This study reports the application of hydrophobic coating on natural leather through plasma polymerization method and the hydrophobic behavior of the substrate . natural leather
Examines plasma coated. The combination of silicon hexane, methyl disiloxane (HMDSO), inert gas argon (Ar) and toluene were used to create surface hydrophobicity on the leather substrate. The results of water contact angle and adsorption time showed that hydrophobicity
The surface of the natural leather sample was clearly improved after the polymerization of HMDSO plasma on the surface of the material. XPS analysis showed that the plasma polymerization of HMDSO toluene compound caused a significant increase in the atomic percentage of Si compound, which is responsible for the property
It is superficial hydrophobicity. These atomic ratios showed that the highest amount of Si and the lowest amount of N, obtained with 100% HMDSO plasma process, confirm the higher degree of plasma angle polymerization than other plasma processes. The decrease observed in
The surface energy of natural leather samples after plasma deposition indicates an improvement in surface hydrophobicity.
Hydrophobic and superhydrophobic surface operations on a variety of substrates for applications such as easy-to-clean textile surfaces have attracted increasing attention in recent years. In general, hydrophobic and superhydrophobic surfaces are produced both by creating a rough structure on the hydrophobic surface, which has a contact angle of more than 90 degrees, and by modifying the rough surface with low-surface free energy materials.
Easy care properties are created on the fabrics of interior appliances (curtains and sofas) and clothing that should prevent dust and stains, by the use of water and oil repellents such as paraffin, polysiloxane and fluorocarbon polymers. Conventional methods, including the use of solvents and organic reagents, mainly wax or wax emulsions, alkene derivatives and hydrophobic resin additives to achieve water repellency, can cause environmental problems due to the disposal of harmful effluents in operating baths. .
In the plasma process, small amounts of reactants are used and due to the short operating times, few materials need to be disposed of, which has environmental benefits. Plasma polymerization of hexamethyl disiloxane (HMDSO) on polyester and cotton blends was studied to achieve superhydrophobic properties.
The formation of a water repellent film on polyester fiber was reported by plasma polymerization using a mixture of argon gas and HMDSO gas phase at atmospheric pressure. Levasseur and colleagues reported the improvement of hydrophobicity on wood surfaces of sugar maple and black spruce using He / HMDSO plasma at atmospheric pressure, controlled by the dielectric barrier. A slight increase in water contact angle was also obtained on natural leather after plasma treatment, which was performed in tetrafluoromethane (CF4) atmosphere.
In the plasma polymerization process, monomers are converted to plasma polymers by the formation of gas phase free radicals, and their recombination at radical sites during film growth results in amorphous, crosslinked, and therefore insoluble, stable structures. It becomes heat, and mechanically hard.
The films produced in this way offer the possibility of creating stainless steel surfaces, scratch-resistant coatings, chemical barrier coatings, and water-repellent coatings.
Hexamethyl disiloxane (3 (HMDSO, (CH3)) 3-Si-O-Si- (CH3), due to the retention of CH3 groups within the Si-O network, is mainly used to achieve hydrophobic surfaces by plasma polymerization.
Wang reported that the improvement of water repellency on cotton fiber surfaces through plasma polymerization, due to the chemical functional groups Si- (CH3) 2, Si-O-Si and Si-C produced from HMDSO fragmentation and reactions Plasma chemistry was between the substrate and the plasma. It was reported that the resulting Si-O-C from the Si-O-Si functional groups broken down by plasma electron collision is then attached to cellulose by chemical bonds of Si-O-Cellulose. In our study, Si-O functional groups, which were also observed after plasma surgery, indicated that the film containing the most primary Si-O functional groups successfully sat on the surface of natural leather.
Although there have been a number of attempts to increase the hydrophobicity of textile-based substrates through plasma treatment, little study has been done on plasma deposition on natural leather. In the present study, the non-corrosive and non-toxic silicone compound hexamethyl disiloxane (HMDSO) was selected as the plasma coating material.
The inert gas argon (Ar) was used as the carrier or carrier for the monomer, and toluene, an aromatic hydrocarbon, was used to reduce the surface polarity due to its non-polar properties. The purpose of this study is to use the plasma process as an ecological complement method to create surface hydrophobicity and easy care properties on natural leather, which has applications in clothing, home appliances and in cars.
All experiments were performed at relative humidity of 65% and 21 ° C.
In this study, hexamethyl disiloxane (HMDSO) obtained from Aldrich Company (98% purity) was used without any purification. The chemical structure of HMDSO, which was coated on a natural leather substrate by the plasma polymerization method, is shown in Figure 1.
Toluene was obtained from Al-drich (purity 8.99%). Argon was used as the carrier gas at a flow rate of 500 cm3 / min and HMDSO was maintained at 25 ° C. The material was bubbled by argon and fed to the plasma tank. The natural leather specimens were wet white goat skins, tanned with aluminum and zirconium-based tanning materials for light interior applications, weighing 400 grams per square meter, and 1 mm thick. The samples were supplied by a natural leather manufacturer.
Figure 1- Chemical structure of hexamethyl nedisiloxane
The outline of the low pressure plasma system used for natural leather surface treatment is shown in Figure 2. The system is a 13.56 MHz radio frequency (RF) source within an L-C matching unit with a maximum power of 100 watts. All samples in this study were processed in plasma power of 20-20 watts. A mixture of HMDSO toluene, bubbled by argon gas, was injected into the reactor tank. The operation was performed at a pressure of 40 Pascals for 10–20 seconds.
The experiments were performed by changing the ratio of HMDSO toluene mixture. Combinations of 100% HMDSO and 1: 3,1: 1 toluene HMDSO were used during plasma polymerization on natural leather samples.
In order to determine the conditions that provide the maximum contact angle of water and therefore the best hydrophobic results, plasma polymerization was performed at different capacities and times of plasma operation. Plasma-free specimens have been cited as practical examples.
Figure 2 – Outline of the plasma system used in low pressure,
To cover natural leather material
Contact angle measurements
Water contact angles and adsorption times on natural leather samples were measured before and after polymerization of HMDSO plasma and HMDSO toluene mixtures using contact angle meters from KSV Instruments. Finland equipped with CAM 200 software.
Water contact angles were measured at different time intervals and changes in water contact angles were observed and compared with the measured angles on the untreated sample. Distilled water droplets with a constant volume of 20 μl were injected on the surface of the sample using a syringe. The system was equipped with a CCD camera and computer-based data processing and acquisition software. Drop photos were taken by the camera at a speed of 1 frame per second.
Stagnant water contact angles were automatically measured by the software using Young-Laplace curve matching based on photographed drop profiles. 5 different contact angle measurements were taken from each sample and the measurements were repeated 5 times for one sample and then the mean values were calculated.
Plasma power was changed from 20 to 100 watts; Plasma operating times of 30, 60, 90 and 120 seconds were used during the experiments. Repeatability of contact angle experiments was performed.
Free surface energy
Changes in surface hydrophobicity of various substrates through plasma deposition were also investigated by measuring surface free energy before and after plasma operation. Surface free energy measurements were performed on the contact angle of the KSV Instruments. The contact angles of distilled water, diidomethane or methylene iodide, ethyl neglycol, and form amide were measured on natural leather substrates. The total surface free energy (Y) for the natural leather sample was calculated by CAM 200 software based on the Oven and Wendt equation, which relates the contact angle (θ) to the solid surface energy (γs) and liquid (γl) and to the surface tension Makes. The principal relation of a linear equation is Y = mX + b, in which m is the slope and the point of intersection b, given by the square root of the free energy component of the solid surface.
Easy to clean
Easy or quick cleaning properties of treated and untreated natural leather stains were tested. Rapid staining test was performed using a standard Taber Industries device. The stained test specimen was fixed to the base of the device and a standard plain white rectangular piece was moistened with distilled water and mounted on the finger of the device with a diameter of 16 mm. The tip of the device was rubbed on the sample at a pressure of 250 g, following a straight path approximately 100 mm long with each arm movement. A total of 20 movements were used during the test to compare stain removal from treated and unprocessed surfaces. The experiments were repeated twice for each type of stain, namely auto ink and mustard. Remaining stain images were taken on treated and unprocessed samples for visual comparison.
Scanning Electron Microscope
The NovaTM NanoSEM system of FEI was used to analyze the surface morphology of unprocessed and polymerized natural leather samples from plasma.
Figure 3 – Absorption of water droplets against time t, not on sample a and samples polymerized with 1: 1 toluene plasma at 80 watts plasma power and 90 seconds plasma operation time.
X-ray photoelectron spectroscopy (XPS)
XPS analysis was performed to identify the chemical composition of the surface of natural leather samples polymerized with plasma. XPS measurements were performed using a high-performance XPS spectrometer from Thermo Scientific. The pressure in the analysis tank was kept at 7-10 Pascals or less during the analysis and the size of the analyzed area was 7.7 mm.
Results and discussion
Different combinations of 100% 3: 1, HMDSO and HMDSO 1: 1 toluene was used during plasma polymerization experiments and the surface hydrophobicity obtained from different plasma compounds was compared.
Water contact angle measurements
Figure 3 shows the wetting behavior of water droplets deposited on unprocessed and polymerized natural leather samples at 80 watts plasma power and 90 s plasma operating time for different combinations of HMD-SO toluene mixture. As can be seen from Figure a3, on the surface of the untreated specimens, the water contact angle was reduced from 105 to zero degrees for 60 seconds.
100% non-polar HMDSO was used for plasma deposition on natural leather substrate and water contact angles were measured to analyze changes in surface hydrophobicity. As can be seen from Figure b3, the contact angle of water decreased from 107 to 105 degrees in 160 seconds, indicating a very small change in the contact angle.
The water droplet remained on the surface and the contact angle of the water after 700 seconds was 90.3 degrees. The contact angle of water began to decrease to less than 90 degrees over time, and at 2800 seconds, the contact angle reached zero degrees, as well as the evaporation of the drop and the contraction of the drop occurred. Compared to the untreated sample, surface hydrophobicity was obtained due to the hydrophobic coating.
Toluene, a non-polar aromatic hydrocarbon, was mixed with HMDSO in a 1: 3 mixing ratio and placed on a natural leather substrate. As can be seen from Figure c3, after the HMDSO-toluene mixture settled in a 1: 3 ratio on the sample surface through plasma polymerization, the contact angle was reduced from 100 to zero degrees in 160 seconds. The water uptake time of 60 s on the untreated sample was increased to 160 s on the treated sample with a 1: 3 HMDSO / toluene mixing ratio. However, due to the lower adsorption time compared to the results obtained for 100% HMDSO, surface hydrophobicity could not be achieved with a 1: 3 toluene HMDSO mixing ratio. Then 1: 1 HMDSO toluene mixing ratio was used for plasma deposition on natural leather substrate. Figure c3 shows the wetting behavior of water droplets placed on a natural leather sample after 1: 1 toluene HMDSO plasma polymerization. The contact angle decreased from 90 to zero degrees in 160 seconds after the drop landed on the surface.
The uptake time of water after plasma placement of the 1: 1 toluene HMDSO mixture was similar to the water uptake time for the 1: 3 toluene HMDSO mixing ratio. The results of water contact angle and adsorption time showed that the surface hydrophobicity of natural leather samples was clearly improved after polymerization of HMDSO plasma on the surface of the material.
This result could be related to the hydrophobic surface formed by silicon compounds with HMDSO plasma treatment.
As can be seen from Figure 4, samples with polymerized plasma showed higher contact angle values over time compared to unprocessed samples. The contact angle values obtained through 1: 3 plasma polymerization and 1: 1 toluene HMDSO were comparable, although for the HMDSO toluene mixing ratio of 1: 3, the initial contact angle was higher at zero. Samples with 100% HMDSO polymerized plasma showed the highest contact angle, approximately 107 ° at zero time, which remained above 90 ° even after 700 seconds.
Figure 4: Time versus contact angle for 100% HMDSO, HMDSO toluene compounds
1: 1 and HMDSO toluene 1: 3 for 80 watt plasma power and 90 seconds operation time.
The contact angle results clearly indicated that the operation improved the hydrophobicity of natural leather. 100% HMDSO plasma polymerization resulted in a hydrophobic film coating for 80 watts of applied plasma power and 90 seconds of operation time. Due to the hydrophobic layer deposited on the natural leather substrate, water droplets over time tend to remain on the treated specimens instead of penetrating the structure. The motion of the water droplets was controlled by the surface properties, which are the irregular surface energy and surface morphology of natural leather. In order to observe the adsorption behavior of water droplets, all 5 samples of unprocessed and plasma coated natural leather were weighed using 100% HMDSO percent, carefully before removing 1 ml of distilled water on each sample.
Water droplets remained on the samples for 15 minutes. Then, the liquid was removed using absorbent paper. The samples were then weighed again. The calculated added weights due to the water absorption of the substrates are presented in Table 1. The weight gain on the plasma-coated natural leather substrate was only about 1% due to the absorption of the droplet, which indicated that the water droplet tended to remain on the surface instead of penetrating into the structure.
Table 1- Weight gain of plasma treated and unoperated samples due to adsorption
Table 2 shows the results of water contact angle and adsorption time on natural leather for untreated sample and plasma polymerized sample using 100% HMDSO with a processing time of 90 seconds, when the plasma power changed from 20 to 100 watts. Gives. The results showed that the increase in plasma power will lead to an increase in surface hydrophobicity based on the time absorption results.
However, when the plasma power increased from 80 to 100 watts, the absorption time decreased to 230 seconds. Contact angles at t = 0 were comparable at different plasma power values. Overall, the highest improved surface hydrophobicity was obtained at 80 watts plasma power; which led to the successful setting of the silicon compound, responsible for creating water repellency, on the natural leather substrate.
Table 3 shows the results of water contact angle and adsorption time on untreated and plasma-treated natural leather at various plasma operating times from 30 to 120 seconds. The sample was coated with 100% HMDSO by plasma plating at 80 watts. The maximum water uptake time was achieved during plasma operation of 90 seconds. The increase in plasma operation time resulted in a slight decrease in water contact angles at t = 0 s. The water uptake time increased with the plasma operation time to about 90 seconds. When the plasma operating time increased from 90 seconds to 120 seconds, the absorption time dropped to 1100 seconds. Overall, the results showed that the most improved surface hydrophobicity was obtained at 80 watts plasma power and 90 seconds operation time. The results of free energy of unprocessed and plasma-treated natural leather surface with 80-watt plasma power and 90-second operation time are shown in Table 4.
Quickly remove stains by washing
Figure 5 shows the stain removal results for unplaced and plasma-treated natural leather samples. Stains were created on the surface using auto ink and mustard, which were allowed to dry for about 12 hours before being removed. After applying 20 motions to the thermometer, the photographs clearly showed that the stains still remained on the untreated specimens, while the specimens were barely visible on the plasma polymerized specimens.
Figure 6 shows scanning electron microscopy images of a natural leather sample before and after plating with HMDSO via plasma. On plasma-coated material, the gaps and holes created by the hair glands were covered by the plasma-coated material, and a thin film was observed on the remaining areas of the background.
Table 3- Water contact angle at t = 0 seconds and adsorption time on untreated and plasma coated samples with 100% HMDSO for 80 watt plasma power
Table 4 – Free energy results of the surface of untreated and plasma-treated samples
X-ray photoelectron spectroscopy (XPS)
The surface chemistry of untreated and plasma coated natural leather samples at 80 watts and 90 seconds plasma operating time was studied by XPS and the results are summarized in Table 5. The main components were unprocessed surface and plasma coated surface, carbon, oxygen, silicon and a small percentage of nitrogen. The peaks of C 1s, O 1s, Si 2p, and N 1s for unprocessed and plasma-coated samples were approximately 285, 532, 102, and 400 electrololes, respectively. For plasma polymerized samples, the locations of Si, O, C, and N peaks did not change significantly compared to the treated sample.
The atomic percentages of silicon, oxygen and carbon components for the surfaces of untreated natural plasma and polymerized with plasma are shown in Table 5. There was 0.57% silicon on the surface of the untreated sample, which may have come from the fabrication process or may be due to the presence of silicon in the XPS assay tank.
Figure 5. Stains of (a) auto ink and (d) mustard stains on untreated samples.
After 20 movements of the odometer; Auto ink stain left on Samples (b) untreated and (c) treated with plasma, residual mustard stain
Unoperated (e) and (f) plasma-treated specimens.
Figure 6. SEM photos of sample (a) unprocessed, (b) coated
Plasma using 100% HMDSO in time
90 second plasma operation and 80 watt plasma power (× 100)
Compared to untreated samples, the atomic percentage of silicon on samples polymerized with HMD-SO plasma, 100% HMDSO / toluene 1: 3 and 1: 1, from 0.57% to 2.23%, 0.98%, respectively and increased by 1.23%. The highest percentage of silicon was transferred to the substrate surface through 100% HMDSO. Atomic oxygen content on 100 HMDSO samples the percentage of plasma polymerized decreased from 13.25% to 12.16% compared to the untreated sample.
Table 5 – Elemental components of plasma coated natural leather samples for different HMDSO toluene compounds
The decrease in atomic oxygen content could be the reason for the improved hydrophobicity obtained on the 100% HMDSO polymerized plasma sample. On samples with plasma polymerized with HMDSO toluene with a mixture ratio of 1: 1 and 1: 3 compared to unprocessed samples, the atomic percentage of oxygen from 13.25 to 20%, respectively Increased by 40 and 17.87%.
No nitrogen was observed on the surface of the sample treated with 100% HMDSO, indicating the deposition of a film of uniform thickness on the surface.
The percentage of nitrogen on the surfaces of the samples after plasma coating with HMDSO toluene 1: 1 and 1: 3, could be a sign that the monomer deposition on the leather surface was not uniform or the thickness of the applied layer was relatively thin. Compared to untreated samples, the atomic percentage of nitrogen on plasma coated samples with HMDSO toluene 1: 1 and 1: 3 decreased from 3.41% to 0.72% and 0.73%, respectively.
The atomic percentage of carbon also decreased with plasma polymerization. As can be seen from Table 5, the C / N atomic ratio for HMDSO toluene compounds with a mixing ratio of 1: 1 and 1: 3, showed that plasma polymerization produces a nitrogen-containing surface that is about 100 HMDSO not found. The O / Si atomic ratio showed that plasma polymerization produced a richer surface than Si due to the increase in silicon compounds with HMDSO plasma treatment.
These atomic ratios showed that the highest SI value and the lowest N value were obtained with 100% HMDSO plasma process, which confirms the higher degree of plasma polymerization than other plasma processes. In addition, the separation of the C1s peak curves for the untreated sample was matched by 3 peaks: one large peak of about 284.54 electrollects due to C = C bonds, the other peak of about 286.232 electroluttes belonging to CN bonds or CO and a small peak at approximately 58.288 eV due to C = O, CN, or C-O bonds.
On the plasma coated sample with 100% HMDSO, the C1s peaks were also matched with 3 peaks: one large peak at 284.41 eV due to C = C bonds, the other peak at about 286.06’s belonging to CO or C = O bonds. And a small peak at approximately 288.65 electron volts due to C = O or CO-H bonds. As can be seen from Table 5, the atomic ratio of nitrogen derived from natural leather on the sample surface decreased to zero% after 100% HMDSO plasma coating.
Separation of Si 2p peak curves can also be done to gain more insight into the chemical bonds present in the samples. Figure 7 shows Si 2p peaks for samples of unworked, plasma-coated natural leather. The unopened Si 2p peak has only one peak of about 102.02 electron volts, which corresponds to Si3N4 units. The Si 2p peak of the plasma-coated natural leather sample also has only one peak of about 85,101 electron volts, which corresponds to SiO or SiO2 units. This result could be due to the formation of a layer of new silicon compounds on the sample surface through plasma coating.
Figure 7. Si 2p peaks for (a) untreated sample and (b) treated sample with plasma using 100% HMDSO.
We proposed surface modification of natural leather substrates through plasma polymerization of different HMDSO toluene blends. Surface hydrophobicity was improved by the introduction of silicon atoms on the surface of natural leather. The formation of a layer of new silicon compounds on the surface through plasma coating increased the contact angle and water absorption time. Significant improvement in the rapid scaling of the stain was observed in the 100% HMDSO plasma polymerized sample compared to the untreated sample. The reduction in free energy levels of the total surface of plasma polymerized leather samples compared to the untreated sample indicated an improvement in surface hydrophobicity.
Placement of HMDSO with plasma at low pressure showed promising results in improving the easy cleaning properties of natural leather. Plasma deposition or coating can be used as a method of environmental (ecological) surface treatment among conventional methods in which solvents and organic reagents are used for surface hydrophobicity.
Collector: Mr. Masoud Hashemi – Today’s textile Magazine
Measuring and shaping the heels of shoes
A special feature of the heel structure of shoes is that they can be made in pairs, because each layer of them must be exactly the same height by the shoemaker in both pairs of shoes. The shoemaker measures each heel separately after making it. If the lifter is too thick in one of them, reduce its size with a hammer and razor so that the other heel size is the same in the other shoelace. After making both heels, the shoemaker then re-measures their height to make sure they are exactly the same.
The next step that requires the most care is to shape the outside of the heels. The shoemaker cuts the heels around with a sharp knife so that when the person wearing the shoe starts walking, the angle of the inside of the ankle is 90 degrees with the ground and the outside of the heel is from the ground to the ground. Be inclined inside.
The shoemakers hammer out the heels of the shoes to make the material compact and hard. The shoemaker also keeps the surfaces of the heels moist with a wet brush and presses the leather edges tightly with the angled side of the hammer head and makes short blows to it.
Each time the shoe attaches another heel to the sole of the shoe, it cuts off the extra parts to match the previous heel. In this photo, only the end part of the soles and the bottom of the rubber band should be added to complete the heel of the shoe.
Wet leather is softer than dry leather, and this is so that if the layers of leather are moistened with water from the beginning, the shoe can be more easily peeled off with a knife. The heel nutrition of the shoes is also curved and should be taken into account when measuring. In addition, the wet outer part of the heel is hammered and compressed.
How to choose ergonomic shoes?
Shoes are the only place where the foot touches the ground while walking, and by choosing a suitable and so-called ergonomic shoe, we can walk more easily and also avoid injuries to the feet (knees and ankles) and especially the back when walking. Avoid prolonged. Legs are our second heart, so wear them properly.
What principles should we follow to choose ergonomic shoes?
When choosing ergonomic shoes, keep in mind the basic rule that your foot should never match the shape of the shoe. Many people think that shoes should have a narrow heel when they are new because they may “open up” as a result of everyday use. This mistake causes many people to choose tight shoes. In most people, one foot is slightly larger than the other, so be sure to always wear shoes the size of your larger foot. Walk around the store with new shoes and make sure it is comfortable.
If necessary, use a tight insole for the smaller foot and make sure that the shoe should be the same size as your foot and do not buy shoes only on the size written on it. When the ergonomic shoe is on your foot, there should be a distance of at least 0.5-1 cm between the longest toe and the toe, otherwise choose a larger size. When walking, shoes should bend with your feet. In fact, the shoes should cover your feet, not restrict them. The characteristics of a good walking shoe are lightness, flexibility of the shoe in the toe and impact.
The upper of the shoe should be a combination of nylon and leather. This part should always be dry and light and well ventilated. The sole of the shoe should provide good protection for the foot and be padded above the heel. The sole of the shoe should also have two basic properties, the first of which should be shock absorbing while walking and the second should be durable.
Shoes should be such that they do not deform too quickly, as well as the nerves, arteries, muscles, and lymphatics of the foot are not under pressure, and the joints can perform their natural movements easily. A normal foot sweats a little during the day, which causes the soles of the shoes to rot. It is very important to wear each shoe regularly every other day so that each shoe has a day or two to dry and breathe.
If you use insoles, remember to take the insoles out of the shoe every day after removing them to allow them to breathe. Most experts and researchers recommend that when choosing shoes, give priority to the appropriate size, lightness, impact and flexibility, and at the same time take into account all of the above. Ignoring any of the above makes the shoe unsanitary and ergonomic.
Of course, in choosing shoes, one should also pay attention to individual differences such as weight, height and type of skeletal shape. For women, the maximum height of the heel is recommended between 2.5 to 3.5 cm, which if not paid attention to this point leads to many discomforts such as back pain, knee pain and recurrent muscle cramps in the leg area. Care in choosing shoes and paying attention to the principles of standard in its production is one of the most essential needs to maintain people’s health. Most people pay attention to the beauty and color and design of shoes, not to their standard. This puts people’s health at risk in the long run. The choice of shoes in the first place should be based on the type of use that is made of it, and a standard shoe is a shoe that has three distinct characteristics: good material, standard heel and standard mold and toe.
Ergonomic shoe uppers
Natural leather, due to the natural pores in its texture, allows the exchange of air between the outside and inside of the shoe and causes the foot to breathe. The air causes bad foot odor and excessive sweating.
Ergonomic shoe soles
There are two types of ergonomic shoe soles on the market: polyurethane (PU) soles and polyvinyl chloride (PVC) soles. PU insoles are lighter, more comfortable, more flexible and more resistant to abrasion, and are more durable. Over time, their friction is slightly reduced and their hardness is lower than that of nitrile rubber. This is why it absorbs pressure shocks. The appearance of these outsoles is solid and they have more flexibility when bending and they enter with the pressure of their fingers. When buying shoes, you should also pay attention to the fact that the sole of the sole should not be flat, but should be treated to prevent slipping.
Ergonomic shoe toe
Paying attention to ergonomic shoe toe standards is also very important in choosing it. In terms of formatting, the toe space of the shoe should be such that it does not put pressure on the toes. Shoes with sharp toes cause the toes to overlap. These shoes put pressure on the toes and deform them. This is more common in women; So that the deviation of the big toe in women is 9 times more than men and the front of the shoe should be such that the toes of the foot are open.
Ergonomic shoe heels
The heel is usually made of leather and rubber so that the upper part is made of leather and the sole is made of soft rubber. Rigid rubber is commonly used for women’s and children’s shoes because they weigh less and do not need to absorb impact like men. It should be noted that the heel with hard rubber increases the durability of the shoe. A wide, low heel increases stability and reduces pressure on the feet, but increasing heel height reduces stability and increases stress on the front of the foot.
Ergonomic shoe trunk
The toe of the ergonomic shoe, which is actually the frame on the shoe and encloses the circumference of the foot, easily resists the pressures and maintains the natural condition of the foot.
Suitable and standard shoes from an ergonomic point of view
The human foot is his second heart. Many ancients believed that certain parts of the soles of the feet represented the health of parts of the body and needed a great deal of care. To choose shoes, you should consider the comfort and health of your feet. Comfortable shoes are shoes that have a suitable height and the foot feels comfortable in the shoe. Normally, the sole of the shoe should not be stiff and transfer the pressure to only one point. Equal distribution of body weight to the front and back of the foot is the best form of shoes. However, high heels cause more weight transfer to the front of the foot and it is recommended not to use it for a long time during the day.
Usually, the narrow toe and high heel of the shoe transfer the weight of the body to the front of the foot and deform the toe and protrude the bone of the foot outwards. Continued use of these shoes causes the bone of the foot to contract and the feet to be pulled in the opposite direction. In fact, these abnormalities will cause excruciating pain and will cause the bone of the foot to deform and this deformation will be irreversible. Hence one will have to wear a custom shoe.
Contrary to popular belief, especially women, who consider sandals and slippers to be the most comfortable shoes, suitable shoes are shoes that completely cover the foot, and it is recommended to buy shoes as much as possible in the afternoon when the foot reaches its maximum volume is done.
Because swelling and increase in leg muscle volume in the afternoon is at its greatest. Although most back and leg pain and discomfort is due to inappropriate shoes, only a very small percentage of shoes are ergonomically standard and usually not suitable in terms of material, model, heel placement and weight distribution, but unfortunately most people they use routine shoes.
Ergonomic sneakers or sports-like shoes are the most comfortable shoes, and also leather shoes are the most suitable material for shoes, because the air transfer between the skin and outside the shoes is established.
But shoes that are made of 100% plastic cause sweat on the feet and prevent air flow and cause skin disorders and abnormalities.
Another point is that shoes should not be worn without socks and socks should be made of cotton because it accelerates air transfer. Also, do not put your foot in the shoes for a long time, even shoes that are very comfortable. Flexing and moving the muscles to relieve foot fatigue causes blood to flow to different parts of the foot, this can be pulled up and held at the ankle. Repeating these movements will reduce the swelling that occurs in the legs.
Here are the factors related to standard ergonomic shoes from an ergonomic perspective:
1) A suitable shoe is a shoe that does not put pressure on the foot when worn for a long time.
2) When wearing shoes, keep in mind that your toes do not change position or the sides of your feet are not under pressure from the shoes.
3) Shoes should not only have a beautiful aspect, but should also prevent damage to your feet in any way from heat, cold, forces from the ground and the unevenness of the ground. In this regard, choosing a shoe with a polyurethane (PU) sole and a natural leather upper is appropriate.
4) Considering diseases such as diabetes may limit your choice, but ultimately with the knowledge of the disease and the conditions that govern you, you will make the right choice.
5) During pregnancy, wear shoes that do not put too much pressure on the foot and back area, such as comfortable and flat shoes that have a soft material and texture. Usually during this period, between half to one score, there will be a change in size, according to which a suitable shoe should be selected.
6) If you suffer from frequent low back pain, try to wear medical shoes because these low back pains are sometimes the consequences of wearing inappropriate and non-standard shoes.
7) If you are overweight, wearing flat and comfortable shoes is recommended. Walking in high heels can upset the balance for those who are overweight.
8) Women who are medium or short in height with medium and fat limbs, it is better to use high-heeled shoes with thick and long heels. Of course, the use of needle-heeled shoes is not suitable for these women.
9) The best shoes for walking are shoes that cover the feet well and act as a protector for the foot when walking, and are also flexible so that the foot does not get tired in it. Walking shoes should be so light that you do not feel like you are wearing shoes at all.
10) If you walk professionally and continuously, it is better to choose shoes with legs that do not damage your legs during long walks.
11) Shoes should match the natural shape of your feet. In addition, the arch of the foot should be in line with the arch of the shoe.
12) Flat shoes should be strong and flexible and have a ribbed surface.
13) Avoid wearing high heels for a long time because high heels cause slipping and falling, back and leg pain and changes in foot shape. The heel of the shoe should not be higher than 4 cm. Wider heels are also more suitable than pointed and narrow heels.
14) When wearing shoes, the heels of your feet should not slip inside the shoes.
15) Wearing narrow toe shoes puts pressure on the toes and deforms them.
16) Flat shoes, stilettos or short heels are both more comfortable and safer.
17) Complications of wearing tight shoes include: calluses, corns, joint pains, pain in the knees and heels, and premature fatigue.
18) Wearing loose shoes leads to blisters on the legs and the person does not have enough balance when walking.
19) Choose a shoe that you can change its size slightly, ie shoes with laces or buckles.
20) The lining and cover inside the shoe should be soft, without seams and any protrusions.
21) You are able to get the size of your shoes according to the formula below. First you need to measure the length of your foot, from the tip of the longest toe (usually the big toe) to the back of the heel: Shoe size = foot length (cm) + 2 cm
22) Due to wearing tight shoes, the foot is under pressure and the nervous system is disrupted, and as a result, the power of thinking and decision-making is reduced to a very low level.
In addition to the standard factors related to the material and construction of the shoes, other factors are equally important when buying shoes.
Here are five tips for buying shoes:
1- The best time to buy shoes is at the end of the day (afternoon), because naturally people’s feet are about half a size smaller in the morning than in the afternoon, and the reason is that your feet get a lot of temperature, pressure and stress during the day. Bear and legs become more swollen and consequently their size becomes larger, so it is a better time in the afternoon to make an informed choice and identify the exact size.
2- In choosing the size of the shoe, two points should be considered, first, in choosing the shoe, it should be worn and relying on the scores written on it is not enough to ensure its size.
Secondly, it should be noted that the size of people’s feet changes with age, weight gain and gain, and even pregnancy, so it is not correct to use the previous sizes in the selection criteria.
3- When buying, it is necessary to wear both soles of shoes, because in most people, the size of one foot is larger than the other, and it is necessary to consider the larger foot as a criterion in choosing shoes.
4- A suitable shoe is a shoe in which the big toe moves easily and there is a distance of about half to one centimeter between the big toe and the front edge of the shoe.
5 – When buying shoes that you plan to wear with socks, it is better to have appropriate socks that are not too thin or too thick.
Ergonomic shoes with heels
Another very important point in choosing shoes is that they have heels, which of course is more common in women. “Flat heel” shoes cause heel pain when walking because they do not hit the heel. So there must be heels, but high heels can cause foot pain in another way.
Women are 10 times more likely than men to complain of foot pain due to wearing very high-heeled shoes with sharp toes that put pressure on the toes. Women are advised not to wear shoes that have a heel higher than 3 cm, because the longer the heel of the shoe, the more pressure is placed on the sole of the foot, which is transferred to the front of the foot and finally to the toes, causing injury Reaching the fingers.
Take care of your second heart!
Complications of wearing non-standard high-heeled shoes include big toe deviation, corns, blisters and toe flexion, chronic back pain, joint and knee and heel pain, and premature fatigue.
As the summer season begins and the weather gets warmer, so-called summer shoes or sandals enter the market. The important thing about wearing sandals is that the foot should remain in a fixed position when moving. In shoes with open backs, when moving, energy is spent not to fall out of the foot, and these shoes cause unnecessary fatigue, and also some delicate women’s sandals have a thin strap on the back. Thin straps, due to their small diameter, put more pressure on one point of the foot and cause it pain. Wearing these shoes in the long run is very painful and annoying, so it is recommended that you do not wear sandals at all if you plan to walk longer than 20 minutes.
Ergonomic children’s shoes
Children’s growing feet need more protection, and adequate support during this period reduces subsequent foot deformities. The feet of children up to the age of 6 are not yet fully formed, so sufficient care will be necessary. For example, wearing narrow toe shoes for growing children has been shown to have a long-term effect on foot deformities until the bone growth plates are completely closed. Shrinkage of muscles and tendons in children can also be a side effect of inappropriate shoes.
In some countries, children with ankle sprains are wearing high-heeled shoes for 2 to 3 days a week to provide good foot care. Research has shown that children who wear narrow-toed shoes are more likely to develop flat feet. The child’s foot should fit snugly inside the shoe and have a longitudinal arch inside the shoe.
Children use their shoes for various activities, especially games and sports, so it is necessary to buy shoes that are suitable for them when walking normally and during play. For this reason, lace-up shoes are not recommended. Wear high-heeled shoes for newborns. These shoes protect the Achilles tendon and prevent toe twisting. Of course, these shoes are not useful for teenagers and older people.
The edges of children’s shoes should not be rigid and also children’s shoes should not be loose and loose in any way. It should be noted that children’s feet tend to sweat more than adults, so it is recommended for children to use sandals in summer.
Guide to buying and maintaining leather boots suitable for snowy and rainy days
Because the boot is worn on snowy and rainy days when the ground is slippery, you should choose a boot that has a dentin sole. Boots with flat soles are not at all useful on snowy and rainy days, and it becomes fashionable to wear a special shape every year.
The ancient Romans and Greeks were the first people in the world to make high boots made of cow and ewe leather, such as boots. They used to sew these shoes in one piece to protect their feet from pebbles and cold while working on snowy and rainy days in autumn and winter, but today it is enough to blow a little cold autumn wind to fill the shop windows with all kinds. And all kinds of short and long boots. Boots with too much variety confuse us to buy.
Fashion is constantly changing, and if you buy boots this year, your boots may go out of fashion next year and another one will become fashionable. Boots are usually available in the form of short, medium and long legs up to the thigh. In winter 2010, high-heeled boots were fashionable, reminiscent of the clothing worn by young women in the 1980s. Long boots are still popular, but it still depends on your taste and the type of clothing you wear, what boots you buy and wear.
For this reason, in the continuation of this article, we will refer to brief points about buying and maintaining boots.
1- Since boots are usually worn with thick woolen socks, it is better to buy them a little bigger than the actual size of your feet so that the toes or toes do not feel uncomfortable in the boots.
2- Formal and party boots are worn with socks or tights, so you do not need to buy these boot larger than the size of the feet.
3- If your legs are fat, you should draw a line around the purchase of long boots and below the knee to wear on the pants, because with them, the fatness of your legs will be too visible.
Wearing short boots is more suitable for shopping, work or university, and long boots are more useful for going to a party.
4 – If your legs are fat and you want to wear a shoe with a short skirt for a winter party in the snow and rain, you should, unlike the previous case, get heeled boots that cover below the knees. The leather or suede of these boots is less visible than socks, which makes the legs appear obese.
5- Boots made of leather or varnish, due to their waterproofness, are suitable options to cover the foot and protect it from the cold, snow and winter rain.
6- Wearing suede boots or snakeskin leathers for a night party will give you a stylish and unique look.
7- Using dark and warm colors for winter boots is more suitable than light and cheerful colors.
8- It is better that the boots you want to buy to wear at work or university do not have more than two centimeters of heel so that you do not put too much pressure on your waist due to wearing them.
9- Wearing short boots is more suitable for going to shopping, work or university, and long boots are more useful for going to a party.
10- Because the boots are worn on snowy and rainy days, when the ground is slippery, you should choose boots that have a dentin sole. Boots with flat soles are not at all useful on snowy and rainy days.
11- By matching the color of the boots with the bag, leather gloves or scarf, you will be very stylish and elegant.
12- The inner material of the boots can be made of fur, wool or even yarn. Of course, those who have skin allergies or eczema, it is better to buy boots that are covered with cotton cloth so as not to aggravate their skin discomfort.
13- If you are very cold, on snowy and rainy days, we suggest you to wear boots with calfskin.
14- To prevent damage to the skin of the legs due to wearing long boots, you must wear socks longer than the boots.
15- In order not to sweat your feet too much inside the boots and not to create a suitable environment for the growth of skin fungi between the toes, it is better to wear cotton socks with boots.
If the inside of the boot gets wet, be sure to expose it to the open air to dry.
This will eliminate the possibility of skin fungus growing inside the boots
16- If you are cold and can not be satisfied with wearing a cotton sock with boots, put at least a cotton sock and then a wool sock on it to reduce the chance of sweating and fungus growth in the space inside the boots.
- On rainy days, if the inside of the boot gets wet, be sure to expose it to the open air to dry. This will eliminate the possibility of skin fungus and infectious agents growing inside the boots.
18- Wash the inside of the boots at least once a month with lukewarm water and mild detergent.
- To prevent leather or varnish boots from cracking, clean and soften them every day with oil waxes.
- If you do not want the boots to bend in the shoelace and crack, pull the zipper of the boots and fill them with cardboard or nylon.
21- You can buy lighter boots for children under 12 so that they do not refuse to wear them under the pretext that the boots are heavy. Lightweight doll boots are better for kids than long, heavy leather boots.
- Zipped boots are better for kids than strappy boots.
Application of X-rays, CT scans and 3D images in the production of shoes
Digital imaging has eliminated the delay in shooting that occurs in X-ray images. This dramatic breakthrough has paved the way for many industries to be more creative with the simultaneous use of X-rays and digital imaging. For example, CT, or CAT, which is mostly used for medical purposes, uses hundreds of two-dimensional X-ray images to create a three-dimensional image of the body’s internal organs.
New tools that use this technology on a small scale (called micro-CT scan) have paved the way for progress in some industries.
Conventional X-ray systems have defects; For example, they provide only a 2D image and are not fast. Micro-CT scan fixes some of these defects and provides even more possibilities.
Micro-CT scans in the field of shoes are also the basis for advances and give the opportunity to control the quality and produce new products with its help.
There are several techniques for scanning and examining plastics and similar materials.
One of these methods is the use of lasers. The SATRA research institute has examined various scanning and imaging techniques that can be effective in the shoe industry.
For example, in the shoe industry, metal detectors are needed to find metals that may have been accidentally left inside the shoe. The process of finding possible metals in shoes may be performed individually or in bulk. However, the location of the metal must be accurately identified. These are issues where the use of micro-CT scans can work.
New X-ray and CT scan technologies
X-ray computerized tomography, sometimes called CT scan, is a non-contact, non-destructive method of obtaining internal and external information about objects that scales the object down to the smallest unit.
This method allows the operator to use X-rays to take hundreds of two-dimensional images of the inside and outside of the object and examine its internal and external features. Then, these two-dimensional photos are converted into three-dimensional photos with the help of software, and it can be cut and viewed from different angles.
Older methods of using X-rays were limited due to the need for more time to produce film and photos. The proliferation of digital imaging has led to an increase in the use of load-bearing devices or CCDs. These tools and other similar technologies help to take high quality photos. They are also widely used in CT scans.
Non-Destructive Testing (NDT)
SATRA tests a wide range of products and goods, many of which are not possible to disassemble and cannot be easily disassembled. For example, some of them are integrated objects or it is very difficult to separate them. Measuring the thickness of the hull, cracks or fractures and defects in plastic and metal materials are some of the things that are difficult to test and measure.
Micro-CT scan in such cases solves a large part of the problem. For example, shoes that have high heels or shock absorbers must be installed and the exact location of these tools must be determined and confirmed. Conventional metal detectors confirm the existence of these instruments, but CT scans and 3D imaging are much more effective in determining their exact location and possible defects.
With this method, not only both metallic and non-metallic materials such as fabric and wood can be examined. In this way, a non-destructive evaluation can be provided without destroying the product. Information that may be obtained with the help of micro-CT scan can be mentioned below:
Three-dimensional image projections created with digital X-ray projections, segmentation information from all three dimensions that can be rotated and reviewed, examining slices or layers, and image transfer from one layer to another.
Software that stores the information and data of scanned images gives the user the option to record the images as desired and show them to another person in the desired way.
In digital imaging, the resolution must be carefully considered. For example, an image of a large area may be of lower quality when magnified, or an image of a small area with a higher resolution will produce a better image.
Utilization of data
An X-ray image can be edited and changed. These images can be made lighter or darker with the histogram to see the details better. The histogram allows light and darkness to be distributed in the image.
Image tonnage analysis of images has a great effect on revealing or hiding high-density or low-density areas and identifying defective areas. It is revealed even if an object or metal is left inside.
Empty or incomplete parts of an object can be easily identified by fading. The user also has the opportunity to focus on one of the shortcomings by zooming and rotating the cuts and to have a better assessment of the situation while examining more closely.
3D CT scanning tools are a valuable investment. Some of these devices have special parts or benefits such as air conditioning and cooling.
Such imaging devices are ideal for situations where an object must be photographed at a certain temperature and humidity. 3D imaging devices require at least one workstation.
A workstation is a computer designed for technical or scientific applications. More working devices can be added to both imaging devices to speed up work and to have enough memory to record information and software and analysis methods such as FEA.
The FEA “finite element method” is a method by which one can predict how a product or commodity will perform under different conditions.
New technology applications
Using X-rays, another level of flexibility, resolution and quality can be added to CT scans and even a fourth dimension can be added. The fourth dimension is time. To add a fourth dimension, images of changes made to the object are recorded at a specified time interval. Of course, this method has some limitations.
If there are several objects to be examined, the location of each of them must be fixed in order to be photographed in its own area. This can be done manually, and after each shot of one part, move the object in its place so that it can be photographed from another part and produce four-dimensional videos.
This special feature paves the way for the use of micro-CT scans in the shoe industry to find interesting and useful applications; For example, it can measure the impact of certain materials or properties that are designed to cool and improve the airflow inside the shoe.
In this example, an air transfer pump is installed, and X-rays are taken of its operation. Then the pressure is measured on the sole of the shoe and the heel.
3D CT scan images can be used in more analytical techniques. These files have the ability to be used in 3D modeling and used in computer aided design or 3D printers.
In fact, these files also help to improve design methods in 3D software. As mentioned, CT scans help a lot in virtual tests and predict performance and structural and mechanical defects.
Product quality evaluation
X-ray image analysis is useful and useful not only in examining the remaining parts inside the shoe but also in examining and confirming the exact production of the product. Recently, research has been done on some shoe insoles, some of which could not be used due to defects in the production method.
In order for the exact type and location of these defects to be visible and eliminated, it was necessary to tear the sole of the shoe. But in this case, the whole final product would be damaged.
However, in the early stages of shoe production, CT scan images could be a great help in solving this problem. As mentioned earlier, the use of CT scan imaging techniques requires the use of new and accurate tools such as histograms. The histogram makes it possible to select or delete different tones of the photo as desired and observe the density of the material inside the shoe.
Of course, some materials are not easily detected by X-rays, and this is where the work becomes difficult. For example, X-rays may not detect the adhesive well because it is transparent and can be detected as part of other materials.
Or at best, it can be detected when the amount is low. Adding some iodine or potassium iodate to the adhesive can solve this problem. Of course, this must be added before applying the glue and then applied to the shoes.
Another way is to use trace chemicals in X-ray images. These materials must also be added to the raw materials before the start of the manufacturing process, and the way it is used must be such that it does not harm the quality and nature of the materials.
There are other ways to take CT scans and larger image samples. For example, in the case of long or long products, spiral scanning can be used. In this method, the sampling or imaging tool rotates 360 degrees around the desired product, and while rotating, the tracker or imaging panel moves upwards to examine all its parts. The goal is to create a spiral path.
The software then converts this spiral image into an image in which all the dimensions of the product are visible. In products that are very large, one of the methods is to scan the different parts separately and then connect these scans. Relevant software can put these images together and determine its dimensions correctly.
Another feature is the use of CT scan images in computer aided design (CAD). In computer design software, the dimensions of the images are specified, and changes can be made on them and the design can be changed or modified.
In general, 3D imaging makes it possible to examine a product from any point of view and from any dimension that is necessary and to observe, measure the various parameters that are needed in different stages of production, and to apply possible changes and corrections in them.
Access to this technology
Access to X-ray CT scanning machines is a significant and valuable investment. Companies that want to buy such equipment, there are different types of them in the market that can meet their different needs according to their budget and cost. This equipment does not require special and complex maintenance conditions.
Such devices, of course, are very heavy and should be taken into account. Steel and lead are an important part of this equipment, and this is due to the safety issues in which such materials are used. The average weight of some of these devices is about 6.5 half tons and they need to have their own location.
Some of these devices may have unique features, such as additional servers or air conditioning. In order for such systems to be used in relation to different goods, the necessary space must be provided for them. This is because in enough space, different goods of different sizes are easily scanned by these devices.
3D imaging technology offers many benefits to manufacturers, distributors, importers and anyone involved in quality control and material analysis.
This tool or technology will be very valuable and useful for reviewing and evaluating the quality and design of any product, because 3D photography makes it possible to identify and accurately fix a defect without slicing a product.
The benefits of micro-CT scan go beyond what is mentioned in this article. The purchase of this equipment may not be in the wealth and financial capacity of all companies, but through rent and contracting services, the ground has been provided for researchers, manufacturers and technicians to access it and carefully examine their product.
Seeing the internal details of a product is a unique opportunity that anyone who thinks of improving the quality of their product can use it. Many people who are active in shoe production and research in this field are becoming more and more interested in using this technology. The use of this technology is expected to grow further in the near future.
Translator: Hormoz Baradaran
Source: world lether/ august-september 2017
Learn more about the types of shoe soles (Features of different types of shoe soles)
In this article, we intend to examine the different materials that are generally used in the production of shoe soles such as leather shoes, rubber, PVC, etc.
Basically, a shoe sole should have the following characteristics:
Beauty: Give the shoes a beautiful shape to be attractive to the buyer of the shoes. The influence and role of shoe shape on the choice of buyers of sports and formal shoes is more evident today.
Impact absorption: In other words, a shoe sole should make the foot feel comfortable.
High abrasion resistance: Replacing the soles of worn and worn leather shoes with elastic indicates the need for soles with high abrasion resistance. For example, a tennis player tends to use a shoe sole that is highly resistant to abrasion.
High flexural strength: Walking and running expose the soles of shoes to bending. Customers expect the soles of their shoes not to be easily damaged during exercise and walking in different temperatures and environments.
High slip resistance: In other words, the amount of friction or coefficient of friction between the materials of different types of soles and different flooring materials should be high to prevent the person from slipping. Special footwear, such as safety shoes, should provide maximum protection for workers’ feet.
Depending on the type and condition of the work environment, the soles of the shoes should be resistant to solvents, oils, petroleum products, hydrolysis, static electricity and abrasion. Antistatic, antibacterial, etc. agents added to the polymer improve its properties.
Materials used in the production of shoe soles:
Rubber: The soles of shoes can be natural or artificial. The characteristics of different types of rubber shoe soles include the following:
- High durability
- Easier and cheaper to produce than leather
Today, most types of rubber shoe soles are synthetic rather than natural rubber soles that used to be made from trees.
Rubber soles are usually a combination of several additives to rubber to control the physical properties of the sole.
Some black compounds may cause blackening of the foam (depending on the type of carbon black used). Shoe soles are used in a variety of products from shoes such as industrial shoes to parliamentary shoes.
Natural rubber or (NR)
Prominent elastic properties and excellent properties of natural rubber allow all types of soles to remain soft and flexible in the cold. Resistance to tearing, puncturing and slipping of natural rubber is higher compared to PVC outsole. Natural rubber is resistant to chemicals such as bases, acids, alcohols and water-based solutions. Because natural rubber is a hydrocarbon, it does not have high resistance to prolonged contact with petroleum and gasoline solvents. NR safety shoe soles are used in food, transportation, facilities, construction and agriculture.
Styrene-butadiene rubber soles: (SBR)
Styrene-butadiene rubber is the most common and cheapest synthetic rubber. It is very weak if you do not add filler. Compared to natural rubber, it has higher abrasion resistance but weaker fatigue resistance.
Nitrile rubber shoe soles: (NBR)
NBR insole or nitrile elastomer is a copolymer of butadiene and acrylonitrile, which is mainly suitable for use in applications where the sole of the shoe requires high resistance to gasoline and petroleum products. NBR cumin has high resistance to minerals and vegetable oils but low resistance to oxygenated solvents such as acetone, methyl ethyl ketone and other ketones.
NBR outsole is highly resistant to acids and bases. Its heat resistance to corrosion compared to natural rubber is an advantage for NBR outsoles.
As the acrylonitrile content in the NBR substrate increases, the resistance to solvents increases but the flexibility decreases at low temperatures. Flexibility at foot temperature NBR outsole is lower than natural foot rubber. Although the performance of NBR low temperature flexibility can be improved by adding compounds, the advantage of NBR outsole lies in its resistance to oil and solvents. In most cases, when it comes to resistance to oil, gasoline and aromatic hydrocarbons, NBR rubber is used instead of natural rubber soles.
Neoprene chloroprene rubber 🙁 CR)
Neoprenees are a large family of synthetic rubbers that have characteristics similar to natural rubbers but have higher resistance to oil, grease, oxidation, and fire resistance than natural rubbers. Although they have lower tensile strength at high temperatures than natural rubber, they have a longer lifespan and do not soften when exposed to heat.
Neoprene rubber, like natural rubber, is used to make soft, high-strength shoe soles in other combinations. The high density of neoprene substrate increases its price and high cost. Neoprene outsole does not have the properties of natural rubber flexibility at low temperatures and limits its use for shock and shock absorption applications. CR substrate is resistant to animal fats, blood, oil, oils, certain acids, alcohols and other solvents.
Thermoplastic elastomer sole: (TPE)
While vulcanized rubbers derive their structural strength from the sulfur crosslinkers that connect the chains at the double bonding sites, the strength of thermoplastic elastomers is derived from crystals that act as the physical crosslinking between the chains. Slowly In the case of thermoplastics (TPU) polyurethane, the crystals are formed by the deposition of a compound (polystyrene) from a polymer network (styrene butadiene). Thermoplastic vulcanization (TPV), which is a double cross-linking process caused by a temperature process, is not discussed here due to its low consumption.
Thermoplastic polyurethane shoe soles:
Polyurethane polyester shoe soles, which are produced by reaction with MDI by mold injection method, have excellent abrasion resistance properties. Thermoplastic polyurethane shoe soles are mostly used in the production of sports shoe soles.
On the other hand, polyester thermoplastic polyurethanes are more resistant to hydrolysis and degradation in contact with water, but their wear resistance is slightly lower.
Cyrillic styrene butadiene styrene 🙁 SBS)
SBS synthetic rubber is made up of a series of styrene butadiene polymers. This rubber is composed of a combination of polystyrene and polyutadiene blocks. The polystyrene phase provides the hardness of the sole, while the polybutadiene phase provides the adhesion and integrity of the sole. The most important descriptive parameter of the SBS shoe sole is the ratio of styrene to butadiene composition.
The share of styrene in the composition is about 29 to 55%, which low amount of styrene to soft grade and high amount of styrene leads to the production of firm cumin.
PVC is the most important material for the production of synthetic shoe soles. PVC polymer is very hard but when used for shoe soles it softens with additives. PVC subsoil is usually produced by direct injection.
Features of PVC underlay include the following:
- Slippery and slippery in cold weather
EVA shoe soles
Ethylene vinyl acetate or EVA sole is one of the most popular materials used in the production of shoe soles due to its cheapness and light weight. The solid co-polymer of vinyl acetate and ethylene expands during the shoe sole production process using a gas as a puffing agent. The resulting closed cell foam gives the shoe sole a high impact absorption property. EVA outsole can be produced by mold injection and extrusion method. Extruded sheets with different hardness and colors can be laminated to the desired thickness with a flame and cut into a specific shape.
Features of EVA outsoles include the following:
- It is much lighter and more durable than micro-cellular rubber soles. It has high flexibility and reversibility.
- Good thermal insulation to protect the feet from the cold.
- Use in midsole for sports shoes
- Use for outdoor soles for lightweight shoes
Polyurethane shoe soles: Polyurethane materials are produced in two parts from a combination of two liquids at high pressure by injection machine and then injection into the shoe sole mold.
The product is open cell foam that is not as cheap and light as EVA substrate.
Due to the open cell of polyurethane outsole, its impact absorption property is not as significant as EVA foam. However, the PU outsole pressure is lower than the EVA outsole so the life of the PU outsole is longer.
PU or polyurethane shoe soles include two types of polyester and polyester, which have been discussed in other articles. Polyurethane materials used in all types of shoe soles have a soft and flexible cell structure.
PUK polymer outsole is very strong and durable and resistant to many chemicals. The production of various types of safety shoe soles with polyurethane materials is very important.
Its features include the following.
- High flexibility, flexibility and high flexibility
- High thermal insulation against cold
- The most durable cumin
Leather outsole: Despite its vulnerability, leather insole is one of the most popular insoles in house shoes.
The cow skin is about half a centimeter thick.
The advantages and disadvantages of leather soles include the following:
Expensive: Leather soles are usually more expensive than rubber and plastic soles.
For this reason, it is mainly used in the production of quality shoes.
- It is less durable than other types of shoe soles:
Leather soles are bought more because of their high attractiveness than for durability, because they are less durable than other shoe soles.
Composite PVC is one of the most widely used and cheapest materials in the production of footwear, sandals and slippers. Subsoil density varies from 0.75 to 1.3 g / cm3 and hardness varies from 45 shore A to 95 shore A 95. When PVC materials are combined with thermoplastic polyurethane (TPU) materials, the substrate is obtained with high abrasion resistance and flexibility. PVC outsole is highly resistant to animal fats, acids, alcohols, gasoline, oil and bases.
PVC outsole is not suitable for working in environments exposed to aldehydes and ketones. The combination of PVC with nitrile rubber powder (NBR) gives the shoe soles a higher resistance to oil and therefore can be used in the molding of shoe soles in the production of safety shoes.
The following features of thermoplastic rubber shoes can be mentioned as follows:
- Feeling comfortable in the foot
- Lighter weight compared to PVC and rubber soles
- High elasticity
- High resistance to cold
- To be cheap
Physical characteristics of shoe soles:
All the materials and compounds mentioned above have unique physical characteristics in the production of various types of shoe soles.
In the following table, we compare the physical characteristics of different types of shoe soles: