Sole Materials Research Articles

Thermoplastic Vulcanizates with an Integration of High Wear-Resistant and Anti-Slip Properties Based on Styrene Ethylene Propylene Styrene Block Copolymer/Styrene Ethylene Butylene Styrene Block Copolymer/Solution-Polymerization Styrene-Butadiene Rubber.

Distinguished from traditional vulcanized rubber, which is not reusable, thermoplastic elastomer (TPV) is a material that possesses both the excellent resilience of traditional vulcanized rubber and the recyclability of thermoplastic, and TPVs have been widely studied in both academia and industry because of their outstanding green properties. In this study, new thermoplastic elastomers based on solution polymerized styrene butadiene rubber (SSBR) and thermoplastic elastomers (SEPSs/SEBSs) were prepared by the first dynamic vulcanization process. The high slip resistance and abrasion resistance of SSBR are utilized to improve the poor slip resistance of SEPSs/SEBSs, which provides a direction for the recycling of shoe sole materials. In this paper, the effects of different ratios of the rubber/plastic phase (R/P) on the mechanical properties, rheological properties, micro-morphology, wear resistance, and anti-slip properties of SSBR/TPE TPVs are investigated. The results show that the SSBR/TPE TPVs have good mechanical properties. The tensile strength, tear strength, hardness, and resilience of the TPVs decrease slightly with an increasing R/P ratio. Still, TPVs have a tensile strength of 18.1 MPa when the ratio of R/P is 40/100, and this reaches the performance of the vulcanized rubber sole materials commonly used in the market. In addition, combined with microscopic morphology analysis (SEM), it was found that, with the increase in the R/P ratio, the size of the rubber particles gradually increased, forming a stronger crosslinking network, but the rheological properties of TPVs gradually decreased; crosslinking network enhancement led to the increase in the size of the rubber particles, and the increase in the size of rubber particles made the material in the abrasion of rubber particles fall easily, thus increasing its abrasion volume. Through dynamic mechanical analysis and anti-slip tests, when the R/P ratio was 40/100, the tan δ of TPVs at 0 °C was 0.35, which represents an ordinary vulcanized rubber sole material in the market. The viscoelasticity of TPVs increased with the increase in the R/P ratio, which improved the anti-slip performance of TPVs. SSBR/TPE TPVs are expected to be used in footwear and automotive fields due to their excellent abrasion resistance and anti-slip performance.

The Land of the Sad Songs: Belarusian National Identity through Polish Documentary films in the 1930s

Belarusian national identity is a taboo subject in Belarus nowadays, unless identity is understood in a Soviet/Lukashenko way. So for Belarusians, who have gone through national destruction more than once, this issue is not just a usual research topic but a crucial question that can contribute to national survival. In the 1920s-30s a part of Belarusian lands belonged to Poland and Polish filmmakers shot some documentaries there, which turned out to be the sole materials since whatever was taken in Soviet Belarus at this time, got burned later. This research aims to determine what these visual materials communicate, how they can add to the Belarusian identity and why it is important for modern Belarus and its cinema.

Effects of triboelectric charging, flooring materials, relative humidity, and shoe sole materials on human walking-induced particle resuspension

Resuspension of settled particles via human activity is one of the primary sources of indoor aerosols. Previous studies have recognized the importance of electrostatic forces on particle resuspension, but the impact has not been well characterized. In this study, we measured the shoe sole electrostatic potential (static charge), airborne particle electrostatic charges, and airborne particle concentration during human stepping under different conditions to assess how these factors affect the resuspension rate of particle size ranging from 0.8 to 8 μm. Six flooring materials (aluminum with and without pattern, carpet, glass, polyvinyl chloride, Teflon, and tile) and three shoe sole materials (EVA, nylon, and rubber) under two relative humidity (RH) levels (normal RH: 60 ± 5% and high RH: 85 ± 5%) were tested. The measured surface static charges of different shoe sole materials before and after human stepping generally agreed with the material's tendency to gain or lose electrons in the triboelectric series. The results also showed that the resuspension rate consistently increased with the increase of particle sizes for all tested scenarios, while it decreased with the increase in RH. Besides, the carpet always gave the highest value for the resuspension rate, while the tile gave the lowest. The data indicated a positive correlation between the charge of resuspended particles and the resuspension rate. In addition, EVA shoe soles generally resulted in higher resuspension rates than shoe soles made of nylon and rubber. This study elucidates the role of electrostatic charge on walking-induced particle resuspension for common materials and helps to assess human exposure to particulate matter.

Electrostatic-spinning construction of HCNTs@Ti3C2T x MXenes hybrid aerogel microspheres for tunable microwave absorption

Abstract Helical carbon nanotubes (HCNTs) are chiral materials that can form an induced magnetic field when current passes through them, making them a desirable material for absorbing microwaves. However, poor electrical properties and inert surfaces limit the application of HCNTs as sole materials. In this study, we develop HCNTs@Ti3C2T x MXenes hybrid aerogel microspheres synthesized using an electrospinning-assisted ice template method. The modified surfaces of the HCNTs form hydrogen bonds with Ti3C2T x MXenes to produce hybrid aerogel microspheres. Because of the different functionalized surfaces of HCNTs (F-HCNTs), F-HCNTs@Ti3C2T x MXenes could be adjusted to obtain effective reflection loss (RL) of microwaves ranging from 2 to 18 GHz. The observed advantageous RL is attributed to the modified surface of the HCNTs, their porous structure, and the optimized impedance matching derived from the synergistic effect between HCNTs and Ti3C2T x MXenes. Successful assembly method for the 3D architectures of HCNTs@Ti3C2T x MXenes hybrid aerogel microspheres significantly widens the practical applications of HCNTs in microwave absorption.

Upcycling of textile and footwear wastes for synergistical reinforcement of cement mortar

The utilization of waste polymeric materials from textile, clothing and footwear (TCF) industry as aggregates in the cement is a valuable approach to reduce plastic pollution. However, the low modulus of polymers and poor interfacial interactions with the cement deteriorate their applications. Herein, we report an upcycling strategy for the recovery of waste fabrics and footwear sole materials from TCF industry as cement mortar reinforcement. The exfoliation of fabrics and pulverization of footwear soles enable them to expose the reactive groups which can absorb Ca2+ dissolved in water, thus helping the formation of C–H–S gel at the organic–inorganic interfacial transition zones between polymers and cement. It was determined by laser confocal Raman spectra. Hence, the exfoliated polyester fibers can prevent the crack expansion of cement and the devulcanized sole elastomers can dissipate energy while subjected to the external force, synergistically enhancing the mechanical properties. The flexural and compressive strengths of cement containing 0.5 wt% PFW and 5 wt% EPW are 48.9% and 59.6% higher than the neat cement. This work suggests a new strategy to realize value-added utilization of waste polymers which are difficult to be classified and separated.

Modification of Footwear PVC Outsoles into Graphene Oxide-Based PVC (PVC/GO) Soling Composites for the Enhancement of Better Physical Properties

Outsole is a crucial component of a shoe’s bottom that directly contacts the ground. Comfort and durability are the most expected characteristics of outsoles. Various nanocomposites are utilized to increase the thermal stability, light weightiness, microporosity, and durability of polymeric materials. In this research, PVC soling composites were prepared using synthesized graphene oxide (GO) from a modified Hummer method. The goal is to improve physical properties like thermal stability or durability, lightweight, tensile strength, and hardness. The GO content in developed soling composites ranged from 0.1% to 0.4% by the colloidal blending method. FTIR, TGA, XRD, and SEM characterized GO and GO/PVC soling composites. The presence of the functional groups C=C, C-O-C, -C=O, and -OH was confirmed by the FTIR spectra of GO, while oxygen-holding functional groups to the layered structure caused the separation of the interlayer space to grow from 0.34 nm to 0.86 nm, according to GO XRD data. XRD results revealed that the GO layers were uniformly distributed in the polymeric matrix of composites. TGA results exhibited that the percentage of mass loss for GO was 81.96% at 800 °C and for soling composites it decreased continuously with an increase in the content of GO, respectively. SEM analysis revealed that the composites with GO showed a homogeneous composite with significantly porous surface morphology. Proportional improvement of tensile strength and hardness for GO-based soling materials were in an increased proportion and density were in a decreased proportion, making the outsole lightweight and durable. Finally, the results suggest that GO/PVC soling composites can improve the durability, mechanical and thermal stability, light weightiness, and microporosity of PVC soles, while the best performance was found for PVC/GO-0.4% soling composites.

Study of the Resistance of Shoe Sole Compositions to various Aggressive Environments

In this paper, the stability of shoe sole compositions to various aggressive media was studied: in water, in gasoline, in diesel fuel, in antifreeze, in industrial oil, in acetone and ethyl acetate. The kinetics of swelling of polymer compositions in various aggressive media for 3 days was determined. It has been determined that the type of filler in the composition has a significant impact on the oil and petrol resistance of the material, therefore, a correctly selected filler will make it possible to significantly improve the ability of sole materials to resist aggressive media. Samples of sole materials were subjected to natural, thermal and light aging. It has been proved that the obtained compositions for casting parts of the bottom of the shoe well withstand tests for natural and artificial aging and can be recommended for use in working conditions with increased thermal and light exposure.

Determination of The Static Friction Coefficient of Some Materials Used for Anti-slip Safety with ANOVA

The surface conditions of ground surface coatings, which are widely used in working environments exposed to various pollutants, were evaluated from a safety perspective. In this work, static and dynamic friction coefficients and safe angle of inclination between some floor coverings exposed to different pollutants for various reasons and some shoe sole materials that are widely used in working environments were determined. The interaction between soil, floor, and surface contaminations were evaluated statistically. In particular, the ground surface contaminated with contaminants such as water and surface cleaners, which significantly reduce the security of the floor is studied. ANOVA results showed that the floor covering, shoe sole samples, and floor contaminants were significant for each variable of the friction coefficient (μ) (p

Cleaner technologies to minimise the environmental footprint of the footwear bonding process

Advances in cleaner technologies have a critical role in reaching Europe’s climate and environmental goals. More precisely, in the case of the footwear bonding process its environmental impact is mainly related to the VOCs emissions resulting from the use of organic solvents in the most common adhesives used, as well as during the application of some surface treatments such as halogenation. Moreover, the use of raw materials of fossil origin also contributes to its carbon footprint. The aim of this work is to deploy cleaner technologies to minimise the environmental footprint of the footwear bonding process through several approaches at different steps of the process life cycle, also to contribute to footwear circularity. This work focuses on the synthesis and application of reactive hot melt polyurethanes from CO2-based polyols as biobased adhesives, and the study of plasma-based surface treatments (low-pressure plasma and atmospheric pressure plasma) to improve adhesion properties, using styrene-butadiene vulcanised (SBR) rubber as a representative footwear soling material. The influence of CO2-based polyols on the polyurethane structure and the physicochemical effects of the plasma treatments on the rubber surface, as well as the final adhesion properties have been evaluated by means of different experimental techniques. The results showed that the values obtained for the T-peel strength of the adhesive joints studied, with the combination of the application of the plasma surface treatments and the biobased reactive hotmelt, exceed the minimum quality requirements for footwear according to the standardised tests. As a result, the deployment of such cleaner technologies regarding adhesives and surface treatments in the footwear bonding process will contribute to improving footwear carbon footprint and its circularity.

Preliminary end-of-service-life study of the soles of protective footwear resistant to selected mechanical factors and mineral oil

This work aimed to study the end of service life of soles of protective footwear resistant to selected mechanical factors and mineral oil. Three sole variants were examined; made from poly(ethylene-co-vinyl acetate) (EVA), poly(vinyl chloride) (PVC) and polyurethane (PU), currently widely used in all-rubber protective footwear. The preliminary study focused on the abrasion resistance and bending strength of the three sole materials after different times of exposure to mineral oil. Changes in density and hardness of the examined materials were evaluated following exposure to cyclical factors. Statistical analysis was performed to identify significant differences between the three types of polymers in terms of abrasion resistance, density and hardness following exposure to mineral oil for three different periods. Surface morphology of the sole materials was examined by means of scanning electron microscopy. The presented studies elucidate the effects of mineral oil on the basic mechanical parameters of all-rubber footwear soles.

Robotised atmospheric plasma treatment to improve the adhesion of vulcanised and thermoplastic rubber materials for a more sustainable footwear

Surface treatment is essential to ensure the resistance and durability of adhesive upper-to-sole joints for footwear. This study investigates robotised atmospheric pressure plasma technology to increase adhesion on styrene-butadiene vulcanised (SBR) and styrene-butadiene-styrene thermoplastic (SBS) rubbers, which constitutes a more sustainable surface treatment as an alternative to solvent-based chemical treatments (i.e., halogenation). In this work, the different parameters such as application speed and distance of the nozzle of the atmospheric plasma system have been optimised and the effects of the plasma treatment on the physicochemical properties in the materials’ surface, roughness, wettability, as well as the adhesion properties have been evaluated by means of different experimental techniques: Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron (FESEM), Contact Angles (CA) and Surface Free Energy (SFE) measurements and T-peel strength tests. The results show that the values obtained for the T-peel strength of the reactive hot melt polyurethane adhesive (HMPUR) joints studied exceed the minimum quality requirements for footwear according to standardised tests. In consequence, the optimisation and validation of operating plasma conditions and adhesion properties of rubbers could consolidate atmospheric plasma as a solvent-free alternative for the preparation of footwear soling materials. The great advantage of this technology is its introduction into the production line by fully automating the bonding process with the use of robots.

TRIBOLOGICAL ASPECTS OF FOOTWEAR SAFETY

The key factor, from the consumer's point of view, during the use of footwear is the safety of use, characterized, among others, by the friction coefficient. A low coefficient of friction can cause skidding, which is very dangerous for the elderly, people with motor apparatus injuries, those with impaired motor skills, and those with a high body BMI index. Fall injuries result in hospitalization, generating high costs of treatment and compensation. The article presents the results of tribological tests of typical footwear sole materials in combination with selected base materials depending on the load on the friction junction, the initial temperature, and the presence of water. The combination of the friction coefficient with the safety of footwear use for typical operating conditions is a new approach to the requirements of ergonomics and increasing comfort while walking.

Differential Raman Spectroscopy Visualization and Rapid Identification of Shoe Sole Materials

Differential Raman Spectroscopy Visualization and Rapid Identification of Shoe Sole Materials

Butter whey and corn steep liquor as sole raw materials to obtain a bioemulsifier from Yarrowia lipolytica for food oil-in-water emulsions

ABSTRACT: A synthetic medium containing glucose, glycerol, yeast extract (YE), and ammonium sulfate (AS) was compared to several low-cost media in their ability to produce high emulsification index (EI). The goal was to reduce the production costs of an emulsifier with application in food oil-in-water emulsions. To this end, agro-industrial by-products were screened for bioemulsifier production from Yarrowia lipolytica. The statistical analysis showed that the EIs of media containing residual frying oil from palm oil (RFO_palm) or soybean oil (RFO_soy), residual liquid from butter production (butter whey, BWhey) or cheese production (cheese whey, CWhey), supplemented with YE and AS were similar to the EI of the synthetic medium. The replacement of YE by corn steep liquor (CSL) also resulted in similar EI, except for RFO_soy. BWhey was tested with CSL without AS and similar EI (66.8%) was detected in comparison to that of the same medium with AS (66.3%). The cell-free broth obtained after Y. lipolytica growth in BWhey+CSL was successfully used to obtain vegetable oil-in-water emulsions indicating its potential application in food products.

Effects of Sole and Combined Physical Filtration Materials on Physicochemical and Microbiological Properties of Waste Waters

Agricultural re-use of waste waters is a feasible alternative for increasing water resources for agriculture. Several methods have been adopted for improving waste water quality for safe re-use in agriculture. However, these methods are complex and difficult to use by local farmers. Hence, a study was conducted to examine the effects of a simple and cost-effective waste water treatment methods on physicochemical and microbial properties of waste waters. The research was conducted in the Department of Crop, Soil and Pest Management, the Federal University of Technology, Akure (FUTA). Waste waters consisted of: fish pond effluent and municipal stream. Materials used for physical filtration of waste waters include: granite, rice husk, charcoal, and pure river sand. Prior to and after treatments, the waste waters were subjected to chemical analysis (pH, electrical conductivity (EC), Nitrate, Cl, P, Ca, and Mg), physical analysis (Total solid, Total dissolved solid and Total suspended solid), and microbiological analysis (Total faecal coliforms, bacteria, yeast and fungi). Results obtained showed that sole and combined applications of physical filtration materials significantly reduced microbial loads in waste waters. Similarly, significant reductions in total solid (TS), total suspended solid (TSS) and total dissolved solid (TDS) were obtained for waters filtered with the filtration materials, both in the single and combined applications. The highest significant pH, EC and chloride were recorded in untreated fishpond effluent (T₁), while fishpond effluent filtered with rice husk (T₅) recorded the highest Significant Ca and Mg. Highest significant Nitrate was recorded in municipal wastewater filtered with rice husk (T₁₁), while highest significant P was obtained at T₅ and T₁₁. Results of this research showed improvement in the quality parameters of waste waters filtered with sole and combined filtration materials.

Analysis of the quality of modern polymer materials of sole

Modern polymer sole materials used in the molding of the sole in the production of shoes are considered. A qualitative analysis of the composition of the compositions used was carried out. The positive and negative characteristics of the resulting products are revealed. In the course of the analysis, a table was created comparing the characteristics of the materials considered for the optimal and effective choice of production material in the shoe industry.

Lightweight, flexible and highly sensitive segregated microcellular nanocomposite piezoresistive sensors for human motion detection

Lightweight, flexible and highly sensitive piezoresistive sensors are promising for future generations of wearable electronics, artificial intelligence, human-computer interaction and soft robotics. Herein, segregated microcellular nanocomposites based on the microcellular poly(ether-block-amide) beads coated with silver (microcellular Pebax@Ag beads) are fabricated by the scalable and feasible supercritical CO2 foaming combined with dip-coating and curing approach. The segregated microcellular nanocomposites show low mass density (0.6 g/cm3), good flexibility (60% compressibility) and high electrical conductivity (0.64 S/m) with ultralow percolation threshold (0.28 vol%) benefiting from the simultaneous incorporation of segregated structures and microcellular structures. The resultant segregated microcellular nanocomposite piezoresistive sensors exhibit superior piezoresistive performances including improved relative resistance changes and higher sensitivity upon the externally applied compression strains owing to the synergistic effect of multiple mechanisms: higher local effective MWCNT contents due to the excluded-volume effect, construction of more effective 3D MWCNT/Ag conductive networks and rapid response due to the highly-resilient microcellular Pebax beads. Furthermore, the segregated microcellular nanocomposite piezoresistive sensors show outstanding long-term durability and working stability upon the repeated compression strains. Practical applications of the segregated microcellular nanocomposite piezoresistive sensors in functional sole materials have been verified for human motion detection during walking, implying their outstanding potential for burgeoning applications such as wearable electronics, artificial intelligence, human-computer interaction and soft robotics.

A mathematical model to investigate heat transfer in footwear during walking and jogging.

Foot temperature during activities of daily living affects the human performance and well-being. Footwear thermal characteristics affect the foot temperature inside the shoe during activities of daily living. The temperate at the sole of the foot (plantar temperature) is influenced by different thermal properties such as heat capacity, heat diffusivity, and thermal conductivity of the shoe sole in addition to its mechanical properties. Hence the purpose of this study was to propose a method to allow investigating the effect of footwear thermal characteristics on the foot temperature during activities of daily living, like walking or jogging. The transient heat transfer between the foot and the ground was studied to drive the governing equation for heat transfer modelling in footwear and to predict foot sole temperature during walking, and jogging. Different thermo-mechanical properties of shoe sole, as well as geometrical parameters, were investigated. The proposed model showed to be able to adequately predict the plantar temperature at the ball of the foot when compared to the results from experimental measurements. Finally, using the proposed method, the thermal behaviour of two different shoes with two different sole materials EVA08 and EVA12 were compared. It was shown that heat capacity as compared to the thermal conductivity of the shoe sole is more effective in reducing the plantar temperature increase in short term. The proposed method proved to be able to accurately predict the thermal behaviour of shoes and can provide a tool to predict footwear thermal comfort.

Characterisation of Shoe Soling Material Prepared by using Rubber and Leather Solid Waste

The ultimate aim of this research is to develop footwear soling materials from solid waste generated from leather industry. The Chrome shaving from the leather sector is used as a solid waste in this study. Styrene butadiene, Nitryl, Ethylene propylene monomer (EPDM) and Isoprene elastomers were used for this research. The rubber and chrome shavings mixes were prepared by using industrial two roll mill. Various propositions of rubbers, chrome shavings and nano fillers were characterised in this research. The developed soling materials were tested for physical testing like hardness, abrasion resistance, tensile strength, density and elongation at break and compared with compared with commercially available soling material. In this research four different experiments has been conducted among the four experiments the soling material prepared using a isoprene rubber-70 Phr and EPDM rubber - 30Phr with chrome shavings -50 Phr and KLN(Silica based) nano fillers- 7 Phr meets the required parameters of commercial soling material. Hence, it is concluded that chrome shaving wastes from tannery in soling material preparation is one of the best remedy for the environmental issues.

Preparation of Low Cost Shoe Soling Material from Leather Waste

Preparation of Low Cost Shoe Soling Material from Leather Waste