Modulating Chromium Containing Leather Wastes into Improved Composite Sheets Using Polydimethylsiloxane

The disposal of huge quantities of leather wastes in open environment produces several toxic contaminants. An alternative to disposal of these wastes is to reuse them. In the present work, we have proposed a method to utilize collagen and chrome shaving wastes (CCS) to prepare composite sheets employing polyvinylpyrrolidone (PVP). The formed CCS/PVP composite sheets were characterized for their thermal, mechanical and morphological properties. It has been found that the mechanical properties of the composite sheets increase as the concentration of PVP increases from 2.5 to 10 wt%. Scanning electron microscopic studies reveal that the incorporation of PVP in the composite sheets resulted in increased interfacial adhesion thereby leading to reduced debonding between fibers. Fourier-transform infrared analysis of the composite sheets revealed the presence of dominant peaks associated with both collagen as well as PVP. It has also been demonstrated that the thermal stability of the formed composite sheets increases significantly as the concentration of PVP increases. These results demonstrate the homogeneity of the developed composite sheets. The obtained results suggest that the PVP incorporated composite sheets were found to have improved characteristics and hence suitable for numerous applications in footwear, clothing and related industries.

The rising concern towards environmental issues and non‐recyclable solid wastes preservation needs has led to the development of high‐performance biodegradable composite materials with new functionalities. In this regard, the current study focused on fabricating flexible and biodegradable composite sheets by utilizing waste buffing dust (BD) and sugarcane fiber (SF). Flexible composite sheets were fabricated using simple solution casting method with different mixing ratios of BD and SF. Wide range of characterizations like ultraviolet‐vis spectroscopy, Fourier‐transform infrared spectroscopy, thermogravimetric analysis, tensile tests, x‐ray diffractometry, scanning electron microscopy, oxygen gas transmittance rate, and soil burial tests were conducted to comprehensively evaluate their performance. The obtained results were highly promising which reveals strong bonding between BD and SF along with a uniform surface quality. Particularly, the enhancement in various key characteristics was observed for composite sheets compared to pure BD sheets. The composite sheets with the optimal content of natural rubber latex demonstrated a significant increase in tensile strength, elongation, hardness, and density by 61%, 42%, 37%, and 44%, respectively. Additionally, the composite sheet has witnessed significant improvements with an increase by 36% in gas barrier property and an enhancement of 39% in biodegradability. These findings highlight the potential of these composite sheets as a versatile material suitable for a wide range of applications which includes packaging, interior furnishing industries, and reinforcing elements in the footwear industry. Numerous advantages like simplicity, cost‐effectiveness, and flexibility of these composite sheets offer an environmentally friendly alternative that is capable of reducing waste and promoting sustainable practices.Highlights Fabricated composite sheets from waste BD and SF. Strong bonding and uniform surface quality observed. Improved thermal stability, gas barrier, and biodegradability. Enhancements in tensile strength, elongation, hardness, and density. Versatile eco‐friendly material for packaging and furnishings.

The relationships between the properties and microstructures of two series of perfectly alternating bisphenol A-polycarbonate-polydimethylsiloxane block copolymers were studied. In the first series, the polycarbonate (PC) block length was kept constant while the block length of polydimethylsiloxane (PDMS) was varied. The tensile properties of these block copolymers were found to be a function of composition. Dynamic mechanical properties measured as a function of temperature revealed the two-phase nature of these materials. Transmission electron micrographs showed that all samples had a sponge-like morphology independent of composition. The rheological maximum viscosity for the sample containing PC and PDMS blocks of equal molecular weight and extrudate swells increased with PC content. Takayamagi's mechanical coupling model was used to predict the maximum loss tangent at the glass transition temperature of PDMS using the known properties of pure components. The predictions agreed fairly well with the experimental results. In a second series of block copolymers, the block molecular weights of both PC and PDMS were varied to keep the composition constant. The tensile strength of these samples was found to increase with block molecular weights, except for the sample having the highest block molecular weights. The lower tensile strength of this material was attributed to its lamellar type morphology. Cold crystallization of PDMS blocks was found for samples having high PDMS block molecular weight (greater than 8000 g/mole). The Tg of PC blocks followed the Fox-Flory equation with a higher K value than expected. The PDMS content in PC domains was calculated to range from 11% for material of low block molecular weights to about 1.3% for high block molecular weight material.

A material-guided, regenerative approach to heal cranial defects requires a scaffold that cannot only achieve conformal fit into irregular geometries but also has bioactivity and suitable resorption rates. We have previously reported "self-fitting" shape-memory polymer (SMP) scaffolds based on poly(ε-caprolactone) diacrylate (PCL-DA) that shape recover to fill irregular defect geometries. However, PCL-DA scaffolds lack innate bioactivity and degrade very slowly. Polydimethylsiloxane (PDMS) has been shown to impart innate bioactivity and modify degradation rates when combined with organic cross-linked networks. Thus, this work reports the introduction of PDMS segments to form PCL/PDMS SMP scaffolds. These were prepared as co-matrices with three types of macromers to systematically alter PDMS content and cross-link density. Specifically, PCL90-DA was combined with linear-PDMS66-dimethacrylate (DMA) or 4-armed star-PDMS66-tetramethacrylate (TMA) macromers at 90:10, 75:25, and 60:40 wt % ratios. Additionally, a triblock macromer (AcO-PCL45-b-PDMS66-b-PCL45-OAc), having a 65:35 wt % ratio PCL/PDMS, was used. Scaffolds exhibited pore interconnectivity and uniform pore sizes and further maintained excellent shape-memory behavior. Degradation rates increased with PDMS content and reduced cross-link density, with phase separation contributing to this effect. Irrespective of PDMS content, all PCL/PDMS scaffolds exhibited the formation of carbonated hydroxyapatite (HAp) following exposure to simulated body fluid (SBF). While inclusion of PDMS expectedly reduced scaffold modulus and strength, mineralization increased these properties and, in some cases, to values exceeding or similar to the PCL-DA, which did not mineralize.

Conversion of finished leather waste incorporated with plant fibers into value added consumer products – An effort to minimize solid waste in Ethiopia

ABSTRACTNylon-6-b-polydimethylsiloxane copolymer was synthesized with macroinitiator through in situ polymerization. The macroinitiator with two chain-growing centers per molecule is based on hydroxyl terminated polydimethylsiloxane (PDMS) functionalized with diisocyanate. The influence of PDMS contents on the properties of copolymers was studied. Differential scanning calorimetry and X-ray diffraction were used to investigate the melting temperature, crystallization temperature and crystal form of samples, and the results showed that the crystallinity of polymers decreased. The mechanical properties of samples were studied by notched-impact testing and tension test. The notched impact strength was improved by 200% with PDMS concentration up to 4 wt%. The form of scaly was seen by scanning electron microscope proved the improvements of the impact strength of the copolymer. The water contact angles test showed that the surface tension of copolymers decreased with the PDMS content increasing and the surface of copolymer changed from hydrophilic to hydrophobic.

Recycled materials are currently receiving significant attention from society. In particular, a large amount of waste is generated during the production process in the textile and footwear industries. New products have been developed by combining textile and footwear waste with plastic or rubber. In the study, the authors used fiber (fabric waste torn into fibers), leather waste, and natural rubber to successfully manufacture outsole materials by combining these three primary materials with additional additives and chemicals. After production, the properties of the product were tested. This article presents the results of a survey on the tensile strength, tear strength, hardness, water resistance, dimensional stability, abrasion resistance, and compression performance of the shoe outsole materials produced by Vietnamese Standards. Based on this research, we aim to develop shoe outsole materials that are in line with the principles of the circular economy of the textile and footwear industry and establish a domestic secondary raw material source for footwear manufacturing companies in Vietnam.

Waterborne polysiloxane–urethane–ureas (WBPSUU) were prepared through a prepolymer process using siloxane polyol, namely polydimethylsiloxane (PDMS) and polyether polyol, namely poly(tetramethyleneoxide glycol) (PTMG) as the soft segments. The goal of this study was to explore the potential use of polysiloxane–urethane–urea in marine coatings in order to boost the flexibility, adhesion, erosion, and foul-release property with respect to PDMS/PTMG ratio (PDMS wt%). The structural elucidation of the synthesized waterborne polyurethane and WBPSUU was carried out by FTIR, 1H NMR, and 29Si NMR spectroscopic techniques. The XPS and AFM analyses indicate that the polymer surface can be silicone enriched with the optimum PDMS content (15.76 wt%). The antifouling property of the coatings was investigated by the immersion test under a marine environment for 90 days. The fouled area was calculated for all the samples and the fouled area (%) decreased with increasing PDMS content. After 90 days the lowest fouled area (5%) was observed in the sample using WBPSUU4 (PDMS 15.76 wt%) among all of the samples.

Much attention has been focused on the development of a new type of bioactive material with mechanical properties analogous to those of natural bone. The present authors previously showed that some polydimethylsiloxane (PDMS)-modified CaO–SiO2–TiO2 hybrids prepared by sol-gel method show apatite-forming ability in a simulated body fluid (SBF), which is indicative of bioactivity. In the present study, effects of composition of PDMS-modified CaO–SiO2–TiO2 hybrids on their bioactivity and mechanical properties were investigated. The bioactivity of the hybrids increased with decreasing PDMS content and increasing TiO2 content. Their strain at failure increased with increasing PDMS content and decreasing TiO2 content. Some samples showed high bioactivity, as well as analogous mechanical properties to those of human cancellous bones. This type of hybrids might be useful as a bone-repairing material.

Flexible and leakage-proof phase change composite for microwave attenuation and thermal management

To treat coal gasification wastewater containing phenol, polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) hollow fiber composite membrane was made by dynamic negative pressure coating method, using PVDF hollow fiber membrane as base membrane, PDMS as modifying membrane material, to improve pervaporation performance of PDMS by the cross-linking modification. The influence of cross-linking agent, PDMS concentration, coating time on pervaporation performance of the composite membrane was investigated. Actual coal chemical wastewater with phenol concentration 1600-1800 mg/L, COD 13000-15000 mg/L was treated by the obtained PDMS/PVDF composite membrane, and at temperature 70℃, the flow rate of 10 L/h, pressure under membrane 3KPa, phenol flux 16.81 g/(m2·h), separation factor reaches 8.103.

New polydimethylsiloxane (PDMS)‐polyimide block copolymers were synthesized by the solution polycondensation of aminopropyl‐terminated polydimethylsiloxane, 1,1‐bis(4‐aminophenyl)‐2,2‐diphenylethylene, and 3,3′,4,4′‐benzophenonetetracarboxylic dithioanhydride in pyridine. New 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane (BADS)‐based random copolyimides were also prepared. The inherent viscosities of all the random and block copolyimides were in the range of 0.13–0.90 dL/g in N‐methyl‐2‐pyrrolidone. These copolymers were soluble in N,N‐dimethylacetamide, N‐methyl‐2‐pyrrolidone, and m‐cresol. All the BADS‐based random copolymers and PDMS‐containing copolymers with PDMS content above 42 wt % were soluble in tetrahydrofuran and chloroform. Transparent or somewhat cpaque films were prepared by casting from the reaction solutions. The BADS‐based random copolyimides had one glass transition temperature (Tg) in the whole composition ranges, which showed single phase nature of the copolymers. On the other hand, the PDMS‐polyimide block copolymers had double TgS, indicating phase‐separated morphology. The block copolymers containing PDMS content above 73 wt % behaved like a high temperature elastomer. © 1993 John Wiley & Sons, Inc.

This study investigated the effect of adding polydimethylsiloxane (PDMS) on the processing, surface and mechanical properties of linear low-density polyethylene (rLLDPE) recyclate generated as post-production waste in the rotational molding process. Polymer blends containing 0.1, 0.2, 0.4, 1.0 and 2.0 wt.% of polydimethylsiloxane were produced during twin-screw extrusion, followed by cold granulation. The addition of the modifier at the adopted concentration range lowered the water absorption of the recyclate and contributed to a slight increase in processing shrinkage; however, it did not significantly affect its processability (MFR~const). The modification carried out increased the hydrophobic character of the recyclate surface (the wetting angle for water was enhanced) and decreased the value of the dynamic friction coefficient. It also contributed to an improvement in surface gloss. The deterioration of point hardness and scratch hardness of the recyclate was noted with an increase in the PDMS content in the mixture. The addition of polydimethylsiloxane caused changes in the nature of resulting cracks (increased width and reduced longitudinal deformation), which led to surface smoothing and increased the sliding effects. There was no negative effect of PDMS addition on the mechanical properties (static tensile) of the recyclate. The impact strength of rLLDPE deteriorated slightly. The research conducted shows the high application potential of PDMS as a modifier of the surface properties of low-density polyethylene linear recyclate and of selected processing properties, which can contribute to the shortening of the production cycle, thus potentially increasing its attractiveness compared to the original raw materials.

Cells are continuously exposed to mechanical forces in physiological and pathological situations, including a variety of tensile and compressive stresses. There is very active research exploring how cells and tissues respond and adapt to such stresses and how these responses integrate with mechanochemical signaling. This has generated a need for sophisticated tools compatible with standard cell culture protocols and microscopy methods, reproducing physiological stresses in in-vitro studies. This study presents the design, function, and characterization of a stretching device compatible with high-resolution optical and fluorescence microscopy. Numerous stretching devices, either pneumatic- or motor-based, have been developed and used in the field. We present one of these systems in detail, including design guidelines, a variety of applications, and all the tools to fabricate a similar setup. The system is based on a deformable polydimethylsiloxane (PDMS) membrane, stretched equibiaxially upon vacuum application, rendering a homogeneous, reproducible, and controlled sample strain. It provides a variety of tensile stresses, from punctual and immediate stretch to repeated stretch-release cycles of controlled amplitude and frequency. Substrate coating with adhesion proteins allows seeding cells bearing fluorescent reporters in the stretching device and performing live-imaging of these cells upon stretch using high magnification fluorescence microscopes. Compressive stresses can also be applied by letting the sample adapt to stretch and subsequently releasing it or by seeding the sample on a pre-stretched substrate before stretch release. Additional topographical patterning of the PDMS substrate enables imaging of the same sample in different microscopy modes (such as fluorescence and electron microscopy). Polyacrylamide gels can also be attached to the PDMS membrane, resulting in the stretching of cells seeded on substrates of different stiffnesses. Overall, by applying controlled tensile stresses on live samples, this stretching device, coupled with high-quality fluorescence microscopy, can address a large variety of questions in mechanobiology.

Hydrophobicity and bioaccumulation potential of linear and cyclic polydimethylsiloxane (PDMS) oligomers were estimated by reversed‐phase liquid chromatography and feeding experiments with guppies (Poecilia reticulata). PDMS concentrations in fish were determined by capillary column gas chromatography and gas chromatography‐mass spectrometry. In contrast to polychlorinated biphenyls (PCBs), only very small amounts of PDMS were retained by the fish after six weeks feeding.