Recycling of chrome‐tanned leather waste in acrylonitrile butadiene rubber

Chrome‐tanned leather waste generated in huge amount from leather industry causing environmental problem; this leather waste was used as filler in acrylonitrile butadiene rubber before treatment and after treatment with ammonia solution and sodium formate. Different formulations of acrylonitrile butadiene rubber/leather waste (untreated–treated with ammonia solution—treated with sodium formate) composites are prepared. The formed composites exhibit a considerable improvement in some of their properties such as rheometric characteristics especially with composites loaded with treated leather waste. Tensile strength, modulus at 100% elongation, hardness, and Young's modulus were improved for composite loaded with treated leather. Crosslinking density in toluene was increased by the incorporation of leather wastes treated or untreated resulting in decreases in swelling equilibrium. Distinct increase in the ageing coefficient and the thermal stability for composites loaded with both treated and untreated leather. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhancing particle erosion resistance of glass‐reinforced polymeric composites using carbon nanofiber‐based nanopaper coatings

Sand erosion may cause severe damage of blades in wind turbine and helicopter blades as well as many surface components of airplanes. In this study, thin nanopapers made of carbon nanofibers (CNFs) are used to enhance the resistance of solid particle erosion of glass fiber (GF)/wind epoxy composites. Finite element computer simulations are used to elucidate the underlying mechanisms. The much higher particle erosion resistance of nanopapers compared to GF‐reinforced epoxy composites is attributed to the high strength of CNFs and their nanoscale structure. The excellent performance in particle erosion resistance makes the CNF‐based nanopaper a prospective protective coating material for the turbine blades in the wind energy industry. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Using of leather fibers as an additive in elastomeric compounds: Its effect on curing behavior and physico‐mechanical properties

In this study, leather fibers have been used as an additive in several elastomeric compounds based on nitryl butadiene rubber (NBR), chloroprene rubber (CR), ethylene–propylene–diene monomer (EPDM), and chlorinated isobutylene‐isoprene rubber (CIIR). The effects of employing fibers upon vulcanization characteristics, physico‐mechanical and thermal properties of the compounds were studied. Measuring of vulcanization characteristics of the compounds exhibited that leather fibers has no considerable effect on initial viscosity, processability, and curing time of the compounds but increases cross‐link density. Evaluation of mechanical properties of the vulcanized compounds showed that using leather fibers leads to increase in tensile strength of NBR‐based compound due to compatibility between NBR and leather fibers. Also hardness of all compounds increased drastically by employing leather fibers. The obtained results showed incorporation of leather fibers had no considerable effect on resilience, density, and thermal stability of compounds but enhanced liquid resistance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical and dielectric properties of short‐carbon‐fibers/epoxy‐modified‐organic‐silicone‐resin as heat resistant microwave absorbing coatings

Heat resistant microwave absorbing coatings were prepared by brushing and thereafter heat treatment, using epoxy modified organic silicone resin as binding material, short carbon fibers (C_sf) as absorbers, talcum powder and glass powder as filling materials. The mechanical and dielectric properties of the coatings before and after heat treatment at 600°C for 10 mins were studied. The results showed that the adhesive power after heat treatment enhances remarkably, both the real (ε′) and imaginary (ε″) parts of the permittivity of the coatings increase with increasing C_sf content in the frequency range of 8.2–12.4 GHz. The calculation value of the reflection loss as single layer absorber indicates that epoxy modified organic silicone resin coatings containing short carbon fibers could be a promising radar absorbing material applied at high temperature. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1392‐1398, 2013     

Effects of static axial strain on the tensile properties and failure mechanisms of self-assembled collagen fibers

Collagen fibers form the structural units of connective tissue throughout the body, transmitting force, maintaining shape, and providing a scaffold for cells. Our laboratory has studied collagen self-assembly since the 1970s. In this study, collagen fibers were self-assembled from molecular collagen solutions and then stretched to enhance alignment. Fibers were tested in uniaxial tension to study the mechanical properties and failure mechanisms. Results reported suggest that axial orientation of collagen fibrils can be achieved by stretching uncrosslinked collagen fibers. Stretching by about 30% not only results in decreased diameter and increased tensile strength but also leads to unusual failure mechanisms that inhibit crack propagation across the fiber. It is proposed that stretching serves to generate oriented fibrillar substructure in self-assembled collagen fibers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1429–1440, 1997     

Effects of compaction and UV exposure on performance of acrylate/glass‐fiber composites cured layer by layer

With an aim to reducing manufacturing costs, in general and specifically to provide a solution to the thick laminate curing depth issue for composite materials, UV curing technology was combined with a fiber placement process to fabricate acrylate/glass‐fiber composites. A novel layer‐by‐layer UV in situ curing method was employed in this article and interlaminar shear strength (ILSS) tests and SEM were used to evaluate the effect of processing parameters, including compaction force and UV exposure dose, on ILSS. The SEM images from short‐beam strength test samples and the results of ILSS showed that the fibers' distribution was uniform in the cured matrix resin resulting from the compaction forces and that beneficially influenced the ILSS of the composite greatly. However, the matrix resin produced large shrinkage stresses when it reached a high degree of conversion (DC) in one‐step, which resulted in poor interlaminar adhesion. In addition, the fast curing speed of UV on the composite resulted in poor wetting between fiber and resin, and accordingly resulted in lower ILSS. To overcome these problems and obtain high ILSS value composites, an optimized compaction force and UV exposure dose were determined experimentally. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of quasi‐carbonization processing parameters on the mechanical properties of quasi‐carbon/phenolic composites

In this work, quasi‐carbon fabrics were produced by quasi‐carbonization processes conducted at and below 1200°C. Stabilized polyacrylonitrile (PAN) fabrics and quasi‐carbon fabrics were used as reinforcements of phenolic composites with a 50 wt %/50 wt % ratio of the fabric to the phenolic resin. The effect of the quasi‐carbonization process on the flexural properties, interfacial strength, and dynamic mechanical properties of quasi‐carbon/phenolic composites was investigated in terms of the flexural strength and modulus, interlaminar shear strength, and storage modulus. The results were also compared with those of a stabilized PAN fabric/phenolic composite. The flexural, interlaminar, and dynamic mechanical results were quite consistent with one another. On the basis of all the results, the quasi‐static and dynamic mechanical properties of quasi‐carbon/phenolic composites increased with the applied external tension and heat‐treatment temperature increasing and with the heating rate decreasing for the quasi‐carbonization process. This study shows that control of the processing parameters strongly influences not only the mechanical properties of quasi‐carbon/phenolic composites but also the interlaminar shear strength between the fibers and the matrix resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel Glass Fiber‐Reinforced Composites Having a UV and Peroxy Curable Fluoropolymer Matrix

Novel glass fiber‐reinforced composites were prepared from E‐glass fibers and perfluoropolyether (PFPE), polyurethane acrylate, and methacrylate resins. The PFPE resins were synthesized by a two‐step process and formulated with reactive acrylic diluents obtaining two compositions with different viscosity and fluorine content. These formulations were photocrosslinked by UV‐A radiation and characterized by tensile and dynamic‐mechanical properties as well as by impact resistance. The two UV cured fluoropolymer compositions are high modulus (> 1 GPa), polyphasic materials characterized by a fracture toughness higher than conventional polymer matrices, like epoxies and unsaturated polyesters. Unidirectional laminate composites were also prepared by hand lay‐up and crosslinked both photochemically and thermally. Mechanical characterization of glass fiber‐reinforced composites was carried out by tensile tests and shear adhesion measurements, showing a good fluoropolymer‐glass adhesion strength (ca. 9 MPa). Surface characterization of composites by static contact angle measurements allowed the calculation of the total surface tension γ_s according to Wu's harmonic mean approximation. Surface tension is very low (< 20 mN/m) suggesting a preferential stratification of PFPE segments at the material‐air interface.

     

Role of internal additives in the friction and wear of carbon‐fiber‐reinforced polyimide

Polyimide composites should function in sliding contacts under high temperatures, but the interference of carbon fibers with sliding mechanisms is difficult to predict: they often increase the coefficients of friction and act abrasively but show lubricating properties under other conditions. The friction and wear behavior of thermoplastic polyimides reinforced with short carbon fibers and filled with solid internal lubricant (polytetrafluoroethylene) or silicon oil was investigated in this study with a reciprocating cylinder‐on‐plate tester under 50 N at 0.3 m/s with steel counterfaces that were heated at 23–260°C. We concluded that polytetrafluoroethylene additives effectively reduced the coefficients of friction over the entire temperature range, especially under thermally controlled sliding conditions at 120°C, whereas the internal silicon oil increased the coefficients of friction. The wear rates of the fiber‐reinforced polyimide significantly decreased with respect to those of the thermoplastic polyimide, whereas additional fillers slightly increased the wear rates. We further analyzed the role of internal additives by considering the deformation and maximum polymer surface temperature during sliding. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of sunshine UV irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene fiber

This study investigated sunlight‐simulated ultraviolet (UV) beam irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene (UHMWPE) fibers. The tensile results showed that after 300 h sunlight UV irradiation, the tensile properties of the UHMWPE fibers were obviously degraded. Investigation of morphology revealed that the crystallinity was slightly increased, whereas the overall orientation and molecular weight of the fibers were decreased. SEM observations indicated that the degradation process was nonuniform throughout the fiber and a change from a ductile to a brittle fracture mechanism was found after UV irradiation. DMA results showed two β‐relaxations and one α‐relaxation in the original single filament, and UV irradiation led to the increased intensity of the high‐temperature β‐relaxation and the lowered position of the low‐temperature β‐relaxation. This indicated that irradiation‐induced molecular scission and branching were located primarily in the amorphous and the interface areas of the fiber. Changes in the thermal behavior were also examined by DSC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2757–2763, 2003     

Modification of dry‐spun Suplon polyimide fibers by mixed‐acid oxidation and their effects on the properties of polypropylene‐resin‐based composites

In this study, the effects of mixed‐acid oxidation on the contents of surface elements, morphology, fiber fineness, mechanical properties, mass change rate, chemical structure, and microaggregate structure of dry‐spun Suplon polyimide (PI) fibers were systematically investigated with wet chemical treatment with HNO₃/H₂SO₄. Experiments investigating both the improvement in the O/C ratio of the fiber surface elements and the changes in other performance features were conducted through the functional modification of the fibers. Meanwhile, the causes of specific changes in the mechanical properties of the oxidized PI‐fiber‐reinforced polypropylene‐resin‐based composites were studied and are discussed. The results of this study demonstrate that the treatment of the fibers with HNO₃/H₂SO₄ mixed‐acid oxidation resulted in significant changes in the properties of the fibers; these changes included an uneven surface, increased specific surface area and surface roughness, a locally etched surface, increased surface energy and O/C ratio, an enhanced wettability, an increased fiber fineness, reduced mechanical properties, and a mass gain in the fibers. Although the chemical structures of the fibers treated by oxidized HNO₃/H₂SO₄ were not significantly changed compared to those of the untreated fibers, the microscopic aggregation of the treated fibers changed to some degree, and the ratio of the amorphous regions significantly increased. Taken together, the functional modification of the PI fiber surface was achieved efficiently through the use of a suitable HNO₃/H₂SO₄ oxidation process and with other performance features of the fibers taken into account. This was favorable for the enhancement of the interfacial properties of the polypropylene fibers and the matrix resins, and thus, the modification improved the mechanical properties of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44932.     

Effects of the addition of LiCl and CsCl salts on the mechanical properties and morphology of poly(styrene‐co‐methacrylate) ionomers

The effects of the addition of LiCl and CsCl salts to Li‐ and Cs‐neutralized styrene‐co‐methacrylate ionomers, respectively, on the mechanical properties and morphology of the ionomers were studied. It was observed that with increasing inorganic salt contents, the ionic modulus increased, and this indicated that the inorganic salts in the ionomers acted as fillers. However, the type of salt did not affect the increase in the ionic modulus. It was also found that the addition of the inorganic salts did not change the matrix glass‐transition temperatures of the ionomers strongly but reduced the cluster glass‐transition temperature significantly and slowly for the LiCl‐ and CsCl‐containing ionomers, respectively. In addition, with increasing salt contents, a small‐angle X‐ray scattering peak shifted to slightly lower angles. These findings suggested that some of the inorganic salts resided in the multiplet with the ionic groups of the ionomers, acting as plasticizers. The presence of an X‐ray diffraction peak for the polymers containing a relatively large amount of CsCl indicated that the CsCl salt formed phase‐separated domains at sufficiently high salt contents. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of an epoxy‐based bonding agent on the cure characteristics and mechanical properties of short‐nylon‐fiber‐reinforced acrylonitrile–butadiene rubber composites

The cure characteristics and mechanical properties of short‐nylon‐fiber‐reinforced acrylonitrile–butadiene rubber composites with and without an epoxy resin as a bonding agent were studied. The epoxy resin was a good interfacial‐bonding agent for this composite system. The minimum torque showed a marginal increase with the resin concentration. The maximum–minimum torque showed only a marginal change with the resin. The scorch time decreased with the fiber concentration and resin content. The tensile strength and abrasion resistance were improved and the tear resistance and resilience were reduced with the resin concentration. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 532–539, 2006     

Modification of leather properties by grafting. I. Effect of monomer chain on the physico‐mechanical properties of grafted leather

Although leather has a number of desirable properties such as thermal stability and fire retardancey, in addition to high toughness, it has a few drawbacks such as weight, high water absorption, poor soil and rot resistance, and nonuniformity. If these defects are overcome, leather's usefulness would be further enhanced and its competitive position with respect to synthetics would increase. This study reports the physical and mechanical properties of buffalo leather after chemical graft copolymerization with ethyl acrylate, butyl acrylate, and 2‐ethyl hexyl acrylate using benzoyl peroxide as an initiator. The optimum conditions for grafting (e.g., monomer and initiator concentrations, temperature and time of grafting, and solvent leather ratio) were extensively investigated. The study achieved outstanding properties for buffalo leather in reduction of water uptake after grafting, especially on using 2‐ethyl hexyl acrylate and butyl acrylate monomers. FT‐IR and solid ¹³C‐NMR for leather before and after grafting confirmed the grafting process.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1478–1483, 2003     

Effect of heat treatment on the structure and properties of Lyocell fibers

Lyocell fibers were heat‐treated under different conditions. The tensile strength and initial modulus of the heat‐treated Lyocell fibers increased sharply, whereas the elongation at break decreased. Moreover, applying tension to the fibers during the heat treatment further improved the tensile strength and initial modulus. In addition, the crystallinity of the heat‐treated fibers increased slightly, and there was no obvious change with an increase in the tension; the general orientation of the heat‐treated fibers increased, the crystalline orientation little changed, and the amorphous orientation improved. Also, the improved mechanical properties of the Lyocell fibers via the heat treatment could not be preserved for long. The reason may be that the crystalline structure of the Lyocell fibers was not destroyed and no new crystallites were formed during the heat‐treatment process. Therefore, the heat‐treated Lyocell fibers reverted to their original state with time because there was no crosslinking point to fix the orientation, although the cellulose molecules of the amorphous region of the Lyocell fibers were more oriented by the heat treatment with tension. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1738–1743, 2006     

Kenaf‐bast‐fiber‐filled biodegradable poly(butylene succinate) composites: Effects of fiber loading,fiber length,and maleated poly(butylene succinate) on the flexural and impact properties

Poly(butylene succinate) (PBS) filled kenaf bast fiber (KBF) composites were fabricated via compression molding. The effects of KBF loading on the flexural and impact properties of the composites were investigated for fiber loadings of 10–40 wt %. The optimum flexural strength of the composites was achieved at 30 wt % fiber loading. However, the flexural modulus of the composites kept increasing with increasing fiber loading. Increasing the fiber loading led to a drop in the impact strength of about 57.5–73.6%; this was due to the stiff nature of the KBF. The effect of the fiber length (5, 10, 15, and 20 mm) on the flexural and impact properties was investigated for the 30 wt % KBF loaded composites. The composites with 10‐mm KBF showed the highest flexural and impact properties in comparison to the others. The inferior flexural and impact strength of the composites with 15‐ and 20‐mm KBF could be attributed to the relatively longer fibers that underwent fiber attrition during compounding, which consequently led to the deterioration of the fiber. This was proven by analyses of the fiber length, diameter, and aspect ratio. The addition of maleated PBS as a compatibilizer resulted in the enhancement of the composite's flexural and impact properties due to the formation of better fiber–matrix interfacial adhesion. This was proven by scanning electron microscopy observations of the composites' fracture surfaces. The removal of unreacted maleic anhydride and dicumyl peroxide residuals from the compatibilizers led to better fiber–matrix interfacial adhesion and a slightly enhanced composite strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of the cross‐sectional shape on the structure and properties of polyester fibers

The effects of the fiber cross‐sectional shape on the structure and properties of polyester fibers were investigated. Fully drawn yarn (FDY) polyester fibers (167 dtex and 48 filaments) were produced under the same spinning conditions used in a spinning plant. The only difference between the fibers was their cross‐sectional shapes. Four different cross‐sectional shapes were chosen for the experimental work: round, hollow‐round, trilobal, and hollow‐trilobal. The crystallinity and values of the maximum stress, maximum strain, modulus, yield stress, shrinkage in boiling water, and unevenness of the fibers were determined. The difference in the cross‐sectional shapes influenced the modulus, maximum strain, yield stress, and shrinkage in boiling water. No effects on the crystallinity and maximum stress were observed. The results suggested that the hollow fibers had higher amorphous orientation than the full fibers. The hollow‐round fiber had the highest unevenness value. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2615–2621, 2007     

Effects of superfine silk protein powders on mechanical properties of wet‐spun polyurethane fibers

Mechanical measurements were employed to investigate the effects of three types of superfine silk protein powder on tensile strength, elongation, and elasticity of wet‐spun Pellethane^® 2363‐80AE polyurethane (PU) fiber. These superfine silk protein powders included undegummed silk (with both native silk fibroin and sericin, water insoluble), native silk fibroin (with native silk fibroin only, water insoluble), and regenerated silk fibroin (with regenerated silk fibroin only, water soluble) in powder form. Experimental data derived from the mechanical measurements illustrated that the miscibility between the PU and regenerated silk fibroin were superior to that between PU and the other two silk proteins. This may be attributed to the similar chemical structure and microphase separation of PU and regenerated silk fibroin with lower molecular weight than native silk fibroin. This preliminary work may provide some information for biomimetic processing of silk‐inspired PU biofibers, which combine elasticity of synthetic PU with biofunction of natural silk fibroin for special biomedical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Comparison of the structures and properties of Lyocell fibers from high hemicellulose pulp and high α‐cellulose pulp

Lyocell fibers were produced from a cheap pulp with a high hemicellulose content and from a conventional pulp with a high α‐cellulose content. The mechanical properties, supermolecular structure, fibrillation resistance, and dyeing properties as well as the fibril aggregation size of the high hemicellulose Lyocell fiber and high α‐cellulose Lyocell fiber were compared. The results showed that the high hemicellulose spinning solution could be processed at a higher concentration, which improved the mechanical properties and the efficiency of the fiber process. Compared with the high α‐cellulose Lyocell fiber, the high hemicellulose Lyocell fiber had better fibrillation resistance and dyeing properties. Therefore, it is feasible that this cheap pulp with a high hemicellulose content can be used as a raw material for producing Lyocell fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Regulation of the mechanical properties and heat resistance of the poly(l‐lactide‐co‐trimethylene carbonate) copolymer by the incorporation of a stereocomplex crystal and graphene oxide

Stereocomplex crystals of polylactide and graphene oxide (GO) were simultaneously used to regulate the mechanical properties and heat resistance of a poly(l ‐lactide‐co‐trimethylene carbonate) [P(LLA‐co‐TMC)] copolymer. The crystallization behaviors in the nonisothermal cold‐crystallization process of P(LLA‐co‐TMC)–poly(d ‐lactide) (PDLA) blends and P(LLA‐co‐TMC)–PDLA–GO composites were investigated by differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized optical microscopy. Data from the crystallization kinetics and the crystallization active energy indicated that GO both promoted nucleation and limited growth during the stereocomplex crystallization process. Three kind of samples (without crystallization, with low crystallinity, and with high crystallinity) were used to investigate the mechanical properties and heat resistance. We found a decrease in the elongation at break when the stereocomplex crystal and GO contents were increased, and this was accompanied by an improvement in the tensile strength. The change in the storage modulus value determined by dynamic mechanical analysis demonstrated that both the stereocomplex crystal and GO effectively improved the heat resistance. These results indicate that this study provided a new strategy for fabricating a P(LLA‐co‐TMC) copolymer with good comprehensive properties at was entirely different from common chemical crosslinking methods. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45248.