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     

Enhanced interfacial adhesion of aramid fiber reinforced rubber composites through bio-inspired surface modification and aramid nanofiber coating

In order to improve the interfacial adhesion between aramid fiber (AF) and rubber matrix, a simple and facile method of aramid nanofiber (ANF) coating is demonstrated in this article. Tannic acid (TA) and polyethyleneimine (PEI) are polymerized in an alkaline solution to form a thin TA/PEI (TP) layer that is deposited on the surface of AF to introduce functional groups such as hydroxyl and amino groups. Then, the ANF coating is utilized to construct nanostructures on the surface of AF to improve the interfacial adhesion between the fiber and the rubber. Through hydrogen bonding and/or π-π stacking between the TP layer and the ANF, the ANF coating is firmly attached to the surface of AF. Compared with the untreated fiber, the interfacial adhesion of AF coated with ANF after 1, 3, 5, 7, 9 deposition cycles is increased by 27.8%, 29.1%, 31.5%, 43.1%, and 30.3%, and the mechanical properties of the fibers remain almost unchanged. This method shows its advantages of simple, facile, and time-effective, which is of great significance for industrial applications.     

Tensile stress relaxation of short‐coir‐fiber‐reinforced natural rubber composites

The stress relaxation behavior of natural rubber (NR) and its composites reinforced with short coir fibers under tension was analyzed. The rate of stress relaxation was a measure of the increase in the entropy of the compounds: the higher the rate was, the greater the entropy was. At lower strain levels, the relaxation mechanism of NR was independent of strain level. However, the rate of relaxation increased with the strain level. Also, the strain level influenced the rate of stress relaxation considerably in the coir‐reinforced NR composites. However, the relaxation mechanisms of both the unfilled compound and the composite were influenced by the strain rate. The rate of relaxation was influenced by fiber loading and fiber orientation. From the rate of stress relaxation, we found that fiber–rubber adhesion was best in the composite containing fibers subjected to a chemical treatment with alkali, toluene diisocyanate, and NR solutions along with a hexaresorcinol system as a bonding agent. In this study, the stress relaxation curves could not be viewed as segments with varying slopes; however, a multitude of inflection points were observed on the curves. Hence, we propose neither a two‐step nor three‐step mechanism for the coir‐fiber‐reinforced NR composites as reported for some other systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 96–104, 2004     

Short sisal fiber‐reinforced tire rubber composites: Dynamic and mechanical properties

The world tendency toward using recycled materials demands new products from vegetable resources and waste polymers. In this work, composites made from powdered tire rubber (average particle size: 320 μm) and sisal fiber were prepared by hot‐press molding and investigated by means of dynamic mechanical thermal analysis and tensile properties. The effects of fiber length and content, chemical treatments, and temperature on dynamic mechanical and tensile properties of such composites were studied. The results showed that mercerization/acetylation treatment of the fibers improves composite performance. Under the conditions investigated the optimum fiber length obtained for the tire rubber matrix was 10 mm. Storage and loss moduli both increased with increasing fiber content. The results of this study are encouraging, demonstrating that the use of tire rubber and sisal fiber in composites offers promising potential for nonstructural applications. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 670–677, 2004     

Effects of the short‐fiber tip geometry and interphase properties on the interfacial debonding behavior of rubber matrix composites

An axisymmetric finite element model of a single fiber embedded in a rubber matrix was established. A cohesive zone model was used for the fiber–matrix interface because of the interfacial failure. The effect of the fiber tip shape on the interfacial debonding of short‐fiber‐reinforced rubber matrix sealing composites (SFRCs) was investigated; the shapes were flat, semi‐elliptical, hemispherical, and conoid, respectively. The initial strain of the interfacial debonding (ε₀) was obtained. We found that among the researched fiber tips, ε₀ of the SFRC reinforced with the hemispherical tip fiber appeared to be the maximum. The initial locations of interfacial debonding were also determined. The results show that the initial locations of the interfacial debonding moved from the edge to the center of the fiber tip when the ratio of the semimajor axis and semiminor axis of the semi‐elliptical fiber tip increased gradually. Further study on the effect of the interphase properties on ε₀ with the hemispherical fiber tip was conducted. The results indicate that an interphase thickness of 0.2 μm and an interphase elastic modulus of about 752 MPa were optimal for restraining the initiation of the interfacial debonding. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42774.     

Surface modification of polyimide fibers by novel alkaline–solvent hydrolysis to form high‐performance fiber‐reinforced composites

We modified polyimide (PI) fibers by a novel hydrolysis approach and fabricated PI‐fiber‐reinforced novolac resin (NR) composites with enhanced mechanical properties. We first used an alkaline–solvent mixture containing potassium hydroxide liquor and dimethylacetamide (DMAc) for the surface modification of the PI fibers. The results indicate that the surface roughness and structure of the PI fibers were controlled by the hydrolysis time and the content of DMAc. With the optimized hydrolysis conditions, the tensile modulus of modified PI fibers improved 15% without compromises in the fracture stress, fracture strain, or thermal stability. The interfacial shear strength between the modified PI fibers and NR increased 57%; this indicated a highly enhanced interfacial adhesion. Finally, the tensile and flexural strengths of the composites increased 72 and 53%, respectively. This research provides an effective method for the surface modification of PI fibers and expands their applications for high‐performance composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46595.     

Strength,permeability, and durability of hybrid fiber‐reinforced concrete containing styrene butadiene latex

Hybrid fiber‐reinforced concrete (HFRC) is examined in this study. Two types of synthetic fibers were considered: polyvinyl alcohol fiber/macro synthetic fiber (PVA/MSF) and polypropylene fiber (PP)/MSF. Styrene butadiene latex was added at 0%, 5%, 10%, and 15% of the cement weight. Tests carried out for the study included compressive strength, flexural strength, chloride ion penetration, abrasion resistance, and impact resistance. The results demonstrated that higher latex contents improved the dispersibility of the fibers because of the increased workability of the HFRC and the improved adhesion. Formation of a latex film improved the strength, permeability resistance, abrasion resistance, and impact resistance. PVA/MSF HFRC had better properties than PP/MSF HFRC. This was attributed to stronger hydrogen bonding by the hydrophilic PVA fibers, which led to superior resistance to micro‐cracking and crack propagation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Tribological behavior of short‐fiber‐reinforced polyimide composites under dry‐sliding and water‐lubricated conditions

Polyimide composites reinforced with short‐cut fibers such as carbon, glass, and quartz fibers were fabricated by the polymerization of monomer reactants process. The mechanical properties of the composites with different fiber contents were evaluated. The friction and wear properties of the polyimide and its composites were investigated under dry‐sliding and water‐lubricated conditions. The results indicated that the short‐carbon‐fiber‐reinforced polyimide composites had better tensile and flexural strengths and improved tribological properties in comparison with glass‐fiber‐ and quartz‐fiber‐reinforced polyimide composites. The incorporation of short carbon fibers into the polyimide contributed to decreases in the friction coefficient and wear rate under both dry and water‐lubricated conditions and especially under water lubrication because of the boundary lubrication effect of water. The polyimide and its composites were characterized by plastic deformation, microcracking, and spalling under both dry and water‐lubricated conditions, which were significantly abated under the water‐lubricated condition. The glass and quartz fibers were easily abraded and broken; the broken fibers transferred to the mating metal surface and increased the surface roughness of mating stainless steel, which led to the wear rate increasing for the glass‐fiber‐ and quartz‐fiber‐reinforced polyimide composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Half‐submerged cultivation method for the microbial desulfurization of waste latex rubber

The common method for microbial desulfurization is the submerged cultivation method. However, its cost is high because of the high consumption of the medium. To cut costs and improve the desulfurization effect, the new half‐submerged cultivation method was used in the microbial desulfurization of waste latex rubber (WLR) by Sphingomonas species With this method, much more WLR was added per unit volume of the culture medium to be desulfurized, and the desulfurization process was done without stirring. The technical conditions, such as the addition of WLR, the addition of polysorbate 80 (Tween 80), and the desulfurization time, for the half‐submerged cultivation method were studied, and its desulfurization effect was compared with that of the traditional submerged cultivation method. The results show that the optimum conditions for the half‐submerged cultivation method were the addition of 40% w/v WLR in the medium without Tween 80 and desulfurization for 10 days. The X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results demonstrate that the decreases in the content of sulfur, S? C bonds, and S? S bonds on the surface of WLR after desulfurization by the half‐submerged cultivation method were greater than those after desulfurization by the submerged cultivation method. The composite of waste latex rubber desulfurized by the submerged cultivation method (SDWLR) and styrene–butadiene rubber (SBR) had better mechanical properties than the composite of waste latex rubber desulfurized by the half‐submerged cultivation method (HDWLR) and SBR. Scanning electron microscopy photographs showed that the combinations of HDWLR and the matrix were better than those of SDWLR and the matrix. Compared with the submerged cultivation method, the half‐submerged cultivation method not only reduced the cost of desulfurization but also improved the desulfurization effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41039.     

Friction and wear properties of dumbbell‐shaped jute fiber‐reinforced friction materials

The surfaces of jute fibers (Corchorus capsularis L.) were processed to have different dumbbell‐shaped spacing (5 mm, 10 mm, 15 mm, and 20 mm), and the physical properties of the modified surfaces of the jute fibers were evaluated in this study. The dumbbell‐shaped jute fiber (DJF)‐reinforced friction materials were prepared through compression mold. The friction and wear performance of the DJF were tested using a friction material tester at constant speed. The results showed that the dumbbell‐shaped spacing has less influence on the friction coefficients of friction materials. The friction coefficients of DJF have bigger fluctuation compared with that of straight fiber during the temperature‐increasing procedure. The wear rate of DJF with dumbbell‐shaped spacing of 15 mm was the lowest, except for that when the temperatures were about 200–250°C. Morphologies of wear surfaces of DJF were observed using scanning electron microscopy and the friction characteristics were analyzed. The results showed that reinforced with DJFs in the friction materials can reduce the specific wear rate and the variation in friction coefficient compared with that of straight jute fibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40748.     

Construction of an in situ interfacial layer for aramid fiber reinforced styrene butadiene rubber composites

In this work, the in situ interface layer composite was prepared by using the coating agent dispersion. Aramid fiber (AF) was modified with lithium chloride aqueous solution, and then coated with the blends of a low-molecular weight maleated polybutadiene liquid rubber (MLPB), the epoxy resin (E51), and 2-ethyl-4-methylimidazole (2E4MZ). The in situ interface layer was formed via the reaction of epoxy group with anhydride group in the presence of the accelerator 2E4MZ and covulcanization of MLPB with styrene butadiene rubber (SBR) in the process of preparing vulcanized AF reinforced SBR. It can be seen from analysis of scanning electronic microscopy, attenuated total reflection Fourier transform infrared, and thermogravimetric analysis that the in situ interfacial layer was a uniform and dense interfacial layer on the fiber surface and was not be destroyed during processing. The results of the dynamic mechanical analysis and mechanical properties showed that the in situ interface layer formed in processing had higher flexibility and better integrity than the interface layer prepared before processing, which is favorable for stress relaxation, and the in situ interface layer imparts better tensile strength and tear strength to the composite. The 100% modulus of composites with in situ interface layers was 14.6% higher than that of composites prepared without uncoated AF.     

Study on properties of natural rubber reinforced by poly(sodium‐4‐styrenesulfonate)‐decorated carbon black with a latex compounding technique

Natural rubber filled with poly(sodium‐4‐styrenesulfonate) (PSS)‐decorated carbon black (CB) by employing a latex compounding technique was prepared. The result of scanning electron microscope demonstrated that CB was uniformly dispersed in the matrix. Comparing to traditional dry compounding, an improvement in physical and mechanical properties was observed in the composites attributed to the homogeneous distribution of CB in matrix and an augment of bound rubber. Owing to the changes of the physical properties of CB surface, vulcanizate filled with oxidized CB via latex way exhibited higher mechanical properties. The resulting vulcanizates displayed a diminished interaction between fillers based on the consequence of strain dependence of storage modulus. Furthermore, a splendid wet‐skid resistance was obtained in vulcanizates fabricated by latex compounding technique in comparison with vulcanizates prepared by traditional dry compounding. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42346.     

Effect of rare earth elements surface treatment on tensile properties of aramid fiber‐reinforced epoxy composites

Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of aramid fiber. Tensile properties of both the aramid/epoxy composites and single fibers were tested. The effects of RES concentration on tensile properties of aramid/epoxy composites were investigated in detail to explore an optimum amount of rare earth elements in solution for modifying aramid fiber. The fracture surface morphologies of tensile specimens were observed and analyzed with the aid of SEM. The experimental results show that rare earth treatment is superior to ECP grafting treatment in promoting interfacial adhesion between the aramid fiber and epoxy matrix. Meanwhile, the tensile strengths of single fibers were almost not affected by RES treatment. The optimum performance is obtained when the content of rare earth elements is 0.5 wt %. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1037–1041, 2004     

Barrier properties for short‐fiber‐reinforced epoxy foams

The barrier properties of short‐fiber‐reinforced epoxy foam are characterized and compared with unreinforced epoxy foam in terms of moisture absorption, flammability properties, and impact properties. Compression and shear properties are also included to place in perspective the mechanical behavior of these materials. Compared with conventional epoxy foam, foam reinforced with aramid fibers exhibits higher moisture absorption and lower diffusion, while glass‐fiber‐reinforced foam is significantly stiffer and stronger. In addition, the polymeric foam composites studied present superior fire‐resistance compared with conventional epoxy foam systems. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3266–3272, 2006     

Modeling and simulation of fiber‐reinforced polymer mold‐filling with phase change

A gas‐solid‐liquid three‐phase model for the simulation of fiber‐reinforced composites mold‐filling with phase change is established. The influence of fluid flow on the fibers is described by Newton's law of motion, and the influence of fibers on fluid flow is described by the momentum exchange source term in the model. A revised enthalpy method that can be used for both the melt and air in the mold cavity is proposed to describe the phase change during the mold‐filling. The finite‐volume method on a non‐staggered grid coupled with a level set method for viscoelastic‐Newtonian fluid flow is used to solve the model. The “frozen skin” layers are simulated successfully. Information regarding the fiber transformation and orientation is obtained in the mold‐filling process. The results show that fibers in the cavity are divided into five layers during the mold‐filling process, which is in accordance with experimental studies. Fibers have disturbance on these physical quantities, and the disturbance increases as the slenderness ratio increases. During mold‐filling process with two injection inlets, fiber orientation around the weld line area is in accordance with the experimental results. At the same time, single fiber's trajectory in the cavity, and physical quantities such as velocity, pressure, temperature, and stresses distributions in the cavity at end of mold‐filling process are also obtained. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42881.     

Cure characteristics and mechanical properties of short nylon fiber‐reinforced nitrile rubber composites

Acrylonitrile butadiene rubber (NBR)‐based composites were prepared by incorporating short nylon fibers of different lengths and concentration into the matrix using a two‐roll mixing mill according to a base formulation. The curing characteristics of the samples were studied. The influence of fiber length, loading, and rubber crosslinking systems on the properties of the composites was analyzed. Surface morphology of the composites has been studied using Scanning Electron Microscopy (SEM). Addition of nylon fiber to NBR offers good reinforcement, and causes improvement in mechanical properties. A fiber length of 6 mm was found to be optimum for the best balance of properties. It has been found that at higher fiber loadings, composites show brittle‐type behavior. Composites vulcanized by the dicumyl peroxide (DCP) system were found to have better mechanical properties than that by the sulfur system. The swelling behavior of the composites in N,N‐dimethyl formamide has been analyzed for the swelling coefficient values. Composites vulcanized in the DCP system were found to have higher rubber volume fraction than that in the sulfur system, which indicates better rubber–fiber interaction in the former. The crosslink densities of various composites were also compared. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1023–1030, 2004     

Mechanical and physical characteristics of cellulose‐fiber‐filled polyacetal composites

We investigated the mechanical and physical characteristics of composites composed of polyacetal [alternatively called polyoxymethylene (POM)] and cellulose fiber (CelF) derived from wood pulp [10–52 wt % (9.3–50.1 vol %)] without any fiber surface treatment. The modulus, deflection temperature under load, and thermal conduction coefficient of the POM/CelF composites were effectively enhanced with increasing CelF content, and the composites had an advantage of specific modulus compared to glass fiber (GF)‐filled POM. The flexural modulus of POM/CelF 40 wt % (38.2 vol %) was measured to be about 6 GPa, which was comparable to that of POM/GF 20 wt % (12.1 vol %). In the composites, the CelFs were distributed randomly as monofilaments, and the debonding of the interface between the fibers and POM matrices in the fracture faces was confirmed as less by scanning electron microscopy observation. The POM/CelF composites possessed lower specific wear rates than the POM/GF composites, and they had damping behaviors near that of neat POM. No clear dependence of the melt flow index of the base POM on these characteristics was observed, except on Charpy impact strength. The composites studied here were unique in their performance and ability to be designed in accordance with specific demands, and they could be potential replacements for mineral‐filled and GF‐filled POM composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Curing characteristics and mechanical properties of alkali‐treated grass‐fiber‐filled natural rubber composites and effects of bonding agent

To improve adhesion between fiber and matrix, natural rubber was reinforced with a special type of alkali‐treated grass fiber (Cyperus Tegetum Rox b). The cure characteristics and mechanical properties of grass‐fiber‐filled natural rubber composites with different mesh sizes were studied with various fiber loadings. Increasing the amount of fibers resulted in the composites having reduced tensile strength but increased modulus. The better mechanical properties of the 400‐mesh grass‐fiber‐filled natural rubber composite showed that the rubber/fiber interface was improved by the addition of resorcinol formaldehyde latex (RFL) as bonding agent for this particular formulation. The optimum cure time decreased with increases in fiber loading, but there was no appreciable change in scorch time. Although the optimum cure time of vulcanizates having RFL‐treated fibers was higher than that of the other vulcanizates, it decreased with fiber loading in the presence of RFL as the bonding agent. But this value was lower than that of the rubber composite without RFL. Investigation of equilibrium swelling in a hydrocarbon solvent was also carried out. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3151–3160, 2006     

Structure and adhesive properties of the RFL‐coated continuous basalt fiber cord/rubber interface

The relationships between the structure of the resorcinol‐formaldehyde‐latex (RFL) layer, static adhesion, and interfacial fatigue properties between the RFL‐coated continuous basalt fiber (CBF) cord and a rubber matrix were studied using films prepared from RFL systems with various formulas and H samples prepared with RFL‐coated CBF cord and NR/SBR matrix. Thermomechanical analysis and tensile testing of the RFL films were carried out using a dynamic mechanical analyzer (DMA). The H pull‐out force and fatigue properties were tested using a universal testing machine and an MTS, respectively. The interfacial fatigue life of the RFL‐coated CBF cord/rubber samples exhibited different variation regularity from the variation of the H pull‐out force as F/R and L/RF changed. The static adhesion reflected the connection strength between the cord and the rubber matrix, whereas the characteristics and the properties of the RFL layer played a decisive role in determining the damage rate of the adhesion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44353.     

Environmental durability of banana‐fiber‐reinforced phenol formaldehyde composites

We explored the environmental aging behavior of banana‐fiber‐reinforced phenol formaldehyde (PF) composites. The composites were subjected to water aging, thermal aging, soil burial, and outdoor weathering. The effects of chemical modification and hybridization with glass fibers on the degradability of the composites in different environments were analyzed. The extent of degradation was measured by changes in the weight and tensile properties after aging. Absorbed water increased the weight of water‐aged composites, and chemical treatments and hybridization decreased water absorption. The tensile strength and modulus of the banana/PF composites were increased by water aging, whereas the strength and modulus of the glass/PF composites were decreased by water aging. As the glass‐fiber loading was increased in the hybrid composites, the increase in strength by water aging was reduced, and at higher glass‐fiber loadings, a decrease in strength was observed. The tensile properties of the composites were increased by oven aging. The percentage weight loss was higher for soil‐aged samples than for samples weathered outdoors. The weight loss and tensile strength of the glass/PF composites and banana/glass/hybrid/PF composites were much lower than those of the banana/PF composites. Silane treatment, NaOH treatment, and acetylation improved the resistance of the banana/PF composites on outdoor exposure and soil burial. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2521–2531, 2006