Short melamine fiber filled nitrile rubber composites

This article reports the development of a new composite based on acrylonitrile butadiene rubber (NBR) and melamine fiber. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to study the effect of a dry bonding system in improving the adhesion between the fiber and the matrix. Mechanical properties of the composites are improved in the presence of the dry bonding system comprising of resorcinol, hexamethylene tetramine (hexamine), and hydrated silica. SEM and atomic force microscopic (AFM) images show that there are distinct changes in the fiber‐matrix interphase with the incorporation of the dry bonding system. A strong attachment of the fiber to the matrix is found in the SEM photomicrographs of the tensile fracture surfaces of the composites containing the dry bonding system. AFM section analysis and surface plot show that the improvement in tensile strength and modulus in the presence of the dry bonding system is due to the formation of a well‐defined interphase between the fiber and the matrix. The width of the interphase between the fiber and the matrix is increased in the presence of the dry bonding system, which is reflected in the mechanical properties and aging characteristics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 544–558, 2003     

Permeability and mechanical property correlation of bio based epoxy reinforced with unidirectional sisal fiber mat through vacuum infusion molding technique

The present investigation is focused to study the permeability of natural fiber during vacuum infusion (VI) process and the effect of the surface treatments of natural fiber, fiber loading direction, resin flow direction and process parameter on the tensile properties of developed composites (sisal/bio based epoxy). The bio based resin exhibits good flow characteristics in NaOH and isocyanate treated fibers which may be attributed to change in polarity. The surface treatments appear to provide an appreciable enhancement in tensile strength through enhanced bonding between fiber and matrix. The longitudinal tensile strength has been found to be higher than that of the transverse direction and the flow along the fiber provides maximum tensile strength. It has also been demonstrated that VI process provides improved mechanical properties as compared to hand‐layup process. Morphological studies of fractured developed composites were performed by scanning electron microscopy (SEM) to understand the de‐bonding of fiber/matrix adhesion. POLYM. COMPOS., 38:2192–2200, 2017. © 2015 Society of Plastics Engineers     

Dynamic mechanical properties of oil palm microfibril‐reinforced natural rubber composites

The dynamic mechanical properties of macro and microfibers of oil palm‐reinforced natural rubber (NR) composites were investigated as a function of fiber content, temperature, treatment, and frequency. By the incorporation of macrofiber to NR, the storage modulus (E') value increases while the damping factor (tan δ) shifts toward higher temperature region. As the fiber content increases the damping nature of the composite decreases because of the increased stiffness imparted by the natural fibers. By using the steam explosion method, the microfibrils were separated from the oil palm fibers. These fibers were subjected to treatments such as mercerization, benzoylation, and silane treatment. Resorcinol‐hexamethylenetetramine‐hydrated silica was also used as bonding agent to increase the fiber/matrix adhesion. The storage modulus value of untreated and treated microfibril‐reinforced composites was higher than that of macrofiber‐reinforced composites. The T_g value obtained for this microfibril‐reinforced composites were slightly higher than that of macrofiber‐reinforced composites. The activation energy for the relaxation processes in different composites was also calculated. The morphological studies using scanning electron microscopy of tensile fracture surfaces of treated and untreated composites indicated better fiber/matrix adhesion in the case of treated microfibril‐reinforced composites. Finally, attempts were made to correlate the experimental dynamic properties with the theoretical predictions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Short glass fiber reinforced ABS and ABS/PA6 composites: Processing and characterization

In this study acrylonitrile‐butadiene‐styrene (ABS) terpolymer was reinforced with 3‐aminopropyltrimethoxysilane (APS)‐treated short glass fibers (SGFs). The effects of SGF concentration and extrusion process conditions, such as the screw speed and barrel temperature profile, on the mechanical properties of the composites were examined. Increasing the SGF concentration in the ABS matrix from 10 wt% to 30 wt% resulted in improved tensile strength, tensile modulus and flexural modulus, but drastically lowered the strain‐at‐break and the impact strength. The average fiber length decreased when the concentration of glass fibers increased. The increase in screw speed decreased the average fiber length, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength were affected negatively and the strain‐at‐break was affected positively. The increase in extrusion temperature decreased the fiber length degradation, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength increased. At higher temperatures the ABS matrix degraded and the mechanical strength of the composites decreased. To obtain a strong interaction at the interface, polyamide‐6 (PA6) at varying concentrations was introduced into the ABS/30 wt% SGF composite. The incorporation and increasing amount of PA6 in the composites broadened the fiber length distribution (FLD) owing to the low melt viscosity of PA6. Tensile strength, tensile modulus, flexural modulus, and impact strength values increased with an increase in the PA6 content of the ABS/PA6/SGF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength to flexural strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/SGF composites, which exhibited an improved adhesion between the SGFs and the ABS/PA6 matrix. POLYM. COMPOS. 26:745–755, 2005. © 2005 Society of Plastics Engineers     

Short sisal fiber reinforced styrene-butadiene rubber composites

Styrene-butadiene rubber (SBR) composites were prepared by incorporating short sisal fibers of different lengths and concentrations into the SBR matrix in a mixing mill according to a base formulation. The curing characteristics of the mixes were studied and the samples were vulcanized at 150°C. The properties of the vulcanizates such as stress-strain behavior, tensile strength, modulus, shore-A hardness, and resilience were studied. Both the cured and uncured properties showed a remarkable anisotropy. It has been found that aspect ratio in the range of 20–60 is effective for sufficient reinforcement. The mechanical properties were found to increase along and across the grain direction with the addition of fibers. The effects of fiber length, orientation, loading, type of bonding agent, and fiber-matrix interaction on the properties of the composites were evaluated. The extent of fiber orientation was estimated from green strength measurements. The adhesion between the fiber and the rubber was enhanced by the addition of a dry bonding system consisting of resorcinol and hexamethylene tetramine. The bonding agent provided shorter curing time and enhanced mechanical properties. The tensile fracture surfaces of the samples have been examined by scanning electron microscopy (SEM) to analyze the fiber surface morphology, orientation, fiber pull-out, and fiber-matrix interfacial adhesion. Finally, anisotropic swelling studies were carried out to analyze the fiber-matrix interaction and fiber orientation. © 1995 John Wiley & Sons, Inc.     

Preparation of rubber composites from ground tire rubber reinforced with waste‐tire fiber through mechanical milling

Composites made from ground tire rubber (GTR) and waste fiber produced in tire reclamation were prepared by mechanical milling. The effects of the fiber content, pan milling, and fiber orientation on the mechanical properties of the composites were investigated. The results showed that the stress‐induced mechanochemical devulcanization of waste rubber and the reinforcement of devulcanized waste rubber with waste‐tire fibers could be achieved through comilling. For a comilled system, the tensile strength and elongation at break of revulcanized GTR/fiber composites reached maximum values of 9.6 MPa and 215.9%, respectively, with 5 wt % fiber. Compared with those of a composite prepared in a conventional mixing manner, the mechanical properties were greatly improved by comilling. Oxygen‐containing groups on the surface of GTR particles, which were produced during pan milling, increased interfacial interactions between GTR and waste fibers. The fiber‐filled composites showed anisotropy in the stress–strain properties because of preferential orientation of the short fibers along the roll‐milling direction (longitudinal), and the adhesion between the fiber and rubber matrix was improved by the comilling of the fiber with waste rubber. The proposed process provides an economical and ecologically sound method for tire‐rubber recycling. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4087–4094, 2007     

Morphology/behavior relationship and recyclability of composites based on PP/EPDM blends and short aramid fibers

The effect of short aramid fibers on the mechanical behavior of polypropylene (PP) and ethylene‐propylene‐diene (EPDM) and their blends has been investigated by means of an experimental design. The results have shown that aramid fibers are very effective reinforcing agents for composites when the continuous phase of the matrix is constituted by PP, so sensible increments in tensile modulus and strength are obtained as fiber content in the composites increases. An optimal matrix composition and fiber content has been observed that produced high abrasion resistance compounds. However, the abrasion resistance of very rich EPDM matrices is hardly affected by fibers content. The addition of fibers to EPDM rich (>50%) matrices gives rise to a sensible decrease of the impact strength of this polymer. However, at PP contents above 50% in the polymer matrix, an increase of impact strength is observed at fiber percentages in the composites above 10%. The different behavior of the fibers depending on matrix type can be attributed to a better affinity of these fibers for PP matrix. Morphological studies of the composites have been carried out by scanning electron microscopy. Finally, the price and recyclability of these materials have been analyzed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2474–2484, 2002     

Polymerization compounding composites of nylon‐6,6/short glass fiber

Nylon‐6,6 was grafted onto the surface of short glass fibers through the sequential reaction of adipoyl chloride and hexamethylenediamine onto the fiber surface. Grafted and unsized short glass fibers (USGF) were used to prepare composites with nylon‐6,6 via melt blending. The glass fibers were found to act as nucleating agents for the nylon‐6,6 matrix. Grafted glass fiber composites have higher crystallization temperatures than USGF composites, indicating that grafted nylon‐6,6 molecules further increase crystallization rate of composites. Grafted glass fiber composites were also found to have higher tensile strength, tensile modulus, dynamic storage modulus, and melt viscosity than USGF composites. Property enhancement is attributed to improved wetting and interactions between the nylon‐6,6 matrix and the modified surface of glass fibers, which is supported by scanning electron microscopy (SEM) analysis. The glass transition (tan δ) temperatures extracted from dynamic mechanical analysis (DMA) are found to be unchanged for USGF, while in the case of grafted glass fiber, tan δ increases with increasing glass fiber contents. Moreover, the peak values (i.e., intensity) of tan δ are slightly lower for grafted glass fiber composites than for USGF composites, further indicating improved interactions between the grafted glass fibers and nylon‐6,6 matrix. The Halpin‐Tsai and modified Kelly‐Tyson models were used to predict the tensile modulus and tensile strength, respectively.     

Effect of short polyethylene terephthalate fibers on properties of ethylene-propylene diene rubber composites

The alteration in some properties of electron beam (EB) cured ethylene-propylene diene rubber (EPDM) reinforced by polyethylene terephthalate (PET) fiber was investigated in this study. Bonding system Resorcinol/Hexamethylenetetramine/Silica (RHS) was used to enhance the fiber/EPDM adhesion and to maintain optimum composite strength properties. Mechanical properties of composites namely; tensile strength, hardness and modulus at 100 % elongation have been enhanced by adding PET fibers and increasing irradiation dose. Moreover, the effect of fiber loading and irradiation dose on the soluble fraction behavior of the composite in benzene was also investigated. The soluble fraction of the composites decreased with increasing the fiber loading and irradiation dose. The extent of fiber alignment and strength of fiber-rubber interface adhesion were analyzed from the anisotropic swelling measurements. In addition, thermal stability of the composites was increased. Besides, the mechanical properties like tensile strength and stiffness were improved by thermal ageing. Scanning electron microscopy (SEM) for the fractured surfaces and Wide- angle X- ray diffraction (WAXD) of the investigated samples confirmed that the adhesion occurred between fibers and EPDM.     

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     

Dynamic mechanical analysis of oil palm microfibril‐reinforced acrylonitrile butadiene rubber composites

The dynamic mechanical properties of microfibers of oil palm‐reinforced acrylonitrile butadiene rubber (NBR) composites were investigated as a function of fiber content, temperature, treatment, and frequency. The storage modulus (E′) was found to increase with weight fraction of microfibrils due to the increased stiffness imparted by the strong adhesion between the polar matrix and the hydrophilic microfibrils. The damping properties were found to decrease with increase in fiber loading. As the fiber content increases, the damping nature of the composite decreases because of the increased stiffness imparted by the natural fibers. By steam explosion method (STEX), microfibrils are separated from fibers. Natural fibers were undergone treatment such as mercerization, benzoylation, and silane treatment. The NBR is modified by the addition of resorcinol‐hexa‐hydrated silica (HRH) bonding agent. Also dicumyl peroxide (DCP) is used as an alternating vulcanizing agent in the system. In the case of composites containing chemically modified fibers, storage modulus were found to increase. Cole–Cole analysis was made to study the phase behavior of the composite samples. Activation energy for the relaxation processes in different composites was calculated. Morphological studies using scanning electron microscopy of tensile fracture surfaces of treated and untreated composites indicated better fiber matrix/adhesion in the case of treated microfibril‐reinforced composites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Effect of macromolecular coupling agent on the property of PP/GF composites

Silane‐grafted polypropylene manufactured by a reactive grafting process was used as the coupling agent in polypropylene/glass‐fiber composites to improve the interaction of the interfacial regions. Polypropylene reinforced with 30% by weight of short glass fibers was injection‐molded and the mechanical behaviors were investigated. The results indicate that the mechanical properties (tensile strength, tensile modulus, flexural strength, flexural modulus, and Izod impact strength) of the composite increased remarkably as compared with the noncoupled glass fiber/polypropylene. SEM of the fracture surfaces of the coupled composites shows a good adhesion at the fiber/matrix interface: The fibers are coated with matrix polymer, and a matrix transition region exists near the fibers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1537–1542, 1999     

Mechanical properties of phenolic composites reinforced with jute/cotton hybrid fabrics

Mechanical properties (tensile, flexural, impact, and dynamic mechanical thermal analysis) of novolac type phenolic composites reinforced with jute/cotton hybrid woven fabrics were investigated as a function of fiber orientation and roving/fabric characteristics. Scanning electron microscopy (SEM) was carried out to investigate the fiber‐matrix adhesion. Results showed that the composite properties are strongly influenced by test direction and rovings/fabric characteristics. The anisotropy degree was shown to increase with test angle and to strongly depend on the type/architecture of fabric used, i.e., jute rovings diameter, relative fiber content, etc. It was possible to obtain composites with higher mechanical properties and lower anisotropy degree by producing cross‐ply laminates. Best overall mechanical properties were obtained for the composites tested along the jute rovings direction. Composites tested at 45° and 90° with respect to the jute roving direction exhibited a controlled brittle failure combined with a successive fiber pullout, while those tested in the longitudinal direction (0°) exhibited a catastrophic failure mode. Our results indicate that jute promotes a higher reinforcing effect and cotton avoids catastrophic failure. Therefore, this combination of natural fibers is suitable to product composites for lightweight structural applications. POLYM. COMPOS., 26:1–11, 2005. © 2004 Society of Plastics Engineers.     

Thermal aging of bentonite‐filled ethylene propylene diene monomer composites

Bentonite‐filled ethylene propylene diene monomer (EPDM/Bt) composites were prepared using two roll mill compounding method and the effect of Bt loading on the thermal aging, swelling resistance and crosslink density of EPDM/Bt composites were studied. The effect of in situ addition of different silane coupling agents (SCAs) on the above properties at optimum Bt loading of EPDM/Bt composite was also investigated. Thermal aging test results show that the tensile strength and tensile modulus at 100% elongation (M100) increase initially for 2 days aged composites and decrease slightly after 4 days of aging, meanwhile the elongation at break (E_b) decrease gradually with aging period as compared to the unaged composites. Upon aging, swelling resistance increase initially indicating increased crosslink density of EPDM/Bt composite due to post‐curing and reduced after 4 days of aging due to crosslink destruction and EPDM chain scissioning. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4419–4427, 2013     

Processability and mechanical properties of ternary composites PP/EPDM/GF

The enhancement of the mechanical properties of neat PP is achieved by the addition of glass fibers and EPDM rubber. The Young's modulus and notched Charpy impact strength of the composites obtained are improved with respect to the original polymer, leading to a new composite material with a very good balance of toughness and rigidity properties. The tensile behavior of these multiphase systems is successfully compared with theoretical predictions using the Halpin‐Tsai/Nielsen theory for uniaxially short fiber composites, which considers the matrix as a blend with spherical particles and can predict the tensile modulus considering an average fiber orientation angle. An accurate morphological study performed by scanning electron microscopy (SEM) shows a very good dispersion of the rubbery phase into the neat matrix. No special affinity between the rubber and the fibers is reported. The good dispersion and the small particle diameter indicate the good processability of the ternary systems studied.     

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     

Structural investigations of acrylonitrile–vinyl acid copolymers by NMR spectroscopy

This article reports the development of new composites based on maleated ethylene–propylene–diene monomer (EPDM) rubber and melamine fiber. The compositions are cured using three different types of curing systems: conventional covalent crosslinking based on sulfur and an accelerator, fully ionic crosslinking based on zinc oxide/zinc stearate, and mixed crosslinking involving both covalent and ionic bonds. A dry bonding system comprising resorcinol, hexamethylene tetramine, and hydrated silica, popularly known as HRH, is found to increase the mechanical properties of the composites cured using both the sulfur/accelerator and mixed crosslinking systems. However, incorporation of the dry bonding system and/or melamine fiber adversely affects the strength of the composites if the linkages are fully ionic. Among the three crosslinking systems employed, composites prepared by using the mixed crosslinking system give higher tensile strength and modulus. Aging at 150°C for 48 h causes improvement in the strength and modulus of the composites cured by using the sulfur/accelerator system, particularly at higher fiber loading. However, in the case of an ionic system, both the modulus and strength drop with aging; in the case of the mixed crosslinking system, the modulus increases, but there is a drop in strength on aging. Rheological studies of the uncured compounds show that the presence of zinc stearate in the formulations of mixed and ionic crosslinking systems results in reduced viscosity and a smoother extrudate as compared to the sulfur crosslinking system. An atomic force microscopy analysis of the roughness reveals that the fiber surface roughness is reduced because of aging for the ionic crosslinking system. This is attributable to the formation of a zinc stearate layer on the fiber surface, which also reduces the adhesion between the fiber and the matrix, thereby reducing the hysteresis after aging. However, for the sulfur and mixed crosslinking system, the roughness of the fiber surface is increased and there is a concomitant increase in hysteresis. © 2003 John Wiley Periodicals, Inc. J Appl Polym Sci 89: 1211–1229, 2003     

Pineapple leaf fiber reinforced thermoplastic composites: Effects of fiber length and fiber content on their characteristics

Pineapple leaf fiber (PALF) was used as a reinforcement in polyolefins. Polypropylene (PP) and low‐density polyethylene (LDPE) composites with different fiber lengths (long and short fibers) and fiber contents (0–25%) were prepared and characterized. The results showed that the tensile strength of the composites increased when the PALF contents were increased. It was observed that the composites containing long fiber PALF were stronger than the short fiber composites as determined by greater tensile strength. An SEM study on the tensile fractured surface confirmed the homogeneous dispersion of the long fibers in the polymer matrixes better than dispersion of the short fibers. The unidirectional arrangement of the long fibers provided good interfacial bonding between the PALF and polymer which was a crucial factor in achieving high strength composites. Reduction in crystallinity of the composites, as evident from XRD and DSC studies suggested that the reinforcing effect of PALF played an important role in enhancing their mechanical strength. From the rule of mixtures, the stress efficiency factors of the composite strength could be calculated. The stress efficiency factors of LDPE were greater than those of PP. This would possibly explain why the high modulus fiber (PALF) had better load transfers to the ductile matrix of LDPE than the brittle matrix of PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Kudzu fiber‐reinforced polypropylene composite

Kudzu fiber‐reinforced polypropylene composites were prepared, and their mechanical and thermal properties were determined. To enhance the adhesion between the kudzu fiber and the polypropylene matrix, maleic anhydride‐grafted polypropylene (MAPP) was used as a compatibilizer. A continuous improvement in both tensile modulus and tensile strength was observed up to a MAPP concentration of 35 wt %. Increases of 24 and 54% were obtained for tensile modulus and tensile strength, respectively. Scanning electron microscopy (SEM) showed improved dispersion and adhesion with MAPP. Fourier transform infrared (FTIR) spectroscopy showed an increase in hydrogen bonding with an increase in MAPP content. Differential scanning calorimetry (DSC) analysis indicated little change in the melting temperature of the composites with changes in MAPP content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1961–1969, 2002     

Elastomer composite based on EPDM reinforced with polyaniline coated curauá fibers prepared by mechanical mixing

Curauá fibers were used to reinforce elastomeric matrices with polyaniline (PAni) synthesized directly on the fiber surfaces to produce antistatic‐reinforced composites. In this work, composites of poly(ethylene‐co‐propylene‐co‐diene) with curauá fibers coated with PAni were prepared by mechanical mixing in a counter‐rotating twin rotor internal mixer. Then, mechanical and electrical properties of these composites were correlated to Raman and Fourier transformed infrared spectra (FTIR) using chemometric data analyze, such as principal component analysis (PCA) and hierarchical cluster analysis (HCA). Raman spectra showed correlation with electrical properties of conductive composites while FTIR spectra showed good correlation with mechanical properties. EPDM reinforced with PAni coated curauá fibers presented higher tensile strength and modulus than EPDM reinforced with pristine curauá fibers, indicating that the reinforcement effect was obtained. Chemical interaction between the phases occurs with formation of hydrogen bonding between the aminic nitrogens of PAni and the carbonyl groups of lignin of the fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40056.