Effects of filler–filler and polymer–filler interactions on rheological and mechanical properties of HDPE–wood composites

High‐density polyethylene (HDPE)–wood composite samples were prepared using a twin‐screw extruder. Improved filler–filler interaction was achieved by increasing the wood content, whereas improved polymer–filler interaction was obtained by adding the compatibilizer and increasing the melt index of HDPE, respectively. Then, effects of filler–filler and polymer–filler interactions on dynamic rheological and mechanical properties of the composites were investigated. The results demonstrated that enhanced filler–filler interaction induced the agglomeration of wood particles, which increased the storage modulus and complex viscosity of composites and decreased their tensile strength, elongation at break, and notched impact strength because of the stress concentration. Stronger polymer–filler interaction resulted in higher storage modulus and complex viscosity and increased the tensile and impact strengths due to good stress transfer. The main reasons for the results were analyzed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of coupling agent on the mechanical properties of fly ash–filled polybutadiene rubber

Fly ash, a waste productof thermal power stations generated in huge quantities, has been posing problems of its disposal. As such it contains a variety of inorganic oxides and is available in finely powdered form. Attempts have been made for its use as a filler in elastomers and plastics. It is important to note that fly ash used in in untreated form does not significantly enhance the mechanical properties of composites. In this work, fly ash treated with silane coupling agent (Si‐69) was used as a filler in polybutadiene rubber (PBR). The comparison of properties of composites filled with treated and untreated fly ash revealed that the composites with treated fly ash showed better reinforcing properties. Thus the silane coupling agent used here promoted adhesion between fly ash and the PBR. The improvement in mechanical properties in general and tensile properties (tensile strength, modulus 100% and modulus 200%, hardness) of the composites in particular were observed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1322–1328, 2004     

Understanding the mechanical and interfacial properties of core–shell structured bamboo–plastic composites

Core–shell structured bamboo–plastic composites (BPCs) were directly prepared with a single‐screw/single‐screw coextruder system. The effects of different shell layers, such as high‐density polyethylene (HDPE), bamboo pulp fiber (BPF)/HDPE, and white mud (WM)/HDPE, were studied in the context of the mechanical properties and the characteristics of the interfacial transition zone (ITZ) of BPC. The mechanical properties of the core–shell structured BPC were characterized by flexure, short‐beam shear, and impact tests. The surface morphologies of BPC were analyzed with field emission scanning electron microscopy. The ITZ properties were studied with dynamic mechanical analysis and nano‐indentation testing. The results show that the flexural properties, short‐beam strength, and impact strength decreased profoundly in the presence of BPF or WM. The dynamic mechanical analysis results suggest that the ITZ properties decreased, as indicated by the reductions in the storage modulus, loss modulus, and loss factor; the nano‐indentation results show that on the addition of BPF or WM, a gradient in the hardness and modulus of elasticity appeared across ITZ. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43053.     

Effects of palm ash loading and maleated natural rubber as a coupling agent on the properties of palm‐ash‐filled natural rubber composites

Natural rubber composites were prepared by the incorporation of palm ash at different loadings into a natural rubber matrix with a laboratory‐size two‐roll mill (160 × 320 mm²) maintained at 70 ± 5°C in accordance with the method described by ASTM D 3184–89. A coupling agent, maleated natural rubber (MANR), was used to improve the mechanical properties of the natural rubber composites. The results indicated that the scorch time and cure time decreased with increasing filler loading, whereas the maximum torque exhibited an increasing trend. Increasing the palm ash loading increased the tensile modulus, but the tensile strength, fatigue life, and elongation at break decreased. The rubber–filler interactions of the composites decreased with increasing filler loading. Scanning electron microscopy of the tensile fracture surfaces of the composites and rubber–filler interaction studies showed that the presence of MANR enhanced the interfacial interaction of the palm ash filler and natural rubber matrix. The presence of MANR also enhanced the tensile properties and fatigue life of palm‐ash‐filled natural rubber composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of filler surface treatment on mechanical properties and thermal properties of single and hybrid filler–filled PP composites

The influence of two types of surface treatments (aminosilane and Lica‐12) on the mechanical and thermal properties of polypropylene (PP) filled with single and hybrid filler (silica and mica) was studied. An improvement in tensile properties and impact strength was found for both treatments compared to those of untreated composites. However, the filler with silane coupling agent showed better improvement compared to the filler with Lica‐12 coupling agent. This was due to better adhesion between filler and matrix. Thermal analysis indicates that surface treatments increased the nucleating ability of filler, but decreased the coefficient of thermal expansion of PP composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of starch on the properties of carbon‐black‐filled styrene–butadiene rubber composites

The influence of starch on the properties of carbon‐black‐filled styrene–butadiene rubber (SBR) composites was investigated. When the starch particles were directly melt‐mixed into rubber, the stress at 300% elongation and abrasion resistance decreased evidently with increasing starch amount from 5 to 20 phr. Scanning electron microscopy observations of the abrasion surface showed that some apparent craters of starch particles were left on the surface of the composite, which strongly suggested that the starch particles were large and that interfacial adhesion between the starch and rubber was relatively weak. To improve the dispersion of the starch in the rubber matrix, starch/SBR master batches were prepared by a latex compounding method. Compared with the direct mixing of the starch particles into rubber, the incorporation of starch/SBR master batches improved the abrasion resistance of the starch/carbon black/SBR composites. With starch/SBR master batches, no holes of starch particles were left on the surface; this suggested that the interfacial strength was improved because of the fine dispersion of starch. Dynamic mechanical thermal analysis showed that the loss factor at both 0 and 60°C increased with increasing amount of starch at a small tensile deformation of 0.1%, whereas at a large tensile strain of 5%, the loss factor at 60°C decreased when the starch amount was varied from 5 to 20 phr. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of titanate coupling agent on the mechanical properties of clay‐filled polybutadiene rubber

Clays belong to an economic class of fillers, which are used extensively in rubbers and plastics. Being nonreinforcing in nature, there are limitations upon its use. If the properties of filler are modified, it will get a higher value as a filler. To achieve this modification of surface properties is one of the avenues. In the present work, the effect of treatment of the coupling agent on clay has been studied, with polybutadiene as a matrix. Composites were made with a varying proportion of untreated and treated clay. A two‐roll mill was used for dispersing the filler in the rubber, and a compression‐molding technique was used to cure the compounded in sheet forms. Tensile properties were measured on a computerized UTM using the ASTM procedure. Comparison of properties of composites filled with treated and untreated clay established that treatment of clay imparts better reinforcing properties. The properties under consideration were tensile strength, modulus at 100 and 400%, Young's modulus, hardness, etc. Tensile strength was improved by 52%, while modulus at 400% was improved by 150%. Similarly Young's modulus also was improved by 27%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1299–1304, 2004     

Effect of a coupling agent on the properties of hemp‐hurd‐powder‐filled styrene–butadiene rubber

Styrene–butadiene rubber (SBR) composites filled with hemp hurd powder (HP) were prepared with bis(3‐triethoxysilylpropyl) tetrasulfide (Si69) as a coupling agent. The effects of the filler content and coupling agent on the curing characteristics and dynamic mechanical properties of the composites were studied. The results indicate that with increasing filler loading, the torque values increased and the curing time decreased. The mechanical properties improved with increasing filled HP content up to 60 phr. Usually, long fibers led to a sharp decrease in the toughness of the composites, whereas short fibers, such as HP, had a positive effect on the elongation at break within the loading range studied. The extent of the filler–matrix interaction and the scanning electron micrographs of the fractured surfaces confirmed that the addition of Si69 improved the interfacial interaction between HP and the SBR matrix, which led to an increase in the maximum torque and the mechanical properties. Moreover, the coupling agent was helpful in dispersing the filler in the rubber matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal and mechanical properties of liquid silicone rubber composites filled with functionalized graphene oxide

To improve the thermal and mechanical properties of liquid silicone rubber (LSR) for application, the graphene oxide (GO) was proposed to reinforce the LSR. The GO was functionalized with triethoxyvinylsilane (TEVS) by dehydration reaction to improve the dispersion and compatibility in the matrix. The structure of the functionalized graphene oxide (TEVS‐GO) was evaluated by Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, X‐ray diffraction (XRD), and energy dispersive X‐ray spectroscopy (EDX). It was found that the TEVS was successfully grafted on the surface of GO. The TEVS‐GO/LSR composites were prepared via in situ polymerization. The structure of the composites was verified by FTIR, XRD, and scanning electron microscopy (SEM). The thermal properties of the composites were characterized by TGA and thermal conductivity. The results showed that the 10% weight loss temperature (T₁₀) increased 16.0°C with only 0.3 wt % addition of TEVS‐GO and the thermal conductivity possessed a two‐fold increase, compared to the pure LSR. Furthermore, the mechanical properties were studied and results revealed that the TEVS‐GO/LSR composites with 0.3 wt % TEVS‐GO displayed a 2.3‐fold increase in tensile strength, a 2.79‐fold enhancement in tear strength, and a 1.97‐fold reinforcement in shear strength compared with the neat LSR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42582.     

Dynamic mechanical properties of styrene‐butadiene composites reinforced by defatted soy flour and carbon black co‐filler

Carboxylated styrene‐butadiene (SB) composites reinforced by a mixture of defatted soy flour (DSF) and carbon black (CB) were investigated in terms of their dynamic mechanical properties. DSF is an abundant renewable commodity and has a lower cost than CB. DSF contains soy protein, carbohydrate, and whey. Aqueous dispersions of DSF and CB were first mixed and then blended with SB latex to form rubber composites using freeze‐drying and compression molding methods. At 140°C, a single filler composite reinforced by 30% DSF exhibited roughly a 230‐fold increase in the shear elastic modulus compared to the unfilled SB rubber, indicating a significant reinforcement effect by DSF. Mixtures of DSF and CB at three different ratios were investigated as co‐fillers. Temperature sweep experiments indicate the shear elastic moduli of the co‐filler composites are between that of DSF and CB composites. Strain sweep experiments were used to study the fatigue and recovery behaviors of these composites. Compared with the DSF composites, the recovery behaviors of the 30% co‐filler composites after the eight consecutive deformation cycles of dynamic strain were improved and similar to that of 30% CB composite. Strain sweep experiments also indicated that the co‐filler composites have a greater elastic modulus than the CB reinforced composites within the strain range measured. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Influence of grafted polypropylene on the mechanical properties of mineral‐filled polypropylene composites

The purpose of this work was to study how mineral fillers would behave in a polypropylene (PP) matrix when PP modified with maleic anhydride (MA) and/or itaconic acid (IA) was used as a coupling agent in the preparation of mineral‐filled PP composites. The composites were characterized with tensile mechanical measurements and morphological analysis. The optimum amount of the coupling agent to be used to obtain composites with improved mechanical properties was established. The results indicated that these coupling agents enhanced the tensile strength of the composites significantly, and the extent of the coupling effect depended on the nature of the interface that formed. The incorporation of coupling agents enhanced the resistance to deformation of the composite. The behavior of IA‐modified PP as a coupling agent was similar to that of a commercial MA‐modified PP for the filled PP composites. Evidence of improved interfacial bonding was revealed by scanning electron microscopy studies, which examined the surfaces of fractured tensile test specimens; their microstructures confirmed the mechanical results with respect to the observed homogeneous or optimized dispersion of the mineral‐filler phase in these composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2343–2350, 2007     

Studies on the effect of titanate coupling agent (2.0%) on the mechanical properties of flyash‐filled polybutadiene rubber

Flyash, a waste product of thermal power stations, generated in huge quantities, has been posing problems of disposal. Attempts have been made for its utilization as a filler in elastomers and plastics; however, it has been established that untreated flyash does not at all contribute in enhancing mechanical properties of composites. The purpose of this work was to make meaningful utilization of flyash as a filler, by treating it with a titanate coupling agent and to use it as a filler in PBR. The properties under consideration were tensile strength, modulus at 100 and 400%, Young's modulus, hardness, etc. Composites were made with varying proportion of untreated and treated flyash. A two‐roll mill was used for dispersing the filler in the rubber, and a compression‐molding technique was used to cure the compound in sheet form. Tensile properties were measured on a computerized UTM using an ASTM procedure. Comparison of properties of composites filled with treated and untreated flyash established that treatment of flyash imparts better reinforcing properties. Tensile strength was improved by 50%, while modulus at 400% was improved by 400%. Similarly, Young's modulus also was improved by 209%. The Titanate‐coupling agent used here has promoted adhesion between flyash and the PBR. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1293–1298, 2004     

Dielectric and microwave properties of elastomer composites loaded with carbon–silica hybrid fillers

In this study, we investigated the influence of carbon–silica dual‐phase fillers on the dielectric and microwave properties of natural‐rubber‐based composites determined in the frequency range from 1 to 12 GHz. The fillers were prepared by the impregnation of two types of carbon black with various silicasol amounts. As the results show, the fillers affected both the dielectric and microwave properties of the obtained composites. The higher the quantity of the dielectric phase (silica) in the hybrid filler was, the lower the real part of the permittivity of the composites was. This caused changes in the total, reflective, and absorptive shielding effectivenesses of the latter and their reflection and attenuation coefficients. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42978.     

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     

Dynamic properties of star‐shaped,solution‐polymerized styrene–butadiene rubber and its cocoagulated rubber‐filled with silica/carbon black

The dynamic properties, including the dynamic mechanical properties, flex fatigue properties, dynamic compression properties, and rolling loss properties, of star‐shaped solution‐polymerized styrene–butadiene rubber (SSBR) and organically modified nanosilica powder/star‐shaped styrene–butadiene rubber cocoagulated rubber (N‐SSBR), both filled with silica/carbon black (CB), were studied. N‐SSBR was characterized by ¹H‐NMR, gel permeation chromatography, energy dispersive spectrometry, and transmission electron microscopy. The results show that the silica particles were homogeneously dispersed in the N‐SSBR matrix. In addition, the N‐SSBR/SiO₂/CB–rubber compounds' high bound rubber contents implied good filler–polymer interactions. Compared with SSBR filled with silica/CB, the N‐SSBR filled with these fillers exhibited better flex fatigue resistance and a lower Payne effect, internal friction loss, compression permanent set, compression heat buildup, and power loss. The nanocomposites with excellent flex fatigue resistance showed several characteristics of branched, thick, rough, homogeneously distributed cross‐sectional cracks, tortuous flex crack paths, few stress concentration points, and obscure interfaces with the matrix. Accordingly, N‐SSBR would be an ideal matrix for applications in the tread of green tires. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40348.     

Dynamic mechanical properties of styrene‐butadiene rubber vulcanizate filled with electron beam modified surface‐treated dual‐phase filler

The influence of the electron beam modification of a dual‐phase filler on the dynamic mechanical properties of styrene‐butadiene rubber (SBR) is investigated in the presence and absence of trimethylol propane triacrylate or triethoxysilylpropyltetrasulfide. Electron beam modification of the filler results in reduction of the tan δ at 70°C, a parameter for rolling resistance, and an increase in the tan δ at 0°C, a parameter for wet skid resistance of SBR vulcanizates. These modified fillers give significantly better overall performance in comparison with the control dual‐phase filler. This variation in properties is explained in terms of filler parameters such as the filler structure that leads to rubber occlusion and filler networking. These results are further corroborated using the master curves obtained by the time–temperature superposition principle. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2992–3004, 2003     

Effects of the moisture and fiber content on the mechanical properties of biodegradable polymer–sisal fiber biocomposites

The matrix of the composites that were used in this work was a commercial blend based on starch and cellulose derivatives. The biodegradable polymer was reinforced by short‐sisal fibers with a range in fiber content of 5–15 wt %. The effects of humidity on the diffusion coefficients, equilibrium moisture content, and mechanical properties were studied. Equations obtained from microscopic mass balances for diffusion in solids were used to predict the absorbed humidity in both components (the sisal fibers and biodegradable polymer) and in the composites as a function of time. Different model predictions of the composite diffusion coefficients as a function of the filler concentration were also examined, and they were found to be in agreement with the experimental results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4007–4016, 2004     

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     

Tribological and mechanical properties of carbon‐nanofiber‐filled polytetrafluoroethylene composites

The effects of various filler concentrations (0.1, 0.5, 1, 1.5, 2, 2.5, and 3 wt %) on the tribological and mechanical properties of carbon‐nanofiber (CNF)‐filled polytetrafluoroethylene (PTFE) composites were studied. Moreover, the influence of various loads (50, 100, 150, and 200 N) and sliding velocities (0.692 and 1.39 m/s) on the friction and wear behaviors of the PTFE composites was investigated. The results showed that the friction coefficients of the PTFE composites decreased initially up to a 0.5 wt % filler concentration and then increased, whereas the antiwear properties of the PTFE composites increased by 1–2 orders of magnitude in comparison with those of pure PTFE. The composite with a 2 wt % filler concentration had the best antiwear properties under all friction conditions. The friction coefficients of the CNF/PTFE composites decreased with increases in the load and sliding velocity, whereas the wear volume loss of the PTFE composites increased. At the same time, the results also indicated that the mechanical properties of the PTFE composites increased first up to a 1 wt % filler concentration and then decreased as the filler concentration was increased above 1 wt %. In comparison with pure PTFE, the impact strength, tensile strength, and elongation to break of the PTFE composites increased by 40, 20, and 70%, respectively, at a 1 wt % filler concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2430–2437, 2007     

Mechanical properties study of micro‐ and nano‐hydroxyapatite reinforced ultrahigh molecular weight polyethylene composites

This is a comparative study between ultrahigh molecular weight polyethylene (UHMWPE) reinforced with micro‐ and nano‐hydroxyapatite (HA) under different filler content. The micro‐ and nano‐HA/UHMWPE composites were prepared by hot‐pressing method, and then compression strength, ball indentation hardness, creep resistance, friction, and wear properties were investigated. To explore mechanisms of these properties, differential scanning calorimetry, infrared spectrum, wettability, and scanning electron microscopy with energy dispersive spectrometry analysis were carried out on the samples. The results demonstrated that UHMWPE reinforced with micro‐ and nano‐HA would improve the ball indentation hardness, compression strength, creep resistance, wettability, and wear behavior. The mechanical properties for both micro‐ and nano‐HA/UHMWPE composites were comparable with pure UHMWPE. The mechanical properties of nano‐HA/UHMWPE composites are better compared with micro‐HA/UHMWPE composites and pure UHMWPE. The optimum filler quantity of micro‐ and nano‐HA/UHMWPE composites is found to be at 15 wt % and 10 wt %, separately. The micro‐ and nano‐HA/UHMWPE composites exhibit a low friction coefficient and good wear resistance at this content. The worn surface of HA/UHMWPE composites shows the wear mechanisms changed from furrow and scratch to surface rupture and delamination when the weight percent of micro‐ and nano‐HA exceed 15 wt % and 10 wt %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42869.