Role of lignin filler in stabilization of natural rubber–based composites

The stabilizing effect of a natural filler, sulfur‐free lignin, on the thermal degradation of natural rubber (NR) was examined. Lignin was incorporated into NR in amounts of 10–30 phr (parts per hundred parts of rubber). It was shown that the lignin preparation used improved the physicomechanical properties of the rubber vulcanizates. Thermogravimetric analysis and differential scanning calorimetry were used to study the thermal degradation of unfilled and lignin‐filled vulcanized natural rubber. Measurements were carried out under atmospheric conditions. It was revealed that lignin used as filler increased the resistance of NR vulcanizates to thermooxidative degradation in air. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1226–1231, 2007     

Tire rubber–sisal composites: Effect of mercerization and acetylation on reinforcement

Tire rubber particles were mixed randomly with short sisal fibers and hot pressed. Sisal fibers were used as received, mercerized, and mercerized/acetylated. The fibers were characterized by scanning electron microscopy (SEM), thermal gravimetry analysis (TGA), infrared spectroscopy (FTIR), water sorption, and mechanical properties. Thermal stability of the mercerized/acetylated fibers improves (from 200 to 300°C) with respect to the raw fibers, and water sorption is ～ 20% smaller than for the raw and the mercerized fibers. Tensile strength is unchanged after the chemical treatments. Water sorption, mechanical properties, and SEM evaluated the performance of the tire rubber composites. All composites showed enhanced elastic modulus; increase is dependent on fiber load. Smallest water sorption was obtained in composites with the mercerized/acetylated fibers. With these fibers at 10% load, the best results were obtained with the smaller tire rubber particles (320 μm) and at 5% load with the bigger (740 μm) tire rubber particles. Both composites showed ～ 50% increase in tensile strength when compared to similar composites with raw fibers. SEM of the surface of fracture showed that the adhesion between fiber and rubber was enhanced after both chemical treatments. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2507–2515, 2003     

Electrical conductivity and EMI shielding effectiveness of polyurethane foam–conductive filler composites

The morphological, electrical, and thermal properties of polyurethane foam (PUF)/single conductive filler composites and PUF/hybrid conductive filler composites were investigated. For the PUF/single conductive filler composites, the PUF/nickel‐coated carbon fiber (NCCF) composite showed higher electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) than did the PUF/multiwall carbon nanotube (MWCNT) and PUF/graphite composites; therefore, NCCF is the most effective filler among those tested in this study. For the PUF/hybrid conductive fillers PUF/NCCF (3.0 php)/MWCNT (3.0 php) composites, the values of electrical conductivity and EMI SE were determined to be 0.171 S/cm and 24.7 dB (decibel), respectively, which were the highest among the fillers investigated in this study. NCCF and MWCNT were the most effective primary and secondary fillers, and they had a synergistic effect on the electrical conductivity and EMI SE of the PUF/NCCF/MWCNT composites. From the results of thermal conductivity and cell size of the PUF/conductive filler composites, it is suggested that a reduction in cell size lowers the thermal conductivity of the PUF/conductive filler composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44373.     

The behavior of natural rubber–epoxidized natural rubber–silica composites based on wet masterbatch technique

Natural rubber–epoxidized natural rubber–silica composites were prepared by the wet masterbatch technique and the traditional dry mixing method. Performances of the composites based on different preparation methods were investigated with a moving die rheometer, an electronic universal testing machine, a dynamic mechanical analyzer, a nuclear magnetic resonance crosslink density analyzer, a rubber processing analyzer (RPA), a scanning electron microscope (SEM), and a transmission electron microscope (TEM). The RPA, SEM, and TEM analyses indicated that silica has better dispersion, lower filler–filler interaction, and better filler–rubber interaction in compounds based on the wet masterbatch technique, leading to improvements in mechanical strength and the dynamic mechanical and compression properties of the composites. It also indicates that composites prepared by the wet masterbatch technique have shorter scorch time, faster curing velocity, and higher crosslink density. The composites prepared by the wet materbatch technique also have lower rolling resistance, which is an important property for their use as a green material for the tire industry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43571.     

Polymer–filler interaction in polyurethane kraft lignin polyblends

Kraft lignin fillers have been shown to enhance the mechanical characteristics of different types of polymeric-based sealants; however, the mechanism for reinforcement and the degree of interaction was not well understood. In this study, interactions between a polyurethane-based elastomer and various Kraft lignin fillers as well as kaolin and titanium dioxide filler combinations were investigated in an effort to determine the most useful elastomer–filler combination for use as a construction joint sealant. A relationship that describes and relates the characteristics of polymer–filler interaction requires that the surface-energy properties of both the polymer matrix and the filler be determined. Measurements using the sessile drop method are used to evaluate the critical surface energy of the polymer matrix, whereas the rate of rise of a liquid through a bed of filler provides the means to evaluate the surface energetics of the various fillers. Results obtained from this study show that the tensile modulus of the different elastomer formulations are proportional to the equilibrium work of adhesion, as described by the relationship derived by Lee that relates the degree of interaction of the formulation components and the mechanical properties of the blends. © 1994 John Wiley & Sons, Inc.     

Diels–Alder‐based crosslinked self‐healing polyurethane/urea from polymeric methylene diphenyl diisocyanate

Crosslinked self‐healing polyurethane/urea based on a Diels–Alder reaction (C‐PMPU–DA) was synthesized from a multiple‐furan monomer and a commercial bismaleimide. The multiple‐furan monomer (PMPU–furan) was obtained from a functionalized prepolymer (polymeric MDI: PBA‐2000 = 2:1) by furfuryl amine. The structures of both the PMPU–furan and C‐PMPU–DA were characterized by attenuated total reflectance (ATR)–Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and ¹H‐NMR. The Diels–Alder bonds enabled C‐PMPU–DA thermal reversibility, which was investigated by ATR–FTIR spectroscopy, ¹H‐NMR, gel–solution–gel experiments, and viscosity tests. Meanwhile, the self‐healing properties of C‐PMPU–DA were also investigated by the recovery of the mechanical properties. The results showed that C‐PMPU–DA exhibited good thermal reversibility and self‐healing properties. C‐PMPU–DA exhibited thermosetting properties at room temperature, although it exhibited thermoplastic properties at higher temperatures and may find applications in self‐healing materials, recyclable materials, or removable materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40234.     

Intercalation process and rubber–filler interactions of polybutadiene rubber/organoclay nanocomposites

The intercalation process and microstructural development of polybutadiene rubber (BR)/clay nanocomposites cured with sulfur were systematically investigated with respect to the organic modifier (primary and quaternary ammonium compounds) of the clay. X‐ray diffraction spectra were recorded at various stages of processing to obtain information about the intercalation process. The rubber–filler interactions was examined on the basis of the surface free energy, stress‐softening effect, and crystallization behavior. A well‐ordered intercalated structure was obtained in the primary ammonium modified clay (P‐OMMT) and quaternary ammonium modified clay (Q‐OMMT) filled with BR composite. The BR/Q‐OMMT composites showed higher mechanical properties and higher hysteresis under tension and lower crystallization abilities than the BR/P‐OMMT composites. The results also show that higher interfacial interactions existed between Q‐OMMT and BR than between P‐OMMT and BR. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Properties of crosslinked casein/waterborne polyurethane composites

Waterborne polyurethane (WPU) and casein (1 : 1 by weight) were blended at 90°C for 30 min, and then were crosslinked by adding 1–10 wt % ethanedial to prepare a series of sheets. Their structure and properties were characterized by using infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical analysis, and tensile testing. The results indicated that crosslinked blend sheets exhibited a certain degree of miscibility, and exhibited much higher tensile strength and water resistivity than did the WPU, casein, and the uncrosslinked blend from WPU and casein. When the ethanedial content was 2 wt %, the tensile strength and elongation at break of crosslinked sheets achieved 19.5 MPa and 148% in the dry state, and 5.0 MPa and 175% in the wet state, respectively. A 2 wt % content of ethanedial plays an important role in the enhancement of mechanical properties, thermal stability, and water resistivity of the blends of WPU and casein as a result of intermolecular crosslinking. This work provided a new protein plastic with good water resistivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 332–338, 2004     

Effect of bonding agents on styrene butadiene rubber–aluminum powder composites

Effects of various bonding agents—such as the hexamethylene tetramine–resorcinol system (HR), bis[3‐ (triethoxysilyl) propyl] tetra sulfide (Si‐69), and cobalt naphthenate (CoN)—on the mechanical properties of aluminum powder filled styrene butadiene rubber composites were studied, giving emphasis on concentration of bonding agent and loading of aluminum powder. Shore A hardness, modulus, tensile strength, tear strength, heat buildup, etc., were increased by the loading of aluminum powder, and the presence of bonding agents again increased these properties. Rebound resilience and elongation at break were decreased by the addition of aluminum powder. Equilibrium swelling studies showed an improved adhesion between aluminum powder and styrene butadiene rubber (SBR) in presence of bonding agents. Among the various bonding agents used in this study, silane coupling agent (Si‐69) and hexamethylene tetramine–resorcinol (HR) system were found to be better for aluminum powder filled SBR vulcanizates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 519–529, 2002     

The influence of montmorillonite on the anti‐reversion in the rubber–clay composites

The influence of organically modified montmorillonate (OMMT) on the curing reversion of natural rubber (NR) and polychloroprene rubber (CR) blend has been demonstrated in this article. Characteristics of the NR/CR/OMMT hybrid composite were undertaken by combining the cure kinetics, thermal stability, and the detection of phase morphology. Compared to the neat rubber blend, thermal gravity analysis has shown improved thermal stability results during degradation for the nanofiller filled ones. Differential scanning calorimetry study has offered cure kinetic results; among which blending with NR has lifted the cure activation temperature of CR low toward. Meanwhile, transmission electron microscopy has shown the intercalation and immobilization of OMMT in the CR phase formed a barrier to NR phase. In addition, to discover the reversion source, infrared spectroscopy has been applied to trace the oxygenic function units in the neat NR vulcanizate. All of the experimental results and related analysis has offered us the base to explain the improvement of the anti‐reversion of the rubber blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Slightly crosslinked polyurethane with Diels–Alder adducts from trimethylolpropane

Diels–Alder (DA) reactions between furan and maleimide have been widely applied in thermally remendable polymeric materials. Crosslinked polyurethane with DA adducts exhibited much better mechanical properties than linear polyurethane with DA adducts. However, the highly crosslinked polyurethane needs a higher temperature and a longer healing time. This will increase the possibility of side reactions proceeding during the healing procedure. In this paper, slightly crosslinked polyurethane with DA adducts was synthesized by incorporating trimethylolpropane into linear polyurethane with DA adducts. The structure of the intermediate and final products was characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, and differential scanning calorimetry, confirming that the synthesizing process proceeded successfully. The images from the polarizing optical microscope demonstrated that the final product with slight crosslinking needed less time and a lower healing temperature to complete the healing procedure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43971.     

Temperature dependence of the tensile strength of glass fiber–epoxy and glass fiber–unsaturated polyester composites

Epoxy and unsaturated polyester resins reinforced with random-planar orientation of short glass fibers were prepared and the temperature dependence of their tensile strength was studied. The tensile strength decreases as the temperature increases, and this tendency can be expressed in terms of critical fiber length l_c and apparent interfacial shear strength τ: where σ_cs is the tensile strength of composite reinforced with random-planar orientation of short fibers, L is the fiber length, d is the fiber diameter, σ_f is the tensile strength of fiber, σ_m is the tensile strength of matrix, u_f is the volume fraction of fiber, v_m is the volume fraction of matrix, and σ′_m is the stress of the matrix at fracture strain of the composite. The experimental strength values at room temperature are considerably smaller than the theoretical values, and this difference can be explained by the thermal stress produced during molding due to the large difference in the thermal expansion coefficient between glass fiber and matrix resin.     

Effect of zeolite particulate filler on the properties of polyurethane composites

Polymer-Zeolites composites have been prepared, using castor oil based polyurethane (PU) as a host and AlPO₄-5 as particulate filler. The prepared PU/zeolite composites have been characterized for mechanical properties such as tensile strength and tensile modulus. These PU composites exhibited an improved mechanical performance compared to the unfilled PU. Thermo gravimetric analyzer (TGA) curve shows that all the chain-extended PUs are stable up to 250 °C and maximum weight loss occurs at 490 °C. The thermal stability of composites increases with increase in zeolite content. Microcrystalline parameters and micro voids of composites have been measured by using wide-angle X-ray scattering (WAXS) and Positron Annihilation Lifetime (PALS) methods respectively. The microcrystalline parameters and micro-voids from PALS indicate the interaction of the filler with the matrix is stronger beyond 5% of the filler which reflect the mechanical performance as well. Surface morphology of composites has been studied using Scanning Electron Microscopy (SEM). The photomicrograph of SEM indicates a uniform distribution of zeolite filler in the PU matrix.     

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     

Gas permeability of crosslinked HTPB–H12MDI-based polyurethane membrane

Crosslinked membranes were prepared by the addition of a crosslinking agent of benzoyl peroxide (BPO) to the hydroxyl-terminated polybutadiene (HTPB) and 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI)-based polyurethane (PU) solutions. The stress–strain properties of segmented HTP-B based PUs were changed by the crosslinking between soft–soft segments. The gas permeabilities of HTPB-based PU membranes with a suitable amount of crosslinking agent were higher than those of uncrosslinked membranes, which is due to the stretched and extended soft-segment molecular chains. The reproducibility of gas permeability was improved by the crosslinked membranes. Thermal stability conducted by TGA was increased with increasing crosslinking agent content. FTIR was utilized to identify the segregation between hard and soft segments and structure change, which affects the gas-transport properties. The change of glass transition temperature was detected by DSC, which can be used to manifest the degree of crosslinking of these membranes. The results of TGA, FTIR, and DSC measurements explain the crosslinking degree with different BPO content and, hence, the gas permeabilities as well. © 1995 John Wiley & Sons, Inc.     

Microwave dielectric properties of flexible butyl rubber–strontium cerium titanate composites

Butyl rubber–strontium cerium titanate (BS) composites have been prepared by hot pressing. The tensile tests show that the BS composites are flexible. The dielectric properties of the composites have been investigated at 1 MHz and 5 GHz as a function of ceramic contents. The composite with volume fraction 0.43 of ceramic filler has a dielectric constant (ε_r) of 11.9 and dielectric loss (tan δ) 1.8 × 10^?3 at 5 GHz. The measured values of ε_r are compared with the effective values calculated using different theoretical models. The thermal conductivity of the composites is found to increase with ceramic contents and reaches a value of 4.5 Wm^?1 K^?1 for maximum filler loading 0.43 volume fraction. The coefficient of thermal expansion of the composites decreases gradually with filler loading and reaches a minimum value of 30.2 ppm °C^?1 at a volume fraction 0.43. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Bitumen–silica model composites: The role of the filler

The storage moduli of bitumen–silica model composites obey a simple relationship: E′ = E′₀ + A?ψ, where ? is the filler volume ratio and ψ the bitumen–silica interfacial area for a unit volume of composite. This equation is experimentally varified taking various silicas of different surface areas or chemical surface reactivity. The influence of the interface properties on the mechanical glass transition temperature is also examined.     

Effect of reinforcement on the barrier and dielectric properties of epoxidized natural rubber–graphene nanocomposites

The influence of epoxidation level of natural rubber (i.e., ENR25, ENR50) on the dielectric and oxygen gas barrier properties of thermally reduced graphene oxide (GR) and graphite (GT) (with 2%·w/w) filled nanocomposites are investigated here. GR, GT filled epoxidized natural rubber (ENR) nanocomposites were fabricated by mechanical mixing using environment friendly two‐roll mill mixing method. Raman spectroscopy and Fourier transform infrared spectroscopy studies were carried out to investigate the extent of chemical interactions between GR and ENR. Morphological studies were done using transmission electron microscopy to evaluate the distribution of GR and GT in the ENR. The improved gas barrier and dielectric properties of GT‐ENR and GR–ENR composites synthesized by a novel green ecofriendly method is correlated with the chemical interactions among GT, GR, and ENR. POLYM. ENG. SCI., 55:2439–2447, 2015. © 2015 Society of Plastics Engineers     

Study of rubber‐filled cementitious composites

A possible method for recycling automobile and truck tires is to comminute them and incorporate the rubber particles in to cementitious mixtures for nonstructural applications. It was found that addition of rubber granules led to a decrease in compressive and flexural strengths of the mortar. The fracture behavior of cementitious paste containing untreated rubber particles showed particulate pull out characteristics and weak interface. The interfacial strength of rubber‐cementitious composite can be improved upon chemical treatment of rubber by gamma mercapto trimethoxy silane coupling agent (GMPTS). The extent of interfacial bonding of rubber and cement was measured by peel strength analysis. The increased interfacial strength of the composite was found to play an important role in the ability of the composite to withstand postpeak loading and postpeak displacement. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 934–942, 2000