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     

Effect of processing conditions on dimensions of sisal fibers in thermoplastic biodegradable composites

Biodegradable composites based on treated and untreated sisal fiber and mater Bi‐Z were processed using an internal batch mixer. The effect of processing conditions (temperature, speed of rotation, and time of mixing) and alkaline treatment on the dimensions of sisal fiber was studied. The length and diameter of the initial fibers were reduced during mixing and this effect was correlated to the magnitude of the shear stress developed in the mixer. An increase of the speed of rotation and/or a reduction of temperature produced fibers of smaller dimensions but with a higher aspect ratio l/d. Alkaline treatment increased the kinetics associated to the reduction of the fiber's dimensions. A semiempirical model was employed to predict the size of the fibers versus the time of mixing. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1084–1091, 2001     

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.     

Resol–vegetable fibers composites

Vegetable fibers like cotton, sisal, and sugar cane bagasse have been used as reinforcement in a polymeric matrix. Because of its low cost and affinity with lignocellulosic fibers, a phenol‐formaldehyde resin —resol— was selected as the matrix. Composites were prepared by compression molding. The influence of fiber volume fraction‐V_f‐in flexural properties and density of composites has been studied. Cotton and sugar cane bagasse composites present a V_f value at which flexural strength and modulus are maxima. However, sisal composites show a continuous rise in flexural strength and modulus as fiber volume fraction increases, up to 76%, which is the highest concentration studied. Composites made with raw cotton show the highest values of strength and stiffness. The actual density of composites is always lower than theoretical density, due to the presence of voids. Scanning Electron Microscopy reveals a good adhesion between fiber and matrix in the composites. In addition, the flexural properties were analyzed with an efficiency criterion, which relates strength and stiffness with density, and the values obtained were compared with those corresponding to typical structural materials. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1832–1840, 2000     

Development and molecular dynamics simulation of green natural rubber composites with modified sisal microcrystalline cellulose

In this study, green composites were prepared using natural rubber (NR) as the matrix and the sisal microcrystalline cellulose (MCC) as the filler. Three modifying agents oleic acid (OA), γ-aminopropyltriethoxylsilane (KH550), and bis-γ-(triethoxysilylpropyl)-tetrasulfide (Si69) were individually tested to modify the MCC to improve the interfacial compatibility of the NR and MCC. Combined with modern instrumental analysis technology and molecular dynamics simulation, the reinforcing effect and microscopic mechanism of modified MCC on NR were analyzed. The structure–activity relationship of NR and MCC composites was further revealed, and the interaction between the two components was clarified. At the same time, the reinforcing and compatibilizing effect of three kinds of modified MCC in NR matrix were also revealed. The results showed that the properties of NR/Mod-MCC composites were better than those of NR/MCC composites, where NR/OA-MCC presented the highest tensile strength, followed by NR/Si69-MCC. In addition, NR/Si69-MCC exhibited higher elongation at break and NR/KH550-MCC exhibited higher vulcanization characteristics. Molecular model systems were constructed through molecular dynamics simulation to investigate the interactions between the three modified cellulose molecules and the NR molecules. OA-cellulose has a better interaction with NR than KH550-cellulose and Si69-cellulose, The simulation results were consistent with the experimental results.     

Preparation and characterization of benzylated sisal fibers

Sisal fibers were benzylated under different conditions and were characterized with infrared spectroscopy, X‐ray diffraction, thermal analysis, and scanning electron microscopy. The benzylation reaction was monitored by the mass gain as a function of the reaction time. In the first stage, there was a mass loss associated with the loss of lignin and polyoses from the raw fiber, which was accompanied by an increase in mass due to benzyl incorporation. When fiber delignification was carried out before benzylation, the mass gain curves of the benzylation reaction presented no initial mass loss and a much higher mass gain. Benzylation promoted several morphological changes: (1) the loss of the parenchyma cells, (2) the defibrillation of the technical fibers into ultimate fibers, (3) the microdefibrillation of the ultimate fibers, and (4) benzyl incorporation. The crystallinity of the fibers decreased with benzylation, as observed by X‐ray diffraction. The thermal stability of the fibers varied according to the treatment used. Other changes promoted in the fibers by chemical modification were examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2957–2965, 2003     

Preparation and characterization of EVA–sisal fiber composites

In this work, composites of an EVA polymer matrix and short sisal fiber were characterized. The physical‐morphological as well as chemical interactions between EVA and sisal were investigated. When the samples were prepared in the presence of dicumyl peroxide, the results suggest that crosslinking of EVA as well as grafting between EVA and the sisal fibers took place. Morphological changes were studied by scanning electron microscopy (SEM). Results from Hg‐porosimetry, SEM, Fourier transform infrared spectroscopy, surface free energy, and gel content strongly indicate grafting of EVA onto sisal under the composite preparation conditions, even in the absence of peroxide. The grafting mechanism could not be confirmed from solid‐state ¹³C NMR analysis. The grafting had an impact on the thermal and mechanical properties of the composites, as determined by differential scanning calorimetry and tensile testing. Thermogravimetric analysis results show that the composites are more stable than both EVA and sisal fiber alone. The composite stability, however, decreases with increasing fiber content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1607–1617, 2006     

Preparation,characterization, and biodegradability of renewable resource‐based composites from recycled polylactide bioplastic and sisal fibers

The biodegradability, morphology, and mechanical thermal properties of composite materials composed of polylactide (PLA) and sisal fibers (SFs) were evaluated. Composites containing acrylic acid‐grafted PLA (PLA‐g‐AA/SF) exhibited noticeably superior mechanical properties because of greater compatibility between the two components. The dispersion of SF in the PLA‐g‐AA matrix was highly homogeneous as a result of ester formation and the consequent creation of branched and crosslinked macromolecules between the carboxyl groups of PLA‐g‐AA and hydroxyl groups in SF. Furthermore, with a lower melt temperature, the PLA‐g‐AA/SF composite is more readily processed than PLA/SF. Both composites were buried in soil to assess biodegradability. Both the PLA and the PLA‐g‐AA/SF composite films were eventually completely degraded, and severe disruption of film structure was observed after 6–10 weeks of incubation. Although the degree of weight loss after burial indicated that both materials were biodegradable even with high levels of SF, the higher water resistance of PLA‐g‐AA/SF films indicates that they were more biodegradable than those made of PLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of hybridization and chemical modification on the water‐absorption behavior of banana fiber–reinforced polyester composites

The water sorption characteristics of banana fiber–reinforced polyester composites were studied by immersion in distilled water at 28, 50, 70, and 90°C. The effect of hybridization with glass fiber and the chemical modification of the fiber on the water absorption properties of the prepared composites were also evaluated. In the case of hybrid composites, water uptake decreased with increase of glass fiber content. In the case of chemically modified fiber composites, water uptake was found to be dependent on the chemical treatment done on the fiber surface. Weight change profiles of the composites at higher temperature indicated that the diffusion is close to Fickian. The water absorption showed a multistage mechanism in all cases at lower temperatures. Chemical modification was found to affect the water uptake of the composite. Among the treated composites the lowest water uptake was observed for composites treated with silane A1100. Finally, parameters like diffusion, sorption, and permeability coefficients were determined. It was observed that equilibrium water uptake is dependent on the nature of the composite and temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3856–3865, 2004     

Green composites using switchgrass as a reinforcement for a conjugated linseed oil‐based resin

Switchgrass (SWG) has been used as a filler to produce conjugated linseed oil‐based green composites. The effect of the amount of the SWG; the matrix crosslink density; and the incorporation of a compatibilizer, maleic anhydride (MA), on the structure, water absorption, and thermal and mechanical properties of the composites has been investigated. The thermal stability of the composites is primarily dependent on the amount of the SWG fibers, which are far less thermally stable than the linseed oil‐based resin. For the most part, improvements in the mechanical properties can be achieved by increasing the amount of SWG (up to 70 wt %), increasing the amount of the crosslinker, and adding MA to increase the filler–matrix interaction. The uptake of water in the composites is mostly influenced by the loading of the SWG fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of fiber volume fraction and aspect ratio in resol–sisal composites

Vegetable fibers are being used as reinforcements in polymeric matrices with a wide variety of applications. Among these fibers, sisal is of particular interest due to the high impact strength and moderate tensile and flexural properties of its derivated composites. Because of its low cost and affinity, a phenol–formaldehyde resin, resol, has been selected as the matrix to obtain resol–sisal composites. The influence of fiber length and volume fraction on flexural properties has been studied. An optimum for the fiber length as well as for the fiber volume fraction was found. The improvement of the properties occurred up to a length of about 23 mm. The use of longer fibers lead to reduced properties because they tended to curl and bend during processing. Besides, actual composite densities were lower than theoretical ones mainly due to the presence of voids. This undesirable porosity produced a reduction in flexural properties at high fiber contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2714–2722, 2003     

Wood–polymer composites prepared by the in situ polymerization of monomers within wood

Wood–polymer composites (WPCs) were prepared from poplar wood (P. ussuriensis Komarov) in a two‐step procedure. Maleic anhydride (MAN) was first dissolved in acetone and impregnated into wood; this was followed by a heat process; and then, glycidyl methacrylate (GMA) and styrene (St) were further impregnated into the MAN‐treated wood, followed by a second thermal treatment. Finally, the novel WPC was fabricated. The reactions occurring in the WPC, the aggregation of the resulting polymers, and their interaction with the wood substrate were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and dynamic mechanical analysis. The performance of WPC was also evaluated in terms of the mechanical properties and durability, which were then correlated with the structural analysis of the WPC. The test results show that MAN and GMA/St chemically reacted with the wood cell walls in sequence, and the quantity of hydroxyl groups in the wood cell walls was evidently reduced. Meanwhile, St copolymerized with GMA or MAN, and the resulting polymers mainly filled in the wood cell lumen in an amorphous form, tightly contacting the wood cell walls without noticeable gaps. As a result, the mechanical properties, decay resistance, and dimensional stability of the WPC were remarkably improved over those of the untreated wood, and its glass‐transition temperature also increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Phenol–furfural resins to elaborate composites reinforced with sisal fibers—Molecular analysis of resin and properties of composites

Resol type resins were prepared in alkaline conditions (potassium hydroxide or potassium carbonate) using furfural obtained by acid hydrolysis of abundant renewable resources from agricultural and forestry waste residues. The structures of the resins were fully determined by ¹H, ¹³C, and 2D NMR spectrometries with the help of four models compounds synthesized specially for this study. MALDI‐Tof mass spectrometry experiments indicated that a majority of linear oligomers and a minority of cyclic ones constituted them. Composites were prepared with furfural–phenol resins and sisal fibers. These fibers were chosen mainly because they came from natural lignocellulosic material and they presented excellent mechanical properties. Thermal analyses (dTG and DSC) and electron microscopy images indicated that the composites displayed excellent adhesion between resin and fibers. Impact strength measurement showed that mild conditions were more suitable to prepare thermosets. Nevertheless, mild conditions induced a high‐diffusion coefficient for water absorption by composites. Composites with good properties could be prepared using high proportion of materials obtained from biomass without formaldehyde. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal and scanning electron microscopy/energy‐dispersive spectroscopy analysis of styrene–butadiene rubber–butadiene rubber/silicon dioxide and styrene–butadiene rubber–butadiene rubber/carbon black–silicon dioxide composites

Silica as a reinforcement filler for automotive tires is used to reduce the friction between precured treads and roads. This results in lower fuel consumption and reduced emissions of pollutant gases. In this work, the existing physical interactions between the filler and elastomer were analyzed through the extraction of the sol phase of styrene–butadiene rubber (SBR)–butadiene rubber (BR)/SiO₂ composites. The extraction of the sol phase from samples filled with carbon black was also studied. The activation energy (E_a) was calculated from differential thermogravimetry curves obtained during pyrolysis analysis. For the SBR–BR blend, E_a was 315 kJ/mol. The values obtained for the composites containing 20 and 30 parts of silica per hundred parts of rubber were 231 and 197 kJ/mol, respectively. These results indicated an increasing filler–filler interaction, instead of filler–polymer interactions, with respect to the more charged composite. A microscopic analysis with energy‐dispersive spectroscopy showed silica agglomerates and matched the decreasing E_a values for the SBR–BR/30SiO₂ composite well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2273–2279, 2005     

Effect of coprecipitated barium ferrite on the cure characteristics and dynamic properties of natural rubber–ferrite composites around percolation

The influence of coprecipitated hexagonal barium ferrite BaFe₁₂O₁₉ phase on the cure characteristics and dynamic properties of natural rubber–ferrite composites has been studied as a function of ferrite loading up to 220 phr (part per hundred part of rubber). Unusual characteristics of coprecipitated ferrite particles were discovered by scanning electron microscope. The results show that scorch time t₁₀ and cure time t₉₀ decrease dramatically with increasing ferrite content up to critical ferrite loading. After 160 phr, t₉₀ increases sharply with increasing ferrite content, in contrast to saturation of t₁₀. Minimum torque recorded normal behavior at low ferrite loading, whereas it decreases with increasing ferrite content at high ferrite loading because of dilution effects. The storage modulus E′ and loss modulus E″ decrease with increasing temperature. The loss tangents (tanδ) of the composites are greater than those of the pure rubber. Linear viscoelastic behavior was observed as a result of the homogeneity and compatibility of the composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

剑麻纤维及其复合材料研究进展

介绍了剑麻纤维(SF)的结构特点、物理力学性能以及纤维改性处理方法,从纤维形态及增强基质出发综述了长、短SF及SF混杂纤维增强复合材料以及SF增强热塑性、热固性树脂和弹性体复合材料方面的研究与开发,指出了SF增强复合材料今后的研究方向。     

Thermal and mechanical properties of LDPE/sisal fiber composites compatibilized with functionalized paraffin waxes

The effect of maleic anhydride‐grafted hard paraffin wax (MA‐g‐wax) and oxidized hard paraffin wax (OxWax), as possible compatibilizers, on the morphology, thermal and mechanical properties of LDPE/sisal fiber composites were examined. The differential scanning calorimetry (DSC) results show that sisal alone did not change the crystallization behavior of LDPE, while the two waxes influenced the crystallization behavior of LDPE in different ways, whether mixed with LDPE alone or in the presence of sisal. The thermal properties seem to be influenced by the fact that the waxes preferably crystallize around the short sisal fibers, and by the fact that the two waxes have different compatibilities with LDPE. The TGA results show an increase in the thermal stability of the blends in the presence of the two waxes, with LDPE/OxWax showing a more significant improvement. The presence of wax, however, reduced the thermal stability of the LDPE/sisal/wax composites. The presence of OxWax and MA‐g‐wax similarly influenced the tensile properties of the composites. Both waxes similarly improved the modulus of the compatibilized composites, but in both cases the tensile strengths were worse, probably because of a fairly weak interaction between LDPE and the respective waxes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Preparation and properties of acrylonitrile–butadiene rubber–graphene nanocomposites

The graphene oxide (GO) was prepared by sonication‐induced exfoliation from graphite oxide, which was produced by oxidation from graphite flakes with a modified Hummer's method. The GO was then treated by hydrazine to obtain reduced graphene oxide (rGO). On the basis of the characterization results, the GO was successfully reduced to rGO. Acrylonitrile–butadiene rubber (NBR)–GO and NBR–rGO composites were prepared via a solution‐mixing method, and their various physical properties were investigated. The NBR–rGO nanocomposite demonstrated a higher curing efficiency and a change in torque compared to the gum and NBR–GO compounds. This agreed well with the crosslinking density measured by swelling. The results manifested in the high hardness (Shore A) and high tensile modulus of the NBR–rGO compounds. For instance, the tensile modulus at a 0.1‐phr rGO loading greatly increased above 83, 114, and 116% at strain levels of 50, 100, and 200%, respectively, compared to the 0.1‐phr GO loaded sample. The observed enhancement was highly attributed to a homogeneous dispersion of rGO within the NBR matrix; this was confirmed by scanning electron microscopy and transmission electron microscopy analysis. However, in view of the high ultimate tensile strength, the NBR–GO compounds exhibited an advantage; this was presumably due to strong hydrogen bonding or polar–polar interactions between the NBR and GO sheets. This interfacial interaction between GO and NBR was supported by the marginal increase in the glass‐transition temperatures of the NBR compounds containing fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42457.