Effect of particulate fillers on short jute fiber-reinforced natural rubber composites

The effect of carbon black on the processing characteristics and physical properties of jute fiber-reinforced composites and the role of silica and carbon black in promoting the adhesion between jute fiber and natural rubber have been studied. It was found that presence of silica is not essential to develop adhesion between fiber and rubber in the presence of carbon black. However, silica and carbon black can improve adhesion by minimizing the resin formation and controlling it to a low molecular weight species. Processing properties like green strength and mill shrinkage are improved by the addition of fiber. Carbon black does not affect mill shrinkage, but improves the green strength. Breakage of jute fiber during mixing is severe, but the extent of breakage is not affected by the presence of carbon black. The minimum loading of fiber to achieve reinforcement is reduced in the presence of carbon black. It was also found that the presence of clay in jute fiber rubber composites impairs the properties. Scanning electron microscopy (SEM) has been used to assess the failure criteria.     

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.     

表面处理对玻纤/碳纤增强橡胶基密封复合材料性能的影响

采用压延成张工艺制备碳纤维和玻璃纤维混杂增强非石棉橡胶基密封复合材料(NAFC),以横向抗拉强度作为表征混杂增强橡胶基密封材料中纤维与橡胶界面粘结性能的指标.通过扫描电镜(SEM)对材料横向拉伸试样断口进行形貌分析,及对材料的耐油、耐酸、耐碱性能进行测试,探讨了不同表面处理工艺对纤维与基体界面粘结效果的影响.研究结果表明,对玻璃纤维采用偶联剂KH-550浸渍后涂覆环氧树脂涂层,对碳纤维在空气氧化后涂覆环氧树脂涂层,可有效增强纤维、基体的界面粘结,所制得的混杂纤维增强复合材料具有较好的机械性能和耐介质性能.     

表面处理对可生物降解黄麻/PLA复合材料结构和性能的影响

采用注塑成型法制备了生物降解黄麻短纤维增强PLA复合材料,通过力学性能测试及SEM,探讨了碱处理、碱和硅烷偶联剂KH550同时处理对复合材料结构和性能的影响。结果表明:两种处理方法均能够增加黄麻纤维的表面粗糙度,但碱和偶联剂KH550同时处理的效果要优于碱处理,且KH550改善了黄麻短纤维与PLA树脂之间的界面黏结性能提,高了黄麻/PLA复合材料的拉伸强度和弯曲强度。     

Fracture behavior of vinylester resin matrix composites reinforced with alkali‐treated jute fibers

Jute fibers were treated with 5% NaOH solution for 4 and 8 h, respectively, to study the mechanical and impact fatigue properties of jute‐reinforced vinylester resin matrix composites. Mechanical properties were enhanced in case of fiber composites treated for 4 h, where improved interfacial bonding (as evident from scanning electron microscopy [SEM]) and increased fiber strength properties contributed effectively in load transfer from the matrix to the fiber; but their superior mechanical property was not retained with fatigue, as they showed poor impact fatigue behavior. The fracture surfaces produced under a three‐point bend test and repeated impact loading were examined under SEM to study the nature of failure in the composites. In case of untreated fiber composites, interfacial debonding and extensive fiber pullout were observed, which lowered the mechanical property of the composites but improved their impact fatigue behavior. In composites treated for 4 h under repeated impact loading, interfacial debonding occurred, followed by fiber breakage, producing a sawlike structure at the fracture surface, which lowered the fatigue resistance property of the composites. The composites with fibers treated with alkali for 8 h showed maximum impact fatigue resistance. Here, interfacial debonding was at a minimum, and the fibers, being much stronger and stiffer owing to their increased crystallinity, suffered catastrophic fracture along with some microfibrillar pullout (as evident from the SEM micrographs), absorbing a lot of energy in the process, which increased the fatigue resistance property of the composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2588–2593, 2002     

Analysis of the Jute/glass fiber reinforced hybrid composites using combined radial basis function method

In this paper, jute/glass fiber reinforced hybrid composites plates have been prepared in the laboratory at different percentage of the jute and glass fibers. Jute has been taken in fabric form and short glass fiber has been distributed randomly. Tensile, flexural properties, and phase morphology were studied experimentally at different percentage of the jute and glass fibers. Deflection and damping behavior of the composites has been analyzed using meshless combined radial basis function method. Thermal analysis of the jute/glass fiber reinforced hybrid composites at various temperature ranges has also been performed. Here, combined radial basis function is used for spatial discretization and Newmark implicit method is used for temporal discretization. The obtained results from this method are compared with analytical methods. POLYM. COMPOS., 38:1890–1901, 2017. © 2015 Society of Plastics Engineers     

Overall properties of fibrillar silicate/styrene–butadiene rubber nanocomposites

The mechanical properties, heat aging resistance, dynamic properties, and abrasion resistance of fibrillar silicate (FS)/styrene butadiene rubber (SBR) nanocomposites are discussed in detail. Compared with white carbon black (WCB)/SBR composites, FS/SBR composites exhibit higher tensile stress at definite strain, higher tear strength, and lower elongation at break but poor abrasion resistance and tensile strength. Surprisingly, FS/SBR compounds have better flow properties. This is because by rubber melt blending modified FS can be separated into numerous nanosized fibrils under mechanical shear. Moreover, the composites show visible anisotropy due to the orientation of nanofibrils. There is potential for FS to be used to some extent as a reinforcing agent for rubber instead of short microfibers or white carbon black. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2725–2731, 2006     

Preparation and properties of successive alkali treated completely biodegradable short jute fiber reinforced PLA composites

The natural fiber reinforced biodegradable polymer composites were prepared with short jute fiber as reinforcement in PLA (Poly lactic acid) matrix. The short jute fiber is successively treated with NaOH at various concentrations (5%, 10%, and 15%) and H₂O₂. The composites were prepared with untreated and treated short jute fibers at different weight proportions (up to 25%) in PLA and investigated for mechanical properties. The results showed that the composite with successive alkali treated jute fiber at 10% NaOH and H₂O₂ with 20% fiber loading has shown 18% higher flexural strength than neat PLA and untreated jute/PLA composite. The flexural modulus of the composite at 25% fiber loading was 125% and 110% higher than that of composites with untreated fibers and neat PLA, respectively. The impact strength of composite with untreated fibers at higher fiber weight fraction was 23% high as compared to neat PLA and 26% high compared to composite with treated fibers. The water absorption was more for untreated jute/PLA composite at 25% fiber loading than all other composites. The composite with untreated fibers has high thermal degradation compared with treated fibers but lower than that of pure PLA matrix. The enzymatic environment has increased the rate of degradation of composites as compared to soil burial. Surface morphology of biodegraded surfaces of the composites were studied using SEM method. POLYM. COMPOS., 37:2160–2170, 2016. © 2015 Society of Plastics Engineers     

Rheological Characteristics of Short Nylon-6 Fiber Reinforced Styrene Butadiene Rubber Containing Epoxy Resin as Bonding Agent

ABSTRACT

The rheological characteristics of short Nylon-6 fiber–reinforced Styrene Butadiene rubber (SBR) in the presence of epoxy resin–based bonding agent were studied with respect to the effect of shear rate, fiber concentration, and temperature on shear viscosity and die swell using a capillary rheometer. All the composites containing bonding agent showed a pseudoplastic nature, which decreased with increasing temperature. Shear viscosity was increased in the presence of fibers. The temperature sensitivity of the SBR matrices was reduced on introduction of fibers. The temperature sensitivity of the melts was found to be lower at higher shear rates. Die swell was reduced in the presence of fibers. Relative viscosity of the composites increased with shear rate. In the presence of epoxy resin bonding agent the temperature sensitivity of the mixes increased. Die swell was larger in the presence of bonding agent.     

新型炭黑填充抗静电和导电聚丙烯复合材料

以炭黑为导电填料,在聚丙烯中加入适量的环氧树脂和玻璃纤维,制备了新型的抗静电和导电聚丙烯复合材料。测定了不同复合体系的渗滤阈值,用扫描电镜(SEM)对相形貌进行了观察,并研究了环氧树脂和玻璃纤维用量对体积电阻率的影响。SEM照片表明在新型复合材料中,炭黑优先分布在环氧树脂中,环氧树脂包覆在玻璃纤维表面,通过玻璃纤维间的搭接形成导电通路。这种独特的结构使该复合材料的渗滤阈值低于聚丙烯/炭黑和聚丙烯/环氧树脂/炭黑复合体系的渗滤阈值。玻璃纤维和环氧树脂含量分别需要达到约10%,复合材料才能具有抗静电和导电作用。     

Nanostructured fly ash–styrene butadiene rubber hybrid nanocomposites

Hybrid nanocomposites of styrene butadiene rubber (SBR) with nanostructured fly‐ash (NFA) were prepared in the laboratory by melt blending technique in an internal mixer. Curatives were added on a laboratory two‐roll mill. Curing characteristics as well as physico‐mechanical properties of the composites were evaluated. A comparison on SBR composites filled with fresh fly‐ash (FFA); carbon black (CB) and precipitated silica (PS) has been reported. In general, SBR‐NFA composites exhibit higher state of cure and higher strength properties as compared with HAF black‐filled and fresh fly‐ash‐filled SBR composites at equivalent loadings. This may be attributed to the higher reinforcing ability of NFA. This fact has also been supported by the swelling studies and Kraus' plot. Tear strength and abrasion resistance of the SBR‐NFA composites were superior to FFA‐filled and precipitated silica‐filled vulcanizates, but were inferior to carbon black‐ filled SBR vulcanizates. The SBR‐NFA composites showed lower hardness as compared with both the carbon black‐filled and silica‐filled composites. Transmission electron microscopy and scanning probe microscopy studies revealed that the NFA particles are well dispersed in the SBR matrix. These results were further supported by fracture surface analysis under the SEM, which revealed the role of NFA in the prevention of fracture propagation. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Studies on process variables for natural fiber composites—effect of polyesteramide polyol as interfacial agent

A systematic study of the process variables for polyester composites based on different natural fibers like jute, sisal, ramie, and pineapple has been made with a view to determine the most suitable processing conditions for such composites. Effect of polyesteramide polyol (PEAP) as interfacial agent in such composites has also been discussed. Fracture modes of jute/polyester (JP) composite sample having different fiber volume fractions have been examined by scanning electron microscope (SEM). Fracture surfaces of untreated and PEAP-treated JP composite samples have been examined in SEM, both before and after 72 h immersion in boiling water, to study the nature of interfacial bonding on fiber treatment with PEAP. A qualitative improvement in bonding in case of PEAP-treated JP composites is evident from SEM photomicrographs. This is also supported by physicomechanical properties of the composite samples.     

Comparison of mechanical performance and fracture behavior of gelatin composites reinforced with carbon fibers of different fiber architectures

Gelatin‐based composites reinforced, respectively, with continuous carbon fibers, short carbon fibers, plain woven carbon fibers, and carbon fiber felt were investigated. Tensile and shear strengths, and their changes with fiber volume fraction (V_f) of these four composites were compared. It was demonstrated that at all fiber levels, the composite containing continuous carbon fibers showed the largest strength, while the composite reinforced with carbon fiber felt exhibited the lowest strength of the four composites. The above results were analyzed by comparing the fracture surfaces of the four composites. SEM confirmed the great differences in fracture surfaces for composites of different fiber architectures. The presence of a large number of pores in the C_F/Gel composite was responsible for its lowest strength, and cracks within fiber tows caused the lower strength of the C_W/Gel composite when compared to its C_L/Gel counterpart. It was suggested that fiber architecture exerted a great effect on composite performance and the effect was dependent on the nature of the matrix material.     

Influences of liquid elastomer additive on the behavior of short glass fiber reinforced epoxy

In this study, improvements in mechanical and thermal behavior of short glass fiber (GF) reinforced diglycidyl ether of bisphenol-A (DGEBA) based epoxy with hydroxyl terminated polybutadiene (HTPB) modification have been studied. A silane coupling agent (SCA) with a rubber reactive group was also used to improve the interfacial adhesion between glass fibers and an epoxy matrix. 10, 20, and 30 wt% GF reinforced composite specimens were prepared with and without silane coupling agent treatment of fibers and also HTPB modification of epoxy mixture. In the ruber modified specimens, hardener and HTPB were premixed and left at room temperature for 1 hr before epoxy addition. In order to observe the effects of short glass fiber reinforcement of epoxy matrix, silane treatment of fiber surfaces, and also rubber modification of epoxy on the mechanical behavior of specimens, tension and impact tests were performed. The fracture surfaces and thermal behavior of all specimens were examined by scanning electron microscope (SEM), and dynamic mechanical analysis (DMA), respectively. It can be concluded that increasing the short GF content increased the tensile and impact strengths of the specimens. Moreover, the surface treatment of GFs with SCA and HTPB modification of epoxy improved the mechanical properties because of the strong interaction between fibers, epoxy, and rubber. SEM studies showed that use of SCA improved interfacial bonding between the glass fibers and the epoxy matrix. Moreover, it was found that HTPB domains having relatively round shapes formed in the matrix. These rubber domains led to improved strength and toughness, due mainly to the “rubber toughening” effect in the brittle epoxy matrix.     

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     

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     

NOVEL LOW-COST JUTE–POLYESTER COMPOSITE. II. SEM OBSERVATION OF THE FRACTURED SURFACES

The scanning electron micrographs (SEM) were taken at different magnifications with respect of the fractured surfaces of the polymer composites prepared from unsaturated polyester resin and jute sliver with 60% fiber loading by weight. The composite specimens were prepared using both untreated (control) and chemically modified (bleached) jute fibers by solution impregnation and hot curing methods and are designated as JPH-60(C) and JPH-60(B), respectively. The method of preparation of the composite specimens have been discussed. The specimens were subjected to tensile and flexural tests and the fractured surfaces were observed under SEM as stated. The fiber surface morphology was also studied from the SEM photographs in the case of the control and bleached jute filaments. The SEM photographs of the fractured surfaces of the composites showed varied extents of fiber pull-outs under both tensile and flexural failure modes. The nature of interfacial adhesion has been discussed on the basis of the SEM study. A good correlation between the SEM study and the mechanical strength properties of the composites could be established. Exceptionally high flexural strength of the composites JPH-60(B) compared to JPH-60(C) could be explained from the SEM study.     

Effects of kenaf contents and fiber orientation on physical,mechanical, and morphological properties of hybrid laminated composites for vehicle spall liners

The aim of this work is to study the effect of kenaf volume content and fiber orientation on tensile and flexural properties of kenaf/Kevlar hybrid composites. Hybrid composites were prepared by laminating aramid fabric (Kevlar 29) with kenaf in three orientations (woven, 0^o/90^o cross ply uni‐directional (UD), and non‐woven mat) with different kenaf fiber loadings from 15 to 20% and total fiber loading (Kenaf and Kevlar) of 27–49%. The void content varies between 11.5–37.7% to laminate with UD and non‐woven mat, respectively. The void content in a woven kenaf structure is 16.2%. Tensile and flexural properties of kenaf/Kevlar hybrid composites were evaluated. Results indicate that UD kenaf fibers reinforced composites display better tensile and flexural properties as compared to woven and non‐woven mat reinforced hybrid composites. It is also noticed that increasing volume fraction of kenaf fiber in hybrid composites reduces tensile and flexural properties. Tensile fracture of hybrid composites was morphologically analysed by scanning electron microscopy (SEM). SEM micrographs of Kevlar composite failed in two major modes; fiber fracture by the typical splitting process along with, extensive longitudinal matrix and interfacial shear fracture. UD kenaf structure observed a good interlayer bonding and low matrix cracking/debonding. Damage in composite with woven kenaf shows weak kenaf‐matrix bonding. Composite with kenaf mat contains the high void in laminates and poor interfacial bonding. These results motivate us to further study the potential of using kenaf in woven and UD structure in hybrid composites to improve the ballistic application, for example, vehicle spall‐liner. POLYM. COMPOS., 36:1469–1476, 2015. © 2014 Society of Plastics Engineers     

Effect of functionalized elastomer addition on mechanical and interfacial properties of poly (butylene terephthalate)/glass fiber composites

In this study the effect of incorporation of ethylene‐co‐glycidylmethacrylate (GMA)‐co‐n‐butyl acrylate (nBA) terpolymer with an epoxy functional group, on the mechanical performance of short glass fiber (SGF)/Poly (butylene terephthalate) (PBT) composites has been investigated. Tensile test showed that incorporation of rubber phase in PBT/SGF composites results in loss of strength. However impact measurement exhibited an increase in impact strength with an increase in rubber content. Tensile and impact properties are discussed in terms of interfacial shear strength and morphology of composites. Morphological observation by SEM revealed a thin layer of polymer adhering to the surface of glass fibers indicating that epoxy functional group in the modifier reacts with fiber surface and PBT matrix. This reactivity of epoxy functional group is also supported by FTIR observations. The composites are also analyzed for % crystallinity using DSC and a strong correlation is found to exist between interfacial shear strength and % crystallinity. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Effects of chemical surface pretreatment on tensile properties of a single glass fiber and the glass fiber reinforced epoxy composite

The aim of this article is to determine the effect of surface pretreatments, prior to the silanization, on the structure and tensile properties of the glass fibers and their epoxy composites. Commercial glass fibers were washed with acetone to remove the soluble portion of sizing, calcinated for the removal of organic matter, activated for surface silanol regeneration, and silanizated with glycidoxypropyltrimethoxysilane (GPS). Tensile test was carried out. The morphology of pretreated glass fibers and the fracture surfaces of the epoxy composites were observed with a scanning electron microscope (SEM). The results revealed that both apparent modulus and strength of a single glass fiber and the glass fiber/epoxy resin composites strongly depend on the fiber surface pretreatments. The acetone treatment did not change appreciably the composition and tensile properties of glass fibers, but there was a weak interface between fibers and matrix. In calcinated and acid activated fibers, the two competitive effects was observed: (1) degradation of the fibers themselves and (2) improved interfacial adhesion between the glass fibers and the epoxy matrix, once the samples was silanizated. The ATR‐FTIR results show that the surface content of Si OH increases as reflected by the increasing of the Si O band, resulting in an interaction between silane coupling agent and glass fiber. POLYM. COMPOS., 91–100, 2016. © 2014 Society of Plastics Engineers