Environmental durability of banana‐fiber‐reinforced phenol formaldehyde composites

We explored the environmental aging behavior of banana‐fiber‐reinforced phenol formaldehyde (PF) composites. The composites were subjected to water aging, thermal aging, soil burial, and outdoor weathering. The effects of chemical modification and hybridization with glass fibers on the degradability of the composites in different environments were analyzed. The extent of degradation was measured by changes in the weight and tensile properties after aging. Absorbed water increased the weight of water‐aged composites, and chemical treatments and hybridization decreased water absorption. The tensile strength and modulus of the banana/PF composites were increased by water aging, whereas the strength and modulus of the glass/PF composites were decreased by water aging. As the glass‐fiber loading was increased in the hybrid composites, the increase in strength by water aging was reduced, and at higher glass‐fiber loadings, a decrease in strength was observed. The tensile properties of the composites were increased by oven aging. The percentage weight loss was higher for soil‐aged samples than for samples weathered outdoors. The weight loss and tensile strength of the glass/PF composites and banana/glass/hybrid/PF composites were much lower than those of the banana/PF composites. Silane treatment, NaOH treatment, and acetylation improved the resistance of the banana/PF composites on outdoor exposure and soil burial. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2521–2531, 2006     

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     

Characterization and biocompatibility of chestnut shell fiber–based composites with polyester

The structural, mechanical, biocompatibility, and biodegradability properties of composite materials formed of poly(butylene succinate) (PBS) and natural fiber (chestnut shell fiber; CSF) were evaluated. Maleic anhydride‐grafted poly(butylene succinate) (PBS‐g‐MA) and treated (crosslinked) CSF (TCSF) were used to improve the mechanical properties of PBS/CSF composites. The results show that PBS‐g‐MA/TCSF composites have superior mechanical properties compared with both pure PBS and PBS/CSF composites, which is attributed to better compatibility between the polymer and TCSF. Normal human foreskin fibroblasts (FBs) were seeded onto these two series of composites to characterize the biocompatibility. FB proliferation, collagen production, and cytotoxicity assays on the PBS/CSF series of composites exhibited superior results compared with those on the PBS‐g‐MA/TCSF composites. PBS‐g‐MA/TCSF was found to be more water resistant than PBS/CSF, and the weight loss of both the composites buried in soil compost indicated that both were biodegradable, especially at high levels of CSF substitution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40730.     

Freeze–thaw resistance of unidirectional‐fiber‐reinforced epoxy composites

The freeze–thaw resistance of unidirectional glass‐, carbon‐, and basalt‐fiber‐reinforced polymer (GFRPs, CFRPs, and BFRPs, respectively) epoxy wet layups was investigated from ?30 to 30°C in dry air. Embedded optic‐fiber Bragg grating sensors were applied to monitor the variation of the internal strain during the freeze–thaw cycles, with which the coefficient of thermal expansion (CTE) was estimated. With the CTE values, the stresses developed in the matrix of the FRPs were calculated, and CFRPs were slightly higher than in the BFRP and GFRP cases. The freeze–thaw cycle showed a negligible effect on the tensile properties of both GFRP and BFRP but exhibited an adverse effect on CFRP, causing a reduction of 16% in the strength and 18% in the modulus after 90 freeze–thaw cycles. The susceptibility of the bonding between the carbon fibers and epoxy to the freeze–thaw cycles was assigned to the deterioration of CFRP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of layering pattern on dynamic mechanical properties of randomly oriented short banana/sisal hybrid fiber–reinforced polyester composites

Dynamic mechanical test methods have been widely employed for investigating the structures and viscoelastic behavior of polymeric materials to determine their relevant stiffness and damping characteristics for various applications. Randomly oriented short banana/sisal hybrid fiber–reinforced polyester composites were prepared by keeping the volume ratio of banana and sisal 1 : 1 and the total fiber loading 0.40 volume fraction. Bilayer (banana/sisal), trilayer (banana/sisal/banana and sisal/banana/sisal), and intimate mix composites were prepared. The effect of layering pattern on storage modulus (E′), damping behavior (tan δ), and loss modulus (E″) was studied as a function of temperature and frequency. Bilayer composite showed high damping property while intimately mixed and banana/sisal/banana composites showed increased stiffness compared to the other pattern. The Arrhenius relationship has been used to calculate the activation energy of the glass transition of the composites. The activation energy of the intimately mixed composite was found to be the highest. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2168–2174, 2005     

Influence of fiber orientation and fiber content on properties of sisal‐jute‐glass fiber‐reinforced polyester composites

The incorporation of natural fibers with polymer matrix composites (PMCs) has increasing applications in many fields of engineering due to the growing concerns regarding the environmental impact and energy crisis. The objective of this work is to examine the effect of fiber orientation and fiber content on properties of sisal‐jute‐glass fiber‐reinforced polyester composites. In this experimental study, sisal‐jute‐glass fiber‐reinforced polyester composites are prepared with fiber orientations of 0° and 90° and fiber volume of sisal‐jute‐glass fibers are in the ratio of 40:0:60, 0:40:60, and 20:20:60 respectively, and the experiments were conducted. The results indicated that the hybrid composites had shown better performance and the fiber orientation and fiber content play major role in strength and water absorption properties. The morphological properties, internal structure, cracks, and fiber pull out of the fractured specimen during testing are also investigated by using scanning electron microscopy (SEM) analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42968.     

Performance of pineapple leaf fiber–natural rubber composites: The effect of fiber surface treatments

Composites of natural rubber (NR) and short pineapple leaf fiber (PALF) were prepared on a laboratory two‐roll mill. The influences of untreated fiber content and orientation on the processing and mechanical properties of the composites were investigated. The dependence of extent of orientation on fiber concentration was also established. Sodium hydroxide (NaOH) solutions (1, 3, 5, and 7% w/v) and benzoyl peroxide (BPO) (1, 3, and 5 wt % of fiber) were used to treat the surfaces of PALFs. FTIR and scanning electron microscope (SEM) observations were made of the treatments in terms of chemical composition and surface structure. The tensile strength and elongation at break of the composites were later studied. The fiber–matrix adhesion was also investigated using SEM technique. It was found that all surface modifications enhanced adhesion and tensile properties. The treatments with 5% NaOH and 1% BPO provided the best improvement of composite strength (28 and 57% respectively) when compared with that of untreated fiber. The PALF‐NR composites also exhibited better resistance to aging than its gum vulcanizate, especially when combined with the treated fibers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1974–1984, 2006     

Study on morphology development for in situ fiber–reinforced composites by blending polyolefin and polycaprolactone

The morphology developments and interfacial properties of extruded polyethylene/polycaprolactone and polypropylene/polycaprolactone blends were investigated. The interfacial thicknesses of both polymer blends were thin and this was investigated by interfacial tension measurement in the melt state. The aspect of boundary area was observed by AFM, and a clear line could be observed at the interface area as a result of thin interfacial thickness. The in situ fiber formation of the dispersed phase was remarkably generated under elongational flow (between die exit and solidification) rather than under shear flow (in the cylinder and die). Drawing ratio was varied at three levels to study its effect on elongation of the dispersed phases. The dispersions dramatically changed from spherical to spheroidal and filament shapes depending on the drawing ratio. Reduced capillary number (Ca*) was used to characterize droplet deformation. The deformation mode under shear flow was classified as nondeformation mode due to the fact that the Ca* was almost 0. On the other hand, the deformation mode under elongational flow was classified into filament shape mode (Ca* > 4). This classification was in agreement with the SEM images. The tensile properties were increased at the border line where the Ca* was 4.0. The melt interfacial tensions of polyolefin/polycaprolactone were relatively large, and a clear line could be observed at the interface area as a result of little affinity of polymer interface. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 500–508, 2005     

Flexural behavior of methyl methacrylate modified unsaturated polyester polymer concrete beams reinforced with glass‐fiber‐reinforced polymer sheets

This study represents the behavior of flexural test of methyl methacrylate modified unsaturated polyester polymer concrete beam reinforced with glass‐fiber‐reinforced polymer (GFRP) sheets. The failure mode, load–deflection, ductility index, and separation load predictions according to the GFRP reinforcement thickness were tested and analyzed. The failure mode was found to occur at the bonded surface of the specimen with 10 layers of GFRP reinforcement. For the load–deflection curve, as the reinforcement thickness of the GFRP sheet increased, the crack load and ultimate load greatly increased, and the ductility index was found to be the highest for the beam with the thickness of the GFRP sheet at 10 layers (6 mm) or 13 layers (7.3 mm). The calculated results of separation load were found to match only the experimental results of the specimens where debonding occurred. The reinforcement effect was found to be most excellent in the polymer concrete with 10 layers of GFRP sheet reinforcement. The appropriate reinforcement ratio for the GFRP concrete beam suggested by this study was a fiber‐reinforced‐plastic cross‐sectional ratio of 0.007–0.008 for a polymer concrete cross‐sectional ratio of 1 (width) : 1.5 (depth). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cure characteristics and mechanical properties of short nylon fiber‐reinforced nitrile rubber composites

Acrylonitrile butadiene rubber (NBR)‐based composites were prepared by incorporating short nylon fibers of different lengths and concentration into the matrix using a two‐roll mixing mill according to a base formulation. The curing characteristics of the samples were studied. The influence of fiber length, loading, and rubber crosslinking systems on the properties of the composites was analyzed. Surface morphology of the composites has been studied using Scanning Electron Microscopy (SEM). Addition of nylon fiber to NBR offers good reinforcement, and causes improvement in mechanical properties. A fiber length of 6 mm was found to be optimum for the best balance of properties. It has been found that at higher fiber loadings, composites show brittle‐type behavior. Composites vulcanized by the dicumyl peroxide (DCP) system were found to have better mechanical properties than that by the sulfur system. The swelling behavior of the composites in N,N‐dimethyl formamide has been analyzed for the swelling coefficient values. Composites vulcanized in the DCP system were found to have higher rubber volume fraction than that in the sulfur system, which indicates better rubber–fiber interaction in the former. The crosslink densities of various composites were also compared. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1023–1030, 2004     

Tensile stress relaxation of short‐coir‐fiber‐reinforced natural rubber composites

The stress relaxation behavior of natural rubber (NR) and its composites reinforced with short coir fibers under tension was analyzed. The rate of stress relaxation was a measure of the increase in the entropy of the compounds: the higher the rate was, the greater the entropy was. At lower strain levels, the relaxation mechanism of NR was independent of strain level. However, the rate of relaxation increased with the strain level. Also, the strain level influenced the rate of stress relaxation considerably in the coir‐reinforced NR composites. However, the relaxation mechanisms of both the unfilled compound and the composite were influenced by the strain rate. The rate of relaxation was influenced by fiber loading and fiber orientation. From the rate of stress relaxation, we found that fiber–rubber adhesion was best in the composite containing fibers subjected to a chemical treatment with alkali, toluene diisocyanate, and NR solutions along with a hexaresorcinol system as a bonding agent. In this study, the stress relaxation curves could not be viewed as segments with varying slopes; however, a multitude of inflection points were observed on the curves. Hence, we propose neither a two‐step nor three‐step mechanism for the coir‐fiber‐reinforced NR composites as reported for some other systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 96–104, 2004     

Improvement of mechanical properties of natural fiber–polypropylene composites using successive alkaline treatments

The use of natural fibers (NFs) in polymer composites for structural applications has increased greatly in the last years, owing to their abundance and biodegradability. In this work, an innovative and simple successive alkali treatment has been developed to improve the mechanical properties of NFs/polypropylene (PP) composites. Three different cellulosic fibers (curauá, jute, and flax) were used, with a fixed proportion of 10 wt %. The fibers were immersed several times in a 5 wt % NaOH solution. Thermogravimetric analysis data showed an improvement in thermal properties of the fibers, as well as the increase of the crystallinity degree was measured by X‐ray diffraction. By Fourier transform infrared spectroscopy, disappearance of characteristics peaks of hemicelluloses and lignin was observed. Finally, mechanical behavior of the NF/PP composites was examined, using dynamic mechanical analysis. The results revealed that the curauá/PP mechanical properties were significantly improved, showing the positive effect of the successive alkali treatments. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41710.     

Investigation of mechanical properties of alumina nanoparticle‐loaded hybrid glass/carbon‐fiber‐reinforced epoxy composites

This research work investigates the tensile strength and elastic modulus of the alumina nanoparticles, glass fiber, and carbon fiber reinforced epoxy composites. The first type composites were made by adding 1–5 wt % (in the interval of 1%) of alumina to the epoxy matrix, whereas the second and third categories of composites were made by adding 1–5 wt % short glass, carbon fibers to the matrix. A fourth type of composite has also been synthesized by incorporating both alumina particles (2 wt %) and fibers to the epoxy. Results showed that the longitudinal modulus has significantly improved because of the filler additions. Both tensile strength and modulus are further better for hybrid composites consisting both alumina particles and glass fibers or carbon fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39749.     

Effect of rare earth elements surface treatment on tensile properties of aramid fiber‐reinforced epoxy composites

Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of aramid fiber. Tensile properties of both the aramid/epoxy composites and single fibers were tested. The effects of RES concentration on tensile properties of aramid/epoxy composites were investigated in detail to explore an optimum amount of rare earth elements in solution for modifying aramid fiber. The fracture surface morphologies of tensile specimens were observed and analyzed with the aid of SEM. The experimental results show that rare earth treatment is superior to ECP grafting treatment in promoting interfacial adhesion between the aramid fiber and epoxy matrix. Meanwhile, the tensile strengths of single fibers were almost not affected by RES treatment. The optimum performance is obtained when the content of rare earth elements is 0.5 wt %. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1037–1041, 2004     

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 thermal shock on interlaminar strength of thermally aged glass fiber‐reinforced epoxy composites

Glass fiber/epoxy composites were thermally conditioned at 50, 100, 150, 200, and 250°C for different periods of time and then immediately quenched directly in ice‐cold water from each stage of conditioning temperature. The polymerization or depolymerization by thermal conditioning and the debonding effect by concurrently following thermal shock in polymer composites are assessed in the present study. The short‐beam shear tests were performed at room temperature on the quenched samples to evaluate the value of interlaminar shear strength of the composites. The short conditioning time followed by thermal shock resulted in reduction of shear strength of the composites. The strength started regaining its original value with longer conditioning time. Conditioning at 250°C and thereafter quenching yielded a sharp and continuous fall in the shear strength. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2062–2066, 2006     

Experimental characterization of woven jute‐fabric‐reinforced isothalic polyester composites

In this article, mechanical performance of isothalic polyester‐based untreated woven jute‐fabric composites subjected to various types of loading has been experimentally investigated. The laminates were prepared by hand lay‐up technique in a mold. Specimens for tests were fabricated as per ASTM standards. All the tests (except impact) were conducted on closed loop servo hydraulic MTS 810 material test system using data acquisition software Test Works‐II. From the results obtained, it was found that the tensile strength and tensile modulus of jute‐fabric composite are 83.96% and 118.97% greater than the tensile strength and modulus of unreinforced resin, respectively. The results of other properties, such as flexural, in‐plane shear, interlaminar shear, impact, etc., also revealed that the isothalic‐polyester‐based jute‐fabric composite have good mechanical properties and can be a potential material for use in medium load‐bearing applications. The failure mechanism and fiber‐matrix adhesion were analyzed by scanning electron microscope. Effects of long‐term immersion in water on mechanical properties are also presented. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2650–2662, 2007     

Influence of fiber modification on interfacial adhesion and mechanical properties of pineapple leaf fiber‐epoxy composites

Three kinds of surface treatment, that is, the alkalization (5% w/v NaOH aqueous solution), the deposition of diglycidyl ether of bisphenol A (DGEBA) from toluene solution (1% w/v DGEBA), and the alkalization combined with the deposition of DGEBA (5% w/v NaOH/1% w/v DGEBA) were applied to modify interfacial bonding and to enhance mechanical properties of pineapple leaf fiber (PALF) reinforced epoxy composites. The fiber strength and strain were measured by single fiber test and the fiber strength variation was assessed using Weibull modulus. Furthermore, a fragmentation test was used to quantify the interfacial adhesion of PALF‐epoxy composite. It was verified that the interfacial shear strength of modified PALFs was substantially higher than that of untreated PALF by almost 2–2.7 times because of the greater interaction between the PALFs and epoxy resin matrix. The strongest interfacial adhesion was obtained from the fibers that had been received the alkalization combined with DGEBA deposition. Moreover, the flexural and impact properties of unidirectional PALF‐epoxy composites were greatly enhanced when reinforced with the modified PALFs due to an improvement in interfacial adhesion, particularly in the synergetic use of 5% NaOH and 5% NaOH/1% DGEBA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of structure on mechanical properties of vinyl ester resins and their glass fiber‐reinforced composites

The article describes the effect of structure of vinyl ester resins (VE) on the mechanical properties of neat sheets as well as glass fabric‐reinforced composites. Different samples of VE were prepared by reacting ester of hexahydrophthalic anhydride (ER) and methacrylic acid (MAA) (1 : 1 molar ratio) followed by reaction of monomethacrylate terminated epoxy resin with glutaric (E) or adipic (F) or sebacic acid (G) (2 : 1 molar ratio). The neat VE were diluted with styrene and sheets were fabricated by using a glass mold. A significant reduction in the mechanical properties was observed by increasing the methylene content of resin backbone (i.e., sample E to G). Glass fabric‐reinforced composites were fabricated by vacuum assisted resin transfer molding (VARTM) technique. Resin content in the laminates was 50 ± 5 wt %. Increase in the number of methylene groups in the vinyl ester resin (i.e., increasing the bridge length) did not show any significant effect on limiting oxygen index (LOI) value (21 ± 1) of the laminates but tensile strength, tensile modulus, flexural strength, and flexural modulus all increased though these values are significantly lower than observed in laminates based on resin B. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008