Effects of rice straw fiber morphology and content on the mechanical and thermal properties of rice straw fiber‐high density polyethylene composites

Rice straw fiber‐high density polyethylene (HDPE) composites were prepared to investigate the effects of rice straw fiber morphology (rice straw refined fiber, rice straw pellet, rice straw strand), fiber content (20 and 40 wt %), and maleic anhydride polyethylene (MAPE) concentration (5 wt %) on the mechanical and thermal properties of the rice straw fiber‐HDPE composites in this study. Rice straw refined fiber exhibited more variability in length and width, and have a higher aspect ratio of 16.3. Compared to the composites filled of rice straw pellet, the composites made of the refined fiber and strand had a slightly higher tensile strength and lower tensile elongation at break. The tensile and flexural strength of the composites increased slightly with increasing rice straw fiber content up to 40 wt %, while the tensile elongation at break decreased. With addition MAPE, the composites filled with 20 wt % rice straw fiber showed an increase in tensile, flexural and impact strength and a decrease in tensile elongation at break. Differential scanning calorimetry showed that the fiber addition and morphology had no appreciable effect on the crystallization temperature of the composites but decreased the crystallinity. The scanning electron microscopy observation on the fracture surface of the composites indicated that introduction of MAPE to the system resulted in promotion in fiber dispersion, and an increase in interfacial bonding strength. Fiber breakage occurred significantly in the composites filled with refined fiber and strand after extruding and injection processing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of wheat straw fiber content and characteristics,and coupling agent concentration on the mechanical properties of wheat straw fiber‐polypropylene composites

Wheat straw fiber‐polypropylene (PP) composites were prepared to investigate the effects of wheat straw fiber content (10, 20, 30, 40, and 50 wt %), fiber size (9, 28, and 35 mesh), and maleic anhydride grafted polypropylene (MAPP) concentration (1, 2, 5, and 10 wt %) on the static and dynamic mechanical properties of the wheat straw fiber‐PP composites in this study. The tensile modulus and strength of the composites increased linearly with increasing wheat straw fiber content up to 40%, whereas the elongation at break decreased dramatically to 3.78%. Compared with the composites made of the longer wheat straw fiber, the composites made of the fines (>35 mesh) had a slightly higher tensile strength of 31.2 MPa and tensile elongation of 5.39% at break. With increasing MAPP concentration, the composites showed an increase in tensile strength, and the highest tensile strength of 34.0 MPa occurred when the MAPP concentration reached 10 wt %. As wheat straw fiber content increased from 0 to 40%, the flexural modulus of the composites increased gradually from 1335 to 3437 MPa. The MAPP concentration and wheat straw fiber size distribution had no appreciable effect on the static flexural modulus of the composites. The storage flexural modulus of the composites increased with increasing wheat straw fiber content. The scanning electron microscopy (SEM) observation on the fracture surface of the composites indicated that a high wheat straw fiber content (>30 wt %) resulted in fiber agglomeration and a reduction in interfacial bonding strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of coupling agents on rice‐husk‐filled HDPE extruded profiles

Lignocellulosic composites are diversifying their applications into various fields as they can meet the requirements of the respective applications by changing the matrix, fiber resource and processing ingredients. In this research work we explored the potential of extruded rice‐husk‐filled high density polyethylene (HDPE) composite profiles for structural applications. The structure and the properties of the interface in fiber‐reinforced composites play a crucial role in determining the performance properties of the composites. An optimum degree of adhesion between the fiber and the matrix is required for efficient stress transfer from the matrix to the fiber. Generally, coupling agents are used to improve the adhesion between lignocellulosic filler and the polymer matrix in structural composite materials. In this study, four different coupling agents based on ethylene‐(acrylic ester)‐(maleic anhydride) terpolymers and ethylene‐(acrylic ester)‐(glycidyl methacrylate) terpolymers were used to enhance the performance properties of the composites. The results indicated that these coupling agents enhanced the tensile and flexural strength of the composites significantly, and the extent of the coupling effect depends on the nature of the interface formed. Incorporation of coupling agents enhanced the resistance to thermal deformation and the water absorption properties of the composite, whereas it reduced the extrusion rate significantly. Among the four coupling agents used, EGMA1—the one with a glycidyl methacrylate functional group and without any methyl acrylate pendant group on the polymer backbone—was found to be the best coupling agent for the rice‐husk‐filled HDPE composites. Copyright © 2004 Society of Chemical Industry     

Kenaf‐bast‐fiber‐filled biodegradable poly(butylene succinate) composites: Effects of fiber loading,fiber length,and maleated poly(butylene succinate) on the flexural and impact properties

Poly(butylene succinate) (PBS) filled kenaf bast fiber (KBF) composites were fabricated via compression molding. The effects of KBF loading on the flexural and impact properties of the composites were investigated for fiber loadings of 10–40 wt %. The optimum flexural strength of the composites was achieved at 30 wt % fiber loading. However, the flexural modulus of the composites kept increasing with increasing fiber loading. Increasing the fiber loading led to a drop in the impact strength of about 57.5–73.6%; this was due to the stiff nature of the KBF. The effect of the fiber length (5, 10, 15, and 20 mm) on the flexural and impact properties was investigated for the 30 wt % KBF loaded composites. The composites with 10‐mm KBF showed the highest flexural and impact properties in comparison to the others. The inferior flexural and impact strength of the composites with 15‐ and 20‐mm KBF could be attributed to the relatively longer fibers that underwent fiber attrition during compounding, which consequently led to the deterioration of the fiber. This was proven by analyses of the fiber length, diameter, and aspect ratio. The addition of maleated PBS as a compatibilizer resulted in the enhancement of the composite's flexural and impact properties due to the formation of better fiber–matrix interfacial adhesion. This was proven by scanning electron microscopy observations of the composites' fracture surfaces. The removal of unreacted maleic anhydride and dicumyl peroxide residuals from the compatibilizers led to better fiber–matrix interfacial adhesion and a slightly enhanced composite strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication and evaluation of some mechanical and electrical properties of jute‐biomass based hybrid composites

Hybrid composites based on bisphenol‐C‐formaldehyde resin and jute mat with rice, wheat, sugar cane, and jamun husks have been fabricated at 150°C under 30.4 MPa pressure for 2 h. The resin content in composites was 50% of fibers. Tensile strength, flexural strength, electric strength, and volume resistivity of hybrid composites have been evaluated and compared with those of jute‐bisphenol‐C‐formaldehyde composites. It is observed that the tensile strength of composites is found to decrease by 53–72%, which is mainly due to random orientation of sandwiched fibers. Flexural strength has increased by 53–153% except jute–rice husk composite for which it is decreased by 26%. A little change in dielectric breakdown strength (1.89–2.11 kV/mm) is found but volume resistivity of Jute–wheat husk and Jute–jamun husk composites has improved by 437–197% and it is slightly decreased(2.3–25.2%) for the remaining two composites. Thus, hybrid composites possess good mechanical and electrical properties signifying their importance in low strength and light weight engineering applications as well as low cost housing units such as partition and hard boards. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1754–1758, 2006     

Studies on mechanical characterization and water resistance of glass fiber/thermoplastic polymer bionanocomposites

This experimental work is aimed at studying the performance of rice husk flour/glass fiber reinforced high density polyethylene hybrid nanocomposites. To meet this objective, the nanoclay was compounded with high density polyethylene (HDPE), rice husk flour (RF), glass fiber, and coupling agent in an internal mixer; then, the samples were fabricated by injection molding. The concentration was varied from 0 to 6 per hundred compounds for nanoclay and from 0 to 15% for glass fiber, individually. The amount of coupling agent was fixed at 2% for all formulations. The morphology, water absorption, thickness swelling, and mechanical properties of nanocomposites were evaluated as a function of nanoclay and glass fiber contents. The results indicated that both modulus and strength were improved when glass fibers were added to the composites system but impact strength and moisture absorption further decreased with the increase of glass fiber content. The morphology of the nanocomposites has been examined by using X‐ray diffraction. The morphological findings revealed that the nanocomposites formed were intercalated. The mechanical analysis showed that the biggest improvement of the tensile and flexural modulus and strengths can be achieved for the nanoclay loading at 4 per hundred compounds. However, further increasing of the loading of nanoclay resulted in a decrease of impact strength. Finally, it was found that addition of nanoclay reduced the water absorption and thickness swelling of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Natural fiber blend—nylon 6 composites

In this study, engineering thermoplastic composites were prepared from natural fiber blend–filled nylon 6. Natural fiber blend from a mixture of kenaf, flax, and hemp fibers were added to nylon 6 using melt mixing to produce compounded pellets. The natural fibers/ nylon6 composites with varying concentrations of natural fibers (from 5 to 20 wt%) were prepared by injection molding. The tensile and flexural properties of the nylon 6 composites were increased significantly with the addition of the natural fiber blend. The maximum strength and modulus of elasticity for the nylon 6 composites were achieved at a natural fiber blend weight fraction of 20%. The Izod impact strength of composites decreased with the incorporation of natural fibers without any surface treatments and coupling agent. The melt flow index (MFI) also decreased with increasing natural fiber blend loading. The results of tensile and flexural modulus of elasticity (FMOE) are in accordance with the rheological data from the MFI measurements. The increase in the tensile and flexural properties indicated that efficient bonding occurred between the natural fibers and nylon 6. No fiber pullout was observed during the scanning electron microscopic analysis of the fracture surfaces. The higher mechanical results with lower density demonstrate that a natural fiber blend can be used as a sufficient reinforcing material for low‐cost, eco‐friendly composites in the automotive industry and in other applications such as the building and construction industries, packaging, consumer products, etc.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Mechanical properties and water absorption of fiber‐reinforced polypropylene composites prepared by bagasse and beech fiber

The present study investigates the tensile, flexural, notched Izod impact, and water absorption properties of bagasse and beech reinforced polypropylene (PP) composites as a function of fiber content. The surface of fibers was modified through the use of maleated polypropylene (MAPP) coupling agent. From this study, it was found that mechanical properties increase with an increase in fiber loading in both cases. However, the addition of wood fibers resulted in a decrease in impact strength of the composites. The water absorption property at varying fiber loading was evaluated and found maximum for the BA/PP composites. The weight gains for all specimens were less than 7%. In general, the results showed the usefulness of bagasse fiber as a good alternative and reinforcing agent for composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Morphological and physicomechanical analysis of high‐density polyethylene filled with Salago fiber

The environmental issues associated with the mass discarding of waste plastics in the Philippines have significantly raised for the past decade. However, this country is a home to many natural fibers which necessitates the development of ecofriendly materials to diminish the environmental footprint of polymers. High‐density polyethylene (HDPE) was filled with floured untreated and 5 wt % alkaline‐treated Salago fiber via melt compounding. The physical and mechanical characteristics of both types of composites were measured and compared. The composite filled with 30 wt % untreated fiber became very brittle, showing tensile strength and impact resistance of 15.8 MPa and 4.9 kJ/m², respectively. Alkaline treatment improved the mechanical properties of untreated composites, but not above the value of virgin HDPE. Nevertheless, the flexural strength of treated composites exceeded that of the virgin HDPE. Untreated composites absorbed water twice as the treated ones. Finally, morphological and fractography inspection on tensile and flexural test specimens showed improvement made by treatment on the interfacial adhesion between fiber and thermoplastic, corroborating the results from mechanical properties test. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46479.     

Influence of interfacial adhesion on the structural and mechanical behavior of PP‐banana/glass hybrid composites

Hybrid composites of polypropylene (PP), reinforced with short banana and glass fibers were fabricated using Haake torque rheocord followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both fibers into PP matrix resulted in increase of tensile strength, flexural strength, and impact strength upto 30 wt% with an optimum strength observed at 2 wt% MAPP treated 15 wt% banana and 15 wt% glass fiber. The rate of water absorption for the hybrid composites was decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has been analyzed to investigate the interfacial properties. An increase in storage modulus (E′) of the treated‐composite indicates higher stiffness. The loss tangent (tan δ) spectra confirms a strong influence of fiber loading and coupling agent concentration on the α and β relaxation process of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out through differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA), indicated an increase in the crystallization temperature and thermal stability of PP with the incorporation of MAPP‐treated banana and glass fiber. POLYM. COMPOS., 31:1247–1257, 2010. © 2009 Society of Plastics Engineers     

Impact and flexural properties of stone‐ground wood pulp‐reinforced polypropylene composites

This study analyses the flexural and impact strength of polypropylene reinforced with stone ground wood pulp (SGWP) and the effect of a maleated‐polypropylene (MAPP) coupling agent on the mechanical properties of these composites. Composites prepared in the absence of the coupling agent showed a very light positive linear evolution of the flexural strength with the percentage of reinforcing fiber. In contrast, composites that included MAPP in their formulation presented highly noticeable improvements with fiber content. By applying mathematical modeling strategies, the flexural modulus has been analyzed using the Cox–Krenchel model. Similarly, the flexural and tensile strength factors for the reinforcing fiber have been defined and utterly allowed for the determination of intrinsic fiber flexural strength. POLYM. COMPOS., 34:842–848, 2013. © 2013 Society of Plastics Engineers     

Mechanical,thermal, and morphological properties of maleic anhydride‐g‐polypropylene compatibilized and chemically modified banana‐fiber‐reinforced polypropylene composites

Composites were prepared with chemically modified banana fibers in polypropylene (PP). The effects of 40‐mm fiber loading and resin modification on the physical, mechanical, thermal, and morphological properties of the composites were evaluated with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Infrared (IR) spectroscopy, and so on. Maleic anhydride grafted polypropylene (MA‐g‐PP) compatibilizer was used to improve the fiber‐matrix adhesion. SEM studies carried out on fractured specimens indicated poor dispersion in the unmodified fiber composites and improved adhesion and uniform dispersion in the treated composites. A fiber loading of 15 vol % in the treated composites was optimum, with maximum mechanical properties and thermal stability evident. The composite with 5% MA‐g‐PP concentration at a 15% fiber volume showed an 80% increase in impact strength, a 48% increase in flexural strength, a 125% increase in flexural modulus, a 33% increase in tensile strength, and an 82% increase in tensile modulus, whereas the heat deflection temperature increased by 18°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mica reinforced nylon‐6: Effect of coupling agents on mechanical,thermal, and dielectric properties

The effects of applying titanate (TYZOR® TPT) and silane (DYNASYLAN VTMO) coupling agents to wet ground muscovite mica in nylon‐6 composites are described. Nylon‐6 composites of 5–40 wt % filler loadings were compounded using an APV Baker twin‐screw extruder. Mica (25 wt %) brought about an increase in the Young's modulus, flexural strength, and flexural modulus but did not produce significant variations in tensile and impact strength. Hence different coupling agents were employed. It was observed that titanate coupling agent improved the tensile strength and the Young's modulus of the composites much while the impact properties were enhanced by the silane coupling agent. An attempt was made to use ?‐caprolactum in improving the interfacial adhesion of the filler and the matrix. It was observed that ?‐caprolactum improved the flexural modulus of the composites most. The effect of coupling agents on the dielectric strength, heat distortion temperature, and morphology were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4074–4081, 2006     

Biodegradability and mechanical properties of agro‐flour–filled polybutylene succinate biocomposites

The objective of this study was the production of rice husk flour (RHF) and wood flour (WF) filled polybutylene succinate (PBS) biocomposites as alternatives to cellulosic material filled conventional plastic (polyolefins) composites. PBS is one of the biodegradable polymers, made from the condensation reaction of 1,4‐butanediol and succinic acid that can be naturally degraded in the natural environment. We compared the mechanical properties between conventional plastics and agro‐flour–filled PBS biocomposites. We evaluated the biodegradability and mechanical properties of agro‐flour–filled PBS biocomposites according to the content and filler particle size of agro‐flour. As the agro‐flour loading was increased, the tensile and impact strength of the biocomposites decreased. As the filler particle size decreased, the tensile strength of the biocomposites increased but the impact strength decreased. The addition of agro‐flour to PBS produced a more rapid decrease in the tensile strength, notched Izod impact strength, and percentage weight loss of the biocomposites during the natural soil burial test. These results support the application of biocomposites as environmentally friendly materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1513–1521, 2005     

Comparison of the effects of polyethylenimine and maleated polypropylene coupling agents on the properties of cellulose‐reinforced polypropylene composites

The desire to improve the properties of cellulose‐reinforced composites while producing them by methods as similar as possible to those used on an industrial scale is one of the driving forces in this field of research. In this work, extensive research for determining the mechanical, thermal, rheological, and physical properties of novel cellulose‐reinforced polypropylene composites containing a polyethylenimine (PEI) coupling agent was conducted. A comparison of their properties with those of reference composites without any coupling agent or containing a maleated polypropylene (MAPP) coupling agent was also carried out. The presence of the PEI coupling agent mainly gave rise to a substantial increase in the tensile and flexural strengths and elongations as well as the impact strength, heat deflection temperature (HDT), melt volume flow index, and water absorption of PEI‐containing composites in comparison with composites without any coupling agent added. However, the increases achieved in the tensile and flexural composite strengths and HDT were lower than those achieved with the MAPP coupling agent mainly for composites containing 50 wt % cellulose fibers. On the other hand, PEI‐containing composites exhibited, in most cases, larger elongations and energies required to break in tensile tests as well as larger impact strengths, melt volume flow indices, and water absorption percentages than MAPP‐containing composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of macromolecular coupling agent on the property of PP/GF composites

Silane‐grafted polypropylene manufactured by a reactive grafting process was used as the coupling agent in polypropylene/glass‐fiber composites to improve the interaction of the interfacial regions. Polypropylene reinforced with 30% by weight of short glass fibers was injection‐molded and the mechanical behaviors were investigated. The results indicate that the mechanical properties (tensile strength, tensile modulus, flexural strength, flexural modulus, and Izod impact strength) of the composite increased remarkably as compared with the noncoupled glass fiber/polypropylene. SEM of the fracture surfaces of the coupled composites shows a good adhesion at the fiber/matrix interface: The fibers are coated with matrix polymer, and a matrix transition region exists near the fibers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1537–1542, 1999     

Viscose fiber/polyamide 12 composites: Novel gas‐phase method for the modification of cellulose fibers with an aminosilane coupling agent

The objective of this study was to improve the adhesion between viscose fibers and polyamide 12 and, thereby, the mechanical properties of the corresponding composites. The cellulose fiber surface was chemically modified in the vapor phase with a silyl coupling agent, aminosilane [(3‐aminopropyl) triethoxysilane]. This new gas‐phase treatment for cellulose fibers proved to be highly effective. Relative to composites without the coupling‐agent treatment, the tensile strength of the composites (40/60 wt % fiber/polymer) increased from 49.3 to 87.4 MPa; the improved adhesion between the fibers and matrix induced by the coupling agent was observed under a scanning electron microscope. The presence and bonding of the coupling agent on the fibers after the reaction was confirmed by solid‐state ²⁹Si‐NMR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4478–4483, 2006     

The influence of chemical surface modification on the performance of sisal‐polyester biocomposites

This article concerns the effectiveness of various types and degrees of surface modification of sisal fibers involving dewaxing, alkali treatment, bleaching cyanoethylation and viny1 grafting in enhancing the mechanical properties, such as tensile, flexural and impact strength, of sisal‐polyester biocomposites. The mechanical properties are optimum at a fiber loading of 30 wt%. Among all modifications, cyanoethylation and alkali treatment result in improved properties of the biocomposites. Cyanoethylated sisal‐polyester composite exhibited maximum tensile strength (84.29 MPa). The alkali treated sisal‐polyester composite exhibited best flexural (153.94 MPa) and impac strength (197.88 J/m), which are, respectively, 21.8% and 20.9% higher than the corresponding mechanical properties of the untreated sisal‐polyester composites. In the case of vinyl grafting, acrylonitrile (AN)‐grafted sisal‐polyester composites show better mechanical properties than methyl‐methacrylate (MMA)‐grafted sisal composites. Scanning electron microscopic studies were carried out to analyze the fiber‐matrix interaction in various surface‐modified sisal‐polyester composites.     

Effect of the delignification of wood fibers on the mechanical properties of wood fiber–polypropylene composites

The effect of the delignification of hornbeam fibers on the mechanical properties of wood fiber–polypropylene (PP) composites was studied. Original fibers and delignified fibers at three levels of delignification were mixed with PP at a weight ratio of 40:60 in an internal mixer. Maleic anhydride (0.5 wt %) as the coupling agent and dicumyl peroxide (0.1 wt %) as the initiator were applied. The produced composites were then hot‐pressed, and specimens for physical and mechanical testing were prepared. The results of the properties of the composite materials indicate that delignified fibers showed better performance in the enhancement of tensile strength and tensile modulus, whereas the hardness of the composites was unaffected by delignification. Delignified fibers also exhibited better water absorption resistance. Notched impact strength was higher for delignified fiber composites, but it was reduced at higher delignification levels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4759–4763, 2006