Unsaturated Polyester-Kenaf Composites: The Effects of a Modified Montmorillonite Filler on the Tensile Properties

This study has been embarked to use the nanofiller to compensate the adverse effect of the lignocellulosic filler. Unsaturated polyester-kenaf composites filled with various types of MMT filler were produced. The study showed that the incorporation of untreated montmorillonite filler (UNT-MMT) and cetyl trimethyl ammonium bromide-modified (CTAB-MMT) had improved the tensile properties. The superior properties of those with CTAB-MMT were attributed to more effective distribution of MMT in the matrix, the availability of effective high aspect ratio MMT and increased compatibility of MMT with the matrix as the results of the introduction of long polymer chain from CTAB.     

Tensile properties of kenaf/unsaturated polyester composites filled with a montmorillonite filler

Kenaf/unsaturated polyester composites filled with montmorillonite (MMT) filler were produced. Overall, the study showed that, for samples with kenaf filler only, the strength properties decreased as the kenaf filler loading was increased from 40 to 60%. The increase in the kenaf filler loading reduced the amount of matrix material. This subsequently lowered the ability of the sample to absorb energy or distribute stress efficiently. However, with MMT, the tensile properties improved because of the high aspect ratio and surface area of the MMT. The study of the effect of kenaf filler size on the tensile properties showed that the samples with the smallest size (74 μm) displayed the lowest tensile properties compared to the larger ones. This was attributed to the agglomeration of the kenaf fillers. The addition of MMT resulted in an overall increase in the tensile strength of the composites compared to those without MMT. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The Properties of Woven Kenaf and Betel Palm (Areca catechu) Reinforced Unsaturated Polyester Composites

The use of woven betel palm and kenaf lignocellulosic fibers as a reinforcing phase in unsaturated polyester was reported. The morphology, physical properties, and mechanical properties of the natural fibers and resulting woven composites were evaluated. Kenaf fibers exhibit higher tensile properties than betel palm fibers due to the higher amount of cellulose content. From the morphology observation, it is found that the alkaline treatment of the fibers effectively clean the fiber surface and increase the fiber surface roughness. Comparison between treated and untreated woven betel palm and kenaf composites at 7 vol% of fiber content was carried out. Interestingly, untreated woven kenaf composites exhibit comparable flexural strength with those of untreated woven betel palm composites. However, untreated kenaf composites exhibit superior flexural modulus to those of betel palm composites. In general, mechanical properties of the woven composites made from alkali-treated fibers were superior to the untreated fibers.     

Investigation of acrylamide‐modified melamine‐formaldehyde resins as a compatibilizer for kenaf‐unsaturated polyester composites

Kenaf fiber‐reinforced unsaturated polyester (UPE) composites were prepared by compression molding. A novel compatibilizer was prepared from melamine, formaldehyde, and acrylamide. The treatment of kenaf fibers with the compatibilizer significantly increased the flexural properties and reduced the water uptake of the resulting kenaf–UPE composites. The effects of the total solids content, the molar ratios of melamine/formaldehyde/acrylamide, and the pH value of the compatibilizer solution in the treatment of kenaf fibers on the flexural strength, flexural modulus, as well as the water uptake of the kenaf–UPE composites were studied in detail. Fourier transform infrared spectra revealed that the compatibilizer was covalently bonded to kenaf fibers. Scanning electron microscopy images of the fractured kenaf–UPE composites confirmed that the treatment of kenaf fibers with the compatibilizer improved the interfacial adhesion between kenaf fibers and UPE resin. The mechanisms for the improved flexural properties and the reduced water uptake by the treatments of the kenaf fibers were proposed and discussed. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

A comparison study of lignocellulosic–thermoplastic composites prepared from different compounding techniques

A comparison study was carried out to determine the effect of different types of compounding technique, i.e., internal mixer, twin screw extruder, and high speed mixer in the preparation of kenaf‐polypropylene composite. The effect of percentage kenaf loading and particle size of kenaf (core) on the flexural properties of the composite was investigated. From the results, the incorporation of kenaf, regardless of particle size had resulted in the reduction of flexural strength of the composite. However, flexural modulus of the composites increased as the percentage of kenaf loading was increased due to the increasing of the stiffness contributed by kenaf fiber. Composites produced from internal mixer had displayed higher flexural properties as compared to those prepared from high speed mixer and twin screw extruder. It was believed that this phenomenon was attributed to the effectiveness of internal mixer with a better compounding mechanism which improved the wetting and distribution on kenaf within the polypropylene matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of Surface Treatments on Mechanical Properties and Water Resistance of Kenaf Fiber-Reinforced Unsaturated Polyester Composites

Abstract

Effects of surface treatments on the strength and water resistance of kenaf fiber-reinforced unsaturated polyester (UPE) composites were investigated. A new coupling agent that consists of 1,6-diisocyanato-hexane (DIH) and 2-hydroxylethyl acrylate (HEA) was investigated for surface treatments of kenaf fibers. The surface treatments were found to significantly enhance the tensile strength, modulus of rupture, modulus of elasticity, and water resistance of the resulting kenaf–UPE composites. Fourier transform infrared spectroscopy (FTIR) confirmed that DIH-HEA was covalently bonded onto kenaf fibers. Scanning electron microscopy (SEM) images of the composites revealed that chemical treatment of kenaf fibers with a combination of DIH and HEA improved the interfacial adhesion between kenaf fibers and UPE resin in the DIH–HEA-treated kenaf–UPE composites. The mechanisms by which the chemical treatment of kenaf fiber surfaces improved strength and water resistance of the resulting kenaf–UPE composites were discussed.     

FRP composites based on different types of glass fibers and matrix resins: A comparative study

Flexural properties, impact energy, heat deflection temperature, and resistance to thermal and hydrothermal degradation of composites based on E-glass and N-glass fibers as the reinforcing agents, and epoxy, unsaturated polyester, phenolic, and epoxy-phenolic resin systems as the matrix materials were studied and compared. As a reinforcing agent E-glass fiber is superior to N-glass fiber, particularly with respect to development of flexural strength and modulus, impact strength, and thermal resistance; N-glass fiber, however, imparts to the composites substantially higher resistance to hydrothermal degradation under boiling conditions in different chemical environments. For use of both E-glass and N-glass fibers as reinforcing agents, the general order of resistance to hydrothermal degradation for the composites based on different matrix resins is epoxy > phenolic > unsaturated polyester resin. Incorporation of a low dose of a rubbery polymer, such as styrene butadiene rubber (0.1–0.2%) and liquid polybutadiene (0.5–0.75%), in unsaturated polyester resin as the matrix resin measurably enhances impact energy of the composite. © 1995 John Wiley & Sons, Inc.     

A Preliminary Study on Ultraviolet Radiation–Cured Biofiber Composites from Oil Palm Empty Fruit Bunch

Biofiber composites, cured by ultraviolet (UV) radiation were produced using pulp made from empty fruit bunch (EFB) as the reinforcing agent and unsaturated polyester as the matrix. The EFB fibers were treated with sodium hydroxide (NaOH) solutions. The kappa number of the EFB decreased as the NaOH concentration increased. The flexural and tensile strength of the composites made from 22% NaOH-treated EFB increased as the percentage of EFB increased. Composites with 28% NaOH treated EFB had lower strength as the percentage of EFB increased. Generally, those with EFB fibers treated with 22% 15 NaOH displayed higher flexural, tensile, and impact strength and tensile modulus than those with 28% NaOH-treated fibers. No significant difference was observed for both types of composite with respect to flexural modulus and elongation at break.     

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     

Resin transfer molding of natural fiber reinforced polybenzoxazine composities

Kenaf fiber is incorporated in a polybenzoxazine (PBZX) resin matrix to form a unidirectionally reinforced composite containing 20 wt% fiber by a resin transfer molding technique. Two types of benzoxazine monomer are synthesized and used as resin mixtures: Benzozazines based on bisphenol‐A/aniline (BA‐a) and phenol/aniline (Ph‐a). The effects of varying BA‐a:Ph‐a ratio in the resin mixture and curing conditions on mechanical properties of pure PBZX resin and kenaf/PBZX composites are studies. The Flexural strength of the pure PBZX resin increases with increasing ratio of BA‐a:Ph‐a, curing temperature and curing time, but the impact strength increases only slightly. PBZX resin has lower water absorption and higher flexural modulus, when compared with unsaturated polyester (UPE) resin. PBZX composites with 20 wt% fiber content have lower flexural and impact strengths, but higher moduli compared with UPE composites with the same fiber content.     

Synthesis and mechanical properties of unsaturated polyester based nanocomposites

Two classes of nanocomposites were synthesized using an unsaturated polyester resin as the matrix and sodium montmorillonite as well as an organically modified montmorillonite as the reinforcing agents. X‐ray diffraction pattern of the composites showed that the interlayer spacing of the modified montmorillonite expanded from 1.25 nm to 4.5 nm, indicating intercalation. Glass transition values of these composites increased from 72°C, in the unfilled unsaturated polyester, to 86°C in the composite with 10% organically modified montmorillonite. From Scanning Electron Microscopy, it is seen that the degree of intercalation/exfoliation of the modified montmorillonite is higher than in the unmodified one. The mechanical properties also supported these findings, since in general, the tensile modulus, tensile strength, flexural modulus, flexural strength and impact strength of the composites with modified montmorillonite were higher than the corresponding properties of the composites with unmodified montmorillonite. The tensile modulus, tensile strength, flexural modulus and flexural strength values showed a maximum, whereas the impact strength exhibited a minimum at approximately 3–5 wt% modified montmorillonite content. These results imply that the level of exfoliation may also exhibit a maximum with respect to the modified montmorillonite content. The level of improvement in the mechanical properties was substantial. Adding only 3 wt% organically modified clay improved the flexural modulus of unsaturated polyester by 35%. The tensile modulus of unsaturated polyester was also improved by 17% at 5 wt% of organically modified clay loading.     

Non‐traditional lightweight polypropylene composites reinforced with milkweed floss

Lightweight composites are preferred for automotive applications due to the weight restrictions and also due to the presence of inherent voids that can enhance the sound absorption of these composites. The density of the reinforcing materials plays a crucial role in such lightweight composites. Milkweed is a unique natural cellulose fiber that has a completely hollow center and low density (0.9 g cm^?3) unlike any other natural cellulose fiber. The low density of milkweed fibers will allow the incorporation of higher amounts of fiber per unit weight of a composite, which is expected to lead to lightweight composites with better properties. Polypropylene (PP) composites reinforced with milkweed fibers have much better flexural and tensile properties than similar PP composites reinforced with kenaf fibers. Milkweed fiber‐reinforced composites have much higher strength but are stiffer than kenaf fiber‐reinforced PP composites. Increasing the proportion of milkweed in the composites from 35 to 50% increases the flexural strength but decreases the tensile strength. The low density of milkweed fibers allows the incorporation of higher amounts of fibers per unit weight of the composites and hence provides better properties compared to composites reinforced with common cellulose fibers with relatively high density. This research shows that low‐density reinforcing materials can more efficiently reinforce lightweight composites. Copyright © 2010 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     

Chemical treatment of wood fiber and its reinforced unsaturated polyester composites

In order to enhance the interfacial adhesion between wood fiber and an unsaturated polyester matrix (UPE), acrylic acid (acrylic acid)/poly(methyl methacrylate), and (acrylic acid)/silanization (AAS) were used to treat the wood fibers. The mechanical properties and the impact fracture surfaces of the prepared composites were measured and characterized, and the fracture mechanism of these kinds of composites was analyzed. The results showed that the AAS composites possessed the optimum comprehensive mechanical properties. When the weight fraction of wood fiber was 16%, the flexural strength and flexural modulus of the AAS composites were increased by 28.9 and 51.8%, respectively, compared to those of untreated composites. The highest tensile strength and lowest water absorption were also noted for AAS composites. These composites possessed the strongest interfacial adhesion between wood fiber and the UPE matrix. J. VINYL ADDIT. TECHNOL., 19:18–24, 2013. © 2013 Society of Plastics Engineers     

Effects of alkalization on tensile,impact, and fatigue properties of hemp fiber composites

The effects of alkalization surface treatment on hemp fiber properties and the properties of hemp fiber–reinforced polyester composites have been studied. Hemp fibers were exposed to 1, 5, and 10% sodium hydroxide (NaOH) solutions. The tensile properties and interfacial shear strength of all alkalized fibers were found to lie within the range of nonalkalized fibers. Laminates were made of alkalized fibers with unsaturated polyester resin, using hand lay‐up and compression moulding. Alkalization of fibers at low concentrations of 1 and 5% resulted in improvements in tensile and fatigue properties of composites made from these fibers, but no such improvements were observed for 10% alkalized fiber composites. The improvements were attributed to improvement in fiber/matrix bonding after this treatment, which was also confirmed by scanning electron microscopy images. No improvement in impact damage tolerance was observed for any of these three alkalized fiber composites. Immersion in distilled water reduced water absorption compared with nonalkalized fiber composites; however, the tensile properties in water were similar to those for nonalkalized fiber composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

The Physical Properties of Oil Palm Empty Fruit Bunch (EFB) Composites Made from Various Thermoplastics

Abstract

Oil palm empty fruit bunch (EFB)-based composites were produced using different types of thermoplastic as matrices. The composites were produced by using an internal mixer. The mechanical and water absorption properties of composites were investigated. Overall, the incorporation of EFB into the polymer matrix has resulted in the reduction of flexural strength. The poor performance has been attributed to the poor filler-matrix interaction. Both flexural and tensile modulus of PE and PP composites have been improved upon the addition of fillers, however, both PS and PVC composites showed a decreasing trend. Tensile strength and elongation at break results for all composites have been reduced as the result of incorporation of filler. This has been attributed to the poor filler-matrix interaction or compatibility, size irregularity and also decreased ductile deformation. Water absorption and thickness swelling increased as the filler loading is increased. This has been attributed to the presence of hyrophillic hydroxyl groups of the filler.     

The effect of glycidyl methacrylate treatment of empty fruit bunch (EFB) on the properties of ultra‐violet radiation cured EFB‐unsaturated polyester composite

In this study, biofiber composites cured by ultra‐violet, were produced using pulp made from empty fruit bunch (EFB) as the reinforcing agent and unsaturated polyester as the matrix. The conversion of EFB fibers into pulp was carried out using organosolv pulping process. The EFB pulp was then chemically treated with glycidyl methacrylate (GMA) to different percentage of weight percent gain and the composites were made with different percentages of pulp loading. Results showed that the Kappa number of EFB decreased as the NaOH concentration in organosolv pulping increased. Composites which were made from GMA‐treated EFB showed better mechanical properties (tensile, flexural, and impact strength) than those of the unmodified. Fourier transform infrared spectroscopy showed peaks that proved the occurrence of grafting between GMA and OH from EFB pulp. Scanning electron microscope analysis showed the evidence of the enhancement of the compatibility between EFB and matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polypropylene Hybrid Composites: A Preliminary Study on the use of Glass and Coconut Fiber as Reinforcements in Polypropylene Composites

Polypropylene hybrid composites were made using coconut and glass fibers as reinforcing agents in the polypropylene matrix. The incorporation of both fibers into the PP matrix has resulted in the reduction of flex-ural, tensile, and impact strengths and elongation at break. The reduction has been attributed to the increased incompatibility between the fibers and the PP matrix, and the irregularity in fiber size, especially for biofibers as shown by scanning electron micrographs. Both the flexural and tensile moduli have been improved with the increasing level of fiber loading. Most of the properties tested for Composites with high glass fibers/low biofiber loading are comparable with the ones with low glass fiber/high biofiber loading. The results show that more biofibers could be incorporated in hybrid composites which would give the same range of properties as the composites with higher loading of glass fibers.     

Effects of fiber extraction,morphology, and surface modification on the mechanical properties and water absorption of bamboo fibers‐unsaturated polyester composites

Bamboo fibers reinforced unsaturated polyester (UPE) composites were prepared by compression molding. Effects of fiber extraction, morphology, and chemical modification on the mechanical properties and water absorption of the bamboo fibers‐UPE composites were investigated. Results showed that the unidirectional original bamboo fibers resulting composites demonstrated the highest tensile strength, flexural strength, and flexural modulus; the 30–40 mesh bamboo particles resulting composites had the lowest tensile strength and flexural strength, but had comparable flexural modulus with that of chemical pulp fibers. The treatment of bamboo fibers with 1,6‐diisocyanatohexane (DIH) and 2‐hydroxyethyl acrylate (HEA) significantly increased the tensile strength, flexural strength and flexural modulus, and water resistance of the resulting composites. Fourier Transform Infrared and X‐ray photoelectron spectroscopy analyses showed that DIH and HEA were covalently bonded onto bamboo fibers. Scanning electron microscopic images of the fractured surfaces of the composites showed that the treatment of bamboo fibers greatly improved the interfacial adhesion between the fibers and UPE resins. The water absorption kinetics of the composites was also investigated; and the results showed that the water absorption of the composites fitted Fickian behavior well. POLYM. COMPOS., 37:1612–1619, 2016. © 2014 Society of Plastics Engineers     

Replacement of styrene with acrylated epoxidized soybean oil in an unsaturated polyester resin from propylene glycol,isophthalic acid,and maleic anhydride

Commercial unsaturated polyester (UPE) resins typically contain a high amount of volatile toxic styrene. A non‐volatile acrylated epoxidized soybean oil (AESO) was found to be an excellent replacement of styrene in a commercially available UPE resin [designated as Styrene‐(PG‐IPA‐MA)] that is derived from propylene glycol (PG), isophthalic acid (IPA), and maleic anhydride (MA) in terms of the mechanical properties of the resulting kenaf fiber‐reinforced composites. The AESO‐(PG‐IPA‐MA) resins had low viscosity and long pot life below 70°C for a typical fiber‐reinforced composite application. AESO and PG‐IPA‐MA were not able to form a strong polymer matrix individually for fiber‐reinforced composites. However, a combination of AESO and PG‐IPA‐MA saw strong synergistic effects between them. The flexural, tensile, and water absorption properties of kenaf fiber‐reinforced composites made from AESO‐(PG‐IPA‐MA) resins were comparable with or even superior to those from the Styrene‐(PG‐IPA‐MA) resin. The AESO/(PG‐IPA‐MA) weight ratio was investigated for maximizing the mechanical properties of the kenaf fiber‐reinforced composites. The curing mechanism of the AESO‐(PG‐IPA‐MA) resins is discussed in detail. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43052.