Effect of coir fiber content and compatibilizer on the properties of unidirectional coir fiber/polypropylene composites

The main objective of this research was to study the effect of fiber content variation and stearic acid (SA) treatment on the fundamental properties of unidirectional coir fiber (CF) reinforced polypropylene (PP) composites. Several percentages of filler contents were used (10–40 wt %) in order to gain insights into the effect of filler content on the properties of the composites. Coir/PP composites were fabricated by compression molding, and the properties of composites were studied by physico-mechanical and thermal properties. The results from mechanical properties such as tensile strength (TS), tensile modulus (TM) and impact strength (IS) of the CF/PP composites were found to be increased with increasing fiber content, reached an optimum and thereafter decreased with further increase in fiber content. Treatment of the coir with SA as the coupling agent enhanced the mechanical properties, crystallization temperature and crystallinity of virgin PP and water desorption of the resulting composites, resulting from the improved adhesion between the CF and PP matrix. Scanning electron micrographs (SEM) of the tensile fractured samples showed improved adhesion between fiber and matrix upon treatment with SA. Interfacial shear strength (IFSS) of the composites was measured by single fiber fragmentation test (SFFT).     

Coir fiber reinforced polypropylene composite panel for automotive interior applications

In this study, physical, mechanical, and flammability properties of coconut fiber reinforced polypropylene (PP) composite panels were evaluated. Four levels of the coir fiber content (40, 50, 60, and 70 % based on the composition by weight) were mixed with the PP powder and a coupling agent, 3 wt % maleic anhydride grafted PP (MAPP) powder. The water resistance and the internal bond strength of the composites were negatively influenced by increasing coir fiber content. However, the flexural strength, the tensile strength, and the hardness of the composites improved with increasing the coir fiber content up to 60 wt %. The flame retardancy of the composites improved with increasing coir fiber content. The results suggest that an optimal composite panel formulation for automotive interior applications is a mixture of 60 wt % coir fiber, 37 wt % PP powder, and 3 wt % MAPP.     

Evaluating the Mechanical Behavior of Basalt Fibers/Epoxy Composites Containing Surface-modified CaCO<Subscript>3</Subscript> Nanoparticles

Polymer matrix composites (PMCs) owing to their outstanding properties such as high strength, low weight, high thermal stability and chemical resistance are broadly utilized in various industries. In the present work, the influence of silanized CaCO₃ (S-CaCO₃) with 3-aminopropyltrimethoxysilane (3-APTMS) coupling agent at different values (0, 1, 3 and 5 wt.% with respect to the matrix) on the mechanical behavior of basalt fibers (BF)/epoxy composites was examined. BF-reinforced composites were fabricated via hand lay-up technique. Experimental results from three-point bending and tensile tests showed that with the dispersion of 3 wt.% S-CaCO₃, flexural strength, flexural modulus, tensile strength and tensile modulus enhanced by 28 %, 35 %, 20 % and 30 %, respectively. Microscopic examinations revealed that the development of the mechanical properties of fibrous composites with the incorporation of modified CaCO₃ was related to enhancement in the load transfer between the nanocomposite matrix and BF as well as enhanced mechanical properties of the matrix part.     

Effect of co-monomer ratio in ABS and wood content on processing and properties in wood/ABS composites

Acrylonitrile-Butadiene-Styrene copolymers (ABS) reinforced with wood flour were investigated for rheological, mechanical and thermal properties. Three grades of commercial ABS resin (high flow (HF-ABS), medium impact (MI-ABS) and super high impact (SI-ABS) grades) were characterized using H-NMR and elemental analysis for the determination of co-monomer content. Wood flour from Para rubber trees treated with N-2 (aminoethyl)-3-(aminopropyl) trimethoxy silane was blended with ABS in the melt blending process using a twin-screw extruder. Wood flour contents used in this work were 0.0 %, 9.1 %, and 33.3 % wt. The composites with higher acrylonitrile contents showed higher melt viscosity especially at the low shear rate. Carreau’s model was used for curve-fitting. The extrudate swell ratio of the composites tended to increase at the shear rate of 10–500 s⁻¹ and then decreased dramatically once the shear rate were further applied. Neat ABS and wood/ABS composites with higher butadiene content illustrated a higher swelling ratio. The neat MI-ABS and composites showed the highest ultimate tensile strength and modulus due to the butadiene content effect. As the wood flour loading was increased, the tensile modulus of all ABS composites increased with the sacrifice of the tensile strength of composites. The elongation at break and impact strength were noticeably the highest for wood/SI-ABS composites among all because of the effect of rubbery butadiene content. Thermal stability of plastic in 9.1 % wood in HF-ABS composites was improved compared with the neat HF-ABS due to the low acrylonitrile content.     

A study on mechanical,thermal and environmental degradation characteristics of N,N-dimethylaniline treated jute fabric-reinforced polypropylene composites

The mechanical and thermal behavior of compression molded jute/polypropylene (PP) composites were studied by evaluating tensile strength (TS), bending strength (BS), tensile modulus (TM), bending modulus (BM), impact strength (IS), thermogravimetric (TG/DTG) and differential thermal analysis (DTA). A chemical modification was made to jute fabrics using N,N-Dimethylaniline (DMA) in order to improve the interfacial adhesion between the fabrics and matrix. It was found that jute fabrics on treatment with N,N-Dimethylaniline (DMA) significantly improved the mechanical properties of the composites. Thermal analytical data of PP, both treated and untreated jute fabrics as well as composites revealed that DMA treatment increased the thermal stability of the fabrics and composite. DMA treatment also reduced the hydrophilic nature of the composite. DMA treated jute composite was found less degradable than control composite under water, soil and simulated weathering conditions.     

Mechanical behavior of composites reinforced with fibers caroa

Composites were prepared with 13, 23 30 and 40 % fiber and evaluated the mechanical performance in tensile, flexural and impact. The mechanical properties of these composites were also evaluated function of time at 110 °C thermal exposure. Caroa fibers were characterized by techniques such as thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the best mechanical properties were achieved for composites containing 23 to 30 % fiber. The incorporation of 23 % fiber caroa increased both the modulus of elasticity in the tensile test as the flexural strength and impact, the composite with 30 % fiber caroa showed higher tensile strength. The results show that the tensile and flexural strength of the composite decreased with time of thermal exposure. The thermal aging at 110 °C caused a decrease in tensile properties of the composites.     

Effect of nanoclay and magnesium hydroxide on some properties of HDPE/wheat straw composites

Since natural fiber/polymer composites are increasingly used, the development of safe and environmental friendly flame retarding bio-based composites is of great importance. But this issue must maintain the mechanical performance of these composites. To study these objectives, four levels of magnesium hydroxide Mg(OH)₂ of (0, 10, 20, 30 phc) and two levels of nanoclay (0, 3 phc) were considered and incorporated into HDPE/wheat straw composites. Maleic anhydride grafted polyethylene (PE-g-MA) was also used as a compatibilizer at constant content. The samples were prepared by melt compounding and injection molding processes, respectively. The some properties of samples including burning rate and mechanical properties (tensile and impact strengths) were tested based on the ASTM standard. The results showed that the burning rate of samples decreased with increasing the nanoclay and Mg(OH)₂ content. The tensile and impact strengths showed a marginal reduction by adding Mg(OH)₂ from 10 phc to 30 phc and the tensile modulus and impact strength revealed an increase by increasing the amount of nanoclay up to 3 phc. Generally, these results confirmed that the fire retarding and mechanical properties of HDPE/wheat straw composites could be significantly improved with an appropriate combination of the nanoclay and Mg(OH)₂ in the composites.     

Polypropylene/high-density polyethylene/carbon fiber composites: Manufacturing techniques,mechanical properties,and electromagnetic interference shielding effectiveness

This study uses polypropylene (PP)/high-density polyethylene (HDPE) polyblends (80/20 wt.%) as matrices, which are then melt-blended with inorganic carbon fibers (CF) as reinforcement to form electrically conductive PP/HDPE composites. Tensile test, flexural test, Izod impact test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) are performed to evaluate different physical properties of samples. A surface resistance and electromagnetic interference shielding effectiveness (EMI SE) measurements are used to evaluate the electrical properties of the PP/HDPE/CF composites. Test results show that an increasing content of carbon fibers results in an 18 %, 23 %, and 60 % higher tensile strength, flexural strength, and impact strength, respectively. SEM results show that carbon fibers break as a result of applied force, thereby bearing the force and increasing the mechanical properties of composites. DSC and XRD results show that the addition of carbon fibers causes heterogeneous nucleation in PP/HDPE polyblends, thereby increasing crystallization temperature. However, the crystalline structure of PP/HDPE composites is not affected. Surface resistivity results show that 5 wt.% of carbon fibers can form a conductive network in PP/HDPE polyblends and reduce the surface resistivity from 12×10¹² ohm/sq to 4×10³ ohm/sq. EMI SE results show that, with a 20 wt.% CF and a frequency of 2-3 GHz, the average EMI SE of PP/HDPE/CF composites is between -48 and -52 dB, qualifying their use for EMI SE, which is required for standard electronic devices.     

Nano-SiO2 filled rice husk/polypropylene composites: Physico-mechanical properties

In this research, reinforcing effect of hybrid filler including rice husk (RH), beech bark (BB) and nano-SiO₂, in polypropylene has been investigated. In the sample preparation, four levels of filler loading were used for waste lignocellulosic materials (55-58 wt.%) and nano-SiO₂ (0-4 wt.%). In order to increase the interphase adhesion, polypropylene grafted with maleic anhydride was added as a coupling agent to all the composites studied. The physical properties, viz. the thickness swelling and water absorption, and mechanical properties, namely, the tensile, flexural and notched Izod impact strengths, of the composites were determined. Generally, high amount of filler content in composites can lead to the reduction of interfacial adhesion between matrix polymer and filler, and it limits their applications. The results showed that while flexural properties and elongation at break were moderately improved by the increase in the amount of filler in the matrix, tensile and Izod impact strengths decreased dramatically. However, the composites had acceptable mechanical strength levels. The mechanical properties of composites filled with RH are generally greater than BB composites. The thickness swelling and water absorption of the composites increased with the increase in the filler loading, but to a negligible extent as compared with the wood-based composites and the solid woods. Nano-SiO₂ addition showed little positive effect on the mechanical properties. It can be concluded from this study that the used waste lignocellulosic materials are attractive reinforcements from the standpoint of their physico-mechanical properties.     

Strawboard from vapor phase acetylation of wheat straw☆

Commercial ground wheat straw was used in a central composite response surface experimental design to examine four acetylating process variables: reaction temperature, reaction time, initial moisture content of straw, and the vapor flow rate of chemical reagent. The response variable was acetyl content determined as a function of straw weight gain. Diphenylmethyane diisocyante was used as a binder to prepare board samples with a hot press. Equilibrium moisture content (EMC) was determined at 65 and 90% RH at 27°C, and dimensional stability was determined using a humidity cycle of 30–90% RH at 27°C. ASTM D1037-93 standard method for a 3-point flex test was used to measure mechanical properties. The microstructures of both treated and untreated wheat straw and boards were observed with a scanning electron microscope. The vapor phase acetylation system used acetylated ground wheat straw to a 24% weight gain (dry weight basis). A mathematical model (R²=0.97) was developed to predict the weight gain as a function of the four acetylation processing variables. The maximum reduction in all strawboard properties occurred at the highest weight gain (24%). The strawboard EMC decreased (30% maximum reduction) as weight gain increased at both 65 and 90% RH. The strawboard dimensional stability increased as the weight gain increased (maximum reductions of 80% in thickness swell and 50% in linear expansion). The initial mechanical properties of the strawboards decreased as the weight gain increased (maximum reductions of 64% in strength and 48% in stiffness). The density of the strawboards decreased as the weight gain increased (23% maximum reduction). SEM micrographs showed no physical evidence of structural damage to cell walls from the acetylation.     

Mechanical and thermal properties of recycled poly(ethylene terephthalate) reinforced newspaper fiber composites

This study presents the mechanical and thermal properties of environment-friendly composites made from recycled newspaper fibers reinforced recycled poly(ethylene terephthalate) (rPET) resin with the addition of styrene-ethylene-butylene-styrene grafted maleic anhydride (SEBS-g-MA) as compatibilizer. The effect of SEBS-g-MA addition (i.e., 10 phr) by using a twin-screw extruder to the rPET resin, followed by different fiber content (5, 10 and 15 wt.%) on the tensile, flexural and impact properties of the composites were determined. Stiffness of composites increased significantly compared to those of rPET/SEBS-g-MA blend. Fiber addition resulted in moderate increases in both tensile and flexural strength of the composites. Scanning electron microscope (SEM) photomicrographs of the impact fracture surfaces demonstrate good adhesion at 5 and 10 % fiber content. Differential scanning calorimetry (DSC) showed that the presence of newspaper fibers enhanced the nonisothermal crystallization kinetics and crystallinity. Thermal stability of the composites was improved as indicated by thermogravimetric analysis (TGA).     

A comparison of flax shive and extracted flax shive reinforced PP composites

In this study, flax shive (FS) and extracted flax shive (EFS) were fully characterized. The results showed that EFS presented lower noncellulose content, smaller porous tunnels and better thermal stability than FS. The 5 % weight loss temperature of EFS was over 200 °C, which can meet the requirements of the processing conditions for the natural fiber reinforced polymer composites. Consequently, the flax shive and extracted flax shive reinforced PP composites were prepared and characterized. It was found that the thermal stability of EFS/PP composites was better than that of FS/PP composites, and both FS and EFS behaved as nucleation agents, which could accelerate the crystallization process of PP in the composites. Mechanical test showed that EFS could be used as a reinforcing material for PP composite when compatibilizer was applied. The flexural strength and modulus of the composites containing 30 % EFS were about 8 % and 100 % higher than that of pure polypropylene, respectively.     

Chitosan-filled polypropylene composites: The effect of filler loading and organosolv lignin on mechanical,morphological and thermal properties

In this work, the effect of organosolv lignin on properties of polypropylene (PP)/chitosan composites was investigated. Mechanical and thermal properties of the composites were analyzed by means of ASTM D 638-91, ASTM D 256, thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Tensile strength and elongation at break of the PP composites decreased upon the presence of chitosan filler, but Young’s modulus improved. Impact strength was found to increase with the maximum value at 30 php of filler loading. At a similar loading, treated PP/chitosan composites were found to have higher tensile strength, elongation at break, Young’s modulus as well as impact strength than untreated composites. Furthermore, the presence of organosolv lignin imparted a plasticizing effect. Thermal properties of the treated PP/chitosan composites were better as compared with the untreated PP/chitosan composites; although the chemical treatment did not alter the thermal degradation mechanism. In addition, the obtained results were comparable to results from previous studies. This finding implied that the organosolv lignin could be a potential reagent to replace its synthetic counterpart.     

Effect of mercerization on mechanical, thermal and degradation characteristics of jute fabric-reinforced polypropylene composites

Jute fabric reinforced polypropylene composites were fabricated by compression molding technique. Fiber content in the composites was optimized at 45 % by weight of fiber by evaluating the mechanical parameters such as tensile strength, tensile modulus, bending strength, bending modulus. Surface treatment of jute fabrics was carried out by mercerizing jute fabrics with aqueous solutions of NaOH (5, 10 and 20 %) at different soaking times (30, 60 and 90 mins) and temperatures (0, 30 and 70 °C). The effect of mercerization on weight and dimension of jute fabrics was studied. Mechanical properties of mercerized jute-PP composites were measured and found highest at 20 % NaOH at 0 °C for 60 min soaking time. Thermal analytical data from thermogravimetric and differential thermal analysis showed that mercerized jute-PP composite achieved higher thermal stability compared to PP, jute fabrics and control composite. Degradation characteristics of the composites were studied in soil, water and simulated weathering conditions. Water uptake of the composites was also investigated.     

Characterization of plant and animal based natural fibers reinforced polypropylene composites and their comparative study

Natural fibers are largely divided into two categories depending on their origin: plant based and animal based. Plant based natural jute fiber reinforced polypropylene (PP) matrix composites (20 wt% fiber) were fabricated by compression molding. Bending strength (BS), bending modulus (BM), tensile strength (TS), Young’s modulus (YM), and impact strength (IS) of the composites were found 44.2 MPa, 2200 MPa, 41.3 MPa, 750 MPa and 12 kJ/m², respectively. Animal based natural B. mori silk fiber reinforced polypropylene (PP) matrix composites (20 wt% fiber) were fabricated in the same way and the mechanical properties were compared over the silk based composites. TS, YM, BS, BM, IS of silk fiber reinforced polypropylene composites were found 55.6 MPa, 760 MPa, 57.1 MPa, 3320 MPa and 17 kJ/m² respectively. Degradation of composites in soil was measured upto twelve weeks. It was found that plant based jute fiber/PP composite losses its strength more than animal based silk fiber/PP composite for the same period of time. The comparative study makes it clear that mechanical properties of silk/PP composites are greater than those values of jute/PP composites. But jute/PP composites are more degradable than silk/PP composites i.e., silk/PP composites retain their strength for a longer period than jute/PP composites.     

Influence of fibre contents on mechanical and thermal properties of roselle fibre reinforced polyurethane composites

The aim of this paper is to study the effect of fibre content on mechanical and morphological properties and thermal stability of roselle fibres (RFs) reinforced polyurethane (TPU) composites. The RF/TPU composites were prepared at difference fibre contents; 10, 20, 30, 40 and 50 wt% by melt mixed mixer and hot press at 170 °C. Mechanical (tensile, flexural and impact strength) and Thermogravimetric analysis (TGA) properties of RF/TPU composites were measured according to ASTM standard. Obtained results indicated that effect of fibre contents display improved tensile and flexural and impact strength properties. RF/TPU composites show the best mechanical and thermal properties at 40 wt% roselle fibre content. Scanning electron microscopy (SEM) micrograph of fractured tensile sample of the roselle composite revealed good fibre/matrix bonding. TGA showed that RF/TPU with difference fibre contents had improved thermal stability.     

Compatibilizing effects of polypropylene-g-itaconic acid on the polypropylene composites

We prepared long carbon fiber (LCF)-reinforced thermoplastic composites using a compatibilizer of itaconic acid grafted polypropylene (PP-g-IA). We confirmed the structure of PP-g-IA and investigated the compatibilizing effects of PPg- IA on LCF/polypropylene composites. The tensile strength, tensile moduli, flexural strength, and flexural moduli of the composites increased with increasing PP-g-IA content in the thermoplastic composites. Using single pull-out analyzing system, we found PP-g-IA improved interfacial strength between the carbon fiber and PP matrix. The thermal properties of the composites were measured by thermogravimetric analysis (TGA). We could observe that LCF enhanced the mechanical properties and thermal decomposition temperature of the polypropylene (PP) composites, compared with neat PP. The fractured surfaces of PP/PP-g-IA/LCF composites showed that PP-g-IA was effective for improving the interfacial adhesion between LCF and PP matrix.     

Flexural and impact properties of chemically treated sugar palm fiber reinforced high impact polystyrene composites

The effects of chemical treatment on the flexural and impact properties of sugar palm fiber reinforced high impact polystyrene (HIPS) composites were studied. Two types of concentration of alkali solution (4 % and 6 %) and also two types of percentage of compatibilizing agent (2 % and 3 %) have been used in this study. The alkaline treatment is carried out by immersing the fibers in 4 % and 6 % of alkali solution for 1 hour. A 40 wt. % of alkali treated sugar palm fiber (SPF) was blended with HIPS using Brabender machine at temperature of 165 °C. The second treatment was employed by compounding mixture of sugar palm fibers and HIPS with 2 and 3 % of compatibilizing agent using the same procedure. The composites plate with dimensions of 150×150×3 mm was produced by using the hot press machine. The flexural strength, flexural modulus and impact strength of composites were measured and the values were compared to the untreated composites. Improvement of the mechanical properties of the composites has been shown successfully. Alkali treatment using 6 % NaOH solution improve the flexural strength, flexural modulus and impact strength of the composites as amount 12 %, 19 % and 34 % respectively, whereas compatibilizing agent treatment only showed the improvement on the impact strength, i.e. 6 % and 16 % improvement for 2 % and 3 % MAH respectively.     

Effects of heat treatment on the properties of bamboo fiber/polypropylene composites

In this paper, the effects of heat treated parameters on the properties of bamboo fiber (BF) / polypropylene (PP) composites were investigated. The crystallization properties of BF/PP composites after heat treatment were characterized by differential scanning calorimetry (DSC), and the mechanical properties were measured. The results showed that the crystallinities of the heat treated composite were enhanced compared with that of the untreated. When the heat treated time was 30 mins, the crystallinities became almost unchanged. However, the crystallinity decreased after 12 h heat treatment. In addition, when the heat treated temperature was above 90 °C, the higher the temperature was, the higher the crystallinities became. Moreover, the tensile strengths of BF/PP composites increased and then decreased with increasing heat treated time, while the impact strengths had a decreasing trend. In the meanwhile, the tensile strengths increased but the impact strengths decreased as the heat temperature increased.     

A novel strategy for the preparation of bamboo fiber reinforced polypropylene composites

In this paper, a novel strategy was used to prepare the bamboo fiber (BF)/polypropylene (PP) composites which greatly improved the distribution of BF. Both the raw and alkali treated BF were utilized for the fabrication of composites and silane coupling agent was used to improve the adhesion of BF and PP. The effects of BF content and the alkali treatment of BF on mechanical, thermal, morphological, dynamic mechanical properties and water absorption were studied. The Fourier transform infrared spectroscopy (FT-IR) analysis indicated that the hydrophilic nature of raw BF was significantly reduced by alkali treatment. In addition, the mechanical properties and the water absorption of the composites were found to increase with the increment of BF loading. Most importantly, the mechanical properties of the alkali treated BF showed much higher values than that of raw BF while the water absorption of alkali treated BF was much lower than that of raw BF. The results indicated the interaction of fiber-matrix was greatly improved by the alkali treatment. Moreover, from the Scanning Electron Microscopy (SEM) images, it further proved that the distribution of BF was improved by the way of papermaking to premix BF and PP fiber. The Dynamic mechanical thermal analysis (DMA) results showed that the storage modulus of the composites was increased with further increase in BF content.