Fabrication of long and discontinuous natural fiber reinforced polypropylene biocomposites and their mechanical properties

Natural fiber reinforced polypropylene (PP) biocomposites were fabricated by blending long-and-discontinuous (LD) natural fibers (NF) with LD PP fibers. Firstly, random fiber mats were prepared by mixing NFs and PP fibers using a carding process. Then, heat and pressure were applied to the mats, such that the PP fibers dispersed in the mats melted and flowed out, resulting in the formation of consolidated sheets upon subsequent cooling. The effect of the fiber volume fraction on the mechanical properties of the bio-composites was scrutinized by carrying out tensile and flexural tests and observing the interface between the fiber and matrix. It was observed that the natural LD fiber content needs to be maintained at less than the nominal fiber fraction of 40 % by weight for the composites fabricated using the current method, which is quite low compared to that of continuous or short fiber reinforced composites. The limited fiber fraction can be explained by the void content in the biocomposites, which may be caused by the non-uniform packing or the deficiency of the matrix PP fibers.     

Characterization of oil palm empty fruit bunch and glass fibre reinforced recycled polypropylene hybrid composites

The effects of hybridization of glass fibre on oil palm empty fruit bunch (EFB) and recycled polypropylene-based composites are described in this paper. The compounding process involved extrusion followed by injection moulding technique to prepare the samples for characterizations. Fibre loading were considered as 40 % of the total weight of the blends and EFB:glass fibre ratio was maintained as 30:70, 50:50, 70:30 and 90:10. Two types of coupling agents of maleic anhydride-grafted polypropylene such as polybond-3200 and fusabond P-613 of different molecular weight and maleic anhydride level were used to improve the interfacial adhesion between the fibres and the matrix. Composites were characterized by density, melt flow index, tensile, Izod impact and flexural testing. Morphological images of the fractured surfaces of the composites were examined by field-emission scanning electron microscopy. Samples were also characterized by thermal tests such as thermogravimetric analysis and differential scanning calorimetry to evaluate the thermal and crystalline properties, respectively. Optimization of hybridization of the fibres and effect of coupling agents were evaluated in terms of various properties of the samples. The composite prepared with EFB:glass fibre ratio of 70:30 showed better reinforcing properties than that of others.     

A study of the mechanical properties of natural fibre reinforced composites

This paper presents the results of a current research of the tensile properties: ultimate strength and stiffness modulus in composites using natural reinforcements. Hemp short fibres and pine sawdust were randomly distributed in polypropylene matrices to produce composite plates with 5 mm thickness by injection moulding technique. The specimens were cut from these plates with bone dog shape or plane bars, and tested in tensile and four points bending, respectively. Stiffness modulus and ultimate stresses were obtained for different weight fraction content of reinforcement and discussed taking in account the failure modes. Four series of pine sawdust reinforced specimens were immersed in water in periods up to 20 days. Periodically, the specimens were removed from the water recipient and immediately tested. The damage effect of water immersion time was discussed based in the tensile results and in the water absorption curves.     

Batch foaming of short carbon fiber reinforced polypropylene composites

In this paper, the short carbon fiber (SCF)/PP composite foams with fine open cell were prepared with batch foaming technique using supercritical CO₂. The effects of SCF contents, saturation pressure and depressurization rate on the cell morphology were studied. The experimental results indicate that the cell morphology of foamed composites was significantly influenced by the SCF contents and saturation pressure. It is found that the cell size increased and cell density decreased with the increment of SCF contents while the saturation pressure had the opposite effect. However, depressurization rate showed little impacts on the cell morphology due to the presence of SCF.     

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.     

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.     

Basic properties of grain by-products and their viability in polypropylene composites

The objective was to study the potential of grain by-products (husk) of grains such as wheat (Triticum aestivum L; German name is Weizen) and rice (Oryza sativa) as reinforcements for thermoplastics as an alternative to or in combination with wood fibres. Prior to composites preparation, the chemical components of fibres such as cellulose, hemi-cellulose, lignin, starch, protein and fat were measured and the surface chemistry and functionality of grain by-products were studied using EDX and FT-IR. Structural constituents (cellulose, starch) were found in wheat husk (W) equal 42%, in rice husk 50% and in soft wood 42%, respectively. Thermal degradation characteristics, the bulk density, water absorption and the solubility index were also investigated. Wheat husk (W) and rice husk were found thermally stable at temperatures as low as 178 °C and 208 °C, respectively. The particle morphology and particle size were investigated using microscopy. Water absorption properties of the fibres were studied to evaluate the viability of these fibres as reinforcements. Polypropylene composites were fabricated using a high speed mixer and an ensuing injection moulding process with 40 wt% fibre. The tensile and Charpy impact strength of the resulting composites were investigated. The tensile elongation at break was found to 75% for wheat husk (W) composites and 23% for rice husk composites better than soft wood composites. Rice husk composites showed 13% better Charpy impact strength than soft wood composites. Due to coupling agent, tensile strength of composites found to improve 25% for soft wood, 35% for wheat husk (W) and 45% for rice husk.     

Mechanical and moisture absorption characterization of PLA composites reinforced with nano-coated flax fibers

This research is intended to improve the interface between the fibers and the matrix and limit water absorption of bio-based material thereby decreasing degradation of the composites when they are exposed to external environment such as high temperature and humidity. In this study, flax fibers were treated with an organic surface coating containing SiO₂ nanoparticles. This coating was a dispersion of silica fume in epoxy. One composite was also made with raw fibers as reference as well as one sample of pure PLA. Flax fibers/PLA composites were manufactured by hot pressing by stacking 4 PLA films and 3 pieces of flax fabric. Morphology and dispersion of the coating on the fibers was observed by scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Accelerated ageing was carried out on the 3 materials by placing them in a 50 °C water bath until saturation to investigate the influence of the coating on water diffusion. Mechanical properties of the different composites were investigated by tensile (before and after conditioning) and short beam shear (SBS) testing in order to evaluate the impact of the coating on the interfacial properties of the materials. The results show that the fibers surface was homogenized and that a better adhesion was reached because of the coating. Coating the fibers also allowed the decrease in water uptake by more than 10 % and their protection during conditioning, preserving their mechanical properties.     

Mechanical properties of uniaxial natural fabric Grewia tilifolia reinforced epoxy based composites: Effects of chemical treatment

The effects of chemical treatment on the mechanical, morphological, and chemical resistance properties of uniaxial natural fabrics, Grewia tilifolia/epoxy composites, were studied. In order to enhance the interfacial bonding between the epoxy matrix and the Grewia tilifolia fabrics, two different types of treatment: alkali treatment (5 % NaOH) and (3-aminopropyl)-triethoxysilane coupling agent (CA), were used. The epoxy composites containing 0–15 wt% of Grewia tilifolia fabric were prepared by hand lay-up technique, at room temperature. The tensile and flexural properties of the untreated, alkali-treated and coupling agent treated Grewia tilifolia reinforced epoxy composites were determined as a function of fabric loading. The 9 % wt Grewia tilifolia fabric reinforced epoxy composites showed improved tensile and flexural modulii when compared to the neat epoxy matrix. Significant improvement in the mechanical properties was obtained when both alkali and coupling agent treated fabrics were used as reinforcement. Morphological studies demonstrated that better adhesion between the fabrics and the matrix was achieved especially when the alkali-treated and coupling agent treated Grewia tilifolia fabrics were used in the composites. For the water absorption and chemical resistance studies, various solvents, acids and alkalis were used on the epoxy composites. This study has shown that Grewia tilifolia fabric/epoxy composites are promising candidates for structural applications, where high strength and stiffness are required.     

Characterization of light weight epoxy composites from short Sansevieria Cylindrica fibers

Sansevieria (genus) cylindrica (species) belongs to Agavaceae family plant fiber first time used as a reinforcing agent in the epoxy system. Fibre extracted from leaves, fairly lesser density, porosity, higher strength to weight ratio (hereafter called SCF) and these fibers were alkali-treated and yet impregnated on the epoxy system using wet hand lay up technique in order to compare with untreated fiber on performance. DMA, TGA, DSC, FTIR, SEM, degradation temperature, flexural and tensile tests were performed for untreated and alkali-treated epoxy composites using different SCF volumes viz. 1 vol.%, 5 vol.%, 7 vol.% and 9 vol.%. Alkali treated fibre were found to have higher initial and final degradation temperatures and flexural and tensile strength. The removal of the amorphous hemi-cellulose on alkali treatment was played an instrumental in improving properties. A 3 °C increase in glass transition temperature and decomposition temperature were recorded respectively and over all treated SCF composites reinforced on the epoxy were shown significant results than untreated. Storage modulus and tan ?? were observed well at 9 vol.% treated SCF while flexural and tensile were increased by 35 and 13 % for SCF treated composites respectively.     

The statistical investigation of mechanical properties of PP/natural fibers composites

A systematic and statistical approach to evaluate and predict the properties of random discontinuous natural fiber reinforced composites. Different composites based on polypropylene and reinforced with natural fibers have been made and their mechanical properties are measured together with the distribution of the fiber size and the fiber diameter. The values obtained have been related to the theoretical predictions, using a combination of the Griffith theory for the effective properties of the natural fibers and the Halpin-Tsai equation for the elastic modulus of the composites. The relationships between experimental results and theoretical predictions are statistically analyzed using a probability density function estimation approach based on neural networks. The results show a more accurate expected value with respect to the traditional statistical function estimation approach. In order to point out the particular features of natural fibers, the same proposed method is also applied to PP-glass fiber composites.     

Evaluation of mechanical properties of jute/glass/carbon fibers reinforced hybrid composites

A study on the tensile and flexural properties of jute-glass-carbon fibers reinforced epoxy hybrid composites in inter-ply configuration is presented in this paper. Test specimens were manufactured by hand lay-up process and their tensile and flexural properties were obtained. The effects of the hybridization, different fibers content and plies stacking sequence on the mechanical properties of the tested hybrid composites were investigated. Two-parameter Weibull distribution function was used to statistically analyze the experimental results. The failure probability graphs for the tested composites were drawn. These graphs are important tools for helping the designers to understand and choose the suitable material for the required design and development. Results showed that the hybridization process can potentially improve the tensile and flexural properties of jute reinforced composite. The flexural strength decreases when partial laminas from a carbon/epoxy laminate are replaced by glass/epoxy or jute/epoxy laminas. Also, it is realized that incorporating high strength fibers to the outer layers of the composite leads to higher flexural resistance, whilst the order of the layers doesn’t affect the tensile properties.     

Characterization of castor oil/polycaprolactone polyurethane biocomposites reinforced with hemp fibers

Abstact  The thermal and mechanical properties of castor oil/polycaprolactone-based polyurethane (CPU) films and polyurethane biocomposites reinforced with hemp fibers (HCPU) were investigated. Although similar films can be synthesized from petroleum, the main interest in studying these biomass-based composites is based on the fact that both fiber and matrix are derived from renewable resources. In this study, castor oil was used as a polyol for polyurethane films and hemp fiber was used to reinforce the biocomposites. To control the mechanical properties of CPU and HCPU, polycaprolactone diol (PCL) was added to the polyol mixture. Varying the mixing ratio of castor oil and PCL, the thermal and mechanical properties of the CPU and HCPU samples were investigated by using FT-IR, DSC, DMTA, Minimat, and SEM. In an attempt to improve interfacial adhesion between the fiber and matrix biocomposites, hemp fiber was reacted with MDI. FE-SEM micrographs showed that the surface of the hemp fiber became smoother after reaction with MDI. Urethane bonding formation was confirmed by FT-IR.     

Direct manufacturing of flax fibers reinforced low melting point PET composites from nonwoven mats

There have been many interests in using natural fibers as substitutes for glass fibers to prepare fiber reinforced composites. Flax fibers, due to their specific strength, have been a hot issue in this field. The focus of this research work is to manufacture flax fiber reinforced low melting point PET composites directly from nonwoven mats. No consolidation methods are applied to the carded nonwoven mats before the hot-press molding. The effects of operating parameters like carding method, molding temperature, molding time, etc. on the mechanical properties of composites have been investigated. Results show it is a facile and cost-saving method to produce composites specifically in the application areas like automobile interior ornament and decoration materials, etc.     

Oil Red as a histochemical stain for natural fibers and plant cuticle

Properties of natural fibers are influenced by the nature of their surface. Oil Red was evaluated as a histochemical stain for the waxy components on the surface of cotton and flax fibers and of plant cuticles. A positive reaction for arachidyl stearate and differential staining of fibers after sequential extraction of fatty acids and alcohols indicated that Oil Red stained wax components in plant materials. For cotton (Gossypium hirsutum) fibers, Oil Red stained to a greater extent the regions closest to the seed coat, especially at points where fibers attached to the seed coat. Fiber regions at a distance from the seed coats stained irregularly, suggesting that the wax was unevenly distributed. Flax (Linum usitatissimum) bast fibers, in contrast, did not stain with Oil Red, but the protective stem cuticle was intensely stained. The positive histochemical reaction for cuticle identified non-fiber fragments in processed and cleaned flax fibers, thus providing a quick method to detect visually trash components in fiber and products. Likewise, bast fibers from kenaf (Hibiscus cannabinus) did not stain well with Oil Red, whereas the stem cuticle gave a positive reaction. The general usefulness of Oil Red as a histochemical stain for the plant cuticle was demonstrated in leaves and stems of mature corn (Zea mays) and fresh bermudagrass (Cynodon dactylon) leaves. Oil Red provides a quick, qualitative histochemical method to demonstrate the wax-containing cuticle in plants.     

Effect of reinforcement and chemical treatment of fiber on The Properties of jute-coir fiber reinforced hybrid polypropylene composites

Present research investigates the mechanical properties of jute-coir fiber reinforced hybrid polypropylene (PP) composite with fiber loading variation and observes the effect of chemical treatment of fiber on property enhancement of the composites. Composites were manufactured using hot press machine at four levels of fiber loading (5, 10, 15 and 20 wt%). Fiber ratio’s were varied (jute:coir=1:1, 3:1 and 1:3) for 20 % fiber loaded composites. Both jute and coir fiber was treated using 5 % and 10 % NaOH solutions. Composites were also prepared using treated fiber with jute-coir fiber ratio of 3:1. Tensile, flexural, impact and hardness tests and Fourier transform infrared spectroscopic analysis were conducted for characterization of the composites. Tensile test of composite showed a decreasing trend of tensile strength and increasing trend of the Young’s modulus with increase in fiber loading. During flexural, impact and hardness tests, the flexural strength, flexural modulus, impact strength and hardness values were found to be increased with increase in fiber loading. All these properties enhanced with the enhancement of jute content except impact strength. 5 % NaOH treatment provided an improving trend of properties whereas, 10 % NaOH treatment showed the reverse one. The FTIR analysis of the composites indicated decrease of hemicelluloses and lignin content with alkali treatment.     

Transport studies of peanut shell powder reinforced natural rubber composites in chlorinated solvents

Composites of Natural rubber (NR) Peanut shell powder (PSP) were prepared and their morphology, transport behavior at different temperatures in chlorinated solvent were studied. The PSP used in compounding the natural rubber was processed in two particle sizes. The effect of modification by alkali treatment of PSP on polymer properties was also investigated. The computed solvent properties were discussed in terms of PSP content, particle size, nature of solvent, and temperature. All the NR-PSP composites were found to decrease with the uptake of chlorinated solvents than NR, but the effect was more significant in the case of alkali treated PSP composites. Furthermore, the uptake of solvent decreased with increase in penetrant size; being the highest for dichloromethane, and the lowest for carbon tetrachloride. Activation energy was found to be maximum for highest in dichloromethane at the filler contents investigated. The thermodynamic parameters of the sorption process were also evaluated. The results showed that PSP filler acts as functional additives capable of manipulating and tailoring the transport of chlorinated solvents through elastomeric membranes even at concentrations as low as 10 parts per hundred (phr). The relationship between the transport behaviour and the morphology of the system was also examined.     

Mechanical and thermal degradation behavior of sisal fiber (SF) reinforced recycled polypropylene (RPP) composites

The present investigation focuses on the effect of fiber surface treatment on the mechanical, thermal and morphological properties of sisal fiber (SF) reinforced recycled polypropylene (RPP) composites. The surface of sisal fiber was modified using different chemicals such as silane, glycidyl methacrylate (GMA) and O-hydroxybenzene diazonium chloride (OBDC) to improve the compatibility between fiber surface and polymer matrix. The experimental results revealed an improvement in the tensile strength to 11 %, 20 % and 31.36 % and impact strength to 78.72 %, 77 % and 81 % for silane, GMA and OBDC treated sisal fiber reinforced recycled polypropylene (RPP/SF) composites respectively as compared to RPP. The thermo gravimetric analysis (TGA), Differential scanning calorimeter (DSC) and heat deflection temperature (HDT) results revealed improved thermal stability as compared with RPP. The morphological analysis through scanning electron micrograph (SEM) supports improves surface interaction between fiber surface and polymer matrix.     

Banana fiber-reinforced polypropylene composites: A study of the physico-mechanical properties

Banana fiber-reinforced polypropylene (PP) matrix composites were prepared by compression molding and their mechanical properties were evaluated. Banana fibers and matrices were irradiated with UV radiation at different intensities. Mechanical properties of irradiated banana fibers and matrices based composites were found to increase significantly compared to untreated counterparts. Optimized banana fibers were treated with 2-hydroxyethyl methacrylate (HEMA) solution and were cured in an oven at different temperatures for different curing times and then composites were fabricated. Monomer concentration, curing temperature and curing time were optimized with the extent of polymer loading and mechanical properties and showed better mechanical properties over untreated composites. Water uptake and simulating weathering test of the composites were also investigated.     

Structure and properties of methylcellulose microfiber reinforced wheat gluten based green composites

Environmentally friendly green composites were prepared by conventional blending wheat gluten (WG) as matrix, methylcellulose (MC) microfibers as filler and glycerol as plasticizer followed by compression molding of the mixture at 127 °C to crosslink the matrix. Morphology, dynamic mechanical analysis (DMA), tensile properties (Young’s modulus E, tensile strength σ_b and elongation at break ?_b), and moisture absorption (MA) and weight loss (WL) in water as well as thermogravimetric analysis (TGA) were evaluated in relation to MC content. It was found that addition of MC microfibers can significantly improve E and σ_b of the composite, which is accompanied by rises in glass transition temperatures of the WG matrix. Influences of MC content on the thermal decomposition and gluten solubility (GS) in water are also discussed.