Wood Fibre Reinforced Polypropylene Composites Research Articles

Tensile and impact properties of pulverized oil palm fiber reinforced polypropylene composites : A comparison study with wood fiber reinforced polypropylene composites

In this study, the Malaysian oil palm fiber (OPF) was extracted from empty fruit bunch (EFB) and used as a reinforcement of polymer composite materials. 10 wt.% and 25 wt.% of OPF were incorporated with polypropylene (PP) and maleated polypropylene (MAPP) to produce injection-molded composite material. For comparison purpose, virgin PP and polymer composites reinforced with wood fiber (WPC) were also fabricated as benchmark samples. From the tensile test result of 25 wt.% of fiber loading, it produced higher tensile properties of the composites. Moreover, the obtained OPF/PP composites showed comparable properties with the WPC material. The second objective of this study is to investigate the effect of fiber sizes on tensile and impact properties of both WPC and OPF/PP composite. The wood fiber and OPF were mechanically classified into several size ranges by using different mesh sieves and proceeded with the kneading and injection molding. The tensile and impact tests were carried out for each type of sample in order to verify the influence of fiber size on the tensile and impact resistance behavior of the WPC and OPF/PP composites.

Impact Resistance Bio Compound

Modified wood fibre reinforced polypropylene composites at a wood fibre content of 50 wt. % are prepared using different types of wood fibres (beech wood refiner fibre, mercerised beech wood refiner fibre, mercerised and bleached beech wood refiner fibre as well as beech wood chips, mercerised beech wood chips, mercerised and bleached beech wood chips) to improve the impact resistance of the final composite. Additionally a beech wood refiner fibre-PP composite as well as a beech wood chip-PP composite are mixed with regenerated cellulosic fibres (5 wt. % and 10 wt. %) to further enhance the impact resistance. To increase the interfacial adhesion with the matrix and to improve the dispersion of particles two different coupling agents with contents from 2 wt. % to 8 wt. % are tested with two wood plastic composites (WPC). One is made of beech wood refiner fibres and the other one is produced from beech wood chips.The present study investigated Charpy impact property of wood fibres reinforced polypropylene as a function of fibre modification, content of regenerated cellulosic fibres and coupling agent.From the results it is observed that beech wood refiner fibre-PP composites show better Charpy impact properties than beech wood chips-PP composites. Charpy impact resistance is improved by mixing regenerated cellulose fibres (RCF) and RCF-PP-granule with beech wood refiner fibres and chips. The maximum increase in impact resistance is two times for refiner fibres and 10 % RCF-PP-granule respectively three and a half times for chips and 10 % RCF-PP-granule. By adding coupling agent Charpy impact resistance is nearly doubled for all wood fibre-PP composites.

Accelerated weathering of unbleached and bleached Kraft wood fibre reinforced polypropylene composites

In this paper, combined moisture/ultraviolet (UV) weathering performance of unbleached and bleached Kraft wood fibre reinforced polypropylene (PP) composites was studied. Composites containing 40 wt% fibre with 3 wt% of a maleated polypropylene (MAPP) coupling agent were fabricated using extrusion followed by injection moulding. Composite mechanical properties were evaluated, before and after accelerated weathering for 1000 h, by tensile and impact testing. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were also carried out to assess the changes occurring during accelerated weathering. Bleached fibre composites initially showed higher tensile and impact strengths, as well as higher thermal stability and greater crystallinity. During accelerated weathering, both unbleached and bleached fibre composites reduced tensile strength (TS) and Young's modulus (YM), with the extent of the reduction found to be similar for both unbleached and bleached fibre composites. Evidence supported that the reduction of TS and YM was due to PP chain scission, degradation of lignin and reduced fibre–matrix interfacial bonding.

Reprocessing of wood fibre reinforced polypropylene composites. Part II: Hygrothermal ageing and its effects

In this paper, hygrothermal ageing behaviour of virgin and reprocessed composites based on radiata pine (Pinus Radiata) wood fibre with a polypropylene (PP) matrix were investigated. Composites were produced with 40 wt% fibre and 4 wt% maleated polypropylene (MAPP) coupling agent using extrusion followed by injection moulding. Composites reprocessing was carried out using repeated pelletising and injection moulding for up to eight times. Hygrothermal ageing was carried out by immersing specimens in distilled water at 50 °C over a 9 month period. The diffusion coefficient of moisture absorption was obtained for composites by measuring water uptake of specimens at regular time intervals. It was found that the diffusion coefficient and the equilibrium moisture contents of composites decreased with increased number of times the materials were reprocessed. After hygrothermal ageing, tensile strength (TS), Young’s modulus (YM) and hardness of both virgin and reprocessed composites were found to decrease, but impact strength (IS) and failure strain (FS) increased. The thermal stability of both virgin and reprocessed composites was found to decrease after hygrothermal ageing.

Reprocessing of wood fibre reinforced polypropylene composites. Part I: Effects on physical and mechanical properties

This paper describes the effects of reprocessing on the physical and mechanical properties of composites based on radiata pine ( Pinus radiata ) fibre in a polypropylene (PP) matrix. Composites, containing either 40 wt% or 50 wt% fibre with 4 wt% maleated polypropylene (MAPP) as a coupling agent, were reprocessed up to eight times. For composites with 40 wt% fibre, tensile strength (TS) and Young’s modulus (YM) were found to decrease with increased reprocessing by up to 25% for TS and 17% for YM (after reprocessed eight times). Flexural tests were also carried out for 40 wt% fibre composites and flexural strength and modulus were found to decrease with increased reprocessing. Although, TS was lower for virgin composites with 50 wt% fibre than for those with 40 wt% fibre, this initially increased with reprocessing by up to 14% (after reprocessed two times), but then decreased with further reprocessing, and an overall 11% reduction of TS was found after reprocessing eight times compared to the virgin composites. YM was higher for virgin composites with 50 wt% than those with for 40 wt% fibre and also initially increased with reprocessing but decreased upon further reprocessing. Reprocessing was found to increase thermal stability. The TS of composites made by combining reprocessed with virgin materials was also assessed.

Influence of Separation and Processing Systems on Morphology and Mechanical Properties of Hemp and Wood Fibre Reinforced Polypropylene Composites

ABSTRACT The separation processes of natural fibres and the technique of composite processing influence the fibre degradation, length and herewith the composites properties in a wide range. Different separation processes (mechanical, refiner and enzymatic separation) were investigated with hemp and partially with flax and wheat straw. Selected fibres were mixed with PP in a cascade mixer (heat-cooling mixer system) or compounded in a twin screw extruder and formed into test specimens by injection moulding with 40 wt.% fibre content. Thermomechanical processed hemp fibre-PP composites showed higher mechanical properties in cascade mixer process compared to twin-screw extruder or agglomerated process. Wood fibre reinforced polypropylene composites containing hard wood fibre were prepared by extrusion-injection moulding, mixer-injection moulding, compression moulding and direct extrusion (profile) process with 30 wt.% and 50 wt.% fibre contents. It is seen that extrusion-injection moulding process showed best properties compared to other processes in maximum cases.

Recycling and Its Effects on the Physical and Mechanical Properties of Wood Fibre Reinforced Polypropylene Composites

This study investigates the effect of recycling/reprocessing on the physical and mechanical properties of composites based on radiata pine (Pinus Radiata) fibre and polypropylene (PP) with a maleated polypropylene (MAPP) coupling agent, produced using a twin-screw extruder, followed by injection moulding. Composites containing 40wt% fibre and 4wt% MAPP were assessed mechanically and thermally, as well as for moisture absorption after being recycled up to eight times. Both the tensile strength (TS) and Young’s modulus (YM) of composites were found to decrease linearly from 41 MPa and 4556 MPa respectively to 31 MPa and 3800 MPa for composites recycled eight times. However, the elongation at break was found to increase with increased recycling due to fibre damage that occurred during reprocessing and the associated reduction of average fibre length, found to decrease from 2.36mm to 0.37mm after recycling eight times. Thermal stability and moisture resistance of composites improved with recycling due to the improvement of interfacial bonding between fibre and matrix.

Investigation of the Debonding Process in Wood Fiber Reinforced Polymer Composites by Acoustic Emission

Wood fiber reinforced polypropylene composites of different fiber contents without any treatment were prepared, and tensile tests were carried out on injection molded specimens. With increasing fiber content a decrease of the tensile strength was experienced. The weak adhesion at the fiber-matrix interface and the typical composite failures can be seen on SEM pictures. During the tests acoustic emission was monitored to get more information about the damage mechanism. From the AE counts distribution it can be concluded that the maximum number of AE counts decreases simultaneously with the tensile strength in case of the different composites.

Mechanical properties of wood–fiber reinforced polypropylene composites: Effect of a novel compatibilizer with isocyanate functional group

Natural fibers are increasingly being used as reinforcement in commercial thermoplastics due to their low cost, high specific properties and renewable nature. While the maleic anhydride modified polypropylene (MAPP) is most commonly used as compatibilizer to improve interfacial adhesion between hydrophilic wood–fibers and hydrophobic polypropylene, in this study, a novel compatibilizer (m-TMI-g- PP) with isocyanate functional group was synthesized by grafting m-isopropenyl-\alpha,\alpha-dimethylbenzyl-isocyanate (m-TMI) onto isotactic polypropylene (PP) in a twin screw extruder. The effect of filler concentration on the mechanical properties of wood–fiber filled composites, prepared by using m-TMI-g-PP as the compatibilizer, was investigated. The addition of the compatibilizer resulted in greater reinforcement of composites, as indicated by the improvement in mechanical properties. Tensile strength of composites so prepared increased by almost 45%, whereas 85% increase in flexural properties was observed. However the addition of wood–fibers resulted in a decrease in elongation at break and impact strength of the composites.

Microcellular Wood Fibre Reinforced PP Composites

Abstract Microcellular wood fibre reinforced polymers have practical significance given the possibility of reducing the density of automotive components due to their microcellular structure, as well as processing and performance advantages. A microcellular foaming process with a chemical foaming agent was applied at an experimental stage to injection moulding, extrusion and compression moulding of wood fibre reinforced polypropylene composites. The focus of the research was to investigate these processes using a chemical foaming agent and to perform comparative studies of the physico-mechanical properties of microcellular materials. The effects of the presence of the chemical foaming agent (exothermic) and variation of its content on density, microvoid content, mechanical properties (tensile and flexural), odour concentration and cell morphology of microcellular polypropylene-wood fibre composites were studied. The morphology, cell size, shape and distribution of the microcells were investigated using scanning electron micrographs. Injection moulding process produced finer microcellular structures in comparison with the other processes. As compared to the non foamed composites, the density reduced maximum 30% (0.741 g/cm3), 20% (0.837 g/cm3) and 22% (0.830 g/cm3) for the injection moulding, extrusion and compression moulding process respectively. The chemical foaming agent reduced the odour concentration in relation to the same non foamed composites. Injection moulding showed better performance in comparison with extrusion and compression moulding in terms of cell morphology, density reduction, odour concentration and mechanical properties.

Fiber Pretreatment and Its Effects on Wood Fiber Reinforced Polypropylene Composites

ABSTRACT This study investigates the effect of pretreatment of fiber with NaOH and coupling with maleated polypropylene (MAPP) on the physical and mechanical properties of composites, based on radiata pine (Pinus Radiata) fiber, produced with a polypropylene matrix, using a twin-screw extruder followed by injection molding. Prior to reinforcement, the fiber was treated with NaOH. The effect of treatment was assessed using zeta potential, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Tensile testing, SEM, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) were carried out to assess the effect of modification on composite properties. An increase of 106% for strength and 302% for Young's modulus were obtained by using 60 wt% fiber and 2 wt% MAPP, compared to the unreinforced matrix. Fiber pretreatment with NaOH reduced strength but improved Young's modulus (370% compared to unreinforced matrix) of resulted composite.

Influence of Different Endothermic Foaming Agents on Microcellular Injection Moulded Wood Fibre Reinforced PP Composites

Microcellular wood fibre reinforced polypropylene composites, a new development using bio-fibre strengthened plastic, were prepared in an injection moulding process. The influence of three different endothermic chemical foaming agents was examined. The effects of various concentrations (1 to 4 wt.% of the composites) of the chemical foaming agent on the properties of the composites was studied with a view to establishing the concentration-structure-property relationships for these materials. The influence of wood fibre type (hard wood and soft wood) on the microcellular structure and physico-mechanical properties of the composites was also investigated. Microcell morphology (cell size, shape and distribution) was observed using scanning electron microscope. The chemical substance of different endothermic foaming agent affected the microcellular structure of hard and soft wood fibre-PP composites. Endothermic foaming agent with chemical substance polymeric microsphere (ESC 5313) showed finer microcellular structures compared to other foaming agents and 4 wt.% content of chemical foaming agent exhibits finer microcellular structures than the other contents. The reinforcing of soft wood fibre showed significantly finer microcellular structures than the hard wood fibre reinforcements. Density reduced maximum 30% and decreased up to 0.721 g/cm3 at soft wood fibre 30 wt.% content with coupling agent maleic anhydride grafted polypropylene (MAH-PP). With the addition of MAH-PP, specific tensile strength and specific flexural strength increased maximum 60% and 55% respectively with foaming agent ESC 5313 at soft wood fibre 30 wt.% content.

Microfoaming of flax and wood fibre reinforced polypropylene composites

Natural and wood fibre reinforced plastics as a relatively new group of environmental friendly materials have been extensively applied in interior, building applications and in the automobile industry. Among others, natural and wood fibre reinforced foamed polymer materials are of high significance because of the possibility of their reducing the density of automotive components which have a cellular structure. However, the properties of these materials have not been fully investigated and described. Microcellular composites of polypropylene containing natural and wood fibre was prepared using an injection moulding process. In the present work, the manufacturing technology of natural and wood fibre reinforced polymer microfoams was developed and the influence of fibre and microvoid content on its property spectrum was systematically investigated. The forming of microvoids and the degree of foaming related to the variation of the processing parameters in connection with manufacture technology was characterised. Measurement of density, cell size, tensile and flexural properties of the prepared composites was carried out. The cell structure is dependent on flow direction of foaming. The density of microfoamed wood fibre-PP composites was reduced by about 24% and decreased by as much as 0.77 g/cm3.Light microscopy showed that the cells are circular and it was also observed that the maximum cell sizes are between 10–50 μm. Water absorption and scanning electron microscopy of the composites were also investigated. Considering the experimental results, it can be deduced that the microcellular composites exhibit a possible combination of relatively good engineering properties and lower density for different technical applications.

Wood Fiber Reinforced Polypropylene Composites: Compression and Injection Molding Process

Wood fiber reinforced polypropylene composites containing different types of wood fiber (hard and softwood fiber) were prepared by an injection molding and a compression molding process. Influence of different processing systems and compatibilizer on the composite mechanical properties was investigated. The present study investigated the tensile, flexural, charpy impact, and impact properties of wood-fiber reinforced polypropylene composites as a function of processing system and compatibilizer. From the results, it is observed that injection molding process showed better tensile and flexural properties comparative with compression molding process, which is about 155% and 60% for tensile strength, and flexural strength, respectively. Charpy impact strength increased the maximum in compression molding for hard-wood fiber-PP (PP) composites, and it is about 70% at the wood-fiber content of 30%. Impact resistance in injection molding process shows better performance comparison to compression molding process and damping index decreased the most at about 60% in injection molding process for hard-wood fiber-PP composites at the wood-fiber content of 50%. Scanning electron microscopy of the composites also is investigated to better understand the interaction between wood fiber and polypropylene in both processing systems.

Creep and impact properties of wood fibre–polypropylene composites: influence of temperature and moisture content

Wood fibre reinforced polypropylene composites of different fibre content (40, 50 and 60% by weight) have been prepared and wood fibres (hard and long fibre) were treated with compatibiliser (MAH-PP) to increase the interfacial adhesion with the matrix to improve the dispersion of the particles and to decrease the water sorption properties of the final composite. Results indicated that impact properties were affected by moisture content. The Charpy impact strength decreased and maximum force was increased with increasing of moisture content. With the addition of MAH-PP (5% relative to the wood fibre content), damping index decreased around 145% for hard wood fibre–PP composites at 60 wt.% wood fibre content. Long wood fibre–PP composites showed more impact resistance than hard wood fibre–PP composites. Short term flexural creep tests were conducted to investigate the creep behaviour of wood fibre–PP composites. Three experimental parameters were selected: the addition of compatibiliser, temperature and wood fibre content. The addition of MAH-PP, increased creep modulus that means reduced the creep. The extent of creep resistance (creep modulus and creep strength) decreased with increasing temperature. It was also found that wood fibre content has a great effect on creep resistance which is increased with increasing wood fibre content.

Wood Fibre Reinforced Polypropylene Composites: Effect of Fibre Geometry and Coupling Agent on Physico-Mechanical Properties

Wood fibre reinforced polypropylene composites at fibre content 50% by weight have been prepared and different types of wood fibres (hard wood fibre, soft wood fibre, long wood fibre and wood chips) were treated with coupling agent (MAH-PP) to increase the interfacial adhesion with the matrix to improve the dispersion of the particles and to decrease the water sorption properties of the final composite. The present study investigated the tensile, flexural, charpy impact and impact properties of wood fibre reinforced polypropylene composites as a function of coupling agent and fibre length and structure. From the results it is observed that wood chips-PP composites showed better tensile and flexural properties comparative with the other wood fibre-PP composites with the addition of 5%MAH-PP, which is around 65% and 50% for tensile strength and flexural strength respectively. Hard wood fibre-PP composites showed better impact characteristic values comparative to other wood fibre-PP composites with the addition of 5%MAH-PP and damping index decreased about to 60%. Charpy impact strength also increased up to 60% with the addition of 5%MAH-PP for long wood fibre-PP composites. Water absorption and scanning electron microscopy of the composites are also investigated.