Hemp Fiber-Reinforced Thermoplastics

Girones et al. (2012) studied the mechanical properties of sisal and hemp fiber-reinforced thermoplastic cornstarch. The fiber increased the stiffness of the material. Results obtained in the tensile test displayed a continuous increase in both tensile modulus and ultimate strength that was proportional to the amount of reinforcement. Thus, Young s modulus for composites reinforced with a 20 % w/w of hemp... 

Several research studies have shown the effectiveness of hemp fiber-reinforced thermoplastic matrices [160-162]. Among the thermoplastic matrices, PP is one of the commodity thermoplastics with better properties such as low density, high Vicat softening point, good surface hardness, good flex hfe, scratch resistance, abrasion resistance, and very good electrical properties [163]. 

The lignocellulosic materials mostly used as fillers in thermoplastic composites include wood flour, starch, rice husk and a wide variety of vegetable fibers available such as jute, sisal, flax, hemp, coir, banana, pineapple, among others. And whenever vegetable fiber reinforced thermoplastic composites with higher properties are needed, possible solutions include improved adhesion, better fiber orientation, and filler hybridization with synthetic fibers or mineral fillers. The latter solution is an intermediate alternative regarding environmental friendliness, cost, weight and performance compared to an all synthetic composite [12,26]. 

Reinforcement of thermoplastic and thermosetting composites with cellulose fibers is increasingly regarded as an alternative to glass fiber reinforcement. The enviromnental issues in combination with their low cost have recently generated considerable interest in cellulose fibers such as isora, jute, flax, hemp, kenaf, pineapple leaf, and man-made cellulose fibers as fillers for polymer matrices-based composites. 

Cellulose is the most abundant polysaccharide in nature with approximately 180 billion tons produced and broken down every year (Engelhard 1995). Cellulose, which occurs as microfibrils, is the component responsible for the excellent load bearing properties of plant cell walls (for a summary for the cellulose content of the different cell wall layers, see Table 6-1). The cellulose microfibrils in wood fibers are important raw material for the pulp and paper industries, and those in cotton and hemp for the textile industries. Moreover, the renewable plant fibers have substantial potential to replace man-made fibers in fiber-reinforced thermosets and thermoplastics to produce environmentally friendly materials (Mohanty et al. 

Girones et al. (2012) studied the effect of incorporation of sisal or hemp strands in Thermoplastic starch (TPS) from cornstarch. Figure 6 shows the DMTA analysis of thermoplastic cornstarch reinforced with various hemp liber amounts. The addition of fibers caused an increase in the glass transition temperature (Tg) of the TPS as determined by DMTA. 

A number of reviews have been studied on the potential of natural fibers such as sisal, kenaf, hemp, flax, bamboo, and jute for the preparation of thermoplastic composites. In this work, however sisal fiber (SF) has been used as reinforcement due to easily availability and comparatively low cost. The xmtreated and treated SF-reinforced RPP composites have been prepared and investigated their thermal, mechanical, morphological, weathering and impact properties. An improved mechanical, thermal, and morphological property has been observed for chemical treated SF as well as clay loaded RPP. The analysis revealed that SF-reinforced RPP composites with enhanced properties can be successfully achieved which warrants to replace the synthetic fillers-based conventional thermoplastic composites. These SF-based RPP composites can be the material of choice in the field of aeronautic, automobiles, civil engineering, etc., due to its low cost, low density, non-toxicity, recyclability, acceptable strength, high specific properties, and minimum waste disposal problems. 

As such wood flour, used as a filler in thermoplastic composites, offers only modest, if any, reinforcement, but wood fibers can lead to superior composite properties and act more as reinforcing filler. Commercial wood flour is a by-product of the wood industry, often mechanically processed from waste materials such as planer shavings, chips, and sawdust, which are reduced to fine powders, with various grades available depending upon the particle size and the wood species. Wood (cellulose) fibers are produced through more or less complex defibrillation techniques, using raw materials from both virgin and recycled resources, and are different from natural fibers, such as jute, hemp, or sisal. 

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