Natural fiber reinforced polyester composites: A literature review

Abstract

Many composite products are made of thermosetting polymers reinforced with synthetic fibers. Despite the high mechanical properties associated with these fibers they are heavy and expensive compared with natural fibers. The use of natural plant fibres, combinations of natural and synthetic fibers, and wood furnish as reinforcement in polyester matrix for making low cost engineering materials has generated much interest recently. Natural fibers with good specific stiffness and strength, low density, low embodied energy, and good biodegradability have an advantage over synthetic fibers. Despite these benefits they have poor compatibility with the matrix due to their hydrophilic nature. This paper reviews the literature on the effects of chemical treatments on fiber-matrix interfacial adhesion and the wettability of natural fibers by polyester. The efficiency of incorporating glass fiber into the natural fiber for the purpose of reducing water uptake and increasing the stiffness of composite is also discussed. Plant fiber/polyester composites Hemp fiberHemp fiber is the most common natural fiber for reinforcing polyester composites. The composites can be manufactured using hand lay-up, compression molding, or resin transfer molding (RTM) methods. The drawback of using plant fibers as reinforcement is their susceptibility to water adsorption due to their hydrophilic nature. Surface modification of fiber, however, can limit their water uptake. The effects of hemp fiber loading, content, and chemical treatments on energy absorbing ability, and on tensile, flexural, and water absorption properties of polyester composites are discussed in this section.Fiber loading and fiber length effects. The energy absorbing mechanisms of hemp fiber/polyester composites associated with the impact fracture have been investigated in detail by Sanadi et al. 1 Composites were made using hand lay-up method and their Izod impact toughness were measured. Results of this study showed the toughness of composites at volume fraction of 24% to be 15 times higher than the pure polyester resin. Scanning electron microscope (SEM) micrographs of fracture surface indicated that various fracture mechanisms including fiber pull-out, plastic flow of the lignin-hemicellulose matrix, hemp fiber splitting, and crack extension at fibril-fibril interface contributed to energy absorption. In a similar study by Dhakal et al. 2 different hemp fiber volume fractions, up to 26%, were used to make nonwoven hemp fiber/polyester composites. A combination of hand lay-up and compression molding methods was used to manufacture these composites. Results indicated the percentage of moisture uptake increased with fiber volume fraction. The increase was attributed to the additive amount of cellulose content at higher

Jute: A Potential Candidate for Phytoremediation of Metals—A Review

“…Other major jute-and kenaf-growing countries are China, Thailand, Myanmar, Indonesia, Brazil, and Nepal. Africa and the Indo-Myanmar region are the primary and secondary centers of origin, respectively, for jute, while the Indo-Myanmar region including South China is considered the center of origin of jute [68][69][70]. Some major exporters of jute fibres along their annual yields per tons are presented in Figure 1.…”

Flax (Linum usitatissimum L.): A Potential Candidate for Phytoremediation? Biological and Economical Points of View

“…All these characteristics of flax make it a potential candidate to grow in metal contaminated soils and it can accumulate metal in the order of root > leaves stem > seed > fiber. Thus, flax can be used for phytoremediation and can provide 100% utilizable raw material which have no harmful residue as well as fully biodegradable waste [64,70,71].…”

“…They proved that flax could tolerate up to 400 mg kg −1 Cu while further increments of metal caused a significant reduction in plant growth and biomass. They also determined Cu used the digestion method at different stages of the plant growth, i.e., 35,70,105, and 140 days after sowing (DAS). Their results also suggested that in the early stage of the life cycle of the plant, Cu tended to accumulate in the roots and was transported to the shoots at the last stage of the plant life cycle.…”

Manufacturing and characterization of hemp‐reinforced epoxy composites

“…Several natural reinforcements can be found in literature, including flax, hemp, jute, sisal, cotton, silk, and others . Among these classes of materials, hemp‐reinforced polymeric composites are especially suitable to be applied in industrial design because of their unique mechanical and physical properties …”