Biocomposites reinforced with natural fibers: 2000–2010

Natural fiber reinforced composites is an emerging area in polymer science. These natural fibers are low cost fibers with low density and high specific properties. These are biodegradable and non-abrasive. The natural fiber composites offer specific properties comparable to those of conventional fiber composites. However, in development of these composites, the incompatibility of the fibers and poor resistance to moisture often reduce the potential of natural fibers and these draw backs become critical issue. This review presents the reported work on natural fiber reinforced composites with special reference to the type of fibers, matrix polymers, treatment of fibers and fiber-matrix interface. © 1999 John Wiley & Sons, Inc. Adv in Polymer Techn 18: 351–363, 1999

Natural fiber polymer composites: A review

Recently, there has been a rapid growth in research and innovation in the natural fibre composite (NFC) area. Interest is warranted due to the advantages of these materials compared to others, such as synthetic fibre composites, including low environmental impact and low cost and support their potential across a wide range of applications. Much effort has gone into increasing their mechanical performance to extend the capabilities and applications of this group of materials. This review aims to provide an overview of the factors that affect the mechanical performance of NFCs and details achievements made with them.

A review of recent developments in natural fibre composites and their mechanical performance

Natural fiber reinforced polymer composites (NFPCs) provide the customers with more alternatives in the material market due to their unique advantages. Poor fiber–matrix interfacial adhesion may, however, negatively affect the physical and mechanical properties of the resulting composites due to the surface incompatibility between hydrophilic natural fibers and non-polar polymers (thermoplastics and thermosets). A variety of silanes (mostly trialkoxysilanes) have been applied as coupling agents in the NFPCs to promote interfacial adhesion and improve the properties of composites. This paper reviews the recent progress in using silane coupling agents for NFPCs, summarizes the effective silane structures from the silane family, clarifies the interaction mechanisms between natural fibers and polymer matrices, and presents the effects of silane treatments on the mechanical and outdoor performance of the resulting composites.

Silane coupling agents used for natural fiber/polymer composites: A review

In the past decade, natural-fiber composites with thermoplastic and thermoset matrices have been embraced by European car manufacturers and suppliers for door panels, seat backs, headliners, package trays, dashboards, and interior parts. Natural fibers such as kenaf, hemp, flax, jute, and sisal offer such benefits as reductions in weight, cost, and CO2, less reliance on foreign oil sources, and recyclability. However, several major technical considerations must be addressed before the engineering, scientific, and commercial communities gain the confidence to enable wide-scale acceptance, particularly in exterior parts where a Class A surface finish is required. Challenges include the homogenization of the fiber's properties and a full understanding of the degree of polymerization and crystallization, adhesion between the fiber and matrix, moisture repellence, and flame-retardant properties, to name but a few.

Natural-fiber-reinforced polymer composites in automotive applications

The effect of several chemical treatments, viz. organotitanate, zirconate, silane, and N-substituted methacrylamide, on the properties of sisal fibers used as reinforcement in unsaturated polyester resin (∼50 vol%) was investigated. An improvement in the properties was observed when sisal fibers were modified with surface treatments. Under humid conditions, a decrease of 30 to 44% in tensile and 50 to 70% in flexural strength has been noted. The strength retention of surface-treated composites (except silane) is high compared with untreated composites. It is observed that N-substituted methacrylamide-treated sisal composites exhibited better properties under dry as well as wet conditions. Fractographic evidence such as fiber breakage/splitting and matrix adherence on the pulled-out fiber surface explains such behavior.

Influence of fiber surface treatment on the properties of sisal-polyester composites

The durability of jute fibre-reinforced phenolic composites

Mechanical behaviour of particulate hybrid composite laminates as potential building materials

Efficacy evaluation of various coupling-agent-treated sisal fibers was made by contact angle measurements and Fourier transform infrared spectroscopy. It was found that high contact angle and reduced hydroxyl groups on titanate-treated fibers favor its better hydrophobicity over the other treatments. The presence of adsorbed layer of coupling agent on the fiber surface was ascertained by appearance, shifting, and decreased intensity of absorption bands. The lowest polar component of surface-free energy for N-substituted methacrylamide-treated fiber indicates the formation of ordered layers of its organofunctionality at the surface. The reason for enhanced interaction between sisal fiber and N-substituted methacrylamide is suggested by the formation of hydrogen bond, besides extracting a surface-active proton from the fiber surface by alkoxy group to form a covalent bond. An optimum treating condition of fiber for effective adsorptive interaction has been reported. The deposition of compound in the form of an aggregate on the fiber surface was also observed under scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1847–1858, 1998

Studies on adsorptive interaction between natural fiber and coupling agents

Natural fibres (sisal) were treated with various coupling agents such as organosilane, zirconate, titanate and N-substituted methacrylamide. The nature of the adsorbed chemical species on the fibre surfaces was analysed by Fourier transform infrared microscopy (FT-IR). The presence of precipitated oligomers on the surface was confirmed by the appearance of hydrogen-bonded carbonyl group and unsaturation bands. The results showed an irregular physisorption/chemisorption of coupling agents, their penetration beyond the surface, and a decrease in the hydrophilicity of fibres. SEM and dynamic contact angle studies on the fibres supported these findings. FT-IR microscopy in its reflectance mode was more effective in ascertaining the chemical nature and structure of adsorbed layers onto sisal fibre surfaces compared with DRIFT and transmission spectroscopy. The difference in the properties of untreated and chemically treated fibres has also been verified in the polymer composites.



© 2000 Society of Chemical Industry

Anchal Verma

Papers

Influence of fiber surface treatment on the properties of sisal-polyester composites

The durability of jute fibre-reinforced phenolic composites

Mechanical behaviour of particulate hybrid composite laminates as potential building materials

Studies on adsorptive interaction between natural fiber and coupling agents

FT-IR microscopic studies on coupling agents: treated natural fibres