Biocomposites reinforced with natural fibers: 2000–2010

Studies on the use of natural fibers as replacement to man-made fiber in fiber-reinforced composites have increased and opened up further industrial possibilities. Natural fibers have the advantages of low density, low cost, and biodegradability. However, the main disadvantages of natural fibers in composites are the poor compatibility between fiber and matrix and the relative high moisture sorption. Therefore, chemical treatments are considered in modifying the fiber surface properties. In this paper, the different chemical modifications on natural fibers for use in natural fiber-reinforced composites are reviewed. Chemical treatments including alkali, silane, acetylation, benzoylation, acrylation, maleated coupling agents, isocyanates, permanganate and others are discussed. The chemical treatment of fiber aimed at improving the adhesion between the fiber surface and the polymer matrix may not only modify the fiber surface but also increase fiber strength. Water absorption of composites is reduced and their mechanical properties are improved.

Chemical Treatments of Natural Fiber for Use in Natural Fiber-Reinforced Composites: A Review

This paper provides a comprehensive overview on different surface treatments applied to natural fibres for advanced composites applications. In practice, the major drawbacks of using natural fibres are their high degree of moisture absorption and poor dimensional stability. The primary objective of surface treatments on natural fibres is to maximize the bonding strength so as the stress transferability in the composites. The overall mechanical properties of natural fibre reinforced polymer composites are highly dependent on the morphology, aspect ratio, hydrophilic tendency and dimensional stability of the fibres used. The effects of different chemical treatments on cellulosic fibres that are used as reinforcements for thermoset and thermoplastics are studied. The chemical sources for the treatments include alkali, silane, acetylation, benzoylation, acrylation and acrylonitrile grafting, maleated coupling agents, permanganate, peroxide, isocyanate, stearic acid, sodium chlorite, triazine, fatty acid derivate (oleoyl chloride) and fungal. The significance of chemically-treated natural fibres is seen through the improvement of mechanical strength and dimensional stability of resultant composites as compared with a pristine sample.

Chemical treatments on plant-based natural fibre reinforced polymer composites: An overview

Characterization and Properties of Natural Fiber Polymer Composites: A Comprehensive Review

This review article describes the recent developments of natural fiber reinforced polypropylene (PP) composites. Natural fibers are low-cost, recyclable, and eco-friendly materials. Due to eco-friendly and bio-degradability characteristics of these natural fibers, they are considered as strong candidates to replace the conventional glass and carbon fibers. The chemical, mechanical, and physical properties of natural fibers have distinct properties; depending upon the cellulosic content of the fibers which varies from fiber to fiber. The mechanical properties of composites are influenced mainly by the adhesion between matrix and fibers. Chemical and physical modification methods were incorporated to improve the fiber—matrix adhesion resulting in the enhancement of mechanical properties of the composites. The most important natural fibers are jute, flax, and coir and their novel processing technics to develop natural fiber reinforced composites are also described.

Recent Development in Natural Fiber Reinforced Polypropylene Composites

The thermal and crystallisation behaviour of sisal/PP composites was studied by thermogravimetry (TG), differential scanning calorimetry (DSC) and polarising optical microscopy. Chemical modifications were made to sisal fibre using a urethane derivative of polypropylene glycol (PPG/TDI), maleic anhydride modified polypropylene (MAPP), and KMnO4 in order to improve the interfacial adhesion between the fibre and matrix. The thermal properties of the blends were analysed by TG analysis. The effects of fibre content and chemical treatments on the thermal properties were evaluated. It was found that treated fibre composites show superior properties compared to the untreated system. DSC measurements exhibited an increase in the crystallisation temperature and crystallinity, upon the addition of fibres to the PP matrix. This is attributed to the nucleating effects of the fibre surfaces, resulting in the formation of transcrystalline regions. On increasing the fibre content, the melting peak of the PP component was shifted to higher temperatures suggesting a constrained melting. The thickness of the transcrystalline layer formed depends on crystallisation temperature and time. The transcrystalline growth rate was slow in the quiescent state. On the other hand, upon the application of stress, transcrystallinity developed quickly. In fact, the shear stress at the polymer/fibre interface initiated the nucleation. Fibre surface modification by PPG/TDI increases the nucleating ability of sisal fibre to a very small extent.

C.K.S. Pillai

Papers

The thermal and crystallisation studies of short sisal fibre reinforced polypropylene composites