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

Sisal fibre and its composites: a review of recent developments

Mechanical properties of sisal/oil palm hybrid fiber reinforced natural rubber composites

Summary: The use of lignocellulosic fibers, pineapple leaf fiber (PALF) and sisal as reinforcements in thermoplastic and thermosetting resins for developing low cost and lightweight composites is an emerging field of research in polymer science and technology. Although, these biofibers have several advantages, such as low densities, low cost, nonabrasive nature, high filling level possible, low energy consumption, high specific properties, biodegradability, etc., over synthetic fibers, the absorption of moisture by untreated biofibers, poor wettability, and insufficient adhesion between the polymer matrix and fiber deteriorate the mechanical properties of composites made up of these biofibers. Therefore, the modification of these fibers is a key area of research at present to obtain optimum fiber-matrix properties. This review article is concerned with the structure, composition and properties of PALF and sisal, the chemical modifications of these fibers and PALF/sisal-reinforced thermosets, thermoplastics, rubber, cement, hybrids and biocomposites.

Scanning electron micrograph of tensile fractured surface of alkali treated sisal fiber (magnification ×500).

A Review on Pineapple Leaf Fibers, Sisal Fibers and Their Biocomposites

Bamboo fibre filled natural rubber composites: the effects of filler loading and bonding agent

Styrene-butadiene rubber (SBR) composites were prepared by incorporating short sisal fibers of different lengths and concentrations into the SBR matrix in a mixing mill according to a base formulation. The curing characteristics of the mixes were studied and the samples were vulcanized at 150°C. The properties of the vulcanizates such as stress-strain behavior, tensile strength, modulus, shore-A hardness, and resilience were studied. Both the cured and uncured properties showed a remarkable anisotropy. It has been found that aspect ratio in the range of 20–60 is effective for sufficient reinforcement. The mechanical properties were found to increase along and across the grain direction with the addition of fibers. The effects of fiber length, orientation, loading, type of bonding agent, and fiber-matrix interaction on the properties of the composites were evaluated. The extent of fiber orientation was estimated from green strength measurements. The adhesion between the fiber and the rubber was enhanced by the addition of a dry bonding system consisting of resorcinol and hexamethylene tetramine. The bonding agent provided shorter curing time and enhanced mechanical properties. The tensile fracture surfaces of the samples have been examined by scanning electron microscopy (SEM) to analyze the fiber surface morphology, orientation, fiber pull-out, and fiber-matrix interfacial adhesion. Finally, anisotropic swelling studies were carried out to analyze the fiber-matrix interaction and fiber orientation. © 1995 John Wiley & Sons, Inc.

Short sisal fiber reinforced styrene-butadiene rubber composites

Morphology and melt rheological behaviour of short-sisal-fibre-reinforced SBR composites

The tear failure and processing characteristics of short sisal fibre reinforced styrene butadiene rubber (SBR) composites were investigated. Tear strength was examined with special reference to the effects of fibre length, fibre orientation, fibre concentration and bonding agent. It was observed that the tear strength depends on all the above factors. The tear failure mechanism was analysed from fractographs taken using a scanning electron microscope (SEM). During tear testing, the composites failed by a shearing process. Microscopic examination of cracks propagating in SBR composites revealed that the amorphous SBR matrix developed cracks, leaving ligaments of rubber attached to the broken fibres. The rubber particles were stretched as the crack opened and failure occurred at large critical extensions. It was observed that an increase in the concentration of fibres increased the tear strength in both longitudinal and transverse directions. The tear strength values were almost three to four times higher than those of the unfilled vulcanizates under similar conditions. In order to analyse the processing behaviour, the green strength, mill shrinkage and Mooney viscosity of the compounds were determined. Finally, the polymer-filler interaction was studied using the Lorenz-Park and Kraus equations.

Tear and processing behaviour of short sisal fibre reinforced styrene butadiene rubber composites

A series of short fibre reinforced styrene butadiene rubber (SBR) composites were prepared by incorporating sisal fibres of different lengths and different concentrations. The vulcanization behaviour and the properties of the vulcanizates were measured by the relevant ASTM procedures. The processing characteristics such as green strength and mill shrinkage were improved by the addition of fibres. The properties like tensile strength, tear strength, moduli at 10% and 20% elongations were found to be maximum for composites containing longitudinally oriented fibres of length 6 mm. Mixes containing 35 phr loading of fibres and bonding agent showed better mechanical performance than others. The failure behaviour of tensile and tear specimens have been analysed by scanning electron microscopy techniques.

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Short fibre elastomer composites: effect of fibre length, orientation, loading and bonding agent

Short sisal fiber-reinforced styrene butadiene rubber (SBR) composites were prepared and characterized by the restricted solvent swelling technique. The solvent swelling characteristics of SBR composites containing untreated and bonding agent-added mixes were investigated in a series of aromatic solvents, such as benzene, toluene, and xylene. The diffusion experiments were conducted by the sorption gravimetric method. The adhesion between the rubber and short sisal fibers was evaluated from the restricted equilibrium swelling measurements. The anisotropy of swelling of the composite was confirmed by this study. The effect of fiber orientation in controlling the anisotropy of restricted swelling was also demonstrated. As the fiber content increased, the solvent uptake decreased, due to the increased hindrance and good fiber-rubber interactions. Bonding agent-added mixes showed enhanced restriction to swelling, due to the strong interfacial adhesion. The bonding system containing hexa-resorcinol in the mix ...

R. Prasantha Kumar

Papers

Short sisal fiber reinforced styrene-butadiene rubber composites

Morphology and melt rheological behaviour of short-sisal-fibre-reinforced SBR composites

Tear and processing behaviour of short sisal fibre reinforced styrene butadiene rubber composites

Short fibre elastomer composites: effect of fibre length, orientation, loading and bonding agent

Interfacial adhesion in sisal fiber/SBR composites: an investigation by the restricted equilibrium swelling technique