Biocomposites reinforced with natural fibers: 2000–2010

A critical review of the literature on the various aspects of natural fibers and biocomposites with a particular reference to chemical modifications is presented in this paper. A notable disadvantage of natural fibers is their polarity which makes it incompatible with hydrophobic matrix. This incompatibility results in poor interfacial bonding between the fibers and the matrix. This in turn leads to impaired mechanical properties of the composites. This defect can be remedied by chemical modification of fibers so as to make it less hydrophilic. This paper reviews the latest trends in chemical modifications and characterizations of natural fibers. The structure and properties of natural fibers have been discussed. Common chemical modifications and their mechanisms have also been elaborated. The importance of chemical modifications and the resultant enhancement in the properties of the composites have also been reviewed. Recent investigations dealing with chemical modifications of natural fiber-reinforced composites have also been cited. POLYM. COMPOS., 29:187‐

Recent Developments in Chemical Modification and Characterization of Natural Fiber-Reinforced Composites

In recent years, the use of flax fibres as reinforcement in composites has gained popularity due to an increasing requirement for developing sustainable materials. Flax fibres are cost-effective and offer specific mechanical properties comparable to those of glass fibres. Composites made of flax fibres with thermoplastic, thermoset, and biodegradable matrices have exhibited good mechanical properties. This review presents a summary of recent developments of flax fibre and its composites. Firstly, the fibre structure, mechanical properties, cost, the effect of various parameters (i.e. relative humidity, various physical/chemical treatments, gauge length, fibre diameter, fibre location in a stem, oleaginous, mechanical defects such as kink bands) on tensile properties of flax fibre have been reviewed. Secondly, the effect of fibre configuration (i.e. in forms of fabric, mat, yarn, roving and monofilament), manufacturing processes, fibre volume, and fibre/matrix interface parameters on the mechanical properties of flax fibre reinforced composites have been reviewed. Next, the studies of life cycle assessment and durability investigation of flax fibre reinforced composites have been reviewed.

Flax fibre and its composites – A review

Natural fibers today are a popular choice for applications in composite manufacturing. Based on the sustainability benefits, biofibers such as plant fibers are replacing synthetic fibers in composites. These fibers are used to manufacture several biocomposites. The chemical composition and properties of each of the fibers changes, which demands the detailed comparison of these fibers. The reinforcement potential of natural fibers and their properties have been described in numerous papers. Today, high performance biocomposites are produced from several years of research. Plant fibers, particularly bast and leaf, find applications in automotive industries. While most of the other fibers are explored in lab scales they have not yet found large-scale commercial applications. It is necessary to also consider other fibers such as ones made from seed (coir) and animals (chicken feather) as they are secondary or made from waste products. Few plant fibers such as bast fibers are often reviewed briefly but other p...

A Review of Natural Fibers Used in Biocomposites: Plant, Animal and Regenerated Cellulose Fibers

Environmentally-friendly monofilament cellulosic fibres have been widely used as alternatives for conventional steel reinforcement within concrete. Recently, the use of cellulosic fibre fabrics and their fabric reinforced polymer composites as reinforcement materials within and/or outside of construction materials (e.g. concrete) has gained popularity due to their inexpensive cost and favourable specific mechanical properties compared with synthetic fibre fabrics (e.g. E-glass). This review presents a summary of recent development on cellulosic fibre Fabric Reinforced Cementitious (FRC) and Fabric Reinforced Geopolymer (FRG) composites, as well as their cellulosic Fabric Reinforced Polymer (FRP) composites as reinforcements of concrete, masonry and timber structures for civil engineering applications. This review covers: (1) properties (i.e. chemical composition, microstructure, mechanical properties and cost) of monofilament cellulosic fibres and their comparison with synthetic fibres, the relationship between fibre chemical composition and fibre mechanical properties, parameters affect fibre properties; (2) properties (e.g. fabrication of monofilament fibres to fabrics and structures) of cellulosic fibre fabrics, properties of polymer matrices, and properties (i.e. flexural, tensile, impact, insulation and fire properties) of cellulosic fabric FRP composites; and (3) properties (compressive, flexural and tensile and impact properties) of cellulosic FRC and FRG composites, and the properties of cellulosic FRP composites reinforced concrete, masonry and timber structures. In addition, the degradation mechanisms of cellulosic FRC and FRP are discussed. Furthermore, the durability of FRC, FRG and FRP composites are reviewed and the methods to improve the durability of FRC, FRG and FRP composites from the aspects of fibre modification and matrix modification are reviewed and summarized.

A review of recent research on the use of cellulosic fibres, their fibre fabric reinforced cementitious, geo-polymer and polymer composites in civil engineering

Effect of chemical treatments on water sorption and mechanical properties of flax fibres

Because of their good mechanical properties and low density, natural fibres are more and more considered as reinforcement in composite materials. In this work, to improve the adhesion between a polyester matrix (unsaturated polyester resin) and Agave (Agave Americana L .) fibres and to increase their moisture resistance, chemical surface treatments have been performed on the fibres. These different treatments were performed with acetic anhydride (Ac), styrene (S), acrylic acid (AA) and maleic anhydride (MA). The modified Agave fibres were characterized by means of infrared spectroscopy, surface energy, and microscopic analysis. The effect of these treatments on water sorption was investigated by using a gravimetric static equilibrium method. Water sorption isotherms have been deduced from kinetic data. The Park model based on the three sorption modes: Langmuir, Henry’s law, and clustering, was successfully used to simulate the experimental sorption data. It was found that the chemical treatments used reduced the overall water uptake of the Agave fibres. In particular, the acetylation treatment allows to significantly increase the moisture resistance of these fibres. The mechanical properties of the treated fibres were analyzed from tensile tests. The tensile modulus, the breaking strength and the breaking strain depend on the chemical treatment used.

Influence of chemical modifications on water-sorption and mechanical properties of Agave fibres

In this study, composite materials were prepared using unsaturated polyester resins reinforced by Alfa fibres. The fibres were previously modified by chemical treatments, maleic anhydride (MA), styrene (S), acrylic acid (AA) and acetic anhydride (Ac). The Ac and the S treatments allowed an increase in the moisture resistance and the mechanical properties of the fibres. The preliminary S or MA treatment of the fibres allowed a decrease of the water permeability of the composite. A slight increase of the stiffness of the composite was observed due to the presence of the fibres (treated or not), whereas the resistance (breaking strength and strain) was not improved. The mechanical behaviour of the composites appeared similar whatever the treatment of the fibres except with S treatment which seemed to improve the breaking strength.

Alfa fibres for unsaturated polyester composites reinforcement: Effects of chemical treatments on mechanical and permeation properties

The plastic materials used for packaging are increasing leading to a considerable amount of undegradable solid wastes. This work deals with the reduction of conventional plastics waste and the natural resources preservation by using cellulosic polymers from renewable resources (alfa and luffa). Plasticized starch films syntheses were achieved at a laboratory scale. These natural films showed some very attractive mechanical properties at relatively low plasticizers levels (12 to 17 % by weight). Furthermore, mixtures including polylactic acid polymer (PLA) and cellulose fibers extracted from alfa and luffa were investigated by melt extrusion technique. When used at a rate of 10 %, these fibers improved the mixture mechanical properties. Both developed materials were biodegradable, but the plasticized starch exhibited a faster biodegradation kinetic compared to the PLA/cellulose fibers. These new materials would contribute to a sustainable development and a waste reduction.

Biodegradable packaging materials conception based on starch and polylactic acid (PLA) reinforced with cellulose.

Because of their good mechanical properties and low density, natural fibers are more and more considered as reinforcement in composite materials. To improve the adhesion between the polymer matrix and natural fibers and to reduce the water sorption, helium cold plasma and autoclave treatments have been performed on flax fibers. The effect of these treatments on water sorption has been investigated by means of a gravimetric static equilibrium method (IGA). Water sorption isotherms have been deduced from kinetic data. Specific mathematical models have been tested to predict the water sorption isotherms of the treated flax fibers. The Park model based on the three sorption modes: Langmuir, Henry's law, and clustering, was successfully used to simulate the experimental sorption data. The results show no significant effect after plasma treatment while an increase of moisture resistance has been observed after autoclave treatment. This effect of autoclave treatment is interpreted in terms of modifications of cell-wall structure. In a kinetic point of view, for the untreated and treated flax fibers, the variation of the diffusion coefficient with water concentration is in agreement with the three sorption modes of the Park model. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4281–4289, 2006

A. Bessadok

Papers

Effect of chemical treatments on water sorption and mechanical properties of flax fibres

Influence of chemical modifications on water-sorption and mechanical properties of Agave fibres

Alfa fibres for unsaturated polyester composites reinforcement: Effects of chemical treatments on mechanical and permeation properties

Biodegradable packaging materials conception based on starch and polylactic acid (PLA) reinforced with cellulose.

Study of water sorption in modified flax fibers