Natural fiber composites moisture content

As the performance of the composite is profoxmdly dominated by the micromechanical deformation process, its knowledge and control are critical for the improvement of composite properties. The effect of particle characteristics and interfacial adhesion on the micromechanical deformation processes in PP-wood composites was investigated by Renner et al. [7]. They proposed a failure map as well as the practical results and considered the influence of matrix characteristics on deformation and failure in PP-natural fiber composites in other research [24]. Hietala et al. [78] studied the effect of chemical pre-treatment and moisture content of wood chips on the wood particle aspect ratio during the processing and mechanical properties of WPCs. The use of pretreated wood chips enhanced the flexural properties of the wood chip-PP composites. Moreover, the use of undried wood chips compared to dried one can improve and reduce the flexural strength and flexural modulus, respectively. On the other hand, they concluded that the use of pretreated and undried wood chips lead to the highest aspect ratio after compounding. The effect of composition and the incorporation... 

Keywords compatibilizer, flax, natural fibers, natural fiber composites, processing, recycling, moisture content. 

In Sections 24.3 and 24.5 the flammability and fire resistance of individual fiber/fabric type are discussed. However, as also discussed before, the fire resistance of a fabric not only depends upon the nature of components and the FR treatments applied, but also on fabric area density, construction, air permeability, and moisture content. Nonwovens, for example, will have superior properties to woven or knitted structure, even if all other variables are kept the same.93 The air entrapped within the interstices of any fabric structure and between layers of fabrics within a garment assembly provides the real thermal insulation. For effective thermal and fire resistance in a fabric structure, these insulating air domains need to be maintained.22 In general, for protective clothing and fire-block materials, for best performance multilayered fabric structures are employed. The assembly structures can be engineered to maximize their performance. It is beyond the scope of this chapter to go into details of these composite structures hence the reader is referred to the literature on specified applications and products available. 

Figure 8.18 shows the effect of moisture content on the flexural strength of a composite. The hygroscopic nature of both the fiber and the matrix contribute to the deterioration of the composite. 

In both studies shown above, the authors dried the hybrid fiber mat prior to molding. The importance of the drying stage lies in the fact that the high content of moisture of natural fibers is detrimental for the properties of the composite [2], since, in combination with the hydrophobic character of the polymer matrix, is responsible for void formation and weak adhesion [59]. 

Natural fiber/PP-composites absorb moisture from the environment. This moisture absorption does not lead to a change in width or length but to an alteration in thickness (about 1% at 1% water absorption). The tensile and flexural properties depend also on the moisture content. So the effects of water uptake are only partly reversible. The relative... 

All natural fibers are hydrophihc and their moisture content ranges from 3 to 13%. This leads to a very poor interface between natural fiber and the hydrophobic matrix and very poor moisture resistance. Several fiber surface treatments are used to improve the interface viz-thermal treatment, chemical treatment, and use of coupling agents (Bledzki and Gassan, 1999). Fillers are added to composites for technical and chemical reasons (Milewski and Katz, 1980). Calcium carbonate has maximum usage as filler in plastics and FRP due to its low cost, non-toxicity and lack of odor. Present work gives effectiveness of jute fabric treatment and addition of filler on properties of jute reinforced polyester composites (JFRP). 

The acetylation treatment decreases the hydrophilic nature of the plant fibers. During the acetylation treatment the hydroxyl groups in the cellulosic fiber are replaced with acetyl functional groups. The decrease in hydrophilicity results in lower moisture intake and stronger interfacial bonding [8]. De Rosa et al. [15] obtained lower water content in acetylated okra fibers compared to untreated ones. Hill and Khalil [72] reported that the acetylation treatment enhanced the bioresistance of coir and oil palm fiber-reinforced polyester composites. 

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