Chemical Pretreatments of Lignocellulosic Fibres

Natural fibre modification relies on chemical and physical techniques to improve the interfacial interactions between the polyethylene matrix and the natural phase. The principal chemical and physical routes explored in polyethylene lignocellulosic fibre composites can be summarized as follows  

Alkali treatment Mercerization or alkali treatment with strong alkali bases was developed as a method for cotton fibre modification by John Mercerin 1850 [55], It is a common method to produce high quality natural fibres, by removing the natural and artificial impurities from the fibre surface. The chemical treatment reduces the fibre diameter and thereby increases the aspect ratio [26]. Mercerization is usually performed applying aqueous solutions of sodium hydroxide (NaOH), at reaction times of 30 min up to 3 hr. 

Peroxide treatment Natural fibres are immersed in a solution of dicumyl (or benzoyl) peroxide in acetone for about half an hour, then decanted and dried [123]. Recent studies have highlighted significant improvements in the mechanical properties. In a study of polyethylene hybrid composites, sisal and glass fibres were proposed to reinforce the matrix in terms of tensile strength and modulus. Among different chemical treatments, benzoyl peroxide treated fibres revealed to be more successful. This was attributed to the peroxide-initiated grafting of polyethylene on to the fibres [124]. 

The tensile properties of polyethylene composites were improved and it was observed an increase in the hydropho-bicity of the fibre [133]. 

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