Abstract
The effect of residual lignin content on the mechanical strength and water absorption of kraft pulp/ polypropylene composites was studied. To meet this objective, hornbeam wood chips were converted to kraft pulp at three different alkalinities (15, 20, and 25%) and three different cooking times (60, 90, and 120 min). The residual lignin contents of these pulps were determined according to the TAPPI standard. Kraft pulp was mixed with polypropylene (PP) at 50% weight ratios. The amount of maleic anhydride (MAPP) coupling agent was fixed at 4 per hundred compounds (phc) for all formulations. The results indicated that the lignin residual content decreased with increasing cooking time and alkalinity in kraft pulp. Also, it was found that tensile strength, tensile modulus, flexural strength, and flexural modulus were increased by increasing the alkalinity and cooking time; however, the notched impact strength and water absorption decreased. Overall, decreasing the lignin content had a positive impact on the flexural and tensile properties and had a negative effect on the notched impact strength.
Highlights
Wood-plastic composites (WPC) are a group of materials made from a combination of wood fiber and a thermoplastic resin, together with varying amounts of additives
Results of analysis of variance (ANOVA) indicated that the alkalinity, cooking time, and their interaction effects had a significant influence on the flexural strength, tensile strength, flexural modulus, tensile modulus, impact strength and water absorption of kraft pulp/polypropylene composites (Table 1)
Flexural and Tensile strength The influence of alkalinity and cooking time on the flexural strength, flexural modulus, tensile strength, and tensile modulus of kraft pulp/polypropylene composites is shown in Figure 2 to 5
Summary
Wood-plastic composites (WPC) are a group of materials made from a combination of wood fiber (or flour) and a thermoplastic resin, together with varying amounts of additives. Incorporation of wood fibers into plastics improves the flexural and tensile properties of the resulting composite material relative to pure plastics (Kord 2011). Among polymer composites, those based on polypropylene (PP) have attracted considerable interest because polypropylene is one of the most widely used and fastest growing classes of thermoplastics with low cost (Kord 2012). PP has been used in conventional composites for a long time and shows good mechanical properties, even with low amounts of filler (Woodhams et al 1984)
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