Mechanical properties improvement of polypropylene/surface-modified newspaper pulp composites

Abstract

Besides reuse or recycling which are the direct methods to reduce the amount of waste papers such as magazines or newspapers, attempt has been made to use these papers as the reinforcing filler in composite materials. This approach is not only to replace the use of expensive synthetic fibers, but also to increase the value added of these materials. In this work, a newspaper pulp reinforced polypropylene (PP) composite was made. However, the main problem in preparation of this type of composite is the incompatibility and poor interfacial adhesion between the newspaper pulp and PP matrix, resulting in poor mechanical properties. Thus, maleic anhydride grafted polypropylene (MAPP) was used as coupling agent to improve the interfacial bond strength between the two phases. For comparison, the esterification reaction using dodecanoyl chloride was adopted to modify surface of the newspaper pulp prior to mix with the PP matrix. Experimental results revealed that the MAPP was a good coupling for newspaper pulp / PP composites. The mechanical properties of the composites with MAPP were better than the ones without MAPP. Likewise, the surface modification by esterification reaction helped promoting the compatibility between the newspaper pulp and PP. Although, comparing to the MAPP - newspaper pulp / PP composites, the strength of esterified - newspaper pulp / PP composites was lowered; it was found that this surface treatment increased the flexibility, elongation at break and thermal stability of the composites. In conclusion, the polypropylene / 20% newspaper pulp with 10% MAPP by weight of newspaper pulp composite showed the highest mechanical properties.