Conifer fibers as reinforcing materials for polypropylene-based composites

Conifer fibers were used to reinforce polypropylene (PP). To improve the co mpatibility between the conifer fibers and the PP matrix, the fibers were e ither grafted with maleated PP (MAPP), treated by adding MAPP, or mixed wit h ethylene/propylene/diene terpolymer (EPDM). The treatments resulted in im proved processing, as well as improvements in the thermal and mechanical pr operties of the resultant composites compared with the composites filled wi th untreated conifer fibers. Moreover, MAPP grafting and MAPP treating disp layed more obvious benefits than EPDM treating in terms of thermal properti es, processing flowability, and tensile strength improvements. EPDM treatin g also produced more significant benefits than either MAPP grafting or MAPP treating in terms of impact strength and tensile elongation improvements. These improvements were attributed to surface coating of the fibers when EP DM was used. In addition, the effect of the concentration of the conifer fi bers on the properties of the composites and the difference between MAPP gr afting and MAPP treating were evaluated. (C) 2001 John Wiley & Sons, Inc.