Impact Behavior of Sawdust/Recycled–PP Composites T. Q. LI, C. N. NG, R. K. Y. LI Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, People’s Republic of China Received 13 March 2000; accepted 2 October 2000 Published online 23 May 2000 ABSTRACT: The instrumented Izod and Charpy tests were performed on the sawdust– polypropylene (PP) composites to study the nature of impact resistance in the thermo- plastic wood composites. The notched Izod strength was found to increase with filler content in composites containing the Maleic–anhydride– grafted PP (MAPP) additive. The Izod strength even exceeds that of the neat matrix resin at higher filler contents, indicating a methodology for applying the recycled PP and also for reinforcing the thermoplastics with wood powders. While the static tensile results show evidences for the reinforcing role of the wood filler, a fracture mechanics characterization through the Charpy impact tests effects of MAPP under the impact loading rates. The choice of MAPP as the additive was discussed accordingly for application of the sort of materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1420 –1428, 2001 Key words: sawdust/recycled-PP composites; Izod test; fracture toughness INTRODUCTION With the growing economic competition and the ecological pressure, the past decade has seen a renewed interest in developing more efficient re- inforcements based on low-cost fillers. Cellulose- based fibers meet such requirements in most as- pects. They are made from recoverable resources themselves, and thus may add degradability to plastics. 1,2 The natural fibers usually have rela- tively high strength and modulus and low-density compared to traditional reinforcements for com- posites, such as E-glass fibers. 3 The versatility and abundance of their resources ensure the low cost of the potential reinforcements. The renaissance of the cellulose fiber compos- ites, however, has been greatly hindered by the available forms of the cellulose fibers. Rather than providing continuous cellulose filaments, which would be the essence of the reinforcement, present techniques produce fibers or fabrics con- sisted of cellulose microfibrils. 3 The situation makes the wood flour a competitive substitute for the cellulose fibers, especially when extrusion compounding and injection molding are adopted as processing methods. The case is especially true when polypropylene, a family of commodity ther- moplastics, the properties of which are the most versatile upon tailoring, 4 is concerned as the ma- trix resin. The promise of using the cellulosic reinforcement, in combination with the consider- ation of plastics recycling, has made the subject of polypropylene–wood fiber or flour blends one of the most widely studied area. A commercial recy- cled PP was selected as matrix resin for this study because it exemplifies an extreme choice of the PP resins. With the technical importance, dispersion of the hydrophilic wood fillers in the hydrophobic PP and the interfacial structures naturally becomes one of the major concerns. Efforts had been made Correspondence to: T. Li (tieqili@wsu.edu) or R. K. Y. Li (aprkyl@ctu.edu.hk). Contract grant sponsor: Committee of Science and Tech- nology of Guangzhou City; contract grant number: 990053. Journal of Applied Polymer Science, Vol. 81, 1420 –1428 (2001) © 2001 John Wiley & Sons, Inc. 1420