Preparation and characterization of polypropylene composites with nonmetallic materials recycled from printed circuit boards

After separation of metals from printed circuit boards (PCBs), they are sent to recycling process; however, significant amounts of useless nonmetallic particles are also included. Recycling useful materials from used PCBs is a major challenging problem that must be solved in China renewable resource industries through harmless and feasible processes. In this article, a novel beta-polypropylene (PP)/nonmetals composite was prepared and evaluated. The nonmetallic particles were treated with calcium pimelate (PA, a beta-nucleating agent for PP) and then compounded with PP through melt blending method. The results show that when cooling and crystallizing from the melt, beta-PP are formed because of the surface effects of PA. This observation is assumed as the source of good rigidity and toughness of prepared PP composites. In the composite containing 10 wt % nonmetallic particles treated with 5 wt % PA, the content of beta-PP was found to be larger than 90% and the impact strength and flexural modulus of PP composite increased by 205.3 and 61.8%, respectively, compared with those of neat PP. Although the addition of PA-modified nonmetals slightly increased the tensile strength of PP, considering all factors, the optimal mass ratio of PP/nonmetals/PA composites to reach optimum mechanical properties was observed as 100/10/0.5. Thus, the application of treated nonmetals to prepare nonmetals/beta-PP composites provides a promising way to recycle PCBs waste and produce useful PP composites.