Composite material production of nonmetallic printed circuit board waste with recycled high density polyethylene

Abstract

This research is intended to develop a new potential reuse of recovered nonmetallic materials of printed circuit boards (PCBs) and plastic waste. Recycling of these wastes are being attempted in order to reduce its harmful effects on the environment. In fact, due to ever increasing environmental concerns and disposal costs, reuse and recycling of nonmetallic fractions from PCB wastes are considered as the best treatment practices. The study includes a process for encapsulation by combining dry nonmetallic PCB powder and recycled High Density Polyethylene (rHDPE) in an extruder to form a homogenous matrix and subsequently, compression molded into specimens in order to examine leachability, mechanical, morphological, thermal and weathering properties of the composites. The optimum nonmetallic PCB particle size with balanced mechanical properties was 0.07-0.09 mm. The leachability of raw nonmetallic PCB was tested by performing Toxicity Characteristics Leaching Procedure (TCLP) and Total Threshold Limit Concentration (TTLC). Subsequently, for rHDPE/PCB composites, the loadings of nonmetallic PCBs were varied from 10-50 wt%. Composites with 40 wt% nonmetallic PCB content showed the best balance of stiffness, strength and toughness with flexural modulus of 17.0 and 16.3 GPa and impact strength of 42.3 and 41.9 J/m for sample A and B, respectively. It was observed that, the addition of 6 phr maleated polyethylene (MAPE) has improved the flexural modulus and impact strength by 69% and 25%, respectively. Scanning electron microscopy (SEM) revealed that addition of compatibilizer improved the interfacial adhesion of the nonmetallic PCB material and polymer matrix. Encapsulation process has successfully entrapped and immobilized the residual metals from leaching out to the surrounding environment. After the nonmetallic PCB was filled in rHDPE composites with composition of 50 wt%, the concentration of Cu leached was far below the regulatory limit with 93.4% and 96% reduction for sample A and B, respectively, compared to raw nonmetallic PCB waste prior encapsulation process. Incorporation of nonmetallic PCB fillers in rHDPE reduced the thermal stability as the decomposition occured at lower temperature and melting temperature (Tm) also occured at lower temperature compared to the neat unfilled rHDPE. By adding 6 phr MAPE, Tm shifted to even lower temperature. The degree of degradation due to weathering increases with the time of exposure. Prolong exposure caused loss of mechanical properties of all the composites with and without compatibilizer. However, the rHDPE/PCB composites are more resistable to weathering attacks as compared to unfilled neat rHDPE. Water absorption of all the rHDPE/PCB composites reduced with addition of nonmetallic PCB material.