Interfacial and mechanical property analysis of waste printed circuit boards subject to thermal shock

Waste printed circuit boards (PCBs) are the focal points for handling electric and electronic waste. In this paper, a thermal shock method was used to pretreat waste PCBs for the improvement of crushing performance. The influence of the thermal shock process on interfacial modification and mechanical property attenuation of PCB waste was studied. The appearance and layer spacing of the basal plane began to change slightly when the temperature reached 200 degrees C. By 250 degrees C, apparent bulging, cracking, and delamination were observed. However, pyrolysis of PCBs occurred when the temperature reached 275 degrees C, where PCBs were carbonized. The thermogravimetric analysis of PCB particles under vacuum showed that 270 degrees C was the starting point of pyrolysis. The tensile and impact strength of PCBs were reduced as shock temperature rose gradually, with a reduction by 2.6 and 16.5%, respectively, at 250 degrees C from its unheated strength. The PCBs that were heated to 250 degrees C achieved 100% liberation, increasing linearly from 13.6% for unheated PCBs through a single-level shear-crusher (2-mm mesh) and resulting in an obvious reduction of 9.5% (dB) in dust and noise at 250 degrees C. These parameters could be helpful for establishing the operational setup for industrial-scale facilities with the aim of achieving a compact process and a highly efficient recovery for waste PCBs compared with those of the traditional combination mechanical technologies.