Research On The Recycle Of Materials In Waste Printed Circuit Boards

With the development of science and technology, the increasingly growing of WEEE (Waste Electrical and Electronic Equipment) has been constituted a serious threat to the natural ecological environment. In view of the environmental problem induced by WEEE and the high residual value of the materials contained in WEEE, such as precious metal, metal, plastic and glass, the recycling of WEEE is attracting widespread attention. PCB (Printed Circuit Board) is used as a basic and important combination part of electronic components. The effective recycle technology of PCB is important for the reutilization of WEEE.The recycling process of waste PCB has been studied. By using the specially designed gas-solid fluidization separation apparatus, a mechanical process including dismantling, crushing, and classification has been developed to separate and enrich metals and non-metals from waste PCB. The state of materials after crushing and separation, distribution of materials size, and effects of the operating air speeds on the enrichment performance of the metals were investigated. The waste PCB materials can be crushed with the particle size below 1.25mm using the high speed revolving hammer type grinder. Crushed materials were separated into 8 particle sizes using the Taylor standard sieve. Through the microscope, metals and nonmetals whose size was below 1.0mm were observed to be separated. The content of different particle sizes was detected by microwave digestion and ICP-AES, which can find out copper takes 26.75% of the total metals content, and the maximum metal content is in the 0.125～0.3mm, 0.3～0.5mm and 0.5～0.8mm, illustrating that the separation technology was a preliminary enrichment process. The different optimal operating air speed at the different particle sizes were identified by calculating the recovery and integrated fractional efficiency of TM (total metal) and Cu: such as the optimal operating air speeds were 0.78～0.85m/s and 1.27～1.41m/s about 0.125～0.3mm and 0.3～0.5mm respectively, and the recovery of metal was above 95% at the optimal air speed. In conclusion, it is feasible and effective that fluid technology applied in separated and selective enrichment of crushed materials of the waste PCB.On the basis of fluid separation technology, by using nonmetal powders filling polypropylene (PP) for making composites, using nonmetal powders whose particle size is between 0.125～0.3mm as fillers, a physical method has been developed for reusing nonmetal powders which are recovered by the fluid separation technology. The effects of filler content and size, the compatibilizer content on the mechanical performance and some physical properties of the composites were investigated. Simply blending of the nonmetal powders and PP would results in the significant decline of the composites' mechanical properties. The composites with smaller filler size display better mechanical performance than those with larger filler size. The results show that maleic anhydride-grafted polypropylene (MAH-g-PP) could enhance the interfacial compatibility and adhesion between PP matrix and nonmetal fillers, leading to higher mechanical performance. After adding 2.5% MAH-g-PP, with the nonmetal powders content of 20%, the stretching, bending and impact strength are enhanced by 36%, 14%, and 35% respectively. Compared with the composites filled with traditional fillers, such as talc and CaCO₃ powder, composites filled with nonmetal powders exhibit light gravity, waterproof and high hardness besides the equivalent mechanical performance, which have a good application perspective.