Thermal cracking of waste printed wiring boards for mechanical recycling by using residual steam preprocessing  

作　　者：Yao CHEN Jinhui LI Huabo DUAN Zhishi WANG 

机构地区：[1]School of Environment,Tsinghua University,Beijing 100084,China [2]Faculty of Science and Technology,University of Macao,Macao 999078,China

出　　处：《Frontiers of Environmental Science & Engineering》2011年第2期167-174,共8页环境科学与工程前沿（英文）

基　　金：This study was funded by the project from the National Natural Science Foundation of China(Grant No.20777043/B070204);the National Science and Technology Support Program(2006BAC02A18).

摘　　要：Mechanical waste-processing methods,whichcombine crushing and separation processes for therecovery of valuable materials,have been widely appliedin waste printed wiring board(PWB)treatment.However,both the high impact toughness and the tensile and flexuralstrengths of whole PWB with a laminated structure resultin great energy consumption and severe abrasion of thecutters during multi-level crushing.In addition,the hightemperatures occurring in continual crushing probablycause the decomposition of the polymer matrix.A thermalcrackmethod using residual steam as the heating mediumhas been developed to pre-treat waste PWBs.Thistreatment reduces the mechanical strength in order toimprove the recovery rate of valuable materials insubsequent mechanical recycling.The changes of thePWBs’macro-mechanical properties were studied toevaluate thermal expansion impacts associated withchanges in temperature,and the dynamic dislocationmicro-structures were observed to identify the fracturemechanism.The results showed that thermal cracking withsteam at the temperature of 500 K can effectively attenuatethe mechanical properties of waste PWBs,by reducing theimpact,tensile and flexural strengths respectively,by59.2%,49.3%and 51.4%,compared to untreated PWB.Thermal expansion can also facilitate the separation ofcopper from glass fiber by reducing peel resistance by95.4%at 500 K.It was revealed that the flexural fracturewas a transverse cracking caused by concentrated stresswhen the heating temperature was less than 500 K,andshifted to a vertical cracking after exceeding 500 K.

关 键 词：waste printed wiring board(PWB) residue steam thermal-crack mechanical properties 

分 类 号：TG1[金属学及工艺—金属学]