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...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.展开更多
常温粉碎废弃电路板易产生许多问题,如冲击热解、有害气体产生和较低的粉碎效率等,本文设计并建立了实验室液氮低温冷冻粉碎系统,研究了不同温度、不同冷冻时间对破碎产品累积产率、颗粒表面形态和性质、解离度以及粉碎效果综合指标的影...常温粉碎废弃电路板易产生许多问题,如冲击热解、有害气体产生和较低的粉碎效率等,本文设计并建立了实验室液氮低温冷冻粉碎系统,研究了不同温度、不同冷冻时间对破碎产品累积产率、颗粒表面形态和性质、解离度以及粉碎效果综合指标的影响.结果表明,低温冷冻使线路板表现出脆性,在预冷温度为-120℃,冷冻时间为5 m in时,可以获得较多细粒级产品、较平滑的颗粒表面和较高的解离度.展开更多
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).
文摘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.
文摘常温粉碎废弃电路板易产生许多问题,如冲击热解、有害气体产生和较低的粉碎效率等,本文设计并建立了实验室液氮低温冷冻粉碎系统,研究了不同温度、不同冷冻时间对破碎产品累积产率、颗粒表面形态和性质、解离度以及粉碎效果综合指标的影响.结果表明,低温冷冻使线路板表现出脆性,在预冷温度为-120℃,冷冻时间为5 m in时,可以获得较多细粒级产品、较平滑的颗粒表面和较高的解离度.
