| Technological innovation and intense marketing engender a rapid replacement process of electrical and electronic equipment (EEE), which makes the problem of treatment and recycling of waste electrical and electronic equipment (WEEE) more and more important and pressing. The printed circuit boards (PCBs) are the basis of all EEE, and thus are one of the most important branches of WEEE stream. There are plenty of toxic materials including heavy metal and BFRs that can be easily found in PCBs and they will cause huge damage to the environment if they are not treated properly. The major economic driving force for recycling of waste PCBs is the value of the metals of PCBs. The nonmetals which take up almost 70 wt% of waste PCBs were treated by combustion or land-filling in the past. However, combustion of the NMFs will cause the formation of highly toxic polybrominated dibenzodioxins and dibenzofurans (PBDD/Fs) while land-filling will take up a mass of land, raise the cost of recycling of waste PCBs, and waste valuable resources.Therefore, according to the"reduce, recycle, reuse"solid waste treatment principle, mechanical-physical methods are used to recycle the nonmetals reclaimed from waste PCBs in this paper. Waste PCBs were first pulverized by two step processes and then separated by corona electrostatic separator. The nonmetals separated from pulverized waste PCBs were used as raw materials to produce unsaturated polyester (UP) bulk molding compound (BMC) and modified asphalt. The impacts of molding temperature and molding time, and the influences of nonmetals particle size and adding content on properties of UP-BMC were investigated. The nonmetals were used as a new modifier for asphalt. The influences of nonmetals particle size and adding content on properties of asphalt were studied, which were chosen to make the asphalt with the best overall properties. The high temperature and low temperature performance improvement of asphalt was analyzed. The distribution of nonmetals particle size is not successive, and the main size regions are 50μm - 91μm and 125μm - 150μm, which represents 58 wt% and 25 wt%, respectively. The onset thermal degradation temperature is 323°C, and the fastest thermal degradation temperature is 343°C, and the residue content is 33.4 wt% at 800°C.The optimal molding conditions for UP-BMC filled with the nonmetals were as follows: the top and bottom mold temperature was 140°C and 135°C, respectively; the molding time was 5 min.There was a maximum value both for the impact strength and flexural strength of UP-BMC filled with the nonmetals, which corresponded to 20 wt % for the nonmetals addition. It appeared two extremums corresponding to 10 wt % and 30 wt % that were for Rockwell hardness of UP-BMC filled with the nonmetals appeared. When the addition of the nonmetals is 20 wt% and the particle size is <0.07 mm, the mechanical performance of UP-BMC is best, with impact strength, flexural strength, Rockwell hardness being 6.4 kJ/m2, 68.8 MPa,and 89.0 HRM.It is indicated by SEM analysis that the glass fiber contained in the nonmetals appears in single form and distribute equably in UP-BMC filled with the nonmetals, the bonding between the nonmetals and resin matrix is strong enough, and the compatibility between the nonmetals and resin matrix is good.When the nonmetals content is 25 wt% and their particle size group is 0.07-0.09 mm, the overall performance of the NMA is best, which had a viscosity of 1225 cP at 135°C, a penetration of 53.7 dmm at 25°C, a ring and ball softening point of 54°C, a ductility of 43.5 cm at 15°C, a G*/sinδof 3995.27 Pa at 60°C , and an upper limit temperature (G*/sinδ= 1 kPa) of 69.4°C, all of which show that the high temperature performance of asphalt is improved significantly.To sum up, the nonmetals from waste PCBs were recycled successfully in different areas in this paper, which provides novel ways to resolve the environment problem caused by the nonmetals from waste PCBs, and thus has fulfilled the resource saving and environmental protection purpose. |
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