Degradation Mechanism And High Value Recycling Of Recycled PC/ABS Alloys

Polycarbonate/acrylonitrile–butadiene–styrene(PC/ABS)alloys are commercial polymer blends that have the combined advantages of PC and ABS.In PC/ABS blends,PC contributes good toughness and heat-distortion temperature properties,whereas ABS improves the processability and reduces the costs of the blends.Therefore,PC/ABS is widely used in the automotive industry,cell phone housings,office supplies,and household appliances.During the use of PC/ABS alloys,under the influence of light,heat and oxygen,the internal molecular chain and phase structure of them have been destroyed,which will affect mechanical properties of the products.In this paper,the changes of molecular chains and phase structure of PC/ABS alloys during natural aging degradation were studied.Based on this,the modification method of recycled PC/ABS(R-PC/ABS)alloys was proposed.Then,the styrene–butadiene–glycidyl methacrylate(SBG)and R-PC/ABS were prepared using melting extrusion,which improve the the strength,toughness and compatibility of R-PC/ABS by chain extension reactions.The properties of the modified R-PC/ABS alloys were studied by six times of melt extrusion,and the changes of various properties with the increase of extrusion times were characterized.The details are as follows:Compared the properties of R-PC/ABS with the new PC/ABS(N-PC/ABS)alloys,the following conclusions were drawn:In the process of natural aging degradation,the ester groups in PC phase and C=C double bonds in ABS phase were oxidized to form carboxyl and hydroxyl groups.However,the nitrile groups in ABS were relatively stable.The molecular weight of R-PC/ABS were reduced significantly after degradation.Both the PC phase and ABS phase degraded,and the decrease in ABS was more serious than PC.The compatibility between the PC phase and ABS phase was also reduced,due to the phase interface between the two phases was destroyed and the interfacial tension was increased.Therefore,the macroscopic mechanical properties of the R-PC/ABS alloys were decresed especially the impact strength.To improve the utilization efficiency of R-PC/ABS,we studied the mechanical,morphological,and rheological properties of R-PC/ABS with SBG,which was used to reinforce,toughen and compatibilized the R-PC/ABS through chemical compatibilization.Fourier transform infrared spectroscopy(FT-IR)demonstrated that carboxyl and hydroxyl groups in R-PC/ABS reacted with epoxy groups in SBG to produce ester and ether groups.The results of scanning electron microscopy(SEM)showed that the domain sizes of the ABS particles decreased when the SBG content was 6 wt%;this demonstrated that the compatibility of the polycarbonate(PC)and ABS was improved after the addition of SBG.The results of the loss modulus of dynamic mechanical analysis(DMA)were consistent with the morphological results,which reflected a better compatibility of PC and ABS in the modified samples.The introduction of SBG increased the molecular weight and entanglements;this improved the viscosity and storage modulus in the modified samples,as demonstrated by the rheological results.Furthermore,the mechanical properties were obviously enhanced,especially the impact strength,when the SBG content was 6 wt%;this was ascribed to the chemical reactions and improved compatibility after melt extrusion with SBG.The mechanical properties and microstructure of the modified sample R-PC/ABS/SBG(6 wt%)was studied by multiple extrusions.The results of FT-IR showed that the peakvalue change of the absorption peak of each characteristic was not obvious.As the number of extrusions increased,the change in tensile strength and flexural strength in R-PC/ABS/SBG(6 wt%)was not significant,but the impact strength gradually decreased.The results of scanning electron microscopy showed that the compatibility and the interfacial adhesion between the PC and the ABS phase was gradually destroyed as extrusions times increased,and the interfacial tension gradually increases.The results of DMA also demonstrated that multiple extrusions disrupted the compatibility between the PC and the ABS phase.The glass-transition temperature(T_g)peak of the PB phase of the R-PC/ABS/SBG(6 wt%)extruded at the sixth time shifted toward the low temperature direction,and a small"shoulder"appeared on the left of the T_g peak of the PC and the SAN phase.The color of R-PC/ABS/SBG(6 wt%)after the third extrusion began to turn yellow gradually.As the times of extrusions increased,the color gradually turned yellow and deep,but theimpact strength ofR-PC/ABS/SBG(6 wt%)still been not bad.