| Polyphenylene oxide（PPO）has good compatibility with high impact polystyrene（HIPS）,and HIPS can effectively improve the processing flow performance of PPO.HIPS is widely used in many fields due to its excellent performance,and the number of discarded HIPS also increases.During the use of HIPS,the molecular chain will be broken due to external factors such as light,heat,oxygen,etc.,resulting in the decline of HIPS performance.In this paper,the compatibility between PPO and recycled high impact polystyrene（R-HIPS）and the mechanical properties of PPO/R-HIPS blends were studied on the basis of molecular chain structure changes and macroscopic properties of materials before and after HIPS degradation,and the methods to improve the compatibility between PPO and R-HIPS were proposed.The chain expansion modification of R-HIPS using erythritol uses the hydroxyl group in erythritol to react with the carboxyl group produced by ageing of R-HIPS,resulting in an increase in the molecular weight of R-HIPS and a decrease in the polarity of R-HIPS,further improving the compatibility with PPO.Finally,polyphenylene oxide/chain recycled high-impact polystyrene（PPO/C-HIPS）blends were prepared and the effect of styrenebutadiene-styrene block copolymers（SBS）on PPO/C-HIPS blends was also investigated.The results of the study are as follows.:（1）By comparing the mechanical properties and molecular structures of new highimpact polystyrene（N-HIPS）and R-HIPS,it is shown that the mechanical properties of R-HIPS,especially the notched impact strength,have a relatively obvious decline;Infrared spectroscopy（FTIR）and contact angle test results showed that carboxyl groups were generated during the aging process of R-HIPS,and the polarity of R-HIPS increased;Gel chromatography analysis（GPC）test showed that the molecular weight decreased and the molecular weight distribution broadened during the aging process of R-HIPS;The dynamic mechanical analysis（DMA）and scanning electron microscopy（SEM）results of PPO/N-HIPS blends showed that the compatibility of the two phases and the interface adhesion of PPO/R-HIPS blends were worse than that of PPO/N-HIPS blends.The notch-impact strength,tensile strength and elongation at break of PPO/RHIPS blends decreased by 55.7%,20.8% and 14.7%,respectively,compared with PPO/N-HIPS blends.（2）The effect of erythritol as a chain extender on R-HIPS was investigated,and the addition of erythritol made the chain of broken molecules in R-HIPS undergo chain extension,increased the relative molecular mass of R-HIPS,and improved the tensile strength and notch impact strength of R-HIPS.The results of FTIR test and contact angle test showed that the hydroxyl group in butane erythritol reacted with the carboxyl group generated by the aging of R-HIPS to form an ester group,which reduced the polarity of R-HIPS.When the erythritol content was 1 wt%,the comprehensive performance of R-HIPS was the best,and the notched impact strength,tensile strength and elongation at break were 256%,114% and 160% of those without addition,respectively.After erythritol was added,the interfacial bonding strength of PB phase and PS phase of R-HIPS was increased,and the glass transition temperature of PB phase and PS phase was closer than that of PS phase without erythritol,and the material compatibility was improved.（3）PPO/C-HIPS blends were prepared by melt blending of 1 wt% erythritol chainextended R-HIPS and PPO,compared with the PPO/R-HIPS blends,both the tensile strength and the notched impact strength of the PPO/C-HIPS blends were improved.The compatibility of PPO and C-HIPS is better than that of PPO and R-HIPS.After adding SBS,SBS has obvious toughening effect on PPO/C-HIPS blends.It can be seen from the mechanical properties test that the addition of SBS improves the notched impact strength of the PPO/C-HIPS blends.When the SBS content is 20 phr,the notched impact strength of the blends is 186% higher than that without SBS. |
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