Study On The Structure And Properties Of Compatibilizing Waste Household Appliances PP And HIPS Blends

Polypropylene(PP)and high impact polystyrene(HIPS),with excellent performance,are two kinds of plastics commonly used in household electrical appliances.However,The sorting process of recycled PP(R-PP)and recycled HIPS(R-HIPS)is time-consuming,laborious and inefficient,which is due to their similarity in appearance and affects their recycling and reuse.If R-PP and R-HIPS are made into composite materials,it would be significant for recycling the waste plastics of household appliances.Nevertheless,R-PP and R-HIPS are incompatible.Simple melt blending could not obtain the composites of superior properties.Therefore,the key to preparing R-PP/R-HIPS blends is to improve their properties by improving the compatibility of the blends.In this paper,the degradation of R-PP and R-HIPS under natural conditions were studied by MFR,GPC,FTIR,SEM,the testing of gel content,graft ratio and mechanical properties.The compatibility between R-PP and R-HIPS was studied by SEM,DSC and mechanical property test.Compared with V-PP,the MFR value and mechanical properties of R-PP decreased,the gel content of R-PP increased.Compared with V-HIPS,the MFR,M _n,M _w,gel content,grafting ratio and mechanical properties of R-HIPS decreased.The interface between PB and PS phases was clear.Moreover,the FTIR spectra of R-PP and R-HIPS had the absorption peak of carbonyl and hydroxyl group in carboxyl compared with V-PP and V-HIPS.These results showed that the aging of PP and HIPS under natural conditions led to molecular chain breaking and molecular weight decreasing,which resulting in the decline of mechanical properties.Meanwhile,the carbonyl and carboxyl groups were formed.Compared with V-PP/V-HIPS blends,the dispersion of dispersed phase in R-PP/R-HIPS blends was more uniform and the particle size of dispersed phase was smaller.Tg of R-PP and PS in R-HIPS was close to each other and the impact strength of R-PP/R-HIPS blends was higher.These indicate that the compatibility between R-PP and R-HIPS is better than that of V-PP and V-HIPS,which may be due to the formation of hydrogen bonds between carbonyl and carboxyl groups in R-PP and R-HIPS.Then,SEP and SEPS were added to R-PP/R-HIPS blends to improve the physical compatibility.This is because SEP and SEPS contain P(E/P)blocks and PS blocks which are similar to R-PP and the PS in R-HIPS.When the content of SEP or SEPS is 10 wt%,the notch impact strength of R-PP/R-HIPS blends is significantly higher than that without compatibilization.The dispersion of dispersed phase is more uniform,the particle size decreases,and the viscosity of blends increases compared to the uncompatibilizing blends.The glass transition temperature of R-PP is close to that of the PS phase in R-HIPS,indicating that SEP and SEPS can improve the phase interface of R-PP/R-HIPS blends and then improve the physical compatibility of R-PP and R-HIPS.Afterwards,SEPS-g-GMA copolymer was prepared by free radical grafting reaction and was used to improve the compatibility of R-PP/R-HIPS blends through carboxyl groups of R-PP and PS phase in R-HIPS.The epoxy group in SEPS-g-GMA can reacted with the carboxyl group in R-PP and R-HIPS,which formed the ester group.Hence,R-PP and the PB phase in R-HIPS were connected by chemical reaction.When the graft ratio of SEPS-g-GMA(10 wt%)was 2.44%,notch impact strength and elongation at break of the blends were 7.06kJ/m~2 and 34.25%,which increased by 186.99%and 68.30%compared with the blends without compatibilizer,respectively.This indicated that the synergistic effect of SEPS-g-GMA copolymer on physical compatibilization and chemical compatibilization of the blends was significant.Moreover,by changing reaction sequence,the epoxide groups of GMA reacted with the carboxyl groups in R-PP and PB phase of R-HIPS firstly.Then,the carbon-carbon double bonds in GMA reacted with the tertiary carbon free radicals in SEPS under the initiation of DCP through theco-monomer NVP.Thus the synergistic effect of physical compatibilization and chemical compatibilization in R-PP/R-HIPS blends would be realized.When the NVP content was 0.50 wt%,the notch impact strength and elongation at break of R-PP/R-HIPS blends reached 6.89 kJ/m~2 and 31.28%,which were 180.08%and 53.71%higher than that of the uncompatibilizing blends,respectively.The compatibilization of R-PP/R-HIPS blends has been achieved by the above methods.Among them,the synergistic compatibilization effect of SEPS and GMA on R-PP/R-HIPS blends(i.e.the physical compatibilization of SEPS on R-PP and PS phase in R-HIPS,the chemical compatibilization of GMA and SEPS on R-PP and PB in R-HIPS)is especially significant in different reaction order.Through these two synergistic compatibilization methods,mechanical properties,phase interface,?~*,G?,G?and thermal stability of R-PP/R-HIPS blends were improved significantly.Thus the excellent properties of R-PP/R-HIPS blends were obtained,which provided a new way for the high value recovery and reutilization of R-PP and R-HIPS.