Mechanical Properties And Aging Resistance Of New High-impact Poly(Vinyl Chloride) Blends

As is well know,rigid poly(vinyl chloride)(PVC) has been widely used in building pipes,window profiles,and plastic siding due to the good overall performance,chemical resistance,flame retardance,low cost,etc.Unfortunately,a fatal limitation for rigid PVC is the propensity for occasional brittle fracture, particularly in presence of impact loads.Additionally,its mechanical properties will quickly deteriorate in conditions of thermal-oxidative and photo-oxidative aging. Consequently,it is of great importance to improve the impact toughness and aging resistance of rigid PVC.The new high-impact rigid PVCs including core-shell acrylics(ACR)/chlorinated polyethylene(CPE)/PVC,high-density polyethylene(HDPE)/CPE/PVC and nano-CaCO₃/ACR/CPE/PVC blends were prepared by melt blending,and their mechanical properties and aging reisitance were investigated,respectively.Moreover, the toughening and aging resistance mechanism were discussed particularly by means of scanning electron microscopy(SEM),dynamic mechanical analyzer(DMA),fourier transform infrared spectroscopy(FT-IR),etc.The following conclusions can be drawn in the paper.1.The impact strength at normal temperature of ACR/CPE/PVC blends was enhanced greatly,with cooperation of the elastomer CPE and Core-shell ACR.With increasing ACR content,ductile-brittle transition point of the blends shifted to a lower temperature,,and intensity of low temperature tanδof the blends also increased obviously,which suggested that there existed significant synergistic effect between ACR and CPE in toughening of PVC.Compared with the CPE/PVC blends, themal-oxidative and photo-oxidative aging resistance of ACR/CPE/PVC blends were enhanced clearly.Furthermore,the polyene index(PI) and gel content(G_el) of the blends gradually increased during thermal-oxidative aging,but the carbonyl index(CI) decresed a little.During photo-oxidative aging,the PI decreased first then increased, whereas the G_el always increased.2.The impact strength of CPE/PVC blends was enhanced significantly by introducing a small amout of HDPE.When HDPE content increased to 3phr,the impact strength of HDPE/CPE/PVC blends reached maximum value.Meantime,the low temperature impact toughness was also improved to some extent.Compared with the CPE/PVC blends,the impact strength retention rate of HDPE/CPE/PVC blends were enhanced remarably during thermal-oxidative and photo-oxidative aging.With increasing HDPE content,aging resistance ability of the blends gradually enhanced, which meant that the aging resistance of CPE/PVC blends was improved significantly due to addition of HDPE.3.The impact properties of CPE/ACR/PVC blends could be improved further when a certain amount of nano-CaCO₃ was added,and the intensity of low temperature tanδof the blends coincided with the changes in impact strength values. There was a negative influence on thermal-oxidative aging resistance of the CPE/ACR/PVC blends after introduction of nano-CaCO₃.However,compared with the ACR/CPE/PVC blends,the impact strength retention rate of nano-CaCO₃/ACR/CPE/PVC blends remarkably increased after photo-oxidative aging.Addionally,the PI,CI and G_el of ACR/CPE/PVC blends efficiently reduced after adding nano-CaCO₃.Those results indicated that nano-CaCO₃ could evidently enhance the photo-oxidative aging resistance of ACR/CPE/PVC blends.