The morphological characteristics of waste polyvinyl chloride(PVC)plastics during its pyrolysis from ambient temperature to 500℃ were investigated with a purpose to obtain the morphological parameters characterizing reaction stages.PVC granules and films were used as typical waste PVC plastics for testing

and influence of impurities was also investigated.During experiments the image changes of PVC were recorded with a high-speed infrared camera

quantitative morphological parameters were explored with the help of a digital image processing software "Image Pro Plus(v6.3)".Two representative morphological signals describing the pyrolysis stages were obtained:pixel area(PA)and bubble ratio(BR).Experimental results showed that plastics pyrolysis involved four stages:melting

two stages of decomposition and a quasi-stable stage in between.For both PVC films and granules

the BR curve could always reflect reaction stages and reaction intensity

while PA could be used as key signal of complete HCl release.The shape of original PVC materials only affected the melting stage.When impurities were involved

the BR curve showed that intense decomposition started earlier at a lower temperature

but overall morphological characteristics remained the same.The morphological signal obtained here could be used as a guide to control dechlorination process of waste PVC and to make a better reactor design.