Abstract:

Modified carbon black was obtained bytreating N990 in CO₂ at high temperature, and its PE HD composites were then prepared. Treated carbon blacks were characterized with BET, SEM and XPS. The effect of CO₂ treatment on the structure and electric property of N990, as well as PTC prop- erties ofits compositeswereinvestigated.The results show that treated carbon black, as compared with the untreated one, keeps its original inner structure, but can increase its conductivity by more than 1 time nitrogen surface area by more than4times, new pores within 10~30A in size by more than 6 times on its surface,and decreases its surface oxygen by 36.6 %. Room resistivity of treated N990 com- posite can decrease by 0.6 to 3 orders of magnitude compared with that of the untreated one, though PTCintensity also deceases byzero to 60.1%.However, composites exhibiting low room resistivity and relative high PTC intensity can be attained by loading suitable weigh of treated N990.

Key words: composite, positive temperature coefficiency, carbon black, carbon dioxide treatment;surface structure, high density polyethylene