The suspension polymerization of vinyl chloride (VC) was carried out at 40~70℃ in the composite dispersant system composed of poly(vinyl alcohol) and hydroxypropyl methylcellulose

with N-tert-butyl--phenylnitrone (PBN) as the source of nitroxide radicals and -cumyl peroxyneodecanoate (Lup188) as initiator.The effects of the concentration of Lup188

the concentration of PBN and polymerization temperature on the polymerization kinetics

molecular weight and polydispersity index (PDI) of poly(vinyl chloride) (PVC) were investigated in detail.The kinetics of VC suspension polymerization was monitored by gravimetric method while the molecular weight and its distribution of PVC synthesized were determined by gel permeation chromatography.The results showed that the chain propagation in VC polymerization could be efficiently controlled by adding suitable amount of PBN and Lup188 at a reasonable temperature.The optimal molar ratio of VC

Lup188 and PBN was 1000:7:1.As the polymerization temperature increased

the polymerization rate of VC first increased and then decreased

which was different from the mechanism of common radical polymerization.Simultaneously

the molecular weight of synthesized PVC first increased and then decreased

while the PDI first decreased and then increased.The optimal polymerization temperature was 50℃.At this temperature

the PDI of PVC was 1.7~2.0 and did not change significantly in the range of conversion 3%~50%

which was considerably lower than that in common radical polymerization.However

with the conversion increasing further

the PDI of PVC increased.