Gas chromatograph-mass spectrograph was used to analyze the decomposition products of a new type of cyclic triperoxy initiator(3

6

9-triethyl-3

6

9-trimethyl-1

4

7-triperoxonane

TETMTPA) in ethyl benzene．The major compounds before ethyl benzene are carbon dioxide and aliphatie compounds

such as ethane

propane

butane

ethanol

acetic acid

methyl ethyl ketone

methyl acetate and ethyl acetate

while the compounds after ethyl benzene are all aromatic

such as styrene

isopmpyl benzene

isobutyl benzene

2-phenyl ethanol

methyl phenyl ketone and 2

3-diphenyl butane The decomposition mechanism of TETMTPA was proposed from the structure of these compounds．It is considered that there are three pathways for the decomposition of the initiator：the main one is the homolysis of O一O bond．and the other two are the cleavage of C—C and C一O bonds due to the effect of p-electron on the adjacent radical．In considering the cage effect

it is proposed that the aliphatic compounds from the coupling of free radicals in the cage

while the aromatic compounds form via the chain transfer of the radicals to ethyl benzene outside the cage．In comparison with di-tert-butyl poroxide as a reference initiator．the polymerization rate of styrene initiated by TETMTPA is slower owing to its lower decomposition rate constant and initiator efficiency in the case of same equivalent of peroxy group

but the molecular weight of polystyrene initiated by TETMTPA is higher due to the propagation via di-radical The mechanism of initiation is validated through 1H-NMR spentra and DSC analysis of PS initiated by TETMTPA Based on these principles

polystyrene with hisher molecular weight and considerable polymerization rate may be prepared commercially by using muhifunetional initiators．