Abstract:

In order to synthesize silicone- acrylate emulsion with stronger hydrophobicity,polydimethylsiloxane endedwith vinyl terminal groups was synthesized via the cationic miniemulsion polymerization of octamethylcyclotetrasiloxane(D₄ ) monomer,with dodecylbenzene sulfonic acid (DBSA) as the catalyst and with ethenylethoxydimethyl silane(EDEV) as the blocking agent.Then,the effects of polymerization temperature,DBSA dosage,blocking agenttype,EDEV dosage and EDEV addition time on the monomer conversion rate,the latex particle radius and thepolydispersity index (PDI) were investigated.The results indicate that stable polymerization product of siliconeminiemulsion,which is of a radius of 95.3nm,a PDI of 0.123 and a monomer conversion rate of 92.1%,can beobtained via the polymerization at 85 ℃,with a DBSA dosage of 6%,an EDEV dosage of 1.0% and an EDEVaddition time of 3h.FT- IR results show that the blocking agent effectively takes part in the miniemulsion polymeri-zation.TEM analysis indicates that the product is in a nano- structure.Moreover,a model is proposed to predict the D₄ conversion rate of functional polysiloxane varying with the main technological parameters.

Key words: cationic miniemulsion polymerization, octamethylcyclotetrasiloxane, dodecyl benzenesulfonic acid, blocking agent, monomer conversion rate, prediction model