STUDIES ON THE KINETICS OF FREE-RADICAL BULK-POLYMERIZATION OF MULTIFUNCTIONAL ACRYLATES BY DYNAMIC DIFFERENTIAL SCANNING CALORIMETRY

The course and kinetics of nonisothermal bulk polymerization of multif unctional acrylates were studied by dynamic differential scanning calo rimetry (DSC). Measurements were carried out for four straight-chain m onomers, diethylene glycol diacrylate (DEGDA), triethylene glycol diac rylate (TEGDA), tetraethylene glycol diacrylate (TTGDA), and poly(ethy lene glycol)diacrylate (PEGDA) (mol. wt. 600), to study the effect of the backbone chain length, atmosphere, and type of initiator on the cr osslinking kinetics. 4,4'-Azobis(4-cyanovaleric acid) (1.0%, w/w) was used as a free-radical initiator. From the dynamic scanning of polymer ization of DEGDA at five heating rates (2-30 degrees C/min), the avera ge heat of polymerization (Delta H-p) was found to be 524.2 J/g. An ac tivation energy of 108.8 kJ/mol and preexponential factor 5.34 X 10(12 ) s(-1) were obtained from the Arrhenius plot, In da/dt. The rate of p olymerization was found manyfold greater at 20-60% conversion than at the initial stage (2-8% conversion). Polymerization was studied under both nitrogen and air atmosphere. The results corresponded well with t he theory of oxygen inhibition. Different types of initiators, e.g., 4 ,4'-azobis (4-cyanovaleric acid) (ABCVA), 2,2'-azobis-isobutyronitrile (AIBN), and benzoyl peroxide (BPO) were used for polymerization and A BCVA was found to be the most efficient among all. (C) 1995 John Wiley & Sons, Inc.