Studies on the kinetics of free‐radical bulk polymerization of multifunctional acrylates by dynamic differential scanning calorimetry

Abstract

The course and kinetics of nonisothermal bulk polymerization of multifunctional acrylates were studied by dynamic differential scanning calorimetry (DSC). Measurements were carried out for four straight‐chain monomers, diethylene glycol diacrylate (DEGDA), triethylene glycol diacrylate (TEGDA), tetraethylene glycol diacrylate (TTGDA), and poly(ethylene glycol)diacrylate (PEGDA) (mol. wt. 600), to study the effect of the backbone chain length, atmosphere, and type of initiator on the crosslinking kinetics. 4,4′‐Azobis(4‐cyanovaleric acid) (1.0%, w/w) was used as a free‐radical initiator. From the dynamic scanning of polymerization of DEGDA at five heating rates (2–30°C/min), the average heat of polymerization (ΔH_p) was found to be 524.2 J/g. An activation energy of 108.8 kJ/mol and preexponential factor 5.34 × 10¹² s⁻¹ were obtained from the Arrhenius plot, In dα/dt. The rate of polymerization 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 the theory of oxygen inhibition. Different types of initiators, e.g., 4,4′‐azobis(4‐cyanovaleric acid) (ABCVA), 2,2′‐azobisisobutyronitrile (AIBN), and benzoyl peroxide (BPO) were used for polymerization and ABCVA was found to be the most efficient among all. © 1995 John Wiley & Sons, Inc.