Kinetics of free radical polymerization of bisphenol A diglycidyl ether diacrylate initiated by barbituric acid

• EA/BTA radical polymerization kinetics studied via model-fitting method.
• Hydroquinone used as a probe to study EA/BTA polymerization mechanisms.
• Major differences between BTA and BPO in initiating EA polymerization illustrated.
• A mechanism involving nucleation and growth of microgel nuclei proposed.
• Microgel formation governed by propagation and diffusion-controlled termination.

Non-isothermal radical polymerization kinetics for barbituric acid (BTA)/epoxy diacrylate (EA) and benzoyl peroxide (BPO)/EA (serving as the reference) in NMP were investigated. The DSC data showed that the activation energy of the polymerization of EA initiated by BTA was much lower than that initiated by BPO. For polymerizations of BTA/EA and BPO/EA except BPO/EA = 3/100 (w/w), the reaction mechanism involving nucleation, followed by nucleus growth in the first stage was proposed. For the polymerization of BPO/EA [3/100 (w/w)], the reaction system was adequately described by the instantaneous nucleation and nucleus growth mechanisms in the first stage. Moreover, the nucleation and subsequent growth of microgel nuclei were primarily governed by the propagation reaction and diffusion-controlled termination reaction for the polymerization system of BTA/EA or BPO/EA. In the second stage (in the conversion range 0.75–0.90), the diffusion-controlled propagation and termination reactions governed the development of highly crosslinked macrogel (i.e., macroscopic agglomerate).