Abstract
Copolymers of n.butyl methacrylate and glycidyl methacrylate (GMA) containing 11, 22, 40 and 51% GMA units were reacted quantitatively with methacrylic acid, producing copolymers with methacrylate side-groups. These copolymers were submitted to photocrosslinking by irradiation at 350 nm in the presence of benzoin isopropyl ether as photoinitiator in the solid state below and above the glass transition temperature of the copolymers. The rate of crosslinking was followed by: 1. (1) Infrared spectrometry by measuring the relative decrease of absorbance of the double bond CC (1640 cm −1). 2. (2) Microcalorimetry on the basis of the initial exothermic peak. 3. (3) By gravimetry by determining the increase of insoluble fraction with time of irradiation. The influence of temperature on the rate of crosslinking was examined above T g . The apparent activation energy of crosslinking varies from 7·5 to 15 kcal mol −1; it is a function of the film thickness because of the influence of segmental motion and viscous flow effects. Increasing the total unsaturation by addition of polyfunctional acrylic ester causes a strong increase in the rate of crosslinking.
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