ISSN:
0887-624X
Keywords:
acrylated silicones
;
radical photocrosslinking
;
polymerization kinetics
;
oxygen effect
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The photoinduced radical crosslinking of silicones containing pendant acrylate and methacrylate groups has been investigated with calorimetric and ESR measurements. Oxygen very strongly influences this process, which leads to a prolonged induction period and a pseudo first-order termination reaction between polymer radicals and oxygen. Kinetically, such reaction steps are responsible for light intensity and monomer exponents, both of unity. In the absence of oxygen, second-order processes take place between polymer and primary radicals. The results of conversion-time and reaction-rate time measurements using stationary irradiations and postpolymerization experiments agree with the corresponding kinetic expressions. Long-lived polymer radicals and their decay have also been determined with ESR techniques. Long-chain spacer groups, which link the unsaturated ester moiety at the silicone backbone, increase the crosslinking rate. The final conversions of the double bonds exceed high values in each case. © 1992 John Wiley & Sons, Inc.
Additional Material:
13 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pola.1992.080301311
Permalink
