The photo-degradation of polymethylmethacrylate I. The mechanism of degradation

Abstract

On exposure to ultra-violet light of wave-length 2537 Å, polymethylmethacrylate degrades rapidly to monomer at temperatures above 130° C in vacuo . The general features of this reaction are described, and the behaviour of polymethylmethacrylate compared with that of other vinyl polymers under similar conditions. The diffusion of monomer through polymethylmethacrylate is a comparatively slow process. The effect of this on the experimental results is described, and the limited conditions under which true rates of degradation can be measured are outlined. The overall quantum efficiency of the photo-degradation reaction is greater than 10 2 , and the intensity exponent about 0·5 for most samples. Number-average molecular weights of samples of degraded polymers have been measured, the results being similar to those obtained in an earlier study of the thermal-degradation. The results show that the mechanism of degradation is a true depolymerization process, involving initiation, a depropagation reaction, and (under most circumstances) mutual termination of reaction chains.

Molecular weights of thermally degraded polymethyl methacrylate

“…This may be called "termination by free-radical d epletion. " Eliminating [p.] b etween eq (3) and (7),…”

Infrared Spectroscopic Studies on Some Thermally Degraded Poly(methyl methacrylate) Doped with N,N,N´,N´- tetraoxaloyl Para Sulphanilamide

“…The pure PMMA samples and PMMA doped with different percentages of the prepared organic dopant were thermally treated by using Muffle Furnace (Model CLF-M25.DAIHAN Scientific, Co. Ltd) under nitrogen atmosphere, taking into consideration the concepts of Cowley et al (53) experiment during the PMMA thermal treatment. The thin films of PMMA which had a thickness of 500 µm are subjected to thermal treatment between two plates of Aluminum connected to thermocouple at the required temperature to avoid temperature ingredient in the tested samples.…”