1981 Volume 38 Issue 8 Pages 535-540
The progress of degradation has been studied for polyethylene sheet (3mm thick) irradiated by a “sunshinetype” carbon-arc weathering tester, without spraying water. Layers of constant thickness (0.05 or 0.1mm) were scraped, by means of a side-milling cutter mounted on a notching machine. Powdered sample from each layer collected was subjected to various testings, infrared spectroscopy (IR), differential scanning calorimetry (DSC) and density measurement. The formation of carbonyl group was distinguished in the surface region and the rate was much faster than that in the inner regions, suggesting different mechanisms for the formation. The density increased and the melting temperature decreased by the exposure and the change was remarkable in surface layers. Vicker's hardness number measured on each layer surface increased in accordance with the formation of carbonyl group.
