WEATHERING OF HIGH-DENSITY POLYETHYLENE IN DIFFERENT LATITUDES

Weathering tests were carried out on high-density polyethylene (HDPE) at two different latitudes. The chemical change in terms of carbonyl a bsorbance was monitored by Fourier transform infrared spectroscopy (FT IR). The carbonyl index showed a simple correlation with the average a ir temperature for both films exposed in Bandung (7 degrees NL, 108 de grees EL) and Tsukuba (36 degrees NL, 140 degrees EL). Samples exposed in Bandung showed a constant carbonyl group growth throughout the yea r, while in Tsukuba, carbonyl group growth varied during the year. In summer it was about four times that in winter. In both Locations, vari ation of carbonyl group growth was apparently correlated with variatio n of temperature, not directly with solar radiation dose. The thermal properties were observed by differential scanning calorimetry (DSC). T he melting temperatures were constant. The shape and the size of melti ng peaks are similar and the enthalpies of melting are increased sligh tly during the initial stages of exposure, suggesting that crystallini ty increased. (C) 1997 Elsevier Science Limited.