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SYNOPSISThe aging of high-density polyethylene (HDPE) when exposed to drastic climatic conditions (Canadian winter, characterized by low temperature and abrupt temperature variations between the night and the day) was studied. The importance of degradation was determined by evaluating the microstructural changes in HDPE (i.e., oxidations, ramifications, and polymeric chain breaking) by means of FTIR spectrophotometry. The crystallinity variation in HDPE by FTIR and DSC was also studied. Both techniques led to coherent results: there was a loss of crystallinity due to weathering degradation. This crystallinity reduction produced a drastic decrease in impact energy. However, the other properties evaluated were not significantly affected.

The properties of gels obtained from porcine blood plasma were studied under different pH conditions. Gels from liquid and spray-dried plasma were prepared and analyzed for water holding capacity (WHC), texture, and microstructure at pH 7.4, 6, 5.5 and 4.5. The denaturation extent of proteins was also determined by differential scanning calorimetry (DSC). All properties studied were dependent on pH. The WHC and consistency of gels decreased when pH decreased. These results correlated with microstructural changes observed by SEM. Spray drying affected the consistency of gels. The penetration force of the gel from dehydrated plasma was always lower than that prepared from liquid plasma where the pH was the same, but neither the WHC nor the microstructure of gels were affected.

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