Air-Flow Oven

Air-Flow Oven One more approach employed at the company was to study oxidative deterioration of GeoDeck boards in airflow oven. Preliminary experiments have shown that GeoDeck boards can stay in a vacuum oven indehnitely long even at high temperatures, above 230°F. At higher temperatures the board becomes deformed because the temperatures are too close to the melting point of HDPE. 

The experiment aimed at a comparison of GeoDeck boards made with no added antioxidants ( zero level ), first level boards (made for several days only in October 2003), second level boards (made between December 2003 and December 2004), and third level boards (made after December 2004). The results are listed in Tables 15.8, 15.9, and 15.10. 

These tables show the obvious trend-the higher the density, the higher the durability. Clearly, in the presence of a relatively small amount of an antioxidant ( first level ) the durability of the boards is significantly higher compared with that in Table 15.8. It is worth mentioning that in the presence of the antioxidant, boards with density below 1.125 g/cm could not be produced (compare with Table 15.8). Apparently, the antioxidant slowed down the decomposition of HDPE in the extruder hence, effectively decreased the amount of VOC and, as the result, decreased the porosity of the extruded deck board and increased its density. 

It is remarkable that at a noticeably higher temperature and a much longer heating time, boards with a relatively high density (1.20 g/cm ) showed practically no degradation, whereas at much lower temperature deck board with low density (1.02-1.09 g/cm ) but without added antioxidant lost 50% and more of their strength. 

Experiments with third level GeoDeck boards (made in or after December 2004) could not detect any reduction in flex/shear strength at conditions given in Table 15.10. Residual load at failure was in the range of 99 + 2%, and could not be reliably measured. 

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