Polyols oxyethylene group content

The principal focus of this paper will be on the effects of polyol molecular weight, polyol oxyethylene group content,... 

Increased oxyethylene group content in the polyol results in improved stability as reflected in better retention of tensile strength with thermal exposure. In turn, this coincides with better retention of the weight average molecular weight of the polymers as determined by GPC measurements. 

There is strong evidence that thermal stability is dependent primarily on oxyethylene group content rather than primary hydroxyl content. Table 3 shows that polymer prepared from a 2000 molecular weight polyol with 45% by weight oxyethylene group content but only 46% primary hydroxyl content is more stable than one prepared from a polyol with 30% by weight oxyethylene groups but with 82% primary hydroxyl. 

The effects of polyol molecular weight and oxyethylene group content on the thermal stability of these polymers have been reported independently by Bonk and Shah ( 7) ... 

Effect of Oxyethylene Content on Stability. The processing instability of TPU elastomers based on PPG 2000 can be overcome by the use of ethylene oxide "tipped" PPG polyols, especially those containing high levels of oxyethylene groups, e.g., 30% to 45% by weight. The improved stability of the polymers based on such polyols is demonstrated in Table 2. 

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