Abstract
For several years, the polyurethane industry has critically examined its products in order to meet present and possible future European environmental regulations. Particularly in the construction industry, research has moved in two directions, namely CFC replacement and halogen-free, fire retardant foam.
It is clear that the formulations have had to be adapted to the new types of blowing agents and the halogen-free additives in order to be able to compare favourably with the thermal and fire performance previously achieved. These changes have resulted in a need to understand the fundamental factors which determine the long term dimensional stability of foams, if one is to underwrite their long term performance.
From the theoretical understanding, it is then possible to assess the validity of current test methods and to design improved tests for the prediction of the long term dimensional stability of the new systems.
In this paper, the relevant fundamental factors have been examined individually. Factors which predominantly effect the polymer strength, processing, diffusion of gases and plasticisation have been grouped together and the combined effect under different conditions and in different applications within the construction area are discussed. Finally the prediction of long term behaviour via modelling is highlighted.
It was shown that the effect of the combined action of all parameters influencing the long term dimensional stability of foams has changed in new systems based on benign blowing agents, compared to conventional CFC 11 blown foams.
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