Abstract
Accelerated ageing tests have been the industry standard for many years. With the introduction of CFC alternatives these accelerated ageing tests have become questionable. This paper describes how the ageing of foams, based on novel blowing agents, can be predicted. The comparison of an ‘experimental data set’ with a ‘calculated data set’ shows the accuracy and reliability of the method presented in this paper.
The calculated data set is generated via the determination of fundamental foam physical properties and an ageing calculation model. The two most important factors are the effective diffusion constant and the initial cell gas composition. The influence of temperature on both the effective diffusion constants and gas content is determined. Finally the foam structure is described in terms of cell size, polymer distribution over struts and windows and foam void volume.
The experimental data is based on the actual K-values measured on foam samples after exposure to a number of different ageing conditions. Parameters that were investigated are foam dimensions and exposure temperature. A comparison between model prediction and data obtained from long term field exposures is made.
The method presented allows for a K-value ageing prediction under well defined conditions without the need for extended exposure experiments.
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