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Abstract
Random cases of exceptionally rapid aging of polyurethane (PUR) and extruded polystyrene (XPS) cellular plastics have been noted in the quality control and some long-term tests in Finland. As a consequence of the experiences, general interest in research in aging process of normal products and in developing and evaluating accelereated aging tests raised up. Rapid aging was anticipated to indicate a relatively high open porosity with the possibility of viscous flow of gas component due to total pressure gradient. As aging model and simulation method was then developed as a tool to support the experimental work. Requirements for the mdoel were capability to handle transient temperature field; simultaneous gas transfer by diffusion and viscous flows as well as possible phase changes and solution of different cases into the matrix of the material. It is also desired that if the heterogenity of the material is known, it could be taken in account as well as influcences of compact impermeable facings (skins, Al-folios etc.). The main differences of the present model and those given in the literature is that viscous flow, transient temperature field and interstitial phase changes are considered. The validation of the model - specially the experimental investigation giving the information of viscous flow of gases compund - is until now limited. The preliminary results of aging under significant total pressure gradient are, howerver, indicating existence of viscous flow. Furhter work is still needed in this field.
Random cases of exceptionally rapid aging of polyurethane (PUR) and extruded polystyrene (XPS) cellular plastics have been noted in the quality control and some long-term tests in Finland. As a consequence of the experiences, general interest in research in aging process of normal products and in developing and evaluating accelereated aging tests raised up. Rapid aging was anticipated to indicate a relatively high open porosity with the possibility of viscous flow of gas component due to total pressure gradient. As aging model and simulation method was then developed as a tool to support the experimental work. Requirements for the mdoel were capability to handle transient temperature field; simultaneous gas transfer by diffusion and viscous flows as well as possible phase changes and solution of different cases into the matrix of the material. It is also desired that if the heterogenity of the material is known, it could be taken in account as well as influcences of compact impermeable facings (skins, Al-folios etc.). The main differences of the present model and those given in the literature is that viscous flow, transient temperature field and interstitial phase changes are considered. The validation of the model - specially the experimental investigation giving the information of viscous flow of gases compund - is until now limited. The preliminary results of aging under significant total pressure gradient are, howerver, indicating existence of viscous flow. Furhter work is still needed in this field.
Date
9/1989
9/1989
Author(s)
R Kohonen; T Kiminki; E Kokko
R Kohonen; T Kiminki; E Kokko
Page(s)
20
20
Keyword(s)
polyurethane; extruded polystyrene; cellular plastic
polyurethane; extruded polystyrene; cellular plastic