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Abstract
CFC blown cellular plastics including polyurethanes, polyiso- cyanurates, polystyrene and phenolics are widely used for insulating buildings and industrial systems because of their potentially high thermal resistance per unit thickness. Heat is transferred through closed-cell foam insualtion by conduction through the solid polymer making up the cell structure (accounting for apporx 25% of the toal heat transfer), by convection throught tyhe gas within the cells (approx 50%) and by radiation (approx 25%). The conductive (through the polymer matrix) and radiative heat transfer properties of foams are reasonably stable; the increase of foam "conductivity" with age occurs due to change in the energy transfer proerties of the intercellular gas (compoisiton and pressure). After manufacture, the cells contain close to 100% blowing agent and 0% air; a vapor difussion process that involves air ingress and blowing agent egress begins (changing the cell gas compositon) and this effect is known as the aging effect.
CFC blown cellular plastics including polyurethanes, polyiso- cyanurates, polystyrene and phenolics are widely used for insulating buildings and industrial systems because of their potentially high thermal resistance per unit thickness. Heat is transferred through closed-cell foam insualtion by conduction through the solid polymer making up the cell structure (accounting for apporx 25% of the toal heat transfer), by convection throught tyhe gas within the cells (approx 50%) and by radiation (approx 25%). The conductive (through the polymer matrix) and radiative heat transfer properties of foams are reasonably stable; the increase of foam "conductivity" with age occurs due to change in the energy transfer proerties of the intercellular gas (compoisiton and pressure). After manufacture, the cells contain close to 100% blowing agent and 0% air; a vapor difussion process that involves air ingress and blowing agent egress begins (changing the cell gas compositon) and this effect is known as the aging effect.
Date
9/1989
9/1989
Author(s)
R J Booth; M P Drouin.
R J Booth; M P Drouin.
Page(s)
14
14
Keyword(s)
R-value; foam insulation; CFC; polyurethane; polyisocyanurate; polystyrene; phenolic; thermal resistance; aging effect
R-value; foam insulation; CFC; polyurethane; polyisocyanurate; polystyrene; phenolic; thermal resistance; aging effect