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The technical viability of alternative blowing agents in polyisocyanurate roof insulation Part 2: Acceleration of thermal resistance aging using thin boards

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Abstract
This paper reports thermal conductivity (k) values on a set of industry produced, prototypical, experimental polyisocyanurate lamined boardstock foams blown with five gases. The k-values were determined from 30-120F using the ORNL Unguarded Thin-Heater Apparatus and the ORNL Advanced R-Matic Apparatus. The test results on panels with facers provide an independent laboratory check on the increase in k observed for a 241-day field exposure in the ORNL Roof Thermal Research Apparatus. The observed laboratory increase in k, was between 8% and 11%. Results are reported on a thin-specimen, accelerated aging procedure to establish the long-term thermal resistance of gas-filled cellular foams. These thin specimens were planed from the industry-produced boardstock foams and aged at 75F for 150F for up to 190 days. The resulting k-values were correlated with an exponential dependency on (diffusuion coefficient x time) 1/2/thickness and provided diffusion coefficient for air components into the foam and blowing agent out of the foam. This accelerated aging procedure is a promising technique and was used to predict the five-year thermal resistivity of the foams. Agingg at 75 and 150F showed the foams performance within 3 to 16% (average 9.4%) of that obtained by CFC-11 under similar conditions.
Date
10/1990
Author(s)
D L McElroy; R S Graves; F J Weaver; D W Yarbrough
Page(s)
239-246
Keyword(s)
CFC-11; blowing agent; polyisocyanurate insulation; thin boards; thermal resistance; k-value


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