Long Term Thermal Resistance of Pentane Blown Polyisocyanurate Laminate Boards

Abstract

The accurate estimation of the thermal performance of insulation products over their expected lifetime has been a recognized challenge for over twenty years. This is because the lifetime of such products is long (10-25 years), thermal aging is caused by the diffusion of a multitude of gases, and the insulation product is not homogeneous. Two classical approaches to accelerating diffusion controlled phenomena, namely aging at higher temperature and aging a thin slice, have limitations when applied to insulation materials like polyisocyanurate (PIR) laminate board. Raising temperature does not change the diffusion coefficients of all the different gases involved in the aging process at the same rate. In the case of pentane blown PIR board, these gases are CO2, air and the different pentane isomers used to blow the foam. Thin slicing of core foam and scaling techniques, such as those in the ASTM C 1303 -00 procedure, do not account for the fact that PIR laminate boards are denser at the surface layer than in the core foam.

Structure, Mechanical, Thermal and Fire Behavior Assessments of Environmentally Friendly Crude Glycerol-Based Rigid Polyisocyanurate Foams

“…9 exceeds 90% (except 70CG). As a result, Fick's law should be more appropriate to describe the diffusion of gases during thermal aging of foam [53], according to the Eq. (9): where ϕ is the concentration; t is time and D is the diffusion coefficient.…”

“…According to Singh et al [53], value of the diffusion coefficient of cyclopentane in PIR rigid insulation boards is from 30 to even 100 times lower in comparison to air, thus also water vapor, depending on the manufacturer of foam. It can be assumed that D values for other physical blowing agents are in the same order of magnitude, which strongly indicates that the main factor affecting thermal conductivity coefficient over time is the amount of water vapor surrounding foam.…”

Closed Cell Foam Insulation: A Review of Long Term Thermal Performance Research

“…However, the diffusion phenomena for all gases are continuous over the entire time period, frustrating their efforts to use the slopes of the two regions to accurately measure diffusion rates. Diffusion rates can be more successfully measured using gravimetric and gas analysis equipment [Glicksman, Ostrogorsky and Chiapetta, 1984;Bhattacharjee et al, 1994;Singh, Ntiru, and Dedecker, 2003;Shankland, 1990].…”

“…An effective diffusion coefficient for each gas was separately obtained by cell gas analysis and used as input to the model. AgeSim then combined the validated methodology with empirical results to assign a "Calibrated skin factor" from elevated temperature aging data iterated through the model [Singh, Ntiru, and Dedecker 2002, Singh and Coleman 2007. Such 'tweaking' factors can be found in many models, and are useful so long as the adjustments are based upon a thorough understanding of the physical process.…”

Experimental and Numerical Examination of Naturally-Aged Foam-VIP Composites

“…The thermal conductivities were measured using a heat flow meter (HFM) according to ASTM C518 [20]. The simulations are intended to evaluate the impact of the thermal conductivities used as inputs to the 1D models on their ability to match the experimental results that are based on real material properties that are, in turn, influenced by both temperature variations and aging-related effects [10,21,22].…”