SYMPOSIA PAPER Published: 01 January 1991
STP16350S

A Review of Techniques for Improved Foam Conductivity: Reducing Radiation Heat Transfer, Limiting Aging and Inclusion of Vacuum Elements

Source

To comply with international agreement closed cell polyurethane and polyisocyanerate foams must be made with blowing agents which minimize ozone depletion in the stratosphere. Candidate blowing agents have higher vapor conductivities resulting in lower R values for the foams. This paper reviews recent results of research at M.I.T. sponsored by the Department of Energy and the Environmental Protection Agency to find means to recover high R values. Use of small opaque particles or smaller foam cells reduces the radiative transfer in foams which is usually one third of the total heat transfer at standard conditions. The thermal aging of foams made with new blowing agents is a function of the permeability which has been measured for several new materials. The rate of aging can be reduced by proper use of diffusion barriers on the foam surface. The inclusion of vacuum elements in foam should increase the overall R value. A key problem is to find packaging materials for the vacuum elements which preserve the vacuum over the insulation life while not causing substantial secondary heat transfer around the circumference of the element.

Author Information

Glicksman, LR
Burke, M
Marge, A
Mozgowiec, M
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Details
Developed by Committee: C16
Pages: 237–259
DOI: 10.1520/STP16350S
ISBN-EB: 978-0-8031-5174-1
ISBN-13: 978-0-8031-1420-3