- Author
- Nguyen, T. | Byrd, W. E. | Zarr, R. R. | Stutzman, P. | Seiler, J.
- Title
- Effects of Environmental Exposures on the Properties of Polyisocyanurate Foam Insulation: Material Properties.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Book or Conf
- Society of the Plastics Industry of Canada. Long-Term Thermal Performance of Cellular Plastics. 2nd International Workshop. June 5-7, 1991, Ontario, Canada, 1-36 p., 1991
- Keywords
- polyisocyanurate foam | material properties | exposure | thermal conductivity | insulation | rigid foams | weight loss
- Abstract
- The effects of exposure environments on the material properties of unfaced polyisocyanurate insulation foams were investigated. Specimens were prepared from a commercial, faced, Refrigerant-11 blown board. Facers were removed and the board was sanded to a nominal thickness of 26.7 mm prior to the environmental exposure. Foams were exposed to the following environments: 1) ambient conditions of 22 deg C and 40% relative humidity (RH); 2) elevated temperature, 60 deg C; 3) cycling from 0 to 60 deg C over 24 hours, and 4) immersion in distilled water at 21 deg C for three months and then exposed to ambient conditions (22 deg C, 40% RH) for three months. Samples from the middle of the unexposed board and from the surface and middle of six-month exposed specimens were analyzed. Material properties were characterized by four analytical techniques, namely, scanning electron microscopy, fourier transform infrared-multiple internal reflection spectroscopy, differential scanning calorimetry, and thermogravimetry. In addition, the Young's modulus in compression was also measured. All four environments significantly decreased the compression modulus of the foams. All exposures caused considerable changes in the chemical, physical, and microstructural properties of polyisocyanurate foams. The effects were more severe for foams near the surface than those in the middle of the board. The material near the surface appears to be more friable than that in the middle. This difference, which relates to the formation of an excess of urea products, was more pronounced for foams exposed to water-containing environments. Thermal and FTIR analyses also showed different behaviors for weight loss, enthalpy change, and chemical variation among the environments. The microstructure, physical, and chemical properties of an unexposed polyisocyanurate foam are also presented.