Standard Test Method for Using Reflectance Spectra to Produce an Index of Temperature Rise in Polymeric Siding

Importancia y uso:

5.1 Heat buildup of polymeric building products due to absorption of energy from the sun may lead to distortion problems. Test Method Test Method D4803 was developed to predict a building product’s heat buildup (temperature rise). It compares the relative temperature changes of a pigmented PVC product and a PVC panel containing carbon black when exposed to an infrared heat lamp. Based on experimental results that determined the maximum temperature for this black panel under both solar exposure and in the laboratory test, a method for determining the exterior temperature rise and heat buildup for a test panel was developed. This test has shown to be useful and reliable but is time consuming and requires controlled conditions to minimize sources of variation.

5.2 This test method uses a spectrophotometer to measure a specimen’s reflectance in the ultraviolet, visible, and near infrared region and uses the spectral power distribution of the heat lamp specified in Test Method D4803 to determine an intensity factor, which is an index of the relative spectral energy absorption by the specimen.

5.2.1 The temperature rise that would occur under an Test Method D4803 test is proportional to this intensity factor. An equation has been derived from the correlation of the intensity factor and temperature rise data obtained from Test Method D4803 testing of samples with a wide range of color and lightness. A total of 99 samples were studied and represent samples with the lowest to highest temperature rise. Linear regression analysis yields a R2 correlation coefficient of 0.98.

5.2.2 The procedure in Appendix X1 allows prediction of temperature rise that would result from testing of the same sample under Test Method D4803.

5.2.3 As this procedure is a correlation to results obtained by Test Method D4803, it is a method that yields a relative temperature rise compared to black under certain defined severe conditions, but does not predict actual field application temperatures of the product. These product temperatures are influenced by incident angle of the sun, clouds, wind speed, insulation, installation behind glass, etc.

5.3 The intensity factor itself is a dimensionless index of the relative energy absorption of the specimen, without conversion to a temperature rise. It can be used to compare the heat buildup characteristics of different colors, or different candidate formulations for the same color. It can also be used to categorize color into ranges of intensity factor, to be used as a basis for testing of full siding products for resistance to thermal distortion.

Subcomité:

D20.24

Volúmen:

08.03

Número ICS:

83.140.99 (Other rubber and plastic products), 91.060.10 (Walls. Partitions. Facades)

Palabras clave:

heat build; intensity factor; polymeric siding; siding; spectral reflectance; temperature rise;