Coefficient of Expansion Values for Modified Bitumen Roof Membranes

    Published: Jan 1987

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    A laboratory study was undertaken to determine the nature and the value of the coefficient of expansion for a wide variety of modified bitumen roof membranes. Tests were run from temperatures of 48.9°C (120°F) down to −40°C (−40°F) with observations being made at discrete temperature points. Regression analysis was used to establish a continuous curve for the coefficient of expansion values. This allowed for either tangent or secant coefficient of expansion values to be derived at any point (or between any two points for the secant coefficient) along the temperature range.

    These data are provided as basic information on the possible range of variation in the coefficient of expansion for these materials. The range of coefficients presented in this paper has been found to be an important factor in evaluating design and performance standards for roof membranes using these sheets.


    roofing, asphalt, atactic polypropylene, built-up roofs, coefficient of expansion, contraction, correlation coefficient, glass, modified bitumen, polyester, regression analysis, styrene-butadiene-styrene rubber

    Author Information:

    Dupuis, RM
    Principals, Structural Research, Inc., Middleton, WI

    Lee, JW
    Principals, Structural Research, Inc., Middleton, WI

    Committee/Subcommittee: D08.20

    DOI: 10.1520/STP25728S

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