Abstract

This International Standard specifies a general procedure for the determination of the volume percentage of open and of closed cells of rigid cellular plastics, by measurement first of the geometrical volume and then of the air-impenetrable volume of test specimens. The procedure includes the correction of the apparent open-cell volume by taking into account the surface cells opened by cutting during specimen preparation. Two alternative methods (method 1 and method 2), and corresponding apparatus, are specified for the measurement of the impenetrable volume. The results obtained from method 2 are intended to be used for comparison purposes only.

Principle

The surface area S and geometrical volume Vg of a number of test specimens, each having a different geometrical surface/volume ratio r, is determined.

The impenetrable volume Vi is determined by either of two methods, namely:

a) method 1 — by pressure variation (pyknometer);

b) method 2 — by volume expansion.

The determination of the impenetrable volume Vi is based on the application of the Boyle-Mariotte law to a gas confined in an indeformable chamber, first in the absence and then in the presence of a test specimen.

The apparent volume percentage of open cells ωr, of the test specimen is calculated by plotting the curve ωr = f (r) and extrapolating to r = 0, followed by calculation of the corrected volume percentage of open cells ω0 and the corrected volume percentage of closed cells ψ0.

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