At day 7 and 14, the specimens shall be removed from the respective test chambers and then stored for a minimum of 2 hours at standard conditions in accordance with EN 13238. At the four corners, the distance between the boards is measured as near as possible to the interior foam surface (distance “c” in Figure B.2). Alternatively, if there are any surface irregularities, the distance can be measured at the exact middle of the specimen where the two spacers were placed (Figures B.3). After the first measurement, place the specimens back in the proper chamber.
Dimensional stability calculation
The dimensional stability, d, is calculated as the percentage change in the assembly dimensions:
b (mm) = Measured width of the gap after storage in the test chamber
c (mm) = Starting value before storage
The dimensional stability d of one specimen is given by the mean value of the four or two measuring points. The mean value of each assembly and the mean value of all assemblies as well as the standard deviation are recorded.
The overall mean value together with its standard deviation shall be reported.
*Locations for determination of thickness after exposure
Figure B.1 – Specimens for determination of dimensional stability – side view