Resistance to immersion in boiling water

 

 

Principle
The effect of immersion in boiling water for 2 h is determined by the increase in mass and thickness of test specimens and by noting any change in appearance.
The test is generally in accordance with EN ISO 62, except for a longer period of immersion in the boiling water and the requirement for thickness measurements.

Apparatus
1. Balance, accurate to 1 mg.
2. Conditioning chamber, in accordance with EN ISO 291, with a standard atmosphere of (23 ± 2) °C and relative humidity (50 ± 5) %.
3. Vessel, containing boiling distilled water.
4. Vessel, containing distilled water at (23 ± 2) °C.
5. Micrometer thickness gauge, as described in 5.2. If curvature of the specimen prevents accurate thickness measurement, then a suitable ball-ended micrometer thickness gauge shall be used.
6. Suitable heating apparatus, (for example an electric hotplate).
7. Specimen holder, to hold specimens vertically during immersion and prevent contact with other specimens or the vessel.

Test specimens
Three specimens shall be taken from the same laminate, cut from positions greater than 50 mm from the edge of the sheet. Each specimen shall be (50 ± 1) mm square, and of the thickness of the laminate under test; and cut in such a way that no appreciable heat is generated and the edges are free from cracks. Cut edges shall be smooth.

Procedure
Place the three specimens for at least 72 h in the conditioning chamber.Weigh each specimen to the nearest 1 mg (mass m1).
Measure the thickness of each specimen as specified in Clause 5, but at the middle of each of the four cut edges (t1, t2, t3, t4) and with the external edge of the micrometer anvil positioned approximately 5 mm from each edge. Mark the measuring points so that subsequent measurements can be made in the same places.
Place the specimens in the vessel of boiling distilled water. Take care to prevent the specimens from making contact over any substantial area with one another or with the vessel.
After (120 ± 5) min, remove the specimens from the boiling water and allow to cool for (15 ± 5) min in the vessel of distilled water maintained at (23 ± 2) °C.
Take them from the water and remove all surface water with a clean dry cloth or with filter paper. Weigh the specimens again to the nearest 1 mg (mass m2) within 1 min of taking them from the water.
Determine the thickness of each specimen to the nearest 0,01 mm at the same points as before (t5, t6, t7, t8).
Examine each specimen visually for change in appearance.

Expression of results
The boiling water absorbed by each specimen is given, as a percentage by mass
The percentage increase in thickness at the measuring points of each specimen
The result of the examination for change in appearance shall be the lowest rating of the three specimens assessed in accordance with the following rating scale:
Rating 5: No visible change.
Rating 4: Slight change of gloss and/or colour, only visible at certain viewing angles.
Rating 3: Moderate change of gloss and/or colour.
Rating 2: Marked change of gloss and/or colour.
Rating 1: Blistering and/or delamination.