Thermosetting Resins Troubleshooting

The most important properties of a hot mounting compound are; Hardness, Shrinkage and Viscosity. The Hardness of the compound should match the hardness of the specimen in order to avoid uneven abrasion during grinding. If the shrinkage during curing is large, a gap between the specimen and the mount will occur and the edge will not be adequately protected. Viscosity should allow the compound to contact all areas of the sample.

Problem Cause Solution
mounting mould radial cracking Radial Cracking Too large sample section. Increase mould diameter or reduce specimen size. The distance between the specimen and the cylinder wall must be a minimum of 3 mm to avoid cracks in the resin.
Sample corners too sharp. Decrease samples size. Round sample corners.
mounting edge shrinkage Edge Shrinkage Incorrect resin choice. Try with a lower linear shrinkage value.
Dirty sample surfaces. Clean and dry samples thoroughly.
Mount not fully cooled under pressure. Increase the cooling time.
grainy mould Mold appears grainy with insufficient compression. Curing temperature too low. Increase cure temperature.
Heat time too short. Increase heat time.
Insufficient mounting pressure. Increase mounting pressure.
bulging or soft mould Bulging or soft mould Insufficient process. Increase heat time.
Increase mounting pressure.
mounting circumferential cracks Circumferential Cracks Absorbed moisture. Store resin in a dry area.
Keep resin containers closed.
Dry resins at low temperatures.
mounting cotton ball effect Cotton ball Effect Excessive cooling rate Reduce the cooling rate by choosing "cooling by time"
Insufficient heating time Increase the heating time.