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Reducing internal stress is very important for the durable bonding of epoxy resin adhesive. The way is to minimize the occurrence of internal stress and to relax the produced internal stress as soon as possible.
1. epoxy resin and long chain curing agent with low modulus of elasticity, small shrinkage and small coefficient of thermal expansion are selected.
2. increase the toughness of epoxy adhesive and form the ductile interface layer, so that the internal stress is easy to relax.
3. strictly control the amount of amine curing agent of epoxy resin, if the large amount of highly cross-linked, elastic shrinkage, easy to produce great stress.
4. addition of inert or inorganic filler reduces the shrinkage rate, but is affected by the type and dosage of two silicon. Calcium carbonate can reduce internal stress.
5. the film is thinner as far as possible so that the volume of the volume is small and the defect is small.
6. solvent epoxy adhesive should be fully coated with solvents and moisture. It can avoid solvent residue and reduce volume shrinkage during solidification, thus reducing internal stress.
7. reduce the heating and cooling rate of the curing process, and keep the uniform temperature field as far as possible.
8. curing speed should not be too fast, because the faster the curing, the more the internal stress accumulates.
9. after curing after curing, the stress relaxation can be made.
10. heating, it can not be cooled sharply, and the relaxation time of internal stress is given.
11. decrease of epoxy resin adhesive adhesive by difference of thermal expansion coefficient.
12. increasing the thermal conductivity of epoxy adhesive can reduce the shrinkage stress caused by different thermal expansion coefficient.
13. as far as possible, the modulus of elasticity and the vitrification temperature can be reduced as much as possible.