1. Foam shedding.
In winter or rainy days, because the temperature of the sprayed surface (the body skeleton and the inner surface of the outer skin, etc.) is too low, or the humidity in the air is too high, there is moisture on the workpiece surface, so that the adhesion between the foam bottom layer and the workpiece decreases, and it is easy to fall off quickly.
In addition, when the coated surface, skeleton has oil, dust, or ingredients imbalance (A material is too much), it will also reduce the adhesion of the foam layer.
The solving measures are as follows: before spraying foaming, do a good job of the surface treatment of the skeleton and skin, construct on a rainy day with high humidity, try to dry the moisture on the surface of the sprayed workpiece, heat the raw materials in winter, and preheat the coated surface and skeleton if possible; if necessary, increase the proportion of component B (or reduce the proportion of component A) to speed up the reaction and improve adhesion.
2. Foam shrinkage.
Foam shrinkage refers to the phenomenon that the foam body shrinks around the foam body after forming, so that there is a large gap between the foam body and the body skeleton, which affects the bonding strength and sealing, and is easy to fall off.
The reason is that during the construction in winter, the viscosity of the material increases, the fluidity becomes worse, and the foam produces volume shrinkage in the forming process.
The solution is to heat the raw material and air, and appropriately increase the air flow rate (speed) to make the material mix evenly and speed up the reaction speed.
3. Dead bubble.
Dead bubbles mean that the foam formed is too dense or does not foamy.
This is due to the lack of foaming agent in the raw materials, or the temperature is too low.
The solution is to heat the raw materials, increase the air volume, adjust the formula, increase the dosage of catalyst and foaming, so as to shorten the reaction time.
If there are dead bubbles in the construction at normal temperature, it may be due to the fact that material A has been stored for too long and the foaming agent has evaporated, so part of the foaming agent should be added to material A.
4. The foam is too brittle.
This is mainly due to the improper proportion of raw materials and the excessive use of materials for component B.
The solution is to reduce the flow rate of material B appropriately in order to reduce the amount of isocyanate.
5. The foam is too soft.
Contrary to the brittleness of foam, this is mainly related to the low material ratio of component B, so appropriately increase the amount of component B (or reduce the material of component A).
