Affected by construction conditions, equipment, technology and environment, polyurethane rigid foam will have various abnormal phenomena during the construction process, which will eventually cause product quality problems. Now analyze the various situations as follows:
1. The materials A and B do not foam after mixing: a.The material temperature is low; b.The distribution ratio of the two groups is not allowed; c.The catalyst is not added; d.The quality of the B material is poor;
2. Shrinkage of polyurethane rigid foam: a. A material has many components, which reduces the strength of polyurethane rigid foam and causes shrinkage; b. The mixture of material and liquid in the spray gun is uneven, the spray air is too small, or the viscosity of the material is too large; c. Too fast curing results in more formation Closed cell; d.The gas is deformed by thermal expansion and contraction.
3. Polyurethane rigid foam is brittle: a. Material B has too many components; b.Too much moisture; c.Working surface temperature is too low; d.Material B has a large acid value and contains many impurities; e. Too much flame retardant is added.
4. Polyurethane rigid foam is too soft and curing is too slow: a. The component amount of material B is small; b.The tin catalyst in material A is too small; c. The air temperature, material temperature, and blanking working surface temperature are low.
5. Polyurethane rigid foam collapses: a. The foaming gas is generated too fast, and the amine catalyst in the A material should be reduced
2. The foam stabilizer is invalid or alkaline; 3. The catalyst is invalid or missing, and the tin catalyst in material A should be added; 4. The acid value in the raw material is large.
6. The polyurethane rigid foam has large pores: a.The foam stabilizer is invalid or missing; b.There is a lot of water (water in the foaming agent or polyether); c.The mixing of materials A and B is uneven; The acid value is high; d. The gas generation speed is faster than that of the gel.
7. Rigid polyurethane foam cracks or burns: a.The temperature of the material is high; b.The catalyst is too much; c.The one-time pouring amount is too large, and the foam is too thick; d.The amount added when water is used as a foaming agent is too much; .
8. Polyurethane rigid foam falls off: a.The humidity of the sprayed working surface is high, which makes the reaction incomplete and the bottom foam becomes crisp, brittle, and powdery; b.The sprayed working surface is dirty, oily, and dusty
9. Fumes from rigid polyurethane foam: a.The dosage of catalyst is too high; b.The hydroxyl value of polyether is too high; c.The material temperature is too high.
From the above analysis of the reasons, it is known that in addition to objective factors, there are many factors involved in the components of material A. In actual production, the adjustment of viscosity, milking time, foaming time, curing time, etc. is mainly to adjust A material.
Polyurethane rigid foam is not only a mixture of materials A and B. It is necessary to understand the principle of forming polyurethane rigid foam and the interaction between each component, comprehensively analyze all factors, analyze them in a targeted manner, and judge the existence of problems from it, and it is not difficult to produce high-quality polyurethane foam. Polyurethane rigid foam products.
