Views:12 Author:Site Editor Publish Time: 2020-08-29 Origin:Site
During the polyurethane foaming process, the foam has shrinkage, crispness, too soft, heartburn, cracking, smoke and other problems. How to analyze the causes.
During the polyurethane foaming process, affected by the construction conditions, foaming equipment, construction technology and ambient temperature, various abnormal phenomena will occur, which will eventually affect bubble quality issues. How to solve the shrinkage, crispness, too soft, heartburn, cracking and smoke during the polyurethane foaming process?
The following material A represents polyurethane white material, that is, combined polyether; material B represents polyurethane black material, that is, polymeric MDI.
1. Material A and B do not foam after mixing: ①The temperature of the material is low; ②The distribution ratio of the two groups is inaccurate ③The catalyst of material A is missing; ④The quality of material B is poor; material A is missing a blowing agent.
⒉. Polyurethane rigid foam shrinkage: ① There are many components in the A material, which reduces the strength of the polyurethane rigid foam and causes shrinkage; ② The material and liquid in the spray gun are mixed unevenly, the spray air is too small, or the material.
The viscosity of the material is too large; ③ solidification is too fast, and more closed cells are formed; ④ the gas expands and shrinks and deforms.
3. Polyurethane hard foam is crispy: ①B material has too many components; ②Too much moisture; ③Working surface temperature is too low; ④B material has a large acid value and contains many impurities; A material flame retardant added amount excessive.
4. The rigid polyurethane foam is too soft and the maturation is too slow: ①The amount of material in the B material is small; ②The tin catalyst in the A material is too little; ③The air temperature, material temperature and blanking surface temperature are low.
5. Polyurethane rigid foam collapse: ①The foaming gas is generated too fast, and the amount of amine catalyst in material A should be reduced; ②The foam stabilizer in material A is invalid and alkaline; ③The catalyst is invalid, otherwise, the tin catalyst in material A should be added; ④The acid value in the raw material is large.
6. Thick polyurethane hard foam cells: ①The foam leveling agent in material A is invalid or missing; ②There is too much water (water in the foaming agent or polyether); ③A. The mixing of materials is uneven uniformity; ④B material has low purity, contains total chlorine or high acid value; ⑤The gas generation rate is faster than gel.
7. Rigid polyurethane foam is cracked or core burned: ①The material temperature is high; ②The catalyst of material A is too much; ③The amount of casting at one time is too large, and the foam is too thick; the amount added when making a blowing agent too much; ④There are metal salt impurities in the material.
8. The polyurethane hard foam falls off: ①The spraying working surface has high humidity, which makes the reaction insufficient, and the underlying foam is crisp, brittle, and powdery.②The sprayed working surface is unclean. oily, too much dust.
9. Fumes from rigid polyurethane foam: ①The amount of catalyst in material A is too high; ②The hydroxyl value of polyether in material A is too high; ③the temperature of material is too high, etc.
From the analysis of the above problems, it is known that in addition to objective factors, the A component involves many factors. In actual production, adjust the viscosity, milky time, and foam time, curing time, etc. are mainly to adjust A material.
In the polyurethane foaming process, it is not only the mixing of A and B materials. It is necessary to understand the principle of forming polyurethane rigid foam and the role of each component, integrate all factors, and be targeted.
After analyzing and judging that there are problems, it is not difficult to produce high-quality polyurethane.