Polyurethane foam spray insulation and analysis of common problems

Polyurethane foaming process, foam shrinkage, crispy, too soft, heartburn, cracking, smoke and other problems, how to analyze what causes.

Polyurethane foaming process by the construction conditions, foaming equipment, construction technology and the impact of environmental temperature, there will be a variety of abnormal phenomena, zui ultimately affect the quality of the foam problem. How to solve the problem of shrinkage, crispness, softness, heartburn, cracking and smoke in the process of polyurethane foaming

The following A material represents polyurethane white material, i.e. combined polyether; B material represents polyurethane black material, i.e. polymerized MDI.

1. A, B material mixed not foam: ① low material temperature; ② two groups of ratio is not allowed ③ A material missed adding catalyst; ④ B material quality is poor; A material missed adding blowing agent.

2. polyurethane rigid foam contraction: ① A material components, so that the polyurethane rigid foam strength caused by contraction; ② uneven mixing of materials and liquids in the gun, spray air is too small, or the viscosity of the material is too large; ③ curing is too fast, the formation of more closed-cell; ④ thermal expansion and contraction of the gas deformation.

3. Polyurethane rigid foam crispy: ① B material components are too much; ② too much water; ③ work surface temperature is too low; ④ B material acid value, containing impurities; A material flame retardant to add too much.

4. Polyurethane hard foam is too soft, slow maturation: ① B material component amount is small; ② A material in the tin catalyst is too little; ③ air temperature, material temperature, low temperature of the working surface of the material.

5. Polyurethane rigid bubble collapse: ① foaming gas generated too quickly, should reduce the amount of amine catalyst in the A material; ② A material in the failure of the homogenizing agent alkaline; ③ catalyst failure or leakage, should be added to the A material in the tin catalyst; ④ raw materials in the acid value is large.

6. Polyurethane rigid bubble holes: ① A material in the failure of homogenizing agent or leakage; ② water (blowing agent or polyether in the water); ③ A, the material mixing mix is not uniform; ④ B material purity is low, containing total chlorine or acid value is high; ⑤ the gas generation rate is faster than the gel.

7. Polyurethane rigid foam cracking, or heartburn: ① high temperature of the material; ② A material catalyst is too much; ③ the amount of a pour is too large, the foam is too thick; do too much foaming agent to add; ⑤ metal salts impurities in the material.

8 polyurethane hard foam off: ① spraying work surface humidity, so that the reaction is not complete and sufficient, the bottom layer of foam crispy, brittle, powder foam ② sprayed work surface is not clean, there is oil, too much dust

9. polyurethane hard foam smoke: ① A material in the amount of catalyst is too high; ② A material in the polyether hydroxyl value is too high; ③ material temperature is too high.

From the above problem analysis, in addition to objective factors, A material components involved in more factors. In the real production, adjust the viscosity, emulsion time, foaming time, curing time, etc. is mainly to adjust the A material.

Polyurethane foaming process is not just A, B material mixing, to understand the principle of generating polyurethane foam and the role of the components, a combination of factors, targeted to analyze, from which to determine the existence of the problem, it is not difficult to produce high-quality polyurethane.