Polyurethane foam shrinkage?
Affected by construction conditions, equipment, technology and environment, polyurethane hard foam will appear various abnormal phenomena during the construction process, which will eventually cause product quality problems. Now the various situations are analyzed as follows:
1、No foaming after mixing A and B materials: ①Low material temperature; ②Inadmissible ratio of two groups; ③Leakage of adding catalyst; ④Low quality of B materials; ⑤Leakage of adding foaming agent.
2, polyurethane rigid foam shrinkage: ① A material components, polyurethane rigid foam strength decline caused by shrinkage; ② uneven mixing of material and liquid in the gun, the spray air is too small, or the viscosity of the material is too large; ③ curing too fast, the formation of more closed pores; ④ gas heat expansion and cold shrinkage deformation.
3, polyurethane hard foam crisp: ① B material components are too much; ② moisture too much; ③ working surface temperature is too low; ④ B material acid value is large, containing more impurities; ⑤ flame retardant added too much.
4、Polyurethane hard foam is too soft and slow to mature: ①B material component is small; ②Tin catalyst in A material is too little; ③Temperature, material temperature and working surface temperature of falling material is low.
5, polyurethane hard foam collapse bubble: ① foaming gas generation too fast, should reduce the A material in the amine catalyst
②The leveling agent fails or has alkali; ③The catalyst fails or misses to add, should add the tin catalyst in A material; ④The acid value in raw material is large.
6, polyurethane rigid bubble pore: ① foam leveling agent failure or leakage; ② moisture (foaming agent or polyether moisture); ③ A, B material mixing mix is not uniform; ④ B material purity is low, containing total chlorine or high acid value; ⑤ gas generation speed faster than the gel.
7, polyurethane hard foam cracking, or heartburn: ① high material temperature; ② excessive catalyst; ③ a pouring volume is too large, the foam is too thick; ④ too much water for foaming agent added; ⑤ metal salt impurities in the material.
8, polyurethane hard foam off: ① spraying work surface humidity, so that the reaction is not fully adequate, the bottom foam crispy, brittle, powder froth; ② sprayed work surface unclean, oil, too much dust
9, polyurethane hard foam escape smoke: ① catalyst dosage is too high; ② polyether hydroxyl value is too high; ③ material temperature is too high.
From the analysis of the above reasons, in addition to objective factors, the A material component involves more factors. In actual production, adjust the viscosity, emulsion time, foaming time, curing time, etc. is mainly to adjust the A material.
Polyurethane rigid foam is not only the mixture of A and B materials, to understand the principle of generating polyurethane rigid foam and the interaction between the components, comprehensive factors, targeted analysis, from which to determine the existence of problems, it is not difficult to produce high-quality polyurethane rigid foam products.
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