polyurethane foam shrinkage?
affected by the construction conditions, equipment, technology and environment, polyurethane rigid foam in the construction process will appear a variety of abnormal phenomena, ultimately resulting in product quality problems. various situations are analyzed as follows:
1, a, b material mixing does not foam: ① material temperature is low; ② two groups are not allowed to allocate the ratio ③ leakage of catalyst; ④ b material quality is poor; ⑤ leakage of foaming agent.
2, polyurethane hard foam contraction: ① a material components, so that the polyurethane hard foam contraction caused by the decline in strength; 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 a large number of closed-cell; ④ thermal expansion and contraction of the gas deformation.
3, polyurethane hard foam crisp: ① b material components too much; ② too much water; ③ work surface temperature is too low; ④ b material acid value, containing impurities; ⑤ flame retardant add too much.
4, polyurethane rigid foam is too soft, too 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 hard foam collapse: ① foaming gas generated too quickly, should reduce the amount of amine catalyst in the a material; ② homogenization of the work surface temperature is low.
dosage; ② leveling agent failure or alkaline; ③ catalyst failure or omission, should be added to the a material in the tin catalyst; ④ raw materials in the acid value is large.
6, polyurethane rigid bubble hole coarse: ① leveling agent failure or leakage; ② water (blowing agent or water in the polyether); ③ a, b material mixing and mixing is not homogeneous; ④ b material purity is low, containing total chlorine or acid value is high; ⑤ gas generation speed faster than the gel.
7, polyurethane rigid foam cracking, or heartburn: ① high temperature of the material; ② catalyst overdose; ③ a pouring amount is too large, the foam is too thick; ④ water as a blowing agent to add too much; 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, powdery foam; ② sprayed work surface is not clean, there is oil, too much dust
9, polyurethane hard foam smoke: ① catalyst dosage is too high; ② polyether hydroxyl value is too high; ③ material temperature is too high.
from the above analysis of the reasons, in addition to objective factors, a material components involved in more factors. in the actual production, adjust the viscosity, emulsion time, foaming time, curing time and so on is mainly to adjust the a material.
polyurethane rigid foam is not just a mixture of a and b materials, to understand the principle of generating polyurethane rigid foam and the interaction between 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 rigid foam products.
