Analysis of the problems of polyurethane hard foam in the construction process

Due to the influence of construction conditions, equipment, technology and environment, various abnormal phenomena will occur in the construction process of polyurethane hard foam, which will eventually cause quality problems of products. The analysis of various situations is as follows:

1. Shrinkage of polyurethane hard foam: (1) multiple components of material A make the strength of polyurethane hard foam decrease and cause shrinkage; (2) spray gun in the mixture of material and liquid, spray air is too small, or the material viscosity is too big; (3) curing too fast, the formation of more obturator; (4) gas expansion cold contraction deformation.

2, A, B mixture after foaming: (1) material temperature is low; (2) the ratio of two components is not allowed to leakage of catalyst; (B) poor quality of materials; 5. Missing foaming agent.

3. Brittle polyurethane hard foam: (a) too many components of B material; (2) too much water; (3) the working face temperature is too low; (4) B acid value is large, containing many impurities; (5) added too much flame retardant.

4. Polyurethane rigid foam is too soft and too slow to mature. (2) A material tin catalyst is too few; (3) temperature, material temperature, blanking working face temperature is low.

5, polyurethane hard foam collapse bubble: (1) foaming gas generation too fast, should reduce the amine catalyst in A

The dosage; (2) foaming agent failure or alkaline; (3) catalyst failure or missing add, add A tin catalyst in the material; The acid value of the raw material is high.

6, polyurethane hard bubble hole thick: (1) foam homogenizer failure or missing add; (2) water (foaming agent or polyether water); A, B material mixing is not uniform; (4) B material purity is low, containing high total chlorine or acid value; (5) gases occur faster than gels.

7, polyurethane hard foam cracking, or heartburn: (1) high material temperature; (2) excessive catalyst; (3) a pouring quantity is too large, too thick foam; (4) do too much water foaming agent add amount; (5) content

There are metal salt impurities in the material.

8, polyurethane hard foam smoke escape: (1) catalyst dosage is too high; (2) high hydroxyl value of polyether; The material temperature is too high.

From the above analysis, it can be concluded that in addition to objective factors, there are many factors involved in the component of A. In the actual production, the adjustment of viscosity, milk white time, foaming time, curing time, etc. is mainly to adjust the A material.

Polyurethane rigid foam is not only A mixture of materials A and B. It is not difficult to produce excellent polyurethane rigid foam products after understanding the principle of forming polyurethane rigid foam and the interaction among various components, taking all factors into consideration, making targeted analysis and judging the existing problems

9, polyurethane hard foam off: (1) spraying work face humidity, so that the response is not fully enough, the bottom foam crisp, brittle, powdery; (2) is sprayed working face unclean, greasy, dust too much.