If the influence of construction conditions, equipment, technology, and environment is excluded, polyurethane rigid foam may encounter various situations during the construction process that fail to meet the requirements, which may ultimately lead to product quality problems. We will list various possible situations as follows:

1. A and B materials do not foam after mixing: ① low material temperature; ② Inaccurate allocation ratio between two groups ③ catalyst omission; ④ Leakage of foaming agent.

2. Polyurethane rigid foam shrinkage: ① Excessive proportion of material A leads to a decrease in the strength of polyurethane rigid foam and causes shrinkage; ② The mixture of material and liquid in the spray gun is uneven, the spray pressure is too low or the material viscosity is too high; ③ Curing too quickly, resulting in the formation of many closed pores; ④ Gas undergoes thermal expansion and contraction deformation.

3. Polyurethane rigid foam crispy: ① Excessive proportion of material B; ② There is too much water in it; ③ The working face temperature is too low; ④ B material has a high acid value and contains many impurities; ⑤ Excessive amount of flame retardant added.

4. Polyurethane rigid foam is too soft and matures too slowly: ① B component has a small amount; ② There are too few tin catalysts in material A; ③ The temperature, material temperature, and working face temperature of the material are low.

5. Polyurethane rigid foam collapse: ① If the foaming gas is generated too quickly, the amount of amine catalyst in material A should be reduced; ② The foaming agent is ineffective or alkaline; ③ If the catalyst fails or is missed, the tin catalyst in material A should be added; ④ The acid value in the raw materials is high.

6. Thick pores in polyurethane hard bubbles: ① Failure or omission of foaming agent; ② High moisture content (in foaming agents or polyethers); ③ A. B material mixing is uneven; ④ B material has low purity and high total chlorine or acid value; ⑤ Gas generation is faster than gel.

7. Cracking or burning of polyurethane rigid foam: ① High material temperature; ② Excessive catalyst; ③ The one-time pouring amount is too large, and the foam is too thick; ④ Adding too much water as a foaming agent; ⑤ There are metal salt impurities in the material.

8. The polyurethane rigid foam falls off: ① the spraying working surface has high humidity, which makes the reaction incomplete, and the bottom foam is crisp and powdery; ② The sprayed work surface is unclean, with oil stains and too much dust

9. Polyurethane rigid foam emits smoke: ① Too high catalyst dosage; ② High hydroxyl value of polyether; ③ The material temperature is too high.

From the above analysis of reasons, it can be concluded that besides objective factors, component A involves many other factors. In actual production, the adjustment of viscosity, milky white time, foaming time and curing time is mainly to adjust material A.

Polyurethane rigid foam is not just a mixture of materials A and B. It is necessary to understand the principles of generating polyurethane rigid foam and the interactions between its components. By comprehensively analyzing various factors and conducting targeted analysis, problems can be identified and high-quality polyurethane rigid foam products can be produced.