Common problems and solutions in the production of

2022-08-09
  • Detail

Common problems and solutions in the production of polyurethane flexible foam

the accidents and problems encountered in the actual foaming production are diverse, and the production of each accident is caused by many factors. In the analysis of accidents caused by complex factors, it is generally difficult to list all influencing factors and the main factors that really work. The following summarizes some frequently encountered accidents and their causes

1. Focus (the temperature of the reaction center exceeds the oxidation resistance temperature of the raw material)

(1) there are problems in the quality of polyether polyols: the water content in the products exceeds the standard during production, storage and transportation, the content of peroxides and low boiling point impurities is too high, the concentration of metal ions is too high, and the type and concentration of antioxidants are inappropriate

(2) formula: in the low-density formula, the TDI index is too high, the proportion of water in foaming agent to physical foaming agent is improper, the physical foaming dose is too small, and the water is too much

(3) climate impact: high temperature in summer, slow heat dissipation, high material temperature, high air humidity, and the temperature of the reaction center exceeds the oxidation resistance temperature

(4) improper storage: when the TDI index increases, the accumulated heat energy during post ripening increases, causing the internal temperature to rise and anxiety

2, large compression deformation

(1) polyether polyol: the functionality is less than 2.5, the proportion of ethylene oxide is large, if it is required to be less than 8%, there are many small molecular components, and the unsaturation is greater than 0.05mol/kg

(2) process conditions: the temperature of the reaction center is too low or too high, the post ripening is not good, the reaction is not complete or there is partial anxiety

(3) process formula: TDI index is too low, stannous octoate in silicone oil is excessive, foam ventilation is low, and pore closure rate is high

3. Foam is too soft (hardness decreases at the same density)

(1) polyether polyols: low functionality, low hydroxyl value, and high relative molecular weight

(2) process formula: less stannous octanoate, slow gel reaction speed, less water, more physical foaming agents, high silicone activity, large dosage, low TDI index under the same amount of tin

4. Large bubbles

(1) poor mixing; Uneven mixing, short milky period

(2) process formula: the amount of silicone oil is lower than the lower limit, the amount of stannous octanoate is small and the activity is poor, and the gel speed is slow

5, higher than the set density

(1) polyether polyols: low activity, high relative molecular weight

(2) process formula: the amount of silicone oil is lower than the lower limit, the TDI index is low, and the foaming index is low

(3) climatic conditions: low temperature and high pressure

6. Collapse holes (gas generation speed is greater than gel speed)

(1) polyether polyols: acid value seriously exceeds the standard, there are many impurities, and the activity is low. The measured force relative to the component cannot be decomposed into two components that produce tear initiation and tear expansion, with a large amount

(2) process formula: the amount of amine is more, the amount of tin is less, and the TDI index is low. At the same amount of tin, the TDI index is too high, the gas generation speed is greater than the gel speed, and the skeleton strength is small and bubbles collapse or local holes appear

source:

this article is from the Internet, and the copyright belongs to the original author. It is only for everyone to share and learn. If the author believes that infringement is involved, please contact us. The automotive industry has higher requirements for the functionality and quality of the automotive surface than any industry. We will delete it immediately after verification

Copyright © 2011 JIN SHI