Common problems and solutions in flexible foam production Common problems and solutions in flexible foam production

Common problems and solutions in flexible foam production Common problems and solutions in flexible foam production
The amount of accidents and problems encountered in actual foam production is varied, and each accident is caused by a variety of factors. When analyzing accidents caused by complex factors, it is generally difficult to list all the influencing factors and the main factors that really play a role.
I. The following summarizes some frequently encountered accidents and their causes:

1. Coke center (reaction center temperature exceeds raw material antioxidant temperature)
(1) Polyether polyol quality problems: production, storage and transportation process to make the product moisture exceeds the standard, peroxide, low boiling point impurity content is too high, metal ions concentration is too high, with the use of antioxidant type and concentration of improper;
(2) Formulation: low-density formula, too high TDI indicator, improper proportion of water and physical blowing agent in the blowing agent, low dosage of physical blowing agent and too much water;

(3) Climatic influence: high temperature in summer, slow heat dissipation, high material temperature, high air humidity, reaction center temperature exceeding antioxidant temperature;
(4) Improper storage: when the TDI index rises, the thermal energy of the fluff increases in the post-cooking process, resulting in the internal temperature rises and scorching.
2、Compression deformation
(1) Polyether polyol: the functional degree is less than 2.5, the proportion of ethylene oxide is more than 8%, the small molecule component is more, the degree of unsaturation is more than 0.05mol picture;
(2) Process conditions: the reaction center temperature is too low or too high, poorly cooked, not fully reacted or part of the focus;
(3) Process formula: TDI indicator is too low, too much silicone oil stannous octanoate, low foam aeration, high closed cell rate.
3、Foam is too soft (decrease in hardness at the same density)
(1) Polyether polyol: low functionality, low hydroxyl value, large relative molecular mass;
(2) Process formulation: low dosage of stannous octanoate, slow gel reaction speed, less water under the same amount of tin, more physical foaming agent, high dosage of silicone oil activity, low TDI index.

4, bubble hole coarse
(1) Poor mixing; uneven mixing, short emulsification cycle;
(2) Process formulation: silicone oil dosage is lower than the lower limit, low dosage of stannous octoate and poor activity, slow gelation.
5, higher than the set density
(1) Polyether polyol: low activity, large relative molecular mass;
(2) Process formulation: silicone oil dosage is lower than the lower limit, low TDI index, low foaming index;
(3) Climatic conditions: low temperature, high air pressure.
6, collapse of the bubble hole (gas velocity is greater than the gel velocity)
(1) Polyether polyol: acid value seriously exceeds the limit, more impurities, low activity, large relative molecular weight;
(2) Process formula: more amine dosage and less tin dosage, low TDI index, too high TDI index under the same tin dosage, gas velocity is greater than the gel speed, the skeleton strength is small and there is a collapsed bubble or localized holes.
Two
1、High rate of closed hole
(1) polyether polyol: high proportion of ethylene oxide, high activity, more displacement of different active polyether polyol;.
(2) Process formulation: more stannous octanoate, high isocyanate activity, high cross-linking degree, fast cross-linking speed, too much amine and physical blowing agent causing low pressure inside the foam, foam elasticity can’t open the holes, TDI index is too large will also lead to high rate of occlusion.
2、Shrinkage (gel speed is greater than foaming speed)
(1) Excessive closed cell ratio: shrinkage during cooling;
(2) Process conditions: low air temperature, low material temperature;
(3) Process formula: too much silicone oil, too much physical foaming agent, too low TDI index.

3、Internal cracks
(1) Process conditions: low air temperature, high reaction center temperature;
(2) Process formulation: low TDI index, too much tin, high early foaming strength;
(3) High silicone oil activity: low dosage.
4, top crack (hair gas gel speed imbalance)
(1) Process conditions: low temperature, low material temperature;
(2) Process formula: insufficient amount of catalyst, low amount of amine, poor quality of silicone oil.
5, bottom corner cracks (too much amine, foaming too fast)
Large holes on the surface: excessive amount of physical foaming agent, poor quality of silicone oil and catalyst.
6、Poor low-temperature performance of foam: poor intrinsic quality of polyether polyol, low functionality and large unsaturation under the same hydroxyl value, same amount of tin, low TDI index.
7、Poor air permeability
(1) Climatic conditions: low temperature
(2) Raw materials: high polyether polyol, high silicone oil activity;
(3) Low process formula content, high TDI index.
8, poor elasticity
(1) Raw materials: high polyether polyol activity, small relative molecular mass, high silicone oil activity;
(2) process formula: large amount of silicone oil, tin content, the same amount of tin under the water content, TDI index is high.