Polyurethane flexible foam 15 common problems and solutions, absolutely valuable, hurry to collect it!
The accidents and problems encountered in the actual foaming production of polyurethane flexible foam are diverse, and each production accident is caused by a variety of factors. In the analysis of accidents caused by complex factors, it is generally difficult to list all the influencing factors and the main factors that really play a role. Here is a summary of 15 frequently encountered problems and their causes, let’s take a look together!
Polyurethane flexible foam common problems and solutions
1、High closed pore rate
a, polyether polyol: high proportion of ethylene oxide, high activity, mostly occurs in the replacement of polyether polyol with different activity.
b, process formula: stannous octanoate dosage, high activity of isocyanate, large cross-linking degree, fast cross-linking speed, too much amine and physical blowing agent caused by the low internal pressure of the foam, foam elasticity can not be opened when the TDI index is too large, will also lead to high closed porosity.
2、Shrinkage (gel speed is greater than the speed of foaming)
a, high closed pore rate, shrinkage when cooling.
b, process conditions: low temperature, low material temperature.
c, process formula: excessive silicone oil, excessive physical foaming agent, TDI index is too low.
3、Inside crack
a、Process condition: low temperature, high temperature of reaction center.
b, process formula: low TDI index, more tin, high early foaming strength.
c、High activity of silicone oil and low dosage.
4、Top crack (unbalanced speed of aerogel)
a, process conditions: low temperature, low material temperature.
b, process formula: catalyst dosage is not enough, amine dosage is less, silicone oil quality is not good.
5, bottom corner crack (too much amine, foaming speed is too fast)
a, surface macropore: excessive amount of physical foaming agent, poor quality of silicone oil and catalyst.
6、Poor low temperature performance of foam
a, poor intrinsic quality of polyether polyol, in the same hydroxyl value, low functional degree, unsaturation, the same tin dosage, TDI index is low.
7、Poor aeration
a, climatic conditions: low temperature.
b, raw materials: high polyether polyol, high silicone oil activity.
c, process formula: more tin or the same amount of tin, less water and amine content, high TDI index.
8, poor inverse elasticity
a, raw materials: high activity of polyether polyol, small relative molecular mass, high activity of silicone oil.
b, process formula: large amount of silicone oil, more tin, more water in the same amount of tin, high TDI index.
9、Poor tensile strength
a, raw materials: too much low-molecular polyether polyol, the same hydroxyl value of low functionalities.
b, process formula: less tin gel reaction is not good, in the same amount of tin, TDI index is high, less water cross-linking degree is low.
10、Smoke when foaming
a, excess amine prompted by water and TDI reaction released a lot of heat, low boiling point material evaporation and smoke.
b、If it is not scorched heart, the smoke is mostly composed of TDI, low boiling point substances and monomeric naphthenes in polyether polyol.
11、Foam with white rib
The reaction speed of foaming and gel is fast, and the transfer speed is slow in continuous foaming, and the dense layer is generated by local extrusion, resulting in the phenomenon of white tendon. The transfer speed should be increased in time, or the material temperature should be lowered and the amount of catalyst should be reduced.
12、Crispy foam
There is more water in the recipe, the generation of diurea has not been dissolved in silicone oil, poor tin catalyst, cross-linking reaction is not sufficient, small relative molecular mass polyether polyol content, the reaction temperature is too high, the ether bond breakage reduces the foam strength.
13、Foam density is lower than the set value
Foaming index is too large due to inaccurate measurement, high temperature and low gas pressure.
14、Foam has bottom skin, side skin, bottom step cavitation
Tin polyamine less, slow foaming speed, fast gel speed, in continuous foaming with temperature too low.
15、Large elongation rate
a, raw materials: polyether polyol with high activity and small functionalities.
b, process formula: TDI index low crosslinking is not enough, more tin, more silicone oil.
Translated with www.DeepL.com/Translator (free version)
