Common problems and solutions of polyurethane elastomers
1. The viscosity of the prepolymer needs to be reduced
(1) Optimizing the synthesis temperature of the prepolymer;
(2) Add polyol to isocyanate;
(3) Increase stirring;
(4) Control the reaction speed to a slower degree;
(5) Use the correct catalyst;
(6) Strictly control the moisture content in the raw materials, and the moisture content should be less than 0.05%;
(7) The preparation of the prepolymer should be carried out under acidic conditions.
2. Yellowing problem
(1) Add antioxidants or UV stabilizers;
(2) Use aliphatic isocyanate.
3. NCO is lower than theoretical value
(1) Water enters the reaction system;
(2) The ratio is wrong;
(3) Loss of isocyanate;
(4) Side reactions caused by alkaline
4. NCO is higher than theoretical value
(1) The reaction time is too short;
(2) Insufficient amount of catalyst or inappropriate catalyst;
(3) The reaction temperature is too low;
(4) The ratio is wrong
5. Causes of bubbles
(1) Water enters the reaction system;
(2) Incomplete degassing;
(3) The mixing is inappropriate;
(4) Bubbles are involved in pouring
6. How to dry the main raw materials
(1) Put the polyol into a high-temperature, vacuum, stirring, and vibrating [wiki] device[/wiki] to dry;
(2) Drum dry nitrogen drying
7. The reaction speed is too fast
(1) Alkaline is too high;
(2) The amount of catalyst is too much;
(3) Increase the temperature too fast (every increase of 10 degrees Celsius, the life in the kettle will be shortened by 2 times)
8. The reaction speed is too slow
(1) The amount of catalyst is insufficient;
(2) The reaction temperature is too low
9. Improve wear resistance
(1) Use appropriate main raw materials, especially hard segment materials;
(2) Use Teflon additives
10. Improve low temperature flexibility
(1) Use higher molecular weight polyether polyol instead of polyester polyol;
(2) Use PTMEG instead of PPG
11. Improve high temperature resistance
(1) Use high-performance raw materials, especially chain extenders and isocyanates (such as HQEE, PPDI);
(2) Use the most stable antioxidant
12. How to improve compression forever
(1) Use appropriate main raw materials;
(2) Use trifunctional chain extender;
(3) Adopt a higher NCO index;
(4) Optimize the mixing temperature;
(5) Use trifunctional isocyanate
13. How to reduce energy absorption
Use raw materials that have linear polymerization, do not form branches and form good hard segment properties
14. How to make transparent PU
(1) Reduce the crystallinity of the hard segment (appropriate processing conditions and/or use special chain extenders);
(2) Change NCO%;
(3) Disrupt the order of hard segments
