Polyurethane prepolymer is one of the main products of our company. In the process of R&D, production, sales and after-sales, some of the common questions and answers we encountered are reflected in today's article. I hope to be helpful.
1. Need to reduce prepolymer viscosity
- The synthesis temperature of the preferred prepolymer；
- Adding polyols to isocyanates；
- Increase stirring；
- Control the reaction rate to a slower degree；
- Use the right catalyst；
- Strictly control the moisture content in raw materials, the moisture content should be less than 0.05%;
- Prepolymer should be prepared under acidic conditions.
2. Yellowing problem
- Add antioxidants or UV stabilizers;
- Using aliphatic isocyanate;
3. NCO lower than theoretical value
- Water enters the reaction system;
- Wrong proportion;
- Loss of isocyanate;
- Alkaline side effects.
4. NCO is higher than theoretical
- Reaction time is too short;
- Insufficient amount of catalyst or inappropriate catalyst;
- Reaction temperature is too low;
- Wrong proportion.
5. The cause of bubbles
- Water into the reaction system;
- Incomplete degassing;
- Not suitable for mixing;
- Entrapment of air bubbles during pouring.
6. How to Dry the Primary Raw Materials
- Dry polyols in high temperature, vacuum, stirring, and vibration equipment;
- Drum dry nitrogen dry.
7. Reaction too fast
- Too alkaline;
- Too much catalyst;
- Raise the temperature too fast（For every increase of 10 degrees Celsius, the life in the kettle is shortened by 2 times）
8. Response too slow
- Insufficient amount of catalyst；
- Reaction temperature is too low.
9. Improve wear resistance
- Use of appropriate primary raw materials, especially hard segment materials;
- Using Teflon Additives.
10. Improve low temperature compliance
- Use higher molecular weight polyether polyols instead of polyester polyols;
- Use PTMEG instead of PPG.
11. Improve high temperature resistance
- Use of high performance raw material ingredients, especially chain extenders and isocyanates (e.g. HQEE, PPDI);
- Use the most stable antioxidant.
12. How to improve compression permanence
- Use appropriate primary raw materials;
- Use trifunctional chain extenders;
- Use a higher NCO index;
- Optimizing Mixing Temperature;
- Use trifunctional isocyanate.
13. How to Reduce Energy Absorption
- Use raw materials with linear polymerization, no branching and good hard segment formation properties.
14. How to make transparent PU
- Reduce the crystallinity of the hard segment (appropriate processing conditions and/or use special chain extenders);
- Change NCO%;
- Disrupt hard segment order.
Shandong Xinruituo Precision Industry Co., Ltd., a manufacturer of polyurethane raw materials, has 16+ years of experience in the development and production of polyurethane prepolymers. Polyurethane prepolymers can be customized according to customer needs. We will provide you with products with stable performance and perfect after-sales service. Welcome new and old customers to negotiate with us.
