Note polyurethane rubber seals made ​​factors

① prepolymer synthesis temperature control , the temperature controlled at 75 ~ 82 ~ C, high performance will decrease the prepolymer synthesis , low will prolong the reaction time . MOCA when mixed with the prepolymer temperature at 90 ~ 110 ℃, high will reduce the hardness and strength of the product , the mixture will increase low spike Yan, is not conducive to casting operations. Curing temperature 120130 ~ C, high will , MOCA decomposition, is not conducive to cross -linking reaction , while the other side reactions increases , lower molding time will be extended . MOCA melting temperature can be controlled just melt into a liquid , can not continue to heat , or liquid MOCA become darker in color , decomposition , affecting crosslinking molding.
⑦ time control synthesis reaction 2h, intermittent vacuum for 2h , and then stored at room temperature and placed in secret . Prepolymer synthesis at 75 ~ C , the no more than 4 ~ h, more {j in high temperature (100 ~ C) for more than 2h, otherwise it will reduce product performance. Pouring should be completed within 1 ~ 2min nephew because prepolymer and MOCA stabilization period after mixing is very short, only 4 ~ 5min, stirring well takes time .
Molding and vulcanization time for the product to the shape and size , are generally between 15 ~ 30min , no less , to ensure the molded product . Sometimes encounter large production such as wheels , rollers , and its curing ( refer molded ) longer and need 2 ~ 3h OK .
③ degassed prepolymer is good or bad degassing casting polyurethane rubber plastic seal made ​​key to success, the prepolymer synthesis on standing , 75 ℃ degassed under vacuum to remove most of the gas in the prepolymer ; prepolymer MOCA body and prior to mixing needs to be heated to a temperature 100 ~ 1 10 ℃ degassed. Meanwhile vacuum (- 0.095MPa) degassing 1Omin, then remove the air bubbles in the bottom stirring upper turn , pulls out the vacuum degassing 10rain, the prepolymer to exclude air bubbles in the clean, in order to cast products with the curing agent are mixed .
④ pressure is generally 14MPa pressure can be.
⑤ release agent Luoyang Liming Research Institute of Chemical 's 4031 production of polyurethane release agent, ester or ether -based polyurethane are preferred release agent. The 3rd month of Na- purpose lubrication , ordinary three calcium-based grease can also be used .
⑥ a set A is a prepolymer of NCO content of the setting , primarily based on degree of erosion products , mechanical and performance requirements on the performance of casting process . Average high hardness bigger ; smaller low hardness products mouth , mouth commonly used value of 3 % to 6% .
⑦ Select the main raw material selection , depending on whether water, heat water , depending ether except ammonia furans superior water resistance ester -based polyurethane .
⑦ mold manufacturing polyurethane container seals the mold and demanding , high structure is in addition to children with normal rubber mold requirements, should not be too small spout , structural casting, stripping and cleaning. In addition to the end of the structure , the cover , the middle block at least three blocks.
Casting shrinkage polyurethane rubber , is generally 1.30% to 1.35 %