| 摘要 |
PROBLEM TO BE SOLVED: To obtain a compsn. which gives a cured item having a highly stable network and exhibiting a low compression set in a short curing time by using a copolymer which has specified physical properties before curing and is obtd. from vinylidene fluoride and a hexafluoropropene-based ionically curable comonomer. SOLUTION: A copolymer used here exhibits, by gel permeation chromatography, such a fraction of polymers having a mol.wt. lower than 10,000 that it is 3wt.% or lower when the Mooney viscosity before curing is 20 and that it is 0.5wt.% or lower when the Mooney viscosity is 50. The copolymer is highly stable to thermal decomposition when it is in the state of a latex after polymn., after coagulation, washing, or drying or before curing; the copolymer after thermally treated at 250 deg.C for 1hr does not exhibit the existence of a double bond: -CH=CF- at a vibration frequency of 1720cm<-1> in its FT-IR analysis. The copolymer can form a stable network in such a short curing time that it may be 30min or lower and it may be even zero, thus giving a cured copolymer exhibiting a compression set lower than 20% and enabling the automatic production of O-rings. |
