| 摘要 |
Bismaleimides of the formula <IMAGE> wherein R1 and R2 each independently is H, C1-4-alkyl, C1-4-alkoxy, C1 or Br, or R1 and R2 together form a fused 6-membered hydrocarbon aromatic ring, with the proviso that R1 and R2 are not t-butyl or t-butoxy; X is O, S or Se; n is 1-3; and the alkylene bridging group, optionally, is substituted by 1-3 methyl groups or by fluorine, form polybismaleimide resins which have valuable physical properties. Uniquely, these compounds permit extended cure times, i.e., they remain fluid for a time sufficient to permit the formation of a homogeneous melt prior to curing.
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