| 摘要 |
A phenolic resin, near polyethylene terephthalate having exposed areas subject to degradation by vaporous materials, is cured by removing free phenol from the resin and heating It. During heating, air is suitably passed near the resin to remove formed vapours. Heating may be effected at 158-180≦̸C, pref. 155-175≦̸C for up to 8, pref. 4.6, hrs. The total wt. of free phenol in the resin can be 5-10%. The method is useful in construction of an electrical appts., e.g. a transformer contg. assemblies having wound conducting layers, the terephthalate being used as insulation between layers of the assembly. Embrittlement of the terephthalate is avoided.
|
