| Popis: |
To facilitate the PPE /epoxy copolymer formation, PPE was redistributed with phenolic compounds to increase the reactive functional groups per PPE chain. Moreover, the resulting PPE with lower molecular weight improved the resin flow during lamination. An optimized process for producing low molecular weight PPE has been developed. The process was accomplished by redistributing regular PPE (0.46 or 0.40 intrinsic viscosity) with benzoyl peroxide and 4,4′-isopropylidenediphenol (BPA) in toluene. The benzoate group was found to be predominantly incorporated at the PPE chain end and the α carbon of the PPE repeating unit. A portion of the amine-containing phenolic end group, the quinone methide precursor, was oxidized to form a dihydro-1,3-benzoxazine derivative during the redistribution process. However, no dienone structural moiety, a proposed PPE redistribution intermediate, could be identified in the redistributed PPE. Two Tg values representing epoxy and PPE phases were usually observed in the PPE /epoxy laminates. Interestingly, the T8 of the PPE phase was equal to, or higher than, that of the PPE powder from which the laminate was made. |
