Reaction-induced phase separation in poly(butylene terephthalate)-epoxy systems: 2. Morphologies generated and resulting properties

P. A. OYANGUREN; P. M. FRONTINI ; R. J. J. WILLIAMS; . VIGIER ; J. P. PASCAULT

POLYMER

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 1996

0032-3861

Poly(butylene terephthalate) (PBT) was used as a semicrystalline modifier of epoxy-aromatic diamineformulations in concentrations ranging from about 3 wt% to 8 wt%. The epoxy monomer was based ondiglycidylether of bisphenol A (DGEBA) and the diamines were either 4,4'-methylenebis [3-chloro 2,6-diethylaniline] (MCDEA) and 4,4'-diaminodiphenylsulfone (DDS). Using conversion-temperaturetransformation diagrams developed in part 1, thermal cycles were selected to generate differentmorphologies. In the case of PBT-DGEBA-DDS systems, phase separation in the course of reaction ledto a random dispersion of spherical particles (sizes in the range of 1 #m), rich in PBT. Small and wide angleX-ray scattering, carried out in situ, during cure, revealed that the dispersion of spherical particles wasproduced by a nucleation-growth mechanism and that crystallization took place after phase separation. Acompletely different morphology, characterized by a distribution of large and irregular semicrystallineparticles, was produced by crystallization before reaction. However, both types of morphologies introduceda small increase in the critical stress intensity factor. The main toughening mechanism was crack bridgingproduced by highly drawn thermoplastic particles. On the other hand, PBT-DGEBA-MCDEAformulations were cured at temperatures high enough to avoid crystallization of PBT during reaction. Inthis case, the PBT remaining dissolved in the matrix did not introduce any toughening effect.