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Formation of a fibrillar morphology of crosslinked epoxy in a polystyrene continuous phase by reactive extrusion
Author(s) -
Fenouillot Françoise,
PerierCamby Hervé
Publication year - 2004
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.20057
Subject(s) - materials science , diglycidyl ether , epoxy , comonomer , extrusion , polystyrene , composite material , reactive extrusion , polymer blend , phase (matter) , bisphenol a , plastics extrusion , diamine , polymer chemistry , polymer , chemical engineering , monomer , copolymer , organic chemistry , chemistry , engineering
An immiscible polymer blend where the dispersed phase is fibrillar was prepared by in situ crosslinking of the minor phase. A model polystyrene/epoxy‐amine blend was selected on the basis of rheological (achievement of the fibrillar structure) and reactivity (fast crosslinking) criteria. The system was a polystyrene/diglycidyl ether of bisphenol A (DGEBA)‐aminoethyl piperazine (AEP) blend. At the temperature of extrusion, 180°C, the DGEBA is immiscible in PS and heterogeneous material is obtained. The elongational flow imposed by drawing the extrudate at the die exit permitted controlled generation of a fibrillar morphology of the dispersed epoxy phase, with a fiber diameter of 1 μm and an aspect ratio greater than 100. It was shown that when the amine comonomer was injected into the extruder, its reactivity with DGEBA at high temperature was high enough to ensure partial crosslinking of the epoxy. The fibrils were formed even though the gel point of the epoxy phase was exceeded. However, above a certain critical insoluble fraction that we estimated to be between 45% and 70%, a coarsening of the structure appeared, caused by the decreasing deformability of the domains and their coalescence. Finally, for our system, the crosslinking of the dispersed phase up to 90% of insoluble fraction did not totally stabilize the morphology after the second processing step (injection molding). Polym. Eng. Sci. 44:625–637, 2004. © 2004 Society of Plastics Engineers.