Blends of epoxy/anhydride thermosets with a high-molar-mass poly(methyl methacrylate)

MJ GALANTE; PA OYANGUREN; K ANDROMAQUE; PM FRONTINI ; RJJ WILLIAMS

POLYMER INTERNATIONAL

JOHN WILEY & SONS LTD

Lugar: LOndres; Año: 1999 vol. 48 p. 642 - 648

0959-8103

Poly(methyl methacrylate) (PMMA,Mn=232000) was used to modify a stoichiometric epoxy(diglycidyl ether of bisphenol A; DGEBA)±anhydride (methyl tetrahydrophthalic anhydride; MTHPA)thermoset. PMMA concentrations in the range 3±7wt% led to morphologies consisting of a continuousPMMA-rich region that appeared rough and striated in scanning electron micrographs and largedomains of the thermoset exhibiting a dispersion of PMMA-rich particles in the micrometre range.These morphologies are the result of the critical point location, estimated at 2.1wt% PMMA as a resultof the high molar mass of the additive. A 5wt% PMMA led to an increase of the stress intensity factorKIC from 0.65MPam1/2, for the neat thermoset, to 0.94MPam1/2. However, Tg was reduced from 117°Cfor the neat thermoset to about 105°C for the PMMA-modi®ed material. The Tg decrease is ascribed tothe differential segregation of both monomers to the PMMA-rich phase. No in¯uence of PMMAaddition on the cure kinetics was observed. An upper critical solution temperature was observed,meaning that cloud-point conversions increased with cure temperature. Phase separation took placebefore gelation in the temperature range investigated in this study.