Electron-beam curing of thermoset resins for composites

Abstract: Electron-beams (EB) are an alternative to traditionalthermal curing when manufacturing thick thermoset composites.It is a quick and energetically efficient technique when curinglarge fiber reinforced parts. Most of the published work onEB-curing deals with curing of thin layers of resin or withcrosslinking of polymers.In this thesis, the curing of acrylic resins is studied tohighlight the critical parameters and the particularities ofEB-curing. Tgof the thermoset increases with increasingirradiation dose and levels-off at Tg?, when the resin is fully cured. As inthermal curing, the temperature during cure strongly affectsthe crosslinking of the resin and the thermo-mechanicalproperties of the cured thermoset. Up to Tg?, a linear relationship between the maximumtemperature during cure and Tgwas found.Carbon and glass fiber composites were EB-cured and tested.Adding fibers to the acrylic resins lowered the exotherm, whichclearly confirmed the importance of temperature during cure tofully crosslink the polymer matrix.Comparing EB-, UV- and thermal cure showed that the curingmethod was not the factor that most influenced the propertiesof the cured thermoset. The curing technique imposesconstraints, such as starting temperature and curing time, butit does not influence directly the polymerization and thenetwork formation. These properties are inherent to the monomerused.An acrylate resin was blended it with a series of alkyl andmethacrylate functionalized hyperbranched polyester. Thephase-separated thermoset exhibited increased toughness.Keywords:electron-beam, thermoset, acrylic resin,hyperbranched polyester, thermal effect, toughening