Liquid rubber modi®ed vinyl ester resins: fracture and mechanical behavior

M.L. AUAD; P.M. FRONTINI; J. BORRAJO; M.I. ARANGUREN

POLYMER

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2001 p. 3723 - 3730

0032-3861

AbstractThe fracture and mechanical behavior of vinyl ester resins (DVER) cured with styrene (S) and modi®ed with two different liquid rubbershas been determined and related to the microstructure of the resulting modi®ed thermosets. Carboxyl terminated poly(butadiene-co-acrylonitrile)(CTBN), a common toughening agent for epoxy resins, is an almost unreactive rubber with the DVER and S comonomers. Duringcrosslinking the system undergoes a phase separation mechanism similar to that occurring in unsaturated polyester resins (UPE) modi®edwith a low pro®le additive (LPA), such as polyvinyl acetate (PVAc). This process leads to materials, which exhibit a sharp drop in density athigh CTBN concentrations ($10% by weight) and to the development of a co-continuous microstructure in these materials. This feature isconsistent with a maximum in fracture toughness as a function of the additive (CTBN) content, followed by a rapid deterioration in toughnessat higher concentrations. On the other hand, the use of a reactive rubber, vinyl terminated poly(butadiene-co-acrylonitrile, VTBN, as theadditive leads to a different morphology consisting on rubber inclusions in the thermoset matrix. This structure gradually reduces the fractureand mechanical performance of the resins modi®ed with increasing concentration of reactive elastomer.