Effects of reactive low‐profile additives on the properties of cured unsaturated polyester resins. II. Glass‐transition temperature and mechanical properties

Abstract

ABSTRACT:The effects of reactive poly(methyl methacrylate) (PMMA) and poly(vinyl acetate)-block-poly(methyl methacrylate) (PVAc-b-PMMA) as low-profile additives (LPAs) on the glass-transition temperature and mechanical properties of low-shrink unsaturated polyester resin (UP) were investigated by an integrated approach of determining static phase characteristics, reaction kinetics, cured sample morphology, and property measurements. The factors that, according to Takayanagi mechanical models, control the glass-transition temperature in each phase region of the cured samples, as identified by both the thermally stimulated currents method and dynamic mechanical analysis, and the mechanical properties are discussed.

Effect of low-profile additives on thermo-mechanical properties of glass fiber-reinforced unsaturated polyester composites

“…The reduction of the flexural modulus was expected since the LPA used in the UP resin system were thermoplastic-based and thermoplastic has a lower modulus value compared to the UP resin (thermoplastic-based LPA modulus ¼ 2-3 GPa vs. UP resin modulus ¼ 2-10 GPa). A similar trend was found in the literature for the Young's modulus variation with LPA content [10][11][12][13][14][15] and the flexural strength evolution with an increase in LPA content for pultruded composites. 17 In the case of the 40% LPA content, the flexural modulus and strength standard deviations appeared to be higher.…”

“…The T g values measured by the two techniques followed the same trend: T g first increased with an addition of 10% LPA and then slightly decreased with the addition of 40% LPA. A similar behavior was observed in 10,11 where the addition of 10% PVAc or PMMA to UP led to 8 C increase in T g . As mentioned earlier, T g depends on a plasticization effect and a crosslinking effect.…”

“…With no LPA, the resin is homogeneous, whereas a co-continuous resin/LPA structure with microvoids is clearly visible with 10% and 40% LPA contents resulting in a compatible LPA/UP system as defined by Huang and co-workers. [10][11][12][13][14][15] Thermal properties…”

“…This change in morphology is closely related to a change in mechanical properties. Huang and co-workers [10][11][12][13][14][15] investigated in details of the compatibility of PVAc, PU, PMMA, and PS LPA systems with the UP resin and their effects on morphology and mechanical properties. The polarity difference between the LPA and the UP resin was determined as a main factor controlling the compatibility of the system and its morphology.…”

“…17,18 The evolution of glass transition temperature (T g ) with addition of LPA was also investigated by different researchers. 4,[10][11][12][13]15,17 It was determined that T g depended on two opposite effects: the plasticization of the resin system due to the presence of LPA which decreased T g and the extent of crosslinking in the UP phases which increased T g . Thus, T g can be improved or reduced depending which effect is more dominant.…”