Effect of co‐promoter and secondary monomer on shrinkage control of unsaturated polyester (UP)/styrene (St)/low‐profile additive (LPA) systems cured at low temperatures

Abstract

ABSTRACT:A series of linear functionalized polyorganosiloxanes of the type Me 3 SiO[MeSiO(CH 2 ) n R] x (Me 2 SiO) y SiMe 3 , where n ϭ 2, R ϭ O(CH 2 )NMe 2 ; n ϭ 1, R ϭ O(CH 2 )OEt; n ϭ 4, R ϭ O(CH 2 )COOEt; n ϭ 3, R ϭ O(CH 2 )Me, have been prepared and characterized. Functional group loadings of ϳ4 mol % (x ϭ 1, y ϭ 25), ϳ11 mol % (x ϭ 3, y ϭ 23), and ϳ30 mol % (x ϭ 8, y ϭ 18) were obtained by reacting commercially available copolymers Me 3 SiO(MeSi{H} O) x (Me 2 SiO) y SiMe 3 with the appropriate ratios of x : y , with the required quantities of HO(CH 2 ) n R, using dichloro(1,5-cyclooctadiene)-platinum(II) as catalyst. Amine, ether, ester, and alkyl functionalized siloxanes were obtained in good yields after purification, and each fluid polymer has been characterized by 1 H and 13 C-nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectral measurements, elemental analysis, viscosity, surface tension, and density measurements. The functionalized polymers exhibit Newtonian behavior over the range of shear rates 0.4 -79.4 s Ϫ1 , and significant viscosity enhancements were observed for all functionalized polymers compared with poly(dimethylsiloxane) fluids of similar chain lengths. The functionalized siloxanes exhibited in almost all cases an increase in both viscosity and density as the functional group loading increased. The surface tensions of the polymers have also been determined and lie within the range 18.8 -22.3 mN m Ϫ1 .

Relation between volumetric changes of unsaturated polyester resin and surface finish quality of fiberglass/unsaturated polyester composite panels

“…Studies demonstrated that the surface finish was improved by the use of LPA up to a critical value after which quality generally decreases or remains constant [16–18]. The cure shrinkage compensation mechanisms of unsaturated polyester, caused by LPA, have been extensively studied in the past decades [19–27]. The predominant mechanisms are the phase separation between the LPA and UP resin during the curing process and the microvoids formation at the interfacial regions between the LPA and UP phases [19, 21, 23–28].…”

Reaction‐induced phase separation in poly(vinyl acetate)/polyester blend

“…For instance, the mechanism of shrinkage control, in particular the formation of microvoids, has been widely investigated. 7,[9][10][11] In the present study the cure process was examined globally with a particular attention to the early stages of curing, which is often neglected. In addition, cure temperatures close to those used in industrial practice were investigated.…”

Effects of reactive low‐profile additives on the volume shrinkage and internal pigmentability for low‐temperature cure of unsaturated polyester

“…Most recently, interest in the development of low shrinkage UP resins for low temperature applications has grown considerably in the industry, which has attracted some research attention. 21,22 The objective of this work is to investigate the effects of reactive vinyl acetate-based block copolymer types of LPA on the volume shrinkage characteristics and internal pigmentability for styrene(ST)/UP/LPA ternary systems cured at low temperatures. Using an integrated approach combining the static ternary phase characteristics of ST/UP/LPA at 25°C, cured sample morphology, reaction kinetics, microvoid formation, and property measurements, factors leading to both good volume shrinkage control and acceptable internal pigmentability for the molded parts are discussed.…”