Crosslinking of unsaturated polyester resins studied by low-resolution1H-NMR spectroscopy

Abstract

ABSTRACT:The curing behavior of five unsaturated polyester resins with different molar ratios of styrene to the double bonds in the polyester chain (MR) was investigated. The gel time was measured according to a standard method by the Society of the Plastic Industry (SPI) and by low-resolution pulse nuclear magnetic resonance (LRP-NMR). The gel and curing times decreased and the maximum temperature of the reaction increased when the MR was decreased. The proton mobilities and populations were measured by LRP-NMR. Three components could be seen in the crosslinking reaction: styrene (very mobile, T 2 à 3 s), free polyester polymers (less mobile, T 2 à 150 ms), and cured resin (immobile, T 2 à 0.04 ms). The third component, cured resin, could be detected at the gel point. At this point, the proton mobilities of styrene and free polyester polymers were rapidly decreasing and the proton populations of the cured resin started to increase.

Correlation of viscoelastic properties with low‐resolution 1H‐NMR measurements of crosslinking unsaturated polyesters

“…Herein, lower MRs gave longer gel time, which results. 14 The same effect could be seen at 80ЊC, except that resin 2 (MR Å 5.1) had a shorter gel can be explained by the different amount of inhibitors used in these resins. time than resin 3 (MR Å 2.7).…”

“…Tetrahydrofuran was used as a populations could be measured as described presolvent, and polystyrene standards were used for viously. [14][15][16] The populations and T 2 values were the calibration. The MR of styrene to the double plotted with curing time.…”

“…also been studied by NMR measurements. [14][15][16] In a recent article, we presented low-resolution pulse 1 H-NMR (LRP-NMR) measurements of the crosslinking reaction. 14 Proton mobilities and popula-EXPERIMENTAL tions were measured, and we could identify three components in the crosslinking reaction.…”

“…The whole curing reaction of the resin was anapromoter at 25ЊC, and by 2 wt % benzoyl perlyzed by using LRP-NMR, according to the oxide ( BPO; Interox BP-50-FT, Peroxid-Chemie method described previously. 14 All experiments GmbH, Mü nchen, Germany ) at 80ЊC.…”

Synthesis and properties of unsaturated epoxyfumarate resins

“…The most important features of these resins are chemically resistant epoxy backbone and terminal unsaturated vinyl groups that can be easily cured by copolymerization with vinyl monomers in analogy with the unsaturated polyesters. [7][8][9][10][11][12][13] Continuing the previous studies, we synthetized the resins by the addition of acidic maleate ester to the epoxy resin and copolymerized them with styrene. Properties of the obtained epoxymaleate resins were compared with those for epoxyfumarate.…”