Effect of phenol end functional switching segments on the shape memory properties of epoxy‐cyanate ester system

Abstract

The effect of phenol end functional shape memory oligomers on the shape memory properties of an epoxy‐cyanate ester resin system was examined. The basic resin system consisted of diglycidyl ether of bisphenol A (DGEBA) cured with bisphenol A dicyanate (BADC). For conferring the shape memory properties, the switching segment (SS) components selected are α, ω‐phenol‐terminated poly(tetramethyleneoxide) (PPTMO), poly(ε‐caprolactone) (PPCL), and poly(propylene glycol) (PPPG). Epoxy‐cyanate ester blend of defined composition was analyzed for thermal, mechanical, thermo‐mechanical, and shape memory properties at two concentrations of the three SSs. The transition temperature of heavily SS loaded matrix increased in the order: PPTMO < PPCL < PPPG commensurate with crystallizability of SS segments at ambient. For same reason flexural property showed an increasing trend. This is in league with the increased crystallizability of the shape memory polymer components. The shape fixity, recovery extent, and recovery time followed a reverse order: PPPG < PPCL < PPTMO. In contrast to the alcohol terminated shape memory components, phenol terminal groups were helpful in integrating the shape memory segments into the matrix by way of reaction with both epoxy and cyanate groups. The coreaction was conducive for achieving better shape memory properties and decreasing the transition temperature. A direct relation existed between the modulus ratio and the shape recovery property. Higher concentration of the SSs caused a diminution in transition temperature but enhanced the shape memory properties, though the mechanical properties were adversely affected. The shape recovery increased with increase in temperature. All polymers possessed good mechanical properties and thermal stability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41196.

Shape memory CTBN/epoxy resin/cyanate ester ternary resin and their carbon fiber reinforced composites

“…Furthermore, peaks of ‐OCN group (2270 and 2238 cm −1 ) and epoxy ring (913 cm −1 ) were disappeared during the curing. It should be noted that the presence of peaks at 1570 and 1370 cm −1 corresponding to C─N and CN of triazine indicated homopolymerization of CE and peak at 1730 cm −1 indicated the formation of oxazolidone ring structure which come from the reaction between epoxy ring and cyanate group . Moreover, there are new peaks of 1210 and 1050 cm −1 corresponding to ester group, indicating the reactions between CTBN and CE.…”

“…It should be noted that the presence of peaks at 1570 and 1370 cm −1 corresponding to C─N and C N of triazine indicated homopolymerization of CE and peak at 1730 cm −1 indicated the formation of oxazolidone ring structure which come from the reaction between epoxy ring and cyanate group. 29,30 Moreover, there are new peaks of 1210 and 1050 cm −1 corresponding to ester group, 31 indicating the reactions between CTBN and CE. Furthermore, the presence of the peaks at 1565 and 1370 cm −1 corresponding to triazine rings in the precured CTBN/EP/CE spectrum indicated that the corresponding reactions had already taken place at the mixing stage of the components.…”

High glass transition temperature shape‐memory materials: Hydroxyl‐terminated polydimethylsiloxane‐modified cyanate ester

“…Furthermore, peaks of ─OCN group (2270 and 2238 cm −1 ) and epoxy ring (903 cm −1 ) disappeared during the curing. It should be noted that the presence of peaks at 1570 and 1370 cm −1 , corresponding to C─N and C═N of triazine, indicated homopolymerization of cyanate ester, and a peak at 1730 cm −1 indicated the formation of an oxazolidone ring structure, which comes from the reaction between epoxy ring and cyanate group …”

Shape memory effect on the formation of oxazoline and triazine rings of BCC/DGEBA copolymer

“…Subsequently, the third peak at 286.1 eV represents N=C-O bonds of the oxazoline ring indicating the successful epoxy and cyanate ester co-reaction and the final peak at 288.1 eV confirm the C-C=N bond formation 26 . The shape fixity of a material mainly depends on the glassy state modulus (E g ), high E g provides higher shape fixity 27 . 2c shows the deconvolution of N1s signal into two peaks; the peak appeared at 402.5 eV was assigned to the presences of C=N-C bonds of triazine ring in the polymer network and the second peak at 399.5 eV corresponds to the formation of C-N bond.…”

“…In addition, the presence of aliphatic chain 10,27 in the cyanate ester (BCC) significantly contributes to the effect of the shape memory behaviors of copolymers. When the sample was attaining at T switch (175 ºC), 98% recovery was obtained and above the T switch (T trans +25) 100% recovery of sample was obtained.…”