Development of low temperature cure hybrid benzoxazine-epoxy resins for thermally stable and moisture resistant applications

• Published in: Reactive & functional polymers 2024-11, Vol.204, p.106032, Article 106032
• Main Authors: Mohamed Mydeen, K., Madesh, Priyanka, Appasamy, Subasri, Krishnasamy, Balaji, Muthukaruppan, Alagar
• Format: Article
• Language: English
• Subjects: Curing catalysts; Hybrid benzoxazine-epoxy resin; Hydrophobic behavior; Low temperature cure; Thermal stability
• ISSN: 1381-5148
• DOI: 10.1016/j.reactfunctpolym.2024.106032

New type of diallyl bisphenol-A (ABA) based benzoxazines and benzoxazine resins tailored with epoxy groups for low-temperature curing, have been developed using various curatives for high performance applications. The molecular structure of the synthesized compounds was analyzed using HRMS, 1H NMR, 13C NMR and ATR-FTIR analytical techniques. The cure behavior (Tp) of benzoxazine (Bz) and benz-epoxy (Bz-Ep) resin in the absence and presence of different nature of curatives were studied using DSC to evaluate their applicability for advanced composite applications. The values of Tp obtained are 279 °C, 190 °C and 247 °C for ABA-a, ABA-dmapa and ABA-ipa respectively. The cure behavior has been further lowered by converting ally group present in the benzoxazine has been transformed into epoxy groups by appropriate mechanism. The curing (Tp) temperature observed for hybrid ABA-a-Ep, ABA-dmapa-Ep and ABA-ipa-Ep benz-epoxy resins are 151 °C, 226 °C and 160 °C, 187 °C and 150 °C, 211 °C respectively. The Tp of different benz-epoxy resin systems studied in the presence of catalysts were found to be in the range of 101-155 °C. With a Tmax of 484 °C and a char yield of 43 %, poly(ABA-a) exhibits impressive thermal stability when compared to other synthesized polybenzoxazines. Further, incorporating various curatives into the benz-epoxy matrix enhances its thermal stability and char yield compared to the neat matrices. Additionally, the developed samples exhibit excellent moisture resistant (0.75 %) and hydrophobic nature with the highest contact angle value of 152o for poly(ABA-a). The findings from various studies indicate that the hybrid benz-epoxy resins demonstrate characteristics such as low-temperature curability, thermal stability, hydrophobicity. These results render them appropriate for a diverse array of high-performance industrial and engineering uses. [Display omitted] •Diallyl bisphenol-A (ABA) based benzoxazines and benzoxazine-epoxy resins were synthesized.•In absence of catalyst diallyl bisphenol-A-dmapa-Ep cures at 160 °C and 187 °C.•In presence of oxalyldihydrazide catalyst diallyl bisphenol-A-dmapa-Ep cures at 101 °C and 155 °C.•Poly(ABA-a) in absence and presence of catalyst (dicy-urea) exhibit higher CY value.•Poly(ABA-benzoxazines) showed better hydrophobic nature than respective polybenz-epoxies.