Curing Process of Benzoxazine Systems. An Experimental and Theoretical Study

Abstract

A mathematical model that simulates the curing process of benzoxazine (Bz) systems is presented. The model predicts the conversion, gel point and Tg along the curing process, and considers the diffusional limitations to mass transfer due to the increase in the system viscosity along the process. This model can be used to select an appropriate combination of time and temperature in order to obtain a material with pre-specified properties. The theoretical parameters were adjusted with experi-mental data: conversion, weight-average molecular weight, weight fraction of solubles and Tg. The Bz based on bisphenol A and aniline (BzBA) was used to adjust the model. The curing kinetic of this Bz was followed by FTIR, SEC and DSC, considering five different curing conditions. A very good agreement between experimental and simulated values was ob-served, even when curing is carried out under differ-ent temperatures profiles.

Tetramethyl guanidine‐assisted synthesis and thermal crosslinking of multifunctional benzoxazine monomers based on natural phloretic acid

“…As a consequence of this ring-opening, a progressive decrease of the band at 1510 cm À1 , attributed to the 1,2,3-tri-substituted aromatic skeleton vibration is also observed, and the apparition of a new band at 1490 cm À1 corresponding to the 1,2,3,5-tetra-substituted aromatic skeleton vibration is detected. 53 This is indicative to the formation of the phenolic Mannich bridges. In addition, other vibrations indicative of the crosslinking network are the bands centered at 1650 and 3380 cm À1 .…”

Synthesis and characterization of polybenzoxazine/silica‐based hybrid nanostructures for flame retardancy applications

“…Bisphenol A and aniline‐based conventional benzoxazine was prepared from previously reported procedures. [ 53 ] 1,3,5‐triphenylhexahydro‐1,3,5‐triazine (0.05 mol), bisphenol A (0.075 mol) and paraformaldehyde (0.15 mol) were added in a 250 ml round bottom flask provided with mechanical stirring. Then, 5 ml of 1,4‐dioxane were added to the system to favor the reagents mixing.…”

Tailoring thermal and thermomechanical properties of biobased blends by hybridization of difuran benzoxazine with polysiloxane‐based benzoxazine and epoxy monomers

“…The synthesis of BA-a was carried out using a two-stage procedure previously reported. 37 The synthesis methods of silicon-and furan-based benzoxazines are detailed below.…”

“…The synthesis of the conventional BA-a was carried out using a two-stage procedure according to the literature. 37 In the first stage,…”

“…BA-a curing has been intensively studied in our previous work. 37 BA-a exhibits a typical curing exotherm for bifunctional benzoxazines centered at 233 C. The curing reaction of BA-a by thermally induced oxazine-ring opening generates an oxazine zwitterion, which is inserted in free ortho-position, leading to the formation of a threedimensional network of phenolic Mannich bridges. 28 Regarding Pr(BA-3aptms), the ring opening reaction starts at 235 C with a maximum centered at 270 C. Spont on et al 31 and Forchetti Casarino et al 34 demonstrated that at high temperature both oxazine-ring opening curing and incomplete sol-gel process occur, generating a chemical structure based on polysilsesquioxane bonds and phenolic Mannich bridges.…”