Curing Reactions of Bismaleimidodiphenylmethane with Mono- or Di-functional Allylphenols. High Resolution Solid-State 13C NMR Study

Abstract

ABSTRACT:Analysis of the curing reactions of bismaleimidodiphenylmethane (BMI) with diallylbisphenol-A (DABA) or o-allylphenol (AP) with the high resolution solid-state 13 C NMR technique revealed that while cured products of BMI and AP are formed through ene-reaction and the sequential Diels-Alder reaction, no Diels-Alder reaction occurs in the case of DABA and only ene-reaction and polymerization proceed. This shows that the crosslinking of such widely used curing system proceeds via a different manner suggested previously.KEY WORDS Curing Reaction/ Diels-Alder Reaction/ ene-Reaction / Bismaleimide / Diallylbisphenol-A / Solid-State 13 C Nuclear Magnetic Resonance / The curing system of bismaleimide has been widely used as thermosetting polyimides, which provides excellent thermal stability but brittleness simultaneously because of the high crosslinking density of the network. In order to add toughness to bismaleimide resins, modification has been made by the addition of diallyl compounds such as diallylbisphenol-A (DABA). 1 • 2 The course of this reaction has been investigated and ene-and Diels-Alder reactions were suggested to be involved in this curing system based on the model reaction of Nphenylmaleimide (PMI) and o-allylphenol (AP). 3 -5 The preceding paper showed that the thermal reaction of PMI and AP gave ene-and Diels-Alder adducts but PMI and DABA did not give the Diels-Alder adduct. 6 However, the practical curing reaction remains uncertain because the curing products are generally insoluble toward almost of organic solvents, which prevents to characterize the reaction products.High resolution solid-state NMR with CPMAS (cross polarization magic angle spinning), developed by Schaefer, 7 has been applied to the analysis of insoluble polymer such as cured thermoset resins. 8 Our previous studies showed that the solid-state 13 C NMR is useful to investigate the curing reactions of bismaleimide resins. 9 -12 Although the solid-state 13 C NMR spectrum of the cured product of bismaleimidodiphenylmethane (BMI) with DABA has been illustrated by Carduner et al. 13 • 14 detailed descriptions are not available. On the basis of fundamental data of the model reactions, we report in this paper the direct measurements of the curing reactions of BMI and DABA with a high resolution solid-state 13 C NMR. EXPERIMENTAL MaterialsBMI, purchased from Wako Pure Chemical Industries, was recrystallized from chloroform-methanol. DABA 410 was obtained from Mitsui Toatsu Chemicals Inc. PMI and o-AP were purchased from Wako Pure Chemical Industries. Sample PreparationMono-or di-functional maleimides and mono-or di-functional allylphenols were mixed in a round bottom flask and heated by an oil bath at 150°C for 15 min. Continuous stirring led to a homogenous melt. This mixture was put in a closed aluminous vessel and heated at 175°C for 2 h, at 200°c for 1 h, and at 250°C for 1 h in an air oven. Each stage samples were analyzed by liquid-state and solid-state 13 C NMR. Liquid-State 13 C NMR MeasurementsNMR spectra were obtained...

Mechanical and thermal properties of modified bismaleimide matrices toughened by polyetherimides and polyimide

“…Curing reactions and schematic representation of cured polymer network are shown on Fig. . The resulting plates were cut by CNC machine (COMAGRAV, COMAC spol.…”

High Performance Thermoplastic/Thermosetting Composites Microstructure and Processing Design Based on Phase Separation

“…The following reaction types have been proposed to be involved in the curing process: ENE, Diels-Alder, homopolymerization, and alternating compolymerization. Allyl phenol compounds are expected to co-react with BMI to give linear chain extension by an ENE-type reaction in lower temperature range of 120-170℃ and show a lower cure activation energy barrier, and this is followed by a Diels-Alder reaction at a high temperature range of 180-200℃ with bigger cure activation energy (Mijovic＆Andjelic,1996;Shibahara et al, 1998;Rozenberg et a,2001;Xiong et al, 2003). The effects of cure reaction energy Ea(ps) were also observed in DGEBA/MTHPA/PES and DGEBA/MHTPA/PEI systems as displayed in Table 10, wherein the initiator BDMA was employed or not.…”

Phase separation time/temperature dependence of thermoplastics-modified thermosetting systems

“…Allylphenol compounds are expected to react with BMI to give linear chain extension by an ENE-type reaction in lower temperature range of 120uC-170uC and show a lower cure activation energy barrier. This is followed by a Diels-Alder reaction at the high temperature range of 180uC-200uC [43][44][45][46][47] with higher cure activation energy. It is probable that lower cure reaction energy barrier results in low E a (ps).…”