Abstract:SynopsisCrosslinked compositions prepared from bismaleimidodiphenyl methane and diallylbisphenol A in the weight ratio of 0.99 to 1.31 have been subjected to dynamic mechanical thermal analysis (DMTA) . The glass transition temperatures of all these fully cured compositions are above 300°C.The stoichiometry of the reactants in the above range does not change the thermal degradation pattern of these crosslinked polymers. DMTA shows that there is a very small decrease in storage modulus at room temperature with … Show more
“…The obtained energies have values comparable with the literature data 14,32−38. In systems 2 and 3, where the cross‐linking reaction took place in the presence of MDABMI, new chemical reactions can take place, homopolymerization and copolymerization of double bonds or the Michael addition and “ene” reactions, which imply the transfer of amine protons to the double bounds of maleimide moieties39–44 (Schemes and ). In these systems, the chemical reactions presented above can take place simultaneously, resulting in high cross‐linked polymers.…”
Novel formaldehyde novolac resins at various molar ratios of monomers (4,4 -methylenedianiline/ p-nonylphenol/ p-formaldehyde) were synthesized in the presence of an acid catalyst. The obtained resins were characterized by using elemental analysis, FT IR, and 1 H NMR spectroscopic methods. Subsequently, these resins may further be modified by allylation and methacrylation and may be used as cross-linking agents for epoxy resin/bismaleimide resin formulations. The curing of epoxy and bismaleimide resins with formaldehyde resins (FR) and modified FR and the thermal decomposition behavior of cross-linked resins were studied by differential scanning calorimetry (DSC) and thermogravimetric (TGA) techniques. DSC scans for the curing of epoxy resins with FR show a single exothermic peak, which implied only the occurrence of cure reactions between epoxy ring and amine protons, whereas the DSC scans for the epoxy resins, bismaleimide resins, and modified FR systems have two exothermic peaks. The cured products possess a good thermal stability and low water absorption. C 2011 Wiley Periodicals, Inc. Adv Polym Techn 30: 219-233, 2011; View this article online at wileyonlinelibrary.com.
“…The obtained energies have values comparable with the literature data 14,32−38. In systems 2 and 3, where the cross‐linking reaction took place in the presence of MDABMI, new chemical reactions can take place, homopolymerization and copolymerization of double bonds or the Michael addition and “ene” reactions, which imply the transfer of amine protons to the double bounds of maleimide moieties39–44 (Schemes and ). In these systems, the chemical reactions presented above can take place simultaneously, resulting in high cross‐linked polymers.…”
Novel formaldehyde novolac resins at various molar ratios of monomers (4,4 -methylenedianiline/ p-nonylphenol/ p-formaldehyde) were synthesized in the presence of an acid catalyst. The obtained resins were characterized by using elemental analysis, FT IR, and 1 H NMR spectroscopic methods. Subsequently, these resins may further be modified by allylation and methacrylation and may be used as cross-linking agents for epoxy resin/bismaleimide resin formulations. The curing of epoxy and bismaleimide resins with formaldehyde resins (FR) and modified FR and the thermal decomposition behavior of cross-linked resins were studied by differential scanning calorimetry (DSC) and thermogravimetric (TGA) techniques. DSC scans for the curing of epoxy resins with FR show a single exothermic peak, which implied only the occurrence of cure reactions between epoxy ring and amine protons, whereas the DSC scans for the epoxy resins, bismaleimide resins, and modified FR systems have two exothermic peaks. The cured products possess a good thermal stability and low water absorption. C 2011 Wiley Periodicals, Inc. Adv Polym Techn 30: 219-233, 2011; View this article online at wileyonlinelibrary.com.
“…A review of the literature on reactions in various maleimide and bismaleimide systems, polymer-forming and non-polymer-forming alike, has revealed a number of proposed reaction paths in BMI formulations, though a comprehensive picture of the mechanisms and kinetics of cure has not yet emerged. The following reactions have been suggested to occur during cure of various BMI formulations: (1) homopolymerization of BMI via the reaction of maleimide CdC double bond that results in the formation of a four-member ring structure, 14 (2) homopolymerization of BMI via the reaction of maleimide CdC double bond between three BMI molecules, 15 (3) reactions between the double bonds of maleimide and allyl groups, which continue at higher temperature via Diels-Alder mechanism and maleimide oligomerization, 16 (4) reaction of bismaleimide with allyl component and/or another bismaleimide molecule via a free radical site on the methylene group, 17 (5) homopolymerization (vinyltype) of the allyl double bond, and (6) cross-linking via etherification (dehydration) involving hydroxyl groups of the allyl component. 13 The principal objective of this study is to investigate the mechanism and kinetics of cure of a two-component BMI formulation, composed of 4,4′-methylenebis[maleimidobenzene] and 2,2′-diallylbisphenol A, using in-situ real time fiber optic near-infrared (IR) spectroscopy.…”
An investigation was carried out on the mechanism and kinetics of cure of a two-component bismaleimide formulation, composed of 4,4′-methylenebis[maleimidobenzene] and 2,2′-diallylbisphenol A. In-situ real time study of the progress of reaction was conducted in the temperature range from 140 to 250°C using remote fiber optic near-infrared spectroscopy. The obtained signal was clean, free of noise, and remarkably reproducible. The principal reaction observed was an alternating copolymerization involving maleimide and allyl double bonds. Maleimide homopolymerization was detected only in the initial stages of reaction at temperatures above 200°C. The extent of self-condensation (or etherification) of hydroxyl groups on the allyl component, which leads to cross-linking, was observed to vary with reaction temperature, suggesting a path to tailor-making networks with desired morphology and physical/ mechanical properties.
“…Although several reports on BMI/DABPA resin have appeared, 1, 7-14 a clear picture of the chemical transformations which occur during curing has not yet been reached. The following reaction types have been proposed to be involved in the curing process: Ene, Diels−Alder, homopolymerization, rearomatization, and alternating copolymerization. ,− These processes are outlined in Figures and . In all of these transformations, maleimide moieties are converted to succinimide groups.…”
Section: Introductionmentioning
confidence: 99%
“…Fluorescence, FT-IR and UV reflection spectral characteristics are used to characterize various reactions. 1 Proposed curing mechanisms for BMI/DABPA resin. ,− 2 Additional reaction pathways during the curing of BMI/DABPA resin. ,− …”
Curing bis(maleimide)/diallylbisphenol A (BMI/DABPA) results
in the formation of a high-temperature thermoset resin. FT-IR, fluorescence, and
UV-reflectance spectroscopy were used to
investigate the cure behavior of this material under three different
cure schedules. Fluorescence signals
were quenched before curing due to the BMI component but increased and
eventually leveled off as cure
time increased. The largest fluorescence intensity increases
occurred after 80% of the phenylmaleimide
units were converted to phenylsuccinimide. Fluorescence signals
were observed in both short-wavelength
and long-wavelength regions. Model compound studies indicated that
the phenolic portion of the BMI/DABPA resin has a higher quantum yield for fluorescence at a shorter
wavelength than phenylsuccinimide
derivatives. Therefore, fluorescence emission observed near 356 nm
during curing is attributed to phenolic
structures. FT-IR was used to quantify the extent of succinimide
formation and to identify cross-linking
processes which occurred during high temperature curing (250−260
°C). High-temperature curing
processes were also identified by UV-reflection spectroscopy.
Various reaction pathways are discussed
in terms of their consistency with the spectroscopic data.
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