Bismaleimide resin

The BMT-biiilding blocks primarily used in commercial bismaleimide resins are 4,4 -bismaleimidodiphenylmethane, 2,4-bismaleimidotoluene [6422-83-9] 1,3-bismaleimidobenzene [3006-93-7J, and, sometimes, aUphatic BMIs based on alkanes. However, because of toxicity problems associated with MO A (4,4 -diaminodiphenylmethane) and other diamines with only one or two aromatic rings, polyaromatic diamines and BMIs based on them ate... 

Another approach to processible bismaleimide resins via a Michael addition chain extension, is the reaction of bismaleimide, or alow melting mixture of bismaleimides, with aminobenzoic hydrazide to provide a resin that is soluble in various solvents, such as acetone [67-64-1methylene chloride [75-09-2] and dimethylform amide [68-12-2] (33). The idealized chemical stmcture for a 2 1 BMI—aminobenzoic hydrazide resin is as follows ... 

Bismaleimide Resins via EI E Reaction. The copolymerization of a BMI with o,o -diallylbisphenol A [1745-89-7] (DABA) is a resia coacept that has beea widely accepted by the iadustry because BMI—DABA bleads are tacky soHds at room temperature and therefore provide all the desired properties ia prepregs, such as drape and tack, similar to epoxies. Crystalline BMI can easily be blended with DABA, which is a high viscosity fluid at room temperature. Upon heating BMI—DABA blends copolymerize via complex ENE and Diels-Alder reactions as outlined ia Eigure 8. 

Commercial BMI Resins. Since the late 1960s, bismaleimide resins have been commercially available. The first company in the marketplace was Rhc ne Poulenc Chimie, Erance. Several others, Technochemie, Germany CIBA GEIGY, Switzerland DSM, The Netherlands, BASE, West Germany Mitsubishi Gas Chemicals and MitsuiToatsu, both of Japan Reichhold and Polyorganics from the United States and Shell Chemical Company, United States (through the acquisition of Technochemie by Deutsche Shell AG), followed. Some of them lost interest in this speciaUty market sector. Table 13 indicates the BMI resins available at the end of 1992. No reference is made to prepreg systems available from various sources. A complete Hst of available products and information on any particular material should be obtained from the suppHers. 

Bismaleimides - Bismaleimides resins were first introduced into the market in the early 1970 s. As with other resin systems, there are many variations of bismaleimides. The Kermid and Kinel bismaleimide products as marketed in the U. S. by Rhodia are representative examples. Bismaleimide chemistry is represented in Eq. 3 where curing can be accomplished thermally through the unsaturation in the maleimide or by way of the Michael Reaction where an appropriate curing agent such as aromatic diamine adds across the activated double bond. In most instances, a combination of curing thermally through the double bond and via an aromatic diamine is used in actual practice. Bismaleimides are frequently formulated... 

Matrix materials for commercial composites are mainly liquid thermosetting resins such as polyesters, vinyl esters, epoxy resins, and bismaleimide resins. Thermoplastic composites are made from polyamides, polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polysulfone, polyetherim-ide (PEI), and polyamide-imide (PAI). 

The maleimide group can undergo a variety of chemical reactions. The reactivity of the double bond is a consequence of the electron withdrawing nature of the two adjacent carbonyl groups which create a very electron-deficient double bond, and therefore is susceptible to homo- and copolymerizations. Such polymerizations may be induced by free radicals or anions. Nucleophiles such as primary and secondary amines, phenates, thiophenates, carboxylates, etc. may react via the classical Michael addition mechanism. The maleimide group furthermore is a very reactive dienophile and can therefore be employed in a variety of Diels Alder reactions. Bisdienes such as divinylbenzene, bis(vinylbenzyl) compounds, bis(propenylphenoxy) compounds and bis(benzocyclobutenes) are very attractive Diels Alder comonomers and therefore some are used as constituents for BMI resin formulations. An important chemical reaction of the maleimide group is the ENE reaction with allylphenyl compounds. The most attractive comonomer of this family is DABA particularly when tough bismaleimide resins are desired. 

Within this section the most important chemical concepts for bismaleimide resins are discussed. Attention is paid to the classical approaches and also to more recent developments. 

The most important application for bismaleimide resin is multilayer boards. The development in this area requires resins with low dielectric constants. It is well documented in the literature that fluorine containing linear polyimides show lower dielectric constants vis a vis their non-fluorinated counterparts. Recently, Hitachi Research Laboratory, Japan, reported the thermal and dielectric behaviour of fluorine-containing bismaleimides (29). The chemical structures of the fluorinated BMIs investigated are provided in Fig. 6. The non-fluorinated four aromatic rings containing BMI, 4,4 -bis(p-maleimidophenoxyphenyl) propane, was tested in comparison. 

A new series of functionalized poly(arylene ether ketone)s and their use as modifiers for bismaleimide resins has recently been published (96). In contrast with the former work in this area, the functional groups are not terminal but randomly distributed along the backbone of the poly(arylene ether ketone). The synthesis involves the reaction of 4,4 -difluorobenzophenone and the potassium bisphenates of bisphenol-A and 2,2 -bis(3-allyl-4-hydroxyphenyl) hexafluoro-isopropane or mixtures thereof in DMAc at 155 °C as outlined in Fig. 31. The concentration of the o,o -diallylbisphenol employed in the synthesis determines the concentration of functional propenyl groups. 

Chemical functionalization of the thermoplastics was found to improve toughness without such detractions. High-molecular-weight resins based on amine-terminated PES oligomers or chain extension of bismaleimide resin with the same amine-terminated PES were found to have improved fracture resistance and reduced thermal shrinkage.14 Also a mechanism was found to toughen cyanate esters by incorporating epoxy resins, which can react with the ester.15... 

Stenzenberger, K.D. Komig, P. New functionalized poly(aryleneetherketones) and their use as modifiers for bismaleimide resins. High Perform. Polym. 1993, 5, 123-137. 

Similar hybrid thermosets consisting of bismaleimide resins mixed with bisphenol A dicyanate ester have been commercially available (BT resin, Mitsubishi gas chemical). The presence of cross-linked triazine ether network in the matrix of bismaleimide crosslinked network is believed to improve the toughness, reduce the moisture sensitivity and improve the dielectric properties of the bismaleimide thermoset without a sacrifice in heat resistance. 

Don Doimellan, T. M., Roylance, D. Relationships in A bismaleimide resin system. Part II Thermomechanical properties. Polym. Eng. Sci. 32 (1992) 415-420. 

Iij lijima, T., Nishina, T., Fukuda, W., Tomoi, M. Modification of bismaleimide resin by poly (phthaloyl diphenyl ether) and the related copolymers. J. Appl. Polym. Sci. 67 (1998) 769-780. 

Wei Wei, G. X., Sue, H.-J. Fracture mechanisms in preformed polyphenylene oxide particle-modified bismaleimide resins. J. Appl. Polym. Sci. 74 (1999) 2539-2545. 

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