Maleimide resin

In the narrow sense, bis-maleimide resin means the thermosetting resin eom-posed of the bis-maleimide of methylene dianiline (BMI, bis(4-maleimidophenyl)-methane) and methylene dianiline (MDA, bis(4-aminophenyl)methane) (Fig. 1). Beeause of the addition meehanism, the resin is eured without elimination, whieh is a eharacteristic of this resin. Bis-maleimide resin is used as a thermally stable matrix up to 204°C (400 F) whieh typical epoxy resins may not normally be used. However, in spite of having an imide structure, bis-maleimides are classified as being moderately thermally stable resins. The aliphatic structure of the resin is not stable for long periods above 232°C (450°F.) If a highly aromatic thermally stable thermosetting resin is necessary, acetylene end-capped aromatic imide-based oligomers should be used. 

Bis-maleimide resins composed of BMI and diamines have been reported in the early 1960s in the patent literature. Since that time, a number of patents have appeared describing improvements in their properties and uses [3]. Although many bis-maleimide resins are commercially developed, relatively few reports of their use as adhesives are to be found in scientific journals [4-10]. Improvements of maleimide resins are mirrored in the improvements of thermosetting polyimides. For example, the method of in situ polymerization of monomer reactants (PMR method) was developed [6]. 

A typical maleimide resin is synthesized by the Michael addition of MDA and BMI (Fig. 4). If the stoichiometrically equal amounts of MDA and BMI are added into the reaction solvent under controlled temperature, linear, high molecular weight polyaminoimide (PAI) results. To obtain crosslinkable oligomer (pre-polymer) with maleimide end groups, a calculated 1.1-1.8 times an excess... 

One can vary the chemical composition of the bis-maleimide system by replacing tbe MDA with other diamines. The nature of the resin is not that different from that using MDA because the resins are so highly crosslinked. Based upon availability, ease of use and cost, BMI and MDA are most often used. However, one commercial maleimide resin, Techocbemie s Compimide H795 has an original structure. As shown in Fig. 8, it is composed of BMI and / -aminobenzoyl hydrazide [10]. 

Fig. 5. Curing mechanism of a maleimide resin via Michael addition.

To improve upon their inherent brittleness, bis-maleimide resins are often mixed with other eompounds and materials. Glass fabrie and earbon fiber fabrie are immersed in uncured maleimide resin and plied are layed up, followed by... 

As already mentioned, aromatie polymers are thermally stable but aliphatic portions of them are not as thermally stable. Typical maleimide resins have aliphatic units. This is inevitable because the Michael addition was used to prepare the maleimide-based oligomers. On the other hand, if an adhesive consists of a linear thermoplastic polymer, it is not usable at temperatures above its softening temperature. Introdueing chemical crosslinking is one way to prevent thermal weakening of a material. 

Okumoto, S., Yamabe, S. A theoretical study of curing reactions of maleimide resins through Michael additions of amines. J. Org. Chem. 2000, 65, 1544-1548. 

Poly(isoimide)s received interest as intermediates for Pis, because the ring closure of the poly(amic acid) runs faster with carbodiimides, e.g., di-cyclohexylcarbodiimide, in comparison to acetic anhydride. " However, the use of a carbodiimide yields the isoimide moiety exclusively, whereas acetic anhydride yields the ordinary imide. However, by the treatment with suitable isomerizing agents, such as 1-hydroxyhenzotriazole, or 3-hydroxy-l,2,3-benzotriazin-4-one, the isoimide can he converted to the imide. This technique is suitable for the synthesis of Uquid thermosetting maleimide resins. 

The most common thermosetting PI resins are bis(maleimide) resins. A wide variety of these resins is known. Commercially available bismale-imide thermoset compositions are well known for their high modulus, and excellent resistance to thermal degradation. 

When considering the use of MA in condensation polymers, it is automatic to think of unsaturated polyesters. In fact, the demand for MA is keyed primarily to the growth of these resins. In 1980, about 172 MM lb of MA were used to produce polyester resins in the United States.This represented approximately 52% of the 330 MM lb of MA demand in the United States in 1980 (see Sec. 1.4.1). MA is also very useful in other condensation polymers, including about 6 MM lb in alkyd resins. The value of using MA to prepare, crosslink, and/or modify condensation and addition polymers is discussed in this chapter. In recent times, the synthesis of maleinated vinyl esters and maleimide resins have had significant study. Because of this interest, we also give some attention to the use of MA in vinyl ester and maleimide technology. 

Paracyclophane 93, 97, 101-102 Percolation theory 140-142 Phenol formaldehyd resins 72-75, 77, 78 Phenol maleimide resins 75 Phenolic triazine 87 Piezoelectricity 159-160 Poisson ratio 153, 179 Polyacrylates 19, 21, 22, 23 Polyamide, aromatic, linear 2, 30, 31, 127, 170-174, 184... 

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