Bismaleimide adhesives

Formulations based on bismaleimide offer the highest temperature resistance and, hence, service temperatures of all the commonly encountered structural adhesives. However, at present, their use is rarely encountered. Those which are used are virtually all in aero engine structures. 

However, the joint strike fighter (JSF) will require new engines with new design concepts and here, because of temperature demands, Rolls Royce are evaluating three novel BMI adhesive systems. 

Of all the current civil engines. Rolls Royce s Trent 7(X) does have high temperature requirements. The IFS of the thrust reversers has to operate for considerable periods of time at elevated temperatures ( 140-150°C). The component manufacturers, Hurel-Hispano, believe that this is asking too much of an epoxy adhesive and hence a Cytec-Fiberite BMI film adhesive (FM-2550) is used to bond this structure. Here the BMI adhesive is reticulated onto phosphoric acid anodised aluminium honeycomb. The core is then bonded directly onto pre-cured carbon-reinforced BMI laminates to form a sandwich structure, one of the skins being perforated to produce an acoustic panel , which helps reduce engine noise. 

Hexcel Composites HP 655 is also qualified by Airbus Industries for use in structures either in or adjacent to the Trent 900 engines, which are to power the Airbus A. 3 80. 

Bismaleimide and imide structural adhesives for the aerospace industry are available [33] from Cytec-Fiberite, Hexcel Composites, Henkel Corporation and Monsanto. 

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PVF-P adhesives have been used at de Havilland in Hatfield, England since 1936 for the manufacture of air screws [199]. Aero Research Ltd. of Duxford, England, which became CIBA (A.R.L.), originally developed them ([200], pp. 76-83). Currently, the Redux business and trademark belongs to the Hexcel Composites Ltd. and is applied to the original polyvinyl-phenolic alloys as well as epoxies and bismaleimide adhesives that give structural performance at even higher temperatures [201]. 

Butylated PVP PVP/eicosene copolymer PVP/hexadecene copolymer adhesive, cotton Styrene/PVP copolymer adhesive, defense Bismaleimide adhesive, denture Karaya (Sterculia urens) gum adhesive, drums Potassium silicate adhesive, EB... 

Politi, R.E., Recent developments in polyimide and bismaleimide adhesives in T.T. Serafini (Ed.), High Temperature Polymer Matrix Composites (pp. 123-134). Noyes Data Corporation, 1987. 

To illustrate the use of the finite element method, a series of single lap joints was analysed using the following combinations of adherend titanium-titanium, titanium-composite, composite-composite, and aluminium-aluminium. For each adherend combination, both an epoxy and a bismaleimide adhesive were analysed and each joint was subjected to four different test temperatures —55°C, 20°C, 130° and 180°C. In all, therefore, 32 different cases of single lap joints were considered. The thicknesses of the adherends were 2 mm for the composite, 1.6 mm for the aluminium and 1.2 mm for the titanium. The joint width was 25 mm, the length was 12.5 mm, and the bondline thickness was 0.1 mm. 

The second adhesive was a bismaleimide adhesive, HP655, manufactured by Hexcel. As can be seen from Fig. 2, this is a relatively brittle material with little, if any, plastic deformation prior to failure. However, it maintains better mechanical properties over a wide range of temperatures and is specifically designed for high-temperature applications. The values of elastic moduli for the HP655 at the different test temperatures are given in Table 2. 

Because of this continued emphasis on adhesive bonding technology development over the years, the airframes of modem front-line aircraft such as the B-2 bomber and the F-117 and F-22 fighters are largely structurally bonded advanced composites. They tend to be comprised of materials that are more advanced (expensive) than commercial aircraft such as carbon and boron fiber reinforcements with cyanate esters, bismaleimides, polyimides or other high-temperature resin matrices and adhesives. 

Interfacial adhesion and, thereby, compatibility can be enhanced by the selective crosslinking reaction in polymer blends. Inoue and Suzuki [26] reported the properties of blends dynamically crosslinked PP-EPDM blends. The crosslinking agent was yV,N -/w-phenylene-bismaleimide - poly(2,2,4 - trimethyl - 1,2-dihydroquino -line) system. Increase in interfacial adhesion leads to... 

BMI polymers have glass transition temperatures in excess of 260°C and continuous-use temperatures of 200-230°C. BMI polymers lend themselves to processing by the same techniques used for epoxy polymers. They are finding applications in high-performance structural composites and adhesives (e.g., for aircraft, aerospace, and defense applications) used at tem-peratrues beyond the 150-180°C range for the epoxies. Bisnadimide (BNI) polymers are similar materials based on bisnadimides instead of bismaleimides. 

Parker et al. (30) reported the synthesis of phosphorous containing bismaleimides and demonstrated their outstanding non-flammability characteristics. Graphite fabric composites prepared from such P-containing BMI as a matrix resin show a LOI of 100 and an anaerobic char yield of 88% at 700 °C. Other P-containing BMI have recently been synthesized (31) for example, bis(3-maleimidophenoxy-4-phenyl)phenyl phosphine oxide (Figure 8) has been tested as a composite matrix resin with the aim of improving the fibre/resin interfacial adhesion. 

JP 62246978 (Japanese) 1987 Heat-resistant adhesives containing siloxanes and imide-containing resins Shin-Etsu Chemical Industry Co. Ltd., Japan S Ueno, N Nakanishi, S Hoshida Adhesives showed good adhesion and flexibility useful in the preparation of flexible laminates Resin was prepared from the reaction product of bismaleimides, diamines, amino-terminated siloxanes and a bisphenol A cyanate adduct. The adhesive formulation was used on polyimide films... 

Many anaerobie adhesives and sealants may require a relatively low strength so that the eomponents can be disassembled for repair or replacement. Many liquid plasticizers have been used for this purpose [62], but the use of a low-molecular-weight polyester has been found to be advantageous [63]. The toughness properties of anaerobic adhesives can be enhanced by the addition of a reactive elastomer [64]. The heat resistance of anaerobic adhesives and sealants can be enhanced by the addition of a bismaleimide... 

Epoxies are the most widely used adhesives in electronics assembly, followed by silicones and polyimides. The use ofthese adhesive types, along with the more specialized types such as cyanate esters, bismaleimides, and modified cyclo-olefin thermosets, is expected to increase as the total production of electronic circuits and hardware increases. In recent years, the total value of electronic components has increased tremendously from 59 billion in 1989 to an estimated 215 billion in 2003. It is predicted that the cumulative growth will be 5% to 10% per year. Adhesives for electronics... 

Bismaleimide paste adhesive Boron nitride QMl 536 HT Loetite 0.9... 

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