BMI systems

Previous BCB/BMI resin studies have demonstrated that the addition of 40X to 60X BCB to a BMI results in a resin with thermal stability dramatically improved over that of the BMI itself The 1 1 siolar ratio BCB/BMI system used in this study has exhibited the retention of thermal mechanical properties at elevated tesiperatures as well. 

The breakthrough with respect to application as tacky autoclaveable pre-preg was achieved by US Polymeric (now British Petroleum Chemicals) with their V378A BMI system (11). This system was used to build the delta wings of General Dynamic s F16XL demonstrator combat aircraft (12) and found application for parts of the Me Donnell Douglas AV8-B vertical take-off aircraft (13). 

There s one major problem with the BMI system. What about an athletic man or woman Muscle weighs more than fat tissue. A football player who stands 6 feet 1 inch and weighs 204 pounds may be solid muscle with very little fat. He would scarcely be thought of as overweight, despite a BMI of 27 that would put him into that classification. A bodybuilder might even weigh 227 at that same height, but he wouldn t be called obese. 

Adhesives in electrical applications involve laminates with metal substrates and often have to withstand high temperatures. The laminates are often fairly thin and reasonably flexible therefore fixed arm and T-peel procedures can be helpful in measuring their adhesive strength. For example, a BMI system was bound to copper foil of thickness 25 pm. Some fixed arm (where the base plate formed a bond with aluminium) and T-peel results for this system are summarised in Table 2 on 15 mm width specimens of length 150 mm. 

A controUed-flow, tough BMI system (for intermediate modulus fibers) for prepreg uses... 

A high-Tg hot/ wet resistant resin A toughened high-Tg BMI formulation A tough BMI system A BMI thermoset with thermoplatic-like toughness... 

Xanthos [30] has reported on the effects of BMI in wood fiber/PP composites. The temperatures needed for activation of the BMI system led to degradation of the... 

V398 A tough BMI system BP Chemicals (Hitco) Inc., Anaheim,... 

The held is still in its infancy however, several basic principles have emerged from these and other early experiments. A crucial requirement in BCI function, for example, is for the reading device to obtain suf-hcient information for a particular task. Another observation refers to the transparency of action in brain-machine interface (BMI) systems Upon reaching prohciency, the action follows the thought, with no awareness of intermediate neural events. 

Another thorough study shows that E-beam exposure cannot propagate the polymerization of BMI systems until the temperature goes up to 100°C. Higher intensity E-beam can give high reaction conversion of BMI... 

Oligomers end-capped with maleimide rings, which are known as bismaleimide (BMI) resins, exhibit thermal stability intermediate between epoxies and poly-imides. BMI systems are mainly used to fabricate structural composites capable of sustaining temperatures up to 230°C. Specific versions, such as American Cyanamid FM 32 and Ciba-Geigy Kerimid 601 have been developed to prepare adhesive compositions. Fig. 17 displays a typical constitutive unit of various commercial BMI resins based on bismaleimide 38, prepared from maleic anhydride 37 and 4,4 -methylenebisbenzeneamine (MDA) 34. 

The few remaining bonding applications generally use structural paste adhesives to produce, essentially, non-structural bonds (Grade III rating). Apart from the BMI systems, mentioned below, by far the greatest proportion of these adhesives utilise epoxy resin chemistry. 

LTP) in hippocampal slices (89,90). LTP is believed to be a critical step in memory acquisition, and agents that possess the abiUty to augment this process in vivo are expected to be of benefit in memory enhancement. However, this compound has only demonstrated this property in vitro. In addition, because (11) does not appear to affect other neurotransmitter systems, as do other nootropics, the potential of BMY 21502 as a memory-enhancing agent is questionable. 

A number of BMI resias based on this chemistry became commercially available through Rhc ne Poulenc for appHcation ia priated circuit boards and mol ding compounds and Rhc ne Poulenc recognized the potential of bismaleimides as building blocks for temperature-resistant thermoset systems. The basic chemistry, however, was not new, because the Michael addition reaction had been employed by Du Pont to obtain elastomeric reaction products from bismaleimides and Hquid polymeric organic diamines (15). 

The resin system V-378A, mentioned eadier, is a bismaleimide system that has been modified with divinylbenzene to achieve drape and tack in prepreg form. Divinylbenzene-modifted BMI is appreciated because of its outstanding hot—wet environmental resistance and epoxylike cure (18). 

BMI—diviaylben2ene systems cure via a Diels-Alder reaction. 

BMI comonomer (aHylphenols, propenylphenoxy compound) systems are significantly tougher than BMI homopolymers or BM-Michael-addition copolymer systems. BMI may also be toughened through elastomers and thermoplastics. 

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. 

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]. 

Curing System S/MBTS/ZnO/ Stearic Acid BMI/MBTS DCP (40%) DCP/EGDM DCP/Sulfur DCP/HQ... 

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