Electron beam curing kinetics of reactive diluent containing bismaleimide
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Electron-Beam (E-Beam) curing kinetics of 4,4'-Bismaleimidodiphenylmethane (BMPM) / BMI-1,3-tolyl / o,o'-diallylbisphenol A (DABPA) based bismaleimide (BMI) systems and their mixing with the reactive diluent N-vinylpyrrolidone (NVP), are investigated to elucidate how temperature, electron-beam dosage and dose rate, and diluent concentration affect the cure extent. The effect of free radical initiators on the cure reactions is also studied. It is found that low intensity E-Beam doses cannot cause the polymerization of BMI. High intensity E-Beam exposures give high reaction conversion due to high temperature rise, which induces thermal curing. It is shown that NVP is a good reactive diluent for BMI. BMI/NVP can be initiated easily by low intensity E-Beam without thermal curing. FT-IR studies indicate that about 70% of the reaction is complete for BMI/NVP with 200kGy dosage exposure at 10kGy per pass. The sample temperature only reaches about 75C. Free radical initiator, dicumyl peroxide, can accelerate the reaction rate at the beginning of E-Beam exposure, but does not affect final reaction conversion. The increase of the concentration of NVP in the BMI/NVP systems increases the reactive conversions almost linearly. The dilution and activation of NVP in BMI make the BMI reaction more complete under E-Beam radiation.