PREPARATION AND STUDY OF THE PROPERTIES OF THE COPOLYMER OF CYCLIC UNSATURATED BISMALEIMIDE WITH STYRENE

The paper is devoted to the study of regularities of radical copolymerization reactions of unsaturated cyclic N,N'-bisimides (M1) with styrene (M2), the study of dependence of copolymerization reaction rate, composition of obtained copolymers, composition and estimated molecular weight on the composition of the initial monomer mixture. With the increase of bismaleimide amount in the initial monomer mixture a decrease of copolymerization reaction yield and molecular weight of the obtained copolymers was observed. This fact can be explained by active participation of bismaleimide in chain transfer in radical copolymerization reaction. The composition of the obtained copolymers in all cases is rich in styrene links

Nanostructured Hydrogel Dressings on Base of Crosslinked Polyvinylpyrrolidone for Biomedical Application

Hydrogel dressings for biomedical application were obtained by γ-irradiation of poly-N-vinipirrolidon (PVP), agar-agar, polyethylene glycol and silver nitrate solution. Influence of irradiation doses (range from 25 kGy to 75 kGy), silver nitrate concentration and PVP concentration in initial monomer mixture on properties of obtained material were investigated. Presence and distribution of silver nanoparticles in obtained bandages is confirmed by optical microscopy and atomic force spectroscopy. Antimicrobial activity study in vitro showed antimicrobial activity, flexibility, high sorption capacity to water and biological fluids.

Effect of Resin Formulation on Thermoset Viscoelasticity

Viscoelastic relaxation curves of thermoset resins may change considerably for relatively small changes in properties of the initial monomer mixture or final conversion level. In order to be able to predict the effect of such changes, a model is proposed which relates the properties of the initial monomer mixture such as the functionality, mixing ratio, and conversion level to changes in the relaxation curves. It basically consists of two parts. Firstly, the crosslink density is calculated based on the exact composition of the monomer mixture and, secondly, the effect of this crosslink density on the position of the glass transition and the rubbery modulus was calculated. The model was tested with a series of Novolac epoxies in which the functionality, mixing ratio, and conversion level were varied systematically. It turned out that changes in the relaxation curves due to variations in conversion level could be predicted quite accurately from the shape and shift factor of the fully cured mastercurve. The agreement between relaxation curve predictions for the series with changing functionality and mixing ratio was only moderate, which was ascribed to errors in the prediction of correct values for the crosslink density.