Benzoxazine Copolymers with Mono- and Difunctional Epoxy Active Diluents with Enhanced Tackiness and Reduced Viscosity

The influence of epoxy active diluents, 1,4-butanediol diglycidyl ether (BD) and furfuryl glycidyl ether (FUR), in the mixtures with benzoxazine monomer based on bisphenol A, formaldehyde and m-toluidine (BA-mt), on the properties of a matrix was disclosed in this work. Resins were modified to achieve good tackiness at room temperature and reduced viscosity. The influence of mono- and difunctional modifiers on the process of curing was studied by way of differential scanning calorimetry and oscillatory rheology. The addition of BD and FUR shifted the curing peak to higher temperatures and significantly reduced viscosity. Preferable tackiness at ambient temperature was achieved with 10 phr of epoxy components in mixtures. However, cured blends with difunctional epoxy BD had an advantage over monofunctional FUR in enhanced tensile strength with remaining glass transition temperature at the level of neat benzoxazine (217 °C).

METHODS OF CHEMICAL MODIFICATION OF EPOXY OLIGOMERS (review)

This paper is devoted to one of the most pressing problems of modern non – metallic materials science-chemical modification of thermosetting systems based on epoxy oligomers with active diluents and bismaleimides: polymer binders for reinforced plastics, adhesives, compounds, sealants, and protective paint coatings. Based on the analysis of domestic and foreign scientific literature, as well as patents for inventions, a conclusion was made about the prospects for further research in this direction. The use of these types of modifiers can increase the chemical resistance, crack resistance, strength, impact strength, heat resistance and other valuable properties of polymer composite materials (PCM) based on an epoxy polymer matrix.

Investigation of surface tension and contact angles for effective polymer binders based on epoxy oligomers and active diluents

Objectives. This study focused on the quantification of the surface tension and the static and dynamic contact angles of epoxy oligomers, active diluents, and their mixtures of various compositions at different temperatures. The active diluents were aliphatic compounds based on glycidyl ethers, namely laproxides and a laprolate of different structure, functionality, molecular weight, and viscosity. Moreover, the preparation of effective polymer binders (matrices) for composites was explored.Methods. In this study, the epoxy oligomers ED-20 and DER-330, laproxides 201B, DEG-1, E-181, and 703, laprolate 301, and their mixtures in various compositions were investigated. Their surface tension and the static and dynamic contact angles were determined by the Wilhelmy plate and ring methods on a semiautomatic tensiometer at different temperatures (20–60 °C). The static contact angle was measured on a thin aluminum borosilicate glass plate, and the dynamic contact angles were determined using an installation for measuring surface tension developed by NPO Stekloplastik.Results. The surface tension and static and dynamic contact angles were obtained for all epoxy oligomers and active diluents, as well as for their mixtures at 20–60 °C. For binders based on systems of epoxy oligomers and active diluents, the impregnation rate of fiber reinforcement was also calculated. The introduction of laproxides or laprolates into the epoxy oligomers led to a decrease in surface tension and contact angles, while the increase in temperature increased the impregnation rate by 10–20 times.Conclusions. The temperature increase from 20 to 60 °C resulted in a decrease in the surface tension of mixed systems of epoxy oligomers and active diluents by almost two times. In addition, the contact angles changed by only 4°–7°, while the impregnation was significantly improved and the corresponding rate increased by 10–20 times.

THE INFLUENCE OF DILUENTS ON THE KINETICS OF VOLUME SHRINKAGE AND STRESS UPON CURING OF EPOXY OLIGOMERS

It is known that for decrease in viscosity polymeric binding on the basis of epoxy oligomers in their composition injecting solvents of the different nature and thermodynamic compatibility. In this paper the dependences describing influence on shrinkage, kinetics of increase and maximum level of strains from diluents content and temperature of curing of epoxy oligomers are established. Introduction about 20 % of the active diluents (DEG-1 and SO-3) in system on the basis of epoxy oligomers leads to decrease in viscosity in ~3 times, to improvement of imbibition quality of fibrous fillers, increase of volume contraction (on ~2.5. %) and decrease in residual stresses in ~6 times as a result of increase of mobility of pieces of a polymeric chain in a three-dimensional grid, and also to decrease in glass transition temperature no more than ~20°C.

Effect of different photoinitiators on the properties of UV-cured electromagnetic shielding composites

A series of UV-cured electromagnetic shielding composites (UV-EMSC) containing different content of graphene oxide (GO) were prepared with oligomer, acrylate active diluents and different photoinitiators (Darocur 1173, Irgacure 184 or Irgacure 651). To fabricate conductive oligomer with low resistivity, polyurethane-acrylate (PUA) was used as the polymer matrix to help construct two-dimensional conductive networks consisting of GO. For forming conductive network structure, the surface functional groups (-OH, -COOH) of GO served as slightly conductive particles bonded with -NCO from the chain of polyurethane. The UV-EMSC exhibited a low resistivity of approximately 402 Ω·cm and an outstanding enhanced electrical conductivity of 249 mS/m at a GO content of 0.0200%. The effects of different photoinitiators on the properties of UV-cured films were investigated. The results indicate that the prepared UV-EMSC has great potential applications in different regions, such as in coatings of electronic, electrical, communications, plastic coatings and wood finishes.