Experimental investigation of cracking behaviors of ductile and brittle rock-like materials

The cracking characteristics of ductile rocks were studied by similar materials with sand, barite, epoxide resin, polyamide, silicone rubber and alcohol, while the cracking characteristics of brittle rocks were investigated by similar material with sand, barite, rosin and alcohol. In this paper, to enhance the application range of the rock-like materials in the field of geotechnical engineering model tests, the values of the elastic modulus and the compressive strength of the artificial rock-like materials are changed in a wide range by adjusting the amount of cementitious materials (epoxide resin, polyamide, rosin, etc). The elastic modulus, compressive strength and cracking characteristics were obtained from the complete axial stress–strain curves of the specimens made of similar materials, which were cast using the different mixture ratios. These experimental data can provide quantitative investigation on mixture ratios of similar materials of rocks to model the geotechnical engineering. Furthermore, the effect of mixture ratios on mechanical properties and crack propagation pattern of specimens were also investigated by the specimens with pre-existing flaws under uniaxial compressive tests

Radical-induced cationic frontal polymerisation for prepreg technology

In this study, a new type of prepreg technology has been established using a dual curing system consisting of 1,6-hexanediol diacrylate (HDDA) and frontally polymerisable components based on the epoxide resin. The study of the polymerisation of HDDA revealed (tert-butylcyclohexyl)peroxydicarbonate (BCPC) as the most suitable radical thermal initiator. The presence of BCPC resulted in a fast radical polymerisation of HDDA and no cationic ring-opening reaction of the epoxy, which was observed by monitoring the double bond and epoxy group conversion in real time-NIR rheology measurement. The formed prepreg can subsequently be cured by radical-induced cationic frontal polymerisation of the epoxy resin. Effects of HDDA amount on the radical polymerisation, stiffness of the gel, frontal parameters and thermal mechanical properties of final polymers were investigated. With 10 wt% HDDA, the formed prepreg has very good storage stability, which was proved by monitoring the epoxy group conversion during 4 months of storage at 50 °C while still a stable front can be obtained. Furthermore, the RICFP-prepregs with different fibre contents were prepared and polymerised by RICFP. Then, a snowflake composite was successfully produced using RICFP-prepreg. Graphic abstract

Synthesis of Hydroxy Aminimide from Unsymmetric Dimethyl Hydrazine Through One Pot Reaction: A New Nanoscale Access for the Reutilization of Unsymmetrical Dimethyl Hydrazine

In this paper, two new kinds of hydroxy aminimide were nanoscale synthesized utilizing Unsymmetrical dimethyl hydrazine (UDMH) and economical carboxylic acid methyl ester was analyzed through one pot reaction. The reaction conditions were examined and the best reaction temperature was 20 °C with the reaction time of 60 h, achieving a highest yield of 83.21% for the two aminimides. Structures of the final products are characterized by GC-MS, FT-IR and NMR. Then the thermal stability of the aminimide is tested and it is found that the decomposition temperature of one aminimide is 65.20 °C, which is better than any other aminimides used for the latent curing agent of epoxide resin.

Epoxy composition on the basis of triestertrisulfoimide saccharin-6-carboxylic acid

By the interaction of the previously synthesized 2-hydroxypropyl-1,3-bis-estersulfoimide of saccharin-6-carboxylyc acid with alkyl esters of sulfimide of the same acid triestertrisulfoimide saccharin-6-carboxylic acid has been obtained. The composition and structure of the synthesized compound has been confirmed by data of elemental analysis and IR-spectroscopy. The obtained product has been as a curing agent - plasticizer for industrial epoxide resin ED-20. It has been established that the triestertrisulfoimide of saccharin-6-carboxylic acidis the effective curing agent — plasticizer of epoxide resin ED-20. The curing prosses of composition was studied by a method of differential thermal analysis on derivatograph of system “Paulik-Paulik-Erdey”. It has been revealed according to the obtained data that the synthesized triestertrisulfoimide of saccharin-6-carboxylic acidis combined well with epoxide resin ED-20 but it is cured at hard temperature regime. It has been shown that in the introduction of accelerator UP 606/2 into epoxy composition the curing temperature of composition is decreased, but its thermal, physical -mechanical values are increased.

Modification of ED-20 epoxy resin by cyclopropane-containing compounds

The modification process of ED-20 epoxy resin by synthesized cyclopropane-containing compounds has been considered. It has been shown that their introduction improves considerably physical-mechanical, heat-physical and thermal indices of the compositions based on the ED-20 epoxide resin.