Investigating the relationship between microstructure and macroscopic properties of epoxy resin (EP) materials for high-voltage insulation at the molecular level can provide theoretical guidance for the synthetic design of EP. Here, using diglycidyl ether (DGEBA) as the resin matrix and methyl tetrahydrophthalic anhydride (MTHPA) as the curing agent, a set of crosslinked EP molecular models at different curing stages were constructed based on the proposed crosslinking method. We studied the influences of crosslinking density on micro-parameters and macro-properties employing molecular dynamics (MD) simulations. The results indicate that crosslinking of DGEBA/MTHPA is a contraction and exothermic process. The structural parameters and macroscopic properties are closely related to the degree of crosslinking. With the increase of crosslinking density, the mean square displacement (MSD) of the system decreases, and the segment motion in the models is weakened gradually, while, the fractional free volume (FFV) first decreases and then increases. In addition, the thermal and mechanical properties of DGEBA/MTHPA have a significant dependence on the crosslinking density. Increasing crosslinking density can improve the glass transition temperature (Tg), reduce the coefficient of thermal expansion (CTE), and enhances the static mechanical properties of DGEBA/MTHPA system. Furthermore, the relationship between microparameters and properties has been fully investigated. Free volume is an important factor that causes thermal expansion of DGEBA/MTHPA. Moreover, there is a negative correlation between MSD and mechanical moduli. By elevating temperature, the decline in mechanical moduli may be due to the exacerbated thermal motion of the molecules and the increasing MSD values.

is a kind of insulating ceramics with high rigidity and melting point, which has been widely used in the preparation of basin-type insulators [1]. Meanwhile, Al 2 O 3 is one of the most commonly used fillers for composites [2]. Filling nano-Al 2 O 3 can improve the mechanical strength [3-6], thermal stability [7,8], wear resistance [9, 10] and other properties of composite materials, but the improvement of surface insulation performance is not obvious [11,12].

Coral-derived microorganisms have been historically proven to be prolific sources of bioactive secondary metabolites. Twelve benzopyranone and/or xanthone derivatives, including a new benzopyranone with an uncommon carboxyl group at C-8, coniochaetone K (1), were obtained from the Beibu Gulf-derived coral symbiotic fungus Cladosporium halotolerans GXIMD 02502. Their structures were determined by extensive spectroscopic data interpretation and comparison with literature values. The absolute configuration of 1 was accomplished by comparison of specific optical rotation as well as quantum chemical ECD calculations. The in vitro cytotoxicity of compounds 1-12 against two human prostatic cancer cell lines, C4-2B and 22RV1, were evaluated. And compounds 1, 3, 6-8, and 10-11 demonstrated significant cytotoxicity with inhibitions ranging from 55.8% to 82.1% at the concentration of 10 μM.

Epoxy resin samples were processed by one direction and multi-directions polishing methods in this research. The contact angles of the samples, the AC/DC flashover voltage in C4F7N/CO2 gas mixtures and the charge dissipation rate of the polished samples were measured. The results show that the contact angle of the polished epoxy resin sample increases. In the gas mixtures, the surface roughness modification of the epoxy resin under different voltage types is proposed. According to the charge dissipation rate, the development mechanism of creeping flashovers under different voltage is revealed. Different dissipative properties ultimately enhance the creeping discharge voltage of the samples by suppressing electron secondary electron emission. This paper offers a basis for insulation design in the C4F7N/CO2 gas mixture.