Zixuan Lei,Jingru Ji,Qianqiu Wu,Junjie Zhang,Yixun Wang,Xinli Jing,Yuhong Liu
Easily oxidized group and rigid structure of phenolic resin (PR) network can result in brittleness and low char yield at high temperatures, which limits the widespread applications of PR in harsh environment. Whilst organic-inorganic hybrid material , such as POSS-containing material was introduced to enhance PR, the microstructure and the thermo-mechanical properties of the hybrid material modified PR are not well understood. Therefore, in the work, a novel organic-inorganic hybrid networks (ENH) were prepared with epoxy-polyhedral oligomeric silsesquioxane (EPOSS) modified novolac phenolic resin (EN) and hexamethylenetetramine (HMTA) to further clarify the curing behavior and its relation to microstructure and the resulting thermal-mechanical properties. Here, the curing characteristics of ENH were discussed by usinag advanced isoconversional method and Fourier transform infrared spectroscopy (FTIR). It was revealed that a diversity of crosslinking networks was exhibited after curing ENH, including EPOSS-NR crosslinked, tethered structure, and self-polymerized structure of EPOSS as well as NH networks. When the substitution degree of EPOSS is relatively low, EPOSS serves as a junction point to further improve the crosslinking density of ENH networks, leading to better thermo-mechanical properties, thermal stability and tensile property as well as lower dielectric properties . However, as the self-polymerization of EPOSS increased, the NH network was dramatically disrupted and the thermo-mechanical properties, thermal stability and tensile property of ENH were deteriorated.
Xiaoxiao Ji,Jinhui Wang,Zhiming Wang,Bowei Mao,Yizhong Cao,Yanjun Xie,Yutao Yan
Bamboo-based composite, being an eco-friendly green material, has garnered widespread utilization across diverse sectors including construction and domestic appliances owing to its impressive strength, innate aesthetic appeal, and wear resistance. However, it tends to crack at bonding interface between bamboo and the brittle resin adhesive due to stress concentration, reducing its mechanical properties and lifespan. To address this issue, the epoxy-based polyhedral oligomeric silsesquioxane (POSS) was incorporated to modify the phenol-formaldehyde (PF) resin and improve the interfacial bonding strength. And the results showed that the incorporation of 5% epoxy-POSS could markedly increase the impact and flexural strength of the modified PF resin by 75.7% and 27.6%, respectively, in contrast to the original PF resin. Moreover, the dry and wet shear strength of bamboo-PF composites bonded by the POSS modified PF resin adhesive was also apparently improved by 17.03% and 28.55%, respectively. The increased toughness and bonding strength were mainly attributed to the nano-effect of POSS and good compatibility and cross-linking reaction with the PF resin, which helped dissipate energy and avoid stress concentration within the PF resin and at the bonding interface. This study aims to address the cracking problem of bamboo-based composites and extend their longevity in architectural and domestic applications. Highlights Epoxy-POSS disperse well in PF resin due to its unique multi-epoxy structure. Epoxy-POSS can react with PF resin and effectively improve its toughness. Nano-effect and cross-linking effect enable dissipate energy and disperses stress. Modification increased bonding strength and decreased interfacial cracking.
It is well known that the interfacial region between the polymeric matrix and nanofiller plays a very important role in tailoring the electrical insulation properties of nanocomposite. In this study two type of polyhedral-oligomeric-silsesquioxane (POSS) are doped into epoxy (EP) to investigate the tailoring of interfacial traps that can limit the mobility of charge carriers and enhance the breakdown strength . Incorporating acryloxypropyl POSS (AP-POSS) to EP matrix improves the breakdown strength than that of pristine EP and octaphenyl POSS (OP-POSS). The molecular simulation and experiments identifies that the compatibility between EP/POSS and trap depth is dependent on the interfacial interaction energy and crosslinking density. The side groups of AP-POSS has large number of localized energy states and higher electron affinity ( E A ) that can tailor deeper traps and restrain the mobility of electrons in EP/AP-POSS. The interfacial compatibility of POSS side groups with EP tune the interfacial traps and dielectric characteristics.
危险品化学品经营许可证（带存储）