The elasticity and yield parameters of PE were determined through a uniaxial tensile experiment.A pipe-soil fi-nite element model under a point load was established to study the point-loading mechanical response of buried PE gas pipes,and the effects of point-loading dimension,pipe internal pressure,and pipe diameter were analyzed.Based on the DFDI(ductile failure damage indicator)model and combined with the finite element simulation results,quantitative dam-age calculations were carried out for PE pipes under a point load.The results indicated that the point load increased the pipe damage when compared to the damage results of the pipe without a point load.The pipe damage shows a great change with a variation of the internal pressure of the pipe.There is little effect on the PE pipe damage with a small change in the pipe diameter,and the damage values under each pipe diameter are relatively close to each other.
Traditional epoxy resins are made from non-renewable fossil resources, which are difficult to reprocess and recycle, and their flammability makes them unsafe during use. In this experiment, an epoxy resin containing Schiff base (TA-VAN-EP) was synthesized successfully with biomass-derived raw materials. This new material not only had favorable mechanical properties but also had good flame retardancy and degradation properties. The chemical structure of TA-VAN-EP was characterized by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (NMR) spectroscopy. Its mechanical properties, thermal stability, flame-retardant properties, and other properties were tested. The results showed that, compared with the pure epoxy resin (EP), the mechanical properties of TA-VAN-EP were significantly improved, and the glass transition temperature (Tg) was increased from 152 degrees C to 190 degrees C. Additionally, TA-VAN-EP reached a V-1 rating during the UL-94 test, and the limited oxygen index (LOI) value increased from 24.7% to 28.4%. Also, the total heat release (THR), smoke production rate (SPR), and total smoke release (TSR) decreased extremely. Moreover, TA-VAN-EP demonstrated good degradation performance under acidic conditions. In conclusion, this work provided a new idea for the production of bio-based flame-retardant epoxy resin with promising degradable abilities and mechanical properties.
Using bisphenol A (BPA) and isophthalaldehyde (IPD) as comonomers, based on open system and solution polycondensation method, phenolic resin was prepared by microwave. The reversible thermochromic composite solution polymerized butadiene styrene rubber film was prepared by resin as chromogenic agent. The resin was tested by gel permeation chromatography, 1 H and 13 C NMR spectrometers, thermogravimetric analyzer, and thermal analyzer, etc. The composite film was tested by thermogravimetric analyzer, thermal analyzer, spectrophotometer, and polarizing microscope, etc. The factors affecting the thermochromic properties, thermal stability, thermal recyclability stability and microscopic morphology of the composite film were studied. The results indicate that BPA-IPD is the 2,6-monosubstituted bisphenol A isophthalaldehyde phenolic resin with M – n of 1.150 × 10 3 g mol –1 and PDI of 1.004. Therefore, the number of monomers in molecular chain containing BPA and IPD are 3 and 3, respectively. When the mass ratio of crystal violet lactone, resin, mixed alcohols (cetyl alcohol and octadecanol) and solution polymerized butadiene styrene rubber is 1 : 1.5 : 30 : 50, i.e., 0.0075 : 0.011 : 0.23(0.14 : 0.09) : 0.38(g), the composite film is obtained by salivation method. The total color difference (Δ E ) of composite film is about 90, and its absorption/scattering color depth difference [Δ( K/S )] values are averagely 20 and 40 at visible light zone of 480– 600 and 600–660 nm at the low temperature region (10–33°С) of phase change during constant speed cooling, respectively. The composite film has good thermal stability and recyclability stability.
Attributed to the merits of excellent material compatibility, healing performance, and long-term stability, the self-healing system based on microencapsulated epoxy-amine chemistry is a potentially practical self-healing system for both structural and functional materials. Herein, based on the microencapsulated epoxy-amine chemistry, a self-healing anticorrosion coating was successfully developed. This self-healing coating system was modeled theoretically to explore the factors that influence the crack filling and the self-healing anticorrosion function. The established quantitative relationship shows that the filling depth of the crack in the coating is proportional to the microcapsule parameters and coating thickness, but inversely proportional to the crack width. Based on the above theoretical model, the effects of various parameters on the anticorrosion performance were experimentally studied. The actual filling of small in-situ cracks (<100 mu m) generated by impact damage was semi-quantitatively characterized using scanning electron microscopy (SEM). The filling behavior is consistent with the theoretical modeling. After being healed at room temperature for 2 days upon impact damage, the formulated self-healing coatings were subjected to accelerated corrosion tests in 10 wt% sodium chloride (NaCl) solution for 2 days to observe their anticorrosion behavior. Compared to the neat epoxy coating, all the formulated self-healing epoxy coatings show evident anticorrosion function. Good self-healing anticorrosion performance was achieved by adding 10.0 wt% microcapsules with a size of 100-150 mu m to the coating with a thickness of 300 mu m. The results of this investigation laid a theoretical and technical foundation for the further development of both the self-healing chemistry and the self-healing anticorrosion coating.
热固性树脂拥有优异的力学性能和热性能,但是不能重新加工且很难降解,通过将席夫碱引入热固性树脂中,利用其解离机制使热固性树脂具备重塑性与降解性是生物质材料的研究热点.本文介绍近年来席夫碱结构热固性树脂的合成方法,列举了常用的合成材料,并阐述了席夫碱结构的降解机理,针对席夫碱结构的特点列举了不同的应用领域;最后总结全文并提出了展望.
