Degradable bio-based epoxy vitrimers based on imine chemistry and their application in recyclable carbon fiber composites

Traditional epoxy resin materials are widely used in coatings, composite materials, electronic packaging materials, etc. They are usually made of unsustainable fossil resources and cannot be recycled under mild conditions. Degradable thermosetting resins with dynamic covalent structure provide a potential solution to this conflict. In this paper, using biomass energy vanillin, m-xylylenediamine and 1, 6-hexanediamine as raw materials, two dynamic imine bond curing agents were synthesized, and then cured with DGEBA to prepare two bio-based imine epoxy vitrimers. The thermal and mechanical properties of two imine epoxy vitrimers were studied and compared in detail. Results showed that the two types of polymers exhibit excellent thermal stability and solvent resistance. At the same time, the tensile strength, modulus and elongation at break were comparable to or even better than those of conventional bisphenol A epoxy resin. In addition, due to the hydrolysis of the dynamic imine bonds, vitrimers had degradable characteristic, and its degradation also exhibited temperature, solvent and acidity dependence. More importantly, the recyclable carbon fiber reinforced polymer composites made of these two vitrimers could be completely degraded under weak acid conditions, and the nondestructive recycling of carbon fiber composites could be realized. We envision that this vitrimers with simple process, excellent comprehensive properties and degradability will make it a potential candidate for applications in sustainable structural materials.

     

防砂用硅酸盐复合材料增渗剂的研制与性能评价

经过大量实验,制得了用于提高硅酸盐复合材料固结体渗透性的增渗剂ZSJ,该增渗剂以有机高分子为原料,通过化学改性使有机高分子的性能满足防砂技术的要求,再混配以无机材料组成.对ZSJ的理化指标进行了测定,结果表明ZSJ的初熔温度为95℃、针入度为12mm,易溶于油不溶于水.它能使硅酸盐复合材料固结体的渗透率在0.5～1.5μm2内调节,渗透率大小与其ZSJ的加量成正比,并保持硅酸盐复合材料固结体抗压强度维持在5～7MPa内.现场试验证明,该增渗剂能够很好地增加硅酸盐复合材料的渗透性,使硅酸盐复合材料具有较好的防砂性能,是一种新型的应用于硅酸盐复合材料中的防砂增渗材料.     

Highly Sensitive Detection of Fe3+ Ions Using Waterborne Polyurethane‐Carbon Dots Self‐Healable Fluorescence Film

In this study, nitrogen‐doped carbon dots (N‐C‐dots) are synthesized via a green and gentle electrochemical‐hydrothermal method. The N‐C‐dots are grafted into the backbone of waterborne polyurethane (WBPU) synthesized from hexamethylene diisocyanate and polycarbonate diol (PCDL). Due to the introduction of N‐C‐dots, the WBPU is functionalized including being able to self heal and specifically identified Fe³⁺. The self‐healing performance of the WBPU‐N‐C‐dots film is principally attributed to the hydrogen bonding effect of the WBPU and the N‐C‐dots. On the other hand, based on the quenching of fluorescent characteristics of the WBPU‐N‐C‐dots film, it is successfully used in the detection of Fe³⁺, showing a wide detection range, good selectivity, and high sensitivity. What's more, the tensile strength of the sample is enhanced from 3.50 to 7.12 MPa when the N‐C‐dots content is increased in the WBPU and the thermal stability is improved as a result of the formation of the more thermally‐stable network structures. Interestingly, compared to the traditional solution detection in WBPU‐N‐C‐dots emulsion with the limit of detection of 2.23 × 10^?6 m , the detection has the lower limit of detection of 2.19 × 10^?6 m in the WBPU‐N‐C‐dots film. These results show that the WBPU‐N‐C‐dots film exhibits great application as an intelligent response‐type material.