Design of controllable degradable epoxy resin: High performance and feasible upcycling

Abstract

Endowing epoxy resin with high performance, controllable degradation as well as feasible upcycling is a huge challenge. Herein, we synthesized a bio-based amine curing agent containing spiro diacetal unit using an environment-friendly method, then the controllable degradable epoxy resin was obtained after the curing reaction between diamine (DVPM) and bisphenol A epoxy resin (DGEBA). Results showed that DVPM-DGEBA resin performed high glass translation temperature of 136 C, glassy storage modulus of 3.93 GPa, and tensile strength of 85.9 MPa, owing to spiro diacetal unit and abundant methoxyl-related hydrogen bonds confirmed by non-isothermal fourier transform infrared spectra (FT-IR) and dynamic mechanical analyses. More importantly, DVPM-DGEBA resin could decompose into soluble linear oligomers in mild acidic solution. Systematically investigated by 1 H nuclear magnetic resonance, gel permeation chromatography, and FT-IR. Furthermore, the recycled oligomers could be reprocessed into thermosetting resins in the presence of diamines, and the upcycling resin performed high-performance (glass translation temperature of 170 C, glassy storage modulus of 6.03 GPa and tensile strength of 86.4 MPa) and flame-retardant (V-0 rating). This work gives us some new ideas to achieve the upcycling of the thermoset resin.

Preparation and properties of carbon fiber reinforced bio‐based degradable acetal‐linkage‐containing epoxy resin composites by RTM process

“…On the other hand, because the epoxy group reacts with the amino group in DDS to generate β‐hydroxylamine, which will form hydrogen bond with methoxy group on vanillin group in DEPVD molecular chain. [ 44 ] Moreover, the amount of hydrogen bonds formed will increase with the amount of β‐hydroxylamine generated, which will further limit the movement of molecular chains, resulting in a rapid enhancement in the viscosity of the resin system. As can be seen from Figure 1B,C, when the temperature is 140°C and the viscosity of the resin system reaches 1 Pa·s, the operation processing window of E51‐DDS resin system reaches 50 min, while that of 70% DEPVD‐E51‐DDS resin system is only 12 min, which can meet the processing window to prepare a size of 300 × 150 × 2 mm composite laminate.…”

“…[40][41][42] Moreover, the recyclable CF/epoxy resin composites with spiro diacetal structure exhibit considerably better mechanical properties and glass transition temperature than CF/bisphenol A resin composites. [43,44] Ma et al [43] prepared CF composites based on the readily recyclable vanillin-based spiro diacetal epoxy resin, which had higher properties than those based on the conventional bisphenol A epoxy resin. Moreover, the ready cleavability of the spiro diacetal structure facilitated the recycling of CF, making the recovered CF possess similar properties as the virgin CF.…”

Epoxy Thermosets Designed for Chemical Recycling

“…In another work, e17 was further reacted with aqueous ammonia in microwave conditions to form an acetal‐containing epoxy hardener, h12 [114] . The DGEBA was further cured with h12 in acetone to yield p(DGEBA‐h12) .…”

“…The network was completely depolymerized in 0.1 M HCl/acetone mixtures at 50 °C within 3 h into monomeric pentaerythritol and aldehyde functional oligomeric structures with molecular weight average of 2,319 g/mol and Đ of 1.3. After determining the aldehyde content of the recycled network (279.8 g/eq aldehyde), it was upcycled upon curing with DDM to yield a polyimine with T g , tensile strength, and Young's modulus of 170 °C, 86.4 MPa, and 2.6 GPa, respectively [114] . In addition, acetal‐containing diamine hardeners ( h13 – h15 ), which are known as Recyclamine®, have been commercially employed in many other epoxy systems [115–118] …”

“…[113] In another work, e17 was further reacted with aqueous ammonia in microwave conditions to form an acetal-containing epoxy hardener, h12. [114] The DGEBA was further cured with h12 in acetone to yield p(DGEBA-h12). The high-performance thermoset showed a high T g of 136 °C, tensile strength of 85.9 MPa, Young's modulus of 2.4 GPa, and a glassy storage modulus of 3.9 GPa.…”