Facile synthesis of intrinsically flame‐retardant epoxy thermosets with high mechanical properties from lignin derivatives

Abstract

Preparing bio-based epoxy resins with high performance is crucial to sustainable development. However, seeking renewable and flame-retardant epoxy resins with high mechanical properties are still challenging. Here, we reported a facile way to transform lignin derivatives to intrinsic flame-retardant epoxy resins with satisfactory mechanical properties. Two guaiacol-based novolac epoxy resins (i.e., GTEP/DDM and GPEP/DDM) were prepared as alternatives for petroleum-based DGEBA/DDM. The cured GTEP/DDM product showed a high T g of 209.5 C, a high tensile modulus of 3.13 GPa, and a high LOI of 28.6% with UL-94 V-1 rating, which outperformed DGEBA/DDM system. Specially, GPEP/DDM resin possessed more superior mechanical properties (e.g., tensile strength of 73.9 MPa, and tensile modulus of 5.85 GPa) owing to additional interactions (i.e., π-π interactions and hydrogen bonds), and outstanding anti-flammability (e.g., LOI of 31.2% with UL-94 V-0 rating) due to the endow of phosphorus-containing groups. The mechanical reinforcement and flame-retardant mechanisms were clarified based on structural evolution and performance variation. This work provides an efficient synthesis route to

A fully bio‐based epoxy resin with excellent mechanical properties combines flame retardancy and degradability

“…In addition, the glass transition temperature ( T g ) of TA‐VAN‐EP obtained from DSC analysis was 190°C (Figure 5C), which was higher than that of EP ( T g = 152°C), further proving its better heat resistance. Comparing the T g and tensile strength of TA‐VAN‐EP with other reported epoxy resins, 11,23,33,35,39–44 we found that TA‐VAN‐EP had a much better all‐around performance (located in the upper right of the picture, Figure 5D).…”

“…(C) The glass transition temperature of EP and TA‐VAN‐EP (DSC). (D) Comparison of T g and tensile strength for TA‐VAN‐EP with other reported epoxy resins (given in detail in the figure) 11,23,33,35,39,40,41,42,43,44 …”

Novel Multifunction Epoxy Thermoset Designed by Manipulating the Silicon-Oxidation Flexible-Rigid Network Topology: Toughening, Strengthening, and Acid/Alkali Resistance

“…Notably, by designing the topological structure and free volume of the cross-linked network, the ESi thermosets overcome the strength–toughness trade-off. In addition, to compare against previous reports and provide a graphical evaluation, the increments in toughness (elongation at break) and strength (tensile strength) of previously reported EPs are presented in Figure e. ,,,,,,– It shows that most current EPs exhibit a strength–toughness trade-off. Moreover, it is difficult to significantly improve toughness while noticeably increasing strength.…”

Facile Synthesis of Phosphorus-Free Biobased Epoxy Resin with Exceptional Flame Retardancy, Mechanical Properties, and Heat Resistance

“…Covalent bonding of flame-retardant motifs into the epoxy matrix can efficiently achieve intrinsic flame retardancy. − Xie et al prepared a difunctional epoxy monomer bis­(2-methoxy-4-(oxiran-2-ylmethyl)­phenyl) phenyl phosphate (BEU-EP) from eugenol. After curing with 4,4′-methylenedianiline (DDM), the obtained resin (BEU-EP/DDM) passes the UL-94 V-0 rating with a LOI value of 38.4%.…”