Adhesion Improvement of Bio‐Based Epoxy in Environmentally Friendly and High‐Performance Natural Fiber‐Reinforced Composites

Abstract

Developing robust bio‐based epoxy against petroleum‐derived epoxy is necessary for environmentally friendly and high‐performance natural fiber‐reinforced composites. A bio‐based vanillin epoxy (VE) is synthesized from the lignin‐derived vanillin, and a thermoset resin is prepared after mixing it with a 4,4′‐diaminodiphenyl methane (DDM) hardener. Further, it is infused in high‐cellulose‐containing alkali‐treated jute fiber (TJF) mats through a simple approach to enhance the adhesion between the VE‐DDM and TJF. Bio‐based VE‐DDM resin shows better compatibility with TJF than petroleum‐derived bisphenol A diglycidyl ether (DGEBA) epoxy. The bio‐based VE‐DDM/TJF composite demonstrates the Tgis ≈165 °C, tensile strength is ≈83.12 ± 3.80 MPa, and Young's modulus is ≈2.86 ± 0.10 GPa with excellent flexural strength (138.72 ± 3.81 MPa) and flexural modulus (8.01 ± 0.11 GPa). It also shows merits regarding hydrophobicity, reduced water absorption ability, durability, and chemical resistance in an acidic medium. The natural fiber‐reinforced VE composites pave the way to produce environmentally friendly and high‐performance composites for structural applications.

Environment-friendly, high-performance cellulose nanofiber-vanillin epoxy nanocomposite with excellent mechanical, thermal insulation and UV shielding properties

“…However, the absorption bands of the epoxy ring in the cured VE-DDM thermoset were consumed entirely after curing with the hardener. A new absorption band for the C N bond at 1620 cm −1 is due to the reaction between the formyl (-CH O) group of VE and the –NH 2 group of hardener [ 30 , 31 ]. Another noticeable change is the decrease in the band intensity of the formyl group after the curing, suggesting the successful completion of the curing between the epoxy and the hardener.…”

“…In our previous study, the VE-DDM resin showed good interfacial adhesion around 13.93 ± 0.26 MPa with CNF film ( Fig. S7 ) because of its excellent compatibility and crosslinking [ 31 ]. The underlying mechanisms for the increased mechanical properties are etherification and crosslinked network structure.…”

“…Higher loading of CNF promoted the reduction in the toughness of the composites due to the fibers' agglomeration and poor crosslinking of CNF with epoxy. The mechanical properties of the nanocomposites are higher than many biobased vanillin epoxy thermosets [ 10 , 14 , 19 , 21 , 30 , 31 , [35] , [36] , [37] , [38] , [39] , [40] ] and natural fibers-reinforced composites [ 41 , 42 ], as delineated in Fig. 3 d. When the CNF concentrations increased, the mechanical properties dropped gradually due to the fibers' agglomeration and poor fiber-matrix crosslinking [ 14 , 43 ].…”

“…VE resin and cured thermoset were synthesized according to the following procedure [ 30 , 31 ]: first, vanillin (5.0 g) was dissolved in ECH (12.0 g) into the round bottom flask, and then TBAB (5 wt% of vanillin) was mixed and heated at 80 °C for 2 h, as shown in Fig. 1 a.…”

Advancements in Synthesis Strategies and Optoelectronic Applications of Bio-Based Photosensitive Polyimides

“…However, traditional polyimides mostly originate from fossil raw materials, which not only cause environmental pollution and fossil fuel consumption but also may pose a carcinogenic risk to experimental personnel. In the current "dual carbon" context, it is particularly important to develop bio-based polyimides with raw materials partly or wholly derived from biomass [29][30][31]. At present, bio-based polyimides are limited to adding bio-based content, which is far from the early goal of complete substitution.…”