No abstract

Environmentally friendly materials are an integral part of sustainable chemistry, and bio‐based polymer composites are an important class of materials. The manufacture of composites is expected to reduce or even eliminate the use of adjuvants, considering the importance of reducing energy consumption and avoiding health and environmental risks. In this study, a phenyl‐containing, polyfunctional, bio‐based epoxy resin (TGER) was synthesized, and carbon fiber‐reinforced, bio‐based epoxy resin composites were fabricated by vacuum‐assisted resin infusion using two aromatic amine curing agents, 4,4′‐diaminodiphenylmethane (DDM) and 3,3′‐diethyl‐4,4′‐diaminodiphenylmethane (DEDDM). Curing reactions and rheological behavior studies showed that TGER had higher curing reactivity toward DDM and DEDDM than to diglycidyl ether of bisphenol A (DGEBA) and possessed good processability. The results indicated that the resveratrol‐based epoxy resin displayed low‐temperature fast curing properties. The evaluation of the mechanical properties of the carbon fiber composites showed that the flexural strengths of CF/TGER/DDM and CF/TGER/DEDDM were 520 and 628 MPa, respectively. The initial decomposition temperature of CF/TGER composites is above 200°C. Furthermore, the carbon fiber–reinforced biopolymers possess excellent heat resistance. Therefore, carbon fiber‐reinforced, resveratrol‐based epoxy resin composites are promising candidates as alternatives to petroleum‐based high‐performance carbon fiber composites.

As an important thermosetting resin, epoxy resin (EP) is widely used in the field of composite materials. Long storage time, rapid curing and low viscosity of one-component EP is ideal for preparing composite materials by vacuum assisted resin transfer molding (VARTM). For this sake, we developed and synthesized a new imidazole thermal latent curing agent, 4,7-diimidazol-2,1,3-benzothiadiazole (BTD-MZ 2 ) with a yield of about 75%. The curing behavior, thermal stability and storage time of the prepared EP system was studied by differential scanning calorimeter (DSC), thermal gravimetric analyzer (TGA), modular compact rheometer (MCR), respectively. DSC results showed that EP/17.5 wt% BTD-MZ 2 had a good latent period at low temperature, and can rapidly cure EP when heated to 150 C. TGA results show that BTD-MZ 2 promoted the formation of carbon residue and the residual carbon rate of EP/17.5 wt% BTD-MZ 2 is as high as 37.9%. MCR results show that the storage time of EP/17.5 wt% BTD-MZ 2 at 60 C can reach 850 min. In addition, it could play a role of catalyst used as co-curing agents with aromatic amines for EP. DSC test showed that the addition of 5 wt% BTD-MZ 2 reduced the activation energy of EP/4,4 0 -diaminodiphenylmethane (DDM) and promoted the curing reaction.

Vanillin, a rigid compound can be separated from lignin, is a promising sustainable candidate for industrial and high performance polymers, while synthesis of hexa-epoxies is challenging. Meanwhile, carbon fiber reinforced biobased polymers combining high performance are more difficult to be achieved because of the contradictions of liquidity and high rigidity in the polymer structure and performance. In this paper, a novel hexa-epoxy functionalized bio-based epoxy resin (HPVIGEP) with a multi-arm star structure, which simultaneously reduced the viscosity and improved thermo-mechanical properties. The rheological behavior analysis results of HPVIGEP indicated that the viscosity was 3406.9 mPaÁs at 25 C, which dramatically decreased by 75.8% compared to DGEBA (14,096 mPaÁs), leading to excellent processability and adaptability. At the same time, the study on mechanical properties revealed that the cured HPVIGEP manifested 30.6%, 33.7% and 49.0% in higher tensile strength, tensile modulus and storage modulus (30 C) than of cured commercial epoxy, respectively. The tensile strength and flexural strength of carbon fiber composites which were applied HPVIGEP were increased by 9.3% and 10.9%, respectively. In a word, this work provides the promise for the application of environmentally friendly bio-based composite materials.