Toughening epoxy resins with modifiers without compromising their modulus and mechanical strength poses a significant challenge. In this work, a bio-based N-heterocyclic-containing reactive toughening agent, HPESZ, was synthesized based on cinnamon derivatives and succinic anhydride. And then the HPESZ was incorporated into the bisphenol A epoxy resin/4, 4′-diaminodiphenylmethane (E44/DDM) curing system to evaluate its effect on the toughening of epoxy resins. The results suggested that the impact strength of the E44/5 %HPESZ/DDM blended system achieved a peak value of 72.4 kJ m −2 , representing a 90.0 % increase over the E44/DDM system (38.1 kJ m −2 ). Subsequently, the toughened system was characterized using scanning electron microscopy and atomic force microscopy to explain its phase structure and toughening mechanism. The cured system produced the chemically induced microphase separation, and the presence of epoxide groups and terminated hydroxyl groups enhanced the interfacial compatibility of E44/DDM, thereby increasing the impact strength. Moreover, the flexural strength, flexural modulus, hardness, and Young's modulus of the blended system were also improved simultaneously. In conclusion, HPESZ is a reactive bio-based toughening agent with promising practical applications.
Xi Ren,Shumin Peng,Wei Zhang,Chunwang Yi,Yuan Fang,David Hui
In this study, a series of adipic acid-polyoxypropylene diamine copolymer (AA-PPA) was prepared by copolymerizing polyoxypropylene diamine (PPA D400) and adipic acid (AA). The AA-PPA with weight-average molecular weight ( M w ) = 10400 and weight-average molecular weight ( M n ) = 7600 was used to modify diglycidyl ether of bisphenol A (DGEBA) epoxy/diethyl toluene diamine (DDM) system. This extended polyether AA-PPA showed unique advantages over traditional polyether at achieving the synchronous enhancement of strength and fracture toughness . With 30 wt% AA-PPA, the bending strength , tensile strength , elongation at break and impact strength were improved by 7.50%, 6.90%, 36.13% and 288.00%, respectively. The single glass transition temperature ( T g ) step proved the homogeneous phase structure of modified epoxy resins. Inevitably, the T g of modified epoxy decreased for the addition of soft segments. The dynamic mechanical analysis (DMA) results indicated that the storage modulus of modified epoxy increased with the increasing content of AA-PPA, while the loss modulus decreased. The interaction of the crosslinked network was explained by calculating the theoretical and measured values of the molecular weight between the crosslinks. The morphology showing the ductile fracture of modified epoxy was testified by scanning electron microscopy (SEM).
危险品化学品经营许可证（带存储）