Novel vanillin-derived epoxy resin: Curing kinetics, thermal, rheological and mechanical properties
Topic(s) : Material science
Co-authors :
Sihem ZAIDI (SPAIN), Daniel SANCHEZ-RODRIGUEZ , Suman THAKUR , Raquel VERDEJO , Jordi FARJAS , Josep COSTA (SPAIN)Abstract :
Due to their outstanding mechanical properties, good adhesion to the fiber and their good thermal stability, a wide range of industries, such as aerospace and automotive, makes use of epoxy resins as matrices for high-performance composites [1]. Their high crosslink stability renders their recyclability extremely difficult. As the majority of epoxies are fossil-based, considerable advances have been made in the production of bio based epoxies including lignin derivatives, because lignin is the most abundant natural aromatic compound on earth. Among them, vanillin stands out from an industrial point of view, because is non-hazardous and it is one of the only few aromatic compounds commercially produced from lignin [2]. Indeed, the epoxy resins derived from vanillin exhibit excellent thermal and mechanical properties owing to the presence of such aromatic ring in their structure [3].
This work presents a detailed characterization of a novel bio-based epoxy resin synthesized from vanillyl alcohol. From the analysis of the curing and degradation kinetics we have been able to generate a Time Temperature Transformation (TTT) diagram, which includes degree of cure, degradation, vitrification and gelation curves. This TTT diagram, which was experimentally validated, results in a processing map that constitute a useful tool to decide the optimal curing conditions in terms of temperature and time, while preventing any undesirable side effects. The processing diagram and its experimental validation confirm that the studied bio-based epoxy thermoset may undergo gelation before vitrification at temperatures as low as 10ºC. This allows the processing of the resin at room temperature. Superior mechanical properties can be achieved after a post-curing treatment at temperatures higher than Tginf = 85ºC.
Fourier-Transform Infrared Spectroscopy characterization of the post-treated samples revealed thermal oxidation to be the main cause of thermal degradation. Besides, we have conducted a rheological and thermomechanical analysis which has proved this vanillin-based epoxy resin to have mechanical properties comparable to other commercial resins derived from bisphenol A diglycidyl ether epoxide, commonly known as DGEBA.
This work presents a detailed characterization of a novel bio-based epoxy resin synthesized from vanillyl alcohol. From the analysis of the curing and degradation kinetics we have been able to generate a Time Temperature Transformation (TTT) diagram, which includes degree of cure, degradation, vitrification and gelation curves. This TTT diagram, which was experimentally validated, results in a processing map that constitute a useful tool to decide the optimal curing conditions in terms of temperature and time, while preventing any undesirable side effects. The processing diagram and its experimental validation confirm that the studied bio-based epoxy thermoset may undergo gelation before vitrification at temperatures as low as 10ºC. This allows the processing of the resin at room temperature. Superior mechanical properties can be achieved after a post-curing treatment at temperatures higher than Tginf = 85ºC.
Fourier-Transform Infrared Spectroscopy characterization of the post-treated samples revealed thermal oxidation to be the main cause of thermal degradation. Besides, we have conducted a rheological and thermomechanical analysis which has proved this vanillin-based epoxy resin to have mechanical properties comparable to other commercial resins derived from bisphenol A diglycidyl ether epoxide, commonly known as DGEBA.