Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE The four-step synthesis of a new bio-based amine hardener is described starting from vanillin as a bio-based compound. The hardener ADBA was utilized to cure DGEBA and the resulting T
g,tanδmax was determined via DMA. Compared to other bio-based curing agents, our curing agent is obtainable in a high yield and leads to a superior T
g of 135°C.

ABSTRACT
Epoxy resins exhibit good mechanical and thermal properties. Most commercially available epoxy resins rely on fossil resources, which is why research is being conducted on the synthesis of bio-based alternatives. Although many scientists dealt with new bio-based epoxy resins, there are still only a few publications on new bio-based amine curing agents. Vanillin is a promising substance for the synthesis of amine curing agents due to its aromatic structure in combination with its potential bio-origin from lignin. In this article, the synthesis of 3-amino-4,5-dimethoxy-benzylamine (ADBA) from vanillin and its use as a novel curing agent for epoxy resins is presented. The synthesis comprises four stages: nitration of the aromatic compound vanillin, methylation of the phenolic group, conversion of the aldehyde into an oxime, and hydrogenation to form the diamine. The diamine can be synthesized with a total yield of 51 wt% and a bio-content of 74 wt%. According to DSC, the new hardener with diglycidyl ether of bisphenol A (DGEBA) shows a gradual curing reaction due to the presence of an aliphatic and an aromatic amine. Glass transition temperatures (T
g) of 135°C were determined via DMA when using ADBA, which is comparable to that of DGEBA cured with IPDA.