Isothermal and Non-Isothermal DSC Analysis towards the Formulation of a Low-Temperature Curing Epoxy-Alcohol Resin

Research output: ThesisMaster's Thesis

Authors

Abstract

Sustainability issues regarding conventional epoxy resins from non-renewable resources led to investigations of bio-based alternatives. One of these alternatives, based on renewable feedstocks, is eugenol, which can be epoxidised at the allyl functionality. In this thesis, the curing behaviour of this monomer was compared to the most frequently used epoxy resin, diglycidyl ether of bisphenol A (DGEBA), with the aid of dynamic and isothermal differential scanning calorimetry (DSC) measurements. The anionic ring-opening homo- and copolymerisation of these monomers in various ratios was initiated by tertiary amines, namely 1-methylimidazole (1-MI) and 2,4,6-tris(dimethylaminomethyl)phenol (K54). This thesis aimed to develop a low-temperature curing epoxy-alcohol formulation without amine co-curing agents. The homopolymerisation showed that K54 was advantageous for low-temperature curing, while 1-MI performed better at elevated temperatures. This was also confirmed by a proton nuclear magnetic resonance (1H NMR) study with phenyl glycidyl ether (PGE) as a soluble model compound. The apparent activation energies calculated based on the Kissinger and Ozawa method were about 10 kJ mol-1 lower for K54 than for 1 MI. Moreover, the dynamic DSC revealed that formulations with epoxidised eugenol (EE) exhibited lower onset temperatures than DGEBA alone. The acceleration of the curing reaction due to hydroxyl groups was even more prevalent in isothermal DSC measurements at 80 °C than in dynamic DSC analysis. The same trends were observed during the copolymerisation of DGEBA and EE. A significant acceleration of the epoxy polymerisation by hydroxyl groups was found for an EE content of only 10 mol%. However, the acceleration due to the phenolic hydroxyl of EE was not confirmed at room temperature in an 1H NMR study. Finally, benzyl alcohol was investigated as an alternative alcohol with a more promising reactivity at room temperature. To conclude, K54 was found to be beneficial for curing at low temperatures and the acceleration of an epoxy-alcohol formulation was shown at 80 °C. However, a monomer with more reactive functionalities than EE should be used for room temperature curing.

Details

Translated title of the contributionIsotherme und nicht-isotherme DSC-Analyse zur Formulierung eines bei niedriger Temperatur aushärtenden Epoxid-Alkohol-Harzes
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
Supervisors/Advisors
Award date22 Mar 2024
DOIs
Publication statusPublished - 2024