Multi‐component Epoxy Resin Formulation for High Temperature Applications

Abstract

The high functionality epoxy resins tetraglycidyl-4,4'-diaminodiphenyl-methane(TGDDM) and triglycidyl-p-aminophenol (TGPAP) are the main components in mostaerospace grade epoxy resin formulations. Owing to their high reactivity and highviscosity, TGDDM and TGPAP pose difficulties when used in wet layup compositemanufacturing. As such, these resins are often modified to achieve the desiredperformance both in the liquid and cured states.The main objective of this thesis is to optimise a low viscosity multi-component epoxyresin formulation suitable for use as an aerospace grade composite matrix. Theformulation will allow for the addition of high levels of thermoplastic to improve thefracture toughness of the resin whilst also maintaining resin processability. Through theuse of thermal analytical techniques this thesis aims to study the effects of varying theTGDDM/TGPAP ratio, incorporation of a low viscosity bi-functional epoxy resin, thediglycidyl ether of bisphenol F (DGEBF) and changes to the stoichiometric ratio (r)between reactive groups of the epoxy resin and amine hardener (4,4'-diaminodiphenylsulphone, DDS) in multi-component epoxy resin formulations.Resin formulations were optimised using factorial experimental design (FED). Resultsfrom two FED's showed curing multi-component resins at a low stoichiometric ratiosignificantly increased the processing window whilst also increasing the glass transitiontemperature (Tg) of the cured resin. No apparent benefit could be assigned to theinclusion of TGDDM owing to its poor processability and a Tg similar to TGPAP. Up to60% DGEBF was incorporated in a multi-component resin formulation whilst stillattaining a Tg greater than 220°C. Its inclusion at 60% had the additional benefit ofincreasing the processing window by 48 minutes over TGPAP, an increase of 62%.Two optimised resin formulations, 100% TGPAP (100T) and a binary mix of 60%DGEBF and 40% TGPAP (60D) were taken forward to study the effects of adding athermoplastic toughener (polyethersulphone, PES) in incremental amounts up to 50wt%. SEM images showed all toughened 100T resins had a phase separatedmorphology whilst all 60D resins were homogenous. The phase separation seen in 100Tdid not improve the matrix fracture toughness when loaded at 10 wt% and 30 wt% PES.Only when 50 wt% PES was added did fracture toughness increase in comparison to thehomogenous 60D resins.Through factorial experimental design two epoxy resin formulations which excludedTGDDM were optimised with a low stoichiometric ratio. The optimum aerospaceformulation is dependent on the desired processability and fracture toughness of theresin. High DGEBF-containing formulations give the longest processing windowswhilst the 100%TGPAP formulation toughened with 50% PES has the highest fracturetoughness.

Date of Award	31 Dec 2014
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Arthur Wilkinson (Supervisor) & Richard Day (Supervisor)