Application of Vitrimer as a Sizing Agent onto Carbon Fibres through Thiol-ene Photo-polymerization

Abstract

This research is dedicated to applying vitrimer material as a sizing agent onto carbon fibres and to analysing the properties of vitrimer-sized CFs. The vitrimer material, bisphenol A glycerolate di(norbornenyl ester) (BPAGDN) was synthesised as the sizing agent of AS4 carbon fibres (CFs). The BPAGDN was made of 1 moleq bisphenol A diglycidyl ether (DGEBA) cured by 2 moleq 5-Norbornene-2-carboxylic acid (NCA) with 0.1 wt% tetrapropylammonium bromide (TPAB) as a catalyst. Surface treatments of oxidation and silanization were carried out on unsized AS4 CFs prior to application of vitrimer sizing agent. The surface oxidation was applied by heating AS4 CFs in nitric acid (64-66% v/v) at 85„degreeƒfor 1h and the silanization was performed by immersing CFs in ethanol solution (90% v/v) with addition of 5 wt% (3-Mercaptopropyl) trimethoxysilane (MPTMS) at 70„degreeƒfor 6h. The CFs materials were washed and vacuum dried after each surface treatment. The vitrimer sizing was conducted by dip-coating AS4 CFs in BPAGDN with addition of 25wt% ethyl acetate together with 0.05 moleq 1,5,7-Triazabicyclo [4.4.0] dec-5-ene (TBD) and 0.05 moleq 2,2-Dimethoxy-2-phenylacetophenone (DMPA) as bond exchange reaction (BER) catalyst and photo initiator. After that, the CFs were irradiated with UV light with a wavelength of 365nm and power of 10 mW/cm2. CF samples with different irradiation time were produced followed by washing and vacuum drying. The mechanism involved in the BPAGDN synthesis reaction and the time required for full reaction were determined from the Fourier-transform infrared spectroscopy (FTIR). The molecular structure of the synthesised BPAGD molecule was validated from the nuclear magnetic resonance spectroscopy (NMR) results. The X-ray photoelectron spectroscopy (XPS) results from CF samples showed successful oxidation, silanization and vitrimer sizing applied on AS4 CF surfaces. The monofilament tensile test was used to evaluate the influence of surface treatments on the mechanical properties of AS4 CFs. The Scanning Electron Microscopy (SEM) was performed to visualise the influence vitrimer sizing has on surface microstructures and morphologies.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Alberto Saiani (Supervisor) & Jonny Blaker (Supervisor)