Thermosetting resins undergo irreversible polymerization to form a 3 Dimensional Structure (3D) via a cure reaction. For the present research, properties of thermosetting resins are studied by analysing cure kinetic modelling as well as investigating various additives and fillers to enhance thermal and mechanical propelties for the modified resin composition. Different ratios of Diglycidyl Ether of Bis-Phenol A (DGEBA) are used with aliphatic amidoamine hardener to study the effects of increasing resin content on an epoxy resin/hardener sample. Epoxy/Hardener samples with ratio 2: 1, 3: I and 4: I were studied to investigate the effect of increasing epoxy content on cure and mechanical properties. Analysis using Dynamic Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and cure modelling was used to explain the thermal characterization and tests involving tensile, flexural, Scanning Electron Microscopy (SEM) and hardness explain the mechanical property changes when mixing ratio is varied. DSC and TGA results showed the presence of two peaks especially at higher heating rates of non-stoichiometric ratios. Cure kinetic modelling using autocatalytic equation of Cure Rate (du/dt) predicted the bell shaped curve and estimated cure kinetic constants irrespective of the mixing ratio. ABSTRACT Mechanical and thermal property analysis of samples showed that increasing ratio drives brittle behavior for the DGEBA/Hardener samples. The autocatalytic model is also used for investigating thermal behavior of two part epoxy-adhesive sample. Dynamic scans for adhesive were conducted at heating rates of 5, 10 and 15 QC for a temperature ranging from room temperature to 200 QC. The autocatalytic equation still predicted the bell-shaped curve uSll1g cure kinetic constant determined by Borchard and Daniels method. Chitosan a polysaccharide component which is normally found on exoskeleton of shrimps and crabs was added to epoxy resin to alter the chemical :1 and mechanical properties. Here DGEBA was also used as the primary epoxy base with hardener Hexamethylenediamine (HMDA) to create epoxy/hardener blends with different weight percentage of chitosan. Agglomeration at higher loadings of chitosan was confirmed by morphological analysis and this agglomeration inturn compromised the mechanical properties due to the miscibility of chitosan filler in epoxy. There is a considerable change to thermal stability on adding chitosan. This thesis presents new data on the validity of the analytical curing models to determine thermal and mechanical behaviour of epoxy based resins and adhesives. In addition data on chitosan loaded epoxy shows for the first time achievable levels of filler loadings and consequential thermal and mechanical properties.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:603597 |
| Date | January 2013 |
| Creators | Satheesh, Britto |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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