This thesis reports on the challenge of applying an innovative ‘soft-soft nanocomposite’ design strategy to establish synthesis parameters that affect the performance of coatings based upon water-borne latexes, which is driven by the environmental and legislative need to develop feasible alternatives to solvent-borne coatings. A framework emulsion polymerisation formulation to synthesise core-shell latexes with (poly[(butyl acrylate)-co-(butyl methacrylate)]) core and (poly[(butyl acrylate)-co-(butyl methacrylate)-co-(diacetone acrylamide)]) shell copolymer phases in a controlled manner was established, with high monomer conversions and approximately constant particle numbers. Retention of particle morphology in the films was confirmed using atomic force microscopy (AFM). The effect of adding adipic acid dihydrazide to the latex post-polymerisation to facilitate crosslinking of the shell phase during film formation was found to have a significant effect on the stress-strain properties of latex films. A core:shell mass ratio of 80:20 was found to be optimum in all crosslinked systems tested. Increasing the amount of crosslinking in the shell phase of the particles was found to have an effect on the large strain tensile properties of films, leading to strain hardening with reduced extension to break and higher failure stresses at higher crosslinker levels. Core phase copolymer Tg had a very significant effect upon the low strain mechanical properties, with Young’s modulus values of 5-180 MPa being accessible in the range of core Tg¬s from 5 – 25 oC, although little difference in mechanical behaviour was seen when varying the shell phase Tg from 5 – 15 oC. Adding 2 wt% methacrylic acid (MAA) to the shell phase copolymer gave an additional improvement in the low strain tensile region, with a Young’s modulus of 425 MPa being realised. However, it was found that additional amounts of MAA (up to 5 wt% in the shell phase) were deterious to film properties, with low Young’s modulus and poor extensibility. This was interpreted as being due to an increased concentration of ionomeric crosslinks restricting interparticle chain diffusion and keto-hydrazide crosslinking. Studies to evaluate the mechanical performance of soft-soft nanocomposite films compared to binder latexes used in commercial products were favourable, and showed that a high level of versatility with regards to mechanical properties is possible.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:654865 |
| Date | January 2015 |
| Creators | Eaves, Elizabeth |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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