The glass polyalkenoate cements (GPCs) are formed by the acid-base reaction between fluoro-aluminosilicate glasses and polycarboxylic acid in the presence of water. Three series of glasses were produced by modifiying glass LG26 [32.1SiO2. 21.4Al2O3. 10.7P2O5. 21.4CaO. 14.3CaF2] (mole %). In the first series, calcium was substituted by magnesium, and in the second series, calcium in the first series was substituted by strontium. The last series were zinc substitution for calcium in LG26. These glasses were characterised by X-ray diffraction (XRD), magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy and differential scanning calorimetry (DSC). The gradual substitution of calcium by magnesium resulted in the formation of F-Mg(n) species and a disappearance of Al-F species on the 19F MAS-NMR. The 31P and 27Al MAS-NMR showed that all glasses contained Q1 pyrophosphate Al-O-PO3 3- species. In addition, the fully magnesium substituted glass showed the possible formation of magnesium pyrophosphate, Mg2P2O7. The fully zinc substituted glass, however, showed only Al-O-PO3 3- species charge balanced by Zn2+. An increase in Al(V) species was observed on the 27Al MAS-NMR with the fully magnesium and zinc substituted glasses. The presence of magnesium also increased the number of bridging oxygen on SiO4 tetrahedra, but the presence of zinc affected the Q structure of the aluminosilicate network less. GPCs with these glasses were formed with poly (acrylic acid) (PAA) and L-(+)-tartaric acid. The setting reaction of selected cements was studied by 19F, 31P and 27Al MAS-NMR spectroscopy. F-Ca(n) species were clearly shown to be consumed for cement formulation, and F-Mg(n) species were still present in the 19F MAS-NMR spectra of the magnesium containing cements. The Al-O-PO3 3- species were present in the cement. The conversion to Al(VI) from Al(IV) and Al(V) was observed by deconvoluting the 27Al MAS-NMR spectra. The experimental ratio of Al(VI):Al(IV)+Al(V) was higher than the theoretical ratio which may have resulted from the possibility of L-(+)-tartaric acid being involved in the Al conversion during the setting reaction. The working and setting times increased with magnesium substitution, but did not change with zinc substitution for calcium. The compressive strengths decreased with magnesium substitution, possibly resulting from the preferential crosslinking between Mg2+ and COO-. The highest release of fluoride was observed from the fully magnesium substituted cements. Another series of glasses [34.0SiO2. 22.6Al2O3. 5.7P2O5. (22.6-x)SrO. xZnO. 15.1SrF2] (mole %) was produced for formulating GPCs with poly (γ-glutamic acid), PgGA. All the glasses have Al-O-PO3 3- species with no change in the phosphorus environment with zinc substitution for strontium. Al(IV) was found to be the major aluminium species with a small presence of Al(V) and Al(VI). The Q structures of all the glasses were found to be a mixture of Q4(4Al) and Q3(3Al). Similarly, DSC showed a negligible change with zinc substitution for strontium. For cement formulations with PgGA, a co-polymer of PAA and poly (but-3-ene 1,2,4- tricarboxylic acid) was used due to the lower reactivity of PgGA than PAA, and cements with different proportions of PgGA and the co-polymer were formed. The working and setting times increased with PgGA content and zinc substitution. On the contrary, the compressive strengths decreased with PgGA content. The highest zinc containing cements in the series showed the highest compressive strength. A longterm fluoride release measurement showed the highest release from the highest PgGA containing cements, possibly resulting from the cements being less crosslinked. There was a slight increase in the adhesion to dentine.

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This study focused on ink transfer media for the lithographic print process. Rubber blanket is the offset media for ink transfer from plate to substrate. Performance of the rubber blanket is important for successful image reproduction. Thus, this ', project intended to develop a blanket for the lithographic print process that has good sheet release, good ink release, good dot reproduction, good solid reproduction (no pin-holing) and low swelling. The blanket should also maintain its compressibility and be capable of running metallic inks, UV inks· and conventional inks with no significant detrimental effect to the printing surface. Various surface layer compounds for a lithographic print blanket were formulated, with the aid of Minitab, and blankets were made according to the designed formulations. Evaluation work on the blankets for hardness, solvent resistance, critical surface tension, ink transfer, durability and quality of print was then carried out. Consequently, correlations of these characteristics with each blanket material component were studied. It was found that the hardness and the durability of the blanket were influenced by the content of the crosslinking agent and the reinforcing agent within the rubber compound. The solvent resistance and the ink transfer of a 'blanket were influenced by the content of nitrile within the rubber compound. The critical surface tension could be controlled by the change of speed of compound drying and the ingredients or by surface treatment. Following the studies carried, a blanket having significantly improved performance properties was developed. Also, interactions between blanket wash solvents and surface layer' rubber of blanket were studied with the help of FT-IR and GC-MS. It was found that solvent penetration into the surface rubber of a blanket, upon prolonged contact, was the main cause for blanket swell. Plasticisers were easily extracted from the surface rubber of a blanket by the blanket wash solvent, which resulted in a c:1taD&e I()i performance.

The advent of ink-jet technology in the field of three-dimensional printing has paved the way for its use in tactile map production. Tactile maps have raised features that are designed to convey spatial information to visually impaired people through touch. This research investigated the design of tactile ink-jet printers that had to embody printout quality principles to satisfy users' psychophysical preferences, via the manipulation of printout parameters such as: feature elevation, adhesion, texture, shape, contrast and size. Also, droplets coalescence and the control over build-up of three-dimensional micro-structures were investigated to enhance symbol discriminability and tactile map design. Analysis of data from a questionnaire helped formulate the Product Design Specification criteria. Collectively, these research elements culminated in a design methodology for tactile map production using tactile ink-jet printing. Research experiments were facilitated by a drop-on-demand ink-jet testing machine which jetted polymer ink. Tactile map production was enabled through a repetitive print process, depositing ink on the 'substrate and curing it via exposure to Ultraviolet light, resulting in elevated print features. Flexible configuration of the machine enabled the variation and isolation of subsystem parameters such as: Ultraviolet exposure, actuation, substrate types, printhead and ink as well as allowing the simulation of different printer setups. Machine performance data were collected along with data on users' performances and preferences from psychophysical experiments. Devised print algorithms, machine configurations and subsystems analyses established production process principles to yield the required printout quality. Print algorithms achieved three-dimensional profiles that improved adhesion to tested substrates and enhanced users' performance. The relationship between the structure of printed features', the printer's subsystems and users' psychophysical performance called for a two-strand convergent design methodology. While miniaturisation of this technology is possible, until it is more established, bureau-sized printers are best suited to improve the quality and availability of tactile maps.

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