Zhu, Chenkai
(2016)
Scale-up manufacture and characterisation of resorbable phosphate based glass fibre for textile production.
PhD thesis, University of Nottingham.
Abstract
Bioresorbable phosphate-based glasses (PBG) have been investigated for varying tissue engineering applications such as fibrous reinforcement for fully resorbable PLA composite for fracture fixation. The mechanical properties of these composites are determined by the mechanical properties of phosphate glass fibre (PGF) which can be tailored by varying the chemical composition of glass. However, current phosphate glass fibre production is in lab-scale quantities and in single filament form which limits the use of these fibres as they can only be produced as non-woven random or unidirectional fibre mats.
The main aim of this project was to scale-up manufacture of phosphate glass fibres and textile product for reinforcement of PLA composite. The detail objectives included novel phosphate glass formulation development, design and manufacture of multifilament PGF drawing system, multifilament PGF fabrication, textile weaving and textile reinforced PLA composite characterisation.
In this study, PBGs of the system P2O5-B2O3-CaO-MgO-Na2O-Fe2O3 were investigated. In order to determine the effects of replacing P2O5 with B2O3 on the glass structure, thermal properties, density, degradation properties and cytocompatibility studies were carried out. The investigation revealed that the thermal properties and chemical durability of the glass were decreased when phosphate was replaced by boron, due to the increase of BO3 units which, could increase crystallisation tendency and easily be attacked by solution.
During phosphate glass fibre fabrication, single filament fibre fabrication was achieved successfully using all glass codes of glass system (48-x)P2O5-(12+x)B2O3-14CaO-20MgO-1Na2O-5Fe2O3. In order to produce phosphate glass fibre, all phosphate based glasses in this study were taken into account during single filament fibre drawing trials. To assess the performance of the single filament fibres, the PGF were subjected to mechanical and degradation testing. The performance of PGF was assessed by measuring three different post-processing methods including: annealed, size (water-soluble epoxy size) coated, and size coated and heat-treated. It was found that size coating and annealing treatment of the fibre improved the chemical durability of fibres significantly, whilst heat treatment damaged the coatings on the fibre and eliminated the protection on fibre surface.
Based on the success from the single filament fibre manufacture, the glasses with excellent fibre drawing performance were then used in multifilament fibre fabrication. A novel furnace design was then used as a multifilament fibre drawing system. The final multifilament fibres were produced successfully and coated with water-soluble epoxy size for fibre combination and surface protection. Final strands of multifilament fibre were rewound and combined to be fibre products such as roving (without twist) and yarns (with twist).
The PLA composite reinforced by unidirectional (UD) roving or yarns were produced and investigated in vitro in terms of degradation profiles and mechanical property retention in order to evaluate the effect of fibre volume fraction and twist on the performance of composites. The flexural properties of UD composites were found to rapidly reduce in aqueous medium, and the high level of twist was also seen to reduce the flexural properties of composite.
With the design and manufacture of a small inkle-type loom for hand weaving, yarns were used successfully in the small Inkle-type loom to produce narrow, plain weave textiles which, to the authors knowledge is the first time textile products of phosphate glass fibre has been produced in the world. The cytocompatibility of this textile was investigated via MG63 cell seeding on the textile surface and characterisation of cell metabolic activity. For further study, the textile reinforced PLA composite was produced and compared with a 0°/90° unidirectional lay-up composite as a pseudo-zero crimp textile. Due to the limitation of the hand weaving technique, a higher density of yarns laying along the longitudinal direction (load direction) demonstrated greater mechanical properties when compared to 0°/90° composite. Retention of mechanical properties for both composites was also investigated during a degradation study and ~20% flexural strength was maintained for both textile reinforced composite and 0º/90º lay-up composite.
Generally, this novel composite could be a good preliminary study to investigate feasibility of industrial scale production of phosphate glass fibre reinforced composites. However, fast degradation behaviour resulted in significant reduction of mechanical properties of composite. As such, the development of novel glass formulations with better degradation behaviours and good fibre drawing performance should be taken into account in future research.
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