Phosphate glass fibre reinforced composite for bone repair applications: investigation of interfacial integrity improvements via chemical treatments

Hasan, Muhammad Sami (2012) Phosphate glass fibre reinforced composite for bone repair applications: investigation of interfacial integrity improvements via chemical treatments. PhD thesis, University of Nottingham.

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Bone repair devices made from degradable polymers, such as poly lactic acid (PLA) have limitation in terms of matching the mechanical property requirements for bone repair, both initially and for the duration of repair. For this reason the use of totally degradable phosphate glass fibre (PGF) reinforced PLA composite has proved attractive. A crucial part of the success of such implants is maintenance of interfacial integrity between the polymer matrix and reinforcement phases of the composite. It is well known that most fibre reinforced composites loose 50% or more of their strength due to interfacial integrity loss. In this study candidate chemical treatments for PGF reinforced PLA composite are being investigated in terms of their reactability, biocompatibility, effect on interfacial mechanical properties and degradation behaviour of these composites.

As a crucial part of this project, phosphate based glass (PBG) formulations were devised and assessed for structural, thermal, degradation and cytocompatibility variations with varying P2O5 or Fe2O3 content. Selected formulations were drawn into fibres and tested for single fibre tensile strength. Finally, a glass formulation (P45Ca16Mg24Na11Fe4, number indicates percentage molar concentration of oxides) was selected for surface modification and composite production.

Chemical surface treatments were selected on the basis of potential to react with PBG and PLA. Mode of chemical interaction between PBG and surface treatments chemicals were analysed using surface analyses techniques (FTIR and XPS). It was found that aminopropyltriethoxy silane (APS), etidronic acid (EA) and hexamethylene diisocyanate (HDI) were linked through covalent bonds, other agents making hydrogen bonds with PBG. Chemical treatments were optimised and investigated for their effect on interfacial shear strength (IFSS) between polymer/glass, wettability and degradation behaviour. Chemically treated PBG was also assessed for cytocompatibility of elution products, short–term direct contact with MG63 osteosarcoma and long term direct contact with primary human osteoblasts. All selected surface treatment chemicals except amino phosphonic acid (APA) improved the interfacial bond between PBG and PLA. However, the covalently linked agents (HDI, APS and EA) saw up to 4–fold improvement in IFSS. SPLA also improved the IFSS significantly, which was attributed to the presence of several –OH groups. There was no significant effect on degradation rate of PBG. All agents demonstrated acceptable cytocompatibility for their elution products and in direct contact.

Selected chemicals (APS, EA, SPLA and HDI) were investigated further in PGF reinforced PLA composite. PGF mats (UD or non–woven), treated with surface treatment chemical were sandwich–pressed between PLA sheets. Flexural mechanical properties with degradation, water–uptake, degradation rate and cytocompatibility were tested. It was found that surface chemical treatment improved the initial flexural properties (APS, SPLA) and/or delayed the mechanical integrity loss (HDI, APS), latter was attributed to the reduced water–uptake and maintenance of relatively strong interface. Human osteoblasts were found to perform normal functions when cultured on prepared composites.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Scotchford, C.A.
Walker, G.S.
Keywords: phosphate glass, PLA, composite, interface, coupling agents, bone repair, cytocompatibility, FRC
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Faculties/Schools: UK Campuses > Faculty of Engineering > Department of Mechanical, Materials and Manufacturing Engineering
Item ID: 12777
Depositing User: EP, Services
Date Deposited: 25 Apr 2013 09:33
Last Modified: 13 Sep 2016 21:11

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