Date of Award

January 2017

Degree Name

Master of Science (MS)

Department

Biomedical and Chemical Engineering

Advisor(s)

Julie M. Hasenwinkel

Keywords

Bone cements, Ethylene glycol-dimethacrylate, Highly viscous, Poly(methyl methacrylate), Two-solution

Subject Categories

Engineering

Abstract

Bone cements are primarily used for fixation of implants as well as dampening of mechanical loads between the implant and neighboring bone. Two-solution bone cements offer a variety of advantages over commercial powder-liquid compositions due to a reduction in porosity, which in turn leads to improved mechanical properties. The effectiveness of the material is limited by its mechanical properties due to a large mismatch in moduli and strength between the cement, bone, and implant. Two-solution bone cements modified with ethylene glycol-dimethacrylate (EG-DMA) as a crosslinker have been developed as an attempt to further improve the mechanical and thermal properties of the material. The crosslinker replaces a volumetric portion of the methyl methacrylate (MMA) monomer and the resulting mechanical, thermal and viscous properties were compared to a formulation free of EG-DMA.

The result of this study shows that EG-DMA can increase the mechanical properties and fractional monomer conversion without significantly (p<0.05) affecting the thermal characteristics, including maximum polymerization temperature and setting time. The maximum flexural strength and bending modulus increase with increasing EG-DMA concentrations up to 10 vol% EG-DMA, and then decrease following a second order polynomial fit. The critical stress intensity factor increases up to 5 vol% and then decreases with increasing EG-DMA content, and the yield strength increases up to 15 vol% EG-DMA. These results indicate that up to a certain concentration, EG-DMA vol% has more of an effect on a specific mechanical property than decreasing the MMA concentration.

All EG-DMA compositions had a higher viscosity than the control at all measurable shear rates due to a higher polymer to MMA ratio. These formulations demonstrated an increase in ductility and the fractured samples displayed different surface morphologies than the control samples. Sample sets containing EG-DMA did not fracture at the upper strain limit (10%) during flexural tests, except 10 and 15 vol% EG-DMA. The fractured EG-DMA samples exhibited evidence of large amounts of plastic strain before failure, indicated by micro-troughs and ridge formation. Samples containing 20 vol% EG-DMA had the highest fractional monomer conversion and lowest residual monomer concentration. This was attributed to the high reactivity of EG-DMA molecules in the presence of an initiator.

These formulations provide insight into the effect of substituting a crosslinker for MMA monomer in a two-solution injection system and layout the ideal concentrations of EG-DMA for superior mechanical or fractional monomer conversion properties.

Access

Open Access

Included in

Engineering Commons

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