Polymeric membranes have been essential to increasing the efficiency of membrane separation processes. The viability of membrane systems for industrial gas applications lies in the tolerance of such membranes to contamination. While membrane contamination from volatile species can be addressed using purge streams and heat treatment, contamination from non-volatile hydrocarbons can cause a significant decline in membrane permselectivity. This study was focused on the characterization and remediation of cellulose acetate (CA) hollow fibre membranes contaminated by heavy hydrocarbons. CA membranes have a moderate resistance against performance decline from hydrocarbons found in natural gas. Hollow fibre CA membranes were coated with motor oil lubricant to simulate heavy hydrocarbon contamination from large-scale gas compressors and industrial feed streams, and remediation of the CA fibres was conducted using solvent extraction methods. The permeabilities of the membranes to carbon dioxide, helium, hydrogen, methane, nitrogen and oxygen were measured at pressures 300 – 1500kPa and at temperatures 25° – 50°C. It was shown that even a thin layer of oil on the membrane surface can result in substantial losses in membrane performance, with faster permeating gases (e.g. He and H₂) suffering the worst losses. Solvent exchange, in which the membrane was washed using a series of solutions of varying organic content, was unable to remediate the membrane effectively, while the removal of the heavy hydrocarbons by a direct cyclohexane rinse was found to work well to restore the membrane performance.

Polymeric membranes have been essential to increasing the efficiency of membrane separation processes. The viability of membrane systems for industrial gas applications lies in the tolerance of such membranes to contamination. While membrane contamination from volatile species can be addressed using purge streams and heat treatment, contamination from non-volatile hydrocarbons can cause a significant decline in membrane permselectivity. This study was focused on the characterization and remediation of cellulose acetate (CA) hollow fibre membranes contaminated by heavy hydrocarbons. CA membranes have a moderate resistance against performance decline from hydrocarbons found in natural gas. Hollow fibre CA membranes were coated with motor oil lubricant to simulate heavy hydrocarbon contamination from large-scale gas compressors and industrial feed streams, and remediation of the CA fibres was conducted using solvent extraction methods. The permeabilities of the membranes to carbon dioxide, helium, hydrogen, methane, nitrogen and oxygen were measured at pressures 300 – 1500kPa and at temperatures 25° – 50°C. It was shown that even a thin layer of oil on the membrane surface can result in substantial losses in membrane performance, with faster permeating gases (e.g. He and H₂) suffering the worst losses. Solvent exchange, in which the membrane was washed using a series of solutions of varying organic content, was unable to remediate the membrane effectively, while the removal of the heavy hydrocarbons by a direct cyclohexane rinse was found to work well to restore the membrane performance.

Calcium phosphate cements (CPCs) are used as bone void fillers and as complements to hardware in fracture fixation. The aim of this thesis was to investigate the possibilities and limitations of the CPCs’ mechanical properties, and find out if these ceramic bone cements can carry application-specific loads, alone or as part of a construct. Recently developed experimental brushite and apatite cements were found to have a significantly higher strength in compression, tension and flexion compared to the commercially available CPCs chronOS™ Inject and Norian® SRS®. By using a high-resolution measurement technique the elastic moduli of the CPCs were determined and found to be at least twice as high compared to earlier measurements, and closer to cortical bone than trabecular bone. Using the same method, Poisson's ratio for pure CPCs was determined for the first time. A non-destructive porosity measurement method for wet brushite cements was developed, and subsequently used to study the porosity increase during in vitro degradation. The compressive strength of the experimental brushite cement was still higher than that of trabecular bone after 25 weeks of degradation, showing that the cement can carry high loads over a time span sufficiently long for a fracture to heal. This thesis also presents the first ever fatigue results for acidic CPCs, and confirms the importance of testing the materials under cyclic loading as the cements may fail at stress levels much lower than the material’s quasi-static compressive strength. A decrease in fatigue life was found for brushite cements containing higher amounts of monetite. Increasing porosity and testing in a physiological buffer solution (PBS), rather than air, also decreased the fatigue life. However, the experimental brushite cement had a high probability of surviving loads found in the spine when tested in PBS, which has previously never been accomplished for acidic CPCs. In conclusion, available brushite cements may be able to carry the load alone in scenarios where the cortical shell is intact, the loading is mainly compressive, and the expected maximum stress is below 10 MPa. Under such circumstances this CPC may be the preferred choice over less biocompatible and non-degradable materials.