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Polylactic acid (PLA) is one of the most promising bio-compostable and biodegradable thermoplastic made from renewable sources. PLA, is typically obtained by polymerising lactide monomer. The technique mainly used for ring opening polymerization (ROP) of Lactide is based on metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in suitable solvent. However, the PLA synthesized using such catalysts may contain trace elements of the catalyst, which may be toxic. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3 were considered to perform ROP of lactide monomer using ultrasound as an alternative energy (AE) source for activating and/or boosting the polymerization. Mathematical model of ROP of lactide, was developed to estimate the impact of reaction kinetics and AE source on the polymerization process. Ludovic® software, a commercial code was used. It was adopted for the simulation of continuous reactive extrusion of PLA. Results from experiments and simulations were compared to validate the simulation methodology. Results indicate that the application of AE source in reaction process boost the PLA formation rate. Result obtained through Ludovic simulation and experiments were validated. It was shown that there is a case for reducing the residence time distribution (RTD) in Ludovic due to the ‘liquid’ monomer flow in the extruder. This change in the parameters resulted in validation of the simulation. However, it was concluded that the assumption would have to be established by doing further validations. The simulation model includes the details of kinetics of reactions involved with in the process and helps to upscale the reaction output. This work also estimates the usefulness and drawbacks of using different catalysts as well as effect of alternative energies and future aspects for PLA production.

Characters on computer keyboards are typically printed using one of the two different processes, namely tampographic printing and laser marking. Tampographic printing is time consuming (app. 3-5 mins.), requires skilled workers and employs difficult-to-handle chemicals. On the other hand, the laser marking process is rapid «1 min.), relatively cheap, avoids the need for chemicals and can be carried out with fewer, less skilled operatives than required fortampographic printing. Data from a keyboard production company indicated that there has been a sudden decline in the percentage (from 60% in 2001 to less than 10% in 2003) of laser marked keyboard users over recent years due to a lack of initial contrast of white characters on a dark plastic and poor durability. Under usual office conditions, characters that are used more regularly e.g. 'e' or 's', can be erased in less than 3-6 months. Further, generating a durable high contrast laser mark on dark coloured polymers has also long been an issue. The thesis initially reports on an investigation into the reasons for lack of initial contrast and subsequent discolouration of laser marked and tampo printed characters. This is followed by the development of a range of plastics compounds based on ABS and containing a series of different additives. Criteria for selecting additives that would respond appropriately to a laser are also proposed. The compounds were laser marked under a 1064nm Nd:YAG laser at different power, frequency and speed settings. Plaques of the material were manufactured and laser marked in a grid-like pattern to study both the effect of frequency and speed of marking. The mechanisms associated with the laser-material interaction during the marking process were also investigated using light microscopy and scanning electron microscopy. Microscopy was also employed toobserve the morphology of the marks left by the laser. Finally a unique test regime was designed to characterise the durability of the laser markings under conditions that attempt to simulate those experienced in practice. Results show that aluminium trihydroxide generated superior contrast and exhibited enhanced durability characteristics when compared with nine other micro-additives. Nano-additives, such as nano titanium dioxide portrayed better contrast and durability performance when compared to their micro-size additive equivalents. Analysis of the test plaque results clearly demonstrated that for a specific material compound, it is possible to optimise the laser settings to achieve the best combination of character contrast and durability. Finally, this work is believed to have made a significant contribution to the rather sparse laser markable polymers research field. It will assist in the development of a more fundamental understanding of laser/material interactions and provide a basis for future work in optimising materials formulations for successful laser marking.

The host response to the family of nuclear replicating DNA viruses or the herpesviruses includes the intrinsic, innate and adaptive arms of the immune system. Intrinsic resistance is a constitutively active line of defense against virus infections and members of the Tripartite Motif (TRIM) superfamily of proteins; such as TRIM5 and TRIM19/PML in nuclear domain 10 (ND10) bodies are important restriction factors in this system. Nuclear intrinsic restriction against the prototypical DNA virus, herpes simplex virus 1 (HSV-1) includes interferon-inducible protein 16 (IFI16) and ND10 bodies. However, the viral E3 ubiquitin ligase, ICP0, encoded by wild-type HSV-1, targets these intrinsic immune proteins for degradation. Previous reports on the anti-viral function of TRIM22, the human paralog of the prototypical TRIM5α protein, emphasized its role as a gene of the innate immune system, particularly its expression as a Type I and Type II interferon-stimulated gene and its antiviral function against retroviruses. This study shows that TRIM22 has an additional intrinsic immune role against DNA viruses, using the herpesviruses as an example of a family of DNA viruses. We report that TRIM22 is a novel restriction factor of HSV-1 and limits HSV-1 ICP0-null virus replication. The TRIM22-mediated restriction of HSV-1 occurs after nuclear entry but prior to viral immediate-early gene transcription, by promoting histone occupancy and heterochromatinization to reduce immediate-early viral gene expression. The ICP0-rescued virus evades the TRIM22-specific restriction by a mechanism independent of TRIM22 degradation. We also demonstrate that TRIM22 inhibits other DNA viruses, including representative members of the β- and γ- herpesviruses. These results collectively show that TRIM22 acts in the nucleus, and provide evidence that TRIM22 restricts HSV gene expression by promoting histone occupancy on the viral genes. Furthermore, we identified seven haplotypic variants of TRIM22 and propose that amino acid substitutions in the linker L2 domain and the coiled-coil domain of TRIM22 alter the magnitude of its restriction against the herpesviruses. Together, these results argue for the importance of the TRIM22 gene as a restriction factor against herpesviruses and offer a novel avenue for further investigation on the role of TRIM genes in host genetic variation in herpesviral susceptibility., Medical Sciences