The aim of this research is to promote the use of G.R.P. as a structural material. In the past, the use of G.R.P. has been confined to non-load carrying applications. Such uses are still rapidly increasing but in addition significant changes have been made during the last decade in the development of semi-structural and now even fully structural applications. Glass-reinforced plastic is characterized by a high strength but a relatively low modulus of elasticity. For this reasona G.R.P. structure can expect to show large deformations as a result of which the individual structural members will fail under load due to a loss of stability rather than approaching the ultimate strength of the material. For this reason the selection of the geometrical shapes of G.R.P. structural elements is considered to be an important factor in designing G.R.P. structures. The first chapter of this thesis deals with a general review of the theoretical and experimental methods used to describe the structural properties of G.R.P. The research programme includes five stages dealing with the structural behaviour of G.R.P. The first stage (Chapter 2) begins with selecting and designing an optimum box beam cross-section which gives the maximum flexural and torsional rigidity. The second stage of investigation (Chapter 3) deals with beam to beam connections. A joint was designed and manufactured with different types of fasteners used to connect two beam units. A suitable fastener was selected and the research extended to cover the behaviour of long span beams using multiple joints. The third part of the investigation includes a study of the behaviour of box beams subjected to combined bending, shear and torsion. A special torque rig was developed to perform the tests. Creep deformation of 6 m span G.R.P. was investigated as the fourth stage under a range of loading conditions. As a result of the phenomenon of post buckling behaviour exhibited in the compression flange during testing of box beams during earlier stages of the investigation it was decided to consider this phenomenon in more detail in the final stage of the investigation. G.R.P. plates with different fibre orientation were subjected to uniaxial compression and tested up to failure. In all stages of the investigation theoretical predictions and experimental results were compared and generally good correlation between theory and experimental data was observed.

Conjugated microporous polymers (CMPs) are a class of amorphous materials with pore sizes in the micropore range (< 2 nm). CMPs have potential advantages over inorganic and inorganic hybrid materials due to the use of only the lighter elements in the periodic table and their stability as well as having the diversity of organic synthesis not available to activated carbons. Due to their sorption properties CMPs find applications as gas storage materials. By tuning the chemistry and designing the monomers around the chemistry ultrahigh surface areas can be achieved. This way, novel materials with good gas storage capabilities for hydrogen, carbon dioxide, and methane can be synthesised.

Fibrous materials are used in a variety of applications due to their relatively high surface area to volume ratio as well as anisotropic behaviour. Electrospinning is a popular fabrication technique which produces polymer nanofibres with a potentially high molecular orientation. The surface of polymer fibres plays a significant role in many applications thus measurement of their surface properties is essential but challenging due to their relatively small size. In this thesis, ultrafine nanofibres have been produced by electrospinning with their nanofibre morphology controlled by varying different processing parameters. Atomic force microscopy (AFM) adhesion contact mechanics and individual nanofibre wetting measurements have been conducted to explore surface properties of the produced electrospun polymer fibres. Results using traditional Owens-Wendt plots applied to our nanomaterials show electrospun nanofibres have a higher dispersive surface free energy compared to bulk polymer film but a lower polar contribution, giving a total surface free energy in excess of bulk equivalents. A novel proposed model indicates that this nanofibre dispersive surface free energy is intimately linked to density of the polymer and ultimately the molecular spacing or orientation for the polymer chains. Comparisons are made with bulk polymer films to show that a high degree of molecular orientation is present at least at the surface of the polymer nanofibre. Structure investigations on electrospun fibres of polyvinyl alcohol using FTIR and XPS surface techniques explore how an increase in hydrogen bonds formed within nanofibres rather than on the fibre surface enhance this dispersive contribution but lowers the polar contribution. The wetting behaviour of electrospun fibre is extended to assemblies at length scales above individual fibres to highlight how superhydrophobic surfaces can be produced from nanofibre networks with defined spacings and geometries. This superhydrophobicity was adequately described by a Cassie-Baxter model modified to account for the fibrous geometry.

In Europe, the rapidly growing thermosetting foam insulation products industry comprises over 11,500 companies employing over a third of a million people and is worth about 6 billion Euros in trade. It is currently estimated 4-7 % of total new UK production is scrapped and goes to landfill. Estimated costs of disposing of this waste foam are of the order of £20 million/annum to the producers of foam panels and insulation blocks. A new strategic direction for rigid polymeric foams waste management has been developed converting the scrapped thermosetting foams into high added value material that can be used in various applications such as fire resistant insulating applications. Thus by this new innovative recycling process the waste is not only eliminated but benefits can be gained from the new material that comes out of it as a structural composite panel. The project involves a new concept that mixes fragmented scrap thermosetting foams materials with a proprietary liquid that cures at ambient temperature to form an incombustible material capable of withstanding high temperatures >1000 C. In this research different kind of polymeric foams used for manufacturing of reconstituted recycled samples. Sodium silicate solution has been chosen as the binder to binds shredded foams together. Due to fastening of sodium silicate curing different kind of acidic powders have been tested. For increasing of post properties after curing variety of fillers as an additive have been tried through out this research. Different foam cutting methods have been tested to find the suitable shredding routine. Rationale for selection of generic binder and its hardeners/fillers has been discussed in this project. Also as post properties evaluation compressive strength, thermal resistance, fire resistance and acoustic properties of recycled structural composite panels have been measured. At last a model for thermal conductivity of composite panels is developed.

In the construction industry, prepainted metal strip is a widely used material for fagade and roofs of building intended for commercial used. The physical properties of modem coatings are outstanding, however one big problem that remains and which affects the overall coatings performance is dirt pick up. Firstly the effect of weathering induced chemical composition change was evaluated using photo-acoustic infrared spectroscopy (PA-FTIR), and X-ray photoelectron spectroscopy (XPS). The results shown that photo-oxidation processes occurs via Norrish type I and type 11 reaction at several sites on the polymer backbone, with the ester linkage and the melamine crosslinkage being the more reactive. Secondly aluminosilicates have been found to be the main source of soiling with organic pollutants also responsible but to a minor extent, the presence of such dirt was confirmed by XPS analyses. Unusual peak shape was observed on the carbon narrow scans with low binding photoelectron emitted. Finally Polymer/organically modified layered silicates (PLS) nanocomposites are a new class of filled polymer with ultrafine phase dimension. They improve considerably the physical properties of the coating while reducing dirt pick up. The best results were obtained when the insitu intercalative method was used. However the implication of the onium salts is obscure and the relation between the nanocomposite structure and its properties is not well understood.

Composites are normally composed of two distinct phases: reinforcement and matrix. In recent years, a new class of “self-reinforced” polymer composites or “all-polymer” composites, which are based on similar or identical materials for both reinforcement and matrix have generated increasing interests in both academia and industries due to their advantages in terms of processing, interfacial properties and recyclability. Current research trend in this field is to investigate the potential possibilities of all-polymer composites based on high-performance polymer fibres. In this thesis, all-poly(ethylene terephthalate) composites (Part 1) and all-aramid composites (Part 2) were prepared. In Part 1, Chapter 3 describes the melt spinning and drawing of poly(ethylene terephthalate) (PET) into highly oriented fibres, with moduli of 20GPa and tensile strengths of 925MPa. The effects of spinning and drawing conditions on the mechanical properties of PET fibres were studied. In the following Chapters 4 and 5, all-PET composites were prepared from 1) hot compaction of bi-component multifilament PET yarns; and 2) a film stacking technique, i.e. combining PET tapes unidirectionally with copolyester adhesive films in an alternating “brick-wall” layer-by-layer structure. The effects of processing conditions on mechanical properties were investigated. In Part 2 Chapter 7, all-aramid composites were prepared by a selective surface dissolution method where aramid fibres were partially dissolved to form a matrix phase to bond remaining fibres together into composites. The structure, morphology and mechanical properties were characterized by X-ray diffraction, scanning electronic microscopy, dynamic mechanical analysis and tensile testing. Compared to traditional aramid/epoxy composites, these all-aramid composites show significantly high mechanical properties, even at elevated temperatures. In Chapter 8, the effects of processing conditions on various properties of all-aramid composites were studied and an optimum condition was found. By replacing high concentration sulphuric acid as a solvent, a mild mixed solvent was used to dissolve aramid fibre surfaces in Chapter 9. In this way, all-aramid composites with prolonged immersion times were prepared and characterized. Potential future work including all-PET composites from post-consumer PET waste, microstructural characterization of all-aramid composites and woven all-aramid composites are discussed in Chapter 10.

Since the discovery of carbon nanotubes (CNTs) and nanoclays, there has been a great deal of research conducted for uses in applications such as: energy storage, molecular electronics, structural composites, biomedical to name but a few. Owing to their unique intrinsic properties and size means that they have an ever growing potential in the consumer and high technology sectors. In recent years the concept of using these as fillers in polymers has shown great potential. One such function is, as flame retardant additives. These possess much better environmental credentials than halogenated based additives as well as only needing to use a small loading content compared to traditional micron sized fillers. The combination of the above make these fillers ideal candidates for polymers and their composites. Especially with regards to natural fibre composites. Owing to environmental awareness and economical considerations, natural fibre reinforced polymer composites seem to present a viable alternative to synthetic fibre reinforced polymer composites such as glass fibres. However, merely substituting synthetic with natural fibres only solves part of the problem. Therefore selecting a suitable material for the matrix is key. Cellulose is both the most common biopolymer and the most common organic compound on Earth. About 33 % of all plant matter is cellulose; i.e. the cellulose content of cotton is 90 % and that of wood is 50 %. However just like their synthetic counterparts, the poor flame retardancy of bio-derived versions restricts its application and development in important fields such as construction and transportation. Abstract -vi- Traditional methods to improve the flame retardancy of polymeric material involve the use of the micron sized inorganic fillers like ammonium polyphosphate (APP) or aluminium trihydroxide (ATH). Imparting flame retardancy with these inorganic fillers is possible but only with relatively high loadings of more than 50 wt. %. This causes detrimental effects to the mechanical properties of the composite and embrittlement. Applying nanofillers can achieve similar if not better flame retarding performances to their micron sized counterparts but at much lower loading levels (<10 wt.%), thus preserving better the characteristics of the unfilled polymer such as good flow, toughness, surface finish and low density. This is the main focus of this study and it will be achieved by using various experimental techniques including the cone calorimeter and the newly developed microcalorimeter. After a comprehensive literature survey (Chapter 2), the experimental part of the thesis starts with a feasibility study of a flame retardant natural reinforced fibre sheet moulding compound (SMC) (Chapter 3). This work demonstrated that with a suitable flame retardant the peak heat release rate can be reduced. Chapter 4 deals with further improving the flame retardancy of the previously used unsaturated polyester resin. The aim is to study any synergistic behaviour by using aluminium trihydroxide in conjunction with ammonium polyphosphate whilst testing in the cone calorimeter. In Chapter 5, nanofillers are used to replace traditional micron sized fillers. In unsaturated polyester, multi-walled carbon nanotubes and sepiolite nanoclay are used together to create a ternary polymer nanocomposite. The microcalorimeter was employed for screening of the heat release rate. This work showed that the ternary nanocomposite showed synergistic behaviour with regards to significantly reducing the peak heat release rate. Abstract -vii- The same nanofillers were utilised in Chapters 6 and 7 but this time in combination with a thermoplastic (polypropylene) and bio-derived polymer (polylactic acid), respectively. In both systems an improved flame retardancy behavior was achieved whist meeting the recyclability objective. Chapter 8 attempts to show how the optimised natural fibre composite would behaviour in a large scale fire test. The ConeTools software package was used to simulate the single burning item test (SBI) and to classify the end product. This is a necessity with regards to commercialising the product for consumer usage. Finally, Chapter 9 is a summary of the work carried out in this research as well as possible future work that should be conducted.

A variety natural materials that are environmentally friendly, renewable and low cost have been created. Bacterial cellulose (BC), which is produced by a harmless bacterium, Acetobacter xylinum, has been used as a reinforcement agent to form bionanocomposites. Apple and radish pulp which are themselves cellulosic, were blended with bacterial cellulose to produce a high quality nanopaper which can be used for special purposes. The resulting sheets are characterised in terms of their morphology as well as their mechanical and thermal properties. Another approach adopted was the combination of BC with bio-polymers such as poly (ε-caprolactone) and a commercially available starch based polymer, Mater-Bi. Freeze-dried BC, which was kept in its 3D shape, was used as a comparison. These innovative composite systems are non-petroleum based and are biodegradable. The morphology, structure, thermal properties and performance of the resulting bio-composites were investigated using scanning electron microscopy, Fourier Transform Infrared spectroscopy, Differential Scanning Calorimetry, Dynamic Mechanical Analysis, and by measuring the mechanical properties. Purification is a crucial step in removing impurities and another organic materials remaining in the BC. The BC gel which was purified in two steps, i.e. with 2.5 wt.% NaOH and then bleaching with 2.5 wt.% NaOCl respectively, showed a greater performance in its thermal and mechanical properties. In addition, it was shown that the cellulose I structure of BC is not converted to cellulose II. BC is an interesting material for in-vivo studies. However, to make it an interesting biological composite a suitable resin must be found. Poly (vinyl alcohol) (PVA) is a known water soluble polymer and is therefore a suitable candidate material. In this study BC was grown in PVA solution to produce an in-situ composite. The concluding work for this project is an in-vitro study of BC for scaffolds for tissue engineering. The BC network was seeded with bovine chondrocytes (bone cells) obtained from an 18 months old deer and cultured into the BC gel to establish the viability of this material for medical applications.

This thesis concerns the thermal behaviour and isothermal crystallisation kinetics study of cyclic polyesters and its blends, in particular cyclic poly (butylene terephthalate) (c-PBT). The production of c-PBT is interesting; in fact it is different from production of conventional linear PBT since c-PBT is produced by in situ polymerisation of cyclic butylene terephthalate oligomers (CBT) in the presence of suitable initiators or catalysts. These relatively novel materials, i.e. CBT offer many advantages in properties and the most unusual and useful is that they can be processed at low viscosity (water like) and exhibit rapid crystallisation. The thermal behaviour and isothermal crystallisation kinetics of CBT and c-PBT were analysed. The most significant achievement of this project is blending where blends of c-PBT and styrene maleimide (SMI) were prepared by simultaneous in situ polymerisation and melt blending of solid dispersion CBT/SMI powder. This is unique and novel and the results show consistency and signs of miscibility although there are no external forces applied during the melt blending. It was found that the presence of 30 wt % and above of SMI impeded the crystallisation of c-PBT. This suggests that miscibility occurred. The miscibility of these c-PBT/SMI blends was support with the presence of a single composition-dependent glass transition temperature and negative Flory-Huggins interaction parameter. Studies on crystallisation kinetics of c-PBT were also done by Avrami analysis and using the Hoffman-Lauritzen theory. Previously there have been very limited studies of the crystallisation kinetics of PBT produced from its oligomer. Further work on crystallisation of c-PBT/SMI blends was also performed.

Dendrimers are globular macromolecules that have a range of applications. These nonnally exploit the individual prope1ties of the functional groups that make up the overall dendrimer. The polyvalent properties of dendrimers are widely used in biomedical scaffolds and catalysis. The internal cavities with the structure can also be harnessed for encapsulation. This application has evoked interest especially within the bio-medical field, using dendrimers as host molecules to increase the solubility of drug molecules. In this research, a set of dendrimers were prepared to test the potential of encapsulation and manipulation of the host structure. The dendrimer products contained thiophene spacer groups and a thiophene outer shell, with alkylated terminal groups. The hetcro­ aromatic rings were held around a phenyl core and internal generations to create the cavity space. After the phenyl-cored thiophene dendrimers were fully characterised, iodoform was used as a guest molecule and incorporated into the dendrimer structure to fonn an encapsulation complex. At this point it was seen that the second dendrimer had the potential to encapsulate and hold iodoform within its internal structure. UV-visible spectroscopy was used to verify how the presence and the overall amount of encapsulated iodofonn. Following these results a microgravimetric study was carried out, and it confinned the ratio of dendrimer to iodof01m (I :2.76). A minimised (MM3) molecular model of each of the dendrimers indicated that there was a possible van der Waals interaction between the thiophene moieties of the dendrimer and iodoform and confirmed that the second dendrimer was more likely to be efficient in encapsulating the guest molecule. Fmther molecular modelling showed that a four­ branched dendron was likely to increase the encapsulation potential. The dendrimers were exposed to iodine vapour to study the effect of doping. This was followed by UV-visible spectrometry, but data were mainly collected and compared by electrical conductivity measurements. It was shown that the dendrimer which contained a larger number of conjugated thiophene rings was much more conductive. The calculated charge carrier mobilities and conductivities were relatively low compared to those of large thiophene oligomers or polythiophene. This was expected as the charge had to hop frequently between dendrimer molecules compared to a single polymer. It was predicted that after encapsulation, the oxidised dendrimer complex would be affected by some torsion of the bond between the thiophene rings. Cyclic voltammetry for the second dendrimer displayed peaks for both n- and p-type doping. From this, the electrochemical band gap was calculated and compared to the optical band gap obtained from the UV-visible spectrum. The values were 2.6 ±0.1 eV.