L’objectif de cette thèse est l’élaboration de matériaux fibreux destinés à être utilisés en matériau d’âme dans des structures sandwiches. Les principales applications visées sont l’absorption acoustique et la résistance à l’impact. Nous avons ainsi développé des nontissés épais (environ 10 mm) en para-aramide, ayant une porosité supérieure à 90% et des densités inférieures à 150 kg/m3. Nous avons fabriqué des composites poreux à base de ces nontissés en utilisant diverses résines, dont l’époxy. La technique utilisée permet de conserver une porosité autour de 80%. Nous nous sommes intéressés à l’architecture interne poreuse des nontissés en étudiant les tailles de pores équivalents, l’isotropie, la distribution/orientation des fibres et leur degré d’enchevêtrement à l’aide de tests expérimentaux (perméabilité ; traction/compression ; capillarité ; porométrie) et de modèles théoriques (perméabilité et van Wyk). Nous avons relié les paramètres structurels aux paramètres de procédé de fabrication. Les résultats en acoustique ont démontré le bon pouvoir absorbant des nontissés au-delà de 4000 Hz. Nous avons lié avec succès l’épaisseur, la résistivité au passage de l’air et les tailles de pore obtenus par capillarité, aux propriétés acoustiques via le modèle de Delany et Bazley et le modèle de Johnson et Allard. Nous avons évalué à travers des tests de compression la capacité des matériaux fibreux à absorber et à dissiper de l’énergie : les mécanismes mis en jeu sont les frottement/rupture de fibres et la déformation de la structure. Enfin, les tests à l’impact de nontissés et de composites ont montré un réel potentiel des nontissés au cœur de sandwichs pour amortir l’impact. / The aim of this thesis is to develop fibrous structures in view of using them as core material in sandwich structures, for impact resistance and acoustic applications. Thick para-aramid nonwovens have hence been manufactured, with porosities above 90% and densities below 150 kg/m3. Their thickness was around 10 mm. Porous composites have been obtained from these nonwovens, using various resins (namely epoxy), and with a technique that allows to keep a high porosity level of 80% in the final structure.The internal porous architecture has been studied through different methods and parameters: the equivalent pore sizes, the isotropy, the fibre distribution/orientation and the degree of fibre entanglements have been evaluated with different experimental techniques (air permeability; tensile/compression tests; capillarity; porometry) and using theoretical models (permeability, van Wyk). The structural parameters have been related to the process parameters. The acoustic measurements have shown that our nonwovens were good acoustic absorbers at frequencies above 4000 Hz. The use of two models, Delany and Bazley, and Jonhson and Allard, has shown that the acoustic absorption behaviour can be modelled with the material characteristics (thickness, resistivity and an equivalent pore diameter). The capacity of our materials to absorb and dissipate energy has been evaluated with compression testing. The main mechanisms involved are fibre friction, fibre breakage and structure deformation. Finally, the impact tests performed on nonwovens and their composites have demonstrated the real potential of nonwovens to be used at the core of sandwiches to absorb impact.

Thesis presented in partial fulfillment of the requirements for the degree of Master of Technology (MTech) at Department of Chemistry, Faculty of Applied Science, Cape Peninsula University of Technology 2011 / Aromatic polyamides (PAs) are widely used as high-performance polymers in technical applications due to their unique combination of outstanding thermal, optical, mechanical and chemical properties. Although PAs are mostly utilized where strength or heat resistance is of primary concern, they also find use in other important applications such as in NOMEX membranes for desalination of brackish water or seawater. PAs do however have some disadvantages such as high melting points, high glass transition temperatures (T 9) and a limited solubility in most organic solvents, wh.ich makes their processing difficult. Polyureas (PUs) are generally known for their excellent thermal stability and high chemical resistance due to the presence of thermally stable bonds of aromatic or heterocyclic ring systems along their backbone. Both polymer systems are poorly researched when it comes*' the introduction of furan units into the chains. The same is valid for cases where two or more different diacids or diamines are incorporated. The aim of this study was therefore to investigate the influence of furan units in the polymer chains and the change in properties if the composition of starting materials is varied further. Nineteen PAs were prepared via the interfacial polymerization method and the homogeneous phase polymerization method. These polymers were prepared either with furan- or isophthalic acids in their chains and then compared with the copolymers, containing both diacids in different ratios. Products were characterized by various analytical techniques. Furanoyl-2,5-dichloride (FDC) and different amounts of isophthaloyl chloride (IPDC) - 0, 10, 30 and 50% - as the basic starting monomers were reacted individually with four diamines: m-phenylen diamine (MPD), 4,4'-diamino diphenylsulfone (DDS), 4,4'-diamino diphenylether (ODE) and 2,4-bis(4-aminophenyl)-6-phenyl-1,3,5-triazine-2,4,6-triamine (BAT) by interfacial or homogeneous polycondensation reactions. Two polyureas, starting with furanoyl-2,5-diazide (FDZ) and transformed into the diisocyanate were prepared by reaction with two diamines, namely MPD and DDS in homogeneous solution. The PAs and PUs were characterized by Fourier-Transform Infrared Spectroscopy (FTIR), Proton NMR CH), Carbon NMR C3C), Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The water up-take per polymer unit (mol water I repeat unit of the polymer) was measured. The values for 70% Relative Humidity (RH) were between 0.87 and 1 ~80 moles of water per repeat unit and for 43% RH between 0.40 and 1.35 mols.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2011. / Aromatic polyamides (PAs) are widely used as high-performance polymers in technical applications due to their unique combination of outstanding thermal, optical, mechanical and chemical properties. Although PAs are mostly utilized where strength or heat resistance is of primary concern, they also find use in other important applications such as in NOMEX membranes for desalination of brackish water or seawater. PAs do however have some disadvantages such as high melting points, high glass transition temperatures (Tg) and a limited solubility in most organic solvents, which makes their processing difficult. Polyureas (PUs) are generally known for their excellent thermal stability and high chemical resistance due to the presence of thermally stable bonds of aromatic or heterocyclic ring systems along their backbone. Both polymer systems are poorly researched when it comes to the introduction of furan units into the chains. The same is valid for cases where two or more different diacids or diamines are incorporated. The aim of this study was therefore to investigate the influence of furan units in the polymer chains and the change in properties if the composition of starting materials is varied further.

Reproduction de : Thèse de doctorat : Physique de la matière condensée : Le Mans : 2005. Reproduction de : Thèse de doctorat : Bioorganic and petrochemistry : National academy of science of Ukraine : 2005. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. p. 232 - 254.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 328-339). Also available via the Internet.

Thèses (Ph.D.)--Université de Sherbrooke (Canada), 2000. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Thesis (M.Sc.)--City University of Hong Kong, 2004. / At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.

Thesis (M.Sc.)--City University of Hong Kong, 2004. / At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.

DNA is the pharmacological target for most platinum drugs; however, the majority of these drugs show little or no specificity for particular base pairs. Considerable progress has been made in the design of sequence selective compounds, such that an antiparallel association of a polyamide can have high affinity for selected DNA base pairs. Hairpin polyamides have distinct advantages as they achieve affinities and specificities that are comparable to that of DNA-binding proteins. Platinum(II) hairpin polyamides are expected to display antitumour activity and target specific sequences of DNA. Five DNA-sequence-selective hairpin polyamide platinum(II) complexes, containing pyrrole (Py) and imidazole (Im) heterocyclic rings, have been synthesised using a combination of solid and solution phase chemistry. One mononuclear sequence selective complex, β-Ala-PyPyPy-L4-ImImIm-L4-Pt (HLSP-6) [β-Ala is β-alanine, L4 is 4-(Fmoc-amino)butyric acid and Pt is transplatin], and two dinuclear sequence selective complexes, β-Ala-PyPyPy-L4-ImImIm-L6'-Pt-(Pt) (DNHLSP-6) [L6' is 2,6-Fmoc-Lysine-(Fmoc)-OH] and β-Ala-PyPyImImIm-L4'-PyPyPyPyPy-L6'-Pt-(Pt) (DNHLSP-10) (L4' is 2-Boc-4-Fmoc-L-diaminobutyric acid), were synthesised entirely using solid phase chemistry. Two mononuclear sequence selective complexes, Pt-L6-β-Ala-Py-L4-Im (HSP-2) and Pt-L6-β-Ala-PyPyPy-L4-ImImIm (HSP-6), were synthesised using a combination of solid and solution phase chemistry. The synthesis of a trinuclear sequence selective polyamide was also attempted using a combination of solid and solution phase chemistry. The polyamides were synthesised in a series of reaction steps. Each heterocyclic ring and linker was coupled through solid phase chemistry using 2-(1H-benzotriazole-1-y1)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU). Once the organic components were assembled, the platinum(II) group/s was/were added using either solid or solution phase chemistry. The polyamide sequence of PyPyPy-L4-ImImIm was designed to target the guanine rich telomere region of DNA. The metal complexes reported in this study will span sequences between 2, 5 or 7 DNA base pairs (depending on their length), which include 5'-(A/T)GGG(A/T)-3' and 5'-(A/T)(A/T)(A/T)GGG(A/T)-3'. All complexes were characterised using 1H and 195Pt NMR, high resolution mass spectrometry and elemental analysis. The binding of HLSP-6 and DNHLSP-6 to guanosine was also monitored by 1H NMR. / Doctor of Philosophy (PhD)

Multi-walled carbon nanotubes (MWNTs) are a nanofiller that has desirable multifunctional properties. They have been shown to offer improved mechanical, thermal, and electrical properties in composites. Research has been studying their incorporation into polymer composites. Polyamide 12 is a polyamide of interest that has been manufactured to have lower moisture absorption and higher ductility than other commercial polyamides such as 6 and 6,6 at room temperature. In these studies, MWNTs have been incorporated into polyamide 12 at different weight loadings and using MWNTs with differing outer diameters. The composites were melt processed and characterized using differential scanning calorimetry (DSC) to understand the effects of MWNTs on the crystallization behavior of polyamide 12. A melt peak splitting behavior was observed in the polyamide 12 and composite samples when the specimens were not allowed to fully anneal. Total crystallinity in the samples remained the same between the polyamide 12 and composites when the samples were fully annealed. Total crystallinity increased by 1 to 4 percent in the composites over the polyamide 12 when samples were not fully annealed. The addition of MWNTs to the polyamide 12 system increased the amount of crystallization contained in the lower temperature melting peak. An increase in MWNT concentration resulted in an increase in the crystallinity contained in the lower temperature peak. The addition of smaller diameter MWNTs resulted in a further increase in the lower temperature peak when the outer diameter was below a critical size.