The direct catalytic hydrogenation of nitrile butadiene rubber (NBR) in latex form was studied as a model system for the development of a new latex hydrogenation process for the modification of unsaturated diene-based polymers. NBR is a synthetic rubber of copolymerized acrylonitrile and butadiene produced in latex form by emulsion polymerization. The catalytic hydrogenation of NBR is an important post-polymerization process resulting in a more stable and tougher derivative, hydrogenated NBR (HNBR), which has been widely used in the automotive and oil drilling industry. The present commercial process involves a number of cumbersome steps to obtain solid NBR from the latex and subsequent dissolution of the solid NBR in a large amount of organic solvent followed by solvent recovery after coagulation of the hydrogenated NBR. Since NBR is produced in latex form, it is very desirable to directly hydrogenate NBR in the latex form which will significantly simplify the hydrogenation process and facilitate subsequent applications. As an economical and environmentally benign alternative to the commercial processes based on the hydrogenation of NBR in organic solution, this direct latex hydrogenation process is of special interest to industry. The objective of this project is to develop an efficient catalytic system in order to realize the direct catalytic hydrogenation of NBR in latex form. OsHCl(CO)(O2)(PCy3)2 was initially used as the catalyst to investigate the possibility of hydrogenation of NBR in latex form and to understand the major factors which affect the hydrogenation operation. It was found that an organic solvent which is capable of dissolving or swelling the NBR was needed in a very small amount for the latex hydrogenation using the Os catalyst, and gel occurred in such a catalytic system during hydrogenation. Wilkinson’s catalyst, RhCl(PPh3)3, was then used for the latex hydrogenation in the presence of a small amount of solvent successfully without gel formation. Further investigation found that Wilkinson’s catalyst has a high activity for NBR latex hydrogenation without the use of any organic solvent. The influences of various operation conditions on hydrogenation rate, such as catalyst and polymer concentrations, latex system composition, agitation, reaction temperature and hydrogen pressure, have been investigated. It was found that the addition of triphenylphosphine (TPP) has a critical effect for the hydrogenation of NBR latex, and the hydrogenation rate was mainly controlled by the amount of catalyst which diffused into the polymer particles. In the presence of TPP, NBR latex can be hydrogenated to more than 95% degree of hydrogenation after about 30 hours at 160oC using Wilkinson’s catalyst with a catalyst to NBR rubber ratio of 1 wt%, without the addition of any organic solvent. The apparent activation energy for such NBR latex hydrogenation over the temperature range of 152oC to 170oC was found to be 57.0 kJ/mol. In the present study, it was also found that there are some impurities within the NBR latex which are detrimental to the hydrogenation reaction and are suspected to be water-soluble surfactant molecules. Deliberately designed solution hydrogenation experiments were conducted to study the impurity issue, and proper latex treatment methods have been found to purify the latex before hydrogenation. To improve the hydrogenation rate and to optimize the latex hydrogenation system, water soluble RhCl(TPPMS)3 catalyst (TPPMS: monosulphonated-triphenylphosphine) was used for the latex hydrogenation of NBR. The latex hydrogenation using the water soluble catalyst with TPP can achieve more than 90% degree of hydrogenation within 20 hours at 160oC. Further experiments using RhCl3 with TPP proved that the water soluble RhCl3 can be directly used as a catalyst precursor to generate the catalytic species in situ for the latex hydrogenation, and a stable NBR latex with 96% degree of hydrogenation can be produced without any gel problem within 19 hours of reaction at 160oC. The catalyst mass transport processes for these Rh based catalysts in the latex system were investigated in order to further optimize the solvent-free latex hydrogenation process. While maintaining the emulsified state of the original latex, the direct catalytic hydrogenation of NBR latex can be carried out efficiently without any cross-linking problem to more than 92% degree of hydrogenation within 8 hours at 160oC. As a result of this research project, new latex hydrogenation technologies were successfully developed to fulfill all major requirements for a solvent-free polymer latex hydrogenation route, which is a significant milestone for the improvement of this polymer modification technology. The finding of TPP’s role as the “catalyst mass transfer promoter” is a breakthrough for the research field related to the hydrogenation of unsaturated diene-based polymers in latex form.

The research presented focused on the synthesis and the characterization of graft polymers, of interest either as model systems or for large-scale applications. The materials selected as substrates for grafting reactions were carbosilane dendrimers, linear and branched polystyrenes, and cross-linked polystyrene latex particles. The synthesis of dendrimer-arborescent polymer hybrids was thus achieved by derivatization of the carbosilane dendrimers with dichlorosilane moieties and coupling with 1,4-polybutadiene side chains with Mn ≈ 1000. A second derivatization and coupling reaction with Mn ≈ 1500, 5000, or 30000 side chains yielded hybrid polymers with narrow molecular weight distributions (Mw/Mn ≤ 1.16). In the second part of the thesis, a procedure for the large-scale (100-g) synthesis of arborescent styrene homopolymers and copolymers incorporating poly(2-vinylpyridine) segments is presented. End-capping of the polystyryllithium chains with 1,1-diphenylethylene in the presence of LiCl, followed by the addition of 3 – 6 equivalents of 2-vinylpyridine per side chain, eliminated side reactions and led to grafting yields of up to 95 %. A systematic investigation of the solution properties of polyelectrolytes obtained by protonation of the poly(2-vinylpyridine) arborescent copolymers with a strong acid (trifluoroacetic acid) is also presented. The relative importance of the electrostatic repulsion and the elastic deformation forces on molecular expansion was investigated by examining the solution properties of the copolymers as a function of structure, protonation level, and the presence of salts in polar solvents (methanol, DMF, H2O). The viscosity of the arborescent copolymer solutions was also found to be much lower than for linear P2VP samples under the same conditions. In the last part of the thesis, the synthesis of model filler particles was achieved by grafting polyisoprene chains onto cross-linked polystyrene latex particles derivatized with acetyl coupling sites. These substrates, which can be viewed as an extreme case of a dense (hard-sphere) arborescent polymer structure, were used to investigate the influence of filler-matrix polymer interactions on the rheological behavior of filled polyisoprene samples. The influence of the filler structure on the rheological behavior of the blends was examined by dynamic mechanical analysis in terms of frequency-dependent complex viscosity, storage modulus, and damping factor. All the blends exhibited enhanced complex viscosity, storage modulus, and decreased damping factor values relative to the matrix polymer.

The research presented focused on the synthesis and the characterization of graft polymers, of interest either as model systems or for large-scale applications. The materials selected as substrates for grafting reactions were carbosilane dendrimers, linear and branched polystyrenes, and cross-linked polystyrene latex particles. The synthesis of dendrimer-arborescent polymer hybrids was thus achieved by derivatization of the carbosilane dendrimers with dichlorosilane moieties and coupling with 1,4-polybutadiene side chains with Mn ≈ 1000. A second derivatization and coupling reaction with Mn ≈ 1500, 5000, or 30000 side chains yielded hybrid polymers with narrow molecular weight distributions (Mw/Mn ≤ 1.16). In the second part of the thesis, a procedure for the large-scale (100-g) synthesis of arborescent styrene homopolymers and copolymers incorporating poly(2-vinylpyridine) segments is presented. End-capping of the polystyryllithium chains with 1,1-diphenylethylene in the presence of LiCl, followed by the addition of 3 – 6 equivalents of 2-vinylpyridine per side chain, eliminated side reactions and led to grafting yields of up to 95 %. A systematic investigation of the solution properties of polyelectrolytes obtained by protonation of the poly(2-vinylpyridine) arborescent copolymers with a strong acid (trifluoroacetic acid) is also presented. The relative importance of the electrostatic repulsion and the elastic deformation forces on molecular expansion was investigated by examining the solution properties of the copolymers as a function of structure, protonation level, and the presence of salts in polar solvents (methanol, DMF, H2O). The viscosity of the arborescent copolymer solutions was also found to be much lower than for linear P2VP samples under the same conditions. In the last part of the thesis, the synthesis of model filler particles was achieved by grafting polyisoprene chains onto cross-linked polystyrene latex particles derivatized with acetyl coupling sites. These substrates, which can be viewed as an extreme case of a dense (hard-sphere) arborescent polymer structure, were used to investigate the influence of filler-matrix polymer interactions on the rheological behavior of filled polyisoprene samples. The influence of the filler structure on the rheological behavior of the blends was examined by dynamic mechanical analysis in terms of frequency-dependent complex viscosity, storage modulus, and damping factor. All the blends exhibited enhanced complex viscosity, storage modulus, and decreased damping factor values relative to the matrix polymer.

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Thèse doctorat : Génie des Matériaux : Villeurbanne, INSA : 2006. / Contient 1 lexique. Titre provenant de l'écran-titre. Bibliogr. à la fin de chaque chapitre.

Fines have a very important role in paper chemistry and are a determinant in retention, drainage and the properties of paper. The purpose of this project was to be able to label the fines with fluorophores and study their Brownian motion with fluorescence microscopy. When succeeded this could then be used to study fines, fibers and other additives in a suspension thus giving the fundamental knowledge of why fines have this important role. Due to aggregation of the fines no Brownian motion could be detected. Instead the fines were handled as a network system and small fluorescence labeled latex particles were then studied in this system. This approach yields information about the fines when the obstacle with sedimentation of the network is resolved. / Fines har en viktig roll i papperskemin och har en avgörande roll när det gäller retention, dränering och papprets egenskaper. Syftet med detta projekt var att kunna färga in fines med fluoroforer och sedan följa deras brownska rörelse med hjälp av ett fluorescensmikroskop. Denna metod skulle sedan kunna användas för att observera interaktionerna mellan fines, fibrer och andra additiver i en suspension. Det skulle göra de underliggande mekanismerna kända för varför fines utgör en så viktig del i processen. På grund av att fines aggregerade så fick man istället behandla dem som ett nätverk där man tillsatte redan fluorescerande prober vars rörelser studerades. Att studera fines indirekt på detta vis kommer att ge information när sedimenteringen av nätverket är löst.

This thesis aims to improve the performance of latex-based pressure-sensitive adhesives (PSAs). PSA performance is usually evaluated by tack, peel strength and shear strength. Tack and peel strength characterize a PSA’s bonding strength to a substrate while shear strength reflects a PSA’s capability to resist shear deformation. In general, increasing shear strength leads to a decrease in tack and peel strength. While there are several commercial PSA synthesis methods, the two most important methods consist of either solvent-based or latex-based techniques. While latex-based PSAs are more environmentally compliant than solvent-based PSAs, they tend to have much lower shear strength, at similar tack and peel strength levels. Therefore, the goal in this thesis was to greatly improve the shear strength of latex-based PSAs at little to no sacrifice to tack and peel strength. In this study, controlling the polymer microstructure of latexes or their corresponding PSA films was used as the main method for improving the PSA performance. The research was sub-divided into four parts. First, the influence of chain transfer agent (CTA) and cross-linker on latex polymer microstructure was studied via seeded semi-batch emulsion polymerization of butyl acrylate (BA) and methyl methacrylate (MMA). Three techniques were used to produce the latexes: (1) adding CTA only, (2) adding cross-linker only, and (3) adding both CTA and cross-linker. It was found that using CTA and cross-linker simultaneously allows one to expand the range of latex microstructural possibilities. For example, latexes with similar gel contents but different Mc (molecular weight between cross-links) and Mw (molecular weight of sol polymers) could be produced if CTA and cross-linker concentration are both increased. However, for the corresponding PSAs with similar gel contents, the relationship between their polymer microstructure and performance was difficult to establish as almost all of the medium and high gel content PSAs showed very low tack and peel strength as well as extremely large shear strength readings. In the second part of this thesis, in order to improve the tack and peel strength of medium and high gel content PSAs, the monomer composition and emulsifier concentration were varied. It was found that changing the monomer mixture from BA/MMA to BA/acrylic acid (AA)/2-hydroxyethyl methacrylate (HEMA) while simultaneously decreasing emulsifier concentration dramatically improved the corresponding PSAs’ shear strength as well as tack and peel strength. The addition of polar groups to the PSA increased its cohesive strength due to the presence of strong hydrogen bonding; meanwhile, PSA films’ surface tension increased. In the third part, two series of BA/AA/HEMA latexes were generated by varying the amounts of CTA either in the absence or presence of cross-linker. The latexes produced in the absence of cross-linker exhibited significantly larger Mc and Mw compared to their counterparts with similar gel contents prepared with cross-linker. The PSAs with the larger Mc and Mw showed much larger shear strengths due to improved entanglements between the polymer chains. In the final part of the thesis, the performance of the BA/AA/HEMA PSAs was further improved by post-heating. Compared with original latex-based PSAs with similar gel contents, heat-treated PSAs showed not only significantly improved shear strengths, but also much larger tack and peel strengths. The different shear strengths were related to the PSAs’ gel structures, which were discrete in the original PSAs but continuous in the heat-treated PSAs. The improved tack and peel strengths were related to the PSA films’ surface smoothness. During the post-heating process, the PSA polymer flowed, resulting in much smoother surfaces than the original PSA films. In addition, the effect of post-heating was related to the polymer microstructure of the untreated PSAs. Decreasing the amount of very small or very big polymers or simultaneously increasing Mc and Mw could lead to post-treated PSAs with significantly better performance. Moreover, it was found that by optimizing the polymer microstructure of the original latex-based PSAs, it was possible to obtain a treated PSA with similar or even better performance than a solvent-based PSA with similar polymer microstructure. Our original objective was surpassed: in two cases, not only was shear strength greatly improved, but so were tack and peel strength due to the simultaneous modification of PSA bulk and surface properties.

Techn. Universiẗat, Diss., 2006--Darmstadt.

Techn. Universiẗat, Diss., 2003--Clausthal.

A conformação de dispositivos médicos implantáveis a partir de uma blenda exige o desenvolvimento de um produto com propriedades próximas do comportamento ideal, combinando propriedades térmicas e mecânicas e boa resposta tecidual. O Poli (ácido láctico-co-glicólico) (PLGA) e o Poli (isopreno) (IR) foram escolhidos como componentes da blenda com finalidade de promover boa biocompatibilidade e características mecânicas especificas. As blendas foram obtidas por dissolução dos polímeros em solvente orgânico, seguida de secagem. Para determinar a influência do teor de IR sobre as propriedades da blenda, foram realizados ensaios de espectroscopia na região de infravermelho por transformada de Fourier (FTIR), calorimetria diferencial de varredura (DSC), análise dinâmico-mecânica (DMA), microscopia óptica por luz polarizada (POM), análise de dureza, ensaio de tração e análise de viabilidade celular. A presença de IR na blenda provocou alteração na estrutura molecular semi-cristalina do PLGA, bem como influenciou o comportamento mecânico analisado a partir da curva tensão-deformação do material. A blenda se mostrou biocompativel em ambiente celular e em ensaios preliminares em animais, apresentando potencial para aplicação como biomaterial. / The conformation of an implantable medical device from a polymeric blend requires the development of a product with properties as close as possible of ideal behavior with the combination between thermal and mechanical properties and good tissue response. The poly (lactic-co-glycolic acid) (PLGA) and the poly (isoprene) (IR) were chosen as the blend components to promote good biocompatibility and specific mechanical characteristics. The blends were obtained by dissolution of polymers in organic solvent, followed by drying. In order to determine the IR content influence over the blend properties, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), polarized light optical microscopy (POM), hardness analysis, tensile test and cell viability test were carried out. The IR presence caused changes in semi-crystalline molecular structure of PLGA, as well as actuated over the mechanical response analyzed on material’s stress-strain curve. The blend showed itself biocompatible at cellular environment and at preliminary animal tests, presenting potential for application as biomaterial.