Adam Strachota

Structural and Surface Properties of Novel Polyurethane Films

In this work, novel polycarbonatediol- and polybutadienediol-based polyurethanes (PU) with promising properties were prepared and compared with an analogous polypropyleneglycol-based product. Hexamethylenediisocyanate was used as isocyanate (NCO) component. All three PU systems were subsequently modified by the incorporation of two different nanofillers (Montmorillonite clays): “Cloisite 15A” and “Bentonite for organic systems.” The PUs were prepared in form of film coatings and characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), and wide angle X-ray scattering (WAXS). Their chemical microstructure was checked by 13C-NMR spectroscopy.

Adsorption behavior of proteins on temperature-responsive resins

The adsorption behavior of proteins on thermo-responsible resins based on poly(N-isopropylacrylamide) and its copolymer containing an anionic co-monomer has been investigated. The influence of the polymer composition, i.e., the content of the co-monomer and crosslinker on the thermo-sensitivity of the protein adsorption has been quantified. The properties of ungrafted polymer as well grafted onto the agarose matrix have been analyzed and compared. Batch and dynamic (column) experiments have been performed to measure the adsorption equilibrium of proteins and to quantify the phase transition process. As model proteins lysozyme, lactoferrin, α-chymotrypsinogen A and ovalbumin have been used. The adsorption process was found to be governed by ionic interactions between the negatively charged surface of resin and the protein, which enabled separation of proteins differing in electrostatic charge. The interactions enhanced with increase of temperature. Decrease of temperature facilitated desorption of proteins and reduced the salt usage in the desorption buffer. Grafted polymers exhibited markedly higher mechanical stability and, however, weaker temperature response compared to the ungrafted ones.

Preparation and characterisation of hybrid organic/inorganic coatings and films

SummariesHybrid organic/inorganic coatings and free-standing films made from GTMS [3-glycidyloxy)propyl]trimethoxysilane, GMDES [3-(glycidyloxy)propyl]methyldiethoxysilane, poly(oxypropylene) of different molecular weights end-capped by amino groups (Jeffamine D-230, D-400 and T-403), and in some cases, colloidal silica, were prepared and characterised. Hydrochloric acid as a catalyst for the sol-gel process and water/propan-2-ol mixture as a solvent were chosen. The structure, morphology and mechanical properties of these scratch-resistant systems were studied by static and dynamic mechanical analysis, small-angle x-ray scattering, NMR spectroscopy and atomic force microscopy. The coatings were fully transparent and colourless with a smooth surface and showed suitable mechanical properties.RésuméDes films indépendants [freestanding] et des revêtements hybrides organiques/inorganiques, préparés à partir du GTMS [3-(glycidyloxy)propyl]triméthoxysilane, GMDES [3-(glycidyloxy)propyl] méthyldiéthoxysilane, poly(oxypropylène) de poids moléculaires variés et dont les extrémités se terminent par des groupes amino (Jeffamine D-230, D-400 et T-403) et dans quelques cas par la silice colloïdal, ont été préparés et caractérisés. On a choisi l’acide chlorhydrique en tant que catalyseur pour le procédé sol-gel et une mélange eau/propan-2-ol comme solvant La structure, la morphologie, et les propriétés mécaniques de ces systèmes qui résistent aux eraflures ont été étudiées par le moyen d’analyses mécaniques statiques et dynamiques, de la diffusion x aux petits angles, de la spectroscopie NMR et de la microscopie force atomique. Les revêtements étaient tout à fait transparents et incolores, ayant la surface lisse. Ils ont manifesté des propriétés mécaniques pertinentes.ZusammenfassungHybrid organische/anorganische Beschichtungen und freistehende Films aus GTMS [3-(Glycidyloxy)propyl]trimethoxysilan, GMDES [3-(Glycidyloxy)propyl]methyldiethoxysilan, Poly(oxypropylen) von verschiedenem Molekulargewicht, die mit Aminogruppen wie Jeffamine D-230. D-400 and T-403 endverkappt sind, und in einigen Fällen aus kolloiden Silikaten, wurden hergestellt und characterisiert. Wir verwendeted Salzsäure als Katalyst für den Sol-Gel Prozess und eine Mischung aus Wasser und Propan-2-ol als Lösungsmittel. Wir studierten die Struktur. Morphologie und mechanischen Eigenschaften dieser kratzfesten Systeme durch statische und dynamische mechanische Analyse, Kleinwinkel-Röntgenverteilung, NMR Spektroskopie und Atomkraftmikroskopie. Die Beschichtungen waren völlig transparent und farblos mit einer glatten Oberfläche, und zeigten geeignete mechanische Eigenschaften.

Comparison of Environmentally Friendly, Selective Polyurethane Catalysts

Selected commercially available amines, including N-substituted morpholines, were evaluated as single catalysts and as catalyst mixtures for polyurethane foam preparation. The motivation was the search for economically and environmentally attractive replacements of “classical” catalysts, like diazabicyclooctane, dibutyltindilaurate, and N,N-bis(2-dimethylaminoethyl)methylamine. Especially interesting was replacing dibutyltindilaurate, and also the possibility of using reactive catalyst derivatives that would be incorporated into polyurethanes, thus reducing the content of volatile organic compounds in the polymer. The catalysts were tested on a α,ω-polybutadienediol + toluenediisocyanate-based system. In some experiments, toluenediisocyanate was replaced by the more reactive and environmentally friendly 4,4′-Methylenebis(phenylisocyanate) and polybutadienediol by polypropyleneglycol.

Strength, elasticity and failure of composites with pyrolyzed matrices based on polymethylsiloxane resins with optimized ratio of D and T components

Two mixtures of T and D siloxane monomeric components labelled as TxDy (molecular ratio x:y equal 3:1 or 4:1) were chosen as matrix precursors for manufacturing Nextel720 reinforced unidirectional composites which, after pyrolysis at 1000 or 1100°C, revealed good endurance in an oxidizing environment up to 1500°C. Vickers hardness of the heat treated (1000–1500°C) samples of pyrolyzed matrices T3D1 and T4D1 are mutually similar (1100–1400 HV0.2) and reach their maximum between 1200–1300°C. Flexural strength of the pyrolyzed composites is 150–170 MPa and 170–250 MPa for T3D1 and T4D1, respectively. After annealing 3 h in air at 1200–1300°C, the strength slightly decreases but similar treatment at 1500°C yields strengths exceeding those of the pyrolyzed material. Shear modulus of the pyrolyzed T4D1 composite is roughly twice that of the T3D1 one (15 GPa vs. 8 GPa) and both increase sharply to 22–25 GPa after annealing at 1500°C, which manifests substantial improvement of the matrix properties. Fracture toughness of the composites, as measured by chevron notch test at RT, 550°C, and 1100°C, yields 4–5 MPa.m−1/2 for T3D1 and 3–4 MPa.m−1/2 for T4D1. For both composite types, the fracture toughness drops by 1 MPa.m−1/2 when measured at 550°C, which can be attributed to suppression of fibre pull-out due to stress state changes caused by the coefficient of thermal expansion (CTE) mismatch. Fracture surfaces generated during flexural tests of the annealed samples reveal decreasing occurrence of pullout towards the highest annealing temperature.

Chitosan–Oligo(silsesquioxane) Blend Membranes: Preparation, Morphology, and Diffusion Permeability

Preparation of the blend chitosan (CHI) membranes containing polyhedral oligomeric silsesquioxane (POSS) derivatives was investigated. POSS derivatives such as (3-aminopropyl)isobutyl-POSS (amino-POSS), [2-(3,4-epoxycyclohexyl)ethyl]isobutyl-POSS (epoxy-POSS), and octa(tetramethylammonium)-POSS were used. The blend CHI–amino-POSS membranes were predicted to be the most porous due to having the weakest interactions between the components in the blends. The CHI–epoxy-POSS blend membranes were assumed to be more dense owing to chemical binding of the chitosan amino groups with the epoxy groups of POSS. Studies of membrane morphology and diffusion permeability support these predictions.

Properties of modified polysiloxane based ceramic matrix for long fibre reinforced composite materials

Abstract The main goal of the work was to prepare a cost effective and simple to preform high temperature matrix for composite materials. To fulfil expectations, it was necessary to optimise the design of the composite to have an optimal fibre–matrix interaction. A number of modified polysiloxane resins were studied in various steps of heat treatment. This contribution deals with changes in the behaviour of the matrix as a stay alone material. This knowledge enables the optimisation of composite properties. A fully instrumented indentation technique for the determination of reliable parameters characterising the microstructural changes was used. The fracture behaviour of the prepared composite matrixes was evaluated in terms of indentation cracks. Both optical and scanning electron microscopies were employed in microstructural observations and fracture mechanism qualification.

Role of Pyrolysis Conditions on Fracture Behaviour of Fibre Reinforced Composites

Fracture response of matrix prepared by pyrolysis of polysiloxane resin used for composite reinforced by long fibres was the main goal of this contribution. A set of composites with matrix prepared by partial pyrolysis of polysiloxane resin was studied. An effect of pyrolysis temperature on the composite behaviour and fracture resistance was monitored. An optimal procedure of pyrolysis was established. Heat treatment at 1550°C in air atmosphere was conducted on fully pyrolysed matrix to explore its high temperature potential. Determination of reliable parameters characterising microstructural changes in the matrix by instrumented indentation technique was used. Both optical and scanning electron microscopy was employed in microstructural observations and fracture mechanism qualification. Observation of indents and associated cracking caused by microstructural changes as well as 3D surface reconstruction using confocal microscopy was employed.

Thermal stability of segmented polyurethane elastomers reinforced by clay particles

The aim of this work was to determine the influence of clay nanoparticles on thermal properties of segmented polyurethanes based on hexamethylene- diisocyanate, aliphatic polycarbonate diol and 1,4-butanediol as chain extender. The organically modified particles of montmorillonite and bentonite were used as reinforcing fillers. The structure of elastomeric materials was varied either by diol type or chain extender content. The ratio of OH groups from diol and chain extender (R) was either 1 or 10. Thermal properties of prepared materials were determined using modulated differential scanning calorimetry (MDSC). Thermal stability of obtained elastomers has been studied by simultaneously thermogravimetry coupled with DSC. The glass transition temperature, Tg, of soft segments for all investigated samples was about -33°C. On the basis of DTG results, it was concluded that obtained materials were very stable up to 300°C.

Fracture response of SiOC-based composites on dynamic loading:

The fracture resistance to the dynamic loading of composites based on partially pyrolysed SiOC glass reinforced with basalt fibres was investigated using an instrumented impact test. The three-point bend loading configuration of the specimen bars prepared from the composite plate was used. Evolution of the matrix during the pyrolysis plays a key role in creation of bonding between the matrix and fibres, which was in the form of woven fabrics. Different temperatures of pyrolysis were applied in order to determine their influence on the fracture behaviour during impact tests. The high speed camera was employed to observe fracture response to impact loading during the fracture process. The temperature range for pyrolysis was chosen from 600 to 800℃ with the step of 50℃. The partial melting of basalt fibres occurred at temperatures above 800℃. Observation of fractographic features on the fracture surfaces was performed using scanning electron microscopy.