Volker Rossbach

Copying and manipulating nature: Innovation for textile materials

This paper considers the potential impact of biological approaches such as bio-copying (biomimetics) and biomanipulating (e.g. genetic engineering) on future developments in the field of textiles and, in particular, fibres. If analytical tools for studying biological systems combined with those of materials science are further developed, and higher efficiency and reproducibility of genetic engineering technology can be achieved, the potential for the copying and manipulation of nature for textile innovations will be immense. The present state for both fields is described with examples such as touch and close fastener, structurally coloured fibres, the Lotus effect (for bio-copying), as well as herbicide tolerant cotton, insecticide resistant cotton (Bt cotton), cotton polyester bicomponent fibres, genetically engineered silkworm and silk protein, and spider fibres (for genetic engineering).

THE CARRIER EFFECT IN THE M-ARAMID FIBER/CATIONIC DYE/BENZYL ALCOHOL SYSTEM

Studies with benzyl alcohol and other substances (acetophenone, dimethylacetamide, dimethylsulfoxide) interacting with poly(m-phenylene isophthalamide) fibers have shown that the carrier effect in the dyeing process takes place through a balanced combination of several factors. For a substance acting as a carrier, the distribution equilibrium must be on the side of the fiber. This is the case if the substance has only a limited hydrophilicity, indicated by a low solubility of the carrier in the dyeing liquor. In order to be effective, it is not sufficient that the sorption of the carrier takes place only in the interior of the fiber; it must also take place on the fiber surface. If the carrier layer on the fiber surface is removed, the dye uptake rate decreases. An optimal carrier effect is accompanied by an increase in the degree of crystallinity and changes in the mechanical properties (decreased tensile strength and elongation at break, as well as increased Youngs modulus). When combined with the carrier substance, water is also able to enhance the dye uptake rate (co-carrier). Electrolytes do not influence the sorption of carrier.

Surface activation of non-porous perfluorinated polymers by deposition of silica

Abstract A method to enhance the surface energy of non-porous films of three different types of perfluorinated polymer [polytetrafluoroethylene with and without a perfluorinated modifier and poly(tetrafluoroethylene- co -hexafluoropropylene)] is described. The surface was activated by the deposition of silica, produced in situ from SiCl 4 and water, without any chemical degradation or modification of the polymer bulk. By adding perfluorohexane and 1,1,1,3,3,3-hexafluoroisopropanol as auxiliaries to the SiCl 4 and water in the gas phase respectively, extended silica layers with spherical morphologies could be generated, which were permanently fixed to the films. By use of low voltage scanning electron microscopy (LVSEM) it was shown that the adhesion of the silica to the fluoropolymers is due to its mechanical anchoring, ultimately resulting from the diffusion of SiCl 4 and water into the polymer surface.

Surface modification of polytetrafluoroethylene with tetraethoxysilane by using remote argon/dinitrogen oxide microwave plasma

The use of remote microwave plasma for the polymerization and deposition of tetraethoxysilane on the surface of polytetrafluoroethylene was investigated using a mixture of Argon and dinitrogen oxide as carrier gas. Layers with thicknesses of 0.5-3 μm were obtained, differing in chemical composition, surface energy, and flexibility/ brittleness, depending on the plasma power and both the treatment and aging times. In general, milder treatments and shorter aging times resulted in higher contents of organic structural elements in the layers and greater flexibility and surface energy. Anchoring between the layers and the bulk polytetrafluoroethylene was at least partially caused by fibrils interconnecting the two components. These results were obtained by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy in the attenuated total reflection mode, contact angle measurements, and scanning electron microscopy combined with energy dispersive X-ray analysis.

Dyeing of Anionically-Modified Polyamide Fibers with Cationic Dyestuffs1 Part I: Uptake of the Dyestuff and its Binding1

The physicochemical principles of the dyeing of two polyamide-6 fibers modified with the monosodium salt of 5-sulphoisophthalic acid at pH 1.8 and 4.5 with an oxazonium dye (Astrazon Blue BG, C.I. 51004) and a thiazonium dye (Methylene Blue, C.I. 52015) are described. Measurements of the zeta potential by the flow-potential method have shown that the fibers have a very highly negatively-charged surface as compared with unmodified types. This decisively promotes the adsorption of the dyestuff cations on the fiber. The uptake of the dye can be described by means of the Langmuir adsorption isotherm as an ion-exchange reaction. It follows from the agreement of dyestuff saturation figures and comonomer contents that the dyestuff is bound stoichiometrically by the sulpho groups (pH 4.5; 80°C). Carboxyl groups probably take no part in the dyestuff binding at pH 1.8 and 4.5. The standard values of the heat of reaction have been determined from the temperature dependence of the equilibrium constants for reactions responsible for the dyestuff binding. They show that the dyestuff/fiber bond contains a covalent component, which is probably due to interactions between the sulphonate group and the dyestuff cation.

Quantitative methyl esterification of carboxyl end groups of polyethylene terephthalate

SummaryFor esterification of its carboxyl end groups in heterogeneous phase, polyethylene terephthalate was treated with boron trifluoride/methanol and with diazomethane in chlorobenzene, respectively. Whereas treatment with boron trifluoride/ methanol in some cases was accompanied by polymer degradation, reacting the polyester with diazomethane resulted in complete methyl esterification without any detectable side reaction.

Characterization of Nitro-Substituted Polybenzimidazole Synthesized by the Reaction with Nitric Acid

Abstract Nitro-substituted poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole]s (PBIs) were synthesized by the reaction of PBI with nitric acid in sulfuric acid under various conditions. The number of nitro groups substituted on the aromatic ring of PBI per polymeric unit varied from 1.44 to 3.55 according to the reaction conditions. An increase in reaction temperature and concentration of the nitric acid increased the degree of substitution. The inherent viscosity of the substituted polymer increased as the reaction temperature decreased. When the reaction temperature was 30°C, the inherent viscosity of the polymer increased as the concentration of nitric acid increased. The nitro-substituted PBI exhibited polyelectrolyte behavior in formic acid. The nitro groups substituted on PBI were dissociated when the polymer was heated to 450°C, displaying exothermic behavior, and the decomposition of polymer was proportional to its nitro group content. All nitro-substituted PBIs showed better solubilities in polar apro...

Surface activation of perfluorinated polymers

Abstract The further development of a method to activate the surface of non-porous perfluorinated polymers are described. A closed layer of polysilicic acid was formed on the surfaces of perfluorinated polymers through treatment with SiCl 4 and H 2 O. The layer was firmly anchored to the polymers through a mixed layer composed of polysilicic acid and perfluorinated polymer. The treatment enabled the surface activation of polymer samples independently of their shape and the thickness of the polysilicic acid layer could be influenced by the reaction conditions. The primary structure of the perfluorinated polymer remained essentially unchanged. The first results on the further functionalisation of the modified polymers with silane coupling agents, as the basis for the building of multilayer composites, is described. The system perfluorinated polymer/polysilicic acid/silane coupling agent was characterised using SEM, EDX, XPS, IR, DSC and contact angle measurements, with respect to the surface morphology, chemical composition and activation as well as the distribution of the polysilicic acid on the surface and within the perfluorinated polymer.

Zum thermischen Verhalten von Polyacrylnitrilfasern in Abhängigkeit vom chemischen Aufbau des faserbildenden Acrylnitrilpolymeren

ZusammenfassungDer temperatur-programmierte und isotherme Abbau einiger comonomerhaltiger Acrylnitrilfasern wurde bis maximal 300 °C unter Luft untersucht; dabei wurden die fogenden Ergebnisse erhalten: Bei der temperatur-programmierten Aufheizung korreliert für die untersuchten Polymeren (comonomer-freies und 2-vinylpyridinhaltiges Polyacrylnitril sowie Dralon, Orlon 42 und Orlon 74) der Beginn der thermischen Verfärbung und die Lage des exothermen Peaks im Differentialthermogramm. Durch alkalische Hydrolyse in Polyacrylnitril eingeführre Carboxylatgruppen verschieben den exothermen Peak im Differential-thermogramm nur geringfügig nach tieferen Temperaturen; der Einfluß von Pyridinresten ist dagegen deutlich ausgeprägter. Es wird gefolgett, daß der Grad der Nucleophilität der comonomeren Gruppen einen Einfluß auf die Initiietung der Cyclisierungs-reaktion der Nitrilgruppen hat.Die Übereinstimmung der maximalen, auf die Last 0 extrapolierten Schrumpfungstemperatur mit der Temperatur des exothermen Peaks im Differential-thermogramm wirdals Hinweis auf die Bildung einer gewinkelten leiterpolymer-Struktur gedeutet.Bei der isothermen Thermooxidation von Poly-acrylnitril wird im Bereich von 180–220 °C eine deutliche Abnahme des Farbstoffaufzichvermögens beobachtet, was auf physikalische Veränderungen der Faserstruktur zurückgeführt wird. Eine Verringerung des Anfärbevermögens durch chemische Reaktionen der Carboxylgruppen wird ausgeschlossen.Da im Gegensatz zur thermischen Behandlung bei einer Alkalibchandlung das Farbstoffaufnahmevermögen zunimmt, kann bei bekanntem Farbstoffsättigungswert der unbehandelten Faser auf die Art der Vorbehandlung (thermisch oder alkalisch) rückgeschlossen werden.SummaryThe thermal degradation of some acrylonitrile copolymers in air at temperatures up to 300 °C has been studied, and the following results obtained:For the polymers studied (polyacrylonitrile, poly-acrylonitrile contraining 2-vinyl-pyridine comonomer, and the commercial fibres Dralon, Orlon 42 and Orlon 74) a correlation was found between the temperatur of the exotherm determined by differential thermal analysis, and the temperature at which discoloration became appaten. Carboxylate groups introduced into polyacrylonitrile by alkaline hydrolysis shift this exotherm only slightly to lower temperatures. But the effect of incorporated pyridine moietics is more obvious. That means that the degree of nucleophility is important for the initiation of nitrile group oligomerisarion by comonomers. Agreement was found between the temperature of the exotherms and the temperatures at which maximum shrinkage at zero stress occurred, and it was concluded that shrinkage at this temperature was due to the formation of polymers with an angled ladder structure.Isothermal thermo-oxidation in the temperature range 180–220 °C resulted in a sharp decrease in the uptake of basic dyestuffs. Since dye uptake was increased by treatment with alkali, this different behaviour enabled damage resulting from thermal oxidation or alkaline hydrolysis to be distinguished.The reduced uptake of dye following thermal treatment cannot be explained by chemical reaction of the carbonyl groups but is due to alterations of the physical polymer-structure.

The Impact of Natural Fiber Science on Manmade Fiber Technology1

Analytical methods are described for the chemical characterization of polyamide and polyester fibers. Their origin from natural fiber chemistry is elucidated. End-group data (amino, acylated amino, and carboxyl groups), number-average molecular weights and breaking stress values are given for commercial polyamide fibers produced by several manufacturers. Amino groups were deter mined with 1-fluoro-2,4-dinitrobenzene, using a new technique. Besides its specifity, this chemical method allows the differentiation of primary and secondary amino groups and their determination in the presence of each other. A related topic is the detection of heat damage in polyamides. Heat treatment leads to the formation of basic groups, which can be distinguished spectroscopically from amino groups after reaction with 1-fluoro-2,4-dinitrobenzene. As a practical application the elucidation of the damage of a nylon needle felt, used in a paper machine, is described. Hydrazinolysis was applied for the determination of carboxyl end groups. The use of this new analytical method for polyester studies is described, also its application on several commercial polyethylene terephthalate fibers. Furthermore, hydrazinolysis allows the determination of the amount of 5-sulfo-isophthalic acid in acidic modified fibers. Values ob tained are confirmed by determination of the uptake of a basic dyestuff (methylene blue). The importance of end- group analysis is stressed by its application to the analysis of hydrolytically damaged polyester fibers. The increase in carboxyl groups was determined for steam-treated modified and unmodified polyethylene terephthalate. Results concerning the analysis and generation of oligomers in polyester are added.