Thermofraktographie zur Schnellanalyse von Kunststoffen. 2. Mitt. Identifizierung von Phenolharzen

Thermofractography is suitable for the rapid identification of phenolic resins. 3–4 mg of the material to be investigated are heated in the temperature gradient of 150–450°C. The thermofractogram shows the free phenols of the resin in the range of 150–250°C. The phenols developing through thermolysis from the condensation products appear, depending on the corresponding initial phenol, in the range of 300–450°C. The efficiency of the method is demonstrated on several novolaks and phenolresol.     

Identifizierung von Polymeren in kosmetischen Produkten II: Spektrometrische Analytik von Kunststoffen

Identification of Polymers in Cosmetic Products II: Spectrometric Analysis of Plastics Synthetic polymers are increasingly used in cosmetics as film-forming agents, as viscosity and moisture regulators and as dispersion stabilizers. Their detection by precipitation and colour often is tedious and not unambiguous. In contrast to these methods, infrared, nuclear magnetic resonance and mass spectrometry frequently permit a rapid and detailed characterization of unknown plastics w. r. t. their composition and microstructure. The efficiency of these methods in the analysis of plastics is demonstrated and the spectra of some polymers and copolymers being essential for cosmetics are compared and discussed.     

Calorimetrische Untersuchung der Vernetzung von Epoxidharzen

Reaction enthalpies of commercial epoxide resins crosslinked with primary, secondary or tertiary amines, anhydrides, a (BF₃) amine complex, respectively, were determined by differential scanning calorimetry. The accuracy of the ΔH_R-values is 2,5–3%. If the initial state of the reaction mixture is homogeneous and fluid and there is no three-dimensional network in the final state, enthalpies of -143 kJ/mol are determined. Reactions sometimes start at room temperature, so reaction enthalpies must be extrapolated. If the initial state is glassy or cristalline, reaction enthalpies of -100 to -129 kJ/mol are determined. Addition of a swelling agent results in higher values of ΔH_R. It is concluded, that for a complete reaction the above mentioned value is attained.     

Zur kinetik der Vernetzung von Epoxidharzen

The crosslinking of epoxy resins,—phenylglycidylether as a model system as well as monomers and oligomers of diglycidylether of bisphenol A and of hydantoine resins—, with acid anhydride in presence of amine accelerators has been investigated. Experimental methods used were chemical analysis, dilatometry and calorimetry. From the determination of the chemical yield resulted, that crosslinking of epoxy and anhydride is a zero order reaction, but for longer distances of reaction time different rate constants must be used, leading to large differences in the activation energies of the steps of crosslinking. From time dependant deviations of the anhydride conversion yield from stochiometry it was concluded, that at first an intermediate compound originates and the linking of these units in the network determines the second step of crosslinking.     

Studium der Reaktivität von aromatischen Diaminen mit Epoxidharzen

It was found that the deciding factor for the reactivity of aromatic diamines with epoxide resins are basic values of electron structure and chemical reactivity on the end amino-groups. A linear dependence was determined between logarithm of gelatinization time and electron density of the amino-group which was calculated using principles of quantum chemistry. Changes in the structure of aromatic diamines leading to changes of the electron density of amino-group cause a reactivity change of these compounds during polyaddition. This method shows possibilities offered by quantum chemistry in the field of plastics.     

Anwendung der FMIR-Technik zur infrarotspektroskopischem Identifizierung von beschechteten Folien und Papieren

The high efficiency of FMIR-technique by infrared investigations of coated foils, papers and cartons is shown in some examples. In this method the surface of the sample to be investigated which is pressed on both sides of a KRS-5 crystal is scanned repeatedly by the IR-beam. This investigation shows that the reflectance technique yields spectra of higher quality (= resolution + band depth) than the traditional transmittance technique. Moreover the procedure of pressing can be omitted in the investigation of lacquered foils or foils with a smooth surface before recording the spectra. This proved to be necessary according to our results we received by the FMIR investigation of coated papers. Often better spectra of foils are obtained if a FMIR-erystal with 15 reflections is used (angle of incidence 60°). The FMIR-method has the great advantage of simplicity and speed.     

Einfluß der Faserbehandlung auf das Feuchteverhalten von glasfaserverstärkten Epoxidharzen

The strength of glass fiber reinforced epoxy resins can be significantly reduced under exposure to moisture. Besides other factors, the interface between fiber and matrix plays an important role. It is responsible for a proper load transfer between fibers and matrix by coupling effects and significantly affects the moisture behavior of the composite. In the present study, glass fibers were treated with different sizes under defined conditions and embedded in three epoxy matrix systems. The composites were exposed to different moisture conditions. The change of the shear and impact behavior due to moisture was determined. It will be shown that the composites with coupling agent treated fibers are significantly more resistant to moisture than composites with poor fiber/matrix adhesion. Furthermore, it will be shown that also the binder plays an important role if the material is subjected to moisture.     

Methoden zur Herstellung und Charakterisierung von Kunststoffen mit verbesserter Blutverträglichkeit

Tubings of different internal diameter (ID) were prepared from 10 different polymers (CPE, EPDM, ETFE, EVA, LDPE, PP, PTFE, PUR, PVC and Silicone):

• tubings of 4–5 mm ID for in vitro- and ex vivo-blood compatibility tests with human blood,
• tubings of 0.3–0.4 mm ID for ex vivo-evaluations for blood compatibility via measuring the bleeding time after introduction of the tubing into the ear vein of rabbits.

The tubings were surface modified by grafting with N-vinyl-N-methyl acetamide (VIMA). For both the original and the grafted tubing correlations were established between the physical characterization (degree of grafting, critical surface tension, ESCA, FT-ATR-IR, SEM) and the in vitro and the ex vivo blood compatibility tests. The in vitro blood compatibility tests consist of an incubation of 4–5 mm tubing with citrated human blood and subsequent determinations of clotting parameters. The human ex vivo blood compatibility tests were performed on human arm veins followed by investigation of the internal surface of the tubing. The results could be correlated with the in vitro tests with human blood. A comparison with conventional tubing on the market (PVC and Silicone) as a standard shows, that PTFE/VIMA, LDPE/VIMA, PUR and EVA have better blood compatibility properties than the standard whereas untreated PTFE and LDPE are ranked below the standard.     

Thermofraktographie – eine neue mikroanalytische Schnellmethode zur Untersuchung von Lipidgemischen

Thermofractography – A Novel Microanalytical Method for the Rapid Analysis of Lipid Mixtures New possibilities now exist for the rapid analysis of lipid mixtures in micro-scale through fractionated carrier gas distillation in direct coupling with the thin-layer chromatography (= Thermofractography). To begin with, the behaviour of pure substances in the temperature gradient 50°–450°C was investigated. It was observed that numerous compounds, which are otherwise separable only via vacuum distillation, pass over with the carrier gas at normal pressure. In this connection, the thermolysis of such compounds was also investigated. Practical cases of application, e. g. fats and oils, mayonnaise, dairy products, chocolate base are given and other possibilities are discussed.     

Produkte der Dimerisierung ungesättigter Fettsäuren X: Identifizierung von Estoliden in der Anfangsphase der Dimerisierung

Products of the Dimerisation of Unsaturated Fatty Acids X: Identification of Estolides in Early Phase of the Dimerisation Dimeric fatty acids, obtained by dimerisation of the conjugated fatty acid (mixture of 9,11-Octadecadienoic acid and 10,12-Octadecadienoic acid) in presence of the catalyst molybdenum pentachloride and tin dichloride, could be separated after methylation with diazomethane. The isolated fraction of methyl-9-octadecanoyloxy-octadecanoat resp. methyl-10-octadecanoyloxy-octadecanoat and methyl-9-octadec-9-enoyloxy-octadecanoat resp. methyl-10-octadec-9-enoyloxy-octadecanoat was characterized. It could be shown that these estolides can be saponified to stearic acid, oleic acid and 9- resp. 10-hydroxyoctadecanoic acid. Thus saponification can serve as an unambiguous proof of estolide components. Analogous estolides could be identified in the early phase of the clay-catalyzed dimerisation of oleic and linoleic acid. The detection of estolides shows that at low dimerisation temperature at first hydroxy fatty acids are formed which are subsequently esterified with unsaturated fatty acids. In the final products of the dimerisation estolides are absent, because their formation is suppressed by higher temperatures.     

O-Methylierung von tert.-Alkylbrenzcatecholen. Analytische Methode zur Bestimmung der Zusammensetzung von Produktgemischen und Synthese-variante zur Herstellung von 4-tert-Alkylveratrolen

O-Methylation of tert-Alkylpyrocatecholes. Analytical Method for Determination of the Content of Product Mixtures and Way for Preparation of 4-tert-Alkylveratroles The O-methylation of tert-alkylpyrocatecholes with dimethylsulfate leads to a mixture of substituted guaiacoles 6/7 , 9/10 and veratroles 5 , 6 which are separated by gas/liquied-chromatography for analytical purposes. It is also possible to prepare 4-tert-alkylsubstituted veratroles 5 with good yields in this way. On the other hand, the alkylation of veratrole was only successful with lower tert-alkanols or alkenes. Long-chained tert-alkanols fail in this reaction. The analytical and spectroscopical data of some new 4-tert-alkylveratroles 5a—g are given.     

Identifizierung der Sterine in verschiedenen Lipidgemischen von Schweinen

Identification of Sterols in Various Mixtures of Lipids of Swines The sterol composition of lipid mixtures of blood serum, adrenals, intestinal fat, and back fat of swines was studied. The main sterol is cholesterol, which constitutes 97-99% of the mixture. The remaining sterols, which occur in amounts less than 0.1%, were identified by thin-layer chromatography and gas chromatography on 4 different columns of varying polarity. These are mainly intermediates in the biosynthesis of cholesterol, namely, Δ7-cholestenol, desmosterol, 4-methylchole-sterol, 4-methyl-Δ8(9)-cholestenol, 4,4-dimethylcholesterol, 4,4-dimethyl-Δ8(9)-cholestenol, lanosterol, and dihydrolanosterol. A further sterol with a Δ5,7 double bond, presumably Δ5,7-cholestadien-3β-ol, was recognized from its characteristic UV-absorption. Cholestanol was also present in all samples. Plant sterols could not be detected in the sterol mixtures. Oxidation products of cholesterol, such as Δ4-cholesten-3-on, 7-hydroxy-cholesterol, 7-ketocholesterol, and Δ3,5-cholestadien-7-on were identified. Δ4-Cholesten-3-on is probably formed in vivo, while the others are formed by oxidation of cholesterol during isolation of the sterols.