Blends aus Polyvinylchlorid und chloriertem Polyäthylen. II. Morphologie von Blends aus Polyvinylchlorid und chloriertem Polyäthylen

Blends of poly(vinyl chloride) (PVC) and chlorinated poly(ethylene) (CPE) form a high impact polymer multiphase system. Characterization of this system by electron microscope becomes possible by a new pretreatment procedure of the polymer blend. The investigation of the morphology by this method shows the initial separation of secondary PVC particles (50–200 μm) into primary PVC particles (0,1–1 μm) by the soft CPE-phase. Due to the stability of the primary PVC-particles an interpenetrating network of the two phases is formed dependent on temperature and shear conditions of the melt Above a specific temperature PVC primary particles melt and the interpenetrating network is transformed into a system of fine dispersed CPE-particles in a PVC matrix Similar results are obtained in the system PVC/poly(ethylene-co-vinyl acetate) and PVC/poly(methyl methacrylate-co-butadiene-co-styrene).     

Blends aus polyvinylchlorid und chloriertem polyäthylen. III. Untersuchungen von dynamischen eigenschaften,schlagzähigkeit,transparenz und fließverhalten

The modul of the polymeric two phase system poly(vinylchloride)/chlorinated poly(ethylene) is dependent on manufacturing conditions during melt blending. We have compared experimentally determined moduls of these blends with calculated moduls according to the models of Davies and Nielsen. The calculated moduls are in agreement with morphological findings by electron microscopy. An interpenetrating network of the two phases or a sphere-in-matrix morphology is found dependent on concentration and on manufacturing conditions during melt blending. Optical properties of the modified PVC were determined by light scattering. Correlation of impact properties of these blends with morphological observations confirms the interpenctrating network structure as optimal to achieve good mechanical properties. This morphology has also the lower melt viscosity compared to the spherematrix-morphology. These rheological results are compared with the particle flow of PVC being demonstrated with two samples of emulsion PVC.     

Polymerisation von Vinylchlorid bei Atmosphärendruck. 2. Chemische und spektroskopische Methoden zur Charakterisierung von U-PVC

PVC, which was polymerized at atmospheric pressure (so called U-PVC) contains relatively high concentrations of defects contrary to normal PVC. The number of chain scissions in U-PVC determined by ozonolytic cleavage resulted in values between 0.026 and 0.058 per 100 monomer units (100 VC). The determination of allylic and tertiary chlorine was done by selective reaction of U-PVC with phenol and NMR-spectroscopic investigations of the phenolized polymers. The average ‘labile chlorine’ content amounts to 0.65/100 VC. Hydroxyl radicals formed during the decomposition of the initiator (K₂S₂O₈) resulted in alcoholic endgroups in U-PVC, which were detectable in the IR-spectrum at 3580 cm^?1. The termination with hydroxyradicals also led to structures at the chain ends changing into ß-chloraldehyde groups accompanied by HCl-elimination. The corresponding signal in the IR-spectrum appeared at 1720 cm^?1. U-PVC raw material contained about two branch points per 100 VC. The CCl₄ extracts of the same polymers revealed the ten-fold content of branching. The olefinic structures ? CH?CH? CHCl? and ? CHCl? CH?CH₂ were determined by NMR-spectroscopy. The concentrations of each ranged from 0.25 to 0.3/100 VC. A typical double bond for U-PVC at the chain ends represented the structure ? CH?CH? CH₂Cl, which was preferably present in the low molecular weight material.     

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.     

Reststabilität von verarbeitetem Polyvinylchlorid

The residual stability of a PVC-compound, stabilized by a solid stabilizing agent, was measured by degradation experiments in bulk under pure nitrogen at 180°C. Several samples of different processing times were prepared by thermomechanical treatment on an extruder. Investigations of the residual stability showed an increasing tendency after the first runs, and then a decrease in stability. The same experiments were performed with a plasticized PVC-compound. Instead of an increase of the residual stability in the beginning of the thermomechanical treatment, a continuous decrease was observed. The same result was found by application of a liquid stabilizing agent to unplasticized PVC. Thus, maximum initial stability is found in the case of plasticized PVC and with liquid stabilizers in unplasticized PVC. In contrast to this result maximum initial stability of PVC, stabilized by a solid stabilizer, was obtained only after several runs on the extruder. This phenomenon can be attributed to a better homogeneity of the stabilizer and the polymer, which is effected by gelation of the PVC by the thermomechanical treatment on the extruder. If the investigation of the residual stability is measured after each run by degradation in a solution of ethylbenzoate the nonplasticized PVC-compound shows maximum stability at the beginning of the experiment. This result leads to the conclusion that the stability of a PVC-compound does not only depend either on the kind or on the amount of the applied stabilizer. To ensure the optimal efficiency of the utilized amount of stabilizer it is necessary to secure a maximum of homogeneity between stabilizer and polymer from the very beginning. Therefore it is of great importance t o the estimation of the residual stability of a PVC-compound after processing to make sure of maximum homogeneity between stabilizer and polymer.     

Über die hitzestabilisierung von PVC durch blei-, barium- und cadmiumoctoat

The following reactions between carbonic acid salts of bivalent metals as heat-stabilizers and PVC take place during heat-treatment:

• Chemical HCI-bonding by stabilizers (HCI-acceptance);
• esterification of isolated allylic chlorine atoms in the polymer chains, starting from a complex formed by stabilizer molecules and labile chlorine atoms:
• the stabilizer inhibits formation of longer polyene sequences by exchange reactions of the allylic chlorine atoms with the ester groups of the stabilizer.

Reaction (a) prevents an autocatalytic acceleration of the HCI splitting off by HCI. Reaction (b) eliminates ?labile”? chlorine atoms of the polymer which are responsible for the thermal instability of PVC. Reaction (c) prevents the formation of longer polyene sequences, which absorb in the visible range of the spectrum.     

Der einfluß der luftfeuchte bei der verfärbung von PVC während der bewitterung und bei der anschließenden dunkellagerung

The influence of humidity on the light-fastness and the dark time yellowing of white PVC and special changes of the irradiated surfaces are described. The results show, that the boundary surface climate at the irradiated specimen surfaces has a decisive influence on the ageing results.     

Einfluß des Tiefziehens von Kunststoff-Folien auf deren Wasserdampfdurchlässigkeit

Influence of Deep-Drawing of Plastic Foils on the Water-Vapour-Permeability The carriergas method for measuring the water-vapour-permeability (WVP) of foils has been modified for measuring the WVP of tubs. With PVC tubs and PVDC-coated PS tubs it is shown, that by deep-drawing the water-vapour-permeability of a foil is not necessarily increased to an amount, which corresponds to the decrease of material thickness during deep-drawing.     

Kunststoffe in der Milchwirtschaft — eine kritische Studie,V. Mitteilung: Zur Reinigung und Desinfektion von Kunststoffoberflächen 1. Teil: Spezielle Gegebenheiten

Plastics in the Dairy Industry — A Critical Study V: Cleansing and Disinfection of Plastic Surface, Part 1: Special Characteristics Plastic articles are suitable for repeated use in direct contact with food-stuffs, provided the former can be maintained properly clean and low in germ-content. Uptil now the plastic surfaces were cleansed empirically, based purely on the experience gathered from conventional materials. The difficulties arising hereby result from the special requirements which the plastics, limited by their specific properties, set on their cleansing solutions and cleaning processes. As against the metals, the plastics do not corrode, however, they are etched easily and are partly not very thermostable. Measurements of angle of contact have shown that the adhesion of fatty impurities on PVC and polyethylene is stronger than the corresponding adhesions of cleansing solutions, hitherto employed for glass and metal surfaces. Soft PVC retains water in contact with cleansing solutions; the extent of liquid retention being dependent on the quantity as well as nature of the plasticizer and on the temperature.     

Untersuchungen und Betrachtungen zur Anwendung von Kunststoffen für Lebensmittel XII: Zur Auswanderung monomerer Weichmacher aus PVC-Milchschläuchen in Reinigungslösungen

Investigations and Observations on the Application of Plastics in Foods XII: Migration of Monomeric Plasticizers from PVC Tubes into Cleansing Solutions The transfer of a few monomeric plasticizers from PVC milk tubes into cleansing solutions can be quantitatively detected by means of the analytical procedure given. It could be thus established that cleansing solutions of various compositions differ from each other in their extracting action on soft PVC. Milk tubes whose internal surface becomes brittle due to unsuitable cleansing agents can not be adequately cleaned because of the rough surface. Thus the quality of the milk flowing through them is impaired.     

Gasdurchlässigeit von mit Hexamethylen-bis-methyloldihydroxyäthylenharnstoff vernetztem Zellglas. I. Synthese von Hexamethylen-bis-methyloldihydroxyäthylenharnstoff und Hexamethylen-bis-methyloldihydroxyäthylenharnstoff

The synthesis of two compounds, believed to be new, is described, which are partculary suitable for crosslinking of cellophane: Hexamethylen-bis-dihydroxyethyleneurea [(CH₂)₆ bis-DHÄH] = 1,6 bis-[4,5-dihydroxy-2-imidazolidinone-1-yl]-hexane (I) and hexamethylene-bis-methyloldihydroxyethyleneurea [(CH₂)₆ bis-MDHÄH] = 1,6 bis-[3-methylol-4,5-dihydroxy-2-imidazolidinone-1-yl]-hexane (II). (I) was prepared by addition of glyoxal to hexamethylenediurea. since (I) is very soluble in water and not crystallizable the byproducts and remainders had to be removed by a special ion-exchange method and by column chromtography. The same operation was applied to the purification of (II). Compouunds (I) and (II) have been checked by analysis of nitrogen and N-methylol groups, by molecular weight determinations and IR-spectra. The reaction-optimum was found by controlling with thin layer chromatography. Practically a 100% conversion was obtained with the addition of glyoxal (I) and a 95% conversion with the methylolation (11) under these conditions, either related to their initial ureas.     

Analyse von Ablagerungen auf Werkzeugoberflächen (Plate-out) bei der Extrusion von PVC

An analytical method to determine the composition of the plate out on different tool parts during PVC extrusion is described. The method was developed by the initial compound of a formulation causing plate out. The single components were separated by solvent extraction of the materials with tetrahydrofurane (THF). The parts insoluble in THF (TiO₂, CaCO₃, etc.) were determined gravimetrically and the single components were identified by chemical and spectroscopic methods (atomicabsorption spectroscopy, X-ray fluorescence, mass spectroscopy). The soluble parts (PVC, plasticizer, lubricant, etc.) were identified by gel permeation chromatography and determined quantitatively by NMR-spectroscopy.     

Vergleich von thermisch und photolytisch ausgelöstem Abbau von PVC-Preßlingen und -Folien

Comparative investigations of PVC discs and foils concerning their thermal and photolytical behaviour showed an expiration of thermal degradation in the mass, whilst the photo processes injure only the surface of a sample. The investigations of polymer samples with different masses have demonstrated a constant rate of thermal dehydrochlorination in nitrogen, which was not influenced by the polymer mass. The degradation experiments in air resulted in an increased HCl-elimination with increasing degradation time. Oxidation reactions which occur in the presence of air cause an accelerated degradation and therefore the dehydrochlorination reaction is appointed as an additional reaction and not in competition with the HCl-elimination process. The influence of UV-light on PVC-discs and foils efforted a much higher dehydrochlorination rate; the energy of the rays is able to stimulate all types of chlorine atoms at the surface. The photolytical injury of the surface increased with degradation time resulting in a decrease of the degradation rate. The degraded and cross-linked material is insoluble in all solvents.     

Farbmetrische Kennzeichnung der Verfärbung von PVC nach thermischer Belastung

The discoloration of PVC which is observable with increasing thermal treatment has been determined by measuring the colour of samples from four different compounds. It could be shown that the thermal stability of a PVC compound can be characterized by determining the chromaticity coordinate z as a function of the milling time of the samples. Moreover a simple explanation of the typical hue shift from yellow to orange or red, that is associated with the thermal degradation of PVC, could be derived. This hue shift can be explained by assuming the existence of a single chromophore whose concentration increases with increasing thermal treatment of the samples.     

Einfluß von zusatzstoffen auf die wärmestabilität von auf PVC basierenden systemen

The instability of systems on PVC basis may be attributed to physical and chemical phenomena. The stability of the system is basically influenced by the oxidation stability of the plasticizers. The volatility loss in plasticizer is only partially due to physical processes. During ageing, oxidation and degradation processes take place to a minor or major degree, or exclusively, depending on the structure of the plasticizer. These processes may be affected in their order of magnitude by the stabilizers and fillers present in the system.     

Zum mechanismus der thermischen abspaltung von chlorwasserstoff aus polyvinylchlorid. 5. Mitt.: Über die verteilung der polyensequenzlängen in thermisch abgebauten technischen polyvinylchloriden und in anwesenheit stabilisierend wirkender substanzen

The rates of dehydrochlorination of commercial poly (vinyl chlorides) and the distribution of the lengths of the resulting polyene sequences may vary widely depending on the origin of the polymer. – In the presence of diphenyllead dichloride the rate of dehydrochlorination is increased, while the resulting discoloration is less intense compared to that of pure poly (vinyl chloride) because of a shift of the polyene sequence lengths distribution. Genuine stabilizers, on the other hand, effect retardation in dehydrochlorination as well as a shift of the sequence lengths distribution towards shorter polyene sequences. The causes for this behavior of admixed stabilizers using lead and cadmium octoate as examples as well as of internally stabilized PVC are discussed.     

Untersuchungen zur Feinstruktur des PVC,IV. Ermittlung der Struktur von niedermolekularem PVC durch Kombination von Hydrierung, 1H- und 13C-NMR-Spektroskopie

By methanol extraction of bulk PVC 0,07% PVC of molecular weight 1500 is received, which can be hydrogenated in chloroform selectively. By combination and comparison of classical analysis, ¹H- and ¹³C-NMR-spectroscopy of the unhydrogenated and hydrogenated methanol extracted PVC of molecular weight 1500 per molecule can be determined. The remaining chain ends predominantly consist of ClCH₂CHCl? and in smaller proportion of ClCH₂CH₂-groups. It is supposed that the results detained with the PVC of M_n = 1500 are valid likewise for the original PVC of M_n = 30000.     

Zur abhängigkeit der mechanischen eigenschaften von thermoplasten von ihrer thermischen vorgeschichte

K.-H. ILLERS has recently shown that the mechanical properties of PVC foils can be considerably influenced by annealing the material at a temperature some-what below the glass transition. This effect ist due to the fact that, in general, at the glass temperature a relative high hole concentration is frozen in which can be diminished by annealing the polymer glass. The variation of the hole concentration during the annealing process was measured by ILLERS with the aid of a new calorimetric method. The purpose of the investigation presented here was to continue ILLERS' measurements and in particular to complete them with regard to the mechanical properties. For this reason tensile tests in the speed range between 10?3 and 1 cm/s and biaxial impact penetration tests were carried out, using specimens cut from a sheet of PVC without plasticizer and annealed for differently long times. It was found that the position of the brittle-tough transition between times until fracture from 10 to 1000 s, caused by a certain molecular relaxation mechanism, is not influenced perceptibly by the hole concentration. If the time until fracture ist shorter than the transition time, or with other words, if the strain rate is sufficiently high, the extensibility of the specimens does not depend very much on the hole concentration. On the other hand the fracture stress, i. e. the strength of the sheet, distinctly increases in this region if the hole concentration decreases. Above the transition, i. e. at long times or low strain rates, the fracture stress is nearly independent of the hole concentration whereas the extensibility strongly decreases with decreasing hole concentration. This means that the sheet material, when being annealed, is improved (reinforced) in the brittle region and deteriorated (brittled) in the tough region. The above-mentioned experimental results were interpreted qualitatively. Furthermore their technical consequences were pointed out with regard to the investigated material as well as to other thermoplastic materials.     

Eigenschaften und Wirkungen von Calcium-verseiften Palmfettsäuren im Verdauungstrakt von Wiederkäuern

Properties and Effects of Ca-Saponified Fatty Acids of Palm Oil in the Digestive Tract of the Ruminant Experiments in vitro applying the Rumen Simulation Technique (RUSITEC) and experiments in vivo with adult wethers and fistulated sheep were conducted to evaluate the effects of Ca-saponified palmoil fatty acid fat supplementations on digestive and physiological parameters in ruminant metabolism. There were only negligible effects of total volatile fatty acid concentration, digestibility of dietary fibrous components (ADF, NDF), retention time of rumen fluid and small feed particles during fat supplementation periods. Numbers of protozoa, ammonia concentrations, cellulolytic activity and the acetate/propionate ratio were however reduced by increasing tat supplementations. The ether-extractability of fatty acids was higher after incubation for several hours and in favour of more unsaturated fatty acids. The extractability of in situ (Nylonbag Technique) applicated Ca-saponified fatty acids was lower for adapted sheep than for sheep fed a standardized basal ration without fat supplementation.