Thermogravimetric analysis of PVC/ELNR blends

The thermal behaviour of a series of solution-cast blends of polyvinyl chloride/epoxidised liquid natural rubber (ELNR) of different mole percentage of epoxidation has been examined using thermogravimetric analysis. Thermal degradation is found to occur through a two-step route in which the first step corresponds to the dehydrochlorination of PVC to form a polyene and the second step is attributed to the decomposition of the ELNR and the polyene. Introduction of 20 and 50 mol% of epoxy group into the liquid NR is found to enhance the thermal stability of PVC. Probable mechanisms of degradation have been suggested on the basis of the kinetic analysis of the degradation studies. It is found that the mechanism is influenced by the epoxy content of the blend system. Activation energy for the degradation and the entropy change have also been reported.     

Plastic deformation kinetics for glassy polymers and blends

Measurements of the plastic deformation kinetics for several glassy (PS, PC, PI-polyimide, PET, epoxy-amine network), semi crystalline polymers (PBT, PET) and blends (ABS, PC:ABS, PC: PBT) were performed for the unidirectional compression loading conditions by using constant temperature deformation calorimetry. The experiments have permitted us to follow the changes of the mechanical work (A), the heat of deformation (Q) and differences between these quantities, i.e., internal energy (U) stored in samples during their loading and unloading. Experiments have shown that the large portion (45–85%) of the mechanical work of deformation (A) is converted to heat (Q). The rest ofA is converted to internal energy (U) stored in deformed samples. U is quite high as compared with metals [1,2]. After complete unloading of plastically deformed samples, i.e., samples carrying irreversible atT _def plastic deformation ( _irr ), some amount (U) of stored energy disappeared. The amount of (U and (U) are different for different polymers. All data are analyzed in the framework of the model proposed in [3,4]. The experiments support the deformation model where the plasticity of glassy polymers is the process of nucleation and development of so-called PDs-plastic local shear defects of nonconformational and nondilatational nature.Dedicated to Prof. Dr. W. Pechhold on the occasion of his 60th birthday     

The ternary system H2O–Fe(NO3)3–Co(NO3)2 isotherms 0 and 15 °C

The solid–liquid equilibria of the ternary system H₂O–Fe(NO₃)₃–Co(NO₃)₂ were studied by using a synthetic method based on conductivity measurements.

Two isotherms were established at 0 and 15 °C, and the stable solid phases which appear are the iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), the iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), the cobalt nitrate hexahydrate (Co(NO₃)₂·6H₂O) and the cobalt nitrate trihydrate (Co(NO₃)₂·3H₂O).     

Annealing of Polypropylene/Polyethylene Blends Near to the Melting Points in TMDSC

Annealing experiments have been carried out just below the melting temperature of both polyethylene (LLDPE) and polypropylene (PP) and their blends. The total melting enthalpy measured after the annealing cycle was greater by 10-15% with respect to the value having been measured before it. During the annealing period the heat capacity decreases to a lower value within the first 2-3 min. Heat capacities of PP (either in pure form or in the blends) measured during the heating cycle following the annealing cycle have the same value as during the cooling section. The heat capacities of the LLDPE in the heating cycle following the annealing were those of the preceding heating cycle. The total heat flows in the cooling section following the annealing cycle were greater than those in another cooling cycle at the same temperatures indicating that the crystallisation takes place during the cooling rather than during the annealing periods. The presence of LLDPE decreases the crystallisation temperature of PP. The presence of SEBS in the blend results in a greater crystallisation temperature than that of pure PP. The crystallisation temperature of LLDPE increases with increasing levels of PP. This revised version was published online in July 2006 with corrections to the Cover Date.     

Neue ternäre Käfigverbindungen aus den Systemen Barium–Indium/Zink/Cadmium–Germanium: Zintl-Verbindungen mit Phasenbreite?

New Ternary Clathrate Compounds in the Systems Barium–Indium/Zinc/Cadmium–Germanium: Zintl Compounds with Phase Width? By systematic investigations in the systems barium–indium/zinc/cadmium–germanium we found a couple of new electrovalent ternary compounds with A₈X₄₆ clathrate (I) type structures. They crystallize cubically in space-group Pm3n. For Ba₈In₁₆Ge₃₀ (a = 1 075.8 pm), Ba₈Zn₈Ge₃₈ (a = 1 082.0 pm) and Ba₈Cd₈Ge₃₈ (a = 1 096.0 pm) the structures were verified by X-ray single crystal diffraction data. According to valence and bounding distances the new clathrates should be Zintl compounds. Measurements of the temperature dependence of the electrical resistivity proved, that they are indeed semiconductors. A part of the 2B/3B metal atoms can be substituted by germanium. Charge balance will be retained by creation of vacancies in the A₈X₄₆ type structures. By phase analysis the limits of the composition range were determined as Ba₈In₄Ge₉[]₃Ge₃₀ (a = 1 084.9 pm), Ba₈Zn₄Ge₁₀[]₂Ge₃₀ (a = 1 073.6 pm) and Ba₈Cd₄Ge₁₀[]₂Ge₃₀ (a = 1 082.0 pm).     

Isothermal Degradation of PVC/MBS Blends

The process of thermal degradation of poly(vinyl chloride)/poly(methyl methacrylate-butadiene-styrene) (PVC/MBS) blends was investigated by means of isothermal thermogravimetry in nitrogen. The total mass loss was determined after 120 min. The kinetic parameters of the degradation process were determined by applying two kinetic models: the model which assumes autocatalytic degradation (Prout-Tompkins) and the model of two-dimensional diffusion. It was established that the thermal degradation at lower degrees of conversion (α<0.20) was well described by the former model, but the latter model was applicable at higher degrees of conversion. The thermal stability of blends at a certain temperature of isothermal degradation depends on the blend composition and the shell/core ratio in MBS, and on the adhesion in the boundary layer in PVC/MBS blends. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of Biodiesel and Triacylglycerols in Diesel Fuel by LC

A high performance liquid chromatographic method was developed for quantifying blends of biodiesel (simple alkyl esters of fatty acids) in petrodiesel. The method uses a silica column with an isocratic mobile phase consisting of hexane and methyl t-butyl ether. Separated components were quantitated using either an evaporative light scattering detector (ELSD) or UV detector. Precision of injection and linearity of response of the ELSD and UV detectors over a range of biodiesel-petrodiesel blends [1–30 v/v %] were established by use of standards. The method also can be used for quantitating similar levels of oils or fats (triacylglycerols) in petrodiesel.     

Miscibility and transesterification in ternary blends of poly(ethylene naphthalate)/poly(trimethylene terephthalate)/poly(ether imide)

Miscibility and morphology of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate)/poly(ether imide) (PEN/PTT/PEI) blends were investigated by using a differential scanning calorimeter (DSC), optical microscopy (OM), wide-angle X-ray diffraction (WAXD), and proton nuclear magnetic resonance (¹H-NMR). In the ternary blends, OM and DSC results indicated immiscible properties for polyester-rich compositions of PEN/PTT/PEI blends, but all compositions of the ternary blends were phase homogeneous after heat treatment at 300 °C for more than 30 min. An amorphous blend with a single T _g was obtained in the final state, when samples were annealed at 300 °C. Experimental results from ¹H-NMR identified the production of PEN/PTT copolymers by so-called “transesterification”. The influence of transesterification on the behaviors of glass transition and crystallization was discussed in detail. Study results identified that a random copolymer promoted the miscibility of the ternary blends. The critical block lengths for both PEN and PTT hindered the formation of crystals in the ternary blends. Finally, the transesterification product of PEN/PTT blends, ENTT, was blended with PEI. The results for DSC and OM demonstrated the miscibility of the ENTT/PEI blends.     

Cellulose acetate and polyethersulfone blend ultrafiltration membranes. Part I: Preparation and characterizations

The overall objective of this investigation is to achieve high‐performance membranes with respect to flux and rejection characteristics, with an interplay of blending polymers having desired qualities. Thus, cellulose diacetate and polyethersulfone as candidate materials, in the presence of polyethylene glycol 600 as a pore forming agent, were blended in 100/0, 95/5, 90/10, 85/15, 80,20 and 75/25% compositions using N,N′‐dimethylformamide as solvent and membranes were prepared by the phase inversion technique. Polymer blend composition, additive concentration, and casting and gelation conditions were standardized for the preparation of asymmetric membranes with various pore statistics and morphology. These blend membranes were characterized for compaction in ultrafiltration experiments at 414 kPa pressure in order to attain steady state flux and is reached within 4–5 hr. The pure water flux was measured at 345 kPa pressure and is determined largely by the composition of polyethersulfone and additive concentration. The flux was found to reach the highest values of 66.5 and 275 1/(cm² hr) at 0 and 10 wt% additive concentrations respectively, at 25% SPS content of the blend. Membrane hydraulic resistance derived by measuring water flux at various transmembrane pressure and by using an algorithm was found to be inversely proportional to pure water flux. Water content is estimated by simple drying and weighing procedures and found proportional to pure water flux for all the membranes. The molecular weight cut‐offs (MWCOs) of different membranes were determined with proteins of different molecular weights and found to vary from 20–69 kDa (globular proteins) depending on the PEG and SPS content in the casting dope. Skin surface porosity of the membranes were analyzed by scanning the frozen membrane samples using scanning electron microscopy (SEM) at different magnifications. The surface porosity is in direct correlation to the MWCO derived from solute retention experiments. Copyright © 2004 John Wiley & Sons, Ltd.     

A DSC-Study of Donor/Acceptor Side-Chain Polymers with Flourinated Taper-Shaped Tails

It is shown that insertion in methacrylic polymers of bulky electron donor/acceptor side-groups with taper-shaped flourinated tails promotes a self-organization of the respective side-chain polymers due to the space demands of the bulky D/A side-groups, leading to a columnar hexagonal mesophase. The presence of an Lc-phase is evidenced by DSC and identified by X-ray analysis. The orientation in the respective copolymers and polymer blends is additionally improved by the CT-interaction between the D/A side-groups. An increased packing effect due to this CT-orientation effect is evidenced in DSC by an increase of the respective transition temperatures. CT-interaction is responsible as well for a preferential polymerization of monomeric D/A-complexes leading to copolymers of alternating structures and for a zip-like arrangement along the main chain of the A/D-complexes between the interacting side-groups in polymer blends. Formation of mesophases is even observed in CT-interacting blends between the Lc-D/A side-chain polymethacrylates and the respective amorphous D/A side-chain polysiloxanes.This revised version was published online in November 2005 with corrections to the Cover Date.