Hans-Gerhard Fritz

New developments on the ring opening polymerisation of polylactide

Abstract Polylactides (PLA), biodegradable aliphatic polyesters, produced solely from renewable resources may substitute petrochemically based polymers in a broad range of applications in the near future, if we manage to produce them at lower cost and higher efficiency as nowadays. Possible applications include food packaging for meat and soft drinks, films for agro-industry and non-wovens in hygienic products. The authors developed, based on a new catalytic system, a reactive extrusion polymerisation process, which can be used to produce PLA continuously in larger quantities and at lower costs than before. This extrusion polymerisation process has been developed and tested with laboratory scale machines and the possibilities to extend this polymerisation process to lactide based blockcopolymers have been investigated.

Rheological characterization of thermoplastic starch materials

The rheological characterization of thermoplastic starches (TPS) by using a capillary rheometer includes the research of their flow properties depending on compounding parameters, on types and contents of incorporated additives, as well as on melt temperatures. Based on extensive experimental studies, the viscosity functions of glycerol de-structurized TPS types can be described analytically by the definition of a new combined shift factor, which considers the influence of both melt temperature and additive amount. Wall-slip effects due to specific TPS formulation; were quantified by the application of a modified Mooney procedure.

Compounding procedure, processing behaviour and property profiles of polymeric blends based on thermoplastic poly(ester-urethanes and destructurized starch

This paper describes the compounding procedure for production of blends consisting of thermoplastic poly(ester-urethanes) (TPU) and thermoplastic starch (TPS) as well as their property profiles. These blends were prepared using co-rotating twin-screw extruders. Different process designs were studied and their impact on material properties is discussed. Even if the process design, the process parameters, and the TPU-content remain unchanged, the morphology can be improved by the use of different types of TPS through the adjustment of the viscosity ratio λ 1 . Excellent flat and tubular films can be produced which are promising materials for a variety of applications.

Modification of surface properties of polypropylene films by blending with poly(ethylene-b-ethylene oxide) and its application

The possibility of improving the interfacial adhesion between polypropylene (PP) and polyamide layers (PA) has been investigated by means of addition of commercially available amphiphilic poly(ethylene-b-ethylene oxide) (P(E-b-EO)) block copolymers. These block copolymers were added to the PP matrix polymer in a twin screw extruder as integral additive. The change in surface properties of PP films upon incorporating P(E-b-EO) was investigated in model studies of blends prepared by casting PP/P(E-b-EO) solutions in 1,2-dichlorobenzene onto glass and Teflon Petri dishes, by melt pressing of PP/P(E-b-EO) blends between Teflon foils and glass substrates, or by melt extrusion of PP/P(E-b-EO) mixtures. The surfaces of the blend films were analyzed by attenuated total reflection Fourier transform infrared spectroscopy and water contact angle measurements. It was shown that an enrichment of the block copolymer at the surface of the blend depends highly on the conditions of film preparation and is driven by reducing the interfacial energy between the blend and the contacting medium. Effects of shear rate and residence time during normal processing conditions were also revealed. Blown film experiments with PP/P(E-b-EO) blends and PA were carried out for evaluating the effect of the integral P(E-b-EO) additive on the interfacial adhesion.

Prüfung der Umweltverträglichkeit neu entwickelter Polymerwerkstoffe auf der Basis nachwachsender Rohstoffe durch ein einfaches Testsystem

Mit Hilfe des OxiTop®-Systems konnte gezeigt werden, wie sich verschiedene Polymerwerkstoffe auf Basis nachwachsender Rohstoffe im Hinblick auf ihre biologische Abbaubarkeit und Umweltvertraglichkeit unterscheiden. Der biologische Abbau von beispielsweise flachsfaserverstarkter, thermoplastischer Maisstarke mit Naturfaseranteilen von 10, 15 und 20% lag nach 14 Tagen in der Grosenordnung von nativer Starke. Dabei hat sich gezeigt, das der Flachsfasergehalt keinen signifikanten Einflus auf den biologischen Abbau ausubt, da die Abweichungen bei den Abbaukurven der mit 10, 15 und 20 Gew. % versehenen TPS/Flachsfaser-Verbunde kaum aufzulosen waren. Thermoplastische Starke (TPS) baut dagegen deutlich langsamer als die flachsfaserverstarkte TPS ab, was auf die wassereinleitende Wirkung der Fasern (Strohhalmprinzip) in das Innere der TPS zuruckzufuhren ist. Demnach mus der Fasergehalt eine Grenze uberschreiten, ab der dieser Effekt deutlich zum Tragen kommt. Der Abbau der TPS erfolgte zudem aufgrund der Probenform deutlich langsamer als bei nativer Maisstarke, da TPS als Granulat vorlag, wodurch die spez. Oberflache im Vergleich zu den Maisstarkepartikeln deutlich reduziert ist. PCL/TPS-Blends bauen praktisch unabhangig vom TPS-Gehalt (40 < ϕTPS < 70 Gew. %) innerhalb von 30 Tagen mit ahnlicher Geschwindigkeit wie native Maisstarke ab. Die in diesem Rahmen untersuchten thermoplastischen Polyurethane (TPU) unterliegen bei Temperaturen von 20 und 37°C keinem nennenswerten Abbau, sofern TPU als alleinige Kohlenstoffquelle vorliegt. Bei Zugabe einer leicht verwertbaren C-Quelle (z.B. Maisstarke) ist ein Anstieg des TPU-Abbaus zu beobachten. Eine Warmeeinwirkung (80°C) beschleunigt die Hydrolyse, was zu einem drastisch gesteigerten Abbau fuhrt, wobei Zwischenprodukte auftreten konnen, die in hohen Dosen toxisch wirken. Allerdings ist die toxische Wirkung der Zwischenprodukte dosisabhangig und unterliegt einer Kinetik, was mit Hilfe des OxiTop®-Systems gezeigt werden konnte und in begleitenden toxikologischen Untersuchungen bestatigt wurde. The OxiTop®-System was used to highlight the differences in biodegradability and environmental acceptance of various polymeric materials based upon renewable resources. For instance the degree of degradation of thermoplastic corn starch (TPS) which was reinforced with natural fibres by 10, 15 and 20% wt. was after a fortnight in the same range as native corn starch. The flax fibre content exerts no significant influence on the degree of degradation since the deviations between the degradation slopes could hardly be resolved. However, TPS itself degrades significantly slower compared to the reinforced TPS-compound using flax fibres. This is because water can penetrate the reinforced material faster due to the “straw effect”. Hence this effect is only detectable above a certain level of fibre content. The degradation of the TPS was slower in these tests compared to the biodegradation of native starch which was due to the sample shape. Contrary to native starch (powder) TPS were used as pellets which results in a reduced specific surface to the TPS. Independent of the TPS-content (40 < ϕTPS < 70% wt) the PCL/TPS-blends degrade practically by the same speed as native starch. The TPU investigated in this report do not degrade significantly at temperatures between 20 and 37°C as long as the TPU is the sole carbon source. With the addition of a carbon source which can be easily degraded (e.g. corn starch) an increase of the TPU-degradation is detected. A rise of the test temperature (e.g. 70°C) speeds up the hydrolysis which drastically accelerates the biodegradation process. However intermediates may occur which can be toxic at high concentrations. Yet the toxicological impact of such intermediates shows a kinetic behaviour which could be demonstrated not only by using the OxiTop®-System but also in accompanying toxicological tests.

Synthesis of Polyolefin-g-Poly(ethylene oxide) by Reacting Maleic Anhydride Modified Polypropylene or Poly(propylene-co-ethylene) with Hydroxy-terminated Poly(ethylene Oxide) in the Melt

The synthesis of amphipolar graft copolymers by reactive extrusion of maleic anhydride modified polypropylene or poly(propylene-co-ethylene) and α, ω-dihydroxy-poly(ethylene oxide) or α-hydro-ω-oxymethyl-poly(oxyethylene) was studied. The graft copolymers were characterized by Fourier transform infrared spectroscopy. Residence time of 30 min at 160°C was established to be sufficient for graft copolymer formation by melt extrusion.

Determination of thermorheological phase diagram of poly(propylene)/poly(ethylene-b-ethylene oxide) blends

Abstract The phase diagram of the polypropylene (PP)/poly(ethylene-blockethylene oxide) (P(E-b-EO) blends exhibiting upper critical solution temperature (UCST) was experimentally established by using small amplitude oscillatory shear rheology, in which the binodal line was obtained by dynamic temperature ramps and the spinodal temperatures were quantitatively estimated on the basis of the theory developed by Ajji et al. The measurements were carried out in the linear viscoelastic regime in which the material functions are sensitive to phase separation.