Polyvinyl chloride - Processing and structure
Abstract - Widely different procedures for the processing of PVC have proved themselves and have succeeded in practice on the basis of the special physical and chemical properties of PVC. In this connection a distinction must be made between the processing of plasticized PVC and the relatively difficult processing of rigid PVC. A survey of the most important methods of preparation and processing is given here. The special, rather abnormal properties of PVC in comparison with other thermoplastics are partly a result of its characteristic structure. The consequences for preparation and processing must therefore be considered anew. Of course, the globular structure of PVC has an effect on the behaviour of the solid-state material and the melt, too, so that great importance must be attributed to the processes at the particle interface.
Rheologische Eigenschaften von Polyvinylchlorid im Vergleich mit Styrolpolymerisaten
Messungen der Viskositatsfunktion, der Strangaufweitung und des Speichermoduls zeigen fur plastifiziertes Suspensions-Polyvinylchlorid (PVC) einen wesentlich anderen Verlauf als beispielsweise fur das Homopolymerisat Polystyrol. Ahnlichkeiten in den rheologischen Eigenschaften bestehen jedoch mit einem ABS-Polymeren, dessen morphologische Struktur durch die heterogene Einlagerung von Polybutadien gekennzeichnet ist. Das rheologische Verhalten von PVC kann mit der Annahme einer Teilchenstruktur in der PVC-Schmelze verstanden werden, die sich bei etwa 200°C auflost, nach Abkuhlung aber wieder zuruckbildet. Elektronenmikroskopische Dunnschnittaufnahmen ergeben fur die Teilchen in PVC einen Durchmesser von ungefahr 0,03 μm.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.