Search

Ein wesentlicher Vorzug der Strahlungshärtung von Klebstoffen oder Lacken liegt in der Schnelligkeit. Für die Formulierung neuer photohärtender Harzsysteme oder die Prozessoptimierung ist es deshalb wichtig, die Härtungs- oder Trocknungsvorgänge zu verstehen. Um nun den chemischen Umsatz und den dynamischen Schubmodul mit einer Zeitauflösung bis in den Millisekundenbereich erfassen zu können, wurde die Nahinfrarot-Spektroskopie mit einem Ultraschallreflexionsverfahren kombiniert.

Commercial injection moulding simulation programs have so far not included crystallisation-kinetic aspects. Without this approach it is impossible to correctly simulate the material behaviour in the injection moulding process, and the simulation is incomplete. The results explained below can eliminate these deficiencies. Kunststoffe-Plast Europe

Dielectric spectroscopy is employed in lamellar forming non-linear block copolymers of the type (BA)3B and (BA)3B(AB)3 based on polyisoprene (A) and polystyrene (B), at temperatures well below the order-to-disorder transition temperature and below the glass transition temperature of the hard phase (polystyrene). We show here that dielectric spectroscopy can be used as a tool to probe the interface in ordered block copolymers with a basic triblock unit. Our estimate of the interfacial width is based on the mobility of the junction points at the interface and compares favorably with the estimated thickness from thermodynamics. © 1998 Elsevier Science B.V. All rights reserved.

Dielectric spectroscopy is employed in two polystyrene-polyisoprene-polystyrene (SIS) triblock copolymers well below the order-to-disorder transition temperature and in the frequency range from 10-2 to 106 Hz. Small angle X-ray scattering has shown the formation of lamellar structures with a long period of about 25 nm. Besides the polyisoprene and polystyrene segmental relaxations and a slower process associated with the reorientation of the interface, we provide evidence for a new type of chain dynamics associated with the mobility of the junction points at the interface. From the relaxation strength of this process - which is very much reduced as compared to the chain relaxation in bulk polyisoprene - we extract a characteristic length of the end-to-end vector fluctuations in the interface in the range 4-6 nm. This value compares well with an independent estimate of the interfacial thickness based on thermodynamics. Dielectric spectroscopy can therefore be used as a dynamic probe of the interface in ordered triblock copolymers. Over the same temperature range rheology is influenced by a broad spectrum of modes related to the dynamics of tethered polyisoprene chains.