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PO: Polymerphysik

PO 7: Poster: Oberflächen und Grenzflächen

PO 7.15: Poster

Mittwoch, 11. März 1998, 15:25–17:15, P1

Transcrystallinity and Permeation Behaviour of Isotactic Polypropylene — •T. Ton-That and B.-J. Jungnickel — Deutsches Kunststoff-Institut, Schlossgartenstrasse 6, D-64289 Darmstadt

The surface of plastics parts experiences a particular solidification during processing. The resulting structure rules a number of important material properties. In order to model these conditions, the crystallization kinetics and morphologies of i-PP on various metallic, anorganic, and polymeric substrates have been studied by cooling thin samples at different rates, and investigating them by means of polarisation microscopy, DSC, and X-ray scattering. The results indicate that poly (ethylene terephthalate), polytetrafluoroethylene, and polyimide as well

act as efficient nucleating surfaces. They generate distinct transcrystalline surface layers, the widths of which depend on the cooling rate, and enhance the degree of crystallinity of the samples. Despite the non-isothermal crystallization conditions, Avrami exponents can be determined. They differ for all investigated surfactants for thin

samples. The importance of such surface layers has been proven by determination of the water diffusion coefficients of the samples using a particular desorption technique. It turns out that the transcrystalline texture reduces strongly the water diffusion ability through the polymer: whereas spherulitic material exhibits a diffusion coefficient D of D=2.26x10⁻⁵mm²/s, we have D=1.39x10⁻⁵mm²/s in transcrystalline material.