Rotational and Capillary Rheometers Aid Plastic Film Development.

Renolit AG, an international manufacturer of high-quality PVC and polyolefin films for surface refinement and technical applications, is using rotational and capillary rheometers from Malvern Instruments to determine the rheological properties of plastic melts.

The analytical laboratory at Renloit AG supports the company's daily production cycle and the company uses the latest analytical technologies for detailed determination of raw material and film properties. If faults occur, rapid identification of the cause is a priority. For instance, any inclusions in films or film defects are examined in order to locate the source of the defect and rectify it. Renolit's experiences in film analysis also make a positive contribution to new developments and the continuing advancement of films.

Using Malvern rheometers to analyze melts, it was shown that even when plastic granules used in the production of films exhibited identical shear viscosities, there were significant differences in extensional viscosity. This may be attributed to the molecular structure of the plastic, and will not be detected by shear alone. Measuring both shear and extensional viscosities across a broad range requires the use of both rotational and capillary rheometers. This complementary use of both techniques delivers valuable additional information which contributes significantly to the further development of RENOLIT plastic films. An important factor in selecting the systems was Malvern's ability to supply both types of instrument, with the benefits that service and applications support is from a single source.