Markus Battisti

PP-polymer nanocomposites with improved mechanical properties using elongational flow devices at the injection molding compounder

Numerous researches have been done in the field of improving PP by adding nanofillers. Consistently good scientific results and positive industrial feedback were reached; however, the industrial interest is still low due to the high technological and financial risks and too less benefit. Our experiments, using the worldwide unique Polymer NanoComposite Injection Molding Compounder (PNC-IMC) which combines the two processing steps of compounding and injection molding, showed an impressive increase of both mechanical and thermal properties, but more or less in the same range than in other publications. Thus we tried to improve the materials by using elongational flow generating devices for better intercalation and exfoliation of nanofillers in the polymer melt. This paper will give an overview on our first investigations, carried out on both a high pressure capillary rheometer (HPCR) and the injection molding machine (IMM) focusing on the mechanical properties. The PNCs were produced at the PNC-IMC with the...

Flow behaviour of rubber in capillary and injection moulding dies

ABSTRACT This study is concerned with the flow behaviour of a rubber compound in capillary and injection moulding dies in the temperature range of 80–120°C. The injection moulding die designs had a tapered angle ranging from 40° up to 150°. The rheological characterisation of the rubber compound in the capillary dies showed that rubber slips at the wall, and this was modelled with an appropriate slip law. The pressure drops in the system were measured for all tapered dies. Numerical simulations were then carried out with a purely viscous (Carreau) model and a multimode viscoelastic (K-BKZ) model. The results showed a good agreement with the experiments for both the capillary and the injection moulding dies, provided that slip is included in the simulations as determined experimentally.

Flow Behavior of PP-Polymer Nanocomposites in Capillary and Injection Molding Dies

Abstract For simulation of thin-wall injection molding, accurate viscosity data measured at shear rates up to 800,000 s−1 and more are important, but not available in any commercial material database. Such data can be measured on conventional injection molding machines with the help of a rheological mold, which is constructed like a standard injection mold with interchangeable dies. It enables operators to measure viscosity in time on their own machines at practically relevant shear rates (from 102 s−1 to 2 × 106 s−1). A special feature allows measuring the pressure dependency of viscosity using closed-loop counter pressure control. Experimental data are evaluated taking into account the melt temperature rise due to dissipative heating. Using capillary dies having different diameters, D, and length-to-diameter L/D ratios, a full rheological characterization has been carried out for a polypropylene-filled nanocomposite, and the experimental data have been fitted both with a viscous model (Cross) and a viscoelastic one (the Kaye – Bernstein, Kearsley, Zapas/Papanastasiou, Scriven, Macosko or K-BKZ/PSM model). Four injection molding dies have been also used to reach apparent shear rates up to 800,000 s−1. Particular emphasis has been given on the pressure-dependence of viscosity. It was found that only the viscoelastic simulations were capable of reproducing the experimental data well, while any viscous modeling always underestimates the pressures, especially at the higher apparent shear rates and L/D ratios.

A study on material optimization for polypropylene nanocomposites based on layered silicates using elongational flow devices

Over the last years, the use of nano-reinforced polymers increased due to their superior mechanical, thermal and rheological properties. Polymer nanocomposites (PNCs) which are based on layered silicates feature a higher Young’s-Modulus and increased thermal conductivity.The aim of this study was to improve the material properties for polypropylene PNCs based on layered silicates by using elongational flow generating devices with super-imposed shear- and elongational flow and optimized nozzle geometries. In order to gain knowledge about the differences in influence for various nozzle geometries, five different hyperbolical and conical nozzles were designed. The varying factors are the nozzle length, the exit radius and the injection speed which correlates with the elongation rate and shear rate. The influence of these parameters was tested for two different materials with a full factorial 23 design (DoE). The first material was a lower viscous homopolymer and the second material a higher viscous block cop...

Short-term and long-term behavior of PP-polymer nanocomposites produced by injection molding compounding

There are only few investigations considering the impact of nanoscale fillers on the mechanical und thermo-mechanical properties of polymers. Particularly there is a lack of results regarding long term creep behavior of Polypropylene-based polymer nanocomposites (PNCs). Therefore, the objective of this study is to determine the influence of nanofiller content on the mechanical and thermo-mechanical behavior of Polypropylene-based PNCs. Processing of the test specimens was carried out using the Polymer NanoComposite Injection Molding Compounder (PNC-IMC). In comparison to the conventional compounding process, in which the compound must be pelletized and fed into the injection molding machine for the second plasticizing process, injection molding compounding combines these two processing steps. Material compounding and subsequent injection molding are done directly with only one plasticizing process, using a heated melt pipe and a melt accumulator for melt transfer from the compounder to the injection moldi...