Peter Guttmann

Dynamic mechanical profile of polyketone compared to conventional technical plastics

Currently the development of a new generation of polyketone materials offers an interesting technical property profile primarily characterized by excellent chemical resistance, impact resistance and gas barrier properties. Various fields of structural applications such as automotive and electronics as well as pipe and film applications are in prime focus for the practical use of polyketone competing well established technical plastics such as polyamides or polyoxymethylene among others. Besides the excellent physical properties mentioned above, particularly the viscoelastic performance of the polymers is decisive for a successful use in structural applications. Regarding this, especially the mechanical behavior under dynamic and/or long term loading conditions is of major interest. Therefore, a sound and comprehensive dynamic mechanical test methodology under consideration of the time and temperature dependent deformation behavior is required for reliable materials comparison and characterization. In this...

Fibre-Reinforced Polyamides and the Influence of Water Absorption on the Mechanical and Thermomechanical Behaviour

Polyamides tend to absorb water from environment especially due to their polar structure. Aliphatic polyamides absorb water faster and to a higher extent than polyamides, aromatic parts within their backbone. The absorbed water causes a weakening of the hydrogen bonds between adjacent polyamide backbones. For both, aliphatic and semi-aromatic polyamides, a significant shift of the glass transition was found using dynamic mechanical analysis. In tensile tests the water absorption and increase of testing temperature show a decrease of the tensile modulus and tensile strength for the aliphatic polyamide 66 (PA66) and the semi-aromatic polyamide (PPA) types. Whereas PA66-GF30 and PA66-GF50 also show an increase of elongation at break with water absorption and higher testing temperature, no such effect can be found for PPA-GF35. An efficient creep test methodology using the Stepped Isothermal Method (SIM) and the principle of time–temperature superposition show differences in the long-term creep behaviour of the investigated polyamides in wet materials condition. It can be shown, that, if the testing or reference temperature of creep tests is chosen at the beginning of the glass transition range, the short-term mechanical properties remain at a high level, but the creep tendency is significantly increased. With testing temperatures distinctly above glass transition, PA66-GF30 and PA66-GF50 show a lower creep tendency compared to PPA-GF35 which was tested at a temperature close to the glass transition range. Physical or chemical ageing effects induced by water absorption of polyamides, which may occur after long-term exposure, are not considered within the present test program. Further specific materials characterisation methods after long-term immersion are recommended for the investigation of possible ageing effects.

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...