Michaela Gedan-Smolka

Spannungsrissbeständigkeit von Pulverklarlacken

Spannungsrisse bei Pulverklarlacken sind ein altbekanntes Problem. Um mehr uber die Spannungsrissanfalligkeit marktublicher Pulverklarlacke zu erfahren, wurden verschiedene Ein- und Mehrschicht-Systeme in einer breit angelegten Untersuchung verglichen.

Polymeric additives for antistatic treatment of sheet molding composites (SMC)

Novel oligomeric/polymeric additives with ionic units were synthesized in a one pot procedure in order to enhance the specific surface resistivity of SMC-materials. In contrast to industrially used inorganic salts or carbon materials, such as carbon black or CNT’s, these substances are nearly colorless and matrix compatible and, resulting from that, easy to homogenize with the SMC-matrix. Furthermore, it was found, that additives which can be covalently bonded to the matrix during the molding procedure are preferred compared to physically mixed substances. The effectiveness of chemically bonded substances regarding with the lowering of the specific surface resistivity is higher and selected additives do not change the reactivity and resulting mechanical properties of the molded material.

Formulation and Characterization of PAI-PTFE-cg Antifriction Coatings

Polytetrafluoroethylene (PTFE) powder is used as a solid lubricant in commercial antifriction coatings. However, most of the matrix polymers are usually not compatible with virgin PTFE resulting in low dispersion and mechanical film stability and adhesion. In our research PTFE TF 2025 was irradiated by g-beam generating PTFE micropowder with persistant radicals and functional groups. These functional groups are able to perform a chemical grafting (cg) of polyamideimide (PAI) and modified PTFE-micropowder by reactive extrusion in melt. Based on grinded extrudates PAI-PTFE-cg dispersions were formulated followed by characterizing dispersion as well as film properties. It was found, that PAI-PTFE-cg dispersion comprises very small PTFE-particles at higher g-irradiation doses in homogeneous dispersions. In addition, all samples showed outstanding film flexibility. Basic tribological properties under mixed lubrication were studied by using a ring-on-disk tribometer. Finally, diluted dispersions were applied to a multi-surface sliding bearing (four segments) for testing in a hydrodynamic plain test bench.