Wetting behavior of polymer melts

Adhesion and friction between polymers and mold surfaces is a key issue in polymer processing. Demoulding forces in injection molding are reduced by physical, chemical, or roughness modification of the mold surface.

 

The research area ‘Wetting of polymer melts‘ is focused on the prediction of friction be-havior of the mating partners polymer and mold surface at processing temperatures by analyzing wetting parameters.

The Chair of Injection Moulding of Polymers and the PCCL research in:

  • Systematic analysis of polymer melt wetting on modified and tempered solid surfaces (steels, PVD coatings)
  • Determination of temperature dependant solid surface energy fractions using high temperature test liquids
  • Determination of surface tension fractions of molten polymers
  • Calculation of work of adhesion and interfacial tension at process temper-atures
  • Correlation of wetting parameters to surface topography and friction in injection molding of polymers

The experiments are conducted on a drop shape analyzer for polymer melts featuring

  • a tempering chamber (up to 400°C),
  • a high-temperature dosing unit (up to 400°C),
  • an electronic single dosing unit for standard test liquids and
  • analysis software to determine contact angles, surface energy, surface tension and interfacial tension.

Furthermore, an injection test mold with integrated friction test featuring

  • part manufacturing in a conventional injection process and friction test during demoulding
  • contact pressure, friction velocity, mold temperature, all of them adjustable draft angle of 0°
  • determination of static coefficient of friction µ 0 between thermoplastic polymers and (coated) mold surfaces

is used.


Surface topography analysis is done by Atomic Force Microscopy, White light interferometry, and confocal microscopy, respectively.