title: A novel tool to standardize rheology testing of molten polymers for pharmaceutical applications.
abstract: Melt rheology provides information about material properties that are of great importance for equipment design and simulations, especially for novel pharmaceutical manufacturing operations, including extrusion, injection molding or 3d printing. To that end, homogeneous samples must be prepared, most commonly via compression or injection molding, both of which require costly equipment and might not be applicable for shear- and heat-sensitive pharmaceutical materials. Our study introduces a novel vacuum compression molding (VCM) tool for simple preparation of thermoplastic specimens using standard laboratory equipment: a hot plate and a vacuum source. Sticking is eliminated by applying polytetrafluoroethylene (PTFE) coated separation foils. The evacuation of the tool leads to compression of the sample chamber, which is cost-efficient compared to conventional methods, such as compression molding or injection molding that require special equipment. In addition, this compact design reduces the preparation time and the heat load. The VCM tool was used to prepare samples for a rheological study of three pharmaceutical polymers (Soluplus(®), Eudragit(®)E, EVA Rowalit(®) 300-1/28). The prepared samples were without any air inclusions or voids, and the measurements had a high reproducibility. All relative standard deviations were below 3%. The obtained data were fitted to the Carreau-Yasuda model and time-temperature superposition was applied.
authors.affiliation: Research Center Pharmaceutical Engineering GmbH, Inffeldgasse 13/2, 8010 Graz, Austria; Institute of Process and Particle Engineering, Graz University of Technology, Inffeldgasse 13/3, 8010 Graz, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Treffer
authors.affiliation: Research Center Pharmaceutical Engineering GmbH, Inffeldgasse 13/2, 8010 Graz, Austria; Institute of Process and Particle Engineering, Graz University of Technology, Inffeldgasse 13/3, 8010 Graz, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Troiss
authors.affiliation: Research Center Pharmaceutical Engineering GmbH, Inffeldgasse 13/2, 8010 Graz, Austria; Institute of Process and Particle Engineering, Graz University of Technology, Inffeldgasse 13/3, 8010 Graz, Austria. Electronic address: khinast@tugraz.at.
authors.forename: Johannes
authors.initials: J
authors.lastname: Khinast
mesh_terms: D000179:Acrylates / Q000737:chemistry*; D006358:Hot Temperature; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011138:Polytetrafluoroethylene / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry*; D015203:Reproducibility of Results; D012212:Rheology / Q000592:standards*; D013678:Technology, Pharmaceutical / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: D000179:Acrylates; C477020:Eudragit E100; D011108:Polymers; D011145:Polyvinyls; C572167:polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer; C016438:ethylenevinylacetate copolymer; D011092:Polyethylene Glycols; D011138:Polytetrafluoroethylene
keywords: Compression moldings; Melt rheology; Pharmaceutical polymer processing; Reproducibility; Sample preparation