The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Using a Micro Blown Film Line for Formulation Screening
A LabTech Ultra Micro Combi line (Microline), the smallest blown film line in the world, was used to conduct blown film formulation screening with a set of LLDPE/LDPE blends. A sample cutting pattern was developed to enable preparation of crease-free test specimens from the small layflat made on the Microline. Haze, dart A, tear (MD, TD) and tensile (MD, CD) were tested using the film made by the Microline. By carefully controlling the time to frost line on the Microline to match the time to frost line on the larger scale lines, it was found that dart A, tear (MD, TD) and tensile (MD) of the Microline film were correlated with those of the larger scale lines films. These film properties can be used for formulation screening with minimal consumption of materials (~150 g per film sample). Haze and tensile (CD) properties did not correlate with those of the larger scale lines films. Future work will investigate the cause of these deviations.
Viscosity Characterization and Transient Flow Simulation and Visualization of Ptfe Paste Extrusion
The shear viscosity of polytetrafluoroethylene (PTFE) paste and its flow behavior during paste extrusion were investigated. Frequency sweeps using a parallel plate rheometer were performed on compression molded samples of PTFE paste made from fine powder PTFE mixed with ethanol as a lubricant. Various grits of sandpaper were used to reduce slip of PTFE paste on the walls. A viscosity model was generated and COMSOL Multiphysics was used to create a time-dependent flow simulation of PTFE through a paste extruder. The simulated results were compared to experimental data of actual paste extrusion. Due to simplifications used in the model, the simulated extrusion pressure over time differed in both magnitude and slope when compared to the experimental data. The simulated velocity profile was compared to flow visualization experiments, showing good agreement in wider regions of the extruder. Despite these drawbacks, the experiments and simulated model provided useful information about the flow within the paste extruder.
Viscosity Considerations In Multilayer Coextrusion
Due to complex viscoelastic nature of the polymers, it is challenging to process multicomponent structures with uniform layer thicknesses. Although multilayered structures have been processed in a broad array of polymer materials and formulated to service a wide range of applications, a clear understanding of the effects of viscosity matching on the uniformity of the layer periodicity is not well understood. Significant work on viscous encapsulation and secondary flow patterns in the die channels affecting the layer structures has been previously reported. However, further evaluation of these effects on wide range of materials in commercial coextrusion lines has been limited. In this paper, we look to extend the initial studies of rheology in multilayered materials via layer multiplication coextrusion approaches and demonstrate preliminary results on model systems that illustrate the effect of mismatched viscosity on coextrusion multilayered polymer materials systems.
‘Plug-and-Play’ Weight Reduction Solution by Hollow Glass Microspheres
Fillers have been in use since the early days of plastics. Today’s enormous growth of the polymer industry is due to the unique properties of fillers they impart to polymers. Glass bubbles (low density hollow glass microspheres) as fillers have been incorporated into thermoset polymers for decades. They are tiny hollow spheres and are virtually inert. These glass bubbles are are compatible with most polymers. Until recently, their use with thermoplastic polymers has been limited because of high rates of bubble breakage from the high shear forces to which they are exposed during such thermoplastic processing operations as extrusion compounding and injection molding. At issue has been the strength of the glass microspheres.
Cost and Mixing Keeps the Screw Rivalry Up & Going
Screw is the heart of an extruder. It is fact that mixing capability of a single screw is poorer than of a twin screw. More precisely, the dispersive action (breakdown) of a twin screw extruder is always better than of a single screw extruder. For producing new blends or alloys, as well as for mixing powdered feedstock or regrinds -- twin screw extruders give unparalleled dispersion. No surprise that twin screw extruders cost more than single screw extruders.
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