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Comparison of shear viscosity and normal stress measurements by rotational and ...
Teixeira, Paulo Francisco; Hilliou, L.; Covas, J. A.; Narimissa, Esmaeil; Poh, Leslie; Wagner, Manfred H.In-extruder measurements of shear viscosity and normal stresses are important as these measurement techniques allow determining the rheological state of the polymer melt at processing conditions up to high shear rates. However, validation of viscosity and normal stress data obtained by in-line slit rheometers at high shear rates is difcult due to a lack of overlap of the in-line data and the of-line measurement...
In-line rheo-optical investigation of the dispersion of organoclay in a polymer...
Teixeira, Paulo Francisco; Covas, J. A.; Hilliou, L.The dispersion mechanisms in a clay-based polymer nanocomposite (CPNC) during twin-screw extrusion are studied by in-situ rheo-optical techniques, which relate the CPNC morphology with its viscosity. This methodology avoids the problems associated with post extrusion structural rearrangement. The polydimethylsiloxane (PDMS) matrix, which can be processed at ambient and low temperatures, is used to bypass any is...
Taking advantage of the functional synergism between carbon nanotubes and graph...
Infurna, Giulia; Teixeira, Paulo Francisco; Hilliou, L.; Dintcheva, Nadka Tz.; La Mantia, Francesco Paolo; Covas, J. A.Carbon Nanotubes (CNT) and Graphene Nanoplatelets (GNP) were incorporated in Polypropylene (PP) as single filler (CNT=1, 2 and 4 %wt. and GNP=2, 4, and 6 %wt.) and in hybrid form (CNT:GNP weight ratio 2:2, 2:4 and 4:2) using a prototype miniature Twin Screw Extruder (TSE) coupled with a double slit rheological die, in order to assess in-line the extent of nanofiller dispersion and to deliver PP-based nanocompos...
Film blowing of PHB-based systems for home compostable food packaging
Teixeira, Paulo Francisco; Covas, J. A.; Suarez, M. J.; Angulo, I.; Hilliou, L.One of the routes to minimize the environmental impact of plastics waste is the use of bio-sourced and biodegradable alternatives, particularly for packaging applications. Although Polyhydroxyalkanoates (PHA) are attractive candidates for food packaging, they have poor processability, particularly for extrusion film blowing. Thus, one relatively successful alternative has been blending PHA with a biodegradable ...
Multi-parameter in-process monitoring of clay dispersion during melt compoundin...
Teixeira, Paulo Francisco; Sutera, F.; Scaffaro, R.; Covas, J. A.; Hilliou, L.The time evolution of organoclay particle size and volume fraction, as well as the shear viscosity, are measured in-line for a series of Poly(lactic acid)/organoclay composites, using a rheo-optical die coupled to a prototype modular co-rotating twin screw extruder. The small angle light scattering patterns and light attenuation recorded during transient experiments indicate that clay dispersion develops throug...
Evolution of dispersion in the melt compounding of a model polymer nanocomposit...
Gaspar, Hugo Silva; Santos, Ana Raquel Ribeiro; Teixeira, Paulo Francisco; Hilliou, L.; Weir, Michael P.; Duif, Chris P.; Bouwman, Wim G.We investigate the morphological development of polystyrene (PS)-C-60 nanocomposites along the length of a prototype co-rotating twin-screw extruder with sampling capabilities. The effects of C-60 concentration and output on the morphological evolution along the extruder are studied employing a suite of characterization techniques covering a wide range of length-scales, thereby shedding new light on the dispers...
In-process rheological measurements during the manufacture of multiphase polyme...
Covas, J. A.; Teixeira, Paulo Francisco; Hilliou, L.The properties of multiphase systems (e.g., immiscible and compatibilized polymer blends, nanocomposites) depend on the characteristics of the components, on their concentration, on the interfacial adhesion and on the resulting morphology. In turn, the latter is influenced by the thermomechanical environment created during the manufacture of these systems, often by twin screw extrusion. Since the rheological be...
A new double-slit rheometrical die for in-process characterization and extrusio...
Teixeira, Paulo Francisco; Ferrás, Luís Jorge Lima; Hilliou, L.; Covas, J. A.The twin-slit rheological die can be operated in such a way that the total pressure drop is maintained constant while the shear rate in the measuring slit is changed. The device is particularly useful when coupled to an extruder and used to characterize materials that are sensitive to thermo-mechanical conditions. In the present work, the twin-slit die design was modified to a double-slit die where the measurem...
Dual-slit rheo-optical die for the characterization of process sensitive melts
Teixeira, Paulo Francisco; Ferrás, Luís Jorge Lima; Covas, J. A.; Hilliou, L.Instrumented slit dies coupled to single or twin screw extruders have been used by many researchers to measure shear viscosity and normal-stress differences and perform rheo-optical experiments, namely small angle light scattering, birefringence, polarized optical microscopy, and turbidityturbidimetry. Generally, generation of a range of shear rates implies operating the extruder with varying screw speeds or fe...
Effects of fermentation residues on the melt processability and thermomechanica...
Hilliou, L.; Teixeira, Paulo Francisco; Machado, Diogo Silva; Covas, J. A.; Oliveira, Catarina S. S.; Duque, Anouk F.; Reis, Maria A. M.Two polyhydroxy(butyrate-co-valerate) (PHBV) produced from mixed microbial cultures (MMC) fed with fermented cheese whey (CW) and recovered with different down streaming routes, were processed into filaments by plasticating extrusion. The thermorheological characteristics were improved when fermentation residues were recovered together with the MMC PHBV polymer. Thermogravimetric analysis of the extruded filame...