In-process assessment of clay dispersion in PLA during melt compounding: Effects of screw speed and filler content

Teixeira, Paulo Francisco; Covas, J. A.; Hilliou, L.

doi:10.1016/j.polymdegradstab.2020.109190

Cited by 13 publications

(11 citation statements)

References 39 publications

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“…Since PDMS is a flu at room temperature, it was fed with a syringe pump (PHD 22/2000, Harvard Apparat Holliston, MA, USA) immediately downstream of the location of the first sampling po whereas clay was fed with a volumetric feeder (Piovan MDP1, S. Maria di Sala, Italy) rig after the second sampling location. The extruder is coupled to a rheo-optical die which was used in earlier studies for t in-line assessment of clay dispersion in poly(lactic acid) [20,29]. The die contains two flo channels for the extrusion of rectangular tapes.…”

Section: Compounding and In-process Characterization Of Cpncmentioning

confidence: 99%

“…Both channels are equipped with valv at the entrance to allow for the independent control of material outputs in each chann while maintaining constant extruder screw speed and feed rate. One of the channels fitted with melt pressure transducers (two flush-mounted Dynisco PT422A (0-3000 P The extruder is coupled to a rheo-optical die which was used in earlier studies for the in-line assessment of clay dispersion in poly(lactic acid) [20,29]. The die contains two flow channels for the extrusion of rectangular tapes.…”

Section: Compounding and In-process Characterization Of Cpncmentioning

confidence: 99%

“…Degradation has an even more acute impact on clay dispersion when thermally sensitive polymer matrices are used to manufacture biodegradable CPNC. For instance, larger screw speeds are detrimental to the dispersion of clay in poly(lactic acid), as demonstrated recently by the in-line rheo-optical monitoring of twin-screw extrusion [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

“…Similar changes can also take place when sampling materials from opened barrels after stopping and freezing the extrusion run. Therefore, efforts have been made to identify relationships between the degree of dispersion assessed by optical means (e.g., light attenuation) and the rheological properties of CPNC [ 11 , 20 , 23 ] since both experimental techniques can be performed in-situ during extrusion [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

“…Rheo-optical methods have been used previously both off-line [ 23 ] and in-line [ 20 ] to study the dispersion of organoclay in poly (lactic acid) (PLA) matrices. PDMS-clay nanocomposites have been previously characterized but were prepared by solution intercalation methods [ 25 , 26 , 28 ].…”

Section: Introductionmentioning

confidence: 99%

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In-Line Rheo-Optical Investigation of the Dispersion of Organoclay in a Polymer Matrix during Twin-Screw Compounding

2021

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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 issues associated with thermal degradation. Local heating in the first part of the extruder allows testing of the usefulness of low matrix viscosity to enhance polymer intercalation before applying larger stresses for clay dispersion. The comparison of clay particle sizes measured in line with models for the kinetics of particle dispersion indicates that larger screw speeds promote the break-up of clay particles, whereas smaller screw speeds favor the erosion of the clay tactoids. Thus, different levels of clay dispersion are generated, which do not simply relate to a progressively better PDMS intercalation and higher clay exfoliation as screw speed is increased. Reducing the PDMS viscosity in the first mixing zone of the screw facilitates dispersion at lower screw speeds, but a complex interplay between stresses and residence times at larger screw speeds is observed. More importantly, the results underline that the use of larger stresses is inefficient per se in dispersing clay if sufficient time is not given for PDMS to intercalate the clay galleries and thus facilitate tactoid disruption or erosion.

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Section: Compounding and In-process Characterization Of Cpncmentioning

confidence: 99%

Section: Compounding and In-process Characterization Of Cpncmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In-Line Rheo-Optical Investigation of the Dispersion of Organoclay in a Polymer Matrix during Twin-Screw Compounding

2021

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Potentialities of cellulose nanofibers (CNFs) in low density polyethylene (LDPE) composites

Agnes,

Hillig,

Zattera

et al. 2024

Eur. J. Wood Prod.

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Comparison of shear viscosity and normal stress measurements by rotational and on-line slit rheometers with tube model predictions

et al. 2022

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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 difficult due to a lack of overlap of the in-line data and the off-line measurements by rotational rheometers limited to lower shear rates. Here, shear viscosity and normal stress data measured in-line at large shear rates during extrusion and off-line at low shear rates are compared to predictions of the Doi-Edwards model and the Hierarchical Multi-Mode Molecular Stress Function (HMMSF) model using linear-viscoelastic off-line small amplitude oscillating shear data of two polystyrenes and a low-density polyethylene as input parameters. For polystyrene, the results of this investigation do not only validate the experimental data obtained by rotational as well as slit-die rheometry, but also demonstrate the agreement between experiments and models up to very high shear rates, which were not experimentally accessible earlier. The low-density polyethylene shows a more complex behaviour, which follows the HMMSF model at low shear rates, but approaches the Doi-Edwards model at high shear rates.

show abstract

In-process assessment of clay dispersion in PLA during melt compounding: Effects of screw speed and filler content

Cited by 13 publications

References 39 publications

In-Line Rheo-Optical Investigation of the Dispersion of Organoclay in a Polymer Matrix during Twin-Screw Compounding

In-Line Rheo-Optical Investigation of the Dispersion of Organoclay in a Polymer Matrix during Twin-Screw Compounding

Potentialities of cellulose nanofibers (CNFs) in low density polyethylene (LDPE) composites

Comparison of shear viscosity and normal stress measurements by rotational and on-line slit rheometers with tube model predictions

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