Description:

Webinar

Applications of Coupled Rheology-FTIR to Polymer Analyses

Dr. Sara Reynaud, Arkema (& NATAS President)

and Dr. Dana Garcia, consultant (& Arkema retired)

Wednesday, February 16, Webinar at 5:00 PM Pacific time

Abstract:

The advancement of coupled rheological spectroscopic techniques creates wide opportunities to study in situ structure-property-processing-performance relationships of polymers under dynamic conditions. At Arkema, we explored the use of combined Rheo-IR in the attempt to understand the mechanisms behind phenomena such as shear instability, preferential crystallization pathways, structural changes under processing conditions, and more. This presentation summarizes initial studies on temperature-dependent structural transitions in Styrene-Butadiene Copolymers and Poly(methyl methacrylate)-Polylactic acid (PMMA-PLA) blends. The collection of real time IR spectra allows identification of chemical changes within the polybutadiene blocks during isothermal rheological experiments. The partial irreversibility of the chemical changes indicates a possible crosslinking of the copolymer when processed at high temperatures. In the case of PMMA-PLA blends, the variation of the IR spectra suggests the formation at high temperatures of a metastable morphology, which was difficult to detect by rheology alone.

In a more recent study, we describe the mechanisms of internal lubrication due to the addition of polymer process aids to polyethylene. In particular, we will focus on commercial fluoropolymer based polymer processing additives, Kynar® PPAs, used to eliminate melt fracture during film extrusion.  We show that addition of ppm level of Kynar® PPAs into PE drastically improves the quality of extrusion. The lubrication phenomenon is due to the migration of PPA particles to the metal surface of the die, which promotes wall slippage. Although the PPA migration mechanism at high shear rates is well understood in the industry; very little is known about the effect of PPAs on the flow behavior of the molten polymer when processed at relatively low shear rates. Our Rheo-IR findings indicate a good correlation between the transient viscosity and the evolution of the CH2 band in presence of PPAs. Based on the conformational changes and the increase in PE mobility observed in the IR spectra when shearing PE with Kynar® PPA, we suggest a new internal lubrication mechanism that involves the diffusion of PPA droplets across the polymer matrix instead of migrating to surface. This work explains why a small amount of Kynar® PPA is also beneficial for low shear rates processing such as pipe & cable extrusion. Further experiments are underway to investigate lubrication and migration phenomena in other commercial systems.

Speaker Background:

EVENT DATE: Wednesday, February 16

Registration requested by: Tuesday, February 15, 1:00 PM.

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Webinar Timing: Webinar Time 5:00 PM.

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