SISAPEM

A contribution to the fundamental understanding of Shear-Refinement of polymer melts by entanglement manipulation

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 Obiettivo del progetto (Objective)

'It has been demonstrated by J-P Ibar that thermal-mechanical history of a polymer melt, in particular the use of mechanical oscillation superposed to shear flow (for instance in the gap of an extruder) appears to boost the magnitude of viscosity and elasticity reduction due to Shear-Refinement. These parameters play a crucial role during processing of plastics, determining the high temperature required to produce flow, thermal degradation, the long cycle times and thus the present productivity limitation in our industries. In the case of loaded polymers, which addresses more than 80% of the polymer resin used today, their high viscosity, aggravated by the presence of the concentrate, limits the maximum amount of dispersants allowed, such as for carbon nanotubes (CNT), as well as the quality of the mix. At the same time, several universities of world wide reputation, including the LPMI of UPPA, the university of Pau et Pays de l’Adour (now called IPREM-EPCP), the Ecole des Mines de Paris (CEMEF Sofia Antipolis) showed that viscosity and elasticity of polymer melts can be reduced by disentanglement of the macromolecules induced by strong deformation. Rheological variables such as strain amplitude, strain rate, elongational ratio, in other words melt thermal-mechanical history, as well as molecular characteristics such as chain molecular weight Mw, degree of branching, branch length, play a critical role to induce chain disentanglement, insure its stability in time, or favor re-entanglement. The objective of this project is to combine the competence of J-P Ibar and that of UPPA-IPREM-EPCP through a collaboration to understand fundamentally the mechanisms of disentanglement and re-entanglement, by Shear Induced Strain Amplified Polymer Entanglement Manipulation (SISAPEM) in order to produce stable disentangled polymers, for instance under pellet form, capable of recovering, after processing, their initial entanglement characteristics and thus their physical performance.'

Introduzione (Teaser)

Polymers form the basis of numerous products made from melted polymer mixtures. New research supports the potential of a processing treatment to decrease viscosity, opening the door to novel formulations with high-tech fillers.

Descrizione progetto (Article)

Polymers, often called plastics, have become ubiquitous. They are in products ranging from food and beverage containers to automotive components to consumer electronics and are a major pillar of the EU economy. Viscosity plays a critical role in processability as a polymer melt is typically employed to fill a mould. High viscosity (internal friction and resistance to flow) affects processing temperature, cycle time, productivity and product quality.

Low-frequency pulsed shear and extensional mechanical treatment helps reduce shear stress. This could help in orienting the melt during extrusion (sustained orientation or disentanglement of the normally tangled polymer chains). However, the topic is one surrounded by controversy given its contradiction of established theories. EU-funded scientists investigated the physical mechanisms of sustained orientation with EU-funding of the project SISAPEM.

Researchers made an inestimable contribution to the field of polymer science by verifying the existence and mechanisms of sustained orientation. Decreasing the viscosity of high-tech polymer mixtures with high concentrations of fillers including carbon nanotubes opens important new markets for the polymer industry. These include the production of flame retardants and components with high electrical conductivity.

Future research will focus on controlling the viscosity of polymer melts using low-frequency pulsed shear and extensional mechanical treatment during processing. SISAPEM outcomes are expected to spawn a flurry of research and discovery and a superior components for high-tech devices could be just around the corner.