Films multinanocouches de polymères amorphes coextrudés : élaboration, caractérisation et stabilité des nanocouches

Abstract : Nanolayer coextrusion enables the production of polymeric films composed of up to thousands of alternating layers. The thickness of each layer can in theory be controlled, by monitoring the number of layers, the mass ratio of the polymers, and the draw ratio of the film at the exit die, and can decrease down to several nanometers. It has been shown that such films can display drastically improved macroscopic properties, such as optical, gas barrier, or mechanical, due to confinement and interfacial effects. However, layer beak-up phenomenon occurring at such thicknesses, impacting the resulting properties, has also been reported for many polymer pairs. The goal of this thesis is to investigate the causes for these break-ups and for the instabilities leading to them. Most of this work deals with multilayer films of polymethyl methacrylate (PMMA) and polystyrene (PS), two amorphous polymers which blends were widely studied in the literature. Films with 65 to more than 8000 layers were fabricated by modifying processing and molecular parameters, to determine their impact on the homogeneity of the samples. These films were characterized mainly by using microscopy techniques, and especially atomic force microscopy (AFM), to extract not only the mean layer thickness, but distribution of thicknesses and the ratio of broken layers within the sample. A first necessary step was to develop a reliable statistical and quantitative analysis to obtain such information. Then, a first study focused on the effects of some process and material parameters on the homogeneity of multilayer films with micronic thicknesses. Choosing favourable experimental conditions at these scales, nanolayered films were then fabricated. We showed the existence of a critical layer thickness, below which layer breakup, estimated at around 10 nm for PS/PMMA films. When the targeted thickness is around or below 10 nm, the amount of broken layers increases significantly. We make the hypothesis that the layer breakup phenomenon is due to interfacial instabilities driven by van der Waals forces. The thicknesses of the layers we can reach with this process are so small that dispersive forces between two layers composed of the same polymer cannot be neglected (typically below 100 nm). Model experiments are proposed to quantitatively study the critical conditions of appearance of these layer breakups.
Complete list of metadatas

https://pastel.archives-ouvertes.fr/tel-01513149
Contributor : Abes Star <>
Submitted on : Monday, April 24, 2017 - 4:55:34 PM
Last modification on : Wednesday, June 12, 2019 - 5:02:26 PM
Long-term archiving on : Tuesday, July 25, 2017 - 5:08:10 PM

File

BIRONEAU.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-01513149, version 1

Collections

Citation

Adrien Bironeau. Films multinanocouches de polymères amorphes coextrudés : élaboration, caractérisation et stabilité des nanocouches. Mécanique des matériaux [physics.class-ph]. Ecole nationale supérieure d'arts et métiers - ENSAM, 2016. Français. ⟨NNT : 2016ENAM0059⟩. ⟨tel-01513149⟩

Share

Metrics

Record views

851

Files downloads

1320