This project deals with fluorosilicone (FVMQs) ageing, lifetime prediction and the synthesis of new FVMQ based materials.
In the field of synthesis, the aim is to create copolymers (containing for example aromatic groups) or thermoplastic elastomers like fluorosilicones (with a reversible physical crosslinking) so as to broaden the range of performances of FVMQs and propose new materials with a better tradeoff « processability / mechanical properties / thermal resistance / resistance ot chemicals ».
The multiscale ageing study will aim at using fine descriptors for the analysis of ageing at molecular scale (using for example FTIR, NRM, elemental analysis…), and the study of its effect at macromolecular scale (apparition of chain scissions or crosslinking by DMA and sol-gel analysis) and the link with relevant mechanical properties for typical purposes of FVMQs pars (compressibility, relaxation, fluage, with taking into account the existence of heterogeneous degradation with an oxidation gradient).
This study will base on an « incremental » approach in which we will first study rubbers with an increasing structural complexity (uncured rubber, cured rubber, cured and stabilized rubber withh various kinds of thermal stabilizers and finally some real FVMQs parts). Contrarily to the scarce previous works addressing FVMQs ageing (mainly based in the study of anisothermal degradations performed in situ in TGA cell), we will perform isothermal ageing at moderate temperatures (to better ensure the representativness of mechanisms) under air. We will also investigate the effect of external atmosphere (study of ageing either under nitrogen or with several oxygen pressures) to better understand the link between oxygen presence and structural changes and later address the case of thick samples ageing, in which thermal ageing provokes an oxidation gradient from edges to the bulk.
Last, we will address the case of real ageing by investigating the ageing in presence of chemicals, in particular moderataly polar solvents, in particular through an original study of the effect of thermal ageing on resistance to solvent ingress, and by discussing the effect of chemical on thermal ageing.
Finally, lifetime predictions will be performed by a kinetic model based on the knowledge of the main reactions taking place in degradation, as highlighted from ageing studies. This model is expected to allow a more reliable lifetime prediction than the empirical approaches such as extrapolations based on Arrhenius law (as reported in the scarce studies dealing with the topic). It will permit to the industrial partner to reassure its potential customers in new markets very demanding in terms of durability.
Monsieur Emmanuel Richaud (Procédés et Ingénierie en Mécanique et Matériaux)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
ICGM Institut de chimie moléculaire et des matériaux - Institut Charles Gerhardt Montpellier
PIMM Procédés et Ingénierie en Mécanique et Matériaux
ARMINES CdM ARMINES
ITC Elastomeres / Direction Technique
Help of the ANR 585,828 euros
Beginning and duration of the scientific project: - 42 Months