- Equipe de recherche : Duffour E.
- Collaboration : Malfreyt P.
- Laboratoire de Thermodynamique des solutions et des polymères (LTSP) - 24, avenue des landais - 63177 AUBIERE Cedex France
The interaction between plasma and a polymer is accompanied by a significant loss of mass of the insulating material, as well as by energy and chemical transfers between the wall and ionized hot gas. The understanding of the elementary physical phenomenon is the most important technological bolt in terms of control and development of the industrial equipment compelled to this interaction.
With the intention of bringing elements of answers, a theoretical study, based on the resolution of Hamilton's equations, at the microscopic scale, is accomplished in the laboratory. From a molecular model of the polyethylene, a macromolecule with the following chemical formula (CH2)n, some different interactions are studied :
- energy transfer by local heating of the polymer,
- the interaction between the energetic incident particles and the polymer surface area,
- calculation and study of the variations of the polymer's local structure properties,
- variation of the thermodynamic properties, like temperature, pressure...,
- evaluation of the transport coefficients at the plasma-polymer area: diffusion, viscosity...
Figure 1. Complete model of the polyethylene crystal.
Figure 2. Polyethylene crystal, SF6 molecule and copper ions interaction.
The last evolutions of the model are :
- taking into account the coulombian's forces inside the polyethylene crystal, it is then possible to study the interaction between the ionised particles and the surface area of the polymer,
- taking into account the creation of the new molecules that could come from the interaction between the incident particles and the products of the decomposition of the material, like for example the CuF molecule,
- parallel computing subroutines have been added to the original code using MPI's (« Message-Passing Interface ») implementation, to use the computational power of the actual computers,
- development of various algorithms, study of the decomposition of the material, distribution's functions, auto correlation's functions...
Interaction Polyethylene crystal- copper ions Cu+
Figure 3. Time evolution of the polyethylene's crystal temperature.
Figure 4. Time evolution of the different kinds of kinetic and potential energies of the polyethylene crystal. The average velocity of the incident particles is 7 km.s-1.