J. Amouroux

Role of helium plasma pretreatment in the stability of the wettability, adhesion, and mechanical properties of ammonia plasma-treated polymers. Application to the Al-polypropylene system

The stability of a plasma-treated polymer surface is an important issue, but very often a surface rendered wettable by the treatment is found to revert to a less wettable state with time. The purpose of this work was to minimize the ageing phenomenon by stabilizing the surface layer via crosslinking using an inert gas discharge. The stability of the wettability, adhesion, and mechanical properties of treated polypropylene (PP) has been investigated by a comparative study of two different plasma treatments (i.e. an NH3 plasma and a He plasma pretreatment carried out before the NH3 plasma; He plasma is well known to crosslink polymer surfaces). The aluminium-polypropylene (Al-PP) interfaces present very different features depending on the gas treatment. The role of the treatment time has been pointed out and under our experimental conditions, a treatment time of the order of a few seconds seems to be an overtreatment leading to degradation of the adhesion and mechanical properties. A broad interphase was ob...

Insitu Metallization of Polypropylene Films Pretreated in a Nitrogen Or Ammonia Low-pressure Plasma

Abstract The polypropylene films are pretreated in a nitrogen or ammonia low-pressure plasma in order to improve their adhesive properties towards an in-situ deposited aluminium coating. The treatment conditions are similar to industrial ones and treatment times as short as 23 ms allow a considerable improvement of the adhesion between the polypropylene and the aluminium. The aim of this work is to understand better the mechanisms involved in the adhesive phenomena. Indeed, the modifications created by the plasma (for very short treatment times) are not easily detected. SSIMS has revealed the presence of a thin non-homogeneous film of light-weight hydrocarbons on the non-pretreated polymer. This film is responsible for the non-adhesion of the aluminium coating onto the polymer. Actually when this film is removed by a cleaning process induced by the plasma, the interactions between the aluminium and the polypropylene are strong enough to allow a good adhesion. This explains one of the effects of the plasma and more experiments will be carried out in order to determine the key factor of the phenomenon: the role of the oxygen at the interface on the treated polymer will be investigated as well as the diffusion depth of the treating gas.

Aluminium Metallization of Polypropylene Films Pretreated by a N2 or NH3 Nonequilibrium Plasma. Study of the Interface and Adhesion Measurements

The adhesion of thin aluminium coatings (≈ 20 nm) to 8 μm isotactic polypropylene films has been improved by pretreating the films in a low pressure nitrogen or ammonia plasma before in situ metallization. In the case of an ammonia plasma for treatment times as short as 0.023 s, nitrogen was detected by XPS; whereas in the case of a nitrogen plasma for treatment times less than 0.7 s, we had to use SSIMS in order to follow the nitrogen uptake of the surface. Optical emission spectroscopy has been used to characterize both the ammonia and nitrogen discharges. The higher nitrogen uptake of the surface in the case of the ammonia plasma has been interpreted in terms of the reactivity of the NH species. With the help of a U-form peel test especially adapted to thin flexible substrates with thin metallic coatings, the optimum treatment time was determined (around 1 sec.) and measured peel strengths were two times higher for NH3 treated surfaces as compared to N2 treated ones. For treatment times exceeding the optimum duration, the adhesion degraded and the extent of metal peeled off increased. For such treatment times, AES shows broader interfaces.