Louis Vovelle

Adhesion of latex films. Part III. Surfactant effects at various peel rates

In order to study the effect of surfactants on the adhesion of latex films, peel energy versus surfactant concentration curves were established at various peel rates. The main latex polymer was a methyl methacrylate (MMA)/ethyl acrylate (EA) copolymer synthesized in the presence of a hydrophilic polyester. Another polymer, less extensively studied, a styrene/butyl acrylate/methacrylic acid terpolymer, was also used for comparison purposes. The surfactants were either sodium dodecyl sulfate (SDS) or ethoxylated nonyl phenol containing 30 segments of ethylene oxide (NP30). The substrates were glass plates or poly(ethylene terephthalate) films. It was found that with SDS-containing films, whatever the substrate or the polymer, the curves went through a maximum, whereas with NP30 they went through a minimum, at medium or high peel rates. When the peel rate was decreased, the curves flattened out and at zero peel rate (extrapolated values), they became horizontal. The peel energies at zero peel rate were three...

Evaluation of mechanical properties and adhesion of polymer coatings by continuous hardness measurements

Two grafted acrylic latex coatings with different glass transition temperatures-one glassy, one rubber-like-were coated onto a polyethylene terephthalate (PET) film in order to obtain new surface properties. The mechanical properties of the coatings were evaluated by continuous hardness measurements. The behaviour of the glassy coating can be defined as elastoplastic and we can analyse the indentation curves using the classic equations developed for elastoplastic materials. In the case of the rubber-like coating, the indentation curves are very different. There is no plastic deformation and the coating adheres to the indenter. We propose a model to calculate the Youngs modulus of the rubber-like coating from these indentation curves. The same experimental set-up was used to perform indentation debonding tests in order to study the influence of the mechanical properties on the adherence of the coatings to the substrate. The rubber-like coating, which has weak mechanical properties, adheres to the PET subs...

Adhesion of latex films. Part II. Loci of failure

In order to continue our work on surfactant effects on the adhesion properties of latex films, we investigated a new system based on an acrylic copolymer, synthesized in the presence of a hydrophilic polyester. The surfactants were either sodium dodecyl sulfate (SDS) or an ethoxylated nonyl phenol containing 30 ethoxy groups (NP30). As substrates, either glass plates or poly(ethylene terephthalate) (PET) films were used. This article describes the analysis of the loci of failure after peeling of the films. The analytical techniques used were X-ray photoelectron spectroscopy (XPS) (or ESCA), static secondary ion mass spectrometry (SSIMS), and contact angle measurements. It was shown that the loci of failure were independent of the peel rate and of the nature of the substrate. The failure occurs in a thick surfactant layer for SDS, and in a thin one for NP30. The thickness of the layer increases with the concentration of surfactant in the latex film. The surfactant is located near the surface of the substra...

Synthesis and Characterisation of New Structured Latices for Improved Adhesion to Polyester Films

The paper describes the synthesis, in an emulsion polymerisation process, of an acrylic copolymer, poly(methyl methacrylate-co-ethyl acrylate), in the presence of a hydrophilic polyester. This polyester has a structure close to that of poly(ethylene terephthalate) (PET) but is made hydrophilic by sulphonate-bearing moieties. It was specially designed to promote the adhesion of latex films to PET. In water, it forms aggregates with a mean diameter of 20nm. These aggregates act as seed particles and the synthesis proceeds like an inverted core-shell emulsion polymerisation. The hydrophilic polyester forms the main component of the shell of the final latex particles. The acrylic copolymer is located mainly in the core. Despite the strong incompatibility between the two polymers, they mix to a certain extent, as clearly shown by the analysis of the mechanical properties of the latex films. This unexpected mixing is due to the synthesis procedure. The acrylic monomers are added slowly and polymerise as soon as they reach the seed particles, before having time to completely phase-separate from the polyester. Knowledge of the particle and latex film structure is used to interpret adhesive properties of the latex films.