Gilles Lorentz

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.