Enhanced polymer coating processes and performance
Formation of films from water-based polymeric dispersions has become the processing method of choice in order to minimise the emission of volatile organic compounds (VOCs) produced from the use of organic solvents. Processing requires the use of compounds to reduce the surface tension of water (surfactants) to enhance stability. However, surfactants tend to cause performance problems in the final coating due to their tendency to form surfactant clusters. Recently, so-called reactive surfactants (surfmers) that become chemically attached to water-based film forming polymer (latex) dispersions during synthesis have been employed to inhibit clustering while retaining stability. However, most studies have focused on the macroscopic performance of the coatings as a result of surfmer use while investigation of molecular level solution microstructure and drying behaviour has been scarce. European researchers initiated the LATEX FILM Formation project to fill this knowledge gap and open the door to additional functionality of polymer film coatings. Researchers synthesised two surfmers structurally similar to the industry standard surfactant. The sulphonate surfmer, whose precursor was a renewable resource (an ingredient of cashew nut shell liquid), was characterised for this reporting period. Tests demonstrated enhanced characteristics (in particular, lower critical micelle concentration) of the sulphonate surfmer compared to the industry standard and the ability to form stable latex dispersions, supporting its viability as an alternative surfactant. In addition, the coating produced using the sulphonate surfmer exhibited new and attractive functionalities. Investigators developed a detailed molecular structural model of the co-polymer that gave insight into structure-function relationships and should be important in development of new surfmers. Continuing research should lead to additional improved surfmers based on renewable resources. Exploitation of the results has the potential to further decrease VOC emissions and enhance functionality and performance of polymer film coatings.
