Relating the performance of one-component acrylic coatings with fundamental mechanical properties
Relating the performance of one-component acrylic coatings with fundamental mechanical properties Summary
One-component waterborne acrylic coatings are gaining importance in a number of application areas, such as decorative and industrial coatings. Most often,environmental considerations are the main driver in the switch from conventional solvent-borne, one- component coatings to waterborne alternatives. A fundamental difference between waterborne and solvent-borne coatings is the fact that films derived from a waterborne coating often display an internal morphology that has a pronounced effect on the coating performance. A number of one- component coatings have been analyzed by means of dynamic mechanical thermal analysis(DMTA) and the influence of parameters such as binder design and paint ingredients has been studied. Based on the results obtained, a methodology has been developed to assess the coatings performance based on the fundamental mechanical properties of the polymeric binder and the coating.
Introduction
Changes in the regulations concerning the emission of organic solvents across the globe have led to a growing interest in the use of polymer dispersions in high-performance waterborne coating systems. One-pack systems, using the current state-of-the-art cross-linking technology with control of the morphology of the particles in the polymeric dispersion have been studied extensively. A new generation of self cross-linking dispersions introduced into the market three years ago uses oligomeric acrylic stabilizers instead of low-molecular weight conventional surfactants. Nuplex Resins has developed a polymerisation process by which we can make these oligomeric stabilizers with acid numbers considerably lower than those of others described in literature. Furthermore, carbonyl groups are introduced in the polymer so the stabilizer can co-react with a cross-linker. In this way the stabilizing oligomer is built into the network formed by the self-crosslinking reaction. The oligomer also contains functional groups that allow grafting onto the second stage polymer.
Nuplex Resins is working with state-of- the-art, high-throughput resins synthesizers. These machines can make a multitude of dispersion samples in a very short time. However, all such samples have to be evaluated in a paint formulation and the coating properties have to be determined in the usual way. As paint formulating and testing is very time consuming, we have been looking into the possibility of predicting some of the key coatings properties using DMTA. The use of statistically designed experiments and the statistical analysis of both the DMTA and conventional paint data enable us to fine-tune the polymer design.
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