Martin Melchiors

Recent developments in aqueous two-component polyurethane (2K-PUR) coatings

Abstract In the field of environmentally friendly coatings waterborne two-component polyurethane systems represent a new technology, combining the good film properties of solventborne two-component polyurethane coatings with the low VOC values of waterborne technology. Recently, waterborne two-component polyurethane coatings have matured to the point that they offer realistic alternatives to the corresponding solventborne systems in various application fields. For industrial finishing and automotive refinish we are introducing rapid drying coatings exhibiting well-balanced range of properties at low VOC level. We developed high-performance OEM-clearcoats which combine good chemical resistance with excellent mar resistance. Waterborne soft-feel lacquers are already well established in the market. Development of a new generation of water dispersible polyisocyanates as well as improvements in application technology have contributed substantially to this. Additionally, progress in understanding the fundamental principles of aqueous two-component-PUR systems like side reactions during pot life and film formation or the cause of blistering supported our developments. We expect that waterborne two-component polyurethane coatings will gain a significant share of the market where high-performance coatings are demanded.

Preparation and properties of solid electrolytes on the basis of alkali metal salts and poly(2,2-dimethyltrimethylene carbonate)-block-poly(ethylene oxide)-block-poly(2,2-dimethyltrimethylene carbonate)

Abstract The dissolution of alkali metal salts, e.g. LiClO 4 , LiCF 3 SO 3 , NaSCN, NaI, NaCF 3 SO 3 and KSCN in poly(2,2-dimethyltrimethylene carbonate)-block-poly(ethylene oxide)-block-poly(2,2-dimethyltrimethylene carbonate) (PDTC- b -PEO- b -PDTC) results in solid polymeric electrolytes. Depending on the nature of the salt, differential scanning calorimetry (d.s.c.) measurements of the polymer/salt systems reveal that crystalline complexes are obtained with NaI, NaSCN, and LiCF 3 SO 3 . These complexes exhibit characteristic infra-red (i.r.) bands, e.g. at 1106 and 1080 cm −1 for the complex with NaI. X-ray powder diagrams of the polymer/salt complexes show that the original patterns of the salt and the crystalline PEO phase have disappeared in favour of a new pattern for the complex; however, reflections attributed to the crystalline PDTC phase are found to be unchanged. Complexation takes place mainly with the PEO segments of the block copolymer, thus causing a change in the secondary structure of the original PEO helix. The stoichiometry of the polymer/salt complexes is 3 1 (EO repeating units/metal cation). The highest value of the alternating current conductivity was obtained for LiCF 3 SO 3 as the salt component, with values of σ = 10 −4 S cm −1 at 60°C being obtained at concentrations of 5 to 10 mol% (based on the EO repeat units). From temperature dependent conductivity measurements it was concluded that above the glass transition temperature the ionic conductivity of the sodium salt systems follows an Arrhenius behaviour, while the lithium and potassium salt systems follow a Vogel-Tammann-Fulcher behaviour.

Serientauglich: 2-K-Wasserklarlack für die Automobil-Lackierung

Neue Rohstoffe und eine optimierte Dispergiertechnik machen den Einsatz von wassrigem 2-K-Polyurethan- Klarlack fur die Automobil-Serienlackierung interessant. Wir stellen die Neuentwicklungen vor.