Hyperbranched Aliphatic Polyesters as Thermoset Resins for Thermally Cured Coil-Coatings
(English)Manuscript (Other academic)
Two hydroxy-functional hyperbranched aliphatic polyesters based on 2,2-dimethylol propionic acid (bis-MPA) and a partially aromatic conventional polyester have been studied as thermoset resins for solvent-borne thermally cured polyester cross-linked with melamine coatings for pre-coated sheet metal, i.e. coil-coatings. The hyperbranched polyesters differ with respect to ratio of the end-groups being either hydroxyls or alkyl esters. The rheological properties of formulations with different polyester resin composition and reactive diluent, i.e. rape seed methyl ester (RME), content have been evaluated with viscosity measurements. Films cured either under industrial cure conditions to obtain a peak metal temperature (PMT) of 232-241°C or at a lower temperature, i.e. 130°C, on untreated or organic primer coated hot dipped galvanized (HDG) steel substrates have been prepared. The film properties have been evaluated with differential scanning calorimetry (DSC), and conventional film characterization techniques i.e. adhesion, impact, Erichsen cupping, pencil hardness, micro hardness, scratch and chemical resistance tests. Formulations possessing high drying ability with maintained suitable film application viscosity were obtained using a hyperbranched polyester resin and a reactive diluent. It is proposed that a solvent-free polyester/melamine formulation with sufficient film properties to withstand the rough forming procedures associated with coil-coatings can be obtained by further modification of the resin and greater amounts of reactive diluent.
Hyperbranched polyester resin, fatty acids, reactive diluents, coatings, thermal curing, film properties
IdentifiersURN: urn:nbn:se:kth:diva-4853OAI: oai:DiVA.org:kth-4853DiVA: diva2:87
QC 201008172008-09-042008-09-042010-08-17Bibliographically approved