Novel toughened automotive clearcoats modified by a polyester-amide hyperbranched polymer: structural and mechanical aspects
Article first published online: 12 FEB 2013
Copyright © 2013 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies
Volume 24, Issue 5, pages 495–502, May 2013
How to Cite
Yari, H., Mohseni, M., Ranjbar, Z., Messori, M. and Naimi-Jamal, M.R. (2013), Novel toughened automotive clearcoats modified by a polyester-amide hyperbranched polymer: structural and mechanical aspects. Polym. Adv. Technol., 24: 495–502. doi: 10.1002/pat.3110
- Issue published online: 16 APR 2013
- Article first published online: 12 FEB 2013
- Manuscript Accepted: 7 JAN 2013
- Manuscript Revised: 5 JAN 2013
- Manuscript Received: 27 NOV 2012
- hyperbranched polymers;
- mechanical properties;
The present work attempts to study the mechanical properties and toughness behavior of a typical acrylic melamine clearcoat modified by a polyester-amide hyperbranched polymer (HBP). Formulations were such that 0, 5, 10, 25 and 50% (molar percent) of total acrylic hydroxyl groups were stoichiometrically substituted by those of HBP. Bulk and surface of the clearcoats were studied by various mechanical techniques including hardness, tensile, dynamic mechanical thermal analysis (DMTA), nano-indentation and scratch tests. In addition a scanning electron microscope (SEM) was utilized to observe the morphology of the fractured films. The bulk mechanical properties showed that a low loading (5 molar %) of HBP was sufficient to considerably increase the bulk hardness, cross-linking density and toughness. DMTA and SEM results proved the occurrence of a single-phase blend and that the shear deformation was the main toughening mechanism of HBP modified clearcoats. In general, it was revealed that the HBP not only could act as an excellent compatible toughening agent, but also maintained the clarity of the clearcoat and increased its scratch resistance. Copyright © 2013 John Wiley & Sons, Ltd.