MSE Seminar Series: Aaron Forster
Friday, December 6, 2013
1:00 p.m.-2:00 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg
Scratch and Mar Resistance in Coatings via Microstcratch and Optical Scattering Metrologies
Aaron M. Forster
Materials Research Engineer, Polymeric Materials Group
Materials and Structural Systems Division
Scratch and mar resistance is important for the performance of coatings and composites used as a glossy protective layer in consumer products. These products include a wide range of material systems including crosslinked polyurethane and epoxy coatings for wood floors and automotive paints to semicrystalline polyvinylidene fluoride (PVDF) coatings for exterior architectural applications. The coatings are expected to remain damage free by resisting environmental and wear damage over the lifetime of the product. Creating a material that both resists all scratch damage, but meets optical clarity requirements is not trivial. The formulator is required to balance stiffness, hardness, and viscoelasticity to optimize physical properties, while maintaining optical properties. This is a daunting task for a formulator without the tools to assess scratch resistance in a quantifiable manner.
There are two challenges in the assessment of scratch and mar resistance in coatings. The first is the development of a repeatable methodology to induce damage at the surface of a coating. The second is a reliable methodology to quantify scratch visibility as a function of damage. NIST has developed a methodology that addresses both challenges and is applicable to a variety of material systems. This talk will describe this methodology and provide examples of the role coating properties play in scratch visibility. A model epoxy will used to demonstrate the connection between viscoelastic properties of the network and scratch damage. A semicrystalline PVDF will be used to demonstrate the impact of semi-crystalline microstructure on visibility.
About the Speaker
Dr. Forster received his doctorate in Chemical Engineering from Clemson University in 2002. After school, he worked on combinatorial methods for surface adhesion measurements as an NRC post-doctoral research in the Polymers Division at NIST. He joined the staff at the National Institute of Standards and Technology in 2005 working in the Polymeric Materials Group of the Building and Fire Research Laboratory. The Polymeric Materials Group has focused on the development of metrologies and instruments to accelerate environmental and wear degradation of polymer coatings and composites in support of more accurate service life prediction models. Dr. Forster was a co-director of the Polymer Interface Consortium at NIST. This consortium of seven companies developed a suite of metrologies utilizing indentation, confocal microscopy, Raman spectroscopy, and surface light scattering to quantify the impact of microstructure, chemistry, and scratch conditions on the visibility of scratch damage. Dr. Forster has worked with ASME to develop a research and development roadmap for the acceptance of large diameter polyethylene pipe in safety critical water cooling applications for nuclear power plants. This roadmap led to the application of Coherent Anti-stokes Raman Spectroscopy to investigate the crystalline morphology of bimodal polyethyelene resins used in pipes. Dr. Forster is addressing gaps within this roadmap by using cohesive zone crack models for the durability of polyethylene fusion joints. Recently, Dr. Forsters research group is utilizing the conductive properties of carbon nanotube networks to measure damage tolerance in hybrid carbon nanotube fiber composites.