Dupont researchers Li Lin and Greg Blackman described how the new method permits them to examine tiny scratches as they develop in real time. Similar to the minuscule scratches that can occur when you wash your car, the micro-scratches are extremely tiny. "A human hair laid up against one of these scratches would dwarf it," Blackman says.
The combination of many of these tiny scratches allows light to scatter over the coating, making the damage visible to the human eye, and leading to what the two researchers call an "objectionable appearance" that doesn't meet the auto industry's goal that cars retain their visual appeal for 10 years.
Examining the mechanical properties of the polymer during the formation of such small scratches, or swirl marks as they are often called, required an analytical device that was not commercially available. Lin developed a unique micro-scratch tester that was then coupled with an atomic force microscope and a video camera, thereby allowing real-time examination of scratches as they developed.
One surprising finding for the scientists was that in the early stages of scratch formation there is no loss of material, or debris formation. Rather, small cracks appear and create voids in the surface of the coating, which cause the scattering of light.
Based on their work, new coatings that Blackman describes as "significantly better" already have been applied to some cars for field testing. The analytical device developed by Lin has been licensed for development by CSEM Instruments (Centre Suisse d'Electronique et de Microtechnique SA) of Switzerland.
Dr. Blackman and Dr. Lin will present their papers, POLY 590 and POLY 593, on Thursday, August 27, from 9:30 a.m. - 10:00 a.m. and from 11:10 a.m. - 11:30 a.m., respectively, at the Westin hotel, Essex Northwest, 3rd Floor
For further information, contact:
Nancy Blount at (202) 872-4451. From August 20-27: Press Room , Convention
Center, Room 308 Phone: (617) 351-6808; FAX: (617) 351-6820
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