QUICK
FACTS
- Applications of X-ray scattering to soft matter have advanced considerably within recent years, both conceptually and technically
- Mature high-power X-ray sources, synchrotrons and rotating anodes, as well as high-speed detectors have become readily available
- High-quality time-resolved experiments on polymer structure can now be performed with ease, a major advancement due to the genuine power of the scattering method
- Dr. Norbert Stribeck, of the Institute of Technical and Macromolecular Chemistry from University of Hamburg in Germany, uses PV-WAVE Advantage to simulate and analyze the properties of polymer materials
THE PROBLEM
Many polymer materials are built from hard domains embedded in a softer matrix. Layers, cylinders, or spheres are observed. A typical diameter is 50 nm. These domains are forming and changing during processing and service. Dr. Stribeck and his colleagues study and document the evolution mechanisms of this nanostructure as revealed from X-ray scattering images recorded during materials processing. New theoretical approaches for model-free evaluation and interpretation of multidimensional scattering data are developed by a combination of the fields of scattering theory, digital image processing, and applied physics.
During straining cycles the material is irradiated and scattering images using a CCD camera are continuously taken. The main question is then what happens inside the material?
Fig. 1: CVJ boot made from Arnitel® (source: DSM Inc., The Netherlands)
Fig. 2: A plastics part is strained. Irradiation by X-rays causes a scattering image
Fig. 3: Monitors showing (from left to right) the sample, the scattering pattern, and the stress-strain cycling
THE SOLUTION
Images and their experimental parameters must be kept together in a structure. Pre-evaluation of scattering patterns is typical in digital image processing: for example, rotating, filling, and transforming. Nanostructure images are then computed by methods similar to those well-known from tomography in the field of medicine. The edges of the hard (polyester) domains in the (polyether) matrix are enhanced. Finally a video exhibits how the nanostructure reacts upon strain: Polyester domains are split into small cylinders which are suspended from polyether threads of all the same length. Thus, they move on paths that are inclined with respect to the drawing direction. As the strain is released, the cylinders merge again – but now in a different arrangement. This is the reason for plastic deformation.
Dr. Norbert Stribeck and his colleagues started to use PV-WAVE in 1996 after he and their former collaboration partner at DuPont Inc., Wilmington, USA had compared several matrix oriented computing languages. They compared the languages by using 60 GB of image data and evaluated the results.
“We needed a flexible and robust container for the image and its environmental data that can be defined on an abstract level. Such a container is readily implemented as a ‘structure’ of PV-WAVE. We have learned much about digital image processing from the PV-WAVE printed manuals – how to automatically clean masks by ‘closure for example’. We benefit from the interpreter concept, which allows very short development cycles. Furthermore, automation is simple, once the flow of data into the PV-WAVE structure is adapted to the actual experiment,” Dr. Stribeck says.
Using the visualization options of PV-WAVE they were able to browse each recorded experiment in different presentations of nanostructure. This is an efficient way to approach interesting transitions and to understand the mechanisms of nanostructure evolution. “Today we still benefit from the flexibility of PV-WAVE,” stated Dr. Stribeck.
RETURN ON INVESTMENT
Today the Polymer Physics Group at the University of Hamburg is no longer the only academic group of polymer scientists working with PV-WAVE procedures. Since 2006, additional colleagues at the Institute of Polymer Research IPF Dresden have joined them. Their main operating environment is a Microsoft Windows XP platform, but they also have experience with PV-WAVE on other platforms (IRIX, Linux: SuSE, Kubuntu). Results of the research are in the papers (cf.
http://www.chemie.uni-hamburg.de/tmc/stribeck/pub), and examples are presented in a textbook, N. Stribeck, “X-Ray Scattering of Soft Matter” (2007) Springer Publishers, Heidelberg, Berlin & New York,
http://www.stribeck.de/scatsoft.
