Optical Diffraction Unit to Monitor On-Line Deformation of Polymers
Ferenc Cser, Mike Allan, Sati, N. Bhattacharya
Rheology and Materials processing Centre, School of Civil and Chemical Engineering, RMIT
Australia
Keywords: optical, diffraction, melt
An Optical diffraction device with a solid-state red laser of 1 mW output power was built and used to record on-line the two-dimensional scattering pattern of polymers during extensional deformation.
The laser unit, the screen to capture the scattering intensities and the recording digital camera were mounted on an optical bench. The laser light was pin-holed to filter all non-coherent radiation and focused to the sample to be tested. The distance between the sample and the screen prepared from a translucent matt film was 60-100 mm depending on the experimental condition. The camera was fixed 3500 mm from the screen in transmission position. Reduced background light recording and manual focusing were used to record scattering data.
The optical diffraction unit (ODU) described above was mounted to Instron tensile testing equipment as well as to Rheotest Melt Strength Tester and the scattering intensities were recorded during the test. The scattering intensities depended on the material used. Generally the extensionally deformed solid and molten polymers as well as nanocomposites produced anisometric diffraction patterns.
The two-dimensional scattering intensities were transferred to individual graphic patterns and their red component was read using software written for this purpose. The patterns were then processed as two-dimensional scattering intensities using particle scattering concepts. Characteristic particle sizes were obtained between 0.2 and 30 mm of radius of gyration. The ratio of the dimensions of inhomogeneity in parallel with and perpendicularly to the direction of extension was calculated and analysed