In situ monitoring of polymer crystallization with PS-OCT

With the introduction of optical coherence tomography (OCT) in the early nineties a novel measurement method was presented exhibiting promising potential for high resolution, contact-free imaging of translucent specimens. Biomedical diagnostics - being the main (and nearly exclusive) driving force for the developments of the OCT method - took soon advantage of new kinds of alternative contrasting techniques and enhanced imaging extensions used in combination with the low coherence interferometry detection principle of OCT. Astonishingly, OCT and its advanced extensions and derivates were (and still are) rather unknown outside the field of biomedical diagnostics, although all its characteristics render OCT an attractive candidate for non-biological applications, as e.g. non-destructive testing of material structures and samples. Therefore, within the frame of the project, advanced techniques of optical coherence tomography will be combined and developed beyond the state- of-the-art, focusing on problems posed in material research and development. In detail, polarisation sensitive OCT (PS-OCT) will be performed with high-resolution at a centre-wavelength of 1.5 m to increase the penetration/imaging depth in typical materials, like polymers. As a light source, a pulsed micro-chip laser will be used in combination with a specially tailored photonic crystal fibre to obtain a suitable spectrum with the required width and shape for OCT imaging. In order to increase the imaging speed, spectral domain techniques will be applied together with PS-OCT and with the pulse rate of the light source synchronised to the read-out rate of the OCT detector. This novel system will be used for the in situ characterisation of dynamic processes, like polymer crystallisation: depth resolved PS-OCT birefringence measurements during cooling of polymer melts subjected to high shear gradients in a laboratory-scale extruder and slit die will be performed for the first time to gain deeper insight into the polymer crystallisation dynamics for refined theoretical models. In a second step, on-line PS-OCT monitoring will be used to investigate the polymer solidification behaviour on a large scale injection moulding machine under realistic processing conditions.

With the introduction of optical coherence tomography (OCT) in the early nineties a novel measurement method was presented exhibiting promising potential for high resolution, contact-free imaging of translucent specimens. Biomedical diagnostics - being the main (and nearly exclusive) driving force for the developments of the OCT method - took soon advantage of new kinds of alternative contrasting techniques and enhanced imaging extensions used in combination with the low coherence interferometry detection principle of OCT. Astonishingly, OCT and its advanced extensions and derivates were (and still are) rather unknown outside the field of biomedical diagnostics, although all its characteristics render OCT an attractive candidate for non-biological applications, as e.g. non- destructive testing of material structures and samples. Therefore, within the frame of the project, advanced techniques of optical coherence tomography will be combined and developed beyond the state-of-the-art, focusing on problems posed in material research and development. In detail, polarisation sensitive OCT (PS-OCT) will be performed with high-resolution at a centre-wavelength of 1.5 m to increase the penetration/imaging depth in typical materials, like polymers. As a light source, a pulsed micro-chip laser will be used in combination with a specially tailored photonic crystal fibre to obtain a suitable spectrum with the required width and shape for OCT imaging. In order to increase the imaging speed, spectral domain techniques will be applied together with PS-OCT and with the pulse rate of the light source synchronised to the read-out rate of the OCT detector. This novel system will be used for the in situ characterisation of dynamic processes, like polymer crystallisation: depth resolved PS-OCT birefringence measurements during cooling of polymer melts subjected to high shear gradients in a laboratory-scale extruder and slit die will be performed for the first time to gain deeper insight into the polymer crystallisation dynamics for refined theoretical models. In a second step, on-line PS-OCT monitoring will be used to investigate the polymer solidification behaviour on a large scale injection moulding machine under realistic processing conditions.