Effectiveness of A Simple Image Enhancement Method in Characterizing Polyethylene Foam Morphology using Optical Microscopy

A simple image enhancement technique was proposed to observe and analyze cell structure of polyethylene foams using optical microscopy. Two coating techniques were implemented in this study; one being a simple black soot coating and the other utilized a commercial Au/Pd coating that is commonly used for Scanning Electron Microscopy (SEM) observation. The former technique was forwarded after considering that when the sample is white in color, usually microscopic observation via optical microscopy is quite difficult. Polarized light was also applied as another supporting tool to counter the light reflectance problem occurred in the observed white sample. Good quality digital images were successfully produced using both coating techniques with the assistance of polarized light projected via the optical microscope. It was proven that the sample with the proposed black soot coating is able to give high quality image with high level of contrast. The results showed that images with clear cell boundaries were obtained and these images were comparable or much better than those obtained with the Au/Pd coating technique. Finally, images with improved contrast were inverted using an image analysis procedure which allows better determination of foam cell features in polyethylene foams. The use of the proposed technique as supplementary device for real-time microscopic observation during foam compression was also proven to be a success.