Light optical microscopy is the most used tool for the study of the polymer morphology. There are two important methods applied in light optical microscopy. The first one is based on light transmission through the sample and the second is based on reflection. Basically, both techniques are employed for surfaces studies. These methods include several procedures used for specific analysis. Usually, there are no treatments on the sample when light reflection technique is used to study material surface. However, a sample thin section must be prepared when light transmission techniques is used.
Light transmission technique is based on: natural light, polarized light, interference, darkfield, contrast methods, ultraviolet light and fluorescence. Light reflection technique is employed with natural light, polarized light, interference and fluorescence.
Polymer light absorption is very small in the region of electromagnetic spectrum. For this reason, direct observation optical microscopy is limited for systems with additives such as: stabilizers, pigments or reinforcement particles. Only their size and distribution can be determined in the matrix.
Special techniques are required for polymer structure observation. Contrast or darkfield techniques are some of them. Polarised light technique is applied to study crystalline morphology in polymers because this is based on material anisotropy.