Fluorescence confocal microscopy as effective testing method of polypropylene fibers and single polymer composites

Single polymer composites are special type of composite made solely of one polymer. They are characterized by promising mechanical properties but the manufacturing process is very difficult to scale to mass production. In this paper a method of testing polymer fibers and single polymer composites was developed. The method provides fast and nondestructive detection of structural defects in fibers and delamination in single polymer composites, therefore it can be applied to quality control of the fibers as well as composites. The method based on the laser scanning confocal microscopy, that uses laser to scan the surface of the specimen and detect light of wavelength longer than laser beam. The results show that the luminescence occur only in the defected or delaminated spots of the sample. Raman and IR spectroscopies were used to analyze the source of the luminescence. The study indicates that the influence of impurities, additives and effects of chemical degradation of polymer doesn't lead to luminescence of the specimen. As the explanation of the effect mechanical stress assisted photoluminescence was proposed.