Surface crystallinity of meltspun isotactic polypropylene filaments

In this study, surface crystallinity of meltspun polypropylene (PP) filaments was reported. Results obtained from attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were confirmed with tapping mode atomic force microscopy (TM-AFM) analysis. ATR-FTIR tests were performed directly on longitudinal surfaces of the filaments, where IR radiation penetrates up to a specific depth. TM-AFM measurements were done on microtomed cross-sections of the filaments, which were scanned carefully to investigate stiffness. Annealing enhanced the surface crystallinity of the filaments in a significant way. Interestingly, samples annealed at 70 and 110 °C for 12 h exhibited similar crystallinity on the uppermost 500 nm surface, whereas for the bulk a continuous increase was observed after XRD studies. 12 h annealing at 70 °C modified the endothermic thermogram, while it did not causes significant effect on overall bulk crystallinity. Differences in the behavior of surface and bulk of the fibrous materials should be considered particularly for surface treatment, i.e. plasma, corona discharge, chemical vapor deposition. Results are also pertinent for water and dye absorbency in polymers. [Figure not available: see fulltext.]