Influence of polymer type, composition, and interface on the structural and mechanical properties of core/sheath type bicomponent nonwoven fibers

In this study, we investigated the effect of polymer type, composition, and interface on the structural and mechanical properties of core–sheath type bicomponent nonwoven fibers. These fibers were produced using poly(ethylene terephthalate)/polyethylene (PET/PE), polyamide 6/polyethylene (PA6/PE), polyamide 6/polypropylene (PA6/PP), polypropylene/polyethylene (PP/PE) polymer configurations at varying compositions. The crystallinity, crystalline structure, and thermal behavior of each component in bicomponent fibers were studied and compared with their homocomponent counterparts. We found that the fiber structure of the core component was enhanced in PET/PE, PA6/PE, and PA6/PP whereas that of the sheath component was degraded in all polymer combinations compared to corresponding single component fibers. The degrees of these changes were also shown to be composition dependent. These results were attributed to the mutual interaction between two components and its effect on the thermal and stress histories experienced by polymers during bicomponent fiber spinning. For the interface study, the polymer–polymer compatibility and the interfacial adhesion for the laminates of corresponding polymeric films were determined. It was shown that PP/PE was the most compatible polymer pairing with the highest interfacial adhesion value. On the other hand, PET/PE was found to be the most incompatible polymer pairings followed by PA6/PP and PA6/PE. Accordingly, the tensile strength values of the bicomponent fibers deviated from the theoretically estimated values depending on core–sheath compatibility. Thus, while PP/PE yielded a higher tensile strength value than estimated, other polymer combinations showed lower values in accordance with their degree of incompatibility and interfacial adhesion. These results unveiled the direct relation between interface and tensile response of the bicomponent fiber.