Transcrystallization, enhanced interface strength and mechanical properties in PE/(PA6 nanofiber)/graphene oxide thermoplastic polymer-polymer nanocomposites via annealing and increased remolding temperature

Abstract

The importance of polymer-polymer thermoplastic composites is increasing due to ease of recycling. This work investigates the effects of remolding temperature and thermal annealing on the properties of polyethylene (PE) composites containing PA6 and GO/PA6 electrospun nanofibers. Nanocomposite samples were prepared by sandwiching several layers of PA6 or GO/PA6 electrospun mats and PE films in a hot press and subsequently were remolded at varying higher temperatures in a range of 180 to 210°C. Furthermore the remolded samples at 200°C were then annealed at 100°C for 10 h. SEM and DMTA results of the developed samples showed that the application of higher remolding temperatures, close to the melting point of PA6, improves wettability and interfacial strength in the composites. The DSC results of the samples revealed a slight increase in PE crystallinity due to the induced crystallization on the surface of nanofiber mat. It was also observed that an increase in the remolding temperature increases the tensile properties of the composites with the best properties obtained at a remolding temperature of 200°C. Increasing the remolding temperature beyond 200°C decreases the tensile properties of the composites due to melting and geometry degradation of the nanofibers. The results revealed that the annealing of the samples at 100°C for 10 h increases the degree of crystallinity and tensile properties. The highest yield strength, 16.4 MPa, and modulus, 277 MPa, were obtained for the composite containing 10.5 wt% of pure PA6 nanofibers. The elongation and toughness of this composite compared to those of pure matrix were increased by 61% and 83%, respectively. In the remolded and annealed nanocomposites, a crystalline region, as thick as 20 microns, grown on the surface of the nanofiber mat or nanofiber rich region, so called transcrystalline region, was observed by polarized reflected light microscopy.