Abstract
In this work, the influence of composition and cold-drawing on nano- and micro-scale morphology and tensile mechanical properties of PE/organoclay nanocomposite fibers was investigated. Nanocomposites were prepared by melt compounding in a twin-screw extruder, using a maleic anhydride grafted linear low density polyethylene (LLDPE–g–MA) and an organomodified montmorillonite (Dellite 67G) at three different loadings (3, 5 and 10 wt %). Fibers were produced by a single-screw extruder and drawn at five draw ratios (DRs): 7.25, 10, 13.5, 16 and 19. All nanocomposites, characterized by XRD, SEM, TEM, and FT-IR techniques, showed an intercalated/exfoliated morphology. The study evidenced that the nanoclay presence significantly increases both elastic modulus (up to +115% for fibers containing 10 wt % of D67G) and drawability of as-spun nanocomposite fibers. Moreover, at fixed nanocomposite composition, the cold-drawing process increases fibers elastic modulus and tensile strength at increasing DRs. However, at high DRs, “face-to-edge” rearrangement phenomena of clay layers (i.e., clay layers tend to rotate and touch each other) arise in fibers at high nanoclay loadings. Finally, nanocomposite fibers show a lower diameter reduction during drawing, with respect to the plain system, and surface feature of adjustable roughness by controlling the composition and the drawing conditions.
Highlights
The use of synthetic fibers is of widespread technological importance in different fields (textiles, sport goods, military and transportation sectors, concrete reinforcement, 3D printing by FusedDeposition Modeling (FDM), etc.) and attracts extensive research efforts aimed to continuously improving their properties and processability to produce high performance fibers [1,2,3].Among the many classes of synthetic polymer fibers, the market is dominated by polyamides, polyesters, acrylic and polyolefins
Morphology of As-Spun Fibers investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and attenuated total reflectance (ATR)-FTIR
The results obtained in this work allowed analyzing the relationships among composition, cold-drawing extent, morphology evolution and mechanical performance improvements in PE/clay nanocomposite fibers
Summary
The use of synthetic fibers is of widespread technological importance in different fields Even if several authors investigated the possibility of producing nanocomposite polyolefin fibers focusing on layered silicates as reinforcing filler, the combined effects of nanoclays addition and cold-drawing on the resulting morphology and fiber performances are rarely considered, in compatibilized systems [24,25,34]. Within this context, we performed a study designed to investigate the effects of fiber composition and cold-drawing ratio on the evolution of the fiber nano- and micro-scale morphology (clay intercalation/exfoliation level, polymer and clay orientation, polymer crystallinity, and fiber surface defects), using a maleated PE as matrix. Morphological and mechanical properties of the nanocomposite systems were analyzed by several techniques, i.e., X-ray diffraction (XRD), infra-red spectroscopy (FT-IR), electron and optical microscopy, and tensile mechanical testing, to evaluate the level of achieved benefits and fibers properties
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