Fibers of Ultra-High Molecular Weight Polyethylene Obtained by Gel Spinning with Polyalphaolefin Oil
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Article www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673
Fibers of Ultra-High Molecular Weight Polyethylene Obtained by Gel Spinning with Polyalphaolefin Oil Instituto de Macromoleculas Eloisa Mano, IMA, Universidade Federal do Rio de Janeiro, Naiara Pirahi da Silva Chagas, Av. Horacio Macedo, 2030, CT Bloco J, RJ, Brazil Geíza Lopes da Silva Fraga, Maria de Fátima Vieira Marques* Received March 29, 2020 / Revised July 2, 2020 / Accepted July 12, 2020
Abstract: The rapid growth of polymer technology has provided viable and more straightforward methods for the development of ultra-high molecular weight polyethylene (UHMWPE) fibers. The gel spinning process yields fibers with improved properties and less impact on the environment. The material used as a solvent for the swelling of the polymer reveals an excellent potential for the processing of new fibers. In the present work, the influence of a new spinning solvent based on polyalphaolefin (PAO100) in the UHMWPE was evaluated. All fibers were obtained by extrusion in concentrations of 0.04 to 60% m/m of PAO100 oil, with screw rotation speed increasing from 20 to 60 rpm, leaving the extruder nozzle of 1.82 mm. Besides, n-hexane was used in the process of extracting oil from UHMWPE fibers. The fibers did not undergo to the drawing process. The results show that the fibers containing 20-40% m/m of PAO100 presented higher linear density, indicating the orientation of the crystals in a compact morphology and the higher relaxation after leaving the nozzle, increasing die-swell. After extraction of PAO100 with n-hexane, huge voids were observed in SEM images, which indicates the alignment of subfibers inside the fiber. The average size of the crystallite related to the polyethylene orthorhombic crystal increased significantly, showing that the number of entanglements decreased. The results indicate that PAO100 oil acts as a lubricant, increasing the mobility of the chains, leading to higher crystallization. The present study presents exciting findings on the effects of PAO100 oil on the morphology, crystalline structures, and thermal properties of UHMWPE fibers, pointing out the oil concentration necessary for the formation of fibers with higher crystallinity and thermal resistance. Keywords: ultra-high molecular weight polyethylene (UHMWPE), fibers, polyalphaolefin, gel spinning, twin-screw extruder.
1. Introduction Ultra-high molecular weight polyethylene (UHMWPE) is a white, opaque, semicrystalline polyolefin, which is produced in the form of the powder obtained by the slurry polymerization technique, similar to other thermoplastic resins such as high-density polyethylene (HDPE), but without the step of pelletizing1,2 since the molten polymer is not able to flow. It has a very high molar mass and is available in three ranges: low (3 million g/mol), medium (5 million g/mol), or high molar mass (7 to 10 million g/mol).3,4 Also, it has remarkable physical and chemical properties, such as excellent abrasion resistance, impact and fatigue, self-lubricating property,
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