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Bridging polymer synthesis and ease in processing

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Abstract

High Performance polymeric materials are a subject of considerable interest due to their high mechanical performances when combined with their versatility in processing and synthesis. In order to achieve high mechanical properties, scientist focuses on increasing the molecular weight of the polymer produced. A striking example is polyethylene. When having a molar mass of approximately 10^3-10^4 g/mol, it is soft a material and it is used for films and packaging; when the molecular weight increases over 10^6 g/mol (also called ultra-high molecular weight polyethylene - UHMWPE) it becomes extremely hard and it is used in ballistic and in high modulus/high strength applications. However, on increasing the molecular weight, also the viscosity increases due to the large number of entanglements in the non-crystalline region of the semi-crystalline material. The current state-of-the-art in processing this material is by partial dissolution of a small amount of polymer (~5-10 wt. %) in organic solvents in order to reduce the entanglements [1]. A recent development in the processing of the UHMWPE is achieved by direct synthesis of the polymer having a reduced amount of entanglements. By tailoring the reaction conditions during synthesis and making a meticulous choice of the catalytic system, it is possible to synthesise disentangled-UHMWPE. The disentangled-UHMWPE can be uniaxial as well as biaxial solid-state processing without using any solvent. The resulting solid-state processed tapes have unprecedented breaking tenacity (>4.0 GPa) and tensile modulus (> 200 Gpa) [2]. The fundamental concept of processing lower entangled high molecular weight polymers is of general nature and can be potentially applied for all the polymeric materials. The current research activity is focusing on testing different catalytic systems for the synthesis of the first solid-state processed biobased tapes and/or fibres for high breaking tenacity and high modulus applications.
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Original languageEnglish
Publication statusPublished - 2017