Solid state drawing of Poly(lactic acid) (PLA) based filaments

M. GUSOVSKY; C. BERNAL; R. TELLIER; E. PÉREZ; J. WALKER; E. AGALIOTIS

Merseburg

Conferencia; PolyMerTec 2018; 2018

Technical University of Merseburg

Over the last decades, as a result of environmental concerns and regulations, there is a growing interest in academy, industry and consumers in the use of biodegradable polymers derived from natural resources. Among biobased polymers, poly(lactic acid) (PLA), a biodegradable aliphatic thermoplastic polyester, has a number of characteristics which make it unique in the marketplace. First, the starting material, lactic acid, can be produced by fermentation of 100% annually renewable resources. In addition, PLA can be designed to controllably biodegrade, with a CO2 generation balanced by the amount taken from the atmosphere during the growth of plant feedstocks. Apart from its origin and biodegradability, the extensive application of PLA in packaging, paper coating, fibres, films, and moulded articles is mainly due to its high modulus, strength and transparency; being in many applications a cost-effective alternative to commodity petrochemical-based plastics. Depending on the stereopurity of the polymer backbone, PLA can be semi-crystalline or totally amorphous. PLA can be stress crystallised, thermally crystallised, impact modified, filled, copolymerised, and processed in most polymer processing equipment. It can also be formed into transparent films, fibres, or injection moulded into blow mouldable preforms for bottles [1-3]. When a polymer crystallises upon drawing, such as in solid state drawing at temperatures between the glass transition and melting temperatures, molecular chains are highly oriented in the strain direction, the material properties become anisotropic and stiff and strong fibres can be obtained.In this work, different extruded filaments based on PLA (neat PLA, PLA/copper or PLA/carbon black) were subjected to solid state drawing to obtain fibres. The effect of the processing temperature and draw ratio on the fibres morphology, thermal and mechanical properties was investigated. In addition, a model based on the Finite Element Method was carried out to determine the temperature profiles of the filaments during drawing and simulated profiles were subsequently compared with experimental measurements by infrared thermography.