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

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

Merseburg

Congreso; PolyMerTec 2018; 2018

Hochschule Merseburg

Over the last decades, as a result ofenvironmental concerns and regulations, there is a growing interest in academy,industry and consumers in the use of biodegradable polymers derived fromnatural resources. Among biobased polymers, poly(lactic acid) (PLA), a biodegradablealiphatic thermoplastic polyester, has a number of characteristics which makeit unique in the marketplace. First, the starting material, lactic acid, can beproduced by fermentation of 100% annually renewable resources. In addition, PLAcan be designed to controllably biodegrade, with a CO2 generationbalanced by the amount taken from the atmosphere during the growth of plantfeedstocks. Apart from its origin and biodegradability, the extensiveapplication of PLA in packaging, paper coating, fibres, films, and mouldedarticles is mainly due to its high modulus, strength and transparency; being inmany applications a cost-effective alternative to commodity petrochemical-basedplastics. Depending on the stereopurity of the polymer backbone, PLA can besemi-crystalline or totally amorphous. PLA can be stress crystallised,thermally crystallised, impact modified, filled, copolymerised, and processedin most polymer processing equipment. It can also be formed into transparentfilms, fibres, or injection moulded into blow mouldable preforms for bottles[1-3]. When a polymer crystallisesupon drawing, such as in solid state drawingat temperatures between the glass transition and melting temperatures, molecularchains are highly oriented in the strain direction, the material propertiesbecome anisotropic and stiff and strong fibres can be obtained. In this work, different extruded filaments based onPLA (neat PLA, PLA/copper or PLA/carbon black) were subjected to solid statedrawing to obtain fibres. The effect of the processing temperature and drawratio on the fibres morphology, thermal and mechanical properties wasinvestigated. In addition, a model based on the Finite Element Method wascarried out to determine the temperature profiles of the filaments during drawingand simulated profilesweresubsequently compared withexperimental measurements by infrared thermography.