Mechanical recycling of polylactide: evaluation of recycling-induced degradation mechanisms and of the resulting deformation mechanisms for new applications


CALL: 2013

DOMAIN: MS - New Functional and Intelligent Materials and Surfaces

FIRST NAME: Frédéric

LAST NAME: Addiego




KEYWORDS: bioplastics, polylactide, reactive extrusion, extrusion, mechanical recycling, degradation, impact, tensile, deformation mechanisms, scale-up, life-cycle analysis

START: 2014-04-01

END: 2017-03-31


Submitted Abstract

The production of biobased plastics is expecting to increase by a factor of 5 in 2016 due to the increasing demand in these green materials as sustainable alternatives to petrobased-polymers. In this respect, polylactide (PLA) represents the most attractive biobased polymers for its biodegradability and excellent mechanical properties, being namely used for short-time applications (packaging), and more recently considered for long-term applications like automotive and electronics. However, its industrial implementation will require addressing the end-life scenario of these materials. Mechanical recycling and re-use of these materials afterwards rather than its direct composting will thereby provide a sustainable approach in order to yield new grades with reduced molecular weights, which can perfectly fit with numerous low-molecular-weight-required applications such as fiber, coating, and adhesive.DuraPLA project is hence focused on mechanical recycling of two PLA grades with different compositions: a reference grade and an original plasticized grade processed by reactive extrusion containing highly plasticized micro-domains dispersed within a slightly plasticized PLA matrix. This project aims specifically at i) identifying and quantifying the degradation mechanisms mediated or not in the presence of esterification catalysts of these two PLA grades resulting from lab-simulated mechanical recycling procedures, ii) studying the impact of recycling on the deformation mechanisms of these two grades, and iii) performing a pre-industrialization study of the recycling of PLA. The disruptive aspect of this project relies on an in-depth investigation of molecular structure, crystallinity, and micro-domains morphology evolution with the reprocessing cycle, and of the resulting chain orientation mechanisms, strain-induced crystallization, and matrix/micro-domains cavitation mechanisms during impact and tensile testing. The processing/reprocessing of the materials will consist in single/multiple extrusion procedures by means of a mini-extruder, respectively. The degradation mechanisms of the materials will be investigated by combining SEC, FTIR, NMR, MALDI-TOF and DSC. The deformation mechanisms will be investigated by DMA, impact testing and instrumented tensile testing. The structural transformations will be investigated by SAXS/WAXS, TEM, AFM, SEM and Light Scattering. The discovered fundamental knowledge will be the basis of the pre-industrialization study of PLA recycling. This last part will consist in i) studying the scale-up of our recycling procedure from the mini-extruder to a targeted industrial extruder, ii) performing the Life Cycle Assessment of PLA recycling, iii) conducting workshops with professional of plastics processing and recycling to build an industrial project, and iii) informing Luxembourgish population about bioplastics and their recycling. This project of valorisation of end-used materials is in line with the knowledge triangle wished by the Luxembourg policy (PNR 2011), aiming at reinforcing the collaboration between Research, Education and Innovation. Indeed, novel fundamental knowledge about bioplastics degradation and mechanics will be obtained and disseminated through publications in high-impact journals and participations to international conferences. Concerning Education, one PhD student and three Master students will be engaged to this research project. Some exhibitions in school will be done and some articles in local press will be published to educate society about bioplastics and their recycling. Innovation will be also addressed by the development of new products (the recycled PLA grades), coupled with their pre-industrialization study. Researchers from the CRP Henri Tudor (Lu), University of Lorraine (F) and University of Mons (B) will participate to this project at the core of the Greater Region.

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