Statistical Modeling and Optimization of the Drawing Process of Bioderived Polylactide/Poly(dodecylene furanoate) Wet-Spun Fibers.

Daniele Rigotti,Alessandro Pegoretti,Andrea Dorigato,Dimitrios N Bikiaris,Davide Perin,Giulia Fredi

doi:10.3390/polym14030396

Abstract

Drawing is a well-established method to improve the mechanical properties of wet-spun fibers, as it orients the polymer chains, increases the chain density, and homogenizes the microstructure. This work aims to investigate how drawing variables, such as the draw ratio, drawing speed, and temperature affect the elastic modulus (E) and the strain at break (εB) of biobased wet-spun fibers constituted by neat polylactic acid (PLA) and a PLA/poly(dodecamethylene 2,5-furandicarboxylate) (PDoF) (80/20 wt/wt) blend. Drawing experiments were conducted with a design of experiment (DOE) approach following a 24 full factorial design. The results of the quasi-static tensile tests on the drawn fibers, analyzed by the analysis of variance (ANOVA) and modeled through the response surface methodology (RSM), highlight that the presence of PDoF significantly lowers E, which instead is maximized if the temperature and draw ratio are both low. On the other hand, εB is enhanced when the drawing is performed at a high temperature. Finally, a genetic algorithm was implemented to find the optimal combination of drawing parameters that maximize both E and εB. The resulting Pareto curve highlights that the temperature influences the mechanical results only for neat PLA fibers, as the stiffness increases by drawing at lower temperatures, while optimal Pareto points for PLA/PDoF fibers are mainly determined by the draw ratio and the draw rate.

Highlights

Biopolymers, i.e., polymers that are bioderived and/or biodegradable, are a promising alternative to traditional plastics, as they reduce the environmental impact of plastic products across the whole life cycle, from resource extraction to end-of-life management [1]
Our group has recently developed blends of polylactic acid (PLA) and poly(alkylene furanoate)s (PAFs) with different alkyl chain lengths, prepared in the form of films and fibers through solvent casting, spinning, and electrospinning [23,24,25,26,27]. These blends are generally immiscible, the results showed that the addition of 5–10 wt% of any of the considered PAFs to PLA remarkably increases the strain at break and the fracture toughness, especially for cast films
Only the curves as a functioFnorotfhxe1s,txra4inanadt bxr3e,axk4, tahree mpruelstei-ndtiemde, ndsuioentaol trhesepironhsigehsluyrfsaigceniifiscraenptoretfefedctins aEfqteuraemtioenrg(i3n)ganfrdotmheAgNraOphViAcaal nreaplyressisen(Ttaatbiolen 5is).shAonwninicnreFaisgeurine 4t.hIen dthraiswcarsaet,ioonrleydtuhceecsutrhvees strain at break, due to the enhanced macromolecular orientation, to what has been previously reported by La Mantia et al [42] for low-density polyethylene/polyamide 6 incompatible blend films and by Gupta et al [44] for PLA-spun fibers

Summary

Introduction

Biopolymers, i.e., polymers that are bioderived and/or biodegradable, are a promising alternative to traditional plastics, as they reduce the environmental impact of plastic products across the whole life cycle, from resource extraction to end-of-life management [1]. The ever-growing interest in this topic has recently encouraged the development and commercialization of many bioderived, recyclable, and compostable plastics, such as poly(lactic acid) (PLA) [2], polyhydroxyalkanoates (PHAs) [3], thermoplastic starch [4], and poly(butylene succinate) (PBS) [5], which were all employed especially for packaging and other single-use applications. The most common grade of PLA on the market is the isomeric form poly-L-lactic acid (PLLA) containing 2–6 wt% of D-lactic acid units [9]. This PLA grade shows elevated tensile modulus (3–4 GPa) and strength (40–60 MPa), high workability, and good transparency [8,9,10]; it is widely commercialized in the packaging field. The poor toughness, high hygroscopic nature, and high gas permeability of PLA restrict its industrial applications to rigid thermoformed packaging, whereas a wide application of PLA as flexible packaging and textile fibers is still limited [7,12]

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