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

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.

Improving the Wet-Spinning and Drawing Processes of Poly(lactide)/Poly(ethylene furanoate) and Polylactide/Poly(dodecamethylene furanoate) Fiber Blends

“…The fiber blends do not show any peak related to the presence of PEF or PDoF, which is due to their limited weight fraction in the blends. Moreover, no red or blue shifts are highlighted when comparing the blends’ spectra with those of the neat−PEF and neat−PDoF, thus highlighting no relevant interactions between the polymer phases in the blends, which is similar to our previous findings [ 22 , 24 , 32 ].…”

“…Neat PLA, PLA/PEF, and PLA/PDoF mixtures were dissolved in a mixture of chloroform and HFIP. The ability of chloroform to dissolve both PLA and furan−based polyesters with long alkyl chains (e.g., PDoF) was previously reported [ 22 , 24 , 32 , 34 ], while HFIP was necessary to provide the dissolution of PEF [ 36 ]. The wet−spinning process was used to produce neat PLA fibers, PLA/PEF, and PLA/PDoF fiber blends with PEF and PDoF concentrations equal to 2.5 wt %, 5 wt %, and 10 wt %.…”

“…Thus, these temperatures enable improving the deformability of the fibers, also avoiding the melting of the PDoF constituent. The drawing procedure was carried out by following the optimized parameters reported in previous work [ 32 ], i.e., by keeping the samples at 80 °C for 10 min to stabilize the temperature and then drawing them at three different draw ratios (1, 2, and 4), corresponding to once, twice, and four times the initial fiber length, at a speed of 50 mm/min. The fibers with a draw ratio of 1 were kept at 80 °C for 15 min, allowing all prepared specimens to be subjected to the same thermal treatment.…”

“…In fact, PLA has been already used in the production of sportswear, furnishings, drapes, and non−wovens, although further improvements in the moisture resistance and mechanical properties are required [ 31 ]. In previous works of our group, PAFs have already been blended with PLA to produce wet−spun fibers, which showed promising improvements in the mechanical properties, thermal stability, and water absorption tendency [ 22 , 24 , 32 ]. Those works demonstrated that PLA/PAF blends with a small fraction of PAFs (max.…”

Improving the Thermomechanical Properties of Poly(lactic acid) via Reduced Graphene Oxide and Bioderived Poly(decamethylene 2,5-furandicarboxylate)

“…Figure 2a-e shows the SEM micrographs of the cryofracture surface of the samples PLA-rGO10 and PLA-PDeF10-rGOx (x = 0.25-2 phr). As already observed for other PLA/PAF blends [26,27,[38][39][40], in this case the blend is also immiscible (Figure 2a), and PDeF forms smooth spheroidal domains with a poor interfacial adhesion with PLA and an average size of 1.9 ± 0.3 µm. The addition of rGO considerably modifies the appearance of the fracture surface.…”