Study of the Influence of the Reprocessing Cycles on the Final Properties of Polylactide Pieces Obtained by Injection Molding

Abstract

This research work aims to study the influence of the reprocessing cycles on the mechanical, thermal, and thermomechanical properties of polylactide (PLA). To this end, PLA was subjected to as many as six extrusion cycles and the resultant pellets were shaped into pieces by injection molding. Mechanical characterization revealed that the PLA pieces presented relatively similar properties up to the third reprocessing cycle, whereas further cycles induced an intense reduction in ductility and toughness. The effect of the reprocessing cycles was also studied by the changes in the melt fluidity, which showed a significant increase after four reprocessing cycles. An increase in the bio-polyester chain mobility was also attained with the number of the reprocessing cycles that subsequently favored an increase in crystallinity of PLA. A visual inspection indicated that PLA developed certain yellowing and the pieces also became less transparent with the increasing number of reprocessing cycles. Therefore, the obtained results showed that PLA suffers a slight degradation after one or two reprocessing cycles whereas performance impairment becomes more evident above the fourth reprocessing cycle. This finding suggests that the mechanical recycling of PLA for up to three cycles of extrusion and subsequent injection molding is technically feasible.

Tailoring the Properties of Thermo-Compressed Polylactide Films for Food Packaging Applications by Individual and Combined Additions of Lactic Acid Oligomer and Halloysite Nanotubes

“…The thermal stability values extracted from the TGA curves are summarized in Table 4, gathering the temperature required for a loss of weight of 5% (T5%), which is representative for the onset of degradation, the maximum degradation rate temperature (Tdeg), and the amount of residual mass at 600 °C. One can observe that neat PLA thermally degraded in a single step in the range from approximately 330 to 400 • C as previously reported by Agüero et al [43]. In particular, the neat PLA film showed respective T 5% and T deg values of 342.2 and 383 • C. The inset image within Figure 7a shows that the addition of OLA gradually reduced the thermal stability of PLA, being more intensely for the onset of degradation since the T 5% values gradually reduced to 335.3, 313.3, and 292.5 • C for additions of 10, 20, and 30 wt%, respectively.…”

Electrospun Active Biopapers of Food Waste Derived Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Short-Term and Long-Term Antimicrobial Performance

“…∆E * = (∆L * ) 2 + (∆a * ) 2 + (∆b * ) 2 0.5 (3) where ∆L*, ∆a*, and ∆b* corresponded to the differences between the brightness and color parameters of the PHBV biopapers containing the active substances and the values of the neat PHBV biopaper. The color change was evaluated according to the following criteria [63]: the difference was unnoticeable if ∆E* < 1. Only an experienced observer can notice the difference for ∆E* ≥ 1 and < 2.…”

Valorization of Linen Processing By-Products for the Development of Injection-Molded Green Composite Pieces of Polylactide with Improved Performance

“…An axial extensometer, model IB/MFQR2, also from S.A.E. Ibertest, was coupled to the tested samples to improve accuracy [34]. Impact strength was tested in a 6-J Charpy pendulum from Metrotec S.A. (San Sebastián, Spain) following the guidelines of ISO 179.…”