Plasticization of Polylactide after Solidification: An Effectiveness and Utilization for Correct Interpretation of Thermal Properties

Abstract

Polylactide/triethyl citrate (PLA/TEC) systems were prepared in two ways by introducing TEC to solidified polymer matrix (SS) and by blending in a molten state (MS) to investigate the effectiveness of the plasticization process after solidification of polylactide. The plasticization processes, independent of the way of introducing the TEC into PLA matrix, leads to systems characterized by similar stability, morphology, and properties. Some differences in mechanical properties between MS and SS systems result primarily from the difference in the degree of crystallinity/crystal thickness of the PLA matrix itself. Based on the presented results, it was concluded that the plasticization process after solidification of polylactide is an alternative to the conventional method of modification-blending in a molten state. Then, this new approach to plasticization process was utilized for the interpretation of thermal properties of PLA and PLA/TEC systems. It turned out that double melting peak observed at differential scanning calorimetry (DSC) thermograms does not result from the melting of a double population of crystals with different lamellar thickness, or the melting of both the α′ and α crystalline phase (commonly used explanations in literature), but is associated with the improvement of perfection of crystalline structure of PLA during heating process.

Nanocomposite Materials with Poly(l-lactic Acid) and Transition-Metal Dichalcogenide Nanosheets 2D-TMDCs WS2

“…This discrepancy is likely related to several factors, including the difference in the thermal conductivity of the filler and polymer matrix, the nucleation efficiency (NE) of the filler, its state of dispersion within the matrix, and the potential existence of mechanisms of interfacial crystallization such as epitaxy and transcrystallization [ 29 , 30 , 31 , 32 ]. NE is strongly dependent on the nanofiller morphology, its surface energy, roughness, and crystalline structure as well as on the filler ability to form the critical nucleus [ 16 , 17 , 33 , 34 ]. Furthermore, the dependence of crystallinity (1-λ) c of PLLA and its 2D-WS 2 nanocomposites as a function of cooling rate ( Figure 5 a) closely mirrors the T p trends previously mentioned.…”

Barrier Properties of Semicrystalline Polylactide: The Role of the Density of the Amorphous Regions

“…The long period of PLA/modifier systems was determined by two-dimensional (2D) small-angle X-ray scattering (SAXS) utilizing the equipment and methods described elsewhere. , …”

“…It exhibits a wide application potential in the field of packaging materials because of its high degradability, extraordinary transparency, good mechanical strength, and easy processability. However, PLA has several limitations (brittleness, stiffness, poor ability to plastic deformation, and poor gas barrier properties) and requires significant property improvement to fulfill the specific functional requirements in such applications. − In a previous work, we showed that as a result of introducing triethyl citrate (TEC) into the PLA matrix and its accumulation into the interlamellar/interspherulitic regions, a system with enhanced flexibility and toughness is obtained. In this work, we verified how the modification with the use of various low molecular weight compounds (TEC; glycerol, Gly; and polyethylene glycol, PEG) with clearly different Hildebrand solubility parameters affects the molecular packing efficiency of the amorphous phase of PLA (increase or decrease in the pore size of the free volume) and determine the final transport properties.…”

The Effect of WS2 Nanosheets on the Non-Isothermal Cold- and Melt-Crystallization Kinetics of Poly(l-lactic acid) Nanocomposites

“…The discrepancy is likely related to several factors and none can be ruled out: the difference in the thermal conductivity of the filler and polymer matrix; the nucleation efficiency (NE) of the filler; its state of dispersion within the matrix; and the potential existence of mechanisms of interfacial crystallization such as epitaxy and transcrystallization [ 6 , 7 , 8 , 9 ]. In addition, NE is strongly dependent on the nanofiller morphology, its surface energy, roughness and crystalline structure as well as on the filler’s ability to form the critical nucleus [ 10 , 11 ]. In this regard, Jabbarzadeh has recently reported the crystallization origin in nanocomposite polymers [ 12 ].…”