Improving the Thermal and Mechanical Properties of Poly(l-lactide) by Forming Nanocomposites with an in Situ Ring-Opening Intermediate of Poly(l-lactide) and Polyhedral Oligomeric Silsesquioxane

Abstract

In this study, a series of poly(l-lactide) and (3-amino)-propylheptaisobutyl cage silsesquioxane (PLLA-AMPOSS) intermediates were first fabricated using single-arm in situ solution polymerization of LLA monomers and AMPOSS nanoparticles with different contents, 0.02–1.00 mol%. Then, the PLLA-AMPOSS intermediate with 0.5 mol% AMPOSS was selected as a representative and investigated by nuclear magnetic resonance (NMR) and X-ray diffraction (XRD). Afterwards, it was added into the pure PLLA with different mass fractions. Finally, the thermal behavior, crystallization kinetics, morphological characteristics, and mechanical properties of the obtained PLLA/PLLA-AMPOSS nanocomposites were carefully measured and investigated by differential scanning calorimetry (DSC), polarizing microscopy (POM), scanning electron microscopy (SEM), and tensile test. After comparing the PLLA-AMPOSS intermediate and PLLA/AMPOSS blend, the results show that the ring-open polymerization of PLLA-AMPOSS intermediate was successful. The results also show that the existence of PLLA-AMPOSS has a strong influence on the crystallization behavior of PLLA/PLLA-AMPOSS composites, which can be attributed to the heterogeneous nucleation effect of PLLA-AMPOSS. In addition, it was also found from the tensile test results that the addition of the PLLA-AMPOSS nanofiller improved the tensile strength and strain at break of PLLA/PLLA-AMPOSS nanocomposites. All of these results indicate the good nucleating effect of PLLA-AMPOSS and that the AMPOSS disperses well in the PLLA/PLLA-AMPOSS nanocomposites. A conclusion can be drawn that the selective nucleating agent and the combined method of in situ ring-opening polymerization and physical blending are feasible and effective.

Extreme Foaming Modes for SCF-Plasticized Polylactides: Quasi-Adiabatic and Quasi-Isothermal Foam Expansion

“…Over the past two decades, research efforts were focused on experimental studies of the relationship between parameters of polymer plasticization and foaming, and the structural and mechanical characteristics of synthesized or modified materials [23][24][25][26]. The obtained results are invaluable for the improvement of foaming technologies.…”

Temperature and Time Dependence of the Solvent-Induced Crystallization of Poly(l-lactide)

“…However, the crystallization of PLA is rather a slow process compared to many conventional thermoplastics [11]. The polymer crystallization can be done by following different approaches such as physical aging [12], phase separation [13], process-induced crystallization [14], nucleating-agent induced crystallization [15], and/or solvent-induced crystallization [16]. The research about the thermal annealing and solvent-induced crystallization of the PLA has been increasingly paid attention to, not only to improve their mechanical, thermal and other properties, but also to know the interaction of this biopolymer with different media or the humid environment during application.…”

Surface Carbon Shell-Functionalized ZrO2 as Nanofiller in Polymer Gel Electrolyte-Based Dye-Sensitized Solar Cells

“…A facile and effective way to improve the conductivity of PGEs is the introduction of nanomaterials to PGEs, such as inorganic metal oxides or carbonaceous materials, as nanofillers (NFs) [12,13,14,15,16]. With metal oxide NFs, the interaction between the Lewis acidic surfaces of metal oxides and Lewis basic polymers in PGEs reduces polymer self-interaction and thus prevents polymer crystallization; this increases the free volume for ion transport and hence enhances ion conductivity.…”