Enhancement of crystallinity and toughness of poly (l‐lactic acid) influenced by Ag nanoparticles processed by twin screw extruder

Abstract

Poly(l‐lactic acid) nanocomposites based on silver nanoparticles (PLA/AgNP) were prepared by melt blending using a twin screw extruder. Nanocomposites at low concentrations were prepared with 0.1, 0.2, and 0.3 wt% of AgNP to enhance the crystallinity and improve the thermal and mechanical properties of PLA. AgNPs smaller than 100 nm which increased the crystallinity of PLA upon the addition were detected by UV–Vis. Crystallinty index of nanocomposites was estimated reaching a maximum of 0.52, where the AgNPs acted as heterogeneous nucleating agent which is correlated with the Ag content. The α and α′ crystals were observed by temperature modulated differential scanning calorimetry and wide angle X‐ray diffraction, thus lattice spacing of more ordered and distorted crystals were corroborated obtaining a higher fraction of α structures when a high content of nanoparticles was added. Moreover, strain at break and toughness of pure PLA were increased from 4.3% to 16.9% and 2.1 to 7.3 MJ/m3, respectively, modifying the inherent brittleness of PLA. Finally, with the obtained results a correlation was established where more disordered crystals show less resistance to deformation that lead to an enhancement of elongation at break observed in the nanocomposites. POLYM. COMPOS., 39:2368–2376, 2018. © 2016 Society of Plastics Engineers

Multifunctional PLA Blends Containing Chitosan Mediated Silver Nanoparticles: Thermal, Mechanical, Antibacterial, and Degradation Properties

“…Neat PLA/OLA showed low elongation at break, (ε), (neat PLA/OLA ε ~108%; AgCH-NPs nanocomposites ε ~338-371%) and high Youngs´ or elastic modulus, (E), (neat PLA/OLA E = 783 MPa; AgCH-NPs nanocomposites E ~88-256 MPa) compared to nanocomposites. All the nanocomposites possessed higher elongation at break while a reduction in the elastic modulus and maximum tensile strength (σmax) was observed similarly as previously reported in other studies [41]. Interestingly, the best balance of mechanical behavior into the nanocomposites was obtained for the least amount of AgCH-NPs tested (0.5 wt%) having the highest Youngs´ modulus and maximum tensile strength of the whole nanocomposites while retaining similar elongation at break.…”

“…This fact can be indicative of a higher degree of order in the structure with increasing the AgCH-NPs content to 5 wt% from more distorted orthorhombic crystals (α form) to more perfect crystals (α form). Calculated interplanar distance from Braggs´law evidenced lower distance between planes in the sample with the highest AgCH-NPs content (Table 2) [41]. It is also possible to note that small diffraction peaks at 12.6 • and 25.3 • appeared in 1, 3, and 5 wt% of AgCH-NPs containing samples that are assigned to the reflections of (004/103) and (016) planes of crystalline PLA respectively [42,43].…”

High-Performance Polylactic Acid Materials Enabled by TiO2–Polydopamine Hybrid Nanoparticles

“…Due to the compatibility between PLA and TiO 2 –PDA, the PLA nanocomposite shows high performance with addition of only 0.2 wt % TiO 2 –PDA nanoparticles. Such a phenomena that a few nanoparticles added or changed can obtain obvious performance varies were also found in some previous studies. − …”

Incorporation of Metal-Based Nanoadditives into the PLA Matrix: Effect of Surface Properties on Antibacterial Activity and Mechanical Performance of PLA Nanoadditive Films

“…In general, packaging novelty concepts have focused not only on biodegradability but also on multifunctionality, in addition to the creation of bio-based and/or biodegradable plastics using biopolymers such as poly(lactic acid) PLA. In particular, surface coating strategies or the integration of nanoparticles (NPs) additives into polymer matrices are used [ 5 , 6 , 7 , 8 , 9 ]. Similar to bulk additives, NPs additives are incorporated into the polymer matrix, but on the other hand, the aspect ratio of largest to smallest dimension provides increased reinforcement effect in the preparation of nanocomposites-based PLA.…”