Effects of chain extender and uniaxial stretching on the properties of PLA/PPC/mica composites

Effect of Poly(propylene carbonate) on Properties of Polylactic Acid-Based Composite Films

To enrich the properties of polylactic acid (PLA)-based composite films and improve the base degradability, in this study, a certain amount of poly(propylene carbonate) (PPC) was added to PLA-based composite films, and PLA/PPC-based composite films were prepared by melt blending and hot-press molding. The effects of the introduction of PPC on the composite films were analyzed through in-depth studies on mechanical properties, water vapor and oxygen transmission rates, thermal analysis, compost degradability, and bacterial inhibition properties of the composite films. When the introduction ratio coefficient of PPC was 30%, the tensile strength of the composite film increased by 19.68%, the water vapor transmission coefficient decreased by 14.43%, and the oxygen transmission coefficient decreased by 18.31% compared to that of the composite film without PPC, the cold crystallization temperature of the composite film increased gradually from 96.9 °C to 104.8 °C, and PPC improved the crystallization ability of composite film. The degradation rate of the composite film with PPC increased significantly compared to the previous one, and the degradation rate increased with the increase in the PPC content. The degradation rate was 49.85% and 46.22% faster on average than that of the composite film without PPC when the degradation was carried out over 40 and 80 days; the composite film had certain inhibition, and the maximum diameter of the inhibition circle was 2.42 cm. This study provides a strategy for the development of PLA-based biodegradable laminates, which can promote the application of PLA-based laminates in food packaging.

Fabrication and characterization of transparent nanocomposite films based on poly (lactic acid)/polyethylene glycol reinforced with nano glass flake

Developing new biodegradable packaging with superior properties and advanced functionalities is one of the most emerging research areas of interest in food packaging. In this study, PLA/PEG-based nanocomposite films incorporated with different amounts of nano glass flake (NGF) (0, 0.5, 1, and 2 phr) were fabricated via casting solution for applications in food packaging. The ATR-FTIR displayed no chemical interaction between the PLA/PEG-based matrix and NGF particles. The scanning electron microscopy (SEM) observations exhibited a relatively smooth and homogeneous surface without defects. Incorporation of the NGF into the PLA/PEG-based matrix did not affect the color and opacity of the fabricated films. The prepared nanocomposite films were highly transparent and exhibited superior properties such as increased hydrophobicity, appreciable oxygen barrier properties, and enhanced thermal stability. Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) analysis confirmed the existence of a single glass-transition temperature (Tg) as evidence of miscibility. According to the research results, the PLA/PEG/NGF1 nanocomposite film significantly offered the best overall performance. This work has developed new insight into the potential application of nano glass flakes in food packaging.

Upcycling of post-industrial starch-based thermoplastics and their talc-filled sustainable biocomposites for single-use plastic alternative

This study utilized post-industrial wheat starch (biological macromolecule) for the development of poly(butylene adipate-co-terephthalate) (PBAT) based thermoplastic starch blend (TPS) and biocomposite films. PBAT (70 wt%) was blended with plasticized post-industrial wheat starch (PPWS) (30 wt%) and reinforced with talc master batch (MB) (25 wt%) using a two-step process, consisting of compounding the blend for pellet preparation, followed by the cast film extrusion at 160 °C. The effect of the chain extender was analyzed at compounding temperatures of 160 and 180 °C for talc-based composites. The incorporation of talc MB has increased the thermal stability of the biocomposites due to the nucleating effect of talc. Moreover, tensile strength and Young's modulus increased by about 5 and 517 %, respectively as compared with the TPS blend film without talc MB. Thermal, rheological, and morphological analyses confirmed that the use of talc in the presence of chain extender at a processing temperature of 160 °C has resulted in an enhanced dispersion of talc and chain entanglement with PBAT and PPWS than PBAT/PPWS blend and PBAT/PPWS/Talc composite films. On the other hand, at 180 °C, the talc-containing biocomposite with chain extender tended to form PPWS agglomerates, thereby weakening its material properties.

The Effect of Epoxidized Soybean Oil on the Physical and Mechanical Properties of PLA/PBAT/PPC Blends by the Reactive Compatibilization

Poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT)/poly (propylene carbonate) (PPC) multi-phase blends were prepared by melt processing technique under the presence of compatibilizer with various composition. The effect on the physical and the mechanical property with/without ESO was characterized with spectrophotometric analysis, mechanical properties, thermal properties, rheological properties and barrier properties, and the structure-properties relationship was assessed. ​​The functional groups of PPC were found to effective to improve an interaction with carboxyl/hydroxyl group of PLA/PBAT binary blends to enhance the mechanical and physical properties on multi-phase blend system. The presence of PPC in PLA/PBAT blend affected the reduction of voids on the interface phase resulting in enhancing the oxygen barrier properties. With addition of ESO, the compatibility of ternary blend was found to be enhanced since the epoxy group of ESO reacted with the carboxyl/hydroxyl group of PLA, PBAT, and PPC, and under the condition with critical content of 4 phr of ESO, the elongation behavior dramatically increased as compared to that of blends without ESO while affecting reduction of oxygen barrier properties. The effect of ESO as a compatibilizer was clearly observed from the overall performances of ternary blends, and the potential feasibility of the PLA/PBAT/PPC ternary blends as packaging materials was confirmed at this study.

Recent progress of preparation of branched poly(lactic acid) and its application in the modification of polylactic acid materials

Poly (lactic acid) (PLA) with branched structure has abundant terminal groups, high melt strength, good rheological properties, and excellent processability; it is a new research and application direction of PLA materials. This study mainly summarizes the molecular structure design, preparation methods, basic properties of branched PLA, and its application in modified PLA materials. The structure and properties of branched PLA prepared by ring-opening polymerization of monomer, functional group polycondensation, and chain extender in the processing process were introduced. The research progress of in situ formation of branched PLA by initiators, multifunctional monomers/additives through dynamic vulcanization, and irradiation induction was described. The effect of branched PLA on the structure and properties of linear PLA materials was analyzed. The role of branched PLA in improving the crystallization behavior, phase morphology, foaming properties, and mechanical properties of linear PLA materials was discussed. At the same time, its research progress in biomedicine and tissue engineering was analyzed. Branched PLA has excellent compatibility with PLA, which has important research value in regulating the structure and properties of PLA materials.

Force-Induced Self-Assembly of Supramolecular Modified Mica Nanosheets for Ductile and Heat-Resistant Mica Papers

Mica is a naturally abundant layered silicate mineral that has higher strength than other layered silicate minerals, but its inherent brittleness limits its application in some fields. In this work, mica was ultrasonically exfoliated into a single-layered nanomaterial after thermal activation, acidification, sodium replacement, and cetyltrimethylammonium bromide (CTAB) intercalation and then modified with ureido-pyrimidinone (UPy)-based PEG chains. Vacuum-assisted self-assembly was used to construct supramolecularly modified single-layered mica into bulk materials, in which the mica nanosheets were stacked into mica paper. The reversible quadruple hydrogen-bonded UPy moieties provided a high binding constant and significantly improved the strength and toughness of the obtained mica paper. These force-induced assembled mica papers showed significantly improved tensile strength and toughness compared with pure mica paper and simultaneously maintained the heat resistance of the mica materials, which may be good candidates for the substrates of flexible sensors working at higher temperatures.

Enhanced oxygen barrier properties of poly(lactic acid) via oxygen scavenging strategy combining with uniaxial stretching

Poly(lactic acid) (PLA) films with significantly enhanced mechanical and oxygen barrier properties were obtained via oxygen scavenging strategy combining with uniaxial stretching. In this study, PLA was melt blended with 3 phr of hydroxy-terminated polybutadiene (HTPB) and different contents of acetyl(tributyl citrate) (ATBC) and cobalt neodecanoate. It was then followed by compression molding and uniaxial stretching. After uniaxial stretching, the crystallinity of all films was significantly improved, which contributed to the enhancement in the oxygen barrier performance of composite materials. The morphological analysis carried out using scanning electron microscopy (SEM) revealed that ATBC could obviously promote the dispersion of HTPB in PLA. Overall, the blend films showed a decrease in the oxygen permeability coefficient as compared with the neat PLA film, which reached a similar level to oriented PET film. The optical and mechanical properties of the blend films with ATBC also improved considerably. This work provides a method to prepare high-crystalline polymers with superior gas-barrier properties having great potential for use in high-barrier applications, such as polymers for oxygen-sensitive food packaging.