Techniques to Improve Crystallization in Polylactic Acid Packaging

A biodegradable packaging material with improved durability and barrier properties, comprising a paper substrate coated with a composition of polyhydroxyalkanoate (PHA) and two or more types of polylactic acid (PLA) with different melting indices. The PHA provides thermal stability and the PLA enhances barrier properties, while the combination of both enables the material to meet both industrial and household composting standards.

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A biodegradable composite comprising a biodegradable polymer and bio-crystals, wherein the bio-crystals are in a concentration of between 1 wt % to 50 wt % of the biodegradable polymer. The composite exhibits improved mechanical properties compared to the polymer alone, including enhanced tensile stress, modulus, and toughness. The bio-crystals can be amino acids, such as L-tyrosine, and are dispersed homogeneously within the polymer matrix. The composite is suitable for various applications, including packaging materials, films, foams, hydrogels, and aerogels.

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Film comprising a poly(3-hydroxyalkanoate) resin and a polylactic acid-based resin, where the polylactic acid-based resin has a melting point peak below 170°C. The film is produced by blending the poly(3-hydroxyalkanoate) and polylactic acid-based resins in a specific ratio, with the polylactic acid-based resin exhibiting a melting point below 170°C. The film can be stretched to achieve high strength and resistance to deformation without compromising its integrity.

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Biodegradable container made from a biodegradable resin composition that uses a specific type of biodegradable polymer called polyhydroxyalkanoate (PHA) with a high content of 4-hydroxybutyrate (4-HB) units. The composition has a melt flow index of 1.0 g/10 minutes or more when measured at 165°C. The container made from this composition has improved properties like impact resistance, chemical resistance, and water resistance compared to other biodegradable containers. It also has a compressive strength of 5 kgf/cm2 or more. The biodegradable container can be prepared by molding the biodegradable resin composition.

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A biodegradable resin with enhanced flexibility, comprising a poly(lactic acid-b-3-hydroxypropionic acid) block co-polymer with a crystalline layer thickness of 1.0 nm to 14.0 nm, a molecular weight of 50,000 g/mol to 500,000 g/mol, and a composition of 10% to 30% poly(3-hydroxypropionic acid) and 70% to 90% polylactic acid. The resin exhibits a Young's modulus of 0.1 GPa to 5.0 GPa and can be used in various molded articles, including packaging materials.

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Biodegradable resin composition comprising a blend of polylactic acid (PLA) and polyhydroxyalkanoate (PHA) resins, wherein the PHA resin comprises a combination of 3-hydroxyhexanoate (3HH) and 4-hydroxybutyrate (4HB) repeating units, enabling the production of biodegradable films with improved mechanical properties, stretchability, and biodegradability.

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A biodegradable foam sheet with enhanced thermal resistance, insulation, and strength, comprising a polylactic acid (PLA) resin composition with a high D- or L-lactic acid content (98 mol% or greater) and a mean volume diameter of sheet silicate grains (10-200 μm). The PLA resin composition has a high melt viscosity, achieved through reactive extrusion with a chain extender, and is processed at a temperature range of 200-240°C. The foam sheet exhibits excellent thermoformability and can be used to produce molded products with improved thermal resistance.

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A biodegradable foam sheet made from a polylactic acid (PLA) resin composition that exhibits excellent moldability, biodegradability, strength, thermal insulation properties, and thermal resistance. The PLA resin composition comprises a high-optical-purity PLA resin with a weight-average molecular weight of 180,000 to 320,000 and a terminal hydroxyl group content of 0.3 to 1.4. The composition also includes an epoxy group-containing compound with an epoxy equivalent of 170 to 350. The foam sheet has a cold crystallization enthalpy of 20 J/g or greater and a recrystallization enthalpy of 20 J/g or greater.

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Polylactic acid (PLA) has inherent drawbacks, such as its amorphous structure, which affect its mechanical and barrier properties. The use of nanofibrillated cellulose (NFC) mixed with PLA for the production of composites has been chosen as a solution to the above problems. A PLA/NFC composite was produced by solution casting. Before use, the cellulose was modified using a silane coupling agent. The composite films were investigated via X-ray diffraction, as well as by mechanical, physical, thermal analyses and by differential scanning calorimeter. The crystallinity was four times that of pure PLA and the water vapor transmission rate decreased by 76.9% with the incorporation of 10 wt% of NFC. The tensile strength of PLA/NFC blend films increased by 98.8% with the incorporation of 5 wt% of NFC. The study demonstrates that the addition of NFC improved the properties of PLA. This provides a solid foundation for the enhancement of the performance of PLA products.

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A biodegradable foam sheet for food containers that combines high thermal resistance, insulation, and anti-staining properties. The foam sheet is made from a polylactic acid (PLA) composition with a crystallinity of 40-60% and a melt viscosity of 100-500 Pa·s. The PLA composition contains a chain extender with two or more epoxy groups per molecule and has a bulk density of 0.063-0.250 g/cm3. The foam sheet is produced using a high-temperature extrusion process and has a surface roughness of 0.5-2.0 μm.

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A polylactide resin composition with improved crystallinity, comprising a polylactide resin, a first nucleating agent, and a second nucleating agent, wherein the composition is heat-treated at 25-120°C for 1-30 minutes to enhance crystallization. The first nucleating agent is a bio-based organic compound, such as uracil or orotic acid, while the second nucleating agent is a conventional inorganic compound, such as talc or mica. The heat treatment step enables the synergistic effect of the two nucleating agents to achieve higher crystallinity and improved thermal properties.

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A biodegradable plastic composition with improved processability and mechanical properties, comprising a blend of polylactic acid (PLA) and suberin or suberin-based compounds extracted from plant sources, such as cork and potato periderm. The composition exhibits enhanced plasticity and biodegradability compared to conventional PLA-based bioplastics, making it suitable for various applications including disposable products, packaging, and agricultural materials.

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Polylactic acid (PLA) is a biobased, biodegradable, non-toxic polymer widely considered for replacing traditional petroleum-based polymer materials. Being a semi-crystalline material, PLA has great potential in many fields, such as medical implants, drug delivery systems, etc. However, the slow crystallization rate of PLA limited the application and efficient fabrication of highly crystallized PLA products. This review paper investigated and summarized the influence of formulation, compounding, and processing on PLA's crystallization behaviors and mechanical performances. The paper reviewed the literature from different studies regarding the impact of these factors on critical crystallization parameters, such as the degree of crystallinity, crystallization rate, crystalline morphology, and mechanical properties, such as tensile strength, modulus, elongation, and impact resistance. Understanding the impact of the factors on crystallization and mechanical properties is critical for PLA processing technology innovations to meet the requirements of various applications of PLA.

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Polylactide (PLA) resin composition with improved crystallinity and reduced glass transition temperature, achieved by combining a first nucleating agent that enhances high molecular weight chain mobility and a second nucleating agent that lowers the glass transition temperature of the amorphous region.

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The toughening modification of polylactic acid (PLA), one of the most promising sustainable plastics, usually comes at the expense of other characteristic properties, such as mechanical strength, transparency, and environmental friendliness. In this work, a polyurethane copolymer elastomer (PCLA-PLA-U) containing three different blocks, i.e., PLA, copolymer synthesized from random copolymerization of -caprolactone and lactide (PCLA), and polyurethane (PU), with different functions has been designed and synthesized. The elastomer's compatibility with the matrix is enhanced by the addition of PLA blocks, therefore effectively regulating the size and dispersion of the toughening phases. PCLA blocks, as the main components, endow the PU copolymer with good transparency and a refractive index matching with PLA matrix. Meanwhile, the physical cross-linked network constructed based on PU blocks endows the toughening phase with an excellent ability to induce matrix elastic deformation, thereby significantly improving the toughness of PLA. When the addition of PCLA-PLA-U is low (<5%), the mo... Read More

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A polylactic acid (PLA) resin composition for producing biodegradable foamed PLA products, comprising a PLA resin with a melt viscosity of 2,000 to 40,000 Pa·s at 190°C and a molecular weight distribution with a region of Mw ≤ 1,000 of ≤ 10% and a region of Mw ≥ 500,000 of ≥ 20%. The composition enables the production of foamed PLA products with improved mechanical properties, thermal stability, and biodegradability.

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A biodegradable foamed polylactic acid (PLA) sheet with improved properties for packaging and cushioning applications. The sheet is manufactured through a novel process involving melting, kneading, and expansion of PLA resin in the presence of a compressive fluid, followed by purging and expansion. The resulting sheet exhibits a low bulk density, controlled melt viscosity, and reduced crystallinity, enabling enhanced flexibility, cushioning performance, and wrapping followability. The sheet can be used as a raw material for various molded products, offering a sustainable alternative to traditional packaging materials.

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Blends of polylactic acid (PLA) with amorphous polyhydroxyalkanoate (aPHA) are less brittle than neat PLA, thus enabling their use as biodegradable packaging. This work investigated the impact of recycling on the properties of neat PLA and PLA/aPHA blends with 90 and 75 wt. % PLA. After the materials were subjected to five heat histories in a single-screw extruder, the mechanical, rheological, and thermal properties were measured. All recycled compounds with 100% PLA and 75% PLA had similar decomposition behavior, whereas the decomposition temperatures for the blends with 90% PLA decreased with each additional heat cycle. The glass transition and melting temperatures were not impacted by reprocessing, but the crystallinity increased with more heat cycles. The complex viscosity of the reprocessed PLA and PLA/aPHA blends was much lower than for the neat PLA and increasing the number of heat cycles produced smaller reductions in the complex viscosity of 100% PLA and the blend with 90% PLA; no change in complex viscosity was observed for blends with 75% PLA exposed to 2 to 5 heat cycles.... Read More

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Polylactide (PLA) resin composition with improved crystallinity, comprising a first nucleating agent and a second nucleating agent, wherein the second nucleating agent is a bio-based organic compound having a molecular weight of 1000-5000 Da, and the first nucleating agent is selected from the group consisting of uracil, OA1, and OA3. The composition exhibits enhanced crystallization rate and crystallinity degree compared to conventional PLA resins.

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A method for preparing polylactic acid (PLA) polymer with high molecular weight and excellent color characteristics through ring-opening polymerization of lactide using a combination of specific catalysts. The method employs a tin-based catalyst and a phosphinite-based cocatalyst to achieve high molecular weight PLA with improved color stability, overcoming limitations of conventional methods that compromise molecular weight for color quality.

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