Polylactide Films Research Articles

ПОЛІЛАКТИДНІ КОМПОЗИЦІЙНІ МАТЕРІАЛИ З ФУНГІБАКТЕРИЦИДНИМИ ВЛАСТИВОСТЯМИ

The regularities of obtaining polylactide film composite materials with simultaneous silver nanoparticles formation were researched. The influence of the nature of polylactide and its structure (amorphous and amorphous-crystalline), of the glycerin plasticizer on the solvent evaporationkinetics was determined. To give polylactide composites fungicidal properties, the silver reduction reaction by the interaction of argentum salts with polyvinylpyrrolidone was applied. A main technological scheme for obtaining films based on polylactide with fungicidal properties is proposed. Above mentioned provides effective practical usage of the films as packaging materials for food products and medicines.

Evaluation of the ageing resistance and lifespan of talc-filled poly(butylene adipate-co-terephthalate)/polylactide (PBAT/PLA) films used for winter potato cultivation

Evaluation of the ageing resistance and lifespan of talc-filled poly(butylene adipate-co-terephthalate)/polylactide (PBAT/PLA) films used for winter potato cultivation

Manufacture of electrospun porous PLA fiber‐type film coated with CMC and its anti‐adhesion efficiency in white mice

AbstractThe electrospun polylactide (PLA) anti‐adhesion fiber‐type film coated with carboxymethylcellulose (CMC) was manufactured and evaluated for its usability through animal experiments. The PLA anti‐adhesion film developed in this study is an adhesion preventive film of a double composite structure with both hydrophobicity and hydrophilicity. This film has the anti‐adhesion effect due to hydrophobic PLA that do not melt easily in the body and at the same time is easily attached to the surgical site by hydrophilic CMC that reacts easily to body fluids and changes quickly to mucus. In this study, the diameter and the pore diameter of the PLA fiber and thickness of PLA film made by electrospinning was 0.2–0.4, 1–10, and 30–50 μm, respectively. Through observation of surface structure (×5000 magnification), the most suitable concentration of CMC to maintain pores on the PLA film as much as possible is 0.5% wt/vol. The CMC content in the PLA film coated with 0.5% wt/vol of CMC was measured to be 5.41% wt/wt and its tensile strength was about 2.92 times higher than that of the noncoated PLA film with CMC. The porosity of CMC‐coated PLA film (5.41% wt/wt) was found to be 76.4%. In the animal experiment, 20 white mice (10 as a control group and 10 as an experimental group) were used to determine the degree of adhesion prevention. As a result of observing adhesion and anti‐adhesion between the cecum and the peritoneum by performing U‐shaped laparotomy on white mice at the third week after surgery, the incidence of adhesion in the control group was 90%, whereas the experimental group was 20%.

Effect of birch tar embedded in polylactide on its biodegradation

The plasticized film was made of polylactide and birch tar, which was used in a concentration of 1, 5 and 10 % by weight. Tar was added to the polymer to obtain materials with antimicrobial properties. The main purpose of this work is to characterize and biodegradation of this film after the end of its use. Therefore, the following analyzes were performed: enzymatic activity of microorganisms in the presence of polylactide (PLA) film containing birch tar (BT), biodegradation process in compost, barrier changes and structural properties of the film before and after biodegradation and bioaugmentation. Biological oxygen demand BOD21, water vapor permeability (Pv), oxygen permeability (Po), scanning electron microscopy (SEM) and enzymatic activity of microorganisms were assessed. Microorganism strains Bacillus toyonensis AK2 and Bacillus albus AK3 were isolated and identified, which constituted an effective consortium increasing the susceptibility of polylactide polymer material with tar to biodegradation in compost. Analyses with the use of the above-mentioned strains had an impact on the change of physicochemical properties, e.g. the presence of biofilm on the surface of the analyzed films and the reduction of the barrier properties of the film, which translates into the recorded susceptibility to biodegradation of these materials. The analyzed films can be used in the packaging industry, and after use, subjected to intentional biodegradation processes, including bioaugmentation.

Transparent, Heat-Resistant, Ductile, and Self-Reinforced Polylactide through Simultaneous Formation of Nanocrystals and an Oriented Amorphous Phase

Imparting polylactide (PLA) films with great heat resistance, transparency, and balanced mechanical performance simultaneous is a big challenge in academia and industry due to mutual exclusiveness of properties. In this work, a newfound strategy that combines elongational stress field and thermal field is proposed to reorganize the crystalline and amorphous structure of PLA films. It is discovered that the oriented PLA films with high draw ratios form a unique structure of the oriented amorphous phase restricted by the oriented nanosized crystal during thermal treatment at an appropriate temperature. Superb stiffness–toughness balance of the film is achieved as the elongation at break increases from 16 to 91.9% after the thermal treatment at 150 °C, while the yield strength increases from 50.0 to 76.0 MPa. It is worth noting that the PLA film also has excellent transparency, i.e., a transmittance as high as 86.6% (550 nm), owing to crystallites formed on the nanometer scale. Excellent heat resistance is also obtained, with the onset decline temperature increasing from 63.7 (for the unstructured casting film) to 77.1 °C due to increased crystallinity. Furthermore, a new understanding of the orientation of the amorphous phase promoted by the confinement effect to the toughening of PLA is obtained, and a phenomenal model for the thermal-treatment-induced toughening effect is proposed. This work could provide a significant guidance for the facile preparation of a PLA film with promising comprehensive properties of toughness–stiffness balance, high transparency, and good heat resistance.

Branched Amphiphilic Polylactides as a Polymer Matrix Component for Biodegradable Implants.

The combination of biocompatibility, biodegradability, and high mechanical strength has provided a steady growth in interest in the synthesis and application of lactic acid-based polyesters for the creation of implants. On the other hand, the hydrophobicity of polylactide limits the possibilities of its use in biomedical fields. The ring-opening polymerization of L-lactide, catalyzed by tin (II) 2-ethylhexanoate in the presence of 2,2-bis(hydroxymethyl)propionic acid, and an ester of polyethylene glycol monomethyl ester and 2,2-bis(hydroxymethyl)propionic acid accompanied by the introduction of a pool of hydrophilic groups, that reduce the contact angle, were considered. The structures of the synthesized amphiphilic branched pegylated copolylactides were characterized by 1H NMR spectroscopy and gel permeation chromatography. The resulting amphiphilic copolylactides, with a narrow MWD (1.14-1.22) and molecular weight of 5000-13,000, were used to prepare interpolymer mixtures with PLLA. Already, with the introduction of 10 wt% branched pegylated copolylactides, PLLA-based films had reduced brittleness, hydrophilicity, with a water contact angle of 71.9-88.5°, and increased water absorption. An additional decrease in the water contact angle, of 66.1°, was achieved by filling the mixed polylactide films with 20 wt% hydroxyapatite, which also led to a moderate decrease in strength and ultimate tensile elongation. At the same time, the PLLA modification did not have a significant effect on the melting point and the glass transition temperature; however, the filling with hydroxyapatite increased the thermal stability.

Aging of Polylactide Films Exposed to Plasma—Hydrophobic Recovery and Selected Application Properties

In this study, the effect of polylactide (PLA) material on the susceptibility to hydrophobic recovery due to storage was examined, the effectiveness of plasma activation of the film, defined as improving the hydrophilicity of the material, was studied, and the selected film properties that are important from an application point of view were investigated. The study was conducted on three films using oxygen and argon plasma. Contact angles of water, diiodomethane, and ethylene glycol were investigated, and the values of surface free energy (SFE) and its polar and dispersive components were determined immediately after activation, as well as after a specified storage time (after 1, 7, 14, 30, and 60 days). The effects of film activation on its roughness, weight loss, tensile strength, color changes, and gloss were also determined. Based on the results, it was concluded that the type of film influences the course of hydrophobic recovery. At the same time, the trend of changes depends on the type of gas used for activation, while the magnitude of changes depends on the film. Moreover, it was observed that the type of PLA film had a significant effect on the changes in the polar and dispersion components of SFE, as well as on roughness and mass loss due to plasma activation. Furthermore, these parameters also depended on the type of gas used for plasma activation.

Structural Features of Polylactide Films Obtained from a Melt and Solution

Structural Features of Polylactide Films Obtained from a Melt and Solution

Study of Argon and Oxygen Mixtures in Low Temperature Plasma for Improving PLA Film Wettability

Oxygen (O2) and argon (Ar) plasma give a significant improvement in the wettability of PLA films. This study investigates the effectiveness of plasma activation with a mixture of these two gases. The study includes contact angle measurements with water and diiodomethane and calculation of surface free energy (SFE) together with its polar and dispersion components. In addition, a chemical analysis of the surface, surface roughness, weight loss and the change in tensile strength were examined. As a result of the study, it was found that the use of a mixture of oxygen and argon during the plasma activation of the polylactide film gives better improvement in wettability than the use of pure gases. Moreover, the use of a mixture of these gases in equal proportions turned out to be the most effective, providing the highest value of the SFE and its polar component, as well as the lowest value of the water contact angle. Furthermore, plasma activation with this gas mixture results in reduced surface etching compared to other gas compositions, which manifests itself in lower weight reduction and an insignificant change in tensile strength.

Investigation of Biodegradation of Polylactide Product Samples under Various Temperature and Soil Conditions

In this work, the biodegradation of polylactide films, granules and tapes at temperatures of 23 °C and 8 °C in humus and chernozem soils was investigated. It was found that under the conditions studied, polylactide products are poorly biodegradable – for 84 days of exposure in the soil, the weight loss of all products did not exceed 10%. According to the results of microbiological assessment of the microflora of soils in which destruction occurred, no destructors of this type of biodegradable polymer were identified by inoculation in nutrient media containing polymer as the only carbon source.

Blowing tough polylactide film enabled by the in situ construction of covalent adaptive networks with epoxidized soybean oil as dynamic crosslinks

PLA covalent adaptive networks with ESO as dynamic crosslinks enhance the melt strength of PLA and enable the tough PLA film by extrusion blowing, opening up a new avenue toward advanced PLA film in response to severe plastic film pollution.

Composites Based on Polylactide Doped with Amorphous Europium(III) Complex as Perspective Thermosensitive Luminescent Materials

This work reports fabrication of polylactide (PLA) films doped with various additives of an amorphous Eu(III) complex. We study the temperature behavior of the luminescence intensity and lifetime of the PLA-Eu(III) composites in the range of 298–353 K and investigate the mechanism of luminescence temperature quenching. The peak relative sensitivity of the films reaches 20.1 %×K−1 and exceeds the respective characteristics of all known lanthanide-containing thermosensors designed for the range of physiological temperatures. The produced films can be potential novel materials for luminescent thermosensors.

Effective and Easy Techniques of Collagen Deposition onto Polylactide Films: DC-Discharge Plasma Treatment vs. Chemical Entrapment.

Enhancement of cell adhesion and growth on surface of the biodegradable materials is one of the important tasks in development of materials for regenerative medicine. This work focuses on comparison of various methods of collagen coating deposition onto polylactide films, aiming to increase their biocompatibility with human mesenchymal stromal cells. The collagen deposition was realized using either preliminary plasma treatment of the polylactide films or pre-swelling in solvent mixture. These techniques were compared in terms of the effect on the surface's chemical structure, morphology, hydrophilicity and ability to support adhesion and growth of human mesenchymal stromal cells.

Birch Tar Introduced into Polylactide and Its Influence on the Barrier, Thermal, Functional and Biological Properties of the Film Obtained by Industrial Extrusion

The aim of the study was to evaluate possibility of producing a polylactide film with birch tar by the industrial extrusion method and whether the addition of 10% birch tar can ensure adequate biocidal properties of PLA against pathogenic microorganisms (E. coli, S. aureus, P. aeruginosa, A. tumefaciens, X. campestris, P. brassicacearum, P. corrugate and P. syringae) and fungi (A. niger, A. flavus and A. versicolor) while ensuring beneficial functional properties, such as water vapor, nitrogen, oxygen and carbon dioxide permeability, which are of considerable importance in the packaging industry. The main test methods used were ISO 22196, ISO 846, ISO 2556, ASTM F 1927 and ASTM F 2476-20. The obtained results prove the possibility of extruding polymer films with a biocidal additive, i.e., birch tar, and obtaining favorable properties that qualify the produced film for applications in the packaging industry.

Light weight, low dielectric constant, super-robust polylactide film based on stress-induced cavitation aided by crystallization

Exploiting pollution-free and highly efficient pore-forming method for low dielectric constant biodegradable materials remains a challenge in green electronics field. As biodegradable polylactide (PLA) exhibits good electric insulation, herein a facile “casting-thermal stretching” approach via stress-induced cavitation aided by crystallization is reported to obtain porous PLA films. The extensional stress and optical purity have vital influence on determining the hierarchical structures (oriented crystallites and porous structure). Hence the PLA with the highest optical purity (>99%) has the best comprehensive properties: When the DR reaches 6.6 (PLA99–6.6), the PLA99–6.6 film exhibits light weight (0.99 g/cm3), low dielectric constant (2.48 at 1 kHz), low dielectric loss (4.6 × 10−3 at 1 kHz), super robustness (tensile strength of 185.9 MPa, Young's modulus of 4.5 GPa and tensile strain of 12.4%) and excellent durability under high temperature and humidity condition, which have great potential application in green electronics.

Preparation, Characterization and Evaluation of Antibacterial Properties of Polylactide-Polyethylene Glycol-Chitosan Active Composite Films.

Chitin is a natural biopolymer obtained from the exoskeleton of crustaceans. Chitosan is a derivative of chitin, which has antimicrobial properties and potential applications in several industries. Moreover, the composites of chitosan with other biodegradable polymers, such as polylactide (PLA) as packaging film, have shown promising results. In this study, chitosan was obtained and characterized from shrimp shells. Then, polylactide-chitosan composite films were prepared by a solvent casting technique using various amounts of chitosan (0.5–2% w/w) and polyethylene glycol as plasticizer (10% w/w). Thermal, mechanical properties, Fourier-transform infrared, scanning electron microscopy, as well as antibacterial properties of composite films were determined. It was found that adding chitosan (CH) into PLA films has a significant effect on tensile strength and no effect on thermal properties. The results showed a reduction on average of 1 log of colony-forming units against Staphylococcus aureus, while there is no antibacterial effect against Salmonella typhimurium. The study proved the antibacterial effect of CH in films of PLA against Gram-positive bacteria and appropriate mechanical properties. These films could be used for the development of biodegradable/eco-friendly food packaging prototypes, as a potential solution to replace conventional non-degradable packaging materials.

The Peculiarities of Electret Effect in Corona Electrets Based on Nonpolar and Polar Polymers With Dispersed Montmorillonite

Polyethylene (PE) and polylactide (PLA) films with 2 and 4 vol% of montmorillonite (MM) are compared to each other and to nonfilled samples. The electret characteristics of initial and composite films (values of the surface potential, effective surface charge density, and electric field strengths) are determined. Filling PE and PLA with MM improves electret properties due to changes in heterogeneous structure.

Tailoring Oligomeric Plasticizers for Polylactide through Structural Control.

Structural variations (oligolactide segments, functionalized end groups, and different plasticizer cores) were utilized to tailor the performances of biobased plasticizers for polylactide (PLA). Six plasticizers were developed starting from 1,4-butanediol and isosorbide as cores: two monomeric (1,4-butanediol levulinate and isosorbide levulinate) and four oligomeric plasticizers with hydroxyl or levulinate ester end groups (1,4-butanediol-based oligolactide, isosorbide-based oligolactide, 1,4-butanediol-based oligomeric levulinate, and isosorbide-based oligomeric levulinate). Structural variations in plasticizer design were reflected in the thermal stability, plasticizing efficiency, and migration resistance. The monomeric plasticizer 1,4-butanediol levulinate decreased the glass-transition temperature of PLA from 59 to 16 °C and increased the strain at break substantially from 6 to 227% with 20 wt % addition. 1,4-Butanediol-based oligomeric levulinate exhibited better thermal stability and migration resistance, though the plasticizing efficiency was slightly lower (glass-transition temperature = 28 °C; strain at break = 202%). Compared to PLA films plasticized by plasticizers with flexible butanediol cores, those plasticized by plasticizers with rigid isosorbide cores exhibited higher Young’s modulus and thermal stability and lower plasticizing efficiency. Furthermore, plasticizers with levulinate ester end groups had improved thermal stability, plasticizing efficiency, and migration resistance compared to the corresponding plasticizers with hydroxyl end groups. Hence, a set of controlled structural variations in plasticizer design were successfully demonstrated as a potent route to tailor the plasticizer performances.

Influence of sericin‐g‐PLA as an organic nucleating agent for preparing biodegradable blend films

AbstractHere for the first time, this work indicated that the sericin‐g‐polylactide (SS‐g‐PLA) copolymer can be potentially used as an organic nucleating agent to improve the crystallinity and biodegradability of polylactide (PLA). The properties of blended films containing SS‐g‐PLA mixed with virgin PLA polymer were highly evaluated. The water vapor permeability (WVP), thermal behavior, dynamic mechanical properties, crystal structure, and biodegradability of the PLA/SS‐g‐PLA‐blended films were characterized and compared with a commercial PLA film. The results clearly indicated that the incorporation of SS‐g‐PLA copolymer in the PLA matrix had a significant effect on the properties of PLA/SS‐g‐PLA‐blended films. The WVP values of PLA/SS‐g‐PLA‐blended films were lower than that of commercial PLA film by about 2–3 g·mm/m2·day·atm, and their thermal behaviors (e.g. Tg, Tcc, and Tm) were also decreased. Adding SS‐g‐PLA can increase the crystallinity of PLA. The degree of crystallinity (%χc) of the series of PLA/SS‐g‐PLA‐blended films was increased to about 2–4 times that of the commercial PLA film (3%). Interestingly, biodegradation results revealed that the percent of biodegradability of PLA/SS‐g‐PLA‐blended film was 80% in 43 days under a compost environmental temperature of 58 ± 2°C. This evidence indicated that the SS‐g‐PLA copolymer can improve the biodegradability of PLA.

High-pressuretreatment of water-filled co-extruded polylactide films: Effect on microstructure, barrier, thermal, and rheological properties.

The impact of high-pressure treatments (450 and 600MPa) on the morphological, thermal, structural, and barrier properties of commercial coextruded polylactide (PLA) packaging films has been explored to evaluate their applicability in food processing. Pouches filled with water as a food simulant were subjected to high-pressure treatment for 15min at ambient temperature. Results indicated no significant changes in the visual appearance, color, integrity, or water barrier properties of the post-process pouches. However, high-pressure treatment affected mechanical property results. Thermal analysis of the film showed endothermic double melting peaks (165.12 and 170.55°C), which did not change with the pressurization; however, the exothermic crystallization peak (118.08°C) varied significantly. Both SEM and AFM micrographs demonstrated that the surface morphology and roughness parameters (arithmetic mean [Sa ] and root mean square height [Sq ]) of the films were significantly affected by the HP treatment, which is further complemented by the FTIR spectra and XRD diffractogram. Melt rheology (175-205°C) of the pressure-treated films showed a significant drop (20-30%) in mechanical rigidity (G') when compared to the untreated sample. Changes in the microstructure/crystallinity in the PLA films were indicated by van Gurp and Palmen plot. PRACTICAL APPLICATION: The results reported here can help to improve the design of the coextruded packaging materials so that it can be successfully implemented to high-pressure processing and high pressure-assisted thermal processing of food.