Polylactide Films Research Articles

Enhanced Performance of Polylactide Film via Simultaneous Biaxial Stretching and Silane Coupling Agent as a Thermal Shrinkable Film

Biaxial stretching technique has been known to improve the toughness of polylactide (PLA) film. Furthermore, blending with an additive is another way to control the mechanical properties of the product. The integrated effect of simultaneous biaxial stretching and blending with silane coupling agent on the properties of PLA film is examined in this study. The PLA pellets are melt compounded with various amounts of 3-aminopropyltriethoxy silane (APS). Then, the films are prepared by cast film extrusion and simultaneous biaxial stretching process with a stretching speed of 75 mm s–1. The relationships among the crystallinity, tensile properties, and thermal shrinkage of the prepared films are investigated. The crystallinity of PLA is significantly induced in the film by the stretching technique. An increase in the additive content also facilitates the polymeric crystallinity. The elongation at the break of the biaxially stretched film increases with the additive content, which corresponds with the PLA crystallinity. Compared to the pristine PLA film, the addition of 1% APS improves tensile strength in a transverse direction of the film about 10 times. The thermal shrinkage of the obtained films was evaluated to assess their applications as heat-shrinkable films. The prepared films show a thermal shrinkage of 45%, which are comparable to that of a commercial shrink film.

Synergistic effects of a novel multi-branched polylactide ionomer on polylactide film

Synergistic effects of a novel multi-branched polylactide ionomer on polylactide film

Quality and Shelf-Life Stability of Pork Meat Fillets Packaged in Multilayer Polylactide Films.

In the present study, the effectiveness of a multilayer film of polylactide (PLA), fully bio-based and compostable, was ascertained to develop a novel sustainable packaging solution for the preservation of fresh pork meat. To this end, the multilayer PLA films were first characterized in terms of their thermal characteristics, structure, mechanical performance, permeance to water and aroma vapors and oxygen, and optical properties and, for the first time, compared with two commercial high-barrier multilayer packaging films. Thereafter, the multilayers were thermosealed to package fillets of fresh pork meat and the physicochemical changes, lipid oxidation levels, and microbiological counts were monitored in the food samples during storage under refrigeration conditions. Results showed that the meat fillets packaged in PLA developed a redder color and showed certain indications of dehydration and oxidation, being more noticeably after 11 days of storage, due to the higher water vapor and oxygen permeance values of the biopolymer multilayer. However, the pH changes and bacterial growth in the cold-stored fresh pork meat samples were minimal and very similar in the three tested multilayer films, successfully accomplishing the requirements of the food quality and safety standards at the end of storage.

Morphological, barrier, thermal, and rheological properties of high-pressure treated co-extruded polylactide films and the suitability for food packaging

Commercial coextruded polylactide films have demonstrated high stiffness, gas and aroma barrier, but little is known about their microstructure and film morphology, in particular in a high-pressure (HP) environment. Therefore, the objective of this study is to examine the influence of the HP-treatment in the pressure range of 300–600 MPa for a residence time of 15 min, and thereafter, assessed changes in the morphological, thermal, rheological, optical, and barrier properties of two commercial co-extruded polylactide films with varying thickness (25-μm and 75-μm). The barrier properties of the films remained unchanged by the treatment except for the thin film (25-μm) that was treated at 600 MPa. The surface morphology and roughness of the thin films were affected by the HP-treatment while XRD analysis confirmed changes in the structure/crystallinity of PLA. The TGA curves demonstrated a variation in thermograms between the two films. HP-treated films exhibited predominating liquid-like property on the melt, and the thin films exhibited higher mechanical rigidity than the thick films. The results demonstrated that HP-treatment significantly affected microstructures of the film. More studies are required for the commercial success of these films by improving film properties and the interaction between the film and the food under high-pressure.

Polylactide Films with the Addition of Olive Leaf Extract-Physico-Chemical Characterization.

The aim of this work was to obtain and characterize polylactide films (PLA) with the addition of poly(ethylene glycol) (PEG) as a plasticizer and chloroformic olive leaf extract (OLE). The composition of OLE was characterized by LC-MS/MS techniques. The films with the potential for using in the food packaging industry were prepared using a solvent evaporation method. The total content of the phenolic compounds and DPPH radical scavenging assay of all the obtained materials have been tested. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (FTIR-ATR) allows for determining the molecular structure, while Scanning Electron Microscopy (SEM) indicated differences in the films’ surface morphology. Among other crucial properties, mechanical properties, thickness, degree of crystallinity, water vapor permeation rate (WVPR), and color change have also been evaluated. The results showed that OLE contains numerous active substances, including phenolic compounds, and PLA/PEG/OLE films are characterized by improved antioxidant properties. The OLE addition into PLA/PEG increases the material crystallinity, while the WVPR values remain almost unaffected. From these studies, significant insight was gained into the possibility of the application of chloroform as a solvent for both olive leaf extraction and for the preparation of OLE, PLA, and PEG-containing film-forming solutions. Finally, evaporation of the solvent from OLE can be omitted.

A comparative study of the interaction between the dried ink layer andPLAfilm used for packaging purposes

AbstractThis research aims at comparing the interactions between the water‐based printing ink and polylactide (PLA) printing base. As a reference base, a polyethylene terephthalate (PET) film was chosen. The wettability of both films was investigated. The Owens–Wendt method was applied to calculate the surface free energy (SFE). The values of SFE and its polar and dispersive components were compared with the surface tension (ST) of the ink and the polar and dispersive components of ST. The wetting envelopes of the investigated PLA and PET films are presented. Finally, the bonding strength between the dried ink layer and the printing base was analyzed. The PET film exhibited higher values of SFE. However, the bonding strength between the dried ink layer and the printing base was higher for PLA films. Our results reveal that PLA films can be an excellent choice as packaging materials, with comparable or even better print quality than conventional fossil‐based plastics.

Fabrication of Microstructured Polylactide Films by Templating Techniques

Fabrication of Microstructured Polylactide Films by Templating Techniques

Kinetics of the release of brilliant green from nanoporous polylactide obtained by a crazing mechanism

Structurally variable nanoporous polylactide (PLA) films containing brilliant green (BG) as a functional antiseptic additive have been obtained by a crazing mechanism. The in vitro release of BG from the porous PLA films into a sodium phosphate buffer solution at 37 °C has been examined by spectrophotometry.

Great enhancement of mechanical features in PLA based composites containing aligned few layer graphene (FLG), the effect of FLG loading, size, and dispersion on mechanical and thermal properties

AbstractFour series of polylactide (PLA) based composite films containing horizontally aligned few layer graphene (FLG) flakes of high aspect ratio and adsorbed albumin are prepared. The mechanical and thermal properties varies with percentage, dispersion degree and size of FLG flakes. Great improvement up to 290% and 360% of tensile modulus and strength respectively were obtained for the composite containing high lateral size of FLG at 0.17% wt, and up to 60% and 80% for the composite with very well dispersed 0.02% wt FLG. The composites of PLA and PEG‐PLLA containing very well dispersed FLG flakes at 0.07% wt are ductile showing enhancement of elongation at break up to respectively 80% and 88%. Relatively high electrical conductivity, 5 × 10−3 S/cm, is measured for PLA film charged with 3% of FLG.

Storage stability of the oxygen plasma-modified PLA film

Polylactide (PLA) is the second most popular biodegradable plastic in the world currently and is a growing alternative to traditional plastics. Similar to most of the polymers, PLA requires surface activation before further processing, among others plasma activation. Hydrophobic recovery is a major problem of plasma-treated polymer; therefore, authors performed extensive research on the storage stability of the oxygen plasma-treated PLA film. For that purpose the low-temperature plasma with oxygen was applied on PLA film and its influence on surface-free energy (SFE) and contact angle (CA) with water, diiodomethane and ethylene glycol was analysed together with their subsequent hydrophobic recovery during storage. In addition, chemical changes were measured with X-ray photoelectron spectroscopy (XPS), mass loss was determined by weight measurement and the surface topography was measured by means of confocal microscopy. The best wettability of the substrate was observed after 2 and 10 min activation time, which was confirmed by the lowest CA, as well as the highest values of SFE. The degree of hydrophobic recovery depends on treatment time and is most stable for 6 min treatment. The PLA hydrophobic recovery reached its peak after a storage period of 14 days, after which the hydrophilic properties improved again, regardless of the activation time.

Anti-Adhesive Effect of Porous Polylactide Film in Rats.

Excessive adhesion between tissues on a significant area can cause the development of disorders, cosmetic problems, and ileus. Methods for preventing adhesion include the use of drugs and anti-adhesion barriers for physical blocking. In this study, the adhesion prevention effect of polylactide film in porous form was analyzed. A porous polylactide film was manufactured using a molecular weight of at least 100,000. To generate porosity, 98% methylene chloride and 95% ethyl alcohol were used as solvents. The thickness, surface, and internal pore shape of film were investigated. The crystal structures and melting temperature of film were measured. In the rat model, the presence and severity of adhesion were then analyzed. The thickness of the film ranged from 10 to 20 µm. The surface of the film contained pores with diameters of less than 10 µm. Partial crystallinity appeared from 15° to 20°, but the structure was amorphous overall. In the rat cecum abrasion model, adhesion occurred in 3 of the 13 rats in the polylactide experimental group, representing a 23.1% incidence rate. There were statistically significant differences in the severity of adhesion. The use of porous polylactide films can reduce the incidence of adhesion.

Effect of tungsten disulfide nanotubes on crystallization of polylactide under uniaxial deformation and annealing

Tungsten disulfide (WS2) nanotubes (NTs) are examined here as a filler for polylactide (PLA) for their ability to accelerate PLA crystallization and for their promising biocompatibility in relevant to biomedical applications of PLA-WS2 nanocomposites. In this work, we have studied the structural and thermal properties of PLA-WS2 nanocomposite films varying the concentration of WS2 NTs from 0 (neat PLA) to 0.6 wt%. The films were uniaxially drawn at 90 °C and annealed at the same temperature for 3 and 10 min. Using wide angle x-ray scattering, Raman spectroscopy and differential scanning calorimetry, we probed the effects of WS2 NT addition on the structure of the PLA films at various stages of processing (unstretched, stretching, annealing). We found that 0.6 wt% of WS2 induces the same level of crystallinity in as stretched PLA-WS2 as annealing in neat PLA for 10 min. These data provide useful insights into the role of WS2 NTs on the structural evolution of PLA-WS2 composites under uniaxial deformation, and extend their applicability to situations where fine tuning of PLA crystallinity is desirable.

Proliferation and adhesion of fibroblasts in vitro on polylactide films

Proliferation and adhesion of fibroblasts in vitro on polylactide films

Nature and mechanisms of relaxation processes in biocompatible polylactide films

Nature and mechanisms of relaxation processes in biocompatible polylactide films

Polylactide films produced with bixin and acetyl tributyl citrate: Functional properties for active packaging

AbstractPackaging materials are decisive to preserve the quality and nutritional value of food. Polylactide (PLA) is a biodegradable polymer with adequate mechanical properties for packaging applications, but its moderate oxygen barrier properties and high UV light transmission hamper its performance as packaging for oxygen‐ and light‐sensitive products. Bixin, a carotenoid with coloring and antioxidant character, was used to improve the light barrier of PLA films plasticized or not with acetyl tri‐butyl citrate (ATBC). The films were subjected to thermal treatment mimicking polymer processing temperatures. Despite more than 74 wt% of bixin degraded during heat treatment, films were still blocking up to 95% of UVA and 90% of UVB transmission. Plasticizing PLA with ATBC accelerated up to six times the bixin release into a food simulant, which allowed to reach relevant concentrations for food preservation. In conclusion, bixin is a promising natural antioxidant and UV‐shielding additive of biodegradable packaging.

Plant extracts as natural additives for environmentally friendly polylactide films

The use of biodegradable polymers derived from renewable sources may in the future be a solution to the problem of environmental pollution with polymer waste. By using natural fillers and additives in addition to the biodegradable matrix, we are able to obtain truly eco-fiendly green materials. The paper presents the result of selected properties of polylactide films containing natural coffee, cocoa or cinnamon extracts which primarily were proposed as natural antioxidants. The focus was on properties relevant to the packaging industry such as color and transparency, surface roughness, wettability, surface energy, friction coefficient, adhesion strength and gas permeability. It was found that the extracts used at the appropriate contents have a beneficial effect on the studied properties. The obtained results were often better not only than the values ​​obtained for pure polymer, but also better than the values ​​obtained for the film containing a synthetic anti-aging compound. It can therefore be concluded that the proposed plant extracts have a positive effect not only on the aging resistance of polylactide, but also other properties of this polymer. They can be therefore an alternative to synthetic additives.

Tuning wettability and mechanical property of polylactide composite films with in-situ nanofibrils of poly(butylene adipate-co-terephthalate)

The poor hydrophobicity and toughness of polylactide (PLA) films make it difficult to meet the requirements of barrier, printing and moisture-proof material. How to improve the two drawbacks of PLA simultaneously is a daunting challenge at present. In this work, we introduce poly (butylene adipate-co-terephthalate) (PBAT) as a second flexible phase into PLA matrix and concomitantly impose intensive elongational flow by two-stage drawing. Under the elongational flow field, the PLA/PBAT film can form the oriented structure combining in-situ nanofibrils with oriented lamellae, exhibiting excellent stiffness-toughness balance. Then surface treatment via moderate alkaline etching makes the micro/nano structure expose on the surface, which can effectively improve the hydrophobicity of the surface. We further investigates the influence of blend composition, drawing ratio and etching time on the oriented structure, mechanical and wetting properties. It is found that the PLA/PBAT film with the weight ratio of 70/30, low draw ratio of 2.7 and etching time of 24 h has the optimal properties, which possesses Young's modulus of 2.53 GPa, yield strength of 51.9 MPa, elongation of break of 131.8% and water contact angle of 131.8°. It is noteworthy that the film can mainly keep original mechanical after surface treatment. This work could offer a facile and effective method to fabricate the green PLA based film with good mechanical properties and hydrophobicity in a large scale.

Hydrolytic degradation of polylactide films deformed by the environmental crazing mechanism

Hydrolytic degradation of porous polylactide (PLA) films with various porosity and morphology has been thoroughly investigated. It has been found that the structural and mechanical modification of PLA films by the environmental crazing mechanism results in the formation of a porous structure, is accompanied by the change in molecular-weight characteristics of the polymer and affects the localization and rate of its hydrolytic degradation. After the films were exposed in phosphate-buffered saline solution at 37 °C for 6 weeks, their average molecular weights MW and MN decreased by 1.5–2 and 3–5 times respectively, while their dispersity ĐM increased to 4–5. For PLA films containing alternating porous crazes and nonporous bulk parts, the hydrolysis leads to the appearance of bimodal molecular-weight distribution (MWD) curves. The degradation of the polymer material localizes predominantly at the craze–bulk polymer interfaces, thereby leading to a rather rapid and significant decrease in the deformation and strength properties of the films, which eventually become brittle. For PLA films, that have completely passed to the fibrillar-porous structure during the hydrolytic degradation, the character of the MWD curves remains preserved, but they gradually widen and shift toward lower molecular weights. The destruction of similar samples occurs uniformly throughout the volume, and the changes in their structural and mechanical parameters are not so abrupt, and even after the hydrolysis for 6 weeks their strength remains at a level of 90 MPa. When the porous matrix of PLA is filled with calcium phosphate (up to 30 wt%), the degradation of the polymer material occurs predominantly in the crazes and hardly proceeds in the bulk parts. The approaches proposed using PLA as an example enable one to control the degradation processes in polymers by varying their structural and morphological characteristics and incorporating inorganic fillers, thus opening new ways to the creation of bioactive and biodegradable materials with predictable degradation times.

Influence of Myrrh Extracts on the Properties of PLA Films and Melt-Spun Multifilament Yarns.

A possible approach for providing new properties for textiles is the insertion of natural ingredients into the textile product during the process of its manufacture. Myrrh has long been used in medicine as an antibacterial and antifungal material. Polylactide (PLA) is a thermoplastic synthetic biopolymer obtained from renewable resources—and due its biodegradability, is also widely used in medicine. In this study, films and multifilament yarns from modified biodegradable PLA granules with ethanolic and aqueous myrrh extracts were developed and characterized. Optical microscopy was used to determine the surface morphology of PLA/myrrh multifilament yarns. Tensile tests, ultraviolet-visible (UV-vis), differential scanning calorimetry (DSC) were applied to determine, consequently, mechanical, optical properties and degree of crystallinity of PLA/myrrh films and multifilament yarns. The chemical composition of PLA/myrrh multifilament yarns was estimated by Fourier-transform infrared (FTIR) spectroscopy method. The results showed that it is possible to form PLA melt-spun multifilament yarns with myrrh extract. The type of myrrh extract (ethanolic or aqueous) has a significant influence on the mechanical and optical properties of the PLA films and melt-spun yarns. The mechanical properties of PLA films and melt-spun multifilament yarns formed from PLA granules with aqueous myrrh extract decreased 19% and 21% more than PLA with ethanolic extract, respectively. Analysis of UV-vis spectra showed that, due to the yellow hue, the reflectance of PLA films and melt-spun PLA multifilament yarns modified with myrrh extracts decreased exponentially. The DSC test showed that multifilament yarns from PLA modified with aqueous extract had the highest degree of crystallization.

Tailoring the Properties of Thermo-Compressed Polylactide Films for Food Packaging Applications by Individual and Combined Additions of Lactic Acid Oligomer and Halloysite Nanotubes.

In this work, films of polylactide (PLA) prepared by extrusion and thermo-compression were plasticized with oligomer of lactic acid (OLA) at contents of 5, 10, and 20 wt%. The PLA sample containing 20 wt% of OLA was also reinforced with 3, 6, and 9 parts per hundred resin (phr) of halloysite nanotubes (HNTs) to increase the mechanical strength and thermal stability of the films. Prior to melt mixing, ultrasound-assisted dispersion of the nanoclays in OLA was carried out at 100 °C to promote the HNTs dispersion in PLA and the resultant films were characterized with the aim to ascertain their potential in food packaging. It was observed that either the individual addition of OLA or combined with 3 phr of HNTs did not significantly affect the optical properties of the PLA films, whereas higher nanoclay contents reduced lightness and induced certain green and blue tonalities. The addition of 20 wt% of OLA increased ductility of the PLA film by nearly 75% and also decreased the glass transition temperature (Tg) by over 18 °C. The incorporation of 3 phr of HNTs into the OLA-containing PLA films delayed thermal degradation by 7 °C and additionally reduced the permeabilities to water and limonene vapors by approximately 8% and 47%, respectively. Interestingly, the highest barrier performance was attained for the unfilled PLA film plasticized with 10 wt% of OLA, which was attributed to a crystallinity increase and an effect of “antiplasticization”. However, loadings of 6 and 9 phr of HNTs resulted in the formation of small aggregates that impaired the performance of the blend films. The here-attained results demonstrates that the properties of ternary systems of PLA/OLA/HNTs can be tuned when the plasticizer and nanofiller contents are carefully chosen and the resultant nanocomposite films can be proposed as a bio-sourced alternative for compostable packaging applications.