PLA-based Films Research Articles

Development and characterization of PLA and Cassava starch‐based novel biodegradable film used for food packaging application

Pure starch like PLA is an outstanding substitute to prepare packaging film, nevertheless, because of its greater hydrophilicity, mixing it with other starch become essential. Cassava is a root vegetable that is an excellent source of starch, and it can be used to prepare bio-based packaging materials. The packaging films were developed by blown film extrusion method using 10% and 20% cassava starch, blended with PLA. The water vapor barrier property, and other physico-chemical properties of the packaging films were determined, and it was observed that the film characteristics of PLA and Cassava starch up to 20%, were equally suitable for packaging application to virgin PLA-based film. The biodegradable film developed for MA packaging, had a potential to retain the quality attributes of capsicum up to 12 and 24 days at 25°C and 8°C, respectively as compared to the shelf-life of unpackaged capsicum viz. 4 and 9 days at respective temperatures. Novelty impact statement The film characteristics like haze %, tensile strength, OTR and WVTR parameters for PLA, and 20% cassava starch were found to be 89.68%, 25.16 MPa, 123.92 cc/m2/day, and 217 gm/m2/day, respectively. The physico-chemical characteristics of the developed packaging films were found to be better as compared to other starch and PLA blended film. The outcomes of biodegradable film-based MA packaging were compared to a non-biodegradable film-based MA packaging of capsicum, it was observed that the application of biodegradable film offers a new alternative over the non-biodegradable polymeric film for MA packaging of fresh produce without compromising its quality.

Evaluation of the Potential Effects of Olive Wood Flour ( Olea Europaea L. ) and Essential Oils on Antimicrobial Activity of Pla-Based Films

Evaluation of the Potential Effects of Olive Wood Flour ( Olea Europaea L. ) and Essential Oils on Antimicrobial Activity of Pla-Based Films

Development of antimicrobial films based on poly(lactic acid) incorporated with Thymus vulgaris essential oil and ethanolic extract of Mediterranean propolis

Antimicrobial films based on polylactic acid (PLA) were developed by incorporating Thymus vulgaris essential oil (TV-EOs) with different concentrations of ethanolic extract of Mediterranean propolis (EEP) (5 wt% and 10 wt% based on PLA). The antimicrobial activities of EEP were performed by the agar disc diffusion method. The EEP exhibited high antimicrobial properties with inhibition zone diameter of 12.1 and 11.58 mm against Staphylococcus aureus and Penicillium sp., respectively. The addition of TV-EOs to films containing 5 and 10 wt% of EEP decrease the elastic modulus from 1292 MPa to 1084 MPa and 911.1 MPa to 794 MPa compared with films containing 5 and 10% of EEP alone, respectively. However, the elongation at break increased by 64% after the addition of TV-EOs to the film containing 10 wt% of EEP. Thermal stability of films improvement by the addition of TV-EOs and EEP. Antimicrobial activity of the films showed that films containing 10 wt% EEP inhibited the growth of Candida albicans and the combination of EEP and TV-EOs in the PLA matrix showed a synergistic effect against Escherichia coli. The developed PLA-based films with antimicrobial activity have a potential application in food packaging to increase the shelf life of packaged food.

Natural antimicrobials and antioxidants added to polylactic acid packaging films. Part I: Polymer processing techniques.

Currently, reducing packaging plastic waste and food losses are concerning topics in the food packaging industry. As an alternative for these challenges, antimicrobial and antioxidant materials have been developed by incorporating active agents (AAs) into biodegradable polymers to extend the food shelf life. In this context, developing biodegradable active materials based on polylactic acid (PLA) and natural compounds are a great alternative to maintain food safety and non-toxicity of the packaging. AAs, such as essential oils and polyphenols, have been added mainly as antimicrobial and antioxidant natural compounds in PLA packaging. In this review, current techniques used to develop active PLA packaging films were described in order to critically compare their feasibility, advantages, limitations, and relevant processing aspects. The analysis was focused on the processing conditions, such as operation variables and stages, and factors related to the AAs, such as their concentrations, weight losses during processing, and incorporation technique, among others. Recent developments of active PLA-based monolayers and bi- or multilayer films were also considered. In addition, patents on inventions and technologies on active PLA-based films for food packaging were reviewed. This review highlights that the selection of the processing technique and conditions to obtain active PLA depends on the type of the AA regarding its volatility, solubility, and thermosensitivity.

Migration kinetic of silver from polylactic acid nanocomposite film into acidic food simulant after different high-pressure food processing.

The migration study of nano-Ag migration from polylactic acid (PLA) films was studied. Samples treated by high-pressure food processing (0, 100, 200, 300, and 400MPa pressure) were soaked in acetic acid solution and incubated at 20°C for 90 days. At the end of storage, nano-Ag particles (AgNPs) migration from the PLA/AgNPs composite film treated under 200MPa high pressure was the lowest. However, AgNPs migration was accelerated under 400MPa high pressure. High-pressure processing (200MPa) could cause denser structure and higher crystallinity degree in films than other treatments. Lower amount of AgNPs induced a decline in the intensity of specific characteristic peaks. The diffraction peak intensity of α-crystal for the film sample treated with 400MPa was the lowest on day 60. The crystallization index of the PLA matrix changed with different high-pressure processing. The result indicated that appropriate high-pressure food processing could effectively suppress AgNPs migration from PLA-based film while contacting with acidic acid food simulant. PRACTICAL APPLICATION: The release of nanoparticles from food packaging material is a very important matter when the migration is concerned with regulatory and toxicity issues. The study described the migration kinetic of AgNPs from PLA nanocomposite film into acidic food simulant after different high-pressure food processing. The results indicated that the PLA/AgNPs nanocomposite film was safe for acidic food after high-pressure treatment.

Poly(lactic acid)-based bionanocomposites: effects of ZnO nanoparticles and essential oils on physicochemical properties

The main shortcoming of polylactic acid (PLA) for packaging applications is its brittleness. Thus, there is a pronounced interest in the potential use of PLA/zinc oxide nanoparticle (ZnO NP) systems as active food packaging. In this study, ZnO NPs and two types of essential oils (EOs) including Zataria multiflora L. (ZEO) and Mentha piperita L. (MEO) at different concentrations (0.5%, 1%, 1.5% w/w) were used for the production of active PLA-based bionanocomposites for packaging applications. The presence of ZnO NPs and EOs led to increased film thickness and improved contact angle properties. ZnO NPs boosted the PLA-based films’ WVP, whereas the EOs had the opposite effect. The increase in the ZEO and MEO content reduced the ultimate tensile strength and Young’s modulus and increased the elongation at break. The X-ray diffraction and Fourier transform infrared spectroscopy results confirmed that the improvements are related to the ZnO NPs exfoliation and good interaction between PLA and ZnO NPs in the presence of EOs. Differential scanning calorimetry analysis showed that the incorporation of ZnO NPs increased the glass transition temperature (Tg), but did not change the melting temperature (Tm), though the addition of the EOs lowered the values of both parameters. Morphology analysis by scanning electron microscopy and atomic force microscopy showed that the presence of ZEO/MEO led to increased pinholes, pores, and roughness in the microstructure of the films. These results revealed that ZnO-PLA films containing EOs may be used as controlled release antimicrobial food active packaging.

Transparent films by ionic liquid welding of cellulose nanofibers and polylactide: Enhanced biodegradability in marine environments

We introduce a green and facile method to compatibilize hydrophobic polylactide (PLA) with hydrophilic cellulose nanofibers (CNF) by using ionic liquid ([DBNH][OAc]) welding with a cosolvent system (gamma-valerolactone). Such welding affords strong (230 MPa tensile strength), flexible (13% elongation at break), transparent (>90%) and defect-free CNF/PLA films. The films are biodegradable in marine environments (70% degradation in 7 weeks), facilitating the otherwise slow PLA decomposition. Physical, chemical and structural features of the films before and after welding are compared and factored in the trends observed for degradation in seawater. The results point to the possibility of PLA-based films forming a co-continuous system with nanocellulose to achieve an improved performance. The role of film morphology, hydrophobicity, and crystallinity is discussed to add to the prospects for packaging materials that simultaneously display accelerated degradability in marine environments.

A Socio-economic Indicator for EoL Strategies for Bio-based Products

In recent years, the bioeconomy has received increased attention from policy makers and practitioners, leading to a first switch from fossil to bio-based products. To open up new market opportunities, transparent information on the sustainability of bio-based products must be provided, taking into account all life cycle stages. The determination of suitable end of life (EoL) strategies furthers this aim. Notably, the socio-economic aspects of EoL alternatives associated with bio-based products have been neglected. This paper contributes to filling this gap by proposing a new socio-economic indicator for EoL (SEI-EoL). The SEI-EoL is developed from an integrated analytic hierarchy process–multicriteria decision analysis (AHP-MCDA) model based on experts' involvement, and is capable of measuring and comparing the socio-economic performance of EoL alternatives for bio-based products. The SEI-EoL is applied to the specific case of polylactic acid (PLA)–based film for food packaging. The results indicate that value chain actors are the most influential category of stakeholders in EoL management, and the assessment of criteria shows that waste disposal cost, resource efficiency and EoL responsibility play a key role in this management. The highest value EoL strategy for PLA-based film for food packaging is mechanical recycling, followed by chemical recycling. Circularity assessment, policy maker responsibility and incentives for recycled materials/green processes represent the most relevant items to consider for policy recommendations and actions.

Survey data for assessing the socio-economic performance of End of Life options of a bio-based product based on expert knowledge.

This data article aims at providing a data description about the manuscript entitled “A socio-economic indicator for EoL strategies for bio-based products” [1]. Data regarding the socio-economic assessment of End of Life (EoL) options for the specific case of PLA-based film for food packaging are presented, with a special emphasis on policy recommendations and actions for the EoL practices in the bioeconomy sectors. A new framework, based on data gathering and validation through experts involvement, is proposed in order to calculate a new indicator to measure the socio-economic performance of EoL practices (SEI-EoL) for bio-based products. Experts were identified from the Horizon 2020 LIFE-funded projects and/or Scopus databases. Two rounds of survey were carried out to determine the weights of socio-economic criteria for bio-based products and the values for the selected case study. The aggregation of these data enabled us to obtain a final ranking of different EoL alternatives. Finally, a third round of survey was conducted to further deepen our understanding of actions and recommendations needed to improve EoL practices in bio-based sectors. Resulting data have a mix of quantitative and qualitative characterization. A potential reuse of these data can allow future estimations, empirical analyses or a direct comparison with the use of experimental observations.

Antimicrobial film based on polylactic acid and carbon nanotube for controlled cinnamaldehyde release

A controlled-release antibacterial active food packaging film was prepared from polylactic acid (PLA), poly (ε-caprolactone) (PCL), carbon nanotubes (CNTs), and cinnamaldehyde (CIN) by solvent evaporation method. The properties and antibacterial activities of CIN loaded PLA/CNTs/CIN film was characterized. Furthermore, the release behavior of CIN from PLA-based antibacterial film was quantified. The introduction of CNT and CIN would not significantly affect the barrier properties of PLA-based film, but would significantly enhance the UV resistance of the film. The co-action of CNTs and CIN led to the decrease of the glass transition temperature of the film and enhanced the elongation at break of the film. The PLA/CNTs/CIN film could continuously release CIN for 21 days in ambient storage, and antibacterial effect of the film on Staphylococcus aureus and Escherichia coli could be maintained for 21 days, during which the antibacterial effect gradually reduced and maintained for 7 days longer than the film without CNTs. According to the research results, The PLA/CNTs/CIN composites have great application potential in antibacterial active food packaging film.

Modification of PLA-Based Films by Grafting or Coating.

Recently, the demand for the use of natural polymers in the cosmetic, biomedical, and sanitary sectors has been increasing. In order to meet specific functional properties of the products, usually, the incorporation of the active component is required. One of the main problems is enabling compatibility between hydrophobic and hydrophilic surfaces. Therefore, surface modification is necessary. Poly(lactide) (PLA) is a natural polymer that has attracted a lot ofattention in recent years. It is bio-based, can be produced from carbohydrate sources like corn, and it is biodegradable. The main goal of this work was the functionalization of PLA, inserting antiseptic and anti-inflammatory nanostructured systems based on chitin nanofibrils–nanolignin complexes ready to be used in the biomedical, cosmetics, and sanitary sectors. The specific challenge of this investigation was to increase the interaction between the hydrophobic PLA matrix with hydrophilic chitin–lignin nanoparticle complexes. First, chemical modification via the “grafting from” method using lactide oligomers was performed. Then, active coatings with modified and unmodified chitin–lignin nanoparticle complexes were prepared and applied on extruded PLA-based sheets. The chemical, thermal, and mechanical characterization of prepared samples was carried out and the obtained results were discussed.

Effectiveness of PECVD deposited nano-silicon oxide protective layer for polylactic acid film: Barrier and surface properties

Abstract This study evaluated the effectiveness of a silicon oxide (SiOx) layer of approximately 100 nm thickness manufactured by plasma enhanced chemical vapor deposition (PECVD) as a protective coating for PLA-based films to reduce the corrosion and contaminant migration caused by food contact. The migration kinetics of plasticizer diethylene glycol dibenzoate (DEDB) in the films and the barrier and surface properties of films were studied. Results indicated that compared to PLA-based films, the final DEDB migration amount of SiOx/PLA-coated films was reduced by 23.75-36.90% in food simulants A, B, C and D1, while the time to reach migration equilibrium was prolonged. SiOx layer increased the static water contact angle of the PLA film from 85.5 ± 0.4° to 101.8 ± 1.2° and decreased the oxygen and water vapor transmission rates by 48.45% and 28.53%, respectively. The nanostructured SiOx barrier layer was effective in protecting the shape and transparency of the coated films.

Preparation and characterization of biocomposite packaging film from poly(lactic acid) and acylated microcrystalline cellulose using rice bran oil

Surface acylation of microcrystalline cellulose (MCC) was performed using rice bran oil (RBO). The resultant acylated MCC (RAMCC) exhibited reduced polarity as compared with MCC. Attenuated Total Reflection (ATR)- Fourier transform infrared (FTIR) spectroscopy confirmed hydrophobic MCC modification. RAMCC and MCC were incorporated into PLA matrix and their influence on morphological, mechanical, thermal and barrier properties of the PLA based biocomposite were analyzed. PLA/RAMCC biocomposite (with 2 wt% loading) exhibited lower water sorption compared to PLA film and PLA/MCC. X-ray Diffraction (XRD) analysis result showed an increase in crystallinity of PLA/RAMCC and reduction in water vapour permeability as compared to PLA film and PLA/MCC composite. PLA/RAMCC exhibited the best mechanical, thermal and UV barrier properties. The fractured surfaces of the composites showed an even distribution of RAMCC throughout PLA matrix. Biodegradability of samples was characterized using soil buried method. The cytotoxicity of the developed PLA-based films was evaluated on human dermal fibroblast (HDF) monolayer culture by the MTT method and it has shown that the films were non-cytotoxic thus indicating their biocompatibility and non-toxicity. These biodegradable composite films can be a sustainable utilization of RBO and MCC in the packaging application.

Physico-chemical characterization of natural lake pigments obtained from Caesalpinia Sappan Linn. and their composite films for poly(lactic acid)-based packaging materials

A newly colored biodegradable PLA-based film was fabricated from a compatibilized poly(lactic acid) poly(butylene adipate-co-terephthalate) blend (PLA/PBAT/TBT) using the natural lake pigment of Sappan. The natural lake pigment of Sappan was prepared as a Sappan colorant-adsorbed kaolinite (S-KT). S-KT composite in the form of an insoluble pigment and was prepared via co-precipitation and adsorption under basic conditions. It had a pinkish-red color and a maximum absorption of 516 nm. The stability of the natural lake pigment was improved and was confirmed by the improvement of the initial and maximum degradation temperatures from the TGA results, which could be attributed to the electrostatic attraction due to the process of chelation. The chelation that occurred between the Al(III) ion, the oxygen atoms of kaolinite surface and the brazilein molecules was proposed. The influence of S-KT content in the compatibilized blended films, known as S-KT composite films, was investigated by comparison with the KT composite film and the film without fillers. When the content of S-KT increased, the S-KT composite films exhibited a darker pinkish-red color. The mechanical properties in terms of strength increased due to KT acting as a nucleating agent with a 92% increase in the heat of crystallization in the S-KT7 film when compared with the film without fillers. The exfoliated-intercalated structure of S-KT resulted from the KT platelet disaggregation by brazilein adsorption and the intercalating of Al3+cations chelation as a hybrid interaction on the KT surface, which was indicated by the SEM. In addition, S-KT composite film could effectively resist heat at high temperatures with the maximum degradation temperature ranging from 337 to 393° C. This occurred as a result of KT clay acting as a superior insulator. Based on these results, the natural lake pigments presented the potential to be employed in the biodegradable polymer and could be used as a substitute for more toxic pigments. The biodegradable PLA-based colored films described here have a potential to be used in packaging applications. They offer the potential to increase the value-added appeal of products, with the benefit of being considered environmentally friendly by the consumer.

Controllable degradation rates, antibacterial, free-standing and highly transparent films based on polylactic acid and chitosan

Plastic wastes have brought increasingly serious environmental white pollution, further boosting the research of degradable materials. Here, the free-standing degradable film based on polylactic acid(PLA)/ chitosan(CS) was fabricated by non-solvent induce phase separation method. The optical and scanning electron microscope images, FTIR spectra, transmittance, water contact angle, thermal gravity analysis, differential scanning calorimetry, degradation rates and antibacterial activity were tested. The prepared film had porous structure and highly transparent capability. And the hydrophilicity of composites was improved while the thermal stability was slightly reduced. Besides the degradation rates could be tuned in terms of structures through changing pore sizes of PLA-based films. Moreover, the film showed strong antibacterial activity against E. coli. The free-standing and highly transparent degradable films have great potential applications in biomedical fileds and food packaging areas.

One-pot synthesis of poly(lactic acid) with terminal methacrylate groups for the adjustment of mechanical properties of biomaterials

Poly(lactic acid) with terminal methacrylate groups was synthesized in one pot using 2-hydroxyethyl methacrylate as initiator, whose content affected the polymer molecular weight. The impact of the obtained modified polymer crosslinking on the mechanical properties of PLA-based films was established.

Antioxidant migration resistance of SiOx layer in SiOx/PLA coated film

ABSTRACTAs novel materials for food contact packaging, inorganic silicon oxide (SiOx) films are high barrier property materials that have been developed rapidly and have attracted the attention of many manufacturers. For the safe use of SiOx films for food packaging it is vital to study the interaction between SiOx layers and food contaminants, as well as the function of a SiOx barrier layer in antioxidant migration resistance. In this study, we deposited a SiOx layer on polylactic acid (PLA)-based films to prepare SiOx/PLA coated films by plasma-enhanced chemical vapour deposition. Additionally, we compared PLA-based films and SiOx/PLA coated films in terms of the migration of different antioxidants (e.g. t-butylhydroquinone [TBHQ], butylated hydroxyanisole [BHA], and butylated hydroxytoluene [BHT]) via specific migration experiments and then investigated the effects of a SiOx layer on antioxidant migration under different conditions. The results indicate that antioxidant migration from SiOx/PLA coated films is similar to that for PLA-based films: with increase of temperature, decrease of food simulant polarity, and increase of single-sided contact time, the antioxidant migration rate and amount in SiOx/PLA coated films increase. The SiOx barrier layer significantly reduced the amount of migration of antioxidants with small and similar molecular weights and similar physical and chemical properties, while the degree of migration blocking was not significantly different among the studied antioxidants. However, the migration was affected by temperature and food simulant. Depending on the food simulants considered, the migration amount in SiOx/PLA coated films was reduced compared with that in PLA-based films by 42–46%, 44–47%, and 44–46% for TBHQ, BHA, and BHT, respectively.

Concentration-dependent anti-/pro-oxidant activity of natural phenolic compounds in bio-polyesters

In this work, the potential of several naturally occurring phenolic compounds, such as Ferulic Acid (FA), Vanillic Acid (VA), Vitamin E (VE) and Quercetin (Q), as stabilizers against the photo-oxidative degradation of Polylactic acid (PLA) has been assessed. Specifically, PLA-based films containing different amounts of considered stabilizers have been formulated and their photo-stability under UVB exposure has been evaluated. The preliminary characterization of the formulated films shows that all used stabilizers exert plasticizing action, as probed by rheological analysis, due to their low molecular weight. Moreover, no significant modification of the PLA crystallinity has been noticed in presence of used natural compounds.The study of the photo-oxidation behaviour of PLA-based systems suggests that, among all used natural phenolic compounds, FA and Q are suitable anti-oxidant for PLA, if they are added at low content. Surprisingly, all considered natural compounds, exert a pronounced pro-degradant action in PLA matrix, if their content overcomes a certain specific threshold. This finding has been related to the known concentration-dependent anti-/pro-oxidant activity of used phenolic compounds, that results exacerbated in presence of traces of transition metals, such as iron and copper.

PLA films with improved flexibility properties by using maleinized cottonseed oil

This work assesses the potential of maleinized cottonseed oil – MCSO as plasticizer in poly(lactic acid) – PLA films with improved ductile behaviour. The effects of MCSO are compared with commercially available maleinized oil, i.e. maleinized linseed oil – MLO in terms of mechanical, thermal and barrier properties, as well as morphology changes. Plasticized PLA formulations were obtained with a maleinized oil content in the 0–10wt% range. Addition of both maleinized vegetable oils leads to a slight decrease in the glass transition temperature (Tg) of neat PLA from 63°C to 60–61°C. Nevertheless, MCSO provides better overall properties. Addition of 7.5wt% MCSO increases the elongation at break by 292%. Regarding the barrier properties, both maleinized vegetable oils increase the oxygen transmission rate – OTR. Nevertheless, this increase is less pronounced in the case of MCSO thus indicating its higher efficiency compared to MLO. On the other hand, addition of both maleinized vegetable oils do not compromise the overall disintegration of the obtained PLA formulations, thus positioning these additives as environmentally friendly solutions to increase ductile properties in PLA-based films.

Effect of PLA/ZnO Packaging and Gamma Radiation on the Content of Listeria innocua, Escherichia coli and Salmonella enterica on Ham during Storage at 4 °C

The effect of ZnO and low γ-radiation on PLA based-films was investigated to be used for food packaging application. Ham slices were inoculated with E. coli, L. innocua and S. enterica and then covered with PLA and PLA/5% ZnO films. The samples were irradiated with a γ-radiation dose of 0.3 kGy at dose rate of 13.5 kGy/h. Microbiological analysis was performed at 0, 1 and 5 days on samples stored at 4 °C. Results showed that no onsistent reduction of bacteria was obtained, even at the fifth day of storage, when the ham was covered with PLA/5% ZnO film and no γ-radiation was performed. The use of γ-radiation results necessary to reduce the bacteria growth. In fact E. coli and S. enterica were not detected after 5 days of storage; whereas in the case of test with L. innocua a reduction of 1.3 log CFU/g was observed after 5 days of storage. The antibacterial results indicate that the presence of ZnOin PLA film is effective only for E. coli. The differences of the results obtained here with those reported in literature (where ZnO particles are reported to be very effective as antimicrobial material) are accounted for the different methodologies used. In conclusion considering the positive results, even if small, obtained here at least only for the E. Coli and considering that PLA/5% ZnO film shows, compared to plain PLA film, good tensile properties (especially Young’s modulus and stress at yielding) and good permeability (to O2 and CO2) induce to consider the PLA/5% ZnO composite film usable for food packaging when long shelf life and food safety are required, considering also that it is biodegradable and compostable.