Acid Films Research Articles

Influence of MgO and ZnO nanofillers on morphology, structural, thermal and mechanical properties of polylactic acid films

Influence of MgO and ZnO nanofillers on morphology, structural, thermal and mechanical properties of polylactic acid films

Biodegradable Poly(l-Lactic Acid) Films with Excellent Cycle Stability and High Dielectric Energy Storage Performance

Polymer-based film capacitors play key roles in numerous applications, such as converter/inverter systems in hybrid electric vehicles (HEVs), smart grids, and pulsed power sources. However, nearly all actively studied dielectric polymers are nondegradable. In this work, we prepare flexible biodegradable poly(l-lactic acid) (PLLA) films via a simple solvent casting method and achieve enhanced dielectric performances by polymer crystallization. The recoverable energy density (Urec) with charge–discharge efficiency (η) of 90% was improved from ∼2.9 J/cm3 for amorphous PLLA to ∼5.7 J/cm3 for the crystallized PLLA film at room temperature. Under 200 MV/m at 85 °C (the operation conditions of commercial biaxially oriented polypropylene-based capacitors in HEVs), Urec of 0.82 J/cm3 with η of 95% is achieved in the crystallized PLLA film, which is much higher than that of BOPP (below 0.5 J/cm3). In particular, the remarkable cyclic stability of the crystallized PLLA film is demonstrated by charge–discharge tests for 20 000 cycles at both room temperature and 85 °C under 200 MV/m. Moreover, the low C/(H+O) atom ratio helps metalized PLLA films exhibit a valuable self-healing ability after breakdown. With excellent recoverable energy density, high efficiency, good cyclic reliability, low-cost preparation method, self-healing ability, and eco-friendliness, the crystallized biodegradable PLLA film provides an eco-friendly and high-performance candidate to develop high-energy-storage capacitors.

Preparation and characterisation of biodegradable polylactic acid/ethyl cellulose film produced using the extruder and roller mixer machine

SummaryThe present study aimed to produce polylactic acid (PLA) and ethyl cellulose (EC) biodegradable film using a single screw extruder and a roller mixer machine. This method resulted in better mixing of the polymers, reducing the possibility of burns and easier control of the film thickness. The mechanical properties measurement showed that tensile strength (TS) decreased by about 37.9%, and elongation at break (EAB) increased about 2.6‐fold by increasing EC to 75%. The increase in EAB indicated the plasticising effect of EC. Since flexibility is essential in shaping a material without fracture, PLA/EC blend films can be a good candidate for packaging. According to DSC results, glass‐transition temperature (Tg) decreased in the blend films, probably due to the increase in the hydrophilicity of the films after EC addition. The water contact angle of pure PLA film was about 83°, whereas it reached 28° in the film containing 75% EC. The water vapour permeability of PLA film was 2.24 × 10−11 g m.s.Pa−1 and PLA reduction to 25% increased the WVP by about two times. Adding EC into the pure PLA film reduced the transparency, indicating the potential of blend film for the packaging of light‐sensitive food products. Besides, EC addition enhanced PLA biodegradability after enzymatic treatment (alcalase) and soil burial.

Design and fabrication of anthocyanin functionalized layered clay/poly(vinyl alcohol) coatings on poly(lactic acid) film for active food packaging

Biodegradable polymers (poly(lactic acid) (PLA), etc.) have been severely limited in their practical applications due to their inherent limitations in performance. Surface coating technology can effectively improve the active packaging function for food packaging. In this study, anthocyanin (ACY) functionalized layered double hydroxides (LDHs@ACY-Cu) was synthesized for the first time by adsorption and complexation of ACY with Cu(II) on the LDHs. Further, ACY (5 wt%)/poly(vinyl alcohol) (PVA) coatings as the first layer and LDHs@ACY-Cu (1–7 wt%)/PVA coatings as the second layer were successively coated on the PLA base film to fabricate active multilayer films. The results showed that ACY-Cu(II) complexes were loaded on the LDHs successfully with a thickness of 4 nm. With the increase of LDHs@ACY-Cu content, UV barrier, antioxidant, antibacterial and gas barrier properties of active multilayer films were improved significantly. When the addition of LDHs@ACY-Cu increased to 7 wt%, UV barrier (at 280 nm) and oxygen barrier properties of active multilayer films were increased by 44.9% and 99.1% compared with PLA base film, and the antibacterial and antioxidant properties also reached 96.4% and 82.21%, respectively. Although the color of all films showed a tendency to brown, the light transmittance exceeded 89.0% in the visible light range (at 600 nm). The milk spoilage test indicated that active multilayer films can inhibit the rapid bacterial reproduction in the pasteurized milk and extend the shelf life of milk. Therefore, active multilayer films exhibit good potential for applications in the field of active food packaging.

Electrospinning of gelatin/chitosan nanofibers incorporated with tannic acid and chitooligosaccharides on polylactic acid film: Characteristics and bioactivities

Electrospinning of gelatin/chitosan solutions incorporated with tannic acid (TA) and chitooligosaccharides (COS) at varying levels was performed on polylactic acid (PLA) films at a constant voltage of 20 kV with a feed rate of 0.5 mL/h. Nanofibers of gelatin/chitosan were incorporated with TA and COS as the sources of antioxidant and antimicrobial agents. SEM images revealed that the gelatin/chitosan nanofibers (GC-NF) had diverse morphologies and diameters. The concentration of TA and COS had prominent effect on the morphology of the nanofibers. Bead-free and smooth nanofibers were formed at higher TA and COS levels. PLA films coated with GC-NF showed high antioxidant activity, especially at higher levels of TA and COS incorporated. The films also exhibited antibacterial activity against both gram positive and gram negative bacteria. Selected GC-NF coated PLA films, having high antioxidant and antibacterial activities, were studied for mechanical and barrier properties. Water vapor permeability (WVP), tensile strength and elongation at break (EAB) of GC-NF coated PLA films were found to be improved when compared to PLA film. Moreover, light transmission of GC-NF coated PLA films was reduced and the films were cloudy in appearance. Characteristic peaks of functional groups in gelatin and chitosan were identified in the GC-NF coated PLA films using Fourier transform infrared (FTIR) spectroscopy. Overall, PLA film coated with GC-NF incorporated with TA and COS, could be a potential active packaging alternative for food applications. • Bead-free and smooth gelatin/chitosan nanofibers were electrospun on PLA film. • Nanofibers were incorporated with tannic acid and chitooligosaccharides. • PLA films coated with nanofibers had high antioxidant and antibacterial properties. • Mechanical properties of PLA film were enhanced by coating with nanofibers.

Capacitive label-free ultrasensitive detection of PSA on a covalently attached monoclonal anti-PSA antibody gold surface

• The design of an ultrasensitive label-free detection of prostate specific antigen (PSA) was achieved. • The fabricated immunosensor used monoclonal anti-PSA antibody as capture probe on an electrografted isophthalic thin fim. • Capacitance signals were deconvoluted from the impedance plots and were sensitive to PSA concentrations. • The detection of PSA could be achieved in fg.ml -1 . A rapid, low-cost, and accurate point-of-care analytical device for the determination of prostate-specific antigen (PSA) is required for the early diagnosis and prognosis of prostate cancer (PCa). In this work, an electrochemical capacitive immunosensor was developed for the label-free detection of PSA. The immunosensor was based on the covalent immobilization of monoclonal anti -PSA antibody via carbodiimide chemistry onto gold electrode pre-modified with a thin monolayer film of isophthalic acid (IPA). A methodology based on the steric hindrance of 1,3-substituted aryldiazonium salt was adopted to control the growth of the IPA thin film on the gold electrode. The non-specific binding sites were blocked with bovine serum albumin (BSA) to afford an AuE-IPA- anti -PSA-mAb|BSA immunosensor. The immunosensor was characterized by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The analytical performance of the developed sensor was evaluated using the capacitance Nyquist plots generated from the complex impedance data. In addition, complex capacitance was also calculated from the imaginary part of the impedance and plotted against the log of frequency. The double layer capacitance from the circuit fitting (R S C) was also used and compared the sensitive capacitance signals to the changes in PSA concentrations. The LOD values were in fg.mL -1 and distinguishable from the blank (PBS) for the Nyquist plots of capacitance, complex capacitance, and double layer capacitance signals. The developed immunosensor exhibited good stability, selectivity, low detection limits, and a wide linear range which was suitable for screening of prostate cancer using prostate-specific antigen.

The effect of alcoholic solutions on the thermomechanical properties of immersed poly(lactic acid) films

AbstractThe effects of aqueous and deuterium oxide (D2O) solutions of alcohols (methanol, ethanol, 1‐propanol, 2‐propanol, and 1‐butanol) on the thermomechanical properties of poly(lactic acid)—PLA—films were assessed by dynamic mechanical analysis. The glass transition temperature (Tg) of PLA films immersed in 25%, 50%, 75%, and 100% (v/v) alcoholic solutions were compared with the Tg of films immersed in 100% water and D2O. The Tg of PLA films immersed in methanol and ethanol aqueous solutions decreased as the concentration of the alcohol solutions increased. For methanol and ethanol, the Tg decreased by 8.6 and 7.6°C per 25% (v/v) increase in alcohol, respectively. When the PLA films were immersed in propanol aqueous solutions and butanol, the Tg reached the lowest value at 75% (v/v) and 100% (v/v), respectively. Tg of PLA films immersed in 1‐propanol and 2‐propanol decreased by 8.6 and 8.9°C for every 25% increase in propanol before reaching the minimum value, respectively. Aqueous and D2O solutions had similar effects on Tg. Selective studies of crystallinity evolution, ethanol sorption, degree of swelling, and Hansen solubility parameters of PLA were conducted. This work assists in developing PLA films intended for contact with aqueous‐alcoholic solutions.

Reduction and Photoreduction of NO2 in Humic Acid Films as a Source of HONO, ClNO, N2O, NO X , and Organic Nitrogen.

Atmospheric nitrous acid (HONO), a trace atmospheric gas, is often underestimated in global atmospheric models due to the poor understanding of its daytime sources and sinks. HONO is known to accumulate during nighttime and undergo rapid photodissociation during the day to form NO and highly reactive OH radical, making it important to have accurate atmospheric HONO estimations. Despite its rapid photolysis, recent field observations have found quasi-steady-state concentrations of HONO at midday, suggesting photolytic HONO formation pathways to replenish daytime atmospheric HONO. Recent studies suggest that the presence of complex organic photosensitizers in atmospheric aerosols converts atmospheric NO2 into HONO. To better understand the effect of environmental photosensitizers in daytime mechanisms of HONO formation, we present here laboratory studies on the heterogeneous photolytic reduction of NO2 by humic acid films, a proxy for organic chromophoric compounds. The effect of pH and Cl- in the photosensitized formation of HONO and other nitrogen-containing gases is also investigated. A dual Fourier transform infrared (FTIR) system is utilized to simultaneously perform in situ analysis of condensed-phase reactants and gas-phase products. We find that the rate of HONO formation is faster at lower pHs. Nitrogen incorporation in the complex organic chromophore is observed, suggesting a competing pathway that results in suppressed daytime formation of nitrogenous gases. Significantly, the presence of chloride ions also leads to the organic-mediated photolytic formation of nitrosyl chloride (ClNO), a known precursor of HONO. Overall, this work shows that organic acid photosensitizers can reduce adsorbed NO2 to form HONO, ClNO, and NO while simultaneously incorporating nitrogen into the organic chromophores present in aerosol.

Poly(lactic acid) films reinforced with hybrid zinc oxide‐polyhedral oligomeric silsesquioxane nanoparticles: Morphological, mechanical, and antibacterial properties

AbstractNanoparticles of zinc oxide (ZnO), polyhedral oligomeric silsesquioxane (POSS), and their hybrids were added to polylactic acid (PLA) using solution casting process at different weight percentages of the nanoparticles (1, 3, and 5 wt%) to form developed nanocomposites for food packaging applications. According to FTIR and XRD studies, both nanoparticles displayed fair chemical interactions with the PLA matrix. Furthermore, morphological investigations (SEM‐EDS) revealed that POSS, ZnO, and their hybrids were uniformly dispersed into the matrix despite some microaggregations at 5 wt% of nanoparticles, especially for those containing POSS. Moreover, adding 1 wt% of POSS to PLA increased its tensile strength and modulus by 20% and 149%, respectively, while decreasing the elongation‐at‐break by 54%. In addition, the tensile strength, tensile modulus, and elongation‐at‐break of PLA all increased by 7.5%, 28.7%, and 162%, respectively, with the addition of 1 wt% ZnO. Contact angle and surface free energy experiments demonstrated that after incorporating ZnO and POSS into the PLA matrix, the hydrophobicity of the samples increased, and POSS nanoparticles could minimize bacterial adherence effectively. In addition to the antibacterial properties of ZnO and POSS nanoparticles, increasing the concentration of hybrid nanoparticles up to 5 wt% expanded the bacteria's inhibitory zone, particularly in the case of Gram‐positive bacteria (Staphylococcus aureus). Finally, the hybrid nanocomposites exhibited both balanced mechanical characteristics and promising antibacterial activity compared with those with ZnO and POSS alone.

Polyvinyl alcohol/α-zirconium phosphate nanocomposite coatings via facile one-step coassembly

Polymer nanocomposites containing inorganic nanosheets have attracted high interest due to their improved stiffness and strength, enhanced barrier properties, and superior flame retardancy after properly incorporating nanosheets. α-Zirconium phosphate (Zr(HPO4)2) (ZrP) is a layered compound that can be well exfoliated into single-layer nanosheets by propylamine in an aqueous dispersion. A polyvinyl alcohol (PVA)/ZrP dispersion was prepared and coated on polylactic acid (PLA) films, followed with crosslinking by glutaraldehyde (GA). The morphological, optical, thermal, barrier, and mechanical properties of the PVA/ZrP nanocomposite coatings were investigated. The ZrP nanosheets were uniformly distributed and well oriented in the PVA matrix. The coated PLA films exhibited high clarity even when containing 20 wt % of ZrP nanosheets. The crosslinked coating layer containing 20 wt % of ZrP nanosheets (PVA/ZrP-20-C) had an oxygen permeability of 0.022 [10−16 cm3 (STP)cm/cm2•s•Pa] and water vapor permeability of 0.25 [10−11 g (STP)cm/cm2•s]. Compared with the neat PVA, when 20.0 wt % of ZrP nanosheets were well-aligned and properly incorporated, the Young's modulus and tensile strength of the resultant PLA nanocomposite were increased from 1.5 GPa and 29.5 MPa to 13.9 GPa and 98.3 MPa, respectively.

Highly efficiency flame-retardant and anti-dripping performance with dual effect of phosphaphenanthrene-benzimidazole for poly (lactic acid) film

To improve the flammability and severe melt-dripping behavior of poly (lactic acid) (PLA), we designed and successfully synthesized a flame retardant structure (D-AB) based on phosphaphenanthrene and benzimidazole groups with hydrogen bonds and π-π stacking effect. Then, D-AB was blended with PLA in solution to prepare PLA/D-ABs films. The results showed that the incorporation of D-AB significantly enhances the viscoelasticity and complex viscosity of PLA due to the synergistic effect of hydrogen bonds and π-π stacking of D-AB. Meanwhile, with the good char formation ability of benzimidazole group, PLA/D-ABs exhibit excellent flame retardancy. With only a 5 wt % addition of D-AB, the PLA film with 0.15 mm thickness easily achieve UL-94 VTM-0 rating and high LOI value of 30.5%, while its melt-dripping behavior is improved. In addition, the flame retardant mechanism of D-AB in PLA is studied in detail. It is found that the release of PO· radicals and non-combustible gas in the gas phase, as well as the formation of a dense and intact carbon layers in the condensed phase contribute to the good flame retardant performance of D-AB. This work provides a method for designing highly efficient flame retardants for PLA.

Synthesis of p-methoxybenzaldehyde/β-cyclodextrin inclusion complex and studies of its release properties in polylactic acid film

Synthesis of p-methoxybenzaldehyde/β-cyclodextrin inclusion complex and studies of its release properties in polylactic acid film

Seasonal Changes in Chemical Profile and Antioxidant Activity of Padina pavonica Extracts and Their Application in the Development of Bioactive Chitosan/PLA Bilayer Film

Seaweeds are a potentially sustainable source of natural antioxidants that can be used in the food industry and possibly for the development of new sustainable packaging materials with the ability to extend the shelf-life of foods and reduce oxidation. With this in mind, the seasonal variations in the chemical composition and antioxidant activity of brown seaweed (Padina pavonica) extracts were investigated. The highest total phenolic content (TPC) and antioxidant activity (measured by ferric reducing/antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, and oxygen radical absorbance capacity (ORAC)) were found for P. pavonica June extract. The TPC of 26.69 ± 1.86 mg gallic acid equivalent/g, FRAP of 352.82 ± 15.41 µmole Trolox equivalent (TE)/L, DPPH of 52.51 ± 2.81% inhibition, and ORAC of 76.45 ± 1.47 µmole TE/L were detected. Therefore, this extract was chosen for the development of bioactive PLA bilayer film, along with chitosan. Primary or quaternary chitosan was used as the first layer on polylactic acid (PLA) films. A suspension of chitosan particles with entrapped P. pavonica extract was used as the second layer. X-ray photoelectron spectroscopy confirmed the presence of layers on the material surface. The highest recorded antioxidant activity of the newly developed films was 63.82% inhibition. The developed functional films exhibited antifogging and antioxidant properties, showing the potential for application in the food industry.

Antioxidant poly (lactic acid) films with rice straw extract for food packaging applications

Antioxidant PLA films incorporating 2%, 4% and 6% of phenol-rich extract from rice straw (RS) were obtained by melt blending and compression-moulding. Aqueous RS extract was obtained by a combined ultrasound-reflux heating method and characterised as to its total phenolic content (TPC) and antioxidant capacity. The effect of the extract ratio on the functional properties of the films was analysed, as well as the release kinetics of antioxidants in food simulants (ethanol 10% and 50%). Extract incorporation slightly reduced the strength of the polymer matrix, stretchability, resistance to break, barrier capacity and thermostability, while films became brownish and gained antioxidant capacity. Phenolic compounds from the extract were effectively released into food simulants, depending on the extract concentration, the food simulant and contact time. The radical scavenging capacity of the films reached asymptotic values from about 150 h contact time, and films with 6% of the extract exhibited similar values for both simulants. So, PLA films with approximately 6% of extract could be used as biodegradable active packaging material with antioxidant capacity in both aqueous foods (simulant A) and more fatty products (simulant D1). Further studies are required to verify the antioxidant efficiency of the films in real foods.

Toward the Scalable Fabrication of Fully Bio-Based Antimicrobial and UVB-Blocking Transparent Polylactic Acid Films That Incorporate Natural Coatings and Nanopatterns.

Microbial transmissions via membrane surface and single-use plastic-induced pollution are two urgent societal problems. This research introduces a scalable fabrication strategy for fully biobased antibacterial and ultraviolet-B block polylactic acid (PLA) films integrating natural coatings and nanopatterns via ultrasonic atomization spray coating and thermal nanoimprinting lithography (TNIL) techniques, respectively. Tannic acid (TA) and gallic acid (GA) were formulated prior to TNIL using anode aluminum oxide template. Results reveal that TA and GA inks display intense adsorption in the UVB region. Plasma increases the hydrophilicity of PLA films for fast spreading of ink droplets. Micron-sized pillars observed on film confirm the successful structural replication. TA-coated PLA films display higher transparency than GA-coated ones. Nanopatterned PLA films have a modest antibacterial resistance of c. 45% against Escherichia coli. TA/GA coatings, however, impart PLA films with a bacterial reduction rate of over 80%. The integration of a TA or GA coating with nanopatterns further promotes the antibacterial rate up to 98%. The cytocompatibility of TA and GA demonstrates that the engineered film can potentially be applied as food packaging. Finally, a continuous mass production strategy is proposed along with an outline of the associated challenges and costs. This study provides a scalable strategy to the sustainable development of eco-benign and functional films.

Corrosion Properties of DLC Film in Weak Acid and Alkali Solutions

As an important joint material, tantalum (Ta) needs to be studied intensively in terms of wear and corrosion resistance. Two films of Ta/Ti/DLC (diamond-like carbon) (referred to as TD film) and Ta/Ti/TiN/Ti/DLC (referred to as TTTD film) were prepared by magnetron sputtering technology, and their electrochemical corrosion performance in lactic acid and sodium bicarbonate solutions was also investigated. The morphology observation, electrochemical corrosion experiment, and static contact angle measurement were carried out using a scanning electron microscope, electrochemical workstation, and a contact angle meter. This paper mainly discusses and analyzes the corrosion influencing factors and corrosion mechanisms of these two films under two different environments. The 20-day immersion experiments show that the TD film in both solutions results in severe surface corrosion due to its loose structure and many internal defects. In contrast, the surface of the TTTD film with a dense structure, a multilayer structure, and a thicker thickness is not corroded under the same conditions. The electrochemical corrosion experiments show that the corrosion resistance of the TD film is worse than that of the Ta substrate, while the TTTD film has the strongest corrosion resistance, improving the corrosion resistance of the Ta substrate. Although the TD film had a higher sp3 content than the TTTD film, it does not provide protection to the Ta substrate due to increased structural defects in the TD film. The results of the contact angle show that the contact angle of the TTTD film is smaller than that of the TD film in both solutions. However, the TTTD film has the lowest roughness and the densest structure, and thus the TTTD film is more resistant to corrosion. It is finally concluded that the surface morphology and internal structure of the films are the main factors affecting corrosion resistance. This provides an important reference for the application of DLC film in weak alkaline and weak acid environments.

Caddisfly Larvae are a Driver of Plastic Litter Breakdown and Microplastic Formation in Freshwater Environments.

Plastic litter is now pervasive in the aquatic environment. Several marine and terrestrial organisms can fragment plastic with their feeding appendages, facilitating its breakdown and generating microplastics. However, similar studies with freshwater organisms are extremely limited. We explored the interactions between the caddisfly larvae Agrypnia sp. and polylactic acid (PLA) film. The use of plastic by larvae to build their protective cases was investigated, along with their ability to fragment the plastic film as they do with leaf litter. Caddisfly consistently incorporated PLA into their cases alongside leaf material. They also used their feeding appendages to rapidly fragment PLA-forming hundreds of submillimeter-sized microplastics. Although larvae showed a preference for leaf material when constructing cases, plastic use and fragmentation still occurred when leaf material was replete, indicating that this behavior is likely to occur in natural environments that are polluted with plastics. This is thought to be the first documented evidence of active plastic modification by a freshwater invertebrate and therefore reveals a previously unidentified mechanism of plastic fragmentation and microplastic formation in freshwater. Further work is now needed to determine the extent of this behavior across freshwater taxa and the potential implications for the wider ecosystem. Environ Toxicol Chem 2022;41:3058-3069. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Bacterial Response to the Surface Aging of PLA Matrices Loaded with Active Compounds.

The use of active components in biomaterials improves the properties of existing ones and makes it possible to obtain new devices with antibacterial properties that prevent infections after implantation, thus guaranteeing the success of the implant. In this work, cetyltrimethylammonium bromide (CTAB) and magnesium particles were incorporated into polylactic acid (PLA) films to assess the extent to which progressive aging of the new surfaces resists bacterial colonization processes. For this purpose, the films' surface was characterized by contact angle measurements, ToF-SIMS and AFM, and adhesion, viability and biofilm growth of Staphylococcus epidermidis bacteria on these films were also evaluated. The results show that the inclusion of Mg and CTAB in PLA films changes their surface properties both before and after aging and also modifies bacterial adhesion on the polymer. Complete bactericidal activity is exhibited on non-degraded films and films with CTAB. This antibacterial behavior is maintained after degradation for three months in the case of films containing a higher amount of CTAB.

CO2 laser perforated biodegradable films for modified atmosphere packaging of baby corn

Microperforated polylactic acid (PLA) and polybutylene succinate (PBS) films were fabricated using a CO2 laser under various pulse fluences from 37.0 to 369.8 J/cm2, corresponding to pulse durations of 20–200 μs. A hole was formed at perforation thresholds of 147.9 J/cm2 for PLA and 129.4 J/cm2 for PBS films. The area and diameter of the microhole and volume losses increased with rising laser fluence. Microperforated PLA and PBS films showed similar mechanical properties of tensile strength, Young's modulus and elongation at break to films without microholes but significant improvements in oxygen transmission rate (OTR) and carbon dioxide transmission rate (CO2TR) over non-perforated films. OTR and CO2TR through a single microhole with area of ∼20,000 μm2 on PLA were 234 ± 58 and 217 ± 57 cm3/d, respectively while OTR and CO2TR though a single microhole on PBS were 205 ± 12 and 144 ± 40 cm3/d, respectively showing that biodegradable film could achieve very high OTR at up to 77,500 cm3/m2.d. Baby corn (100g) was packed in microperforated bags. Equilibrium modified atmosphere conditions of 10%–17%O2 and 4%–7% CO2 were reached in performed film packages with very high OTR and CO2TR of 35,000–77,500 and 36,500–80,000 cm3/m2.d, respectively. Results suggested that baby corn maintained freshness qualities for more than 7 days at a storage temperature of 15 °C. The CO2 laser perforation process was successful in producing modified atmosphere packaging (MAP) with tailored gas transmission rates.

Carbon quantum dots-driven surface morphology transformation towards superhydrophobic poly(lactic acid) film

Focused on the design and implementation of superhydrophobic surface of poly(lactic acid) (PLA) film, the novel morphology regulating strategy (i.e., carbon quantum dots (CQDs)-nucleated interfacial-crystallization induced phase separation) is reported to fabricate CQDs-grafted-poly(D-lactic acid)/poly(L-lactic acid) (CQDs-g-PDLA/PLLA) films with tailorable hierarchical micro-nano structures. The hierarchical structures of CQDs-g-PDLA/PLLA films evolve from laminar protrusions to microspheres to petal-like structures and further to micro-nano sphere structures, only by adjusting the CQDs-g-PDLA content. 30 wt% CQDs-g-PDLA/PLLA film with lotus leaf-like microstructures exhibits a record-high contact angle of 168° and a rather small sliding angle of 7.8°, indicating the pretty superhydrophobicity. Constructing controllable hierarchical structures is key factor to attain the superhydrophobicity, instead of commonly introducing suitable nanoparticles or hydrophobization agents. In combination with the high porosity, 30 wt% CQDs-g-PDLA/PLLA film illustrates a maximal oil-absorption up to 9.7 g/g. This strategy provides a novel insight into designing and constructing superhydrophobic PLA materials for the enormous application potential in surface self-cleaning and oil-water separation.