Development of antimicrobial PCL/nanoclay nanocomposite films with enhanced mechanical and water vapor barrier properties for packaging applications

Modified cellulose nanocrystals enhanced polycaprolactone multifunctional films with barrier, UV-blocking and antimicrobial properties for food packaging

The packaging industry demands improved eco-friendly materials with new and enhanced properties. In this context, bio-nanocomposite films with antimicrobial and UV-shielding properties based on modified cellulose nanocrystals/polycaprolactone (MCNC/PCL) were fabricated via solution casting method, and then food packaging simulation was carried out. CNCs were obtained by acid hydrolysis followed by successful functionalization with Quaternary ammonium surfactant, confirmed by FTIR, XPS, XRD, TEM, and DLS analyses. Furthermore, the morphological, physical, antibacterial, and food packaging properties of all prepared films were investigated. Results showed that the mechanical, UV blocking, barrier properties, and antibacterial activity of all composite films were remarkably improved. Particularly, the addition of 3 wt% MCNC increased the tensile strength and elongation at break by 27.5 % and 20.0 %, respectively. Moreover, the permeability of O2, CO2, and water vapor dramatically reduced by 97.6 %, 96.7 %, and 49.8% compared to the Neat PCL. Further, the UV-blocking properties of the composite films were significantly improved. The antimicrobial properties of MCNC/PCL films showed good antimicrobial properties against S. aureus. Finally, cherry packaged with 1 and 3 wt% MCNC films exhibited satisfactory freshness after 22 days of preservation. Overall, the fabricated PCL nanocomposite films can be utilized in the food packaging industry.

Tuning the physiochemical properties of polycaprolactone-hydroxyapatite composite films by gamma irradiation for biomedical applications

Physiochemical properties of polycaprolactone-hydroxyapatite (PCL-HAp) composites were investigated in the pristine and after irradiation of γ rays (25, 50, 75, and 100 kGy). PCL-HAp composites were synthesized by solvent evaporation and characterized using spectroscopic methods as well as biological assays. The surface roughness (RMS) of the irradiated composite film (at 75 kGy) was 80 times higher than that of the pristine. Irradiation tailors the contact angle of the films from 77° to 90° (at 100 kGy). A decrease in particle size (at 100 kGy) of HAp nanorods in PCL-HAp composites film was observed. The XRD peak of PCL was slightly shifted from 21.2° to 21.7° (at 100 kGy) with the decrease in crystallite size. The peak intensity of the PCL and HAp altered on irradiation that was confirmed by FTIR and Raman analysis. Further, the bandgap of the irradiated film was lowered by 13 % (at 25 kGy). The luminescence intensity decreased due to the non-radiative process induced by the irradiation defects. All the samples possess hemocompatibility percentage of <10 % as per ASTM standards. At 75 kGy, fibroblast cell proliferation was higher than the pristine and other doses. The gamma-irradiated PCL-HAp composite films are potential candidates for tissue engineering applications.

Organomodified nanoclay with boron compounds is improving structural and antibacterial properties of nanofibrous matrices

In this study, nanofibrous polymeric matrices were successfully developed with nanoclay, montmorillonite (MMT) and various boron (B) compounds, which were known to have positive effects on the wound healing with elevated antibacterial properties. For this purpose, MMT was modified with quaternary ammonium salt, trimethyl octadecyl ammonium bromide (TMOD), and boron compounds, boron nitride (BN), zinc borate (ZB), or phenylboronic acid (PBA) were adsorbed on organomodified MMT (OMMT). Then, poly (lactic acid) (PLA) based nanofibrous PLA-OMMT/B composites were fabricated via electrospinning. Modification of MMT nanoparticles with TMOD occurred through ion-exchange reaction and led to better homogenous fibrous structures which exhibited dramatic inhibition for gram-positive bacteria. Moreover, composites with ZB and PBA demonstrated both bacteriostatic and bactericidal effects for gram-positive and gram-negative bacteria. The chemical structures of the matrices were evaluated through ATR-FTIR and supported the intercalated composite formation. The thermal and mechanical stabilities of PLA matrices were also enhanced after OMMT and B incorporation. The lowest breaking strain value was recorded for PLA-OMMT/PBA composite compared to other B composites. The 100% and 50% extracts of the PLA-OMMT matrices showed modest cytotoxic effect on the human dermal fibroblasts (NHDF) on the second day culture that probably originated from TMOD. These results demonstrated that PLA-OMMT/B matrices, especially PBA including matrices, can be used as replaceable wound dressings that have limited interaction with cells but exhibit antibacterial activity and support the early stages of wound healing both morphologically and chemically.

Investigations of Fused Deposition Modeling for Perovskite Active Solar Cells

The advent of Fused Deposition Modeling (FDM; or 3D printing) has significantly changed the way many products are designed and built. It has even opened opportunities to fabricate new products on-site and on-demand. In addition, parallel efforts that introduce new materials into the FDM process have seen great advances as well. New additives have been demonstrably utilized to achieve thermal, electrical, and structural property improvements. This combination of fabrication flexibility and material additives make FDM an ideal candidate for investigation of perovskite materials in new solar cell efforts. In this work, we fabricate and characterize a perovskite-based solar cell polymer designed for the FDM fabrication processes. Perovskite solar cells have garnered major research interest since their discovery in 2009. Perovskites, specifically methylammonium lead iodide, offer beneficial properties to solar cell fabrication such as long minority charge carrier distance, high light absorption, and simple fabrication methods. Despite the great potential of these materials, however, stability remains an issue in solar cell utilization as the material degrades under ultraviolet light, exposure to oxygen and water, as well as increased temperatures. To mitigate degradation, different fabrication methods have been utilized. Additionally, multiple groups have utilized encapsulation methods post-fabrication and in situ solution processed integration of polymer materials into the solar cell to prevent degradation. In this paper, we leverage the unique ability of FDM to encapsulate perovskite materials and yield a MAPbI₃-PCL solar material as the active layer for solar cell use. In this manner, increased ability to resist UV light degradation and material stability from other environmental factors can be achieved. This study provides characterization of the material via multiple techniques like SEM (Scanning Electron Microscopy) and XRD (X-ray Diffraction) as well as absorbance, transmittance, and photocurrent response. Investigations of processing on perovskite degradation as well as initial solar simulated response are recorded. Unique aspects of the resulting material and process are noted including improved performance with increased operating temperature. Increased electron–hole pair generation is observed for 200 μm FDM-printed PCL film, achieving a 45% reduction in resistance under peak incident flux of 590 W/m2 with the addition of MAPbl₃. This work establishes insight into the use of FDM for full solar cell fabrication and points to the next steps of research and development in this growing field.

Biodegradable blend films of poly(ε-caprolactone)/poly(propylene carbonate) for shelf life extension of whole white button mushrooms

Blend films with poly(ε-caprolactone)(PCL) and poly(propylene carbonate)(PPC)with thickness of approximately 40 μm and 60 μm, respectively, were prepared using a uniaxial-stretching extrusion process to modify the property of PCL. PCL/PPC blend films with better comprehensive properties with thickness about 60 μm were used for equilibrium-modified atmosphere packaging of button mushrooms at 5 °C. The gas barrier property together with water vapor permeability were evaluated as well as its effects on the shelf life button mushrooms. The results showed that the PCL/PPC20 and PCL/PPC50 blend films have suitable gas barrier property and water vapor permeability, which was helpful to generate an appropriate storage environment and more importantly no condensation occurred in these two packages. The lower weight loss of button mushrooms was observed for PCL/PPC20 and PCL/PPC50 blend films 4.43 and 4.46, respectively. The PCL/PPC blend films was more effective in decreasing the activity of PPO and preserving the color of the button mushrooms. The over market acceptability of button mushrooms packaged in PCL/PPC blend films still maintained good and within the limit of marketability after 17 days of storage.

Viscoelastic, Thermal, and Mechanical Properties of Melt-Processed Poly (ε-Caprolactone) (PCL)/Hydroxyapatite (HAP) Composites

Poly (ε-caprolactone) (PCL)/hydroxyapatite (HAP) composites represent a novel material with desired properties for various applications. In this work, PCL/HAP composites at low loadings were developed through melt-extrusion processing. The effects of HAP loading on viscoelastic, thermal, structural, and mechanical properties of PCL were examined. The morphological analysis revealed better dispersion of HAP at low loadings, while aggregation was noticed at high concentrations. The complex viscosity of the prepared composites increased with increasing concentration of HAP. In addition, a significant decrease in crystallinity was observed upon increase in HAP loading. However, the elongation at break increased with increasing the concentration of HAP, probably due to a decrease in crystallinity. The onset thermal degradation temperature of PCL was enhanced at low concentrations of HAP, whereas a decrease was observed at high loading. Overall, different degrees of HAP dispersion resulted into specific property improvement.

Development of Novel Thin Polycaprolactone (PCL)/Clay Nanocomposite Films with Antimicrobial Activity Promoted by the Study of Mechanical, Thermal, and Surface Properties

Infection with pathogenic microorganisms is of great concern in many areas, especially in healthcare, but also in food packaging and storage, or in water purification systems. Antimicrobial polymer nanocomposites have gained great popularity in these areas. Therefore, this study focused on new approaches to develop thin antimicrobial films based on biodegradable polycaprolactone (PCL) with clay mineral natural vermiculite as a carrier for antimicrobial compounds, where the active organic antimicrobial component is antifungal ciclopirox olamine (CPX). For possible synergistic effects, a sample in combination with the inorganic antimicrobial active ingredient zinc oxide was also prepared. The structures of all the prepared samples were studied by X-ray diffraction, FTIR analysis and, predominantly, by SEM. The very different structure properties of the prepared nanofillers had a fundamental influence on the final structural arrangement of thin PCL nanocomposite films as well as on their mechanical, thermal, and surface properties. As sample PCL/ZnOVER_CPX possessed the best results for antimicrobial activity against examined microbial strains, the synergic effect of CPX and ZnO combination on antimicrobial activity was proved, but on the other hand, its mechanical resistance was the lowest.

Nanotechnology application in food packaging: A plethora of opportunities versus pending risks assessment and public concerns

Environmental factors, oxidation and microorganisms contamination, are the major causes for food spoilage, which leads to sensory features alteration, loss of quality, production of harmful chemicals and growth of foodborne pathogens capable to cause severe illness. Synthetic preservatives, traditional conserving methods and food packaging (FP), although effective in counteracting food spoilage, do not allow the real-time monitoring of food quality during storage and transportation and assent a relatively short shelf life. In addition, FP may protect food by the spoilage caused by external contaminations, but is ineffective against foodborne microorganisms. FP preservative functionalities could be improved adding edible natural antioxidants and antimicrobials, but such chemicals are easily degradable. Nowadays, thanks to nanotechnology techniques, it is possible to improve the FP performances, formulating and inserting more stable antioxidant/antimicrobial ingredients, improving mechanical properties and introducing intelligent functions. The state-of-the-art in the field of nanomaterial-based improved FP, the advantages that might derive from their extensive introduction on the market and the main concerns associated to the possible migration and toxicity of nanomaterials, frequently neglected in existing reviews, have been herein discussed.

Behaviours of poly(ε-caprolactone)/silver-montmorillonite nanocomposite in membrane ultrafiltration for wastewater treatment

The scope of this work consists in studying the possibility of using the long-lasting antimicrobial poly(ε-caprolactone)/silver-montmorillonite (PCL/Ag-MMT) materials which we have developed in our previous research, as new class of nanocomposite membranes, finding their application in the wastewater treatment. The surface properties of these hybrid membranes were investigated by scanning electron microscopy (SEM) analysis and contact angle measurements. The SEM results showed that the synthesized membranes exhibited homogeneous sponge microstructures. It was found that the gradual inclusion of nanoparticles (2, 3 and 5 wt. %) into PCL matrix induced a remarkable increase of the membrane thickness. Moreover, these hybrid materials exhibited an enhancement of the surface hydrophilicity attributed to the hydrophilic nature of clay incorporated. The water contact angle of the PCL membrane surface noticeably decreased after the Ag-MMT addition: dropping from 82.60° for PCL 0%Ag-MMT to 64.28° for PCL 5%Ag-MMT membrane. The antimicrobial properties of the membranes were confirmed using Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) as the model bacteria. Quality parameters including total suspended solids (TSS), electric conductivity (EC), nitrates, chlorides, bicarbonates, heavy metals and other trace elements, were determined before and after treatment of real wastewater. A decrease of nitrates by 15.12%, a diminution of sulphates by 45.61% and a removal of 41.38%, 53.57% and61.11% for heavy metals Pb, Zn and Cd respectively indicating clearly that the ultrafiltration process using PCL/AgMMT nanocomposite membranes is an effective way to eliminate the wastewater effluents.

Effects of Immobilized Ionic Liquid on Properties of Biodegradable Polycaprolactone/LDH Nanocomposites Prepared by In Situ Polymerization and Melt-Blending Techniques

The high capacity of calcinated layered double hydroxides (LDH) to immobilize various active molecules together with their inherent gas/vapor impermeability make these nanoparticles highly promising to be applied as nanofillers for biodegradable polyester packaging. Herein, trihexyl(tetradecyl)phosphonium decanoate ionic liquid (IL) was immobilized on the surface of calcinated LDH. Thus, the synthesized nanoparticles were used for the preparation of polycaprolactone (PCL)/LDH nanocomposites. Two different methods of nanocomposite preparation were used and compared: microwave-assisted in situ ring opening polymerization (ROP) of ε-caprolactone (εCL) and melt-blending. The in situ ROP of εCL in the presence of LDH nanoparticles with the immobilized IL led to homogenous nanofiller dispersion in the PCL matrix promoting formation of large PCL crystallites, which resulted in the improved mechanical, thermal and gas/water vapor barrier properties of the final nanocomposite. The surface-bonded IL thus acted as nanofiller surfactant, compatibilizer, as well as thermal stabilizer of the PCL/LDH nanocomposites. Contrary to that, the melt-blending caused a partial degradation of the immobilized IL and led to the production of PCL nanocomposites with a heterogenous nanofiller dispersion having inferior mechanical and gas/water vapor barrier properties.

Biodegradable Poly(ε-Caprolactone) Active Films Loaded with MSU-X Mesoporous Silica for the Release of α-Tocopherol

In this study, new active PCL (poly(ε-caprolactone)) films containing α-tocopherol (TOC) and MSU-X mesoporous silica were prepared by melt blending. The studied additives were directly incorporated into the polymer matrix or by impregnating TOC into MSU-X silica (PCL-IMP). Thermal, optical, oxygen and water barrier properties as well as oxidation onset parameters, were studied. Films containing MSU-X and/or TOC showed a significant increase in oxidative onset temperature (OOT) and oxidative induction time (OIT), improving thermal stability against materials oxidation by the addition of mesoporous silica and TOC into the polymer matrix. In addition, the effect of MSU-X addition on the migration behaviour of α-tocopherol from active films was investigated at 40 °C using 50% (v/v) ethanol as fatty food simulant, showing PCL-IMP films the lower release content and diffusion coefficient (3.5 × 10⁻¹⁵ cm² s⁻¹). Moreover, radical scavenging (DPPH and ABTS) and antibacterial activity against E. coli and S. aureus were favoured by the release of α-tocopherol in the developed films. The obtained results have demonstrated the potential of the new PCL-based active formulations for TOC controlled release in antioxidant and antibacterial food packaging applications.

A Review of the Synthesis and Applications of Polymer–Nanoclay Composites

Recent advancements in material technologies have promoted the development of various preparation strategies and applications of novel polymer–nanoclay composites. Innovative synthesis pathways have resulted in novel polymer–nanoclay composites with improved properties, which have been successfully incorporated in diverse fields such as aerospace, automobile, construction, petroleum, biomedical and wastewater treatment. These composites are recognized as promising advanced materials due to their superior properties, such as enhanced density, strength, relatively large surface areas, high elastic modulus, flame retardancy, and thermomechanical/optoelectronic/magnetic properties. The primary focus of this review is to deliver an up-to-date overview of polymer–nanoclay composites along with their synthesis routes and applications. The discussion highlights potential future directions for this emerging field of research.

K R. Antimicrobial, antibiofilm, and microbial barrier properties of poly (ε-caprolactone)/cloisite 30B thin films

Development of antibacterial and antibiofilm surfaces is in high demand. In this study, nanocomposite of Poly (ε-caprolactone)/Cloisite 30B was prepared by the solvent casting method. The membranes were characterised by SEM, AFM, and FTIR. Evaluation of water uptake, antimicrobial, antibiofilm, and microbial barrier properties demonstrated a significant antimicrobial and antibiofilm activity against MTCC strain of Staphylococcus haemolyticus and strong biofilm positive Staphylococcus epidermidis of clinical origin at low clay concentrations. These membranes acted as an excellent barrier to the penetration of microorganism. These nanocomposites can have promising applications in various fields including packaging.

Controlled biodegradation of polymers using nanoparticles and its application

Controlled biodegradation mechanism has been revealed using different nanoparticles which eventually regulate pH of media.