Preparation and antimicrobial properties of LDPE composite films melt-blended with polymerized urushiol powders (YPUOH) for packaging applications

Polymerized solid-type urushiol (YPUOH) with high thermal stability and excellent antimicrobial properties was prepared and incorporated into low-density polyethylene (LDPE) via melt-compounding and subsequent melt-extrusion processes. To investigate the feasibility of as-prepared LDPE/YPUOH composite films for use in packaging applications, the films were characterized as a function of YPUOH using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (WAXD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), contact angle, and antimicrobial activity assays. The physical properties and antimicrobial activities were found to be strongly dependent upon the changes in chemical and morphological structures originating from different compositions of the composite films. The thermal stability of the composite films was effectively improved with YPUOH addition. Incorporating YPUOH caused the water vapor transmission rate (WVTR) to decrease from 10.3 to 6.5 g/m²·day, suggesting that the barrier properties of LDPE, which are relatively good per se, were further improved. Furthermore, the LDPE/YPUOH composite films exhibited good antimicrobial activities against both Gram-negative and Gram-positive micro-organisms. However, the dispersion of YPUOH in the LDPE matrix was not satisfactory due to a weak interaction between LDPE and YPUOH, which may adversely affect the thermal and barrier properties at higher contents of YPUOH. Further studies are required to increase the compatibility and dispersion of YPUOH in the LDPE matrix in order to optimize its performance and expand its applications.     

LDPE composite films incorporating ceramic powder emitting far‐infrared radiation for advanced food‐packaging applications

A ceramic powder that emits far‐infrared radiation (FIR) was incorporated into low‐density polyethylene (LDPE) via melt‐compounding and subsequent melt‐extrusion processes. To investigate the feasibility of as‐prepared LDPE/FIR composite films for use in packaging applications, the composite films were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, FIR emissivity and emissive power, antimicrobial activity assays, and storage tests. The physical properties and antimicrobial activities of the composite films were found to strongly correlate with the changes in the chemical and morphological structures that originate from different contents of FIR ceramic powder. A higher content of FIR ceramic powder in the LDPE/FIR composite film provided increased FIR emissivity and emission power of the composite and resulted in good antimicrobial activity. Storage tests also showed that incorporation of FIR ceramic powder into LDPE film was an effective method for maintaining the freshness of lettuce. Furthermore, the incorporation of FIR ceramic powder into LDPE films induced higher thermal stability and crystallinity and enhanced their barrier properties, which suggest these LDPE/FIR composite films are potential candidates for advanced packaging materials for the food and medical industries. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43102.     

Nanocomposite polymer films containing carvacrol for antimicrobial active packaging

Nanocomposite films based on low‐density polyethylene (LDPE) containing carvacrol were prepared and characterized with the aim to get antimicrobial active packaging. Organo‐modified montmorillonite (MMT) was used as filler. The weak interaction between LDPE and clay led to the formation of intercalated systems. On the other hand, strong interaction between carvacrol and organosilicate allowed a good dispersion of the oil into the clay galleries, promoting the swelling of MMT stacks and a higher polymer/clay interface. As a result, carvacrol was protected against thermal degradation and its release from the films was efficiently delayed. Moreover, outstanding thermal oxidative stability as well as improved oxygen barrier properties were detected in the nanocomposite containing carvacrol. The presence of clay and carvacrol also increased LDPE crystallinity, due to an enhanced nucleation activity, while the mechanical properties of the films were slightly affected. The antimicrobial properties of carvacrol containing films were tested, showing a significant activity against several bacterial strains, which is preserved in presence of the clay. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Development of low density polyethylene nanocomposites films for packaging

Requirements for adequate permeability of polymeric materials to gases and vapors, good barrier and mechanical properties of polymers have boosted interest in developing new strategies to improve these properties. Research and development in polymeric materials coupled with appropriate filler, matrix-filler interaction and new formulation strategies to develop composites have potential applications in various types of packaging (agricultural produce, dried food, frozen food etc.). In this study, LDPE composites containing various types of fillers (zeolite TMAZ 7, nanoclay Cloisite 20A and precipitated calcium carbonate, CaCO₃) were prepared using extrusion/injection molding. The microstructural and morphological changes as well as mechanical features of samples were characterized by scanning electronic microscopy and by tensile tests. The thermal degradation of LDPE composites was studied using thermogravimetric analysis. Barrier properties (permeability, the diffusion and the solubility constant) in modified LDPE samples were determined. It is found that used minor clay concentration is already very effective for achievement of good morphology. In the presence of nanoparticles, at lower content, the value of oxygen permeability of LDPE decreases. Also, the results have revealed that the samples containing fillers have increased thermal stability in comparison to pure LDPE.     

Carboxymethyl cellulose-based nanocomposites reinforced with montmorillonite and ε-poly-l-lysine for antimicrobial active food packaging

Traditional packaging materials with single function or weak activity cannot meet the requirements of active packaging. In this study, antimicrobial carboxymethyl cellulose (CMC)-based nanocomposites containing montmorillonite (MMT) and ε-poly-(l -lysine) (ε-PL) were prepared by solution casting method. The morphological, optical, mechanical, barrier, thermal, and antimicrobial properties of the resulted ternary nanocomposites were investigated. The surface morphology of the films was dependent on the contents of the ε-PL used. The incorporation of MMT and ε-PL into CMC matrix improved the UV barrier property, tensile strength, hydrophobicity, and water vapor barrier property. When incorporation of 7.5 wt % ε-PL, the tensile strength increased more than threefold and the water vapor permeability decreased by about 35% compared with pure CMC film, the water contact angle reached up to the highest value of 65.38°. The ε-PL incorporated CMC/MMT films exhibited good antimicrobial activities against Gram-positive (Staphylococus aureus) and Gram-negative (Escherichia coli) bacteria and fungi (Botrytis cinerea and Rhizopus oligosporus). Microbial growth inhibition rate of above 90% was obtained when the content of ε-PL got up to 7.5 wt %. In addition, CMC/MMT/ε-PL7.5 wt % film-forming solution having the appropriate properties was used as coating for the strawberries preservation, the shelf life of strawberries was extended for 2 days. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48782.     

Bioactive efficacy of low‐density polyethylene films with natural additives

Active packaging can be defined as packaging that includes additives that help to extend the shelf life of food; among the advantages of its use is the possibility to reduce the amount of additives added to the food during processing. The aim of this study was to develop, characterize, and apply active films of low‐density polyethylene, incorporating carotenoid and yerba mate extracts as active additives. Active films were obtained by extrusion and were characterized for water vapor permeability, thickness, color, and mechanical and thermal properties. The effectiveness of the films was evaluated using butter packed in the formulated films. There was a significant reduction in thickness, and mechanical, thermal, and water vapor barrier parameters of the films compared to the control. The concentration of additives directly influenced coloration and antioxidant and antimicrobial action of the films. The formulated films provided protection against oxidative action and inhibition of microbial growth. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46461.     

Monitoring food quality - effect of curcumin in the development of polyethylene/thermoplastic starch based smart packaging

Smart packaging relies on the one-to-one interaction of food with its packaging or its environment to monitor food quality and safety. Colorimetric pH indicators (synthetic, natural) working in a smart food packaging system are particularly striking when used with fresh foodstuffs such as fish and meat that perish quickly and require real-time freshness monitoring. In this study, curcumin (Cur) was used as a natural pH indicator to produce sustainable smart packaging material. Towards this objective, low-density polyethylene (LDPE) and thermoplastic starch (TPS) blend-based films containing Cur were prepared using a twin screw extrusion and hot-pressing processes. Besides, two different compositions of LDPE/TPS mixture (50/50 and 70/30) were used as the matrix. Thermal, mechanical, morphological properties, an affinity for water, and color change properties of LDPE/TPS/Cur films were investigated. They showed a significant color change from yellow to brown at pH: 10 at the end of the seventh day, especially in the 50 LDPE/50 TPS mixture. 50 LDPE/50 TPS mixture with 7% curcumin content gave the highest tensile strength of 8.03 Mpa. When the same mixture was used to monitor chicken meat spoilage at 25°C, meat samples have shown color changes from light yellow to light brown due to the increased content of total volatile basic amines. As a result, it has been suggested that 50 LDPE/50 TPS mixture containing 7% Cur can be used as a smart packaging material.     

LDPE/clay/carvacrol nanocomposites with prolonged antimicrobial activity

Over the past decade there is an immense effort to develop antimicrobial packaging systems, which incorporates natural biopreservatives, such as essential oils (EOs). The highly volatile nature of EOs, which is advantageous for their efficient diffusion and mode of action, presents a major obstacle for their incorporation with polyolefins via conventional high‐temperature melt compounding and processing. This study presents a new approach to use organo‐modified montmorillonite (MMT) clays, as active carriers for carvacrol (used as a model EO), aiming to minimize its loss throughout the polymer compounding. Different MMT clays are pretreated with carvacrol, resulting in the oil molecules intercalation in between the clay galleries and enhanced carvacrol thermal stability. These hybrids are incorporated within low‐density polyethylene (LDPE) and the resulting films are characterized in terms of their nanostructure, thermal properties, and antimicrobial activity. The LDPE/(clay/carvacrol) nanocomposites exhibit excellent and prolonged antimicrobial activity against E. coli bacteria, while LDPE/carvacrol films loss their antimicrobial functions within several days. The superior antimicrobial behavior is ascribed to the significantly higher carvacrol content and its enhanced thermal stability within the films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41261.     

Application of paraffin and silver coated titania nanoparticles in polyethylene nanocomposite food packaging films

In this work, 3% and 5% TiO₂/Ag nanoparticles were dispersed in low‐density polyethylene through melt blending process, and subsequently nanocomposite films were prepared by hot pressing. Paraffin was used for the first time in this work as compatibilizer agent. The effect of TiO₂/Ag nanoparticle content, as well as compatibilizer dosage on the antimicrobial, morphological, mechanical, and optical performance of the nanocomposite films was investigated. Improved mechanical properties of the nanocomposite films were found on using paraffin as compatibilizer in comparison with the neat low‐density polyethylene (LDPE) films. The optical study results also showed that the addition of TiO₂/Ag to the LDPE films does not drastically change the film appearance other than making them more reddish. The fabricated nanocomposites presented in this study could be a suitable choice for food packaging (subject to further investigation of the food packaging behavior). The results showed that both TiO₂/Ag nanoparticle and compatibilizer are needed to prevent the bacteria growth in the film. The best result was obtained by using 5% nanoparticle and 4% paraffin compatibilizer where the bacteria growth rate was significantly reduced by 95%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45913.     

Effect of starch on thermal,mechanical, and barrier properties of low density polyethylene film

Low‐density polyethylene (LDPE) with different quantities of starch was compounded using a twin screw extruder and blown into films by a Konar K, blow‐film machine. Mechanical properties, namely percent elongation, tensile, bursting, and tear strength, as well as barrier properties, such as water vapor and oxygen transmission rate, of the filled LDPE film were studied. Thermal properties of the films were studied using DSC and DMA. Master curves at reference temperature of 30°C were obtained using software linked to DMA. Incorporation of 1% starch in LDPE has marginally affected the thermal, barrier, and mechanical properties; however, that of 5% starch filled LDPE has affected the properties to a great extent. The mechanical properties, such as percent elongation, tensile, tear, bursting, and seal strength, decreased by 19.2, 33.6, 3.60, 10.8, and 22.12%, respectively. Similarly, water vapor and oxygen transmission rate increased to 32.5 and 18.3%, respectively. Other physical properties, namely migration and thermal properties, were also affected in 5% starch filled LDPE; however, the film can still be used as packaging material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3355–3364, 2006     

Behavior of α‐ and β‐cyclodextrin‐encapsulated allyl isothiocyanate as slow‐release additives in polylactide‐co‐polycaprolactone films

The natural antibacterial agent allyl isothiocyanate (AITC) encapsulated in either α‐ or β‐cyclodextrin (CD) has previously been evaluated as a slow‐release additive in polylactide‐co‐polycaprolactone (PLA–PCL) films designed for use in cheese packaging. In the research described in this article, thermogravimetric analysis (TGA) and thermogravimetric analysis in tandem with mass spectrometry (TGA–MS) were used to explore the thermal properties of CD‐encapsulated AITC complexes as well as those of PLA–PCL films containing these complexes. To our knowledge, this is the first reported application of the TGA–MS technique to explore the thermal stability of CD‐entrapped AITC and the first study to report differences in thermal stability of AITC in α‐and β‐CD cavities in the solid state. Observed differences in the thermal degradation profile of films containing the CD complexes can be explained if AITC binds more strongly to β‐CD than to α‐CD. This hypothesis has been reinforced by gas chromatography (GC) and high performance liquid chromatography (HPLC) studies, the results of which suggest that a new covalently bound AITC–CD complex may be formed when incorporating the β‐CD complex of AITC in PLA–PCL films but not when incorporating the α‐CD complex of AITC. This finding means that the α‐CD complex of AITC would be preferred in situations where adequate long‐term controlled release of AITC from polymer films is required, as for example in the case of active packaging applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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

Packaging 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.     

Low-density polyethylene/polyamide 6 blends from multilayer films waste

Multilayer films combine properties of different polymers in a single material, attending specifications to applications such as packaging. However, the mechanical recycling for this material king is commercially less interesting because the polymeric components cannot easily be separated and the direct mechanical processing of the material leads to the immiscible and incompatible polymeric blends. The aim of this study was to evaluate properties of the blends of low-density polyethylene (LDPE) and polyamide 6 (PA6) generated from mechanical recycling of multilayer films constituted by LDPE and PA6, containing maleic anhydride grafted polyethylene (PE-g-MA) as compatibilizing agent and different amounts of virgin PA6. The LDPE/PA6 blends are immiscible for all composition and the use of PE-g-MA has showed little effect on the compatibility of the blends with high content of PA6. However, LDPE/PA6 blends with PA6 content up to 20 wt % showed considerable performance for mechanical performance that can justify the mechanical recycling of the material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47456     

Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Biodegradable poly(ester)urethane (PU) elastomer‐based nanocomposite films incorporated with organically modified nanoclay were prepared with melt‐extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X‐ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water‐vapor barrier properties of the nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrophobic nanocomposites of PBAT with Cl-fn-POSS nanofiller as compostable food packaging films

Antibacterial nanocomposite films of poly(butylene adipate-co-terephthalate) (PBAT) incorporated with different weight percentage of octakis(3-chloropropyl)octasilsesquioxane (chloropropyl functionalized POSS [Cl-fn-POSS]) nanofiller were prepared. The mechanical, thermal, morphological, barrier, and antimicrobial properties were examined. The mechanical properties of the nanocomposite films were enhanced by the addition of Cl-fn-POSS nanofiller. An optimum filler loading of 3 wt% is identified to be best suited for maximum enhancement in tensile strength (24 MPa for 3 wt% filled PBAT vs 11 MPa for neat PBAT) while a 1 wt% filler loading was adequate to double the tensile strength. The barrier properties (WVTR and oxygen transmission rate) of PBAT was improved by the presence of Cl-fn-POSS. A volume of 3 wt% filler loading results in 50% reduction of water permeation and 10% reduction in oxygen transmission. The thermogravimetric analyses of the nanocomposites indicated that the filler enabled the enhancement of thermal stability of PBAT. The nanocomposite films revealed antimicrobial activity with this activity increasing with increasing filler content. PBAT is compostable under suitable conditions and with a low weight percentage of filler that is largely made of silicon dioxide these nanocomposite films can find application as biodegradable food packaging material given their flexibility.     

Processing triacetyl-β-cyclodextrin in the liquid phase using supercritical CO2

TA-β-CD has been proposed as an effective sustained release carrier for highly water soluble drugs with short biological half-lives. In this work, the possibility of preparing drug - triacetyl-β-cyclodextrin (TA-β-CD) complexes in the liquid phase by exploring its solid-liquid-gas equilibrium (S-L-G) under supercritical CO₂ atmosphere was evaluated. The S-L-G equilibrium line for the binary system TA-β-CD + CO₂ was determined by a visual method for pressures up to 25.3 MPa. At the studied conditions, a homogeneous and translucent liquid phase emerge at 307 K when exposed to CO₂ pressurized at 16 MPa and this temperature further increases with increasing pressure, up to 318 K at 25.3 MPa. The S-L-G equilibrium behaviour observed is typical of this kind of asymmetric systems, it is totally CO₂ density-dependent and opens the possibility of further processing TA-β-CD in the liquid phase. In order to investigate the possibility of preparing a drug-TA-β-CD complex in the liquid phase of TA-β-CD, a preliminary experiment was performed at 25 MPa and 308 K using flufenamic acid (FA) as the model active principle.     

Improving the mechanical properties of ethylene propylene diene monomer rubber/low density polyethylene/rice husk biocomposites by using various additives of filler and gamma irradiation

In this work, ethylene propylene diene monomer rubber (EPDM)/low‐density polyethylene (LDPE) (100/60) blend was loaded with 20 phr (part per hundred parts of rubber) of rice husk to give biocomposites. To improve the compatibility of this biocomposites, 7 phr of maleic anhydride was also loaded. This biocomposite was then reinforced with 40 phr of high abrasion furnace (HAF)‐carbon black (N330) or 40 phr Hisil. Vulcanization of these biocomposites was carried out by gamma irradiation at doses from 50 to 250 kGy. The EPDM/LDPE blend and its biocomposites were characterized by studying the mechanical, physical, and thermal properties. Also examination by scanning electron microscopy (SEM) was studied. The results indicated that gamma irradiation and fillers improved the physical and mechanical properties and the thermal stability of the obtained biocomposites. The SEM micrographs confirmed the results obtained from mechanical properties. J. VINYL ADDIT. TECHNOL., 25:296–302, 2019. © 2019 Society of Plastics Engineers     

Ultrastructural and antimicrobial impacts of allyl isothiocyanate incorporated in cellulose, β-cyclodextrin,and carbon nanotubes nanocomposites

Antimicrobial nanobio packaging with controlled-release of active compounds is one of the most promising versions of active packaging. In this study, the antimicrobial effect of allyl isothiocyanate (AIT), complexed or not with β-cyclodextrin (βCD), and carbon nanotubes (CNTs) in cellulose films against Salmonella choleraesuis and Listeria innocua was investigated. Structural changes caused by AIT in bacteria were evaluated by transmission electron microscopy (TEM), as well as changes in the surface of the films, which were analyzed by atomic force microscopy and scanning electron microscopy. The active films inhibited the growth of both bacteria and caused damage to the cell membrane. The presence of inclusion complex and CNTs resulted in structural changes in films, such as the formation of lumps and reduction of roughness, respectively. Complexation of AIT with βCD and the use of CNTs increased the retention of the antimicrobial agent, which is desired to promote its controlled diffusion and consequently increase the preservative action of the film. However, when considering the use of βCD inclusion complexes, caution is necessary to prevent detrimental changes in the films' surface.     

Thermal,mechanical, and gas barrier properties of ethylene–vinyl alcohol copolymer‐based nanocomposites for food packaging films: Effects of nanoclay loading

For the application of single‐layer food packaging films with improved barrier properties, an attempt was made to prepare ethylene‐vinyl alcohol (EVOH) copolymer‐based nanocomposite films by incorporation of organically modified montmorillonite nanoclays via a two‐step mixing process and solvent cast method. The highly intercalated tactoids coexisted with exfoliated clay nanosheets, and the extent of intercalation and exfoliation depended significantly on the level of clay loadings, which were confirmed from both XRD measurements and TEM observations. It was revealed that the inclusion of nanoclay up to an appropriate level of content resulted in a remarkable enhancement in the thermal, mechanical (tensile strength/modulus), optical, and barrier properties of the prepared EVOH/clay nanocomposite films. However, excess clay loadings gave rise to a reduction in the tensile properties (strength/modulus/elongation) and optical transparency due to the formation of clay tactoids with a larger domain size. With the addition of only 3 wt % clay, the oxygen and water vapor barrier performances of the nanocomposite films were substantially improved by 59 and 90%, respectively, compared to the performances of the neat EVOH film. In addition, the presence of clay nanosheets in the EVOH matrix was found to significantly suppress the moisture‐derived deterioration in the oxygen barrier performance, implying the feasibility of applying the nanocomposite films to single‐layer food packaging films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40289.     

Improvement of mechanical,thermal and antimicrobial properties of organically modified montmorillonite loaded polycaprolactone for food packaging

The aim of this study is to evaluate the biodegradable packaging materials which will be an alternative to traditional synthetic packaging materials. For this purpose, packaging films containing polycaprolactone (PCL), montmorillonite (MMT), and organically modified montmorillonite (OMMT) were prepared by solution casting method, and the mechanical, physical, structural, antimicrobial, and antifungal properties of these films were examined. Cetyl trimethyl ammonium bromide (CTAB) was used for the modification of montmorillonite. The structural properties of the prepared films were characterized by attenuated total reflection-Fourier transform infrared, X-ray powder diffraction, thermogravimetric analysis, and scanning electron microscopy. The PCL/OMMT structure was found to be thermally more stable than the PCL/MMT structure. The addition of OMMT to PCL improved the thermal and mechanical properties of the films compared with the pure PCL and PCL/MMT films. In addition, adding MMT/OMMT to the PCL caused an increase in the hardness of the films. In the antimicrobial analysis, while no inhibition effect was observed in PCL/MMT films, PCL/OMMT films showed inhibition effect against Staphylococcus aureus. Antifungal tests performed with the prepared films showed that the film-wrapped bread did not deteriorate for 40 days. It is thought that PCL/MMT and PCL/OMMT films prepared in this study will provide an advantage in applications as packaging material.