Unfilled Films Research Articles

Study of the Reinforcing Effect and Antibacterial Activity of Edible Films Based on a Mixture of Chitosan/Cassava Starch Filled with Bentonite Particles with Intercalated Ginger Essential Oil.

Edible films based on biopolymers are used to protect food from adverse environmental factors. However, their ample use may be hindered by some challenges to their mechanical and antimicrobial properties. Despite this, in most cases, increasing their mechanical properties and antibacterial activity remains a relevant challenge. To solve this problem, a possible option is to fill the biopolymer matrix of films with a functional filler that combines high reinforcing and antibacterial properties. In this work, biocomposite films based on a mixture of chitosan and cassava starch were filled with a hybrid filler in the form of bentonite clay particles loaded with ginger essential oil (GEO) in their structure with varied concentrations. For this purpose, GEO components were intercalated into bentonite clay interlayer space using a mechanical capture approach without using surface-active and toxic agents. The structure and loading efficiency of the essential oil in the obtained hybrid filler were analyzed by lyophilization and laser analysis of dispersions, ATR-FTIR spectroscopy, thermogravimetry, and X-ray diffraction analysis. The filled biocomposite films were analyzed using ATR-FTIR spectroscopy, optical and scanning electron spectroscopy, energy dispersive spectroscopy, mechanical analysis under tension, and the disk diffusion method for antibacterial activity. The results demonstrated that the tensile strength, Young's modulus, elongation at the break, and the antibacterial effect of the films increased by 40%, 19%, 44%, and 23%, respectively, compared to unfilled film when the filler concentration was 0.5-1 wt.%.

Using α-chitin nanocrystals to improve the final properties of poly (vinyl alcohol) films with Origanum vulgare essential oil

-In the present work, nanocomposite films based on poly(vinyl alcohol) (PVA) containing different amounts of Origanum vulgare essential oil (OEO, 0, 0.5, 1, 1.5 and 2% v/v) were reinforced with 0.5% (w/v) of alphachitin nanocrystals (α-CHNC, from shrimp and from lobster) and prepared by solvent casting. Another set of films was prepared without α –CHNC to assess the effect of the nanocrystals on the final properties of the films. The obtained nanocomposite films were homogeneous and showed better thermal stability and mechanical properties. After exposure the nanocomposite films to ultraviolet radiation, the obtained data revealed that the presence of α-CHNC into the materials has a retarding effect on their loss of mechanical properties. It was also shown that the antioxidant activity and the total phenolic content of the materials increased with the augmentation of OEO and with the antioxidant release time. Interestingly, the nanocomposite films made of chitin nanocrystals from shrimp showed better total phenolic content than the unfilled films and the nanocomposite films made of chitin nanocrystals from lobster over the first 48 h. Henceforward, this study demonstrated the potential of the nanocomposite films based on PVA, OEO and reinforced with α-CHNC for active food-packaging applications.

Deformation-Strength Properties of Films Derived from Hydroxyethylcellulose Filled with Micro- and Nanocrystalline Cellulose

A study was carried out on the preparation and properties of film materials obtained from hydroxyethylcellulose filled with micro- and nanocrystalline cellulose, which may hold promise for use as nonpolluting biodegradable coatings or films. We studied the effect of size (micro- or nanocrystalline cellulose), means of dispersion (mechanical stirring or ultrasonic treatment), and filler concentration on the deformation-strength properties of filled hydroxyethylcellulose films. The effect of the means of dispersion on the structure and properties of the matrix derived from two different types of hydroxyethylcellulose and on the efficiency of dispersion of the filler was studied by viscosimetry, UV spectrophotometry, and optical microscopy. Independently of the type of hydroxyethylcellulose, ultrasonic treatments leads to a reduction in the viscosity of their solutions and increase in optical transparency but the effect of such treatment has significantly different effects on the deformationstrength properties of both unfilled films and the films filled with micro- and nanocrystalline cellulose.

Facile strategy for improvement properties of whey protein isolate/walnut oil bio-packaging films: Using modified cellulose nanofibers

This work aims to explore the addition impact of surface modified cellulose nanofibers (CNF) with poly (methyl methacrylate) (PMMA), CNF-g-PMMA, on the required properties of whey protein isolate (WPI)/walnut oil (WNO) films for packaging applications. WPI/WNO films containing 15 wt% WNO were selected for CNF incorporation. The addition effects of different quantities of unmodified and modified CNF (CNF and MCNF) on mechanical strength, fracture surface morphology, hydrophobicity, water vapor permeability (WVP), water uptake, and transparency of bionanocomposite films were studied. Fracture surface was observed by Scanning electron microscopy (SEM). The maximum ultimate tensile strength (UTS) was obtained to be 9 ± 0.11 and 10.38 ± 0.16 MPa, respectively, at 7.5 wt% of both CNF and MCNF. Compared with WPI/WNO unfilled films, while CNF increased the hydrophilicity of the films, MCNF resulted in more hydrophobic films. In addition, 51% and 64% improvement in water vapor barrier features of CNF and MCNF-loaded films was observed, respectively. The similar trend was occurred for the water uptake behavior. In the case of film transparency, MCNF-loaded films were opaque with 18.12% light transmittance (600 nm wavelength). Generally, WPI films including 15 wt% of WNO and 7.5 wt% MCNF shows promising potential as bio-packaging films.

Mango kernel starch films as affected by starch nanocrystals and cellulose nanocrystals

Mango seeds have been used to obtain components for nanocomposite films, namely, starch and starch nanocrystals (SNC) from seed kernels, and cellulose nanocrystals (CNC) from seed shells. Lignin was also recovered from shells. Starch-based films were prepared with different contents and combinations of SNC and CNC. SNC exhibited round-like rather than platelet-like morphology, and their effect on water vapor barrier was not as high as that of the needle-like CNC. Also, CNC were more effective than SNC to increase elastic modulus. On the other hand, CNC impaired more the elongation. The optimized conditions (1.5 wt% CNC and 8.5 wt% SNC on a starch basis) resulted in a film with enhanced strength, modulus, and barrier to water vapor when compared to the unfilled film, although the elongation has been impaired.

Hydrolytic Stability of Films of Aromatic Polyimides and Composites on Their Basis, Filled with Carbon Nanocones

Variation of the mechanical and thermal characteristics of poly(4,4′-oxydiphenylenepyromellitimide) and poly{1,3-bis(3′,4-dicarboxyphenoxy)benzene [4,4′-bis)4′-N-phenoxydiphenylsulfone]imide} films and nanocomposites based on these polyimides and filled by carbon nanocones/disks in the course of hydrolysis in an alkaline solutions was studied. The goal of the study was to obtain systematic information about the influence exerted by carbon nanoparticles introduced into polyimide films with varied chemical structure on the stability of the resulting film materials against a prolonged action of active hydrolyzing media. It was shown that the hydrolytic stability of the materials under study is largely determined by the molecular packing density. Introduction of nanoparticles into the polymers under study may result in that the concentration in the material of the excess free volume localized at polymer–filler interfaces increases. This, in turn, causes a decrease in the hydrolytic stability of the nanocomposite film as compared with unfilled films of the matrix polyimide. The opportunity was considered of raising the hydrolytic stability of the polyimide and nanocomposite material by making higher the average packing density.

Nanocomposite Films from Mango Kernel or Corn Starch with Starch Nanocrystals

Mango kernels are used for the first time as a source of both starch and starch nanocrystals (SNC) for bionanocomposite films. The starch yield was 38.5%, whereas the SNC yield (from starch) is more than 30%. Bionanocomposite films are produced from mango kernel starch (MKS) and 0–10 wt% SNC, and the corresponding films are also obtained from commercial corn starch. The addition of 5% SNC to MKS films increases their tensile strength and modulus in about 90% and 120% respectively, and reduces their water vapor permeability in about 15%. On the other hand, the film elongation has been reduced to half the one for the unfilled film, and the opacity has been increased. When compared to the corresponding corn starch films, mango kernel starch films exhibited higher overall tensile strength and elastic modulus, as well as increased opacity.

Effect of nanosized carbon fillers on the hydrolytic stability of films of a heat-resistant aromatic polyimide

The effect of carbon nanoparticles (nanofibers, nanocones/nanodiscs) introduced into a polypyromellitimide matrix on the stability of the mechanical and thermal characteristics of the resulting nanocomposite film materials in the course of hydrolysis in aqueous alkali was studied. The nanocomposite films are less resistant to hydrolysis than the unfilled films of the matrix polyimide. The decreased packing density in the nanocomposite material is considered to be the major factor responsible for the observed effects. A certain excess void volume in the nanocomposite appears owing to insufficient compatibility of the matrix polyimide with the nanoparticles, manifested in the course of the material preparation.

Novel Polymer Clay‐Based Nanocomposites: Films with Remarkable Optical and Water Vapor Barrier Properties

The impact of varying the copolymer composition of styrene–co‐butyl acrylate copolymers on the dispersion of montmorillonite (MMT) clay and the effect thereof on the transparency and water vapor barrier properties of the resultant films is assessed. The hybrid latexes containing MMT clay concentrations of 10–30 wt% are prepared using miniemulsion polymerization. The morphology of the resultant latexes shows that the MMT particles are predominantly adhered onto the surface of the latex particles. However, the transparency of the films suggests a fair dispersion of the MMT platelets in the matrix. The thickness‐normalized light transmittance for copolymers with 40 and 50 mol% styrene only decreases from 70% in the neat films to 50% in the nanocomposite films containing 30 wt% clay. The best optical properties are observed for the copolymers with 30 mol% styrene, in which the light transmittance only decreases from 85% (unfilled film) to 60% in the nanocomposite films containing 30 wt% clay. Overall, the water vapor barrier properties are much higher in the copolymer films with 30 mol% styrene due to the unique morphological organization of MMT platelets in the matrix. image

Peculiarities of the initial stages of carbonization processes in polyimide-based nanocomposite films containing carbon nanoparticles

AbstractCarbonization of the polyimide-based composite films containing carbon nanoparticles, namely nanofibers and nanocones/disks, in the temperature range 500–550°C was studied and the kinetics of the initial stage of carbonization and the effect of the filler on the mechanical properties of the carbonized films were evaluated. Two polyimides (PIs) characterized by different macrochains’ rigidity and different degrees of ordering of the intermolecular structure were used. The character of the nanofiller’s action on the kinetics of the carbonization process depends on the heating rate. In this work, the intensity of the destruction of the PI matrix of the composite films was shown to be slightly higher than that of films of the same polymers with no filler. The introduction of the carbon nanoparticles into both PIs provokes the increase in the ultimate deformation values of the partially carbonized films, while the carbonization of the unfilled PI films yields the brittle materials. The Young’s modulus ...

Adhesion and barrier properties of polymeric nanocomposite films

Polymeric nanocomposite films with superparamagnetic Fe3O4 nanoparticles in polystyrene or poly(methyl methacrylate) matrices on the surface of 08kp steel were prepared. The adhesion of the synthesized two-layer film nanomaterials and their barrier properties in 3 wt % aqueous NaCl solution were studied in comparison with the unfilled polymer films. Adequate mathematical description of the influence of the nanoparticle concentration (0–10%) on the adhesion of the polymeric nanocomposites was made. The barrier properties of the polymeric nanocomposite films were evaluated by measuring the electrode potentials of the uncoated and coated specimens. Based on the experimental data obtained, the following nanocomposite was suggested as material for film deposition: poly(methyl methacrylate) + 5.6 wt % Fe3O4 with the nanoparticle size of approximately 10 nm. Films of this material ensure high adhesion (100%) and sufficiently good (86%) barrier properties.

Modifications induced by the addition of a nanoclay in the functional and active properties of an EVOH film containing carvacrol for food packaging

A nanoclay/EVOH composite has been developed to retard the release of a volatile antimicrobial from an EVOH film with application in active packaging. Concretely, 2% of bentonite nanoclay was added to the EVOH-29 matrix to modify its mass transport properties and consequently the activity of the antimicrobial film. The nanocomposite obtained, containing 5% of carvacrol as antimicrobial compound, is characterized in terms of antimicrobial solubility and release, water vapor solubility and permeability, oxygen and carbon dioxide permeability, diffusivity and solubility, thermal properties, and microstructural morphology.The clay-filled EVOH-29 film had a similar macroscopic appearance to the unfilled film, thanks to the excellent dispersion of bentonite nanoparticles as revealed by TEM images. Glass transition temperature was higher in the modified material, whereas fusion temperature was slightly lower, although the differences found were not significant. Water vapor, oxygen, carbon dioxide, and carvacrol solubilities were found to be higher for the modified polymer, whereas water vapor permeability, carvacrol diffusivity, and oxygen and carbon dioxide permeabilities and diffusivities were found to be lower for the nanocomposite. All parameters, with the exception of water vapor permeability, increased with the water concentration in the polymeric matrix. Therefore, the incorporation of 2% bentonite nanoclay in EVOH-29 provides a significant improvement in the controlled release of the antimicrobial agent with no relevant drawbacks.

Preparation of bio-based nanocomposite emulsions: Effect of clay type

Bio-based nanocomposite latexes were prepared by emulsification–diffusion method. Two kinds of silicate, sodium and organo-modified montmorillonites, were compared and clay concentrations were varied at 1–6wt%. The resultant particles were characterized in terms of particle size, particle morphology, and zeta potential. Silicate dispersion in the polymer matrix was evaluated by X-ray diffractometry and transmission electron microscopy, while thermal properties of the resultant nanocomposite films were also investigated by differential scanning calorimetry and thermogravimetry. The average particle sizes of the emulsions were found in the range of 20–30μm, whereas zeta potentials of the particles were obtained in the range from −37 to −60mV, depending on the silicate type and content. X-ray diffraction patterns combined with micrographs indicated that the silicates were effectively distributed in the polymer matrix where extensive exfoliation and partial intercalation were present. Thermal properties of the nanocomposite films were significantly improved compared to those of the unfilled film. Thermal stability tended to increase in accordance with clay content for both types of silicate, in which the highest shift of degradation temperature was obtained with the sodium montmorillonite filled nanocomposite film at the maximum loading content (6wt%).

The Influence of Engineered Calcium Carbonate Functional Additives on the Mechanical Properties and Value Proposition of Polyethylene Films

The current study considers the use of a selection of engineered ground calcium carbonates in two different polyethylene film systems. The calcium carbonate grades selected cover a range of particle sizes and include uncoated and organically treated examples. Alterations in the processing requirements on mineral addition are reported and their implications for film and masterbatch production considered with respect to energy usage and throughput. Inclusion of the engineered additives allowed production of the same weight of material at lower energy uses or improved productivity at the same energy usage. The effects on the mechanical properties of the composite films with increasing mineral loading have also been measured, demonstrating enhancements particularly in the areas of tear strength and impact resistance. These enhancements allow the possibility of film downgauging relative to the unfilled film without loss of performance and yield a raw material cost saving by reduction of polymer usage.

Correlation between Free-Volume Properties and Pervaporative Flux of Polyurethane−Zeolite Composites on Organic Solvent Mixtures

Micron-sized zeolite particles were incorporated into a polyurethane (PU) matrix to prepare ethylbenzene-selective membranes. The resulting composite membranes were used in the pervaporation (PV) of ethylbenzene/styrene (EB/ST) mixtures. The sorption, diffusion, and PV permeation behaviors as a result of zeolite addition were elucidated. Zeolite is less chemically compatible with organic solvents than PU and the PU-zeolite composites, which exhibited suppressed solvent solubilities compared with pristine PU. However, these membranes favor EB transport by diffusion selectivity. The diffusivity and permeation flux increases in parallel with the enlarged radius of the free-volume hole size (R(4) increasing from 3.46 to 3.64 Å using positron annihilation lifetime spectroscopy analysis) by increasing the zeolite content from 0 to 23%. The enlarged free volume at a zeolite loading of 23% promoted pure solvent diffusivities by 10% higher than that of the unfilled film. During the PV operation on the EB/ST mixture, a significant diffusion-coupling was observed, and the permeant diffusion coefficients from the binary mixture exceeded the pure solvent diffusivity. The permeation flux was greatly improved (up to 0.72 kg/m(2)·h) by zeolite addition without any detrimental effect on the separation efficiency.

Effect of glycerol on the morphology of nanocomposites made from thermoplastic starch and starch nanocrystals

Fully bio-based nanocomposites were prepared using starch nanoparticles obtained by acidic hydrolysis of waxy maize starch granules as reinforcement. The same type of starch, which contains 99wt.% amylopectin, was used to prepare glycerol plasticized and unplasticized matrices. The X-ray diffraction pattern of the plasticized reinforced materials displays both A and B-type peaks, showing that the crystalline structure of the nanocrystals was not affected by processing. The storage modulus of the composite material increases, with respect to the unfilled film, by 470% at 50°C, while the permeability increases by 70%. This is probably due to a good association of glycerol with the nanoparticles leading to a fibrillar structure, studied by scanning electron microscopy of plasticized and unplasticized composites.

Morphological and dielectric properties of barium chloride-filled poly(vinylidene fluoride) films

Morphological characteristics of poly(vinylidene fluoride) (PVDF) films, filled with mass fractions (w ≤ 20%) of Barium Chloride (BaCl2), were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectra and differential scanning calorimetry (DSC) measurements. The dielectric properties of films were measured from 250 Hz to 1 MHz range between 100 and 400 K as a function of frequency and temperature. Spectroscopic data revealed that the filled and unfilled films include a-, b-, and c-crystalline phases. By a 20% filling, 73% increase was obtained in the total degree of crystallinity. Since the BaCl2 formed fluorine bridges over the chain segments on the crystal lamellar surface, the c-crystalline phase decreased, whereas the total degree of crystallinity increased. Dielectric measurements showed that maximum of the dielectric loss factor belonging to b-relaxation transition decreased linearly with filling level. The filling process did not have any effect on the real dielectric constant till a-relaxation transition region. However, in the a-relaxation transition region, it was determined that the real dielectric constant increased linearly with filling level. POLYM. COMPOS., 31:1782–1789, 2010. a 2010 Society of Plastics Engineers

The Preparation of Core–Shell P(St-MMA)–SiO2 Hybrid Nanoparticles and Filling in the Styrene/n-butyl Acrylate Adhesive

In this study, core–shell poly(styrene-methyl methacrylate) (P(St-MMA))–SiO2 hybrid nanoparticles were prepared successfully by emulsion polymerization. Firstly, nanosilica particles were modified by oleic acid (OA) in order to introduce the polymerization active vinyl groups and hydrophobic groups onto the nanosilica. This was followed by graft copolymerization onto the modified nanosilica particles to obtain P(St-MMA)–SiO2 hybrid nanoparticles. The hybrid nanoparticles were characterized by: transmission electron microscope (TEM); Fourier transform infrared spectroscopy (FT-IR); dynamic light scattering (DLS); and thermal gravimetric analysis (TGA). The results indicate that the hybrid particles had a regular spherical morphology with a diameter ranging from 50 to 80 nm. A reasonable mechanism for the preparation of the core–shell hybrid nanocomposites was presented. The obtained hybrid nanoparticles were subsequently (incorporated into) filled in the poly(styrene-n-butyl acrylate) (PSBA) latex. The effect of (hybrid nanoparticle concentration) filling content on the physicochemical properties of PSBA latex and the resulting node strength per monofilanment of the fibre glass gridding cloth was investigated. The results indicated that the node strength/monofilanment of the fibre glass gridding cloth coated with the PBSA latex filled with 1.0 wt% hybrid nanoparticles demonstrated greatest improvement among all the investigated PSBA latex. This result is related to the rheological properties of the latex. Moreover, the water-resistance property of PSBA composite film was found to be enhanced when compared with that of unfilled PSBA film.

Characterization of nanocellulose‐ reinforced shape memory polyurethanes

AbstractBACKGROUND: Shape memory polymers are capable of fixing a transient shape and of recovering their original dimensions by the application of an external stimulus. Their major drawback is their low stiffness compared to smart materials based on metals and ceramics. To overcome this disadvantage, nanocellulose was utilized as reinforcement.RESULTS: Composites were prepared by casting stable nanocellulose/segmented polyurethane suspensions. The heat of melting of the polyurethane soft segment phase increased on cellulose addition. Composites showed higher tensile modulus and strength than unfilled films (53% modulus increase at 1 wt% nanocellulose), with higher elongation at break. Creep deformation decreased as cellulose concentration increased (36% decrease in 60‐minute creep by addition of 1 wt% nanocellulose). The nanocomposites displayed shape memory properties equivalent to those of the neat polyurethane, with recoveries of the order of 95% (referred to second and further cycles).CONCLUSIONS: It is possible to markedly improve the rigidity of shape memory polymers by adding small amounts of well‐dispersed nanocellulose. However, this improvement did not have substantial effects on the material shape fixity or recovery. Shape memory behavior seems to continue to be controlled by the polymer properties. Copyright © 2007 Society of Chemical Industry

Dielectric properties of polyimide/Al 2O 3 hybrids synthesized by in-situ polymerization

Polyimide/nano-Al 2O 3 hybrids were prepared via simple in-situ polymerization and the thermal imidation routes. The hybrids film was characterized by transmission electron microscope (TEM) and infrared spectrum (IR). The dielectric behaviors of the composites were investigated as a function of the concentration of the Al 2O 3 nanoparticles. The results show that, at ± 980 V (bipolar), the corona-resistant life to the breakdown of polyimide with nano-Al 2O 3 loading of 30% is 93 min which is over 10 times longer than that of the unfilled film. Such large enhancement may originate from the shielding, thermal conduction and thermal stability effects of the nano-Al 2O 3 layer. As the nano-Al 2O 3 loading increases, the volume resistivity and the electrical breakdown strength show a little decline, while the dielectric constant of the hybrid films increases, which could be attributed to the significant interfacial zone between the polyimide and the filler.