Preparation and Barrier Properties of Chitosan-Layered Silicate Nanocomposite Films

Summary: In this study, chitosan nanocomposite films were prepared using a solvent-casting method by incorporation of an organically modified montmorillonite (Cloisite 10A). The effect of filler concentration on the water vapor permeability, oxygen permeability, mechanical and thermal properties of the composite films was evaluated. The structure of nanocomposites and the state of intercalation of the clay were characterized by XRD. The water vapor permeability of pure chitosan films was measured as a function of relative humidity (RH). It was found that the permeability value increased with an increase in RH. The water vapor and gas permeability values of the composite films decreased significantly with increasing filler concentration. Permeation data was fitted to various phenomenological models predicting the permeability of polymer systems filled with nanoclays as a function of clay concentration and aspect ratio of nanoplatelets. According to the XRD results, an increase in basal spacing was obtained with respect to pure clay for chitosan/clay nanocomposites. This demonstrated the formation of intercalated structure of clay in the polymer matrix. Tensile strength and elongation at break of the composites increased significantly with the addition of clay, however the thermal and color properties of the films were not much affected by the intercalation of clay into polymer matrix.     

Characterization of an antimicrobial poly(lactic acid) film prepared with poly(ε‐caprolactone) and thymol for active packaging

Antimicrobial active films based on poly(lactic acid) (PLA) were prepared with poly(ε‐caprolactone) (PCL) and thymol (0, 3, 6, 9, and 12 wt%) by solvent casting methods. The films were characterized by thermal, structural, mechanical, gas barrier, and antimicrobial properties. Scanning electron microscopy analysis revealed that the surface of film became rougher with certain porosity when thymol was incorporated into the PLA/PCL blends. Thymol acted as plasticizers, which reduce the intermolecular forces of polymer chains, thus improving the flexibility and extensibility of the films. The addition of PCL into the pure PLA film decreased the glass transition temperature of the films. The presence of thymol decreased the crystallinity of PLA phase, but did not affect the thermal stability of films. Water vapor barrier properties of films slightly decreased with the increase of thymol loading. The antimicrobial properties of thymol containing films showed a significant activity against Escherichia coli and Listeria monocytogenes. The results indicated the potential of PLA/PCL/thymol composites for applications in antimicrobial packaging. Copyright © 2014 John Wiley & Sons, Ltd.     

Hydrophilic nature and sorption-diffusion properties of nanocomposite hybrid polysulfone films

Hybrid nanocomposite films containing silica (??11.4 wt.%) or titania (??18.8 wt.%) in the polymer matrix were prepared by the sol-gel method using the hydrolytic polycondensation of tetraethoxysilane and tetrabutoxysilane in a THF solution of aromatic polymer, polysulfone (PSF). The influence of the oxide nature and the film composition on the structure, the interaction of the polymer with oxides, hydrophilicity, and sorption-diffusion properties of the hybrid films were studied by FTIR spectroscopy, atomic force microscopy, dynamic light scattering, and a complex of other physicochemical methods. The absence of chemical or intermolecular hydrogen bonds between the polymer and oxide particles in the PSF films was shown. The average size of the oxides (SiO₂, ??20 nm; TiO₂, ??90 nm) in the films and roughness of their surface (??0.2?C0.8 nm) were determined. The introduction of oxides into the polymer matrix increases the hydrophilic properties and the ability of the PSF films to swell in water; the diffusion coefficients of water and permeability of water vapor in the PSF films also increase. Titania also induces a more considerable change in the structure of the polymer matrix and more strongly affects the sorption-diffusion properties of the hybrid films in aqueous solutions of THF. All prepared nanocomposite films PSF/SiO₂ and PSF/TiO₂ are capable of extracting an organic component from aqueous solutions and can be used as sorbents and membrane films for the removal of organic substances from the aqueous medium.     

Effect of the Maillard reaction on properties of casein and casein films

The use of biodegradable natural polymers has increased due to the over-solid packaging waste. In this study, a chemical modification of the casein molecule was performed by Maillard reaction, and the modified polymer was evaluated by polyacrylamide gel electrophoresis (PAGE), thermogravimetry/derivative thermogravimetry (TG/DTG), FT-IR, and ¹H-NMR spectroscopy. Subsequently, films based on the modified casein were obtained and characterized by mechanical analysis, water vapor transmission, and erosion behavior. The PAGE results suggested an increase of molecular mass of the modified polymer, and FT-IR spectroscopy data indicated inclusion of C–OH groups into this molecule. The TG/DTG curves of modified casein presented a different thermal decomposition profile compared to the individual compounds. Mechanical tests showed that the chemical modification of the casein molecules provided higher elongation rates (45.5%) to the films, suggesting higher plasticity, than the original molecules (13.4%). The modified casein films presented higher permeability (0.505 ± 0.006 μg/h mm³) than the original polymer (0.387 ± 0.006 μg/h mm³) films at 90% relative humidity (RH). In pH 1.2, modified casein films presented higher erosion rates (32.690 ± 0.692%) than casein films (19.910 ± 2.083%) after 8 h, suggesting an increased sensibility for erosion of the modified casein films in acid environment. In water (pH 7.0), the films erosion profiles were similar. Those findings indicate that the modification of molecule by Maillard reaction provided films more plastic, hydrophilic, and sensitive to erosion in acid environment, suggesting that a new polymer with changed properties was founded.     

Surface modified graphene oxide/poly(vinyl alcohol) composite for enhanced hydrogen gas barrier film

A series of novel polyethyleneimine (PEI) modified graphene oxide (PEI-mGO) filled poly(vinyl alcohol) (PVA) nanocomposite (PEI-mGO/PVA) films were prepared by solution-casing for hydrogen gas barrier applications. Hydrophilic PEI was used to simultaneously reduce and modify graphene oxide sheets, thereby facilitating a homogeneous dispersion of PEI-mGO in the PVA matrix. The effects of PEI-mGO on the morphology and properties of the nanocomposite films were examined by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and field emission scanning electron microscopy. Analogous GO/PVA composites were also prepared and characterized for comparative purposes. The PEI-mGO/PVA nanocomposites showed higher thermal and mechanical stability as well as remarkable improvement in hydrogen gas barrier properties compared to the PVA film; specifically, the PEI-mGO/PVA film having 3.0 wt% of PEI-mGO content exhibited almost 95% decrease in GTR and permeability values compared to PVA film.     

Synergistic effect of polylactic acid(PLA) and Poly(butylene succinate-co-adipate) (PBSA) based sustainable,reactive, super toughened eco-composite blown films for flexible packaging applications

Polylactic acid (PLA)/poly (butylene succinate-co-adipate) (PBSA) based blend films at variable compositions and fixed weight percentage of Epoxy functionalized styrene acrylate (ESA) were prepared using a single step blending process, followed by blown film extrusion process. The morphological studies revealed proper interaction between polymers by the interaction of chain extender (ESA) subsequently improved the mechanical properties of the prepared blown films. Similarly, the blend films showed a decrease in oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) in the order of 60% and 14% as compared with VPLA film. The optical and antislip properties of the blend films also increased considerably. The thermal analysis of the blend films depicted marginal enhancement in the stability of PLA along with heterogeneous nucleation effect in PLA matrix due to the presence of ESA and PBSA.     

引入三氟甲基侧基对对苯醚型聚酰亚胺薄膜吸水性及水蒸汽透过性的影响

合成了3种含三氟甲基的芳香二胺,进而与3,3′,4,4′-联苯四甲酸二酐(BPDA)缩聚,得到3种对苯醚型含氟聚酰亚胺薄膜,并由4,4′-二氨基二苯醚（4,4′-ODA）与BPDA缩聚得到聚酰亚胺薄膜。 对4种聚酰亚胺薄膜的水蒸汽透过率、吸水性和热学性能的测试结果表明,其中聚合物PI-1（2,2′-BTF-4,4′-BADE+BPDA;BTF：双三氟甲基;BADE：二氨基二苯醚）的水蒸汽透过率为7.70 g/（h·m2）,吸水率为0.67%,玻璃化转变温度为259.74 ℃,质量损失5%的温度为521.40 ℃,具有良好的水蒸汽透过性和低吸水性。     

Studies on functional properties of PCL films modified by electron radiation and TAIC additive

Investigation of the effect of electron radiation and triallyl isocyanurate (TAIC) on the functional properties of poly(ε-caprolactone) (PCL) films was the aim of the present paper. The mechanical properties from static tensile tests, resistance to strain at elevated temperatures, permeability of oxygen and water vapor, shrinkage, luminous transmittance, haze and surface free energy were determined. It was found that irradiation of PCL containing TAIC induces larger and more distinct changes in the film properties with regard to the irradiation of PCL with no TAIC. This fact results from formation of a crosslinked structure, in which TAIC participates in linking of PCL macromolecules. The extent of observed changes essentially depends on the magnitude of the electron radiation dose. It was also found that films obtained exhibit a two-phase structure (crosslinked and non-crosslinked) in the case of samples with TAIC, and structural changes associated with elongation of macromolecules, formation of branched structures or polymer degradation in the case of samples with no this compound.     

Poly(caprolactone triol) as plasticizer agent for cellulose acetate films: influence of the preparation procedure and plasticizer content on the physico‐chemical properties

The influence of the plasticizer content and film preparation procedure on the morphology, density, thermal and mechanical properties of cellulose acetate (CA) films plasticized with poly‐(caprolactone triol) (PCL‐T), were studied. Differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), scanning electron microscopy (SEM), wide‐angle X‐ray diffraction (WAXD) and infrared spectroscopy (FT‐IR) techniques were used. The films were prepared by dry‐casting CA and CA/PCL‐T in acetone or acetone/water solutions, which produced transparent and opaque films, respectively. In contrast to the transparent films, which were dense, the opaque films presented a porous morphology. However, the presence of PCL‐T reduced the opaque film porosity, increasing, in consequence, its bulk density. The TMA results revealed that PCL‐T reduced the glass transition temperature more significantly in the transparent than in opaque films. Only the transparent CA/PCL‐T films presented a melting temperature, that reduced with higher concentrations of PCL‐T, suggesting a higher ordering (crystallinity) when the films were prepared in the absence of water, as observed from WAXD curves. The mechanical properties also showed that the transparent films were more soft and tough than the opaque films. In summary, PCL‐T was a good plasticizer agent for CA films due to the presence of hydrogen bonds between the components (FT‐IR spectra). The presence of water in the dry casting process has a significant effect mainly on film morphology and mechanical properties. Copyright © 2004 John Wiley & Sons, Ltd.     

Photopolymerized Cellulose Acetate/Poly(Acrylic Acid) Semi-IPN Films for Wound Dressing Applications

In this work, semi-IPN films, composed of cellulose acetate(CA) and crosslinked poly(acrylic acid), have been synthesized via benzophenone (BP) induced free radical photo-polymerization of acrylic acid (AAc) in the presence of dissolved cellulose acetate (CA) using N,N’ methylene bisacrylamise (MB) as the crosslinking agent. The mechanical properties were tested for the films having different compositions of MB, CA and AAc in the feed mixtures. The tensile strength (TS) and percent elongation (PE) were found to increase with a concentration of CA in the films, but showed decreasing trends with concentrations of CA in the films. However, with AAc content in the films, the TS increased and PE showed just the opposite trend. The film samples were also studied for water vapor and oxygen permeation studies. The water vapor transmission rate (WVTR) decreased with MB and CA contents, but showed an increasing trend with AAc contents in the films. Finally, a representative sample showed fair antibacterial and antifungal action against E. coli and Aspergillus flavus when studied using the ‘Zone of inhibition method’.     

紫外光固化的聚氨酯－丙烯酸酯－纤维素复合膜

再生纤维素膜(甘蔗渣浆制)表面直接用紫外光固化聚氨酯-丙烯酸酯制备出防水性复合膜。由红外光谱和扫描电镜研究了复合膜的结构。同时,测定了膜的防水性、力学性能、水汽透过性和尺寸稳定性。实验结果表明,当聚氨酯：丙烯酸酯为40:55(质量比),在400W紫外光下固化5min制得的复合膜具有致密的表面结构和较好的性能,该膜经水浸泡后其断裂强度可达干膜的90%,浸水收缩率和膨胀率均小于2.5%,水汽渗透量仅为再生纤维素膜的1/4.由此表明复合膜的防水性和尺寸稳定性明显提高。此外,该复合膜在可见光区的透光率在80%～90%之间,而且对紫外光有屏蔽作用。     

Films prepared from electrosterically stabilized nanocrystalline cellulose

Electrosterically stabilized nanocrystalline cellulose (ENCC) was modified in three ways: (1) the hydroxyl groups on C2 and C3 of glucose repeat units of ENCC were converted to aldehyde groups by periodate oxidation to various extents; (2) the carboxyl groups in the sodium form on ENCC were converted to the acid form by treating them with an acid-type ion-exchange resin; and (3) ENCC was cross-linked in two different ways by employing adipic dihydrazide as a cross-linker and water-soluble 1-ethyl-3-[3-(dimethylaminopropyl)] carbodiimide as a carboxyl-activating agent. Films were prepared from these modified ENCC suspensions by vacuum filtration. The effects of these three modifications on the properties of films were investigated by a variety of techniques, including UV-visible spectroscopy, a tensile test, thermogravimetric analysis (TGA), the water vapor transmission rate (WVTR), and contact angle (CA) studies. On the basis of the results from UV spectra, the transmittance of these films was as high as 87%, which shows them to be highly transparent. The tensile strength of these films was increased with increasing aldehyde content. From TGA and WVTR experiments, cross-linked films showed much higher thermal stability and lower water permeability. Furthermore, although the original cellulose is hydrophilic, these films also exhibited a certain hydrophobic behavior. Films treated by trichloromethylsilane become superhydrophobic. The unique characteristics of these transparent films are very promising for potential applications in flexible packaging and other high-technology products.     

Antimicrobial,mechanical, barrier,and thermal properties of bio‐based poly (butylene adipate‐co‐terephthalate) (PBAT)/Ag2O nanocomposite films for packaging application

Bio‐based nanocomposites of poly (butylene adipate‐co‐terephthalate) (PBAT)/silver oxide (Ag₂O) were prepared by the composite film casting method using chloroform as the solvent. The prepared Ag₂O at different ratios (1, 3, 5, 7, and 10 wt%) is incorporated in the PBAT. The PBAT nanocomposite films were subjected to structural, thermal, mechanical, barrier, and antimicrobial properties. The electron micrographs indicated uniform distribution of Ag₂O in the PBAT matrix. However, the images indicated agglomeration of Ag₂O particles at 10 wt% loading. The thermal stability of the nanocomposite films increased with Ag₂O content. The tensile strength and elongation of the composite films were found to be higher than those of PBAT and increased with Ag₂O content up to 7 wt%. The PBAT‐based nanocomposite films showed the lower oxygen and water vapor permeability when compared to the PBAT film. Antimicrobial studies were performed against two food pathogenic bacteria, namely, Klebsiella pneumonia and Staphylococcus aureus.     

氧化石墨烯增强卡拉胶复合膜的制备与性能

在Hummers法基础上制得了氧化石墨烯(GO), 采用流延法制备了氧化石墨烯/κ-卡拉胶(GO/κ-Car)复合膜材料. 结合红外光谱、 扫描电子显微镜及热重分析对其结构进行表征. 探讨了不同条件所得膜的成膜性、 溶解性、 透气性和力学性能, 得到性质稳定GO/κ-Car复合膜的制备条件为15.0 g 3%的κ-Car溶液、0.040 g GO粉末及5.0 g 8%的PVA溶液于75 ℃搅拌混合5 h后, 流延铺平, 于30 ℃烘干6.5 h. GO质量分数为5%的GO/κ-Car复合膜的最大负荷、 拉伸强度及杨氏模量分别是对照组κ-Car膜的1.5倍、 1.5倍和1.6倍. 同时, GO/κ-Car复合膜具有较强的透气性能, 且保留了κ-Car清除羟基自由基的生物性能.     

In situ synthesis of polyethylene terephthalate nanocomposites using bis (2‐hydroxyethyl) phthalate monomer

In this article, we address in situ synthesis of polyethylene terephthalate (PET) nanocomposites using the bis (2‐hydroxyethyl) phthalate monomer and inorganic layered materials (sulfanilic acid salt‐modified magnesium aluminum‐layered double hydroxides [MgAl LDH‐SAS] and Dimethyloctadecyl [3‐(trimethoxysilyl) propyl] ammonium chloride [DTSACl] and tetraethyl orthosilicate [TEOS]‐ modified clay [CL120‐DT]). The dispersion morphology of the synthesized nanocomposites was evaluated using XRD and TEM, from these results, it was confirmed that 0.5 wt% loaded PET/MgAl LDH‐SAS and PET/CL120‐DT nanocomposites have flocculated and intercalated morphologies, respectively. Thermomechanical analyses were performed by thermogravimetric analysis, dynamic mechanical analysis, and differential scanning calorimetry, respectively. Moreover, the water vapor transmission rate (WVTR) values of a pure PET, PET/CL120‐DT 0.5 wt%, and PET/MgAl LDH‐SAS 0.5 wt% nanocomposites were found to be 49, 45, and 46 g·m^?2·day^?1, respectively. Furthermore, the gas barrier properties of PET composite films containing various amounts of inorganic nanoparticles were investigated using Gas permeability analysis (GPA).     

Synergistic effect of graphene oxide nanoplatelets and cellulose nanofibers on mechanical,thermal, and barrier properties of thermoplastic starch

In recent years, because of the limited availability of oil resources and the increasing concerns regarding environment protection, much attention has been drawn to produce packaging films based on degradable biopolymers instead of synthetic polymers. On the other hand, because of the high costs of oil extraction, raw materials and film production, and disposing of the waste products of synthetic films, the need to replace these films with less pollutant and more cost‐effective films is growing globally. In this study, to answer the need for replacing synthetic polymer films, nanocomposite films based on thermoplastic starch reinforced with cellulose nanofibers and graphene oxide nanoplatelets were produced and characterized. The results implied that the synergistic effect of cellulose nanofibers and graphene oxide nanoplatelets has played an important role in improving the mechanical properties of the films. The results showed that with the addition of cellulose nanofibers and graphene oxide nanoplatelets, the tensile strength and elastic modulus of starch film were increased from 3 and 32 MPa to 13 and 436 MPa, which corresponds to 438% and 1435% improvement, respectively. In addition, the oxygen permeability resistance and the water vapor transmission for samples containing 3 wt% of graphene oxide nanoplatelets was decreased by 78% and 30% compared with the thermoplastic starch film, respectively. The permeability coefficient of the samples containing 3 wt% graphene oxide nanoplatelets for oxygen, nitrogen, and carbon dioxide have proved to be 0.051, 0.054, and 0.047 barrer, which shows that these films can perform well as packaging films.     

Toward a quantitative description of the anodic oxide films on aluminum

A method to quantify the composition of anodic oxide films on aluminum using Infrared Spectroscopic Ellipsometry (IRSE) is proposed. It consists of obtaining the absorption coefficient of the film as a function of wavelength. Using values of the absorption coefficients for the pure components of the film, the percentages (mole or wt%) of each component in the sample can be calculated.The method is demonstrated in a study of the structure of the oxide film on electropolished aluminum and the anodically formed barrier layer film. Both surface oxides were found to be initially a form of amorphous Al₂O₃. While the barrier film is essentially free of water as prepared, the film on electropolished aluminum contained about 25 wt% water. Hydration of both types of films by immersion in boiling water results in the formation of pseudoboehmite (AlOOH). The technique may have more general applicability to the quantitative determination of the composition of corrosion films and other surface layers on metals.     

Evaluation of methoxy polyethylene glycol‐polylactide diblock copolymers as additive in hypromellose film coating

This paper deals with a new application of diblock methoxy polyethylene glycol‐polylactide block copolymers, a class of synthetic biomaterials largely studied in the pharmaceutical and biomedical fields owing to their favorable properties such as biocompatibility, biodegradability, low immunogenicity, and good mechanical properties. In this work, these materials were evaluated as additives for gastro‐soluble pharmaceutical coating aimed to reduce film stiffness and water permeability. Two copolymers with different polylactide chain lengths were synthesized and characterized in term of molecular weight and solid‐state properties. A series of free films with different hypromellose/copolymers ratio were prepared and characterized in terms of appearance, components miscibility, plasticity, and water vapor permeability. The obtained results demonstrate that copolymers effectively influence hypromellose film properties according to their concentration and molecular weight. Specifically, the addition of the copolymer with a molecular weight of 6.5 kDa in a ratio hypromellose:polymer 5:1, allowed to obtain films with good appearance, improved plasticization, and water permeability properties. For higher molecular weight, copolymer or different ratios was not possible to observe the improvement of all the properties at the same time. The results also make possible to define the critical features to improve in order to use block copolymers as additive in hypromellose film coating. The availability of new water‐soluble additives able to work as plasticizer and moisture sealer in polymeric films represents an important progress not only in the field of pharmaceutical coating but also in that of food coatings, as for example in the formulation of edible films. Copyright © 2013 John Wiley & Sons, Ltd.     

Ethylene-vinyl acetate (EVA)/polycaprolactone (PCL)–Fe3O4 composites

In this study, we investigate the effect of nano sized Fe₃O₄ nanoparticles on the mechanical and thermal properties of EVA/PCL–Fe₃O₄ composites. Composites were prepared using the melt mixing technique on a Rheomex mixer coupled to a single screw extruder. The fine dispersion of nano-Fe₃O₄ aggregates in the polymer matrices led to a significant improvement in the crystallinity, thermal and mechanical properties of EVA/PCL–Fe₃O₄ nanocomposites compared to that of native polymers due to improved interface bonding between the filler and the polymer matrix. Techniques such as scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Instron for mechanical properties were used to characterize nanocomposites samples. The results obtained from this investigation demonstrated that composite materials could be promising raw materials in industry.     

Bionanocomposites poly(ϵ-caprolactone)/organomodified Moroccan beidellite clay prepared by in situ ring opening polymerization: Characterizations and properties

In this study, a series of poly(?-caprolactone) (PCL)/clay bionanocomposites were prepared via in situ ring opening polymerization (ROP) of ?-caprolactone catalyzed by titanium butoxide. The natural Moroccan clay beidellite (BDT), used as nanocharge, was organomodified with cetyltrimethylammonium bromide, CTA, to obtain the organically modified 3CTA-BDT (3 = CTA/BDT equivalent feed ratio). Characteristics of the final nanocomposites are investigated by FTIR, SEC, XRD, SEM, TGA, DSC, optical tensiometry, thermal conductivity and water vapor sorption analysis. The intercalated/exfoliated morphologies, revealed by XRD and SEM analyses, confirm uniform dispersion of the nanoclay within the PCL matrix. Thermal stability of all the nanocomposites is improved by the addition of 3CTA-BDT clay compared to pure PCL polymer. The DSC data show that the addition of 3CTA-BDT particles promotes an increase in the disorder of the crystalline phase, which reduces the crystallinity degree. The hydrophobicity of Polymer/clay compatibility was analyzed by studying surface polarity degree of samples by contact angle measurements. Thermal conductivity and water vapor sorption was also discussed. The permeability (P), the sorption coefficient (S) and the diffusion coefficient (D), showed a significant decrease with increasing 3CTA-BDT loading.