Decrease In Oxygen Permeability Research Articles

Consequences of sequential photooxidation of polycarbonate: Relating microscopic modifications to the change of oxygen permeability

AbstractThe consequences of light‐induced oxidation of polycarbonate on its permeability to oxygen were deeply investigated. Polymer films were sequentially photoaged, resulting in the sequential appearance and growth of oxidation products at the surface of the exposed side up to a limit value, owing to the progressive yellowing of the film during the photoageing process. Such effect restricts drastically the oxidation process to the film surfaces. The observed decrease in oxygen permeability consecutive to exposure of only one side of the film results principally from a decrease in oxygen solubility into the polymer, with a minor reduction of its diffusion ability. This was explained by the increase of the polymer polarity owing to the appearance of several types of polar chemical groups (namely CO and OH) as well as the occurrence of cross‐linking upon photodegradation. This decrease in oxygen permeability is then a positive feature in the case of applications for packaging and medical components. No further decrease in oxygen permeability was observed when the second side of the films was photooxidized, which can be explained by a “funnel effect” type between sorption, diffusion and desorption steps.

Enhancing Hydrophobicity and Oxygen Barrier of Xylan/PVOH Composite Film by 1,2,3,4-Butane Tetracarboxylic Acid Crosslinking.

Hemicellulose has potential advantages in food packaging because of its abundant reserves, degradability and regeneration. However, compared with fossil-derived plastic films, hemicellulose-based films show inferior hydrophobicity and barrier properties because of their low degree of polymerization and strong hydrophilicity. Focusing on such issues, this work covers the modification of a xylan/polyvinyl alcohol (PVOH) film using 1,2,3,4-butane tetracarboxylic acid (BTCA) as esterifying agent. The thus prepared composite film was more compact owing to the esterification reaction with xylan and PVOH forming a crosslinked network structure and reducing the distance between molecular chains. The results showed that BTCA had a positive effect on the oxygen barrier, hydrophobicity and mechanical properties of the composite film. The tensile strength of the xylan/PVOH composite film with 10% BTCA content increased from 11.19 MPa to 13.99 MPa. A 20% BTCA loading resulted in an increase in the contact angle of the composite film from 87.1° to 108.2°, and a decrease in the oxygen permeability from 2.11 to 0.43 (cm3·µm)/(m2·d·kPa), corresponding to increase in the contact angle by 24% and a decrease in oxygen permeability by 80%. The overall performance enhancement indicates the potential application of such composites as food packaging.

Nano-SiO2-modified xylan-PVOH-based composite films: Mechanical and barrier properties investigation

Hemicellulose from a wide range of sources and abundant reserves shows good biocompatibility, degradability, and renewability. Because of its low degree of polymerization and a large amount of hydroxyl groups, hemicellulose-based films exhibit low strength and tend to be hydrophilic, which hinders some potential applications. Therefore, hemicellulose-based films with improved strength and barrier properties are needed. In this study, nano-SiO2 was incorporated into polyvinyl alcohol/xylan matrix for the purpose of preparing an inorganic-organic hybrid composite film with elevated mechanical and barrier performance. The addition of nano-SiO2 can serve this purpose. A 1% nano-SiO2 loading resulted in an increase of contact angle of the composite film from 89.6° to 110.4°, an increase of the tensile strength from 11.2 to 14.8 MPa, and a decrease of oxygen permeability from 1.83 to 0.27 (cm3⋅µm)/(m2·d·kPa), which corresponds to a contact angle that was increased by 23%, tensile strength increased by 32%, and oxygen permeability decreased by 85%. These results indicated that the nano-SiO2 modified xylan film might have great application prospects as a barrier film in food packaging.

Preparation and characterization of innovative poly(butylene adipate terephthalate)‐based biocomposites for agri‐food packaging application

AbstractThe present work reports on the preparation and subsequent mechanical, morphological and thermal characterization of composites based on poly(butylene adipate terephthalate) (PBAT), reinforced with micro‐particles of inorganic bioabsorbable calcium‐phosphate glass (CPG) at different contents up to 40 wt%. The PBAT‐CPG composites were prepared by solvent casting. The resulting composite pellets were used for the injection molding of model 1BA specimens, according to standard UNI EN ISO 527. PBAT‐CPG composites displayed an effective increase of the Young's modulus (E) up to 82% compared to the pristine polymer, while showing a reduction of the yield stress (σy) up to 20%, of the stress at break (σB) up to 46%, of the strain at break (εB) up to 57% and of the toughness (T) up to 72%. The values of E, σy and σB were also compared and validated with theoretical values calculated using Kerner's and Pukanszky's models. Scanning electron microscopy (SEM) images display homogeneous dispersion and distribution of the filler particles in the polymer matrix with no aggregates or phase separation that would cause a deterioration of the material properties. Infrared (IR) spectroscopy did not show structural variations of the polymer matrix due to the CPG presence. The oxygen permeability in PBAT‐based samples assumes significantly lower values when benchmarked with the permeability of low‐density polyethylene (LDPE). Among the different composites, a decrease in oxygen permeability is observed as the CPG concentration increases. Regarding water vapor permeability, PBAT‐based samples show a lower barrier effect than polyethylene (PE): in particular, permeability to water vapor assumes an increasing trend as the quantity of filler increases. The tuneable degradation of the final composite materials was defined by the disintegration degree (DD) determination under composting conditions in a laboratory‐scale reactor. The developed materials prove to be valid biodegradable and eco‐friendly alternatives to traditional thermoplastic polymers, such as LDPE, and can be applied in many fields, especially in package and mulch film applications.

Preparation by direct mixing and characterization of graphene nanoplatelet filled poly(dimethyl siloxane) composites

The present study investigated the effect of GN nanoplatelets on the properties of PDMS composites, prepared by direct mixing, using sonication. The calculation of the ratio of intensities of D (1350 cm−1) and G (1580 cm−1) bands (ID/IG), recorded by RAMAN spectroscopy, suggested an increase in carbon defects, upon the incorporation of grapheme into the PDMS matrix. This effect was attributed to the sonication procedure applied to the mixture. The thermal stability of the composites deteriorated, especially for higher GN concentrations (0.8 and 1 phr), as detected by thermogravimetric analysis (TGA). As to their mechanical properties, the tensile strength was enhanced up to 69% for composites reinforced with 0.5 phr GN, whereas the elongation at break increased for all composites, along with the modulus of elasticity, which improved especially at higher GN content (0.5 and 0.8 phr). The incorporation of GN nanoplatelets affected the elastomeric network, restricting the swelling of specimens immersed in toluene, especially for the 0.5 phr GN composite. Membranes of PDMS composites reinforced with 0.5 phr and 1 phr GN, exhibited a decrease in oxygen permeability of 28% and 53% respectively, in comparison with unreinforced PDMS specimens.

The effect of graphene oxide on thermomechanical and permeability properties of poly(dimethyl siloxane) composites

The effect of graphene oxide (GO) on the properties of composites withhydroxyl-terminated poly(dimethyl siloxane) (PDMS) matrices, prepared by solution mixing, using tetrahydrofuran (THF) as a solvent, were examined. Viscosity measurements during the vulcanization reaction, usinga Brookfield viscosimeter, revealed that GO increases the viscosity of the system, in comparison with the unreinforced PDMS, proportionally to its concentration. The calculation of D and G bands ratio (ID/IG) at 1350 and 1580 cm−1 respectively, using RAMAN spectroscopy, showed more defects in graphene nanoplatelets incorporated in the PDMS nanocomposites. By Differential Scanning Calorimetry (DSC), a slight decrease in glass transition and melting temperatures of PDMS was observed. The thermal stability of composites was significantly improved, especially at higher GO concentrations (0.5 and 1 phr), as it was detected by thermogravimetric analysis (TGA). Also, the tensile strength of composites was enhanced, up to 113%, for samples reinforced with 1 phr GO. The elongation at break was increased, whereas no effect on the modulus of elasticity was observed. A decrease in oxygen permeability of 38% and 15% was measured in membranes made ofcomposites containing 0.5 phr and 1 phr GO respectively. The increase in swellingafter immersion of composites in toluene was explained by the fact that this phenomenon is not only related with the crosslinking density of the elastomer but alsowith the increased absorption properties of GO particles, due to the sonication treatment in THF during the preparation process of the composite, which might contribute to this effect.

Preparation by solution mixing and characterization of condensation type poly(dimethyl siloxane)/graphene nanoplatelets composites

The impact of the incorporation of graphene nanoplatelets (GN) on the properties of hydroxyl-terminated poly(dimethylsiloxane) (PDMS) matrices was investigated. The composites were prepared by solution mixing, using tetrahydrofuran (THF) as a solvent. Brookfield viscosimetry, implemented during the vulcanization process, revealed that GN increases the viscosity of the system, compared to pristine PDMS, proportionally to its concentration. X-ray diffraction patterns suggested an efficient dispersion of GN in the polysiloxane matrix. The D and G bands ratio (ID/IG) calculation, based on RAMAN spectra of GN/PDMS specimens, revealed more defects in graphene nanoplatelets when incorporated in the PDMS matrix. By differential scanning calorimetry (DSC), a marginal increase in crystallization, glass transition and melting temperatures of PDMS in GN/PDMS composites was observed. Improvement of the thermal stability of LMW PDMS composites, especially for higher GN concentrations (3 and 5 phr), was noticed by thermogravimetric analysis (TGA). Additionally, GN enhanced the tensile strength of composites, up to 73% for the 3 phr GN/LMW PDMS composite. A significant increase in the elongation at break was recorded, whereas no effect on the modulus of elasticity was recorded. The decrease in toluene-swelling, for the LMW PDMS matrix composites, was attributed to the increase in the tortuosity path because of the efficient dispersion of GN. A decrease in oxygen permeability of 55–65% and 44–58% was measured in membranes made of PDMS composites containing 0.5 phr and 1 phr GN, respectively. Dielectric relaxation spectroscopy (DRS) measurements recorded a significant increase in the conductivity of the higher graphene content composites.

Enhancing the mechanical and barrier properties of chitosan/graphene oxide composite films using trisodium citrate and sodium tripolyphosphate crosslinkers

AbstractThis study investigated the effect of ionic crosslinking on the mechanical, barrier, and optical properties of chitosan (CS) and CS/graphene oxide (CSGO) composite films using trisodium citrate (CIT) and sodium tripolyphosphate (TPP) solutions of different concentrations (0.5, 1.0. 2.0, and 3.0% w/v). Successful crosslinking was confirmed by Fourier‐transform infrared spectroscopy. The hydrophilicity and light transmittance decreased significantly (p < 0.05) with the increase in concentration of both crosslinking agents. The CS films crosslinked with 3.0% w/v TPP exhibited significant (p < 0.05) improvements in barrier properties, achieving a 51% decrease of water vapor permeability and 59% decrease in oxygen permeability, in comparison to neat CS film. In addition, TPP‐crosslinked CSGO films experienced an 82% and 42% improvement in tensile strength and elongation at break, respectively. Overall, crosslinked CS and CSGO films possess significantly improved properties and have great potential to be further studied as food packaging materials.

Antibacterial Activity of Polyvinyl Alcohol/WO3 Films Assisted by Near-Infrared Light and Its Application in Freshness Monitoring.

Nowadays, films with antibacterial activity and applied for freshness monitoring by colorimetric response have been drawing growing attention in food packaging. However, the development of versatile antibacterial and colorimetric agents is still highly desirable. Herein, WO3 nanorods are incorporated in a polyvinyl alcohol (PVA) matrix to develop a novel composite film with photothermal antibacterial activity and freshness monitoring faculty. The interaction between WO3 nanorods and PVA is due to hydrogen bonds. Compared with the PVA film, the presence of WO3 nanorods can significantly enhance the mechanical and barrier properties; typically, the target film (WO3/PVA)4 shows an increase in tensile strength by 52.7% and Young's modulus by 400.0% and a decrease in oxygen permeability by 72.4% and water vapor permeability by 66.9%. The films demonstrate a WO3 content-dependent antibacterial activity. Under irradiation of near-infrared light (NIR808), the synergistic effect of physical damage, oxidative stress, and temperature increase markedly improves the antibacterial activity of (WO3/PVA)4, showing an antibacterial efficiency of ∼90% against Escherichia coli or beyond 90% against Staphylococcus aureus. The incorporated WO3 nanorods demonstrate lower cytotoxicity toward the model cells of human colon cancer cell line HT-29. The (WO3/PVA)4 film exhibits colorimetric response to H2S and can also be used for pork freshness monitoring as an indicator.

Synergistic enhancement of gas barrier and aging resistance for biodegradable films with aligned graphene nanosheets

There is currently great interest in biodegradable alternatives for packaging and agricultural applications. The most viable biodegradable alternative, poly (butylene adipate-co-terephthalate) (PBAT), has poor resistance to water vapor and oxygen permeation and tends to degrade rapidly under solar exposure. Herein, we report a preparation of PBAT nanocomposite films with aligned graphene nanosheets both in and on the films by combining two techniques, biaxial orientation and rod scarping. The composite films with a graphene content of 0.48 vol% exhibited 80% decrease of water vapor permeability and over 99% decrease of oxygen permeability, approaching values of 1.0 × 10−11 g m m−2·Pa−1 s−1 and 6.2 × 10−16 cm3 cm cm−2·Pa−1 s−1. These values are respectively comparable to and even lower than the reported 9.9 × 10−12 g m m−2·Pa−1 s−1 and 8.0 × 10−15 cm3 cm cm−2·Pa−1 s−1 for polyethylene films. After a 200 h aging, the composite films still possessed a fracture strength of 47.3 MPa and an elongation at break of 167%, in contrast to a complete fragmentation of pure PBAT. We believe that the controlled incorporation of aligned graphene nanosheets to biodegradable polymers could become an important strategy to develop sustainable packaging and agricultural films.

Mussel-Inspired Approach to Constructing Dual Network Coated Layered Clay for Enhanced Barrier and Antibacterial Properties of Poly(vinyl alcohol) Nanocomposites.

Inspired by complexation and mussel adhesion of catechol groups in tannic acid (TA), organophilic layered double hydroxides (LDHs@TA-Ti) were synthesized by forming a one-pot assembled TA-titanium (Ti) dual network coating on the surface of layered clay for the first time. LDHs@TA-Ti/poly(vinyl alcohol) (PVA) nanocomposites were prepared by the solution casting method. The results show that TA-Ti(IV) and TiO2 coordination compounds are simultaneously formed due to hydrolysis of titanium tetrachloride and complexation of TA in aqueous solution. Upon TA-Ti coatings onto the surface of LDHs, the antibacterial rate of LDHs@TA-Ti is up to 99.98%. Corresponding LDHs@TA-Ti/PVA nanocomposites also show outstanding antibacterial properties. Compared with pure PVA, LDHs@TA-Ti/PVA nanocomposites show a 40.9% increase in tensile strength, a 17.5% increase in elongation at break, a 35.9% decrease in oxygen permeability and a 26.0% decrease in water vapor permeability when adding 1 wt % LDHs@TA-Ti. UV transmittance (at 300 nm) of LDHs@TA-Ti/PVA nanocomposites decrease by 99.4% when the content of LDHs@TA-Ti reaches 3 wt %. These results indicate that PVA matrix incorporated with LDHs@TA-Ti could be used as a potential active packaging material to extend the shelf life of food products.

High-Barrier and Antioxidant Poly(lactic acid)/Nanocellulose Multilayered Materials for Packaging.

In the current context, the development of bio-based and high-performance materials is one of the main research priorities. This study aims to combine the outstanding properties of cellulose nanofibrils (CNFs) or nanocrystals (CNCs) with those of bio-based poly(lactic acid) (PLA). Three-phase multilayered materials (TMLs) were built up by complexing a dry CNF- or CNC-based film with two PLA sheets, using a heat-pressing process. Before the preparation of the nanocellulosic films, CNFs and CNCs were modified by the adsorption of a rosin-based nanoemulsion. The rosin mixture as a natural compound is of interest because of its low cost, renewability, hydrophobicity, and its antimicrobial and antioxidant properties. After demonstrating the efficiency of the complexing procedure, we investigated the barrier properties of the multilayered materials against both oxygen and water vapor, with highly encouraging results. In fact, the presence of nanocellulose as an inner layer between the two PLA films significantly enhanced the oxygen barrier, with a decrease in oxygen permeability comprised between 84 and 96% and between 44 and 50% for neat nanocelluloses and nanocelluloses with rosins as the inner layer, respectively. On the other hand, the antioxidant properties of the final multilayered materials including rosins were highlighted, with a highly encouraging radical scavenging activity close to 20%. Because of the simplicity and the efficiency of the proposed method, this study paves the way toward the development of hybrid multimaterials that could be highly attractive for food packaging applications.

Two-Layer Functional Coatings of Chitosan Particles with Embedded Catechin and Pomegranate Extracts for Potential Active Packaging.

Two-layer functional coatings for polyethylene (PE) and polypropylene (PP) films were developed for the active packaging concept. Prior to coating, the polymer films were activated by O2 and NH3 plasma to increase their surface free energy and to improve the binding capacity and stability of the coatings. The first layer was prepared from a macromolecular chitosan solution, while the second (upper) layer contained chitosan particles with embedded catechin or pomegranate extract. Functionalized films were analyzed physico-chemically to elemental composition using ATR-FTIR spectroscopy and XPS. Further, oxygen permeability and wettability (Contact Angle) were examined. The antimicrobial properties were analyzed by the standard ISO 22196 method, while the antioxidative properties were determined with an ABTS assay. Functionalized films show excellent antioxidative and antimicrobial efficacy. A huge decrease in oxygen permeability was achieved in addition. Moreover, a desorption experiment was also performed, confirming that the migration profile of a compound from the surfaces was in accordance with the required overall migration limit. All these properties indicate the great potential of the developed active films/foils for end-uses in food packaging.

Phosphonated Poly(ethylene terephthalate) ionomers as compatibilizers in extruded Poly(ethylene terephthalate)/Poly(m-xylylene adipamide) blends and oriented films

Blends of poly(ethylene terephthalate) (PET) and poly(m-xylylene adipamide) (MXD6) were successfully compatibilized by using a phosphonated PET ionomer in the Na+ form (Na+-PPET) as a compatibilizer. The compatibilized 90:10 (by weight) polyester/polyamide blends containing various amounts of the phosphonated polyester were prepared by melt mixing in a twin-screw extruder. Scanning electron microscopy (SEM) revealed that the extruded blends contained spherical MXD6 domains dispersed in the PET matrix. The phase-separated MXD6 domain size decreased with increasing ionic monomer concentration, and the efficient compatibilization was attributed to specific interactions between the ionic phosphonate groups on the Na+-PPET ionomer and the amide linkages of MXD6. Thermal analysis suggested that the small MXD6 domains nucleated the crystallization of PET upon cooling as indicated by a shift of crystallization temperature of PET to higher temperatures. Furthermore, the specific interactions appeared to inhibit crystallization of MXD6. Biaxial orientation of melt processed films of the blends with a draw ratio of 3 × 3 transformed the spherical MXD6 domains into high aspect ratio platelets that were oriented in the plane of the film. Compared to the uncompatibilized base blends, optical property characterization on the oriented films revealed a decreased haziness by 56% and an improved transparency by 35% with 0.22 mol% of phosphonated ionic monomers incorporated in the polyester component. Moreover, a 33% decrease in oxygen permeability was found for the oriented Na+-PPET/PET/MXD6 blend composition containing 0.11 mol% of phosphonated monomers.

Effect of functionalized silica nanoparticles on the mass transfer process in active PLA nanocomposite films obtained by supercritical impregnation for sustainable food packaging

Nanocomposite films based on PLA with 1.0 % w/w silica nanoparticles (NP) and surface-functionalized silica nanoparticles with lactic acid (NP-LA), respectively, were obtained by extrusion process. Subsequently, cinnamaldehyde (ci) was incorporated through supercritical impregnation in the films at a pressure of 12 MPa, 40 °C temperature and 1.0 MPa min−1 depressurization rate. The developed materials were characterized on their thermal-mechanical, structural and barrier properties. Simultaneously, a phenomenological mass transfer was used to describe the release of cinnamaldehyde from the bionanocomposite in an aqueous food simulant (ethanol 10 % v/v solution). A 44 % decrease in oxygen permeability concerning the material without nanoparticles was checked as well as the plasticizing effect of cinnamaldehyde. Regarding the release of the active compound, the incorporation of functionalized nanoparticles NP-LA decreased the diffusion coefficient from 3.5·10−14 to 0.9·10−14 (m2/s), obtaining the filling effect of the silica nanoparticles, delaying the active compound release.

Influence of the dispersing agents to obtain polymer–clay nanocomposites processed in two-steps using thermokinetic mixer

Polymer nanocomposite performance depends not only on the compatibility between nanoparticles and polymer matrix, but also the sequence in which the nanoparticle is incorporated into the polymer and the compounding device applied. In this study, we report the morphology, oxygen permeability, thermal and mechanical properties of the polypropylene nanocomposites change due to the use of a thermokinetic mixer when specific preparation steps are followed based on the dispersing agents used. Two organically modified clays and dispersing agents were applied: montmorillonite and hydrotalcite; hydrogenated hydrocarbon resin and poly (propylene-g-maleic anhydride) as compatibilizer with different maleic anhydride content. For the nanocomposites containing montmorillonite, poly (propylene-g-maleic anhydride), with low maleic anhydride content and the hydrocarbon resin prepared using the thermokinetic mixer, a more efficient clay dispersion was achieved. As a result, an increase in mechanical stiffness (57% in the Young modulus), higher thermal stability and a decrease in oxygen permeability (58%) were obtained. However, samples prepared with hydrotalcite achieved a better distribution and dispersion by preparing directly on a twin-screw extruder. Wherein, higher mechanical stiffness (36% in the Young modulus) with reduction in the oxygen permeability (52%) was reached when poly (propylene-g-maleic anhydride) with low maleic anhydride content and the hydrocarbon resin were present. These results point to that by using the dispersing agents in combined with a proper mixing system is possible to improve polyolefin nanocomposite properties, increasing the range of application in the packaging industry.

Improvements in the oxygen barrier property of polypropylene nanocomposites

A nanocomposite consisting of polypropylene (PP)/nanoclay (montmorillonite) was prepared by means of a melt‐compounding process with the use of a twin‐screw extruder. Because of the complex dispersion of polar and hydrophilic clays that have many cations in the nonpolar and hydrophobic PP, amino‐silane was introduced to modify the surface of the clays. Also, to improve the compatibility of the modified nanoclay with PP, a PP‐graft‐maleic anhydride was used as a compatibilizer. From Fourier transform infrared spectroscopy analysis and the mechanical property test results, it was confirmed that the surface of the nanoclay was properly modified, and it was successfully dispersed in the PP matrix. The composite was investigated by electron microscopy to analyze its morphology and the degree of dispersion of the nanoclay. An analysis of oxygen permeability according to nanoclay content was performed, and it was found that the higher nanoclay content makes the decrease in oxygen permeability. In addition, a shelf‐life test was carried out to determine the relationship between decreased oxygen permeability and food preservation performance. The preservation performance of the food package prepared with the resin made in this study was improved because of the improvement in mechanical properties and oxygen barrier property.

High CO2 tolerance oxygen permeation membranes BaFe0.95-xCa0.05TixO3-δ

A high CO2-tolerance oxygen permeation membrane BaFe0.95-xCa0.05TixO3-δ (BFCT, x = 0.05–0.15) was designed and prepared. Single cubic perovskite phase can be maintained up to the doping level x = 0.15. The Ti substitution enhances significantly the CO2 tolerance and improve the structural stability under H2 containing atmosphere of BFCT materials. With increasing Ti doping level, the oxygen vacancy concentration decreases and the oxygen ion migration energy increases, leading to a slight decrease in oxygen permeability of BFCT materials. Nevertheless, the sample BaFe0.8Ca0.05Ti0.15O3-δ delivers a high oxygen permeation flux of 1.02mLmin−1cm−2 at 950°C for 1mm thick membrane. The Ti substitution alleviates the lattice oxygen loss and reduces the thermal expansion coefficient of BFCT. A combination study of experimental measurements and first principles calculation was conducted to advance the understanding of Ti effects on the electrical conductivity behavior in BFCT. The BFCT membranes show an excellent long-term operation stability. The high oxygen permeability, good structural stability under CO2 and reducing atmosphere make the BFCT (x = 0.15) a promising membrane for oxygen separation applications.

Modification of poly(ethylene terephthalate) (PET) using linoleic acid for oxygen barrier improvement: Impact of processing methods

ABSTRACTPoly(ethylene terephthalate) (PET) is commonly used in the packaging industry; however, there is considerable interest in reducing the rate of oxygen permeation through PET to extend product shelf life. One method being employed to improve oxygen barrier is the introduction of reactive compounds to bind the oxygen permeating through the polymer. This work investigates a naturally occurring oxygen scavenger, linoleic acid (LA), which was incorporated within blown PET bottles using two different processing schemes. The LA was incorporated within PET at 0.5% by weight using both by blending and reaction of carboxyl end of LA and hydroxyl end of PET. The effect of LA on the thermal, mechanical properties, and oxygen permeation were determined. There was a decrease in oxygen permeability for the PET/LA samples with little change in physical properties relative to base PET. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45023.

Synthesis, CO2-tolerance and rate-determining step of Nb-doped Ce0.8Gd0.2O2−δ–Pr0.6Sr0.4Co0.5Fe0.5O3−δ ceramic membranes

In this work, CO2-tolerant Ce0.8Gd0.2O2δ–Pr0.6Sr0.4Co0.5Fe0.5−xNbxO3−δ (CG–PSCF0.5−xNx; x=0–0.125) dual-phase dense oxygen permeation membranes were successfully developed. The crystal structure, microstructure, oxygen permeability, rate-determining step and CO2 tolerance were systematically investigated. The experimental results showed that the increase in CG content improved oxygen permeability and CO2 tolerance. Thermogravimetry–differential-scanning-calorimetry analysis, X-ray photoelectron spectra and oxygen permeation tests indicated that the increase in Nb content caused a slight decrease in oxygen permeability, while the long-term CO2 resistance can be improved significantly. According to the adopted permeation model, the weight ratio and thickness affect the oxygen permeability and permeation resistance distribution. By examining the distribution of three permeation resistances, we identified the rate-determining step and then optimized the weight ratio of the two phases, as well exploring the effects of thickness on oxygen permeability. All these experiments confirm that CG–PSCF0.5−xNx dual-phase membranes have great CO2 tolerance and potential application in oxy-fuel combustion.