Oxygen Permeability Coefficient Research Articles

Solo water-gelatinized starch enhances the barrier properties of starch/PBAT.

Glycerol-plasticized thermoplastic starch blending with biodegradable materials reduces costs and enhances toughness at the expense of deteriorating barrier properties. Herein, solo water-gelatinized corn starch (GCS) was melt-blended with polybutylene adipate terephthalate (PBAT) at 130 °C, and subsequent dehydration converted GCS into retrograded corn starch (RCS), yielding RCS-filled PBAT composites. As a barrier filler, RCS dispersed in smaller particles, combined with an interfacial compatibilizer, pentaerythritol monolaurate (PM), dramatically enhances the barrier properties. At 40 % RCS content, the oxygen permeability coefficient decreases to 0.78 × 10-15 cm3·cm/cm2·s·Pa, which is about one order of magnitude lower than that of neat PBAT. Meanwhile, the water vapor permeability coefficient, light transmittance, and haze are all comparable to neat PBAT. Although the mechanical properties of RCS-filled PBAT decreased, the tensile strength and elongation at break remained at 9.60 MPa and 462.19 % (30 % RCS), respectively. This work presents an innovative and cost-effective approach for starch-filled biodegradable polymers.

Development of a high-barrier, antimicrobial, and pH-sensitive nanocomposite film based on gellan gum/sodium carboxymethylcellulose/sodium alginate with nano-SiO2 for strawberry preservation and monitoring.

In this study, pH-responsive nanocomposite films with high barrier properties were obtained by the addition of a mixture of methyl red and bromothymol blue to the inner film and Silicon dioxide nanoparticles (nano-SiO2) to the outer film matrix. The incorporation of nano-SiO2 resulted in a notable reduction in the oxygen permeability coefficient and water vapor transmission rate, accompanied by an enhancement in the UV barrier and tensile strength. In comparison with the control sample (0 % nano-SiO2), the film containing 1 % nano-SiO2 exhibited a 57.1 % decline in the oxygen permeability coefficient, a 33.6 % rise in tensile strength, and a reduction in the water vapor permeability coefficient to 2.32 × 10-11 g-1s-1Pa-1. Meanwhile, the film with incorporated nano-SiO2 demonstrated enhanced thermal stability and augmented free radical scavenging capacity. The color of all films exhibited notable alterations in response to fluctuations in pH and CO2 concentrations. The application of a bilayer film to strawberry packaging allowed the freshness of the strawberries to be evaluated based on visible color change to the naked eye. The results of the experiment demonstrated that the addition of the nano-SiO2 film served to maintain the intrinsic physicochemical characteristics of the strawberries, while simultaneously extending their shelf life. In conclusion, the 1 % nano-SiO2 film has the potential for a wide range of applications.

Effect of poly(vinyl alcohol)-g-poly(lactic acid) on the oxygen barrier performance of poly(lactic acid)-based film.

In order to improve the oxygen barrier performance of poly(lactic acid) (PLA), a simple and economical melt blending method was chosen and poly(vinyl alcohol) (PVOH) with excellent oxygen barrier was used as the reinforcing phase to meet high oxygen needs. To improve compatibility, PLA was grafted onto PVOH through L-LA ring opening polymerization to get poly(vinyl alcohol)-graft-poly(lactic acid) (PVOH-g-PLA). The films with high oxygen barrier performance were prepared by blending PLA with PVOH-g-PLA. The structure of PVOH-g-PLA were characterized by FTIR and 1H NMR, where 58% -OH of PVOH grafted PLA and the average polymerization degree of the grafts was 8. The compatibility, crystallization, mechanical properties, and oxygen barrier performance of the blend films were studied. The results indicate that, compared with PVOH, PVOH-g-PLA has better compatibility with PLA. The PVOH-g-PLA separation phase size is <3μm, whereas the of PVOH separation phase size is 15-40μm. The oxygen permeability coefficient (PO2) of PLA/PVOH-g-PLA decreases with PVOH-g-PLA. When the amount of PVOH-g-PLA reaches 15%, PO2 decreases to 1.10×10-14cm3·cm/(cm2·s·Pa), 38% improvement in oxygen barrier compared to 1.77×10-14cm3·cm/(cm2·s·Pa) of neat PLA. These blends exhibited potential as a novel barrier material for food packages.

Preparation of exfoliated and dispersed thermoplastic starch/montmorillonite nanocomposites via synergy of phase‐transition and ultrasonic in elongational flow field

AbstractIn this study, a new mixing method and its principle via the synergy of phase‐transition and ultrasonic based on an elongational flow field were introduced in detail. Thermoplastic starch (TPS)/montmorillonite (MMT) nanocomposites from native corn starch were prepared using this novel method. The scanning electron microscope and x‐ray diffraction analyses confirmed that MMT can be efficiently exfoliated and dispersed evenly in the TPS matrix. Dynamic rheological analysis showed that exfoliated MMT obstructed starch molecular movement, increasing the viscosity and elasticity of TPS/MMT nanocomposites. Thermogravimetric analysis highlighted that evenly dispersed MMT enhanced the thermal stabilities of TPS/MMT nanocomposites. When the MMT content was 9 wt%, compared with nanocomposites prepared by melt blending alone, the tensile strength of TPS/MMT nanocomposites prepared by the new method increased from 5.8 to 14.3 MPa, and the oxygen permeability coefficient decreased from 13.43 × 10−15 cm3·cm/(cm2·s·Pa) to 5.52 × 10−15 cm3·cm/(cm2·s·Pa). This new method provided a promising pathway for the preparation of well‐exfoliated and evenly dispersed polymer‐based nanocomposites with excellent mechanical properties and barrier properties.Highlights A new mixing method based on the synergy of phase‐transition and ultrasonic in an extensional flow field for preparing exfoliated and dispersed TPS/MMT nanocomposites was proposed. The new method promoted the exfoliation and dispersion of MMT in the TPS matrix. The performance of TPS/MMT nanocomposites was significantly improved with the introduction of phase‐transition and ultrasonic.

Experimental Characterization of Biodegradable Films Based on Modified Starch and Chitosan

Gas transport and physico-mechanical properties of synthesized films based on modified starch and chitosan have been studied. The values of the permeability coefficients of pure gases included in the air for films based on modified chitosan and a copolymer based on modified starch and chitosan at a temperature of 23°C were determined. The oxygen permeability coefficient of the synthesized copolymer was compared with other polymers. A copolymer based on modified starch and chitosan was found to have medium oxygen barrier properties. The biodegradability of the samples under the action of the micromycete Aspergillus niger was studied by analyzing the degradation products by chromatography-mass spectrometry. The total biodegradation time of the samples was 4 weeks. These films are promising for use as packaging material.

Crystallization, Gas Barrier, and Mechanical Properties of Polypropylene Nanocomposites Reinforced by Graphite‐Like Carbon Nitride Nanosheets

ABSTRACTPolypropylene (PP) based nanocomposites with graphitic carbon nitride nanosheets (CNNSs) exfoliated from g‐C3N4 (CN) were fabricated via melt compounding. The detailed structure and morphology of the CNNSs were examined using X‐ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM), and atomic force microscopy (AFM) measurements. The effects of CNNSs on the crystalline morphology, oxygen vapor permeability, and mechanical properties of PP based nanocomposites were carefully evaluated. The CNNS not only increased the crystallization peak temperature and crystallinity, but also enhanced gas barrier properties and tensile strength of the PP nanocomposites. For PP/CNNS‐2 nanocomposites, the tensile strength was increased by 10.7%, and oxygen permeability coefficients decreased by 64.5% compared to pure PP. Therefore, PP/CNNS nanocomposite could be a potential candidate for packing application.

Preparation and characterization of nanocomposites based on natural rubber/chlorobutyl rubber/graphene nanoparticle: Effect of feeding sequences, mixer type and nanoparticle concentration

AbstractBlends of natural rubber (NR)/chlorobutyl rubber (CIIR) (50/50), along with their nanocomposites containing varying amounts of graphene nanoparticles (GNPs) with and without silane, were prepared using different feeding sequences and mixers. The results indicated that when GNP was first mixed with NR before adding CIIR, the highest GNP content was found in NR; the oxygen permeability and diffusion coefficient decreased significantly by 37% and 55%, respectively. Conversely, when graphene was initially added to CIIR, it was distributed in both rubbers and at the interface, enhancing phase interaction and achieving a finer morphology. This sample exhibited the greatest improvement in mechanical properties due to specific localization of GNP and increased crosslink density. Using an internal mixer instead of a two‐roll mill improved graphene dispersion, reduced curing time, and enhanced mechanical properties. Although the presence of silane reduced graphene dispersion, it improved mechanical and barrier properties due to increased crosslink density. Oxygen permeability was reduced by up to 36% at 3 phr of GNP content with silane. This research proves that the mixing order and the type of mixing equipment are crucial in determining the final performance of rubber composites, as they significantly influence the dispersion and localization of fillers.Highlights NR/CIIR/GNP nanocomposites were prepared by different methods and evaluated. Adding NR/GNP to CIIR led to more presence of GNP in NR and lower permeability. By adding CIIR/GNP to NR, GNP were placed more at interface, modulus improved. Mixing in an internal mixer improved GNP dispersion compared to a two‐roll mill. Silane improved mechanical and barrier properties of NR/CIIR/GNP nanocomposite.

Oxygen diffusion effects in thermo-oxidative degradation of typical tire rubber

Thermo-oxidative degradation of tire rubber has been demonstrated as a green method for upcycling waste tire rubber. However, the complicated tire compositions present challenges to achieving the homogeneity and efficiency of the reclaimed products, which restricts their widespread industrial adoption. To address this challenge, natural rubber(NR)and natural rubber/butadiene rubber(NR/BR)were innovatively designed to simulate complex tire compositions and investigate the influence of oxygen diffusion on thermo-oxidative degradation at 150–240 °C. The evolution of chemical structural changes and mechanical properties during degradation was traced by FTIR, UV–vis, and nanoindentation test. A basic reactive-diffusion model based on Fickian oxygen diffusion was used to simulate the diffusion profiles. It was found that recrosslinking decreases the oxygen permeability coefficient during NR/BR degradation as the temperature increases, making it difficult for oxygen to diffuse into the inner layer, and therefore tire rubber degrades unevenly. Lower temperatures and prolonged treatment times were recommended to enhance degradation. These findings provide substantial guidance for optimizing the recycling process of tire rubber and its sustainable utilization.

Poly (lactic acid)/Poly (butylene adipate-co-terephthalate) films with simultaneous high oxygen barrier and fast degradation properties

Although poly (lactic acid) (PLA) is a good environmentally-friendly bio-degradable polymer which is used to substitute traditional petrochemical-based polymer packaging films, the barrier properties of PLA films are still insufficient for high-barrier packaging applications. In this study, oxygen scavenger hydroxyl-terminated polybutadiene (HTPB) and cobalt salt catalyst were incorporated into the PLA/poly (butylene adipate-co-terephthalate) (PLA/PBAT), followed by melting extrusion and three-layer co-extrusion blown film process to prepare the composite films. The oxygen permeability coefficient of the composite film combined with 6 wt% oxygen scavenger and 0.4 wt% catalyst was decreased significantly from 377.00 cc·mil·m−2·day−1·0.1 MPa−1 to 0.98 cc·mil·m−2·day−1·0.1 MPa−1, showing a remarkable enhancement of 384.69 times compared with the PLA/PBAT composite film. Meanwhile, the degradation behavior of the composite film was also accelerated, exhibiting a mass loss of nearly 60% of the original mass after seven days of degradation in an alkaline environment, whereas PLA/PBAT composite film only showed a mass loss of 32%. This work has successfully prepared PLA/PBAT composite films with simultaneously improved oxygen barrier property and degradation behavior, which has great potential for high-demanding green chemistry packaging industries, including food, agricultural, and military packaging.

Fabrication of high performance poly(vinyl alcohol)/straw composite film used for package via melt casting and biaxial stretching

A high performance poly(vinyl alcohol)/straw (PVA/SP) composite film for package was fabricated in this study by using thermal processing technology of PVA established in our research group and biaxial stretching technology. The introduction of SP disrupted the original hydrogen bonds in modified PVA by forming new hydrogen bonds with the hydroxyl groups of each component in modified system, thus promoting the stable melt casting of PVA/SP composites and also endowing the obtained PVA/SP precursor sheets with good drawability. Upon biaxial stretching, SP reinforced the crystalline structure and orientation of PVA through their hydrogen bonds with PVA, improving the mechanical strength, crystallinity and thermal stability of PVA/SP films. The film with 3.0 × 3.0 stretching ratios demonstrated the exceptional tensile strength (62.2 MPa), tear strength (119.7 kN/m), low heat shrinkage (5.2 %), and oxygen permeability coefficient (1.38 × 10−16 cm3·cm/cm2·s·Pa), which surpassed most conventional plastic films used in food packaging field. This research not only pioneered an environmentally friendly packaging solution, but also offered a novel strategy for solid-state high-value, large-scale and economical utilization of waste crop straw, greatly avoiding the adverse effects of its burning on the environment.

The Effect of Fibrillation, Semi-Dry Pressing, and Surface Treatment on the Barrier Properties of Water Molecules and Oxygen on Food Packaging Paper.

The characteristics of fiber morphology and paper structure are critical to the barrier properties of food packaging paper. Herein, this study aimed to use pulp fibrillation, paper semi-dry pressing and carboxymethyl starch (CMS) coating to flatten the fibers, which were formed on the paper surface with good barrier properties due to the tight bond between fibers. The results showed that the permeability of paper was reduced by 87.56%, from 81.44 μm/Pa·s to 10.13 μm/Pa·s after the pulp fibrillation treatment (60 °SR). Moreover, semi-dry pressing treatment contributed to decreasing the water vapor transmission coefficient (WVP) by 50.98% to 2.74 × 10-10 g/m·s·Pa, and the oxygen permeation coefficient (OP) decreased by 98.04% to 1.93 × 10-14 cm3·cm/cm2·s·Pa. After coating the paper surface with titanium dioxide (TiO2) and CMS, the WVP of the paper was further reduced to 1.55 × 10-10 g/m·s·Pa, and OP was reduced to 0.19 × 10-14 cm3·cm/cm2·s·Pa. These values were 72.27% and 99.8% lower than those of the original paper, respectively. Therefore, through pulp fibrillation, semi-dry pressing of paper, TiO2 filling, and surface coating with CMS, there is no need to use synthetic polymer surface film-forming agents to achieve the high barrier properties that are required for low water and oxygen molecules permeation in food packaging paper.

Development of high barrier poly(l-actic acid)/chitosan/graphene oxide flexible films for meat packaging by layer-by-layer

An new high-barrier packaging films for meat preservation were obtained by depositing graphene oxide (GO) layer-by-layer (LbL) on poly(l-lactic acid)(PLLA)-poly (butylene itaconate) (PBI) copolymers (PLBI) with chitosan (CS) as bonding layer in this study. The 1H NMR results revealed that PLBI copolymer was successful synthesized. The introduction of PBI reduced the Tg and crystallization capacity of PLLA film, which made the copolymer films exhibit extremely high flexibility (up to 186.1% elongation at break). The film also exhibited high hydrophilicity, which was favorable for the effective attachment of CS. With CS as an intermediate layer, the FTIR and SEM results showed that the GO was evenly distributed onto the PLBI film surface due to the electrostatic interaction. The oxygen, water vapor and UV light barrier properties of PLBI/CS/(GO-CS)x films were improved and increased with the GO-CS layers. The PLBI/CS/(GO-CS)10 films, with extremely low oxygen permeability coefficients about 0.4 × 10−8 cm3 m/m2·h·Pa, delayed the increase in weight loss, hardness, pH, TVB-N, TBARS, and total viable counts of chilled meat during storage. It also decreased the discoloration, and loss of springness and cohesiveness of chilled meat caused by long-term refrigeration. The LbL films even showed better freshness-keeping effect than commercial PA/PE films due to its superior barrier and certain antibacterial properties, suggesting great potential application in fresh meat preservation.

Apple pectin-based active films to preserve oil: Effects of naturally branched phytoglycogen-curcumin host

Pectin has excellent film-forming properties, but its functional properties need to be enhanced. Therefore, we constructed naturally branched phytoglycogen (PG) nanoparticles to solubilize curcumin (CCM) and further enhance the properties of apple pectin-based active films. The size of the PG spherical particles ranged from 30 to 100 nm with some aggregates. The branch density of the PG was 6.02 %. These PG nanoparticles increased the solubility of CCM nearly 1742-fold and a nanosized phytoglycogen-curcumin (PG-CCM) host was formed via hydrogen bonding and hydrophobic interaction. This host promoted the formation of pectin-based films with a dense structure and increased their tensile strength to 23.51 MPa. The coefficient to water vapor permeability, oxygen permeability and carbon dioxide permeability were all decreased indicating their barrier performance were improved. Among them, the oxygen permeability coefficient decreased most, from 1.14 × 10−7 g·m−1·s−1 to 0.8 × 10−7 g·m−1·s−1. Also, the transmittance of the active film at 280 nm and 660 nm decreased to 0.65 % and 72.10 %. Antioxidant and antibacterial properties were significantly enhanced (P < 0.05). And the results showed this film was an excellent oil packaging material. The active film incorporating PG-CCM host can replace heat-sealed plastic bags/pouch made from polyethylene and polypropylene synthetic plastics, and solve the problem that plastic packaging is difficult to degrade and cannot be squeezed clean. This provides a new conceptual framework for developing pectin-based active films by incorporating of PG and CCM.

Proton Transport, Electroosmotic Drag and Oxygen Permeation in Polytetrafluoroethylene Reinforced Ionomer Membranes and Their Effects on Fuel Cell Performance

Abstract With the increasing need for high power density of proton exchange membrane fuel cells, new composite membranes have been explored for superior proton transport and gas impermeability. These membranes’ physicochemical properties usually deviate from existing empirical formulas, which are poorly understood, especially when mechanical deformation occurs. This poor understanding hinders development of novelty membranes and their fuel cell applications. Here, using polytetrafluoroethylene reinforced ionomer membrane as an example, we conducted extensive water absorption experiments to determine hydration levels at different water activities. Molecular dynamics simulations and electrochemical impedance spectroscopy were used to investigate the impacts of hydration level, external electric field strength, and tensile deformation on proton transport and electroosmotic drag coefficient, as well as the impact of hydration level and free volume ratio on oxygen permeability. We proposed mathematical correlations for these impacts and incorporated them into a single-cell voltage model to analyze their effects on fuel cell performance. Results show that an increase in the electric field strength alters the proton transport pattern, but has minimal impact on the electro-osmosis coefficient. The oxygen permeability coefficient of a deformed membrane with a free volume ratio of 28.57% is more than two orders of magnitude higher than that of a non-deformed membrane. The electro-osmatic drag coefficient imposes a larger influence on fuel cell performance than oxygen permeability

Polyethylene terephthalate bottles with excellent oxygen, water vapor barrier and mechanical performances prepared by injection and blow molding

AbstractIn this work, the oxygen barrier property of polyethylene terephthalate (PET) films was enhanced by optimizing the “active” and “passive” synergistic barrier approaches, that is, integration of high barrier material polyethylene naphthalate (PEN) and oxygen scavengers along with catalyst with PET before biaxially stretching the PET blended films. When the PEN content in the PET blended films reached 50 wt%, the oxygen permeability coefficient was significantly reduced to 0.9687 cc·mil·m−2·day−1·0.1 MPa−1, showing an enhancement of 117.4 times compared to the pure PET film. Furthermore, the water vapor permeability coefficient was reduced to 8.0208 g·mil·m−2·day−1, representing a 45.5% reduction in comparison to the pristine PET film. It also maintained a higher transverse and longitudinal tensile strength (110.5 and 127.2 MPa) than PET film only with oxygen scavengers and catalyst (53.5 and 78.0 MPa). This work presents a viable and practical approach to endow PET materials with simultaneously enhanced oxygen, water barrier performance, and mechanical property.Highlights The OPC of PET film was as low as 0.9687 cc·mil·m−2·day−1·0.1 MPa−1. The “active” and “passive” barrier techniques together reduced the OPC of PET film.

Gas-permeable fluorine-substituted poly(diphenylacetylene)s: Effect of number and position of fluorine atoms on gas permeability

Poly(diphenylacetylene)s are ideal for fabricating gas-permeable membranes in gas separation systems. We previously reported the superior gas permeability of fluorine-substituted poly(diphenylacetylene)s compared to their fluorine-free counterparts. In this study, novel poly(diphenylacetylene)s were synthesized by varying the number of fluorine atoms from three to five in the repeating unit (2a, 2b, and 2c). Comparing the gas permeability for 2a–c, the highest value was achieved for poly(diphenylacetylene) with three fluorine atoms in a repeating unit (2a). The oxygen permeability coefficient was 8,100 barrers for 2a, remarkably higher than that of the previously reported poly(diphenylacetylene) with two fluorine atoms in the repeating unit. The density and X-ray diffraction analyses revealed a decrease in the free volume of the membranes with an increase in the number of fluorine atoms. Additionally, 2a–c did not show desilylation because the trimethyl silyl groups were substituted on the benzene ring possessing an electron-withdrawing fluorine atom.

Thymol@Natural Zeolite Nanohybrids for Chitosan/Polyvinyl-Alcohol-Based Hydrogels Applied as Active Pads.

Currently, food saving, a circular economy, and zero environmental fingerprints are of major interest. Scientific efforts for enhanced food preservation using "green" methods have been intensified. Even though chemicals could achieve such targets effectively, the global trend against the "greenhouse effect" suggests the use of environmentally friendly biobased materials for this purpose. In this study, the promising biopolymer chitosan is incorporated with the promising biodegradable polymer polyvinyl alcohol to produce an improved biopolymeric matrix. This biodegradable biopolymer was further mixed homogeneously with 15% thymol/nano-zeolite nanohybrid material. The properties of the final developed film were improved compared to the relevant values of chitosan/polyvinyl alcohol film. The mechanical properties were enhanced significantly, i.e., there was a 34% increase in Young's modulus and a 4.5% increase in the ultimate tensile strength, while the antioxidant activity increased by 53.4%. The antibacterial activity increased by 134% for Escherichia coli, 87.5% for Staphylococcus aureus, 32% for Listeria monocytogenes, and 9% for Salmonella enterica. The water vapor diffusion coefficient and the oxygen permeability coefficient decreased to -51% and -74%, respectively, and thus, the water vapor and oxygen barrier increased significantly. The active pads were used in strawberries, and the antimicrobial activity evaluation against the mold of fungi was carried out. The visual evaluation shows that the active pads could extend the shelf life duration of strawberries.

Crystallization behavior analysis and reducing thermal shrinkage of poly(lactic acid) miscibilized with poly(butylene succinate) film for food packaging

AbstractPoly(lactic acid) (PLA) incorporated with poly(butylene succinate) (PBS) through in situ reactive blending is proposed to retard thermal shrinkage. Succinic anhydride (SA) with varied contents (0.01–0.5 phr) was used as a reactive compatibilizer to enhance miscibility between PLA and PBS phases. The success of PLA chemically bound with PBS chains through simple esterification to form PLA‐SA‐PBS phase is confirmed and quantified using an X‐ray photoelectron spectroscopy technique. The binding energy intensity ratio of ester and hydrocarbon in the PLA/PBS/SA blend with 0.5 phr SA increases for two‐fold, as compared to the PLA/PBS blend. The good interfacial adhesion of PLA and PBS phases is achievable with SA content up to 0.1 phr. In addition, the PLA‐SA‐PBS molecules preferentially support crystallization of PBS phase with increased degree of crystallinity (Xc,PBS) by ~15%. These enhanced homogeneity of PLA/PBS/SA blend and high Xc,PBS trigger the increased tensile strength to 50 MPa, and substantially reduced oxygen permeation coefficient approximately 10 times. Remarkably, the interpenetration of PLA‐SA‐PBS phase in amorphous PLA region coexisting with uniformly dispersed PBS crystals inhibits the PLA chain relaxation and deformation at elevated temperatures, leading to maintaining dimensional stability of PLA/PBS/SA films without shrinkage at 100°C.

Oxygen permeability of regenerated cellulose films with different water regains

The effect of water regain on the oxygen permeability coefficient (OP) of regenerated cellulose film was investigated. The OP of the dry film was extremely low, which was classified as a “very high” performance gas barrier; however, the OP increased with increasing water regain, and reached to the OP similar to that of low-density polyethylene film, which was categorized as a “poor” gas barrier. The film thickness increased with increasing water regain, and edge-view small-angle X-ray scattering revealed widening of the space between microcrystals in the thickness direction. Oxygen molecules likely passed through the space between cellulose molecules, which was widened with increasing water regain. The viscoelastic measurements indicated that regenerated cellulose existed in a rubbery state under wet conditions. Overall, the OP of regenerated cellulose was increased because of the widening and micro-Brownian motion of cellulose main chains caused by water.

Morphological evolution ofTMB‐5/ethylene–vinyl alcohol copolymer blends under biaxial‐stretching field and its effect on the crystallization and gas barrier properties of isotactic polypropylene

AbstractThe morphological evolution of TMB‐5/ethylene–vinyl alcohol (EVOH) copolymer blends under biaxial‐stretching field and its effect on the crystallization and gas barrier properties of isotactic polypropylene (iPP) were investigated. iPP/TMB‐5/EVOH ternary blends with TBM‐5 selectively distributed in the EVOH phase were prepared through a multistage stretching extrusion, which combined an assembly of layer multiplying elements (LMEs) with an extruder. Scanning electron microscopy revealed that the biaxial‐stretching field in LMEs transformed the TMB‐5/EVOH phase into platelets along the extrusion direction. Differential scanning calorimetry and X‐ray diffraction results indicated that the TMB‐5 particles were distributed in the EVOH phase and noβcrystals formed in as‐extruded samples. Especially, the TMB‐5 was released from the EVOH phase into iPP in the annealing process and induced the formation ofβcrystals. Compared with that of pure iPP, the oxygen permeability coefficient of iPP containing aligned TMB‐5/EVOH platelets decreased more than three times. The enhanced barrier properties resulted from the increased tortuosity of the diffusion pathway caused by the orientated high‐aspect‐ratio platelets. © 2023 Society of Industrial Chemistry.