Excellent Gas Barrier Properties Research Articles

Design of Carboxylic Acid‐Functionalized Poly(Butylene Adipate‐co‐Terephthalate) for Recyclable and Biodegradable Zero‐Waste Paper Packaging

AbstractDemand for water‐ and oil‐repellent‐coated paper as an alternative to plastics is growing, but the challenge is that coated paper lacks concurrent recyclability and biodegradability. Reported herein is a novel carboxylic acid‐functionalized poly(butylene adipate‐co‐terephthalate) (CPBAT) copolymer investigated for recyclable and repulpable water‐borne paper coatings. The CPBAT synthesized here is characterized by spectroscopic methods. Paper coated with waterborne CPBAT exhibited excellent water, oil, moisture, and gas barrier properties suitable for packaging applications. The recyclability and repulpability of the CPBAT‐coated paper are successfully validated via certified TAPPI methods. This work demonstrates the first successful preparation of coated paper that is per‐ and polyfluoroalkyl substances (PFAS)‐free, recyclable, and biodegradable, with significant benefits for the environment and human health.

Flexible and Recyclable Bio-Based Polyester Composite Films with Outstanding Mechanical and Gas Barrier Properties Using Leaf-Shaped CNT@BNNS Covalent Heterojunction.

With the depletion of petroleum resources, the development of sustainable alternatives for plastic substitutes has grown in importance. It is urgently desirable yet challenging to design high-performance polyesters with extensive mechanical and prominent gas barrier properties. This work uses bio-based PBF polyester as a matrix, "leaf-shaped" carbon nanotube@boron nitride nano-sheet (CNT@BNNS) covalent hetero-junctions as functional fillers, to fabricate CNT@BNNS/PBF (denoted as CBNP) composite films through an "in-situ polymerizing and hot-pressing" strategy. The covalent CNT "stem" suppresses the re-stacking of BNNS "leaf", endowing hetero-structured CNT@BNNS illustrates superior stress transfer and physical barrier effect. The covalently hetero structure and high orientation degree of CNT@BNNS greatly improve the comprehensive performance of the CBNP composites, including excellent mechanical (strength of 76MPa, modulus of 2.3GPa, toughness of 85MJm-3, elongation at break of 193%) and gas barrier (O2 of 0.015 barrer, and H2O of 1.1 × 10-14g cm cm-2s-1Pa-1) properties that are much higher than for pure PBF or other-type polyesters, and most engineering plastics. Moreover, the CBNP composites also boast easy recyclability, overcoming the tradeoff between high performance and easy recycling of traditional plastics, which makes the polyester composite competitive as a plastic substitute.

Poly(butylene 2,5-thiophenedicarboxylate-co-glycolate) copolyesters with good degradation and barrier properties

In this work, poly(butylene 2,5-thiophenedicarboxylate-co-glycolate) (PBTFGA) copolyesters were synthesized from 2,5-thiophenedicarboxylic acid, 1,4-butanediol and glycolic acid. The influence of the glycolic acid content on thermal properties, mechanical properties and degradation capacity of copolyesters was systematically investigated. The glass transition temperature of copolyesters closely matched that of poly(butylene 2,5-thiophenedicarboxylate) (PBTF). While also demonstrating good thermal stability. When the glycolic acid content was low, the copolyesters exhibited some crystallization capability, but they gradually became fully amorphous as the glycolic acid content increased. The tensile tests revealed that the young's modulus of the PBTFGA copolyesters ranged from 69.2 MPa to 221.4 MPa. With elongation at break exceeding 659%, outperforming most biodegradable packaging materials. Copolyesters exhibited excellent gas barrier properties to both oxygen (PO2 = 0.024 barrer) and carbon dioxide (PCO2 = 0.029 barrer), both of which are superior to poly(butylene 2,5-thiophenedicarboxylate). The incorporation of glycolic acid significantly reduced the crystalline content of the copolyesters, facilitating the interaction of water molecules with ester bonds in the polymer backbone. The weight of poly(butylene 2,5-thiophenedicarboxylate-co-glycolate) was decreased significantly during enzymatic hydrolysis, indicating excellent degradation performance

High thermal resistance biobased copolyester from 2,5-Thiophenedicarboxylic acid with excellent gas barrier properties

Driven by sustainable development strategies, bio-based polyesters have received significant attention due to renewable bio-derived monomers and various unique properties. In this study, a series of high molecular weight bio-based poly(ethylene-co-2,2,4,4-tetramethyl-1,3-cyclobutylene thiophenedicarboxylate) (PETTh) copolyesters on the basis of an emerging bio-derived aromatic diacid, 2,5-thiophenedicarboxylic acid (TDCA), was synthesized by a conventional two-step melt polycondensation method. Copolymers were random copolyesters with weight-average molecular weights (Mw) in the range from 65,400 to 84,100 g/mol. Their comprehensive properties, including thermal transition properties, thermal stability, mechanical properties, gas barrier properties, as well as optical transparency were systematically investigated. Rigid 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) cyclic diol contributed a positive effect to thermal resistance, leading to the glass transition temperature (Tg) growing from 65.3 °C of PETh to 85.3 °C of PET42Th. Furthermore, the mechanical properties, gas barrier properties and optical transparency were improved as diol segment was incorporated. Especially, all copolyesters displayed great ductility with elongation at break between 54 and 195 %. Meanwhile, the gas barrier properties of copolyesters were 3.9-fold to 16.3-fold for CO2 and 3.0-fold to 6.0-fold for O2 better than PET. Therefore, PETTh copolyesters might potentially substitute for commercial PET and they are extremely suitable for food packaging materials.

Energy-efficient and directional preparation of cellulose nanosheets by one-pot surface modification assisted swelling method

The energy-intensive and time-consuming process required for disassembling natural materials into nanoblocks are the major obstacles for the practical applications of biopolymer nanomaterials. Herein, a one-pot, energy-efficient and directional preparation method for gently exfoliating cellulose into nanosheets was achieved by surface modification assisted swelling process. The resulting cellulose nanosheets (CNSs) exhibited diameters ranging from 100 to 480 nm and thicknesses of approximately 5 nm, with a maximum yield of 97.9 %. This method could be widely applicable to common cellulose raw materials. Contrary to other nanocellulose reported previously, CNSs could be dried and stored in solid state, and re-dispersed in aqueous phase, thereby convenient for storage and transportation. Cellulose nanosheets films (CNSFs) obtained from CNSs showed high transparencies (>90 %) and excellent gas barrier properties, especially for the water vapor permeability of only 0.0072×10−10 cm3 cm cm−2 s−1 Pa−1, which were superior to other cellulose based films. In the simulation experiment of dry food packaging, CNSF10 possessed remarkable water vapor and oxygen blocking capabilities comparable to commercial cling films and met the practical requirements. The preparing process of CNSs reported here had the advantages including easy implementation, energy efficiency, and environmentally friendliness, and expanded possibilities for large-scale and widespread utilization of nanocellulose.

Recoverable and degradable carboxymethyl chitosan polyelectrolyte hydrogel film for ultra stable encapsulation of curcumin

Hydrogels have shown great potential for application in food science due to their diverse functionalities. However, most hydrogels inevitably contain toxic chemical cross-linking agent residues, posing serious food safety concerns. In this paper, a curcumin/sodium alginate/carboxymethyl chitosan hydrogels (CSCH) were prepared by self-assembly of two oppositely charged polysaccharides, carboxymethyl chitosan and sodium alginate, to form a three-dimensional network encapsulating curcumin for extending food shelf life. The network structure of the CSCH film confirmed by FTIR, XRD, and XPS was mainly formed by electrostatic interactions. The chemical stability of CSCH network encapsulated curcumin was 4.2 times greater than that of free curcumin, with excellent gas barrier, antimicrobial, antioxidant, and biosafety properties. It was found that CSCH films reduced dehydration, prevented nutrient loss, inhibited microbial growth, and lowered the respiration rate, which effectively maintained the quality of mango and prolonged its shelf-life up to 11 days. Notably, CSCH films possessed the properties of rapid recycling (10 mins) and biodegradability (53 days). This polysaccharide-based hydrogel film provides a viable strategy for the development of green and sustainable food packaging.

Silica aerogel-PVA dough: A high internal phase composite with superior thermal insulation and gas barrier

Silica aerogel (SA) has shown great promise in constructing thermal insulation composites in various forms. However, it is still challenging to disperse a huge amount of SA particles into other matrices for fabricating superior thermal insulation materials or highly filled masterbatch, owing to its high specific surface area and ultra-low density. Herein, inspired by high internal phase emulsion (HIPE), we successfully prepare processable SA/polyvinyl alcohol (PVA) composites (SA-PVA dough) with over 74 vol% dispersed SA, using a PVA aqueous solution as a binder. This is achieved by gradually mixing a large amount of hydrophobic SA filler into a small amount of PVA aqueous solution. The resulting SA-PVA dough exhibits an internal structure resembling that of HIPEs, with hydrophobic SA particles stabilized in the water phase by amphiphilic PVA chains, tightly packed within the thin continuous PVA aqueous phase. Benefiting from such a HIPE structure, the SA-PVA dough can be easily shaped into various forms and exhibits good applicability in further processing. The dried dough inherits the excellent properties of SA, including ultra-low density, superhydrophobicity (water contact angle: 153°), thermal insulation (thermal conductivity: 0.03 W m−1 K−1), and flame resistance. Moreover, the continuous PVA network structure, combined with the nanoscale pore structure of SA, provides the dough with excellent gas barrier properties, greatly expanding the application scope of SA-based composites.

High Barrier Properties of Butyl Rubber Composites Containing Liquid Rubber and Graphene Oxide.

The high elasticity and excellent gas barrier properties of rubber composites make them irreplaceable in the field of sealing. Constructing a complicated barrier network to reduce free volume is crucial to improving gas barrier properties. In this research, liquid acrylonitrile-butadiene rubber/γ-Methacryloxypropyl trimethoxy silane (KH570) modified graphene oxide/butyl rubber composites (LNBR/KGO/IIR) were fabricated. A KGO lamellar network was constructed to resist gas diffusion in the IIR matrix. Meanwhile, LNBR macromolecules further occupied the free volume inside the IIR composites, thereby maximizing the retardation of the path of small molecule gas permeation. The modification of GO by KH570 was successfully demonstrated through FTIR and XRD. The grafting rate of KH570 was calculated to be approximately 71.4%. KGO was well dispersed in IIR due to emulsion compounding and the formation of lamellar networks. The 300% modulus, tensile strength and tear strength of KGO/IIR were improved by 43.5%, 39.1% and 14.8%, respectively, compared to those of the IIR composite. In addition, the introduction of LNBR resulted in a 44.2% improvement in the gas barrier performance of nitrogen permeability relative to the original IIR composite.

Fabrication of flame retardant nylon 6 film composites with superior gas barrier property and puncture resistance

Developing a flame retardant and puncture resistant nylon 6 (PA6) film composite with excellent gas barrier property as a food packaging material is still a great challenge. Herein, microencapsulation and hydrogen-bonding interaction were adopted to synthesize a multifunctional additive (SiO2@CS@GO-S), which simultaneously improved the mechanical, gas barrier and flame retardant performances of PA6 film. The obtained results indicated that the gas barrier property of the as-prepared PA6 film composite containing 0.1 wt% SiO2@CS@GO-S (PA6/SiO2@CS@GO-S-0.1) was obviously improved. For instance, the oxygen transmission rate of the film composite decreased dramatically by 52.0% compared with that of PA6 film. Furthermore, the puncture resistance of the PA6/SiO2@CS@GO-S-0.1 markedly increased from 18.3 N of PA6 to 25.3 N. Additionally, both thermal stability and fire safety of the PA6/SiO2@CS@GO-S film composites were enhanced. The peak of heat release rate and total smoke release of the PA6/SiO2@CS@GO-S-0.1 were reduced by 10.7% and 19.3%, respectively, compared to those of PA6 film. This work provides a new paradigm for creating a multifunctional PA6 film composite with high performance for grain preservation and loss reduction.

In-situ constructing hybrid cross-linked networks in brominated butyl rubber via amphiphilic graphene oxide cross-linkers: Retaining excellent gas barrier and mechanical properties after fatigue

Rubber/graphene nanocomposites as gas barrier materials have attracted great interest in recent years. However, it is still a challenge to construct strong covalent interfaces between nonpolar rubber matrix and graphene for retaining excellent gas barrier and mechanical properties of aircraft tires after fatigue. In this work, hybrid cross-linked networks in brominated butyl rubber (BIIR) are first proposed and in-situ constructed successfully via introducing the amphiphilic graphene oxide cross-linkers (R-aGO). R-aGO can participate in the curing of BIIR to form hybrid cross-linked networks, which can force R-aGO to move with BIIR synchronously during fatigue deformation due to strong interfaces between BIIR and R-aGO via covalent bonds. When R-aGO content is 3 phr, the BIIR/R-aGO nanocomposites show a 27 % improvement in gas barrier property, a 230 % increase in strength at 40 % strain (suffered deformation of aircraft tires), and a 229 % enhancement in tensile strength relative to conventional BIIR/aGO nanocomposites with interfacial modifiers. More importantly, BIIR/R-aGO nanocomposites still retain excellent gas barrier and mechanical properties even after 500,000 load cycles (40 % strain). This work provides a novel route to fabricate rubber/graphene nanocomposites with superior gas barrier and mechanical properties, especially after fatigue.

High-performance chemically recyclable multifunctional polyolefin-like biomass-derived polyester materials.

Polyolefins are the most widely used and produced petroleum-based plastics. Unfortunately, the enormous production and usage of traditional polyolefins, coupled with the lack of effective disposal or recycling options, have led to significant fossil fuel depletion and severe environmental pollution. To foster sustainable societal development, there is an urgent need to design high-performance and inherently recyclable polyolefin-like bio-derived materials by innovative structural and molecular designs. Here, inspired by a copolymerization molecular design approach that simultaneously confers recyclability and superior properties to materials, high-performance recyclable polyolefin-like bio-derived polyesters (PBCxS) enabled by a novel judicious combination of building blocks are reported. PBCxS display excellent mechanical (40.6 MPa, 498.4%) and gas barrier properties (O2 0.09 barrer, H2O 1.70 × 10-13 g cm cm-2 s-1 Pa-1), even greater than those of bio-based materials and most aliphatic polyester. Meanwhile, PBCxS also exhibit multifunctionality with excellent biocompatibility properties and ultra-high processability (thermoforming, extrusion spinning, and 3D printing processing). Notably, PBCxS undergo depolymerization in the absence of any additional organic solvents, regenerating 92.0% of the high-purity (98.3%) original monomers, even with polyolefin blend plastics. Repolymerized polyesters still maintain their exceptional mechanical and thermal qualities. The successful application of this approach in polyesters opens up exciting possibilities for designing high-performance and recyclable bio-derived polyolefin-like materials.

Supramolecular cross-linking affords chitin nanofibril nanocomposites with high strength and water resistance

Polysaccharide nanofibrils of chitins or celluloses are emerging biobased building blocks for sustainable, high-performance bioinspired nanocomposites fusing high stiffness, strength, and other functionalities. Owing to their hygroscopicity, a crucial challenge towards real-life applications of these nanocomposites is to maintain their mechanical performances in the humid or even fully swollen conditions. Here, we report water resistant nanocomposites composed of sustainable chitin nanofibrils (ChNFs) and polyvinyl alcohol (PVA) that are physically cross-linked by tannic acid (TA) to enhance and stabilize wet mechanical properties. We demonstrate that the formation of polymer-coated core/shell nanofibrils at the intermediate stage is crucial for the well-defined nanopaper structures after casting. By infiltrating TA, the formation of hydrogen bonding in the PVA matrix and at the ChNF/PVA interface renders the nanocomposites with extremely high strength and stiffness, even under high humidity and swelling conditions. With the increase in the amount of conjugated TA, the Young's modulus and tensile strength of the swollen nanocomposites reach up to 3.0 GPa and 70 MPa, respectively, which are superior to the existing water-borne nanofibils/polymer nanocomposites. Moreover, the nanocomposite films show excellent gas barrier properties at high relative humidity (90%), as well as UV shielding, antibacterial properties and biodegradability, complementing the multifunctional property profile and allowing a transfer into applications as advanced packaging materials.

A synergy of atmospheric plasma and UV-additive incorporated PU and styrene–isoprene-styrene adhesive for improving inter-layer adhesion in PVF/Fabric/BOPET laminate for aerostat envelope

Engineers and material scientists face a significant challenge in finding the right adhesive and technology to join the layers of a multi-layered laminated composite for making lightweight aircrafts. This paper focuses on a novel method of exposing substrates to atmospheric-plasma using different purging gases and subsequent adhesive-lamination. Three separate plasma-exposed layers— polyvinyl fluoride (PVF) film, polyester fabric, and biaxially oriented polyethylene terephthalate (BOPET) film were joined together using two different solvent-borne/pressure-sensitive adhesives, based on polyurethane and styrene-isoprene-styrene. Both adhesives were compounded with organic UV-additives and nano-carbon black for improving weather resistance. The composite laminates were exposed to accelerated weathering for 100h to qualify for the targeted application of aerostat envelope/hull. Among different gas combinations, the helium/oxygen-mixture (80:20) showed the best results in terms of surface etching/functionalization, which strongly attributed to improving adhesion-strength. Among two adhesives, styrene-isoprene-styrene-based adhesive performed much better. This adhesive was UV-cured after post-weathering cycle, and it improved inter-laminar adhesion strength by 81% and reached 16.2 N/cm. As a consequence, it prevented adhesive breakage from the weak bond layers and turned it into a cohesive failure from the adhesive layer. Most importantly, the laminated fabric showed excellent helium gas barrier property, which improved further after weathering cycle, making it ideal for the targeted application.

Bio-based high gas barrier polyesters based on furandicarboxylic acid: Trade-off between ethylene and propylene diols

A series of bio-based poly(ethylene-co-propylene furandicarboxylate) (PEPF) copolyesters with different compositions were synthesized from dimethyl-2,5-furandicarboxylate, ethylene glycol and 1,3-propanediol by transesterification and melting polycondensation. Their chemical structure, composition and sequence distribution were confirmed by 1H NMR and 13C NMR. The results of GPC showed that the obtained copolyesters had a high number average molecular weight between 25000 g/mol and 30900 g/mol. The thermal properties characterized by DSC showed that the Tg increased with the mole fraction of EF from 64.4℃ for PEPF-23 to 83.2℃ for PEPF-84 as well as the samples displayed a high Young's modulus between 2800 and 3360 MPa and tensile strength between 56 and 89 MPa. Furthermore, the PEPF copolyesters exhibited excellent CO2, O2 and H2O barrier properties compared with poly(ethylene terephthalate) with the BIFp of 8.7–10 times, 3.7–4.4 times and 1.5–1.6 times, respectively. The transparency of PEPFs was up to 89% by cutoff at 700 nm and had better solvent resistance. This work builds a bridge between poly(ethylene 2,5-furandicarboxylate) and poly(propylene 2,5-furandicarboxylate) and PEPFs owned excellent thermo-mechanical and gas barrier properties could be used in food packaging fields.

Towards ductile and high barrier poly(L-lactic acid) ultra-thin packaging film by regulating chain structures for efficient preservation of cherry tomatoes

The irreconcilable paradox between barrier performance and ductility is a “stumbling block” restricting the development of poly(L-lactic acid) (PLLA) films in the packaging industry. In this work, we reported the fabrication of an ultra-thin PLLA-based film with barrier properties and ductility by adjusting the polarity and conformational behavior of the polymer chains. Firstly, a novel unsaturated poly(L-lactic acid-co-butyrate itaconate) P(LA-BI) copolymer containing CC double bonds was synthesized using melt polycondensation. The results reveal that the addition of 60 % of P(LA-BI) enables PLLA film to achieve an elongation at a break of 83.6 % due to P(LA-BI) containing partially branched structures, which resulted in the polymer chains being arranged more in a high-energy gg conformer. Meanwhile, because of the large number of CO polar groups in P(LA-BI), PLLA/P(LA-BI)60 film show CO2 and O2 permeability coefficients (CDP and OP) of 1.8 and 0.45 × 10−8 g·m·m−2·h−1·Pa−1 respectively, which means that it has excellent gas barrier properties. Moreover, PLLA/P(LA-BI)60 film shows a 33.3 % increase in CO2/O2 ratio and an excellent ultraviolet (UV) barrier performance compared to neat PLLA. Preservation results suggested that the CO2 and O2 levels within the package could be regulated by varying the amount of P(LA-BI) added. Among them, PLLA/P(LA-BI)40 film generated a more desirable CO2 and O2 atmosphere for cherry tomatoes preservation, which was reflected by the delaying of senescence, discoloration, and decay, inhibition of oxidative cell damage through reduced malondialdehyde production, and maintenance of nutritional and flavor substances in cherry tomatoes. This PLLA-based film offers the advantages of operational simplicity, environmental friendliness, and inexpensive cost, making it great promising for food preservation and other applications requiring barrier properties and ductility.

Bioinspired polyimide film with fire retardant and gas barrier properties by gravity‐induced deposition of montmorillonite

AbstractFlame retardants play a crucial role in improving the flame retardant properties of polymer materials. In recent years, environmental problems caused by flame retardants have attracted widespread attention. It is urgent to use green and effective methods to prepare flame retardant polymers. Bioinspired nanocomposites with layered structures seem to provide effective ideas, but in general, their hydrophilic raw materials limit their applications in certain fields. Here, we prepared biomimetic composites with a layered “brick‐and‐mortar” structure by gravity‐induced deposition using polyimide as the polymer matrix and montmorillonite (MMT) as the filler. The well‐arranged structures of the composite material could isolate oxygen and prevent combustible gases from escaping. The gas barrier performance has been greatly improved, in which the water vapor transmission rate and the oxygen transmission rate decreased by 99.18% and three orders of magnitude, respectively. The flame retardant performance has also been improved, and its limiting oxygen index can reach 67.9%. The polyimide matrix can be converted to water‐insoluble by thermal imidization of water‐soluble poly (amic acid) salt precursors, which endows the composites with low hygroscopicity. The coating containing MMT can protect against polyurethane (PU) foam from fire. During the conical calorimetric test, the coated sample self‐extinguished, and the peak heat release rate, total heat release, and total smoke production are significantly decreased by 53.39%, 40.69%, and 53.03%, respectively. Taking advantage of these properties, this work utilizes a facile method to prepare biomimetic composites with low moisture absorption, excellent gas barrier properties, and flame retardancy, which have great application potential.

Synthesis and characterization of biobased poly(butylene adipate‐co‐furandicarboxylate) with excellent gas barrier properties

AbstractIn this work, we prepared a series of bio‐based poly(butylene adipate‐co‐furandicarboxylate) (PBAF) copolyesters with BF segments ranging from 20 to 80 mol% through a two‐step polycondensation. Then, their thermal, mechanical, gas barrier, and degradable properties were investigated. With the increase of BF content, the glass transition temperatures (Tg) and melting temperatures (Tm) of PBAFs increase constantly. Besides, PBAF copolyesters exhibit excellent mechanical performance with elongation at break in the range of 140% to 870%. The elastic modulus and tensile strength of PBAF60 are 138 and 17 MPa respectively, which are comparable to those of commercial poly(butylene adipate‐co‐terephthalate) (PBAT). Moreover, thanks to the structural characteristics of the furan ring, the barrier performances against CO2, O2, and H2O of PBAFs are 4.6–147.5 folds, 4.0–76.0 folds, and 0.8–8.7 folds of PBAT, respectively. Finally, the degradation tests reveal that the weight losses of PBAFs increase with decreasing BF contents. It is worth emphasizing that although the compost degradation rate of PBAF60 is slightly lower than that of PBAT, it is still a prospective alternative to PBAT due to its improved barrier properties. And it provides a possibility for applications in food packaging, mulch films, and structural elements.

Ductile Effect of PGA/PCL Blending Plastics Using a Novel Ionic Chain Extender with Non-Covalent Bonds.

Polyglycolic acid (PGA) is a promising polymer in the packaging field owing to its excellent hydrolysis, heat resistance, and gas barrier properties, but it is limited in application due to its poor toughness. For this reason, a covalently bonded chain extender is introduced to increase compatibility with flexible polymers. However, covalent bonds are unfavorable for application to degradable plastics because of the energy required for reverse reactions. Therefore, we intended to effectively control the ductility of blending plastics by using a novel ionic chain extender with a relatively weaker non-covalent bond than the existing covalent bond. Polycaprolactone (PCL), which has biodegradability and flexibility, was selected as a blending polymer. For comparison, a covalently reactive chain extender (G-CE) and a non-covalently ionic chain extender (D-CE) were synthesized and compounded with blending plastics. Each chain extender improved the compatibility between PGA and PCL, and the ductility of the PGA/PCL blending plastics was more greatly enhanced with non-covalently bonded D-CE than with covalently bonded G-CE. At this time, the ductility of the PGA/PCL(90/10) blending plastic without CE was 7.2%, the ductility of blending plastic with D-CE (10D) was 26.6%, and the ductility of blending plastic with G-CE (10G) was 18.6%. Therefore, it was confirmed that the novel ionic chain extender inducing non-covalent bonds improves the compatibility between PGA and PCL and is more advantageous in enhancing ductility through a reversible reaction.

Polyethylene Terephthalate Composite Films with Enhanced Flame Retardancy and Gas Barrier Properties via Self-Assembly Nanocoating.

The flammability and gas barrier properties are essential for package material. Herein, a highly-oriented self-assembly nanocoating composed of polyvinyl alcohol (PVA) and montmorillonite (MMT) was prepared for endowing polyethylene terephthalate (PET) films with excellent flame retardancy and gas barrier properties. The specific regular nanosheet structure of the PVA/MMT composite nanocoating was confirmed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) and the vertical burning test (VBT) suggested that the thermal stability and flame-retardancy of the coated PET films were considerably improved with more pick-up of the resulting nanocoating. When reaching 650 °C, there was still 22.6% char residual left for coated PET film, while only 6% char residual left for pristine PET film. During the vertical burning test, the flame did not spread through the whole PET film with the protection of PVA/MMT nanocoating, and no afterflame was observed. Scanning electron microscopy (SEM) is consistent with vertical burning test, proving that the thermal stability and flame retardancy of coated PET films were considerably enhanced with the increment of PVA/MMT. Thanks to the multi-layer structure, PVA/MMT nanocoating could effectively improve the gas barrier properties of PET films, and the oxygen vapor transmittance rate and water vapor transmittance rate of PET films were more than four hundred times lower and 30% lower than those of neat PET film. Our work demonstrates that bi-functional flame retardant and gas barrier materials could be gained via constructing inorganic/organic highly-oriented self-assembly nanocoating, which is promising in the area of packaging.

Polystyrene/Polyolefin Elastomer Blends Loaded with Halloysite Nanotubes: Morphological, Mechanical, and Gas Barrier Properties

AbstractHerein, a simple melt‐blending method is utilized to disperse of halloysite nanotubes (HNTs) in polystyrene/polyolefin elastomer (PS/POE) blends. Based on morphological studies, the PS/POE/HNT nanocomposite containing up to 3 phr HNTs shows excellent nanofiller dispersion, while those filled with 5 phr HNTs exhibit nanofiller aggregation. To overcome the nanofiller aggregation issue, the polypropylene‐grafted‐maleic anhydride (PP‐g‐MA) compatibilizer is added to the PS/POE/HNT nanocomposite, which results in improved mechanical properties for the nanocomposite sheets. Furthermore, the addition of compatibilized HNTs to the PS/POE blends leads to decreased O2and N2gas permeabilities. Besides, incorporating POE, HNTs, and PP‐g‐MA leads to a decrease in water vapor transmission of PS. In the end, the experimentally‐determined mechanical properties and gas permeabilities of the nanocomposite sheets are compared to those predicted by prevalent theoretical models, revealing a good agreement between the experimental and theoretical results. Molecular‐dynamics simulations are also carried out to calculate the gas diffusion coefficients in the different sheets to further support the experimental findings in this study. Overall, the PS/POE/HNT/PP‐g‐MA nanocomposite sheets fabricated in this work demonstrate excellent mechanical and gas barrier properties; and hence, can be used as candidate packaging materials. However, the strength of the resulting PS/POE blend may be inferior to that of the virgin PS.