scCO2 Processing Research Articles

Innovative recycling of organic binders from electric vehicle lithium-ion batteries by supercritical carbon dioxide extraction

The growing demand for energy storage devices due to the skyrocketing production/consumption of portable electrical and electronic equipment as well as electric vehicles has promoted battery technologies, resulting in the piling of a large number of waste lithium-ion batteries (LIBs). Organic binders wrapped on electrode particles are usually the main reason that causes the difficulty of liberation and extraction of electrode materials. Pyrolysis or incineration is the general approach to separate the organic binder, leading to fluorinated exhaust gas emissions. In this study, the supercritical carbon dioxide (SC CO2) combined with a cosolvent dimethyl sulfoxide was innovatively adapted to enable the extraction of organic binders from spent LIBs to facilitate the liberation of the cathode material from aluminum foil. Pure polyvinylidene fluoride was preferentially used to study the SC CO2 dissolution mechanism. The results indicate that 98.5 wt% polyvinylidene fluoride (PVDF) dissolves in SC CO2 dimethyl sulfoxide system under the optimum conditions; 70°C process temperature, 80 bar pressure, and 13 min duration. After removing PVDF, the recovered sample was characterized by Fourier Transform Infrared Spectrometer (FTIR) and thermogravimetric analyzer (TGA) to observe its possible re-utilization. It is clear that the surficial chemical groups and content remained the same after treatment. SC CO2 processing effectively liberates the active cathode material from the aluminum substrate due to removal of the binder. The suggested innovative approach is promising as an alternative pretreatment method due to its high efficiency, relatively low energy consumption, and environmentally friendly features.

Controlling the foam morphology of supercritical CO2‐processed poly(methyl methacrylate) with CO2‐philic hybrid nanoparticles

AbstractHighly CO2‐philic nanoparticles, octatrimethylsiloxy polyhedral oligomeric silsesquioxanes (POSS) are used to increase the affinity of poly(methyl methacrylate) (PMMA) to CO2 in supercritical carbon dioxide (scCO2) foaming, thus to improve its foaming performance and the foam morphology. PMMA and PMMA‐POSS composite foams were produced based on the two‐factorial design, at the upper and lower experimental conditions of pressure, temperature, processing time, and venting rate. The foams of PMMA‐5% POSS composites exhibited smaller average pore sizes and higher pore densities than neat PMMA and PMMA‐0.5% POSS composites. The smallest average pore diameter (0.3 μm) and the highest pore density (6.33 × 1012 cm−3) were obtained with this composite processed at 35°C, 32 MPa, for 24 h and depressurized with fast‐venting rate (0.4 MPa/s). ScCO2 processing decreased the density of the polymer by more than 50%.

Wide-Ranging Multitool Study of Structure and Porosity of PLGA Scaffolds for Tissue Engineering.

In this study, the nanoscale transformation of the polylactic-co-glycolic acid (PLGA) internal structure, before and after its supercritical carbon dioxide (sc-CO2) swelling and plasticization, followed by foaming after a CO2 pressure drop, was studied by small-angle X-ray scattering (SAXS) for the first time. A comparative analysis of the internal structure data and porosity measurements for PLGA scaffolds, produced by sc-CO2 processing, on a scale ranging from 0.02 to 1000 μm, was performed by SAXS, helium pycnometry (HP), mercury intrusion porosimetry (MIP) and both “lab-source” and synchrotron X-ray microtomography (micro-CT). This approach opens up possibilities for the wide-scale evaluation, computer modeling, and prediction of the physical and mechanical properties of PLGA scaffolds, as well as their biodegradation behavior in the body. Hence, this study targets optimizing the process parameters of PLGA scaffold fabrication for specific biomedical applications.

Development of a decellularized porcine bone graft by supercritical carbon dioxide extraction technology for bone regeneration.

A series of novel decellularized porcine collagen bone graft (DPB) materials in a variety of shapes and sizes were developed by the supercritical carbon dioxide (SCCO2 ) extraction technique. The complete decellularization of DPB was confirmed by hematoxylin and eosin staining, 4,6-diamidino-2-phenylindole (DAPI) staining, and residual DNA analysis. The native intact collagen remained in the DPB after the SCCO2 process was confirmed by Masson trichrome staining. The physicochemical characteristics of DPB were investigated by scanning electron microscopy and x-ray diffraction. The cytotoxicity and biocompatibility tests according to ISO10993 and its efficacy for bone regeneration in osteochondral defects in rabbits were evaluated. The rabbit pyrogen test confirmed DPB was non-toxic. In vitro and in vivo biocompatibility tests of the DPB did not show any toxic or mutagenic effects. The bone regeneration potential of the DPB presented no significant histological differences compared to commercially available deproteinized bovine bone. In conclusion, DPB produced by SCCO2 exhibited similar chemical characteristics to human bone, no toxicity, good biocompatibility, and enhanced bone regeneration in rabbits comparable to that of deproteinized bovine bone. Results from this study could shed light on the potential application of the SCCO2 extraction technique to generate a native decellularized scaffold for bone tissue regeneration in human clinical trials.

\u03b2-Carotene extraction from Dunaliella salina by supercritical CO2

This paper reports the results of supercritical carbon dioxide (scCO2) extraction of β-carotene from Dunaliella salina as potential alternative to conventional organic solvent extraction. In pilot-scale scCO2 experiments, the pressure, temperature, and co-solvent concentration were varied. The supercritical extraction at 500 bar, 70 °C, and 10 wt% ethanol as co-solvent yielded in the highly efficient pigment recovery of over 90%. Techno-economic assessment demonstrated higher energy consumption for the scCO2 extraction that was compensated by lower solvent costs. Thus, comparable pigment production costs to the reference extraction with n-hexane were estimated for the scCO2 process. Due to the green solvent properties of scCO2 and ethanol, this approach is highly promising for extraction of algal biomass in industrial scale.

Supercritical carbon dioxide assisted complexation of benznidazole: γ-cyclodextrin for improved dissolution

Benznidazole (BZ) and nifurtimox are first-line drugs for the treatment of Chagas disease, with BZ preferred due to its moderate side effects compared to nifurtimox. However, BZ has low aqueous solubility and a low dissolution rate which potentially limit its oral bioavailability. We now report for the first time efforts to improve the aqueous dissolution of BZ via processing and γ-cyclodextrin (γ-CD) complexation using supercritical carbon dioxide (scCO2). We first investigated the solubility of BZ in scCO2 and the effect of scCO2 processing on the solid-state, particle size characteristics and dissolution behaviour of processed BZ compared to un-processed BZ. Moreover, the efficacy of scCO2 in dissolving and complexing BZ with γ-CD was studied and compared with conventional freeze-drying (FD). The solubility of BZ in scCO2 was time-dependent (1.78 × 10-6 to 3.18 × 10-5 mol. mol−1) and reached the equilibrium after 10 h. Complexation efficiency and loading capacity were in the range of 4 ± 1.4% to 54 ± 10% and 1.8 ± 0.1% to 27 ± 5%, respectively, and they varied depend on the preparation method and conditions. XRD, DSC, and FTIR results revealed that although scCO2 was able to solubilise BZ, it did not change the solid-state morphology of BZ. Contrary, FD and γ-CD complexation were shown to affect the solid-state characteristics of BZ and γ-CD. The mean particle size of processed BZ was significantly reduced from 604 ± 61.50 nm (un-processed BZ) to 257 ± 41–385 ± 36.56 nm (processed BZ). Both the dissolution rate profiles and dissolution efficiency differed depending on preparation methods, process conditions, and BZ-to-γ-CD ratio, but they were significantly increased compared to un-processed BZ. Overall, this study demonstrated that the preparation methodology had substantial effects on the solid-state particle size/morphology characteristics and aqueous dissolution behaviour of BZ, both alone or in complexes with γ-CD, with potential to develop improved formulations.

Enhancing resistant starch content in brown rice using supercritical carbon dioxide processing

AbstractDietary fiber and resistant starch (RS) play a key role in suppressing the increase in blood glucose levels. Whole grains such as brown rice (BR) which have a higher content of dietary fiber and important nutrients, are common products used for the maintenance of human health. The higher RS content in BR is suggested to contribute significantly to blood glucose level maintenance in cooperation with dietary fiber. We aimed to enhance the RS levels in BR using supercritical carbon dioxide (scCO2) processing which is typically undertaken by the reactor packed with BR and filled carbon dioxide in a state of supercritical fluids developed with above critical temperature and pressure, and a suitable operating duration as an alternative to conventional methods. This innovative process expectedly enhanced the RS content, promoted gelatinization, and eliminated the foul odors causing appetizing control. In addition, this processing method is highly effective for the removal of pollutions such as pesticides and inactivation of microbial contaminants in food. Therefore, scCO2 processing is a promising alternative to conventional methods.Practical ApplicationProcessing RS in cereals using scCO2 is an innovative alternative to conventional processes such as heat‐moisture treatment and annealing, autoclaving and retrogradation cycles, high hydrostatic pressure, and extrusion that are commonly used to promote RS formation in food products to improve human health and consequently contributes to the control of blood glucose levels after a meal. The innovative scCO2 process is considerably simple, easily operable, and environmentally friendly and safe due to the use of nontoxic CO2 as a solvent. This process has great potential for application in the extraction of pesticides and fats and the inactivation of microbes in food products. Therefore, scCO2 processing will be useful as a food processing method that helps maintain human health.

PLA/PLGA-Based Drug Delivery Systems Produced with Supercritical CO2-A Green Future for Particle Formulation?

Supercritical carbon dioxide (SC-CO2) can serve as solvent, anti-solvent and solute, among others, in the field of drug delivery applications, e.g., for the formulation of polymeric nanocarriers in combination with different drug molecules. With its tunable properties above critical pressure and temperature, SC-CO2 offers control of the particle size, the particle morphology, and their drug loading. Moreover, the SC-CO2-based techniques overcome the limitations of conventional formulation techniques e.g., post purification steps. One of the widely used polymers for drug delivery systems with excellent mechanical (Tg, crystallinity) and chemical properties (controlled drug release, biodegradability) is poly (lactic acid) (PLA), which is used either as a homopolymer or as a copolymer, such as poly(lactic-co-glycolic) acid (PLGA). Over the last 30 years, extensive research has been conducted to exploit SC-CO2-based processes for the formulation of PLA carriers. This review provides an overview of these research studies, including a brief description of the SC-CO2 processes that are widely exploited for the production of PLA and PLGA-based drug-loaded particles. Finally, recent work shows progress in the development of SC-CO2 techniques for particulate drug delivery systems is discussed in detail. Additionally, future perspectives and limitations of SC-CO2-based techniques in industrial applications are examined.

Functionalization of Silica SBA-15 with [3-(2-Aminoethylamino)Propyl] Trimethoxysilane in Supercritical CO2 Modified with Methanol or Ethanol for Carbon Capture

The CO2 adsorption process using amine-grafted silica is a promising technology for reducing the CO2 emissions from the power and industry sectors. In this work, silica SBA-15 was functionalized using [3-(2-aminoethylamino)propyl] trimethoxysilane (AEAPTS) in supercritical CO2 (scCO2) modified with 10% mol methanol or ethanol. The functionalization experiments were carried out at 323 K and 12.5 MPa, and with reaction times of 2 and 3 h. The molar fraction of AEAPTS in scCO2 plus 10% mol alcohol ranged from 0.5 × 10−3 to 1.8 × 10−3. It was found that as the molar fraction of AEAPTS increased, the amino-grafting density steadily rose, and the pore volume, surface area and pore size of the functionalized silica SBA-15 also decreased gradually. The scCO2 functionalization method was compared to the traditional toluene method. The diamine-SBA-15 prepared in the scCO2 process shows a slightly lower amine-grafting density but a higher surface area and pore volume than the ones obtained using the traditional method. Finally, the excess CO2 adsorption capacity of the materials at different temperatures and low pressure was measured. The diamine-silica SBA-15 displayed moderate excess CO2 adsorption capacities, 0.7–0.9 mmol∙g−1, but higher amine efficiency, ca. 0.4, at 298 K, due to the chemisorption of CO2. These findings show that diamine-grafted silica for post-combustion capture or direct air capture can be obtained using a media more sustainable than organic solvents.

Surface morphology and drug loading characterization of 3D-printed methacrylate-based polymer facilitated by supercritical carbon dioxide

Polymers have been shown to have viable applications in the biomedical field, from controlled drug delivery systems to biological implants. The preparation and processing of polymers into bio-systems have nevertheless encountered some technical challenges in part customization and adverse effects to the human body functions and recovery. This study proposes the utilization of 3D printing technology and supercritical carbon dioxide (scCO2) processing to deliver a drug-impregnated polymeric material system which can be engineered and tuned to suit a particular implantation procedure and dramatically improve patient outcomes. In this work, an acrylate-based polymer is 3D-printed using stereolithography, then impregnated with flurbiprofen drug using scCO2. Drug loading above 24 % by mass is achievable under the tested conditions. The correlation of drug loading and material surface roughness with different process parameters, including 3D printing layer thickness, scCO2 processing temperature, pressure and treatment time, are investigated and empirically modeled using the linear regression methods.

Supercritical carbon dioxide enhanced pre-treatment of cotton stalks for methane production

Cotton stalks (CSs) are an abundant, renewable lignocellulose residue, which is usually burnt in the field to prevent propagation of vegetal diseases, causing economic losses and environmental concerns. The production of biogas has been considered as an alternative. This work aimed to improve the biogas production from CS by steam or organosolv plus supercritical carbon dioxide (scCO2) pre-treatment. All samples were pre-treated in a 500 mL autoclave for 140 min at 180 °C and fermented in 1 L eudiometer batch digesters for 42 days at 37.5 °C. The biogas and methane yields achieved from the untreated CS were 250 and 137 norm litres per kg of volatile solid (LN kg−1 VS), respectively. Pre-treatment of the CS samples with steam or the organosolv plus scCO2 process increased the methane yield by 20% compared to the untreated samples. The highest methane yield of 177 LN kg−1 VS was achieved by organosolv plus scCO2 pre-treatment at 100 bar and 180 °C for 140 min. Moreover, pre-treatment of the CS led to a significant reduction in the optimal digestion time from 30 days to 20 days for biogas production for the untreated CS.

Microwave Irradiation Assisted Supercritical Carbon Dioxide Extraction of Bio-Oils from Chlorella Vulgaris Microalgae

Chlorella vulgaris is one of the promising microalgae strains that can produce high yield of bio-oils. The C. vulgaris was pretreated with microwave irradiation prior to extraction using supercritical carbon dioxide (SCCO2). Fourier transform infrared spectroscopy (FTIR) analysis showed microwave irradiation pretreatment does not affect the material composition of C. vulgaris. Scanning electron microscopy (SEM) of the microwave irradiation pretreated microalgae showed an agglomeration of the cells with the cells shape became distorted due to rupturing of the cell walls. Optimization of the SCCO2 process parameters (pressure, temperature and CO2 flow rate) was performed by using response surface methodology (RSM) with central composite design (CCD). Two factors significantly affecting the extraction yield were temperature and pressure. The model equation also predicted the optimum condition for the SCCO2 (without microwave pretreatment) at 70 , 5676 psi and 7 sL/ min while optimum condition for SCCO2 (microwave irradiation pretreatment) at 63 , 5948 psi and 10 sL/ min. High amount of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), -linolenic acid and palmitoleic acid were found in the extracted oil with microwave irradiation pre-treatment sample. In addition, the polyunsaturated fatty acids (PUFA) content in the microwave irradiation pretreated oil was considerably low and is desirable for biodiesel production.

Facile synthesis of 1-butylamino- and 1,4-bis(butylamino)-2-alkyl-9,10-anthraquinone dyes for improved supercritical carbon dioxide dyeing

Supercritical carbon dioxide (scCO2) has recently been conquering both material sciences and process engineering owing to its intriguing properties like high diffusivity and tuneable (de)solubilizing performance. However, except for impregnation with biocidal preservatives, utilization of scCO2 for modification of wood including dyeing has been hitherto less explored. Therefore, we recently proposed a green wood dyeing approach that relies on the excellent carrier medium properties of CO2 for non-polar disperse dyes in supercritical conditions and their reversion when leaving the supercritical state. However, using a common disperse dye of the 9,10-anthraquinone family (Disperse Blue, DB-134) without the addition of co-solvent, only a moderate colour change was obtained for the interior of small wood cuboids (1 cm × 1 cm x 2 cm) even after extensive variation of scCO2 process conditions. Insufficient solubility of the dye in scCO2 was assumed to be a major hindrance for homogeneous wood dyeing. Therefore, we synthesized a variety of 1-n-butylamino- and 1,4-bis(n-butylamino)-9,10-anthraquinone derivatives carrying different alkyl moieties in 2-position, which was confirmed to improve scCO2 solubility. Instead of a previously reported seven-step synthesis affording moderate yields only (60% on average), we propose an alternate much simpler synthesis comprising of Marschalk alkylation (2-position) and a sequence of tosylation and n-alkylamination (1-position). The latter proved to pave way to a wide variety of colours and disperse dyes of improved solubility in scCO2. Moreover, all products were characterized by various techniques including liquid-state 1H and 13C NMR and X-ray crystallography. Complementing X-ray diffraction, quantum-mechanical simulations were performed to predict or confirm conformation and colour of selected compounds.

Myristic Acid Coated Protein Immobilised Mesoporous Silica Particles as pH Induced Oral Delivery System for the Delivery of Biomolecules.

Solid core drug delivery systems (SCDDS) were prepared for the oral delivery of biomolecules using mesoporous silica as core, bovine haemoglobin (bHb) as model drug and supercritical fluid (SCF) processing as encapsulation technique. The use of organic solvents or harsh processing conditions in the development of drug delivery systems for biomolecules can be detrimental for the structural integrity of the molecule. Hence, the coating on protein-immobilised particles was performed via supercritical carbon dioxide (scCO2) processing at a temperature lower than the melting point of myristic acid (MA) to avoid any thermal degradation of bHb. The SCDDS were prepared by bHb immobilisation on mesoporous silica followed by myristic acid (MA) coating at 43 °C and 100 bar in scCO2. bHb-immobilised silica particles were also coated via solvent evaporation (SE) to compare the protein release with scCO2 processed formulations. In both cases, MA coating provided required enteric protection and restricted the bHb release for the first two hours in simulated gastric fluid (SGF). The protein release was immediate upon the change of media to simulated intestinal fluid (SIF), reaching 70% within three hours. The release from SCF processed samples was slower than SE formulations, indicating superior surface coverage of MA on particles in comparison to the SE method. Most importantly, the protein conformation remained unchanged after the release from SCDDS as confirmed by circular dichroism. This study clearly demonstrates that the approach involving protein immobilisation on silica and scCO2 assisted melt-coating method can protect biomolecules from gastric environment and provide the required release of a biologic in intestine without any untoward effects on protein conformation during processing or after release.

Parametric Characterization of Copper Metal Coatings Produced by Supercritical Argon Electroplating

An electroplating process under supercritical argon applied to a copper sulfate bath with no additives is presented in this work. Adjusting electroplating parameters such as temperature, pressure and current density changed the deposition behavior, thus changing the coating properties. The finest grains (~ 20.91 nm) were obtained at 2500 psi and 35°C, which were relatively higher pressure and lower temperature than those found for SC-CO2 processes, respectively, 2000 psi and 50°C. Mechanical, electrical and corrosion analyses revealed the coating properties were enhanced compared with those produced by the conventional process. Finally, the results point to optimal fabrication parameters of 35°C, 5 A/dm2 and 2500 psi, achieving the relatively best coating properties and highest current efficiency (~ 93%).

Supercritical carbon dioxide extraction of pomegranate (Punica granatum L.) seed oil: Kinetic modelling and solubility evaluation

Experimental and modelling investigations of supercritical fluid CO2 extraction (SC-CO2) of pomegranate seed oil (PSO) were performed at 240, 280 and 320 bar, and 40, 50 and 60 °C with CO2 flow rate of 8 kg/h. A retrograde solubility behaviour was found at 50 °C and 280 bar. The model of broken and intact cells developed by Sovová adequately described SC-CO2 processes (AARD% 0.2497-1.1691). It was demonstrated that the extraction of type A was the most suited to apply. The solubility of PSO in SC-CO2 was estimated and modelled by Chrastil model (AARD% 0.1910-1.1821). The highest value of the oil solubility was obtained at 320 bar and 60 °C. PSO extracted by SC-CO2 was found high-quality, evaluated in terms of antioxidant activity, and richer of punicic acid as compared to Soxhlet extracted oil.

Study on Surface Properties of Aramid Fiber Modified in Supercritical Carbon Dioxide by Glycidyl-POSS.

The outstanding diffusivity and permeability of supercritical carbon dioxide (scCO2) are extremely beneficial for grafting reaction. In this work, aramid fibers (AF) are modified in scCO2 by glycidyl-polyhedral oliomeric silsesquioxane (POSS) with 2-ethyl-4-methylimidazole (2E4MZ) on the basis of cleaning with acetone. The surface morphology and chemical structure of the modified AF were measured and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Thermogravimetric (TG), and Atomic force microscope (AFM). The interfacial shear strength (IFSS) was measured by a micro-bond pull-out test, then the modified AF/EP composites were prepared and the interlaminar shear strength (ILSS) was characterized. Research has shown that some of the glycidyl-POSS molecular chains permeated into the surface of the fiber and grafted onto the surface of the AF after modification, and the other glycidyl-POSS self-assembled on the surface of the fiber. XPS indicated the introduction of C–O and –COO–, which confirmed the existence of chemical reactions between AF and glycidyl-POSS. AFM and SEM images revealed that 2E4MZ, not only promoted the grafting reaction of glycidyl-POSS, but also intensified the self-assembly of glycidyl-POSS, both of which increased the roughness of the fiber. A monofilament tensile test and micro-bond pull-out test showed that there was a negative effect on the tensile strength after scCO2 processing. The tensile strength of modified AF, with glycidyl-POSS, increased the highest strength of 25.7 cN dtex−1, which was 8% higher than that of pristine AF. The improvement of ILS roughness and the polar chemical groups produced in grafting reaction. These results indicated that AF, treated in scCO2, with glycidyl-POSS, which is a suitable way of fiber modification, can significantly improve the surface adhesion of AF reinforced composites.

Recent Progress of Supercritical Carbon Dioxide in Producing Natural Nanomaterials.

Natural medicines are widely utilized in human healthcare. Their beneficial effects have been attributed to the existence of natural active ingredients (NAI) with a positive impact on disease treatment and prevention. Public awareness about the side effects of synthetic chemical compounds increased the need for NAI as well. Clinical applications of NAI are limited by their instability and poor water solubility, while micronization is a major strategy to overcome these drawbacks. Supercritical carbon dioxide (sc-CO2) based nano techniques have drawn great attention in nanomedicinal area for many years, due to their unique characters such as fast mass transfer, near zero surface tension, effective solvents elimination, non-toxic, non-flammable, low cost and environmentally benign. In terms of functions of sc-CO2, many modified sc-CO2 based techniques are developed to produce NAI nanoparticles with high solubility, biological availability and stability. 5 types of promising methods, including gas-assisted melting atomization, CO2-assisted nebulization with a bubble dryer, supercritical fluidassisted atomization with a hydrodynamic cavitation mixer, supercritical CO2-based coating method and solution-enhanced dispersion by sc-CO2 process, are summarized in this article followed by a highlight of their fundamental synthesis principles and important medicinal applications.

Soluplus®, Eudragit®, HPMC-AS foams and solid dispersions for enhancement of Carvedilol dissolution rate prepared by a supercritical CO2 process

The present work is aimed towards designing advanced materials by means of sustainable processes. In that sense, the utilization of supercritical CO2 (scCO2) for processing of pharmaceutical polymers (Soluplus®, Eudragit®, and hydroxypropyl methylcellulose acetate succinate), alone and with an addition of cardiovascular drug Carvedilol, was explored. Employed single-step static scCO2 process (pressure of 30 MPa and temperature of 100 °C for 2 h) enabled fabrication of solvent-free polymeric foams and Carvedilol solid dispersions with controlled microstructure and average pore diameter of 101–257 μm suitable for application in the pharmaceutical industry. ScCO2 did not remain in the foams after processing or affected the polymer composition, while Carvedilol formed hydrogen bonds with the polymers. Carvedilol was molecularly dispersed in the fabricated solid dispersions and its transition from the crystalline to amorphous form was complete. Korsmeyer-Peppas model was successfully used for the mathematical description of Carvedilol dissolution from solid dispersions. The dissolution rate of Carvedilol in acidic medium was significantly enhanced by its dispersion in tested polymers using the proposed high-pressure method.

Effect of silane functionalized graphene prepared by a supercritical carbon dioxide process on the barrier properties of polyethylene terephthalate composite films

In this work, a simple and eco-friendly strategy to modify graphene nanoplatelets (GNs) with different silane coupling agents using a supercritical carbon dioxide (Sc-CO2) process has been presented, and effect of the modified GNs on the oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of GN/PET composite films was studied. FT-IR, SEM, EDX and TG results indicated that Sc-CO2 process was an effective strategy to modify GNs with silane coupling agents. Addition of the modified GNs into PET matrix could greatly decrease the OTR and WVTR values of the GNs/PET composite films, and the WVTR of GNs560/PET composite film and OTR of GNs550/PET composite film were respectively decreased about 90.08% and 58.04%, as compared to those of GNs/PET composite film. It is found that the gas barrier property of GN/PET composites was attributed to not only the tortuous path effect caused by GNs themselves and the interfacial interaction, but also the affinity of binding bonds between GNs and the polymer to the gas molecules. It is believed that this work provided a strategy to design and prepare CN/polymer composites with high barrier properties.