Low-pressure CO2 sorption in poly(vinyl benzoate) conditioned to high-pressure CO2

Sorption of CO₂ in poly(vinyl benzoate) was gravimetrically measured at pressures up to 1 atm. Sorption isotherms were determined above and below the glass transition temperature T_g from 5 to 85°C. The isotherms were analyzed by the dual-mode sorption model assuming that the plasticizing effect of sorbed CO₂ is negligible at this pressure range. The solubilities and Henry's law dissolution parameters were compared with those obtained by the high-pressure sorption and permeation measurements. Henry's law dissolution parameters were in good agreement with one another. However, the solubilities first determined here were smaller than those determined by the high-pressure sorption experiment at the same temperature. It was clear that the Langmuir capacity of the present specimen was smaller in spite of similar high-pressure CO₂ exposure. Relaxation of the polymer was expected to be one of the reasons. This expectation was confirmed from the observation and analysis of sorption isotherms after two kinds of treatments. After annealing above T_g, the Langmuir capacity was shown to be decreased to 1/2 or even to 1/3 from the sorption isotherms below 45°C. This means that the conditioning to the high-pressure CO₂ surely has a large effect on the nature of glassy polymer. Just after high-pressure CO₂ exposure at 25°C, increased solubility was observed. Furthermore, the slow decrease of solubility, that is, the decrease of conditioning effect, was also followed from the continual measurements at 25°C. This result reflects not only the characteristic of sorption capacity after high-pressure CO₂ exposure, but also the relaxation of polymer in glassy state.     

Density measurement of polymer/CO2 single‐phase solution at high temperature and pressure using a gravimetric method

The densities of two polymer/CO₂ single‐phase solutions, poly(ethylene glycol) (PEG)/CO₂ and polyethylene (PE)/CO₂, were measured at temperatures higher than melting temperature of the polymer under CO₂ pressures in the range 0–15 MPa using a newly‐proposed gravimetric method. A magnetic suspension balance (MSB) was used for the density measurement under the high pressure CO₂: A thin disc‐shaped platinum plate was submerged in the considered polymer/CO₂ single‐phase solution in the MSB high‐pressure cell. The weight of the plate was measured while keeping CO₂ pressure and temperature in the sorption cell at a specified level. Since the buoyancy force exerted on the plate by the polymer/CO₂ solution reduced the apparent weight of the plate, the density of the polymer/CO₂ solution could be calculated by subtracting the true weight of the plate from its measured weight. Experimental results showed that the density of PE/CO₂ solution increased with the increase of CO₂ pressure and the density of PEG/CO₂ solution decreased with the increase of CO₂ pressure. To differentiate the effect of CO₂ dissolution in polymer from that of mechanical pressure, the density of polymer/CO₂ solution was compared with the density of neat polymer under the given mechanical pressure, which was calculated using the Sanchez–Lacombe equation of state and Pressure–Volume–Temperature data of the polymer. The comparison could elucidate that the dissolution of CO₂ in polymer reduced density of both PEG/CO₂ and PE/CO₂ systems but the degree of CO₂ induced‐density reduction was different between two polymer/CO₂ systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Molecular dynamics study on the dissolution behaviors of poly(vinyl acetate)-polyether block copolymers in supercritical CO2

Poly(vinyl acetate) (PVAc) could be dissolved in CO₂ at a high pressure, which limits its application. In this work, the PVAc-polyether block copolymers were constructed by introducing the CO₂-philic blocks poly(propylene oxide) (PPO) and poly(ethylene oxide) (PEO) into the PVAc molecules to increase the solubility of these polymers in supercritical CO₂ (scCO₂). The dissolution behaviors of PVAc-polyether copolymers with different structures in scCO₂ were investigated by the molecular dynamic simulation methods. First, the cohesive energy and solubility parameters of PVAc, PVAc-PEO, and PVAc-PPO copolymers were analyzed. Moreover, the mechanism of PVAc-polyether copolymers dissolving in CO₂ was investigated. The results show that PVAc-PPO molecules have a higher solubility in CO₂ because they have lower polymer–polymer and higher polymer-CO₂ interactions than PVAc and PVAc-PEO. Among the three structures of PVAc-PPO molecules, PVAc-PPO-PVAc (VPV) has a highest solubility in CO₂. Therefore, the molecular composition and structure have greatly influences on the interactions of polymer and CO₂.     

超临界CO2辅助聚合物加工

近年来,以超临界CO₂替代聚合物加工过程中大量使用的有机溶剂实现超临界CO₂辅助聚合物加工过程已引起人们越来越多的关注。CO₂在聚合物中的溶解扩散可导致其结构和形态的变化,能够溶胀增塑聚合物并且将溶解于其中的小分子物质携带输运到聚合物基体中,进而影响聚合物的结晶及晶型转变行为,聚合物/CO₂体系界面张力以及聚合物/CO₂体系流变行为等基本物性的变化。利用聚合物基本物性的变化可实现CO₂辅助聚合物接枝反应,CO₂辅助聚合物渗透小分子物质以及CO₂辅助聚合物发泡等超临界CO₂辅助聚合物加工过程的应用。结合本研究室的实例,探讨了CO₂作用下等规聚丙烯和间规聚丙烯的结晶行为以及一种多晶型聚合物--等规聚丁烯-1的晶型转变行为;探讨了利用CO₂对等规聚丙烯、聚乳酸和聚酯三种典型的低熔体强度结晶聚合物具有的不同诱导结晶作用,调控聚合物的结晶行为,使其具备发泡所需的熔体强度,制备了具有不同结构特征的发泡聚合物材料。     

Measurement and prediction of LDPE/CO2 solution viscosity

When CO₂ is dissolved into a polymer, the viscosity of the polymer is drastically reduced. In this paper, the melt viscosities of low‐density polyethylene (LDPE)/supercritical CO₂ solutions were measured with a capillary rheometer equipped at a foaming extruder, where CO₂ was injected into a middle of its barrel and dissolved into the molten LDPE. The viscosity measurements were performed by varying the content of CO₂ in the range of 0 to 5.0 wt% and temperature in the range of 150°C to 175°C, while monitoring the dissolved CO₂ concentration on‐line by Near Infrared spectroscopy. Pressures in the capillary tube were maintained higher than an equilibrium saturation pressure so as to prevent foaming in the tube and to realize single‐phase polymer/CO₂ solutions. By measuring the pressure drop and flow rate of polymer running through the tube, the melt viscosities were calculated. The experimental results indicated that the viscosity of LDPE/CO₂ solution was reduced to 30% of the neat polymer by dissolving CO₂ up to 5.0 wt% at temperature 150°C. A mathematical model was proposed to predict viscosity reduction owing to CO₂ dissolution. The model was developed by combining the Cross‐Carreau model with Doolittle's equation in terms of the free volume concept. With the Sanchez‐Lacombe equation of state and the solubility data measured by a magnetic suspension balance, the free volume fractions of LDPE/CO₂ solutions were calculated to accommodate the effects of temperature, pressure and CO₂ content. The developed model can successfully predict the viscosity of LDPE/CO₂ solutions from PVT data of the neat polymer and CO₂ solubility data.     

Evaluation of CO2-philicity and thickening capability of multichain poly(ether-carbonate) with assistance of molecular simulations

Phenyl-centered tri-chain poly(ether-carbonate) (TMA-PEC), phenyl-centered double-chain poly(ether-carbonate) (TPA-PEC), and phenyl-centered four-chain poly(ether-carbonate) (TFA-PEC) were synthesized to act as CO₂ thickener. Their solubility in CO₂ was measured by cloud point pressure. In order to explore the material characteristics that affect the solubility, dynamic simulations were used to analyze intermolecular polymer interactions, and the interaction between polymers and CO₂. It was found that TPA-PEC and TMA-PEC has better solubility than TFA-PEC in CO₂ among the three polymers while the thickening effect is poor, TFA-PEC possess the best viscosity thickening effect while the solubility in CO₂ is unfavorable. The silicone unit 1,1,1,3,5,5,5-heptamethyl-3-(3-[oxiran-2-ylmethoxy] propyl)trisiloxane modified TFA-PEC (TFA-PEC-SAGE) combine good solubility and good thickening ability together. The molecular simulations show that TPA-PEC and TMA-PEC have weaker intermolecular interactions and TPA-PEC and TMA-PEC have stronger interaction with CO₂ which are beneficial to the solubility.     

Simulation modeling of the phase behavior of palm oil-supercritical carbon dioxide

The phase behavior of crude palm oil (CPO) with supercritical CO₂ was successfully modeled in an Aspen Plus^® 10.2.1 commercial simulator (Aspen Technology Inc., Cambridge, MA) using the Redlich-Kwong-Aspen (RKA) equation of state thermodynamic model. The modeling procedure involved estimating pure component vapor pressures and critical properties and computing a regression of phase equilibrium behavior. The interaction parameters for the RKA model were obtained from the regression of experimental phase equilibrium data for a binary system of palm oil components-supercritical CO₂ available in the literature. The distribution coefficients and solubilities of palm oil components obtained from this simulation showed good agreement with experimental data obtained from the literature. The model provides an efficient and cost-effective alternative for the preliminary design and optimization of a supercritical fluid extraction process involving a complex CPO-supercritical CO₂ system.     

Investigation of the interaction of CO2 with poly (L‐lactide), poly(DL‐lactide) and poly(ε‐caprolactone) using FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy was used to reveal intermolecular interactions between carbon dioxide (CO₂) and the carbonyl groups of poly(L ‐lactide) (PLLA), poly(D,L ‐lactide) (PDLLA), and poly(ε‐caprolactone) (PCL). After exposing polymer films to high pressure CO₂, the wave number of the absorption maxima of the polymer carbonyl groups shifted to higher values. Also, due to the interaction between CO₂ and the carbonyl groups of the polymers, a new broad peak in the bending mode region of CO₂ appeared. To distinguish between polymer‐associated and nonassociated CO₂, and to quantify these contributions, the bending mode peaks were deconvoluted. From these contributions, it was found that in the case of PCL more CO₂ is interacting with the polymer carbonyl groups than in the case of PDLLA and PLLA. Under our experimental conditions, 40°C and pressures up to 8 MPa, a significant depression of the PCL melting temperature was observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase behavior on the binary and ternary mixtures of poly(cyclohexyl acrylate) and poly(cyclohexyl methacrylate) in supercritical CO2

High‐pressure phase behavior was measured for the CO₂–cyclohexyl acrylate and CO₂–cyclohexyl methacrylate system at 40, 60, 80, 100, and 120°C and pressure up to 206 bar. This system exhibits type I phase behavior with a continuous mixture‐critical curve. The experimental results for the CO₂–cyclohexyl acrylate and CO₂–cyclohexyl methacrylate system were modeled using the Peng–Robinson equation of state. Experimental cloud‐point data, at a temperature of 250°C and pressure of 2800 bar, were presented for ternary mixtures of poly(cyclohexyl acrylate)–CO₂–cyclohexyl acrylate and poly(cyclohexyl methacrylate)–CO₂–cyclohexyl methacrylate systems. Cloud‐point pressures of poly(cyclohexyl acrylate)–CO₂–cyclohexyl acrylate system were measured in the temperature range of 40 to 180°C and at pressures as high as 2200 bar with cyclohexyl acrylate concentrations of 22.5, 27.4, 33.2, and 39.2 wt %. Results showed that adding 45.6 wt % cyclohexyl acrylate to the poly(cyclohexyl acrylate)–CO₂ mixture significantly changes the phase behavior. This system changed the pressure–temperature slope of the phase behavior curves from the upper critical solution temperature (UCST) region to the lower critical solution temperature (LCST) region with increasing cyclohexyl acrylate concentration. Poly(cyclohexyl acrylate) did not dissolve in pure CO₂ at a temperature of 250°C and pressure of 2800 bar. Also, the ternary poly(cyclohexyl methacrylate)–CO₂–cyclohexyl methacrylate system was measured below 187°C and 2230 bar, and with cosolvent of 27.4–46.7 wt %. Poly(cyclohexyl methacrylate) did not dissolve in pure CO₂ at 240°C and 2500 bar. Also, when 53.5 wt % cyclohexyl methacrylate was added to the poly(cyclohexyl methacrylate)–CO₂ solution, the cloud‐point curve showed the typical appearance of the LCST boundary. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1117–1125, 2004     

Influence of tert-amine groups on the solubility of polymers in CO2

There is a need to develop new, non-fluorous polymers that are highly soluble in CO₂. Experimental evidence indicates that tertiary amine and pyridine groups may exhibit favorable Lewis acid-Lewis base type interactions with CO₂. It is therefore reasonable to assume that incorporation of tertiary amines into the side chain or backbone of non-fluorous polymers may impart a degree of CO₂-solubility to the polymer. We present experimental results for eight different tert-amine-containing polymers. Of these polymers, only propyl dimethylamine-functionalized poly(dimethylsiloxane) is soluble in CO₂ at temperatures and pressures accessible in our experiments, but even this polymer is less soluble than non-functionalized poly(dimethylsiloxane) at the same chain length. We have performed ab initio calculations on tertiary amine-containing moieties representative of some of the polymers examined experimentally. Our calculations confirm that amine-CO₂ interactions are indeed energetically favorable. However, we also find that the moiety self-interactions are typically more favorable than the CO₂-moiety interactions. This indicates that the lack of solubility of amine-containing polymers in CO₂ is a direct result of strong polymer-polymer interactions.     

High‐pressure phase equilibria for a styrene/CO2/polystyrene ternary system

To reveal the possibility of supercritical (SC)‐CO₂‐assisted devolatilization of polystyrene, the equilibrium composition data for the CO₂ phase in a styrene/CO₂/polystyrene ternary system is determined by a semistatic experimental technique. The parameters in the lattice–fluid equation of state of Sanchez and Lacombe are determined for the investigated system. The distribution coefficients of styrene between the polymer and the supercritical fluid phases are investigated experimentally at 318 and 328 K over the pressure range of 12–20 MPa. The binary interaction parameter between styrene and CO₂ is obtained by regression of the vapor–liquid equilibrium data. The interaction parameter between CO₂ and polystyrene is calculated by using the sorption data from the literature, and the interaction parameter between styrene and polystyrene is optimized by using the measured data of this study. The investigation of the distribution coefficients indicates that styrene can be removed from polystyrene by SC‐CO₂ at near room temperature and moderately high pressures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1938–1944, 2002     

High-pressure phase equilibria of Polystyrene dissolutions in Limonene in presence of CO2

Dissolution with terpenic solvents is presented as an alternative and original route to recycle Polystyrene wastes at room temperature. Limonene was the chosen solvent to carry out the dissolution process because it presents high compatibility with Polystyrene besides being natural, non toxic and relatively low cost. The solvent removal is possible thanks to supercritical CO₂ since it provides high solubility of Limonene and complete PS insolubility at moderated pressures and temperature. In order to determine the proper working conditions to conduct the precipitation of the polymer, accurate knowledge of the phase equilibrium for mixtures of carbon dioxide, Limonene and Polystyrene should be known.In this work, the solubility of Limonene in the ternary system CO₂/Limonene/Polystyrene was determined. The phase equilibrium experiments were conducted in a variable-volume view cell employing the static method. These experiments were carried out in the temperature range of 298.15–313.15 K, at pressures up to 15 MPa and in the concentration range of 0.05–0.80 g PS/ml Limonene. Initially the binary systems were studied by means of equations of state: Peng–Robinson in the case of CO₂/Limonene and Sanchez–Lacombe in the case of Limonene/PS and CO₂/PS. Predicted data were collected together with the experimental to check the agreement and to determine the limits of the ternary system formed by CO₂–Limonene–PS. It is indispensable to determine the behaviour of the ternary system to know completely the fluid phase equilibrium. The results indicate that the solubility of Limonene in the vapour phase is favoured by high pressure and temperature as well as low concentration.     

Effect of pressure on CO2 transport in poly(ethylene terephthalate)

The CO₂ solubility, permeability, and diffusion time lag in poly(ethylene terephthalate) are reported at 35° and 65°C for CO₂ pressures ranging from 0.07 to 20 atm. The subatmospheric time lag and permeability measurements were made with a glass system at North Carolina State University, while the measurements between 1 and 20 atmospheres, using an identical polymer sample, were made at The University of Texas with a metal system capable of tolerating gauge pressures up to 30 atm. The measured solubility, permeability, and time lag all show strong deviations from the well-known simple expressions for gases in rubbery polymers. The solubility isotherm is non-linear in pressure, and both θ and P are quite pressure dependent, with each showing tendencies to approach low and high pressure asymptotic limits. These effects decrease as temperature increases and would be expected to disappear at or near the glass transition where the amorphous regions become rubbery. The importance of reporting the pressure levels used in transport measurements is emphasized for gas/glassy polymer systems where transport process do not follow linear laws.     

Phase behavior on the binary and ternary mixtures of poly(isooctyl acrylate) + supercritical fluid solvents + isooctyl acrylate and CO2 + isooctyl acrylate system

Experimental cloud‐point data to the temperature of 180 °C and the pressure up to 2000 bar are presented for ternary mixtures of poly(isooctyl acrylate) + supercritical fluid solvents + isooctyl acrylate systems. Cloud‐point pressures of poly(isooctyl acrylate) + CO₂ + isooctyl acrylate system is measured in the temperature range of 60–180°C and to pressures as high as 2000 bar with isooctyl acrylate concentration of 0–44.5 wt. This system changes the pressure–temperature slope of the phase behavior curves from upper critical solution temperature (UCST) region to lower critical solution temperature (LCST) region as the isooctyl acrylate concentration increases. Poly(isooctyl acrylate) does dissolve in pure CO₂ to the temperature of 180°C and the pressure of 2000 bar. The phase behavior for poly(isooctyl acrylate) + CO₂ + 9.5, 14.8, 30.6, and 41.9 wt % dimethyl ether (DME) mixture show the curve changes from UCST to LCST as the DME concentration increases. Also, the cloud‐point curves are measured for the binary mixtures of poly(isooctyl acrylate) in supercritical propane, propylene, butane, and 1‐butene. High pressure phase behaviors are measured for the CO₂ + isooctyl acrylate system at 40, 60, 80, 100, and 120°C and pressure up to 200 bar. This system exhibits type‐I phase behavior with a continuous mixture‐critical curve. The experimental results for the CO₂ + isooctyl acrylate system are modeled using the Peng‐Robinson equation of state. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Pressure variation due to heat shock of CO2hydrate desserts

CO₂ hydrate desserts are carbonated frozen desserts in which the CO₂ is trapped in a crystalline water‐carbon dioxide structure called a CO₂ clathrate hydrate. The CO₂ concentration of the dessert enables strong perception of carbonation, but CO₂ hydrate dissociation during heat shock can cause high package pressures during storage and distribution. In this work, a model is developed for package pressure as a function of temperature, CO₂ content, package volume, dessert mass, and recipe. The model is validated by comparison with an experimental measurement of the pressure and mass of a CO₂ hydrate dessert subjected to heat shock. It is shown that during heat shock a sealed package can reach pressures greater than the ice‐CO₂ hydrate equilibrium pressure. At pressures above the ice‐CO₂ hydrate equilibrium pressure, the fraction of water crystallized in the dessert can be increased, potentially mitigating heat shock damage. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Quantification of specific interactions between CO2 and the carbonyl group in polymers via ATR-FTIR measurements

We have used in situ ATR-FTIR measurements to provide estimates of the strength of specific interactions between carbon dioxide (CO₂) and carbonyl groups in polymers such as poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc), poly(lactide) (PLA) and poly(lactide-co-glycolide) (PLGA). Polymer films were exposed to high pressure CO₂ and the carbonyl stretching vibration at 1700 cm⁻¹ and the CO₂ bending mode at 660 cm⁻¹ were studied. The observed shift in the carbonyl stretching band to higher wavenumber was attributed to dielectric effects according to the Kirkwood-Bauer-Magat (KBM) equation. On the other hand, the splitting of the CO₂ bending mode provided direct evidence of specific interactions between the polymer and CO₂. These interactions were quantified via an equilibrium constant for the association reaction between CO₂ and the carbonyl group.     

Fluid phase behavior modeling of CO2 + molten polymer systems using cubic and theoretically based equations of state

Phase equilibrium data of CO₂ + molten polymer systems are of great relevance for chemical engineers because these are necessary for the optimal design of polymer final‐treatment processes. This kind of processes needs information about gas solubilities in polymers at several temperatures and pressures. In this work, CO₂ solubilities in molten polymers were modeled by the perturbed chain‐statistical associating fluid theory (PC‐SAFT) equation of state (EoS). For comparison, the solubilities were also calculated by the lattice gas theory (LGT) EoS, and by the well‐known Peng‐Robinson (PR) cubic EoS. To adjust the interactions between segments of mixtures, there were used classical mixing rules, with one adjustable temperature‐dependent binary parameter for the PC‐SAFT and PR EoS, and two adjustable binary parameters for the LGT EoS. The results were compared with experimental data obtained from literature. The results in terms of solubility pressure deviations indicate that the vapor–liquid behavior for CO₂ + polymer systems is better predicted by the PC‐SAFT model than by LGT and PR models. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Bio-based mixed CO2-switchable surfactant for reducing viscosity of heavy oil

CO₂-switchable surfactants have significant viscosity-reducing abilities, but their applicability is limited by the complexity of their manufacture. In this work, a simple mix of CO₂-switchable bio-based surfactants N-lauroylsarcosine (LS) and glucosamine (GA) was used to reduce viscosity of heavy crude oil. Surface tensiometer was used to investigate the surface activity of LS/GA, revealing the potential for viscosity reduction. By alternating sparging of CO₂ and N₂, the switchability of LS/GA was examined and proved. It reveals that LS/GA significantly reduces the viscosity of heavy oil by emulsification, but the formed emulsion can be quickly destabilized by introduction of CO₂. The results of this study reveal that CO₂-switchable bio-based surfactants with viscosity-reducing capabilities for heavy crude oil may be produced by simple mixing, paving the way for reversible emulsification of heavy crude oil utilizing CO₂-switchable bio-based surfactant.     

Effect of the octadecyl acrylate concentration on the phase behavior of poly(octadecyl acrylate)/supercritical CO2 and C2H4 at high pressures

Pressure–composition isotherms were measured for the CO₂/octadecyl acrylate system at 45.0, 80.0, and 100.0°C and at pressures up to 307 bar. This system exhibited type I phase behavior with a continuous mixture‐critical curve. The solubility of octadecyl acrylate for the CO₂/octadecyl acrylate system increased as the temperature increased at a constant pressure. The experimental results for the CO₂/octadecyl acrylate system were modeled with the Peng–Robinson equation of state. A good fit of the data was obtained with the Peng–Robinson equation of state with one adjustable parameter for the CO₂/octadecyl acrylate system. Experimental cloud‐point data for the poly(octadecyl acrylate)/CO₂/octadecyl acrylate system were measured from 36 to 193°C and at pressures up to 2100 bar, and the added octadecyl acrylate concentrations were 11.9, 25.9, 28.0, 35.0, and 40.0 wt %. Poly(octadecyl acrylate) dissolved in pure CO₂ up to 250°C and 2100 bar. Also, adding 45.0 wt % octadecyl acrylate to the poly(octadecyl acrylate)/CO₂ solution significantly changed the phase behavior. This system changed the pressure–temperature slope of the phase‐behavior curves from an upper critical solution temperature (UCST) region to a lower critical solution temperature region as the octadecyl acrylate concentration increased. Cloud‐point data to 150°C and 750 bar were examined for poly(octadecyl acrylate)/C₂H₄/octadecyl acrylate mixtures at octadecyl acrylate concentrations of 0.0, 15.0, and 45.0 wt %. The cloud‐point curve of the poly(octadecyl acrylate)/C₂H₄ system was relatively flat at 730 bar between 41 and 150°C. The cloud‐point curves of 15.0 and 45.0 wt % octadecyl acrylate exhibited positive slopes extending to 35°C and approximately 180 bar. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 372–380, 2002     

Effects of carbon nanofiber on the dissolution and diffusion of CO2 in polypropylene nanocomposites

The effects of nanofiller with elongated structure on the dissolution and diffusion behaviors of CO₂ in polypropylene (PP)/carbon nanofiber (CNF) composites were investigated in this work. The solubility of CO₂ in PP and PP composites containing 5 wt% and 10 wt% CNF was measured by using magnetic suspension balance (MSB) combined with the experimental swelling correction by using a self-designed high-temperature and -pressure view cell at the temperatures of 200 and 220 °C and pressures up to 20 MPa. The diffusion coefficient of CO₂ in PP and PP composites was also determined from the sorption line at CO₂ pressures ranging from 5 to 10 MPa. It was found that the solubility and diffusivity of CO₂ in PP/CNF composites increased with increasing the filler content, which should be mainly attributed to the change of the distribution of free volume in the polymer matrix besides the small amount of adsorption capacity of CO₂ in CNF. A modified Henry model incorporated with Langmuir adsorption factor was proposed to correlate the solubility of CO₂ in the PP/CNF composites with an average relative deviation less than 3%. A new model based on free volume theory incorporated with the diffusion driving force factor was established to correlate the experimental diffusion coefficient of CO₂ in the PP/CNF composites within an average relative deviation of 2%.