Fickian Diffusion Model Research Articles

Controllably Biodegradable Hydroxyapatite Nanostructures for Cefazolin Delivery against Antibacterial Resistance

Multidrug resistance (MDR) is a global threat posed by continuously evolving microbial resistance against currently available antimicrobial agents. In this study, we synthesized hydroxyapatite-based porous nanocarriers with pH-dependent biodegradation, using cefazolin (CFZ) as cargo drug against MDR E. coli, S. aureus, and P. aeruginosa. Oval-shaped porous hydroxyapatite nanoparticles (opHANPs) were synthesized via core-shell method. Field emission scanning electron microscopy revealed that the average length and width of opHANPs were found to be similar to 90 and similar to 110 nm, respectively with monodispersed size and morphology. The encapsulation efficiency (EE) of CFZ was observed to be dependent on the initial concentration of the drug (EE, 41.37-92.40% with 300-2000 mu g/mL of CFZ). Brunauer-Emmett-Teller specific surface area and pore width of opHANPs were 166.73 m(2)/g and 3.3 nm, respectively, indicating hierarchal pore distribution. The pH-responsive drug release was observed from CFZ-loaded opHANPs (CFZ@opHANPs). An enhanced drug-releasing behavior was observed at lower pH (4.5, 2.5, and 1.5). The study of release kinetics revealed that at pH 7.4, drug release is due to anomalous diffusion, while at lower pH, the drug release followed fickian diffusion model. Cytotoxic and hemolytic studies showed biocompatibility of CFZ@opHANPs with HepG2 and red blood cells. The growth kinetic study and colony-forming unit assay showed the superior antibacterial potential of CFZ@opHANPs, in contrast to carrier or CFZ alone, against MDR E. coli, S. aureus, and P. aeruginosa strains.

Stretchable hydrophobic modified alginate double-network nanocomposite hydrogels for sustained release of water-insoluble pesticides

In agritechnology applications, the sustained release of pesticides plays significant roles in efficient bioavailability and environmental protection. In this study, hydrophobic derivate of sodium alginate (Ugi-SA), polyacrylamide (PAM) and montmorillonite (MMT) were utilized to construct several stretchable double-network nanocomposite hydrogels, which were used to control the release of λ-cyhalothrin. These nanocomposite hydrogels were fully characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The adoption of Ugi-SA and appropriate incorporation of MMT could significantly improve the tensile properties, pesticide-loading efficiency and sustained release performances of the hydrogels. The swelling behavior of all the hydrogels well fits into the Fickian diffusion model. The maximum fracture strain and loading efficiency of the hydrogels reached 2000% and 81.30%, respectively. The hydrogel with 5% MMT content shows the lowest cumulative release percentage of 6.68% over 87 h, and the pesticide release curves well fit into the Weibull model. These novel nanocomposite hydrogels take advantages of both the gelation property of alginate derivatives and the adsorption capacity of clays, to serve as promising potential carriers and to improve the utilization efficiency of water-insoluble pesticides.

Scalping of aroma compounds from food simulants into polyethylene terephthalate laminated steel.

Aroma scalping is a very common problem and can affect the sensory quality of packaged food. To study the aroma scalping characteristics of polyethylene terephthalate laminated steel (PET-LS), the sorption kinetics of six common aroma compounds (2-pentanone, 2-heptanone, hexanal, citral, butyl acetate, isopentyl acetate) in foods were assessed for drawn-redrawn cans made with PET-LS. Storage temperature and initial concentration were proved as important factors to affect compound sorption and diffusion for flavors. The correlation between logarithm of equilibrium absorption lnM∞ and reciprocal of absolute temperature 1/T showed good linear relationship (R2 = 0.9380-0.9998) at 4°C, 20 °C and 50 °C, and the M∞ obtained by the experiment was very close to the predicted value at 37 °C. At low initial concentration (below 500 µL L-1 ), the absorption capacity and initial concentration showed a slow linear growth trend, whereas there was a rapid change at high initial concentration. The values of diffusion coefficient D were on the order of 10-11 -10-12 m2 day-1 , which were lower than reported for other polymer materials (linear low-density polyethylene, polybutylene succinate, polylactic acid). The equilibrium absorption amount of each flavor component was dependent on the temperature under the same concentration (500 µL L-1 ). The Fickian diffusion model was used for fitting the experimental kinetics values satisfactorily (R2 = 0.9158-0.9885). © 2019 Society of Chemical Industry.

Chemisorption and kinetic mechanisms of elemental mercury on immobilized V2O5/TiO2 at low temperatures.

To investigate the effect of low temperature and catalyst filling pattern on the adsorption of Hg° by DeNOx equipment, the chemisorption and kinetic mechanisms of Hg° adsorption on 5-30%V2O5/TiO2 immobilized on glass beads at 100-160 °C were investigated. The effects of the reaction temperature, influent Hg° concentration, and V2O5 doping amount on the adsorption efficiency and capacity for Hg° were explored. The active sites for Hg° adsorption were further identified. Additionally, the adsorption kinetics were modelled using the linear driving force approximation, Fick's diffusion model, and pseudo-second-order kinetic model. Finally, the influence of immobilization on the adsorption of Hg° was also investigated. Experimental results showed that the bridged oxygen atom of V-O-V played a key role in the adsorption of Hg°. The Hg° adsorption efficiencies decreased from >90% to 40% as the reaction temperature increased from 120 °C to 160 °C for 20%V2O5/TiO2, while the adsorptive capacities for Hg° were highly influenced by the influent Hg° concentration and V2O5 doping amount. 20%V2O5/TiO2 had the highest adsorptive capacity of 2547 μg Hg°/g V2O5/TiO2 at 160 °C. The kinetic results showed that the linear driving force approximation model fit the Hg° adsorption better than the other models. The diffusion resistance increased significantly for the immobilized catalysts because the external mass transfer coefficient decreased by more than 1200-fold.

Green pH/magnetic sensitive hydrogels based on pineapple peel cellulose and polyvinyl alcohol: synthesis, characterization and naringin prolonged release

This study develops a green method to fabricate pH/magnetic sensitive hydrogels based on pineapple peel carboxymethyl cellulose (PCMC), regenerated nanocellulose (rPPNc), and polyvinyl alcohol (PVA), accompanied by in situ incorporation of Fe3O4. The rPPNc was obtained through a two-stage method involving ionic liquid swelling followed by dilute sulfuric acid hydrolysis. The SEM images revealed the porous structure of the hydrogels. The hydrogels showed a magnetic responsive behavior due to incorporation of Fe3O4, and an enhanced thermal stability at high temperature due to incorporations of rPPNc and Fe3O4. The hydrogels displayed a pH-dependent swelling behavior and swelled more due to incorporation of rPPNc. In addition, rPPNc enhanced the naringin loading and entrapment efficiency of the hydrogels, showing an optimum value at 2% addition. The naringin can be gradually released from the hydrogels, which followed Fickian diffusion model. In summary, this work provided a relatively green approach for producing nanocellulose. The prepared hydrogels can be served as promising candidate materials for drug delivery system due to the characteristics of biocompatibility, pH and magnetic sensitivity.

Homogenization of a Shrinking Core Model for Gas–Solid Reactions in Granular Particles

Reactions between gases and solid particles are commonly modeled using a shrinking core framework, where a sharp interface between an inner unreacted core and an outer product shell moves inward until the reaction is complete. However, for some physical systems this sharp divide is not present, and so a better model is needed to capture a transition region for the reaction. We are interested in large particles made of many small grains where there are strong interactions between microscale granular and macroscale particulate effects, and where a shrinking core model represents behavior at the microscale level. We obtain homogenized equations for macroscale behavior by exploiting the small ratio of granular to particle lengthscales. These macroscale equations allow for a diffuse reaction front, as well as a sharp interface between reacted and unreacted solid material. We analyze the resulting model asymptotically in the limits where the reaction time is rate-limited by chemical kinetics, and separately by diffusion, determining the thickness of the reaction front. Numerical simulations support the law of additive reaction times, which states that the total reaction time is given as the sum of the conversion times under these limits. We further show how the model results can be extended to incorporate the transport of the product gas out of the solid particle, using a binary Fickian diffusion model. In metallurgical production the particle size and porosity are known to influence reaction times. Our results help quantify these effects and may be an aid in raw material selection.

Evaluation of Effectiveness Factors for Multicomponent Diffusion Models Inside 3D Catalyst Shapes

On an industrial scale, the efficiency of heterogeneous catalysis is commonly subject to diffusive transport limitations. The binary friction model (BFM) combines Maxwell–Stefan-type diffusion, pore effects and viscous contributions for multicomponent reaction mixtures. A variety of catalyst shapes have been developed over the years to overcome transport problems. However, rigorous modeling of multicomponent diffusion–reaction problems in 3D geometries remains an ongoing challenge. We successfully applied the BFM to nine shapes, all varying in size and catalyst loading. The volume-to-surface ratio and the curvature of the bodies were found to be the characteristic features of the pellets, describing the reaction–diffusion interplay. With this, the 3D shape can be adequately approximated with straightforward 1D strategies. Finally, a comparison to Fickian diffusion models highlights the similarities and discrepancies to the Maxwell–Stefan concept of the BFM. These findings can contribute to an integral description of 3D reaction–diffusion problems in homogeneously distributed, mesoporous catalysts.

Study of hygroscopic stresses in asymmetric biocomposite laminates

The hygro-mechanical behaviour of a bio-sourced composite material (MAPP/flax) is experimentally investigated through the characterization of its moisture diffusion and elastic properties, as well as the in-plane hygroscopic swelling of a unidirectional ply sequence and curvature in the case of an asymmetric lay-up sequence. From these considerations, we propose a hygro-mechanical model for the material behaviour, based on a Fickian diffusion model solved in 1D with a finite difference method, and coupled to a modified mechanical model based on laminate theory. The proposed model takes into account the evolution of the mechanical properties as well as hygroscopic swelling during moisture uptake to predict the stress state during water sorption of a biocomposite. Results show that sorption kinetics is dependent on the lay-up sequence of the biocomposite structure. The stress state determined from the thickness of the asymmetric lay-up shows that most of the plies (approx. 75% of the whole laminate) are subjected to a compressive stress along their in-plane direction transverse to the fibres. This stress distribution may lead to a decrease in the free-volume of the material, thus modifying the hygroscopic properties by reducing its maximum moisture content compared to the unidirectional laminate (the stress distribution being equal to zero for this latter laminate when saturation is reached).

Polypyrrole actuators: the effects of polymer thickness and voltage scan rate on fractional charging and isotonic actuation strain

For conducting polymer actuators to be practically useful, they need to be able to generate large forces and displacements and respond quickly. The simplest way to generate larger forces is to produce thicker actuators, but this approach has a negative impact on the response time. The effects of polypyrrole film thickness and voltage scan rate on the electrochemical actuation strain rate are investigated in this study. The rate of oxidative charging is shown to follow a standard Fickian diffusion model suggesting that the migration of ions into the polymer from the electrolyte is the dominant rate-determining mechanism. The migration rate is slow with full oxidation requiring several minutes for film thicknesses of just 10 μm. The free strains generated were found to be directly proportional to the oxidative charge passed. The isotonic actuation strains were additionally reduced by increasing applied stress and this effect was attributed to the increase in Young’s modulus that occurs during polypyrrole oxidation. A simple model is presented that predicts the change in modulus during oxidation and gives reasonable estimates of the isotonic actuation for PPy actuators of different thickness and when subjected to different stresses.

Adsorption Equilibrium and Kinetics of Methanol Vapor on Zeolites NaX, KA, and CaA and Activated Alumina

Methanol vapor as a contaminant presented in industrial streams leads to catalysts deactivation. Therefore, it needs deep removal with adsorption technique. The isotherms and effective diffusion coefficients of methanol vapor are essential to design the purification process. The equilibrium sorption of methanol steam on commercial zeolites NaX, KA, and CaA and activated alumina were tested using an intelligent gravimetric analyzer, respectively. The equilibrium experiments were carried out at 303.2 K and pressures of up to 19.6 kPa, and the results obtained were fitted with the Dubinin–Astakhov (D-A) model. Moreover, the diffusion of methanol vapor in the adsorbents was investigated, and the effective diffusion coefficients were obtained with fitting the Fick diffusion model. The adsorbents are compared on the basis of adsorption capacities for methanol steam, and the descending order of zeolites is NaX > CaA > KA > Al2O3. The sorption equilibrium experimental results of methanol steam on NaX, KA, and CaA...

Experimental and theoretical analysis of drying grapes under an indirect solar dryer and in open sun

Abstract In the present work, the drying behavior of grapes under open sun and into indirect solar dryer was studied. The indirect solar dryer was designed in the Solar Energy and Environment Laboratory of Mohammed V University, Rabat, Morocco. It consists of a solar collector, a heat exchanger, a water storage tank and a drying chamber. Results show that during off sunshine hours, the heat transfer from the water storage tank kept the grapes temperature higher than ambient temperature. Drying results indicated that the times required for drying grapes starting at the initial moisture contents of 79.8% (w.b.) till final moisture contents of 20.2% (w.b.) were 120 h and 201 h in indirect solar and open sun drying, respectively. The drying data were fitted to 10 thin-layer drying models to describe and compare the drying characteristics of the grapes. Comparisons were based on the coefficient of correlation (R), root mean square error (RMSE) and reduced chi-square (χ2). Midilli et al. model is found to best depict grapes drying behavior in both indirect solar and open sun drying. The evaluated values of the effective moisture diffusivity of grapes sun drying and grapes indirect solar drying when applying the Fick's diffusion model were 2.34 × 10−11 and 4.08 × 10−11 m2/s, respectively.

Adsorption isotherms, kinetics and thermodynamic simulation of CO2-CSAC pair for cooling application

This research article proposes to develop a waste heat driven single-stage adsorption-based cooling system by selecting CO2 and indigenous coconut shell based activated carbon (CSAC) as the adsorbate/adsorbent pair. The CO2 adsorption isotherms and kinetics of activated carbon are measured at different temperatures (273–368 K) using volumetric method. In order to illustrate adsorption isotherms, experimental data of CO2 uptake is correlated with the Langmuir and Dubinin-Astakhov (D-A) models. On the other hand, Linear Driving Force (LDF) and Fickian Diffusion (FD) models are utilized to explain adsorption kinetics data. Fugacity and pseudosaturation pressure of CO2 plays a significant role in the estimation of high-pressure CO2 adsorption and thermodynamic properties above the critical temperature of CO2, and these parameters are evaluated using adsorption isotherms data. The key thermodynamic properties and kinetics parameters of the assorted pair are estimated using measured adsorption isotherms and kinetics data which are used for the thermodynamic analysis of CO2-CSAC pair based cooling system. The maximum theoretical values of SCE and COP of CO2-CSAC pair are obtained as 12.52 kJ kg−1 and 0.10, respectively at the regeneration temperature of 80 °C along with the evaporator temperature of 15 °C.

Monitoring the water absorption in GFRE pipes via an electrical capacitance sensors

One of the major problems in glass fiber reinforced epoxy (GFRE) composite pipes is the durability under water absorption. This condition is generally recognized to cause degradations in strength and mechanical properties. Therefore, there is a need for an intelligent system for detecting the absorption rate and computing the mass of water absorption (M%) as a function of absorption time (t). The present work represents a new non-destructive evaluation (NDE) technique for detecting the water absorption rate by evaluating the dielectric properties of glass fiber and epoxy resin composite pipes subjected to internal hydrostatic pressure at room temperature. The variation in the dielectric signatures is employed to design an electrical capacitance sensor (ECS) with high sensitivity to detect such defects. ECS consists of twelve electrodes mounted on the outer surface of the pipe. Radius-electrode ratio is defined as the ratio of inner and outer radius of pipe. A finite element (FE) simulation model is developed to measure the capacitance values and node potential distribution of ECS electrodes on the basis of water absorption rate in the pipe material as a function of absorption time. The arrangements for positioning12-electrode sensor parameters such as capacitance, capacitance change and change rate of capacitance are analyzed by ANSYS and MATLAB to plot the mass of water absorption curve against absorption time (t). An analytical model based on a Fickian diffusion model is conducted to predict the saturation level of water absorption (MS) from the obtained mass of water absorption curve. The FE results are in excellent agreement with the analytical results and experimental results available in the literature, thus, validating the accuracy and reliability of the proposed expert system.

Preparation and Characterization of Superabsorbent Polymers Based on Starch Aldehydes and Carboxymethyl Cellulose.

Superabsorbent polymers (SAPs) are crosslinked hydrophilic polymers that are capable of absorbing large amounts of water. Commercial SAPs are mostly produced with acrylic acid that cannot be easily biodegraded. Therefore, in this study, polysaccharide-based SAPs using carboxymethyl cellulose as a major component were prepared. Starch aldehydes and citric acid were selected due to their environment-friendly, non-toxic, and biodegradable properties compared to conventional crosslinking agents. Starch aldehydes were prepared by periodate oxidation, which forms aldehyde groups by taking the places of C–OH groups at C-2 and C-3. Furthermore, starch aldehydes were analyzed through the change in FT-IR spectra, the aldehyde quantitation, and the morphology in FE-SEM images. In the crosslinking of polysaccharide-based SAPs, the acetal bridges from starch aldehydes led to a large amount of water entering the network structure of the SAPs. However, the ester bridges from citric acid interfered with the water penetration. In addition, the swelling behavior of the SAPs was analyzed by the Fickian diffusion model and the Schott’s pseudo second order kinetics model. The relationship between swelling behavior and morphology of the SAPs was analyzed by FE-SEM images. In conclusion, polysaccharide-based SAPs were well prepared and the highest equilibrium swelling ratio was 87.0 g/g.

In-situ characterization of moisture absorption and hygroscopic swelling of silicone/phosphor composite film and epoxy mold compound in LED packaging

In this paper, moisture absorption/desorption and hygroscopic swelling of silicone/phosphor composite film and epoxy mold compound (EMC) used in chip-on-board (COB) LED packaging is studied with in-situ characterization. Material properties, including diffusivity, activation energy, saturated moisture concentration and the coefficient of hygroscopic swelling, are extracted from the experimental data. For silicone/phosphor film, the moisture diffusion can be described by the conventional Fickian diffusion model. However, the saturated moisture concentration increases with temperatures under the same relative humidity condition. The dependence of saturated moisture concentration on temperature is characterized by an Arrhenius-like equation, and the net absorption heat is found to be 8–11 kJ/mol. Furthermore, the silicone/phosphor composite film shows reversible diffusion process during absorption and desorption cycle, which confirms the Fickian behavior of moisture absorption. Moisture diffusion in EMC, on the other hand, exhibits non-Fickian diffusion, and thus, a dual stage diffusion model is adopted to fit experimental data. Moreover, EMC shows partially non-reversible moisture absorption during absorption and desorption cycle, which is consistent with the dual-stage model description. In hygroscopic swelling testing, silicone/phosphor film shows a permanent swelling during moisture absorption despite that the moisture absorption is completely reversible. EMC shows partially reversible swelling after moisture is removed, which indicates the residual moisture in material. Further study is needed to understand the mechanism of permanent hygroscopic swelling for silicone/phosphor composite during moisture absorption and desorption.

Investigating the structural effect of electrospun nano-fibrous polymeric films on water vapor transmission

Abstract Electrospun polymers have many applications in the industry. However, the structure of these polymers has been less widely considered by researchers. In this work, the structural effect of electrospun and casted films of polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) polymers on water vapor transmission were investigated. Sorption of water vapor was measured at 35, 60 and 80 °C and different relative humidities. The diffusion coefficients were calculated based on mass changes of the polymer sample. The water vapor transmission rate (WVTR) was also measured at 35 °C and 90% relative humidity. The results indicated that electrospun nano-fibrous polymers (ESNPs) absorb much higher water vapor compared to non-porous casted polymers. The interaction of water molecules with mentioned polymers was investigated based on Flory-Huggins theory. The Flory-Huggins interaction parameter of electrospun films was less than casted films, suggesting much better interaction of water molecules with electrospun films. It was also found that electrospun films have anomalous kinetic behavior and do not obey the Fickian diffusion model. Finally, it was revealed that ESNPs show less resistance to water vapor transmission and they are good candidates for the applications of water vapor separation using membranes.

Crosslinked Polyacrylamide Composite Hydrogels Impregnated with Fly Ash: Synthesis, Characterization and Their Application as Fractures Sealant for High Water Producing Zones in Oil and Gas Wells

Polymeric hydrogels are designed to serve many purposes in various fields of human endeavor. Herein, crosslinked polyacrylamide (PAM) composite hydrogels impregnated with coal fly ash (CFA) were synthesized, characterized and tested as fracture sealing agents in high water producing permeable zones in petroleum industry. The concept of utilizing CFA as an inorganic additive in the matrix of hydrogel emanates from the fact that CFA constitutes majorly alumina and silica. Both chemical oxides can induce the CFA to promote the inherent properties of hydrogel. Polyethyleneimine (PEI) was chosen as the crosslinking agent. Neat PAM/PEI hydrogel and PAM/PEI–CFA hydrogels at various CFA loadings (0.5, 1 and 2 wt%) were synthesized via a transamidation reaction pathway. The developed hydrogels were characterized by hybrid rheometer, FTIR, SEM and XRD instruments. Rheological results reveal that the PAM/PEI–CFA composite hydrogels embedded with various CFA quantities were more elastic than the neat PAM/PEI hydrogel, indicating the dispersion and reinforcing effect of CFA. The functional groups of these hydrogels were confirmed by the FTIR while SEM analysis show that the surface micrographs of neat PAM/PEI hydrogel and PAM/PEI–CFA1 hydrogel were porous in several regions. In contrast, the micrographs of PAM/PEI–CFA2 and PAM/PEI–CFA3 hydrogels demonstrated dense and “net-like” structural patterns. Further, XRD analysis revealed that CFA impregnation has a significant effect on the bulk structural properties of the fabricated hydrogels. The swelling rates of these hydrogels were determined by the gravimetric method and their diffusion parameters evaluated using Fickian diffusion and Schott-order kinetic models. Efficacy of the PAM/PEI–CFA composite hydrogel as fractures sealant in oil and gas wells was conducted at a typical reservoir temperature, 90 °C, and the outcome demonstrated considerable sealing potency.

Empirical and diffusion models of rehydration process of differently dried pumpkin slices

Abstract The present study investigated the rehydration kinetics of dried pumpkin slices issued from different drying operations, namely airflow drying (AFD), freeze-drying (FD), Vacuum Multi Flash Drying (VMFD) and Swell-drying (SD) which inserts Instant Controlled Pressure Drop (DIC) Texturing between two AFD stages (AFD + DIC + AFD). Rehydration process depends on dehydration methods. It has been noticed that the slowest rehydration process has been observed for AFD whilst VMFD, FD, and SD averred short rehydration time. Experimental rehydration curves were performed through empirical and diffusion models. Hence, it has been noticed that Weibull has provided the best rehydration fitting curve. In other hand, Fick's diffusion models were also used to describe kinetics of rehydration process. They were characterized by two effective diffusivity coefficients D eff 1 and D eff 2 for AFD and VMFD, and three effective diffusivity coefficients in the case of FD and SD (AFD + DIC + AFD). The temperature dependence of the diffusivity coefficients was also described by Arrhenius-type relationship, with adequate activation energy levels.

Synthesis and Characterization of Superabsorbent Polymer Based on Carboxymethyl Cellulose-graft-Itaconic Acid

Superabsorbent polymers of carboxymethyl cellulose-graft-itaconic acid were synthesized using potassium persulfate as a free radical initiator in the presence of N,N′-methylene bisacrylamide as a crosslinker using solution polymerization technique. The structures of the grafted copolymers were characterized by FT-IR spectroscopy and thermogravimetric analysis. The effect of reaction variables such as concentration of carboxymethyl cellulose, itaconic acid, initiator, crosslinker, and neutralizing agent were optimized to achieve a hydrogel with high swelling capacity of 74 g/g (DI water) and 18 g/g (0.9 wt% NaCl solution). The swelling kinetics of the prepared SAP were analyzed by applying the Fickian diffusion model and the Schott’s pseudo second order kinetics model. The diffusion exponents in the Fickian model, n, showed values of 0.73-0.93, indicating that chain relaxation behavior during absorption had a large effect on total absorbency.

Noble-gas-infused neoprene closed-cell foams achieving ultra-low thermal conductivity fabrics.

Closed-cell foams are widely applied as insulation and essential for the thermal management of protective garments for extreme environments. In this work, we develop and demonstrate a strategy for drastically reducing the thermal conductivity of a flexible, closed-cell polychloroprene foam to 0.031 ± 0.002 W m−1 K−1, approaching values of an air gap (0.027 W m−1 K−1) for an extended period of time (>10 hours), within a material capable of textile processing. Ultra-insulating neoprene materials are synthesized using high-pressure processing at 243 kPa in a high-molecular-weight gas environment, such as Ar, Kr, or Xe. A Fickian diffusion model describes both the mass infusion and thermal conductivity reduction of the foam as a function of processing time, predicting a 24–72 hour required exposure time for full charging of a 6 mm thick 5 cm diameter neoprene sample. These results enable waterproof textile insulation that approximates a wearable air gap. We demonstrate a wetsuit made of ultra-low thermally conductive neoprene capable of potentially extending dive times to 2–3 hours in water below 10 °C, compared with <1 hour for the state-of-the-art. This work introduces the prospect of effectively wearing a flexible air gap for thermal protection in harsh environments.