Amount Of Residual Solvent Research Articles

New Surface Modification of Hydrophilic Polyvinyl Alcohol via Predrying and Electrospinning of Hydrophobic Polycaprolactone Nanofibers.

Despite the excellent oxygen barrier and biodegradability of polyvinyl alcohol (PVA), its poor physical properties owing to its inherent hydrophilicity limit its application. In this paper, we report a novel surface modification technique for PVA films, involving the control of the predrying conditions (i.e., amount of residual solvent) of the coated PVA film and adjusting the electrospinning process of hydrophobic polycaprolactone (PCL) nanofibers onto the PVA films. The residual solvent of the coated PVA film was varied by changing the predrying time. A shorter predrying time increased the residual solvent content significantly (p < 0.05) and the flexibility of the coated PVA film. Moreover, scanning electron microscopy depicted the improved physical binding of hydrophobic PCL nanofibers to the hydrophilic PVA surface with increased penetration depth to the PVA film with shorter drying times. The PVA/PCL composite films with different predrying times and electrospun PCL nanofibers exhibited an apparent increase in the contact angle from 8.3° to 95.1°. The tensile strength of the pure PVA film increased significantly (p < 0.05) from 7.5 MPa to 77.4 MPa and its oxygen permeability decreased from 5.5 to 1.9 cc/m2·day. Therefore, our newly developed technique is cost-effective for modifying the surface and physical properties of hydrophilic polymers, broadening their industrial applications.

Investigating Nano-Sized Dispersity and High Crystallinity of Perfluoro-Sulfonic Acidionomer in Polymer Electrolyte Fuel Cell Electrodes Via Electrospray Deposition

Polymer electrolyte fuel cells (PEFCs) hold great promise for mitigating the worldwide climate crisis by tapping into the potential of producing clean energy from renewable sources. However, widespread commercial adoption of PEFCs requires addressing the challenges associated with PEFC performance and durability, particularly concerning electrode materials and design. The PEFC electrode is a crucial component of PEFC performance, with the ionomer playing a vital role as both an electrode binder and proton conductor. Nano-sized dispersity and high crystallinity of the ionomer are vital properties that are crucial for achieving enhanced performance and durability. However, existing methods for fabricating PEFC electrodes have been unable to attain these desirable ionomer characteristics. In this work, we propose a novel approach to fabricating PEFC electrode architectures with ionomers possessing nano-sized dispersity and high crystallinity using the electrospray deposition (ESD) technique. In the ESD process, a precursor solution is atomized into charged droplets, while evaporating the solvent, and results in the formation of advanced electrode with vertical architecture that exhibits high crystallinity of ionomer, in contrast to much lower crystallinity of those fabricated by conventional decal methods. The ionomer characteristics significantly impact the overall fuel cell performance and durability. Therefore, controlling the residual solvent content during the ESD process is a crucial aspect that is vital for achieving the desired ionomer characteristics. The residual solvent content is tuned by investigating the initial mixed solvent ratio, substrate temperature, and distance between the nozzle to substrate. By fine-tuning the residual solvent content and optimizing the deposition parameters, the ESD technique can overcome the limitations of traditional fabrication methods, resulting in PEFC electrodes that offer enhanced performance, increased durability, and improved energy efficiency. The electrospray deposition (ESD) technique provides precise control over the amount of residual solvent required for deposition, making it a scalable technique. This work shows that the residual solvent content of PEFC electrodes significantly impacts the ionomer crystallinity and the electrode architecture using a well-controlled and optimized electrospray technique, without the use of any additives or special ionomer. In summary, this work demonstrates a novel approach to fabricating PEFC electrode architectures with ionomers possessing nano-sized dispersity and high crystallinity using the electrospray deposition technique. This approach provides precise control over the residual solvent content, allowing for enhanced performance and increased durability of PEFC electrodes due to the high-crystallinity of the ionomer. These findings have important implications for the development of sustainable energy technologies and contribute to the ongoing efforts towards mitigating the worldwide climate crisis.

OMNI: Gas Chromatograph Captures Seven Common PET Radiotracer Analytes in under 5 Minutes.

A novel gas chromatography method was developed using automatic injections to identify and quantify the amount of residual solvents or analytes in samples of fluorine-18 and carbon-11 radiopharmaceuticals. This approach evaluates seven analytes in less than 5 versus 13 min of acquisition time. The method additionally includes a 3 min bakeout to aid in the removal and carry-over of higher-boiling impurities. Chromatographic parameters such as column temperature, hold time, column pressure, flow rate, and split ratios were adjusted and optimized to analyze radioactive drug samples containing analytes which include methanol, ethanol, acetone, acetonitrile, triethylamine, N,N-dimethylformamide, and dimethyl sulfoxide. The relative standard deviation for each solvent was determined to be no greater than 1.6%. The method limit of detection (LOD) and limit of quantification (LOQ) were between 0.053 and 0.163 and 0.000 (5.791 × 10-6) and 0.520 mg/mL, respectively. This GC technique, using flame ionization detection (FID), was validated and is currently employed for the routine quality control of all approved IND and RDRC PET radiopharmaceuticals at our center.

Optical properties of multilayer Er-doped Ga1As39S60 chalcogenide glass thin films deposited by spin coating

In order to produce spin-coated chalcogenide glass thin films with higher thickness and lower residual solvent, multilayer lamination of 0.85 at.% Er-doped Ga1As39S60 chalcogenide glass was studied. Er was doped into the Ga1As39S60 glass by melt quenching technique. Solutions for spin coating were prepared from glass powders dissolved in propylamine at a concentration of 0.2 gr/ml. Films with 1–4 layers were spin coated using multiply deposition/two step thermal stabilization procedure. The average thickness for each layer was about 0.48 μm as the 4-layered sample was 1.76 μm thick. Influence of multilayer lamination on optical parameters of films and the amount of residual solvent was studied by examining UV visible infrared spectroscopy. According to AFM images, surface roughness of layers decreased with increasing number of layers from 3.6 nm to 0.78 nm. No interfaces were observed from SEM images of multi layered cross section. Although all of the films demonstrated PL emission at 1.55 μm, emission slightly decreased with increasing the number of layers.

The Impact of Residual Solvent on the Performance of Catholyte for Solid-State Batteries

All-solid-state batteries (ASSBs) are attracting more attention in recent years due to their safety, use of Li metal anode, higher energy density, and so on. However, high interfacial resistance, especially on the cathode side, is one of the major challenges to commercialize ASSBs. Catholyte, both liquid or solid, is added to lower the cathode/electrolyte interfacial resistance. In this study, we found residual solvent remaining in a solid polymer catholyte after incomplete drying can dramatically lower the interfacial resistance between LLZO electrolyte and NMC cathode active material. Cells with different amounts of residual solvent are compared to optimize the solvent loading. With residual solvent, the capacity can reach 135 mA h/g when cycled at 25 °C and 0.5 C. Capacity retention is more than 60% after 125 cycles. The cell performs even better at low temperatures than a cell with liquid catholyte. This study demonstrates the possibility of widely differing results for ASSBs when the cathode is not completely dried. Also, it provides a hint for a potential method to lower the cathode/electrolyte interfacial resistance.

Green solvents, potential alternatives for petroleum based products in food processing industries

Solvent extraction is used at the industrial scale for extraction of oil, flavouring and functional compounds from the source materials. Easy availability at lower price makes petroleum based solvents (e.g., hexane, petroleum ether, etc.) the preferred choice for solvent extraction. However, some amount of the solvent always escapes to the environment during the extraction process and the yield product also contains some amount of residual solvent. This causes hazard not only to the environment and people at large, but also affects the manpower involved in the solvent extraction industry in particular. This has led to the search of alternative solvents which have lower toxicity and are environmentally safe. Green solvents appear to be a potential candidate for this. Solvent extraction studies performed using green solvents have revealed their equal or higher extraction efficacy to that of petroleum based products. This review paper aims to provide comprehensive information about the studies pertaining to the application of green solvents as a safer and their potential for replacement of petroleum based solvents for extraction of fat soluble compounds. In addition, health and environmental aspects of greens solvents along with their associated advantages-disadvantages has also been discussed in this paper.

Determination of contaminants in artisanal cannabis products used for childhood epilepsy in the Australian community: A sub-analysis of the ‘PELICAN’ study

Despite recent approval of pharmaceutical-grade cannabis products for the treatment of childhood epilepsy, some families continue to use artisanal cannabis products as a way to manage seizures in their children. However, such products are typically of unknown composition and quality, and may therefore pose an unpredictable health risk to the child. In the present analysis, 78 samples of cannabis products collected (as part of a previous study) from families of children with epilepsy (average age 8.8 ± 4.6 years) were analyzed for heavy metals (arsenic, cadmium, lead, and mercury), residual solvents (panel of 19 solvents) and pesticides (panel of 57 pesticides). Due to small sample volumes obtained, only a subset of samples was used in each analysis. Results showed that no cannabis sample exceeded the toxicity limits for heavy metals (n = 51 samples tested). Of the 58 cannabis samples tested for residual solvents, 17 (29%) contained concentrations of ethanol or isopropanol above the generally accepted limit of 5000 parts per million. With the volumes consumed, it was thought unlikely that children were consuming hazardous amounts of residual solvents, although this could not be ruled out in every case. Most samples (n = 31 samples tested) yielded inconclusive results for the pesticides, although one sample contained concentrations of bifenthrin that were 4.9 times higher than the acceptable limit. Overall, these results highlight the need for improved access to quality-assured cannabis products and the education of doctors, patients, and artisanal manufacturers around the contaminant exposure risk in unregulated cannabis products.

Interlayer molecular migration and reaction in an epoxy-polyurethane coating system: Implications for the system hardness

Curing of coatings under solvent evaporation-suppressed conditions, can lead to trapping of solvents and subsequent solvent migration into mid- or topcoats in a multilayer coating system. Such migrations may have adverse effects on the coating mechanical properties, hardness in particular.Using a two-layer epoxy-polyurethane (PU) coating system with a strong practical significance for the heavy industry, the aim of the present work was to quantify the migration-reaction phenomenon for selected alcohols (co-solvents), and map the underlying mechanisms. In the experimental series undertaken, the evaporation rate of solvents was measured gravimetrically, and the urethane group formation quantified by the use of Fourier-transform infrared spectroscopy (FTIR). Simultaneously, the transient hardness development of the epoxy-PU system was followed and the coating surface morphology studied with a three-dimensional profilometer. In addition, to estimate the required coating curing time for dry-to-handle conditions, high-pressure compression measurements were conducted.As expected, due to solvent build-up in a closed exposure chamber, the amount of residual solvents in the epoxy-PU coating system increased under the evaporation-suppressed conditions. In particular, the residual 1-butanol in the epoxy primer migrated to the PU topcoat, where it reacted with the isocyanate reactants. The reduced cross-linking density, as a consequence of this undesired reaction, and the simultaneous suppressed solvent evaporation, resulted in an insufficient hardness development of the PU topcoat, despite continuous evaporation of solvents and consumption of isocyanates were indeed observed.To elucidate the underlying mechanisms, a kinetic study on the reactivity of 1-butanol with the isocyanate crosslinker was also conducted, and it showed a two orders of magnitude higher reaction rate than for the polyol reactant in the PU system, which explains the negative effects of the 1-butanol migration. In comparison, 2-butanol was less reactive towards isocyanates, and could substitute 1-butanol, whereby, under the evaporation-suppressed conditions, the hardness development of the epoxy-PU coating system was significantly improved and the curing time required for high-pressure dry-to-handle conditions reduced from more than eight to four days.The results of this work provide insight and guidelines for how to optimize a formulation to obtain adequate curing of the epoxy-PU coating system under evaporation-suppressed conditions.

Analysis and characterization of cefixime by using IR, HPLC and gas chromatography

To develop a new, simple, sensitive, accurate, and economical analytical methods for the estimation of related compounds in Cefixime formulations. Validate the proposed methods in accordance with USP, EUROPE and ICH guidelines for the intended analytical application. Identify whether the given sample is Cefixime by IR spectroscopy and solubility test. To determine the wavenumber in cm-1 (reciprocal to wave length region) of given sample by Infrared Spectroscopy. To determine the moisture content present in the given sample of Cefixime by Karl Fischer method. Find out the assay and related substances (impurities) of given Cefixime by using the validated method with help of High performance Liquid Chromatography. Estimate the amount of Residual solvents by Gas Chromatography. The tests were performed as per the requirements of EUROPE monograph for Cefixime. Keywords: Cefixime, IR, HPLC and gas chromatography

Solvent-Assisted Secondary Drying of Spray-Dried Polymers

PurposeThe purpose of this work is to introduce solvent-assisted secondary drying, a method used to accelerate the residual solvent removal from spray dried materials. Spray-drying is used to manufacture amorphous solid dispersions, which enhance the bioavailability of active pharmaceutical ingredients (APIs) with low aqueous solubility. In the spray-drying process, API and excipients are co-dissolved in a volatile organic solvent, atomized into droplets through a nozzle, and introduced to a drying chamber containing heated nitrogen gas. The product dries rapidly to form a powder, but small amounts of residual solvent (typically, 1 to 10 wt%) remain in the product and must be removed in a secondary-drying process. For some spray-dried materials, secondary drying by traditional techniques can take days and requires balancing stability risks with process time.MethodsSpray-dried polymers were secondary dried, comparing the results for three state-of-the-art methods that employed a jacketed, agitated-vessel dryer: (1) vacuum-only drying, (2) water-assisted drying, or (3) methanol-assisted drying. Samples of material were pulled at various time points and analyzed by gas chromatography (GC) and Karl Fischer (KF) titration to track the drying process.ResultsModel systems were chosen for which secondary drying is slow. For all cases studied, methanol-assisted drying outperformed the vacuum-only and water-assisted drying methods.ConclusionsThe observation that methanol-assisted drying is more effective than the other drying techniques is consistent with the free-volume theory of solvent diffusion in polymers.

Residual Solvents in Nanomedicine and Lipid-Based Drug Delivery Systems: a Case Study to Better Understand Processes

Complexities surrounding the manufacture and quality control of nanomedicines become increasingly apparent. This research article offers a case study to investigate how, at the laboratory scale, various stages of liposome and nanoparticle synthesis affect the amount of residual solvent found in the formulations. The objective is to bring insights on the reliability of each of these processes to provide final products which meet regulatory standards and facilitate identifying possible bottleneck early during the development process. The residual solvent at various stages of preparation and purification was measured by headspace gas chromatography. Liposomes were prepared by two different methods with and without solvent. Polymer nanoparticles prepared via nanoprecipitation and purified by ultrafiltration were studied. The effects of purification by size exclusion chromatography and dialysis were also investigated. The complete removal of residual solvent requires processes which go beyond usual preparation methods. This work might prove valuable as a reference for scientists of different fields to compare their own practices and streamline the translation of nanomedicines into efficacious and safe drug products.

Effect of tetrahydrofuran on poly(methyl methacrylate) and silica in the interfacial regions of polymer nanocomposites

The effects of tetrahydrofuran (THF) on the physical properties of poly(methyl methacrylate) at (PMMA)/silica nanoparticle interfaces in polymer nanocomposites were investigated via differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) analysis. Amorphous structures containing PMMA chains with large numbers of trans-gauche conformers were observed in the annealed samples. The amorphous structures in the samples cast from THF suspensions contained PMMA chains rich in trans–trans conformers. These amorphous structures differed from those of neat PMMA prepared without silica. Although the polymer chain mobility was reduced due to interactions between PMMA and the silica nanoparticles, trans–trans-enriched PMMA chains within the amorphous structures were less affected by these interactions. When the amorphous structures were heated above the glass transition temperature of PMMA, the proportion of trans–gauche conformers increased. When the neat PMMA samples were dried at room temperature, the glass transition temperature (Tg) increases linearly with the decrease in the amount of residual solvent. However, even if the residual solvent is extrapolated to 0 wt%, the Tg is significantly lower than the bulk Tg despite no residual solvent. The Tg of heat-dried samples heat treated at 120 °C also increases linearly with decreasing residual solvent content. However, Tg was significantly different depending on the drying temperature even with the same residual solvent amount. These results indicated that the PMMA samples dried at room temperature have a distinctly different molecular mobility from the heated sample.

Effects of residual solvent in printed phosphorescent emissive thin films as, the origin of limited efficiency in organic light emitting diodes

Using printed organic materials to fabricate organic light emitting diodes (OLEDs) is a low-cost process and one of the most innovative deposition technologies. Nozzle jet printing is a facile method with the advantages of high speed and large area fabrication. However, the printing process leaves residual solvent in the deposited organic films. How that remaining solvent affects the performance of the OLEDs, and the fundamental mechanism of that effect, is still unclear. In this study, we investigated the effect of residual solvent in a jet printed phosphorescent emissive layer. Gas chromatography-mass spectrography (GC–MS) was used to measure the amount of residual solvent, which was dependent on the film drying environment. The printed phosphorescent films exhibited weak intersystem crossing and decreased coupling between the vibrational states of the tris[2-(p-tolyl)pyridine]iridium(III) (Ir(mppy)3) in measurements of ultraviolet–visible absorption (UV–vis Abs), photoluminescence (PL), and electroluminescence (EL). The deterioration of the photophysical characteristics of the phosphorescence was attributed to the polaronic effect of the residual solvent molecules. The dipoles of the solvent molecules influenced the orbitals of surrounding organic molecules, and those perturbations induced nonradiative relaxation of the excitons. There was no shift in the peaks, but the intensities of the photophysical measurements decreased, indicating that the deterioration in phosphorescence was not chemical degradation. Finally, when the amount of residual solvent increased, the current density and the efficiency of the fabricated OLED decreased. The residual solvent also resulted in efficiency roll-off at high luminance in the devices.

Effective Antarctic krill oil extraction using switchable hydrophilicity solvents

Antarctic krill has been widely studied because of its abundant biomass, rich nutritional value, and great production potential. Notably, krill oil (KO) is rich in phospholipids (PLs), polyunsaturated fatty acids (PUFAs), and astaxanthin. A method based on a green switchable hydrophilicity solvent N,N-dimethylcyclohexylamine (DMCHA), which can reversibly change from oil soluble to water soluble in the presence of CO2 was used to extract KO from frozen Antarctic krill as it consumes less energy than traditional methods. We showed that DMCHA destroyed the surface structure of Antarctic krill and accelerated the dissolution of KO. In addition, this method enabled the PL extraction to reach up to 80.2% of total PLs, among which PC accounted for the highest proportion, up to 90.91% in PL. In fact, the astaxanthin extraction reached up to 81.44% of total astaxanthin while the fatty acid (FA) extraction up to 84.35%. The KO extracted through DMCHA was rich in PUFA, up to 47.74%, and the content of EPA + DHA reached 42.16% of total FA content. Furthermore, the amount of residual solvent in the lipid phase was just 0.23% of the DMCHA used for the extraction and the recovery rate of solvent was up to 93.2%. Our results demonstrated the high efficiency of oil extraction and the environmental friendliness of this method.

Electrospun Bioresorbable Membrane Eluting Chlorhexidine for Dental Implants.

To prevent the uncontrolled development of a pathogenic biofilm around a dental implant, an antimicrobial drug-release electrospun membrane, set up between the implant and the gingival tissue, was developed by taking several technical, industrial and regulatory specifications into account. The membrane formulation is made of a blend of poly(l-lactic–co–gycolic acid) (PLGA, 85:15) and poly(l-lactic acide–co–ɛ-caprolactone) (PLC, 70:30) copolymers with chlorhexidine diacetate (CHX) complexed with β-cyclodextrin (CD). The amount of residual solvent, the mechanical properties and the drug release kinetics were tuned by the copolymers’ ratio, between 30% and 100% of PLC, and a CHX loading up to 20% w/w. The membranes were sterilized by γ-irradiation without significant property changes. The fiber′s diameter was between 600 nm and 3 µm, depending on the membrane composition and the electrospinning parameters. CHX was released in vitro over 10 days and the bacterial inhibitory concentration, 80 µg·mL−1, was reached within eight days. The optimal membrane, PGLA/PLC/CHX-CD (60%/40%/4%), exhibited a breaking strain of 50%, allowing its safe handling. This membrane and a membrane without CHX-CD were implanted subcutaneous in a rat model. The cell penetration remained low. The next step will be to increase the porosity of the membrane to improve the dynamic cell penetration and tissue remodeling.

Solid-to-liquid transition of polycarbonate solid electrolytes in Li-metal batteries

In this work, we analyzed the thermal stability of polycarbonate: lithium trifluoromethane sulphonylimide (LiTFSI) systems. Polyethylene carbonate (PEC) and polypropylene carbonate (PPC) undergo depolymerization to ethylene carbonate (EC) and propylene carbonate (PC), respectively, in the presence of Li salt under annealing treatment. The decomposition reaction can explain the surprising high ionic conductivity recently reported for solid polymer electrolyte (SPE) polycarbonate-based systems. Because this phenomenon can strongly impact the results of SPE research, it is essential to control the depolymerization of polymers to avoid inaccurate electrochemical performance. In addition, we observed that the standard drying procedure for the preparation of high-salt-concentration polymer (polymer-in-salt) SPEs traps a high amount of residual solvent, e.g., acetonitrile (ACN), due to the strong bond between the solvent and ionic species. This finding represents another factor influencing the remarkably high ionic conductivity.

Influence of hydrophobic resin coating on micro-tensile bond strength of different adhesives: an in – vitro study

Recently, the etch-and-rinse and self-etching approaches are the two strategies of resin-based adhesive systems to accomplish the bonding to enamel and dentin. The increased amount of solvents and hydrophilic monomers in the adhesive formulations lead to greater amount of residual solvents entrapped in the adhesive layer. Consequently, the resulting polymers will be more susceptible to degradation over time. One of the methods for more durable bond includes the application of an additional layer of a hydrophobic resin coating over the polymerized simplified adhesive. The aim of this in –vitro study was to evaluate the influence of hydrophobic resin coating on micro-tensile bond strength of different adhesives Eighty freshly sound human molars were divided into three main groups according to method of bonding (A), where (A1) represents teeth bonded using Single Bond Universal Adhesive in total each approach, (A2) represents teeth bonded using Single Bond Universal Adhesive in self-etch approach while (A3) represents teeth bonded using Self Etch Future Single Bond DC Bonding System. Each (A) group will be then subdivided into two additional subgroups according to the addition of hydrophobic resin coating into (B1) which stands for teeth with additional hydrophobic resin coating and (B2) which stands for teeth without additional of hydrophobic resin coating. Each (AB) group will be finally subdivided into two smaller subgroups according to the effect of thermocycling, where (T1) denotes the teeth which were thermocycled, and (T2) denotes the teeth which were not thermocycled. The occlusal dentin surface of each molar was prepared on two levels: Superficial level (below the dentino enamel junction by 0.5 mm) and deep level (below the dentino enamel junction by 1.5 mm). For all specimens, after bonding procedures either total etch or self etch, a hydrophobic resin coating was added for the assigned groups. Resin composite was applied; thermo-cycling was done for the assigned groups. Teeth were sectioned into a series of 1 mm thick slabs and microtensile bond strength testing was done. Two representative specimens of each group were selected for Ultramorphological Examination. Mode of application, addition of adhesive layer and thermocycling had a significant effect on bond strength. Within the limits of this study, we concluded that regarding bonding efficacy to enamel and dentine, conventional 3-step etch-and-rinse adhesives are still not surpassed by the newer simplified self etch adhesive systems. Addition of the hydrophobic bonding resin coating improved bonding to dentine especially when used with all-in-one self-etch adhesive systems.

Pilot evaluation of an aqueous/nonaqueous hybrid bitumen extraction process for mineable oil sands

An aqueous/nonaqueous hybrid bitumen extraction (HBE) process for mined oil sand has the potential to reduce thermal energy demand and greenhouse gas emissions while integrating the productivity and robustness of the current commercial process. The process involves the application of a small amount of solvent to pre-soak the mined ore prior to slurry conditioning, followed by the currently used water-based process, albeit at a lower temperature (e.g. 20 °C) and with no need for caustic addition. In this work, the HBE technology is advanced to the testing of a pilot continuous flow system of 100 kg per hour. This communication describes the extraction outcomes of a series of pilot HBE flotation tests conducted at various extraction conditions, and determination of the respective residual solvent contents in the extraction tailings. Results showed that bitumen recoveries and froth qualities from the pilot HBE process depended on the type and dosage of solvent used to soak the ore prior to slurry conditioning, as well as on the slurry conditioning and residence time. Importantly, lower-temperature HBE could produce comparable or higher bitumen recoveries than those achieved using standard Clark hot water extraction; bitumen froth generated from ambient HBE contained lower fines or water contents. The amount of residual solvent in the tailings produced from the pilot hybrid extractions largely correlated to the unrecovered bitumen percentage. For good-processing ores, for which over 90% bitumen recoveries were achieved, the amount of solvent lost to the tailings was below the regulatory limit even without the use of a tailings solvent recovery unit.

Amorphous Fluoropolymer Membrane for Gas Separation Applications.

Amorphous fluoropolymers have been studied in the past few decades and received extensive attention due to their unique and useful properties. One of the remarkable properties of amorphous fluoropolymers is high fractional free volume (FFV), and they tend to retain large amounts of solvent inside their polymer chains. In this study, amorphous flouoropolymer membranes were employed to examine the influences of the residual solvent and drying condition on the thermal properties, gas permeation behavior, and structure change by the polymer chains. Thermal properties of the produced membranes were characterized by differential scanning calorimetry (DSC) and a thermogravimetric analysis (TGA) to verify the effects of residual solvent. The residual solvent content and the glass transition temperature (Tg) of amorphous fluoropolymer membranes prepared with both solvents decrease with increasing drying temperature. The effect of the thermal treatment method on the d-spacing between the polymer chains of the prepared membranes was investigated using X-ray diffraction (XRD). The d-spacing decreased with drying below the Tg whereas it drastically increased near the Tg because of chain relaxation. From these phenomena, the helium permeability of the membranes treated at 120 °C radically increased. However, the oxygen and nitrogen permeability decreased with decreasing residual solvent content. The glass transition range shifted to higher temperature, from 75 °C to 133 °C, depending on the reduced amount of residual solvent.

Do Very Small POSS Nanoparticles Perturb s-PMMA Chain Conformations?

Small-angle neutron scattering (SANS) measurements of syndiotactic s-PMMA polymers mixed with weakly attractive 1.0 nm diameter polyhedral oligomeric silsesquioxane (POSS) nanoparticles (NPs) show no observable changes in the chain radius of gyration Rg, regardless of the polymer molecular weights, the amount of residual solvent, or the POSS NP loading and dispersion (from 0 to 20 vol %). In retrospect, these results are not surprising since scaling arguments imply that chain size in the concentrated region of the phase diagram of a polymer solution is ideal and independent of the polymer volume fraction ϕ, and only as the semidilute region is entered with decreasing concentration does the chain size for a good solvent begin to increase due to polymer excluded volume and then scales with concentration as ϕ–1/8. For typical polymer nanocomposites the NP concentrations are less than 50% v/v, so the polymers are still generally within the concentrated regions of their phase diagrams, where ideal chain confor...