Solvent Swelling Method Research Articles

Effect of reduced graphene oxide on vulcanization of polydimethylsiloxane composites

AbstractThis research aims to investigate the effect of reduced graphene oxide (rGO) on the kinetics of addition vulcanization in polydimethylsiloxane (PDMS) elastomers. For this purpose, the synthesis of graphene oxide (GO) and silane‐grafted GO followed by chemical reduction of particles was conducted to prepare rGOs with different surface chemistry. Particles were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, x‐ray diffraction, scanning electron microscopy, and energy‐dispersive x‐ray analysis. Composites of PDMS containing these particles were prepared by solution mixing, and vulcanization of composites was investigated using differential scanning calorimetry. Results showed that the rate and degree of vulcanization reaction increase up to a critical concentration of particles and then decrease afterward. This behavior was attributed to the catalytic effect of chemical groups on the surface of rGOs, whereas the reverse behavior above the critical concentration was correlated to the immobilization of trapped rubber in the network of particles. Grafting graphene oxide by a long alkyl‐chain silane covered these chemical groups, suppressed the catalytic effect, improved the dispersion of particles, and shifted the critical concentration lower. The critical concentration was correlated to the electrical percolation threshold of particles and confirmed by the solvent swelling method. It was also shown that rGO can itself act as the catalyst for the vulcanization of PDMS with no need for platinum. As the dynamic‐mechanical‐thermal analysis showed, the PDMS composites containing 0.75 wt% of particles did not vulcanize properly. However, composites containing fewer particles were vulcanized.Highlights Reduced graphene oxide affects additional vulcanization of PDMS. Below a critical loading, rGO accelerates vulcanization by a catalytic effect. Above critical loading, rGO decelerates vulcanization by a networking effect. Surface groups of rGO control catalytic and networking mechanisms. Silane modification of rGO affects interfacial behavior, thus critical loading.

Improving interfacial bonding strength between epoxy and PE-based wood plastic composites by micro-riveting

In this paper, we proposed a micro-riveting method using the wood fibers in the wood plastic composites (WPC) to effectively enhance the interfacial bonding strength between the epoxy coating and polyethylene (PE) -based WPC. The WPC surface with wood fibers partially embedded in the PE matrix was prepared using a simple solvent swelling and polishing method. Epoxidized Cardol having a long and hydrophobic chain was modified on the surface of the exposed wood fibers to improve the water-resistance and chemical reactivity of the wood fiber surface. Fourier transforms infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), contact angle, confocal microscopy, and scanning electron microscope (SEM) have been used to characterize the composition and morphology of the surface structures. A pull-off test has been used to evaluate the interface bonding strength, which increased from 1.88 to 5.27 MPa. This constitutes the highest performance among all the non-plasma surface treatment reports (30 % higher than the highest bonding strength reported in the literature and comparable to plasma-based surface treatments). The epoxy-WPC interface showed excellent water resistance after immersing in sodium chloride (NaCl) solution (3.5 wt%) for 60 days. The proposed micro-riveting method is of high significance for WPC and may contribute to the interface adhesion enhancement of other polymer composites.

Thermally oxidized PAN as photocatalyst support layer for VOCs removal

Photocatalytic filter plays a key role in VOCs removal and ensuring the long-term durability of photocatalytic filter is essential for increasing their lifespan in real-world industrial application. However, how to unlock the stability of organic supporting materials as photocatalytic filter has not been taken into account. In this work, photocatalyst TiO2 nanoparticles were successfully immobilized on a polyacrylonitrile (PAN) nonwoven using a solvent swelling method, followed by a thermal oxidation treatment. The photocatalytic efficiency of prepared PAN nonwovens in VOCs removal was investigated and the effect of surface treatments and thermal oxidation process on fibers photostability and thermal characteristics were explored. The obtained thermal-oxidized TiO2@PAN nonwoven showed photocatalytic efficiencies of 75% and 92% for the degradation of toluene and formaldehyde gases, respectively, under simulated sunlight. Compared with the TiO2@PAN nonwoven, the photo-induced degradation rate of oxidized-TiO2@PAN nonwoven decreased by 43%, and TGA-DTG results demonstrated a superior thermal stability of the oxidized PAN sample. The findings of this research can facilitate the application of novel PAN-based nonwoven filters in photocatalytic removal of VOCs by providing higher efficiency, improved thermal stability and photostability.

Examining the Effect of Trimethylol Propane Crosslinker on Butanetriol Trinitrate Plasticized Polycaprolactone Polymer Networks of Propellant Binder System

AbstractThe knowledge of polymer network characteristics is important to tune the properties of advanced energetic propellants based on nitrate ester plasticized polyol binder system. In this article, plasticized polyurethane networks of polycaprolactone (PCP) and hydroxyl‐terminated polybutadiene (HTPB) with different crosslinker content [0 to 0.20 parts] at various stoichiometric ratios (r‐value) [0.8 to 1.0] were studied. Five numbers of polyurethane networks of 1,2,4‐butanediol trinitrate (BTTN) plasticised PCP were formulated at each r value 0.8, 0.9 and 1.0 using 0, 0.05, 0.10, 0.15 and 0.20 parts of trimethylolpropane (TMP) crosslinker. Similarly, five numbers of dioctyl adipate (DOA) plasticized HTPB based polyurethane networks were formulated at r‐value of 0.8. FT‐IR spectra of these polyurethane networks (PUNs) were recorded for functional group identification. Stress‐strain behavior of PUNs was studied for understanding the effect of TMP content and r value on mechanical properties. Hard segment content of PUNs were calculated and its influence on network characteristics and mechanical properties was evaluated. CLD values (ν) increased with increase of hard segment content of PUN and the values quantified by different approaches followed the trend νe (by solvent swelling method) > νne2(by Initial modulus method)>νne1 (by Mooney Rivlin method).

Reduction in Foreign Body Response and Improved Antimicrobial Efficacy via Silicone-Oil-Infused Nitric-Oxide-Releasing Medical-Grade Cannulas.

Foreign body response and infection are two universal complications that occur with indwelling medical devices. In response, researchers have developed different antimicrobial and antifouling surface strategies to minimize bacterial colonization and fibrous encapsulation. In this study, the nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine (SNAP) and silicone oil were impregnated into silicone rubber cannulas (SR-SNAP-Si) using a solvent swelling method to improve the antimicrobial properties and decrease the foreign body response. The fabricated SR-SNAP-Si cannulas demonstrated a stable, prolonged NO release, exhibited minimal SNAP leaching, and maintained sliding angles < 15° for 21 days. SR-SNAP-Si cannulas displayed enhanced antimicrobial efficacy against Staphylococcus aureus in a 7-day biofilm bioreactor study, reducing the viability of adhered bacteria by 99.2 ± 0.2% compared to unmodified cannulas while remaining noncytotoxic toward human fibroblast cells. Finally, SR-SNAP-Si cannulas were evaluated for the first time in a 14- and 21-day subcutaneous mouse model, showing significantly enhanced biocompatibility compared to control cannulas by reducing the thickness of fibrous encapsulation by 60.9 ± 6.1 and a 60.8 ± 10.5% reduction in cell density around the implant site after 3 weeks. Thus, this work demonstrates that antifouling, NO-releasing surfaces can improve the lifetime and safety of indwelling medical devices.

Effect of crosslinking on the physicochemical properties of polydimethylsiloxane-based levonorgestrel intrauterine systems

Polydimethylsiloxane (PDMS)-based levonorgestrel intrauterine systems (LNG-IUSs) such as Mirena® are long-acting drug-device combination products designed to release LNG for contraceptive purposes up to 6 years. LNG-IUSs consist of a hollow cylindrical drug-PDMS reservoir mounted with a polyethylene frame and covered by an outer PDMS membrane. PDMS is the release-controlling excipient present in both the matrix and the outer membrane. The degree of PDMS crosslinking is a key parameter in LNG-IUS manufacturing, dictating the elasticity and mechanical strength (which are critical parameters in molding and demolding of the cylindrical reservoirs). In addition, elasticity and mechanical strength are also important to prevent deformation during insertion into the uterine cavity. The objectives of this study were to investigate the impact of PDMS crosslinking on the physicochemical properties of LNG-IUSs and to develop appropriate testing methods for characterization of their mechanical strength. Formulations with different degrees of crosslinking were prepared by varying the ratio of the PDMS elastomer base and the crosslinking agent. A novel solvent swelling and extraction method was developed to determine the degree of PDMS crosslinking. The extent of crosslinking was also characterized via FTIR, Raman, 1H NMR, DSC, TGA and dynamic mechanical analysis. As expected, formulations with higher degrees of crosslinking showed lower crystallinity. Interestingly, the less crystalline formulations showed higher Tg values and storage moduli compared to the high crystalline formulations, implying that crosslinking is the predominant parameter governing the physicochemical and mechanical properties in LNG-IUSs. Correlations were established between PDMS crosslinking and the physicochemical properties of LNG-IUSs which will be useful for quality control purposes during formulation screening and development. A better understanding of the physicochemical characteristics of these complex products will facilitate drug product development.

Attenuation of Proteus mirabilis colonization and swarming motility on indwelling urinary catheter by antibiofilm impregnation: An in vitro study

Proteus mirabilis is one of the important etiologic agents of urinary tract infections (UTI), which complicates the long-term urinary catheterization process in clinical settings. Owing to its crystalline biofilm forming ability and flagellar motility, elimination of P. mirabilis from urinary system becomes very difficult. Thus, the present study is focused to prepare antibiofilm-impregnated Silicone Foley Catheter (SFC) to prevent P. mirabilis instigated UTIs. Through solvent swelling method, the antibiofilm compounds such as linalool (LIN) and 2-hydroxy-4-methoxy benzaldehyde (HMB) were successfully infused into SFCs. Surface topography was studied using AFM analysis, which unveiled the unmodified surface roughness of normal and antibiofilm-impregnated SFCs. In addition, UV-spectrometric and FT-IR analyses revealed good impregnation efficacy and prolonged stability of antibiofilm compounds. Further, in vitro biofilm biomass quantification assay exhibited a maximum of 87 % and 84 % crystalline biofilm inhibition in LIN (350 μg/cm3) and HMB (120 μg/cm3) impregnated SFCs, respectively against P. mirabilis in artificial urine medium. Also, the LIN & HMB-impregnated SFCs demonstrated long-term crystalline biofilm inhibitory activity for more than 30 days, which is ascribed to the sustained release of the compounds. Furthermore, the results of swarming motility analysis revealed the efficacy of antibiofilm-impregnated catheters to mitigate the migration of pathogens over them. Thus, antibiofilm-impregnated catheter is proposed to act as a suitable strategy for reducing P. mirabilis infections and associated complications in long-term urinary catheter users.

Sesbania gum based hydrogel as platform for sustained drug delivery: An ‘in vitro’ study of 5-Fu release

The purpose of this study is to fabricate 5-Fluorouracil sustained release matrix based on a novel, nontoxic, eco-friendly modified biopolymer. The sesbania gum based hydrogel has been prepared by microwave assisted method using acrylamide as a monomer and N,N Methylenebisacrylamide as a crosslinker. The crosslink copolymerization has been confirmed by several modern techniques such as FTIR, SEM, XRD, TGA, DSC, elemental analysis etc. The bioactive 5-Fluorouracil has been encapsulated via solvent swelling method and its release rate has been investigated in various pH dissolution medium through USP standard protocol.The synthesized hydrogel with higher degree of crosslinking exhibited slower release rate than that of hydrogel having lower degree of crosslinking. Thus, resulting higher t25 value, the release rate increases with increase in pH of the medium. Release kinetics suggests the non-Fickian release behaviour of the hydrogel.

UV Reduced Graphene Oxide PEDOT:PSS Nanocomposite for Perovskite Solar Cells

In this paper, we have investigated the possibility to realize a nanocomposite buffer layer for perovskite solar cells, based on polyelectrolyte poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) PEDOT:PSS and graphene oxide (GO). To this aim, GO, prepared by a modified Hummers method, was mixed with PEDOT:PSS by solvent swelling method and reduced in situ into the polymer matrix through a green and simple method, by using UV radiation. Thin nanocomposite layers were spin coated on different substrates and characterized by several techniques. GO reduction was first analyzed by XPS analyses, monitoring the decrease of the intensity of the peak of the oxygen groups linked to carbon. The grade of the dispersion of GO into PEDOT:PSS was also analyzed by scanning electron microscopy. Sheet resistance measurements of the films with and without GO before and after UV treatment was performed. The thermal stability of the nanocomposites was then evaluated by thermogravimetric analyses. The nanocomposite layer was finally employed in a perovskite solar cell to evaluate the effect of GO reduction on power conversion efficiency. The interface interaction between the nanocomposite and the perovskite precursors was analyzed by contact angle measurements.

S-Nitroso-N-acetylpenicillamine (SNAP) Impregnated Silicone Foley Catheters: A Potential Biomaterial/Device To Prevent Catheter-Associated Urinary Tract Infections.

Urinary Foley catheters are utilized for management of hospitalized patients and are associated with high rates of urinary tract infections (UTIs). Nitric oxide (NO) potently inhibits microbial biofilm formation, which is the primary cause of catheter associated UTIs (CAUTIs). Herein, commercial silicone Foley catheters are impregnated via a solvent swelling method with S-nitroso-N-acetyl-D-penicillamine (SNAP), a synthetic NO donor that exhibits long-term NO release and stability when incorporated into low water-uptake polymers. The proposed catheters generate NO surface-fluxes >0.7 × 10–10 mol min–1 cm–2 for over one month under physiological conditions, with minimal SNAP leaching. These biomedical devices are demonstrated to significantly decrease formation of biofilm on the surface of the catheter tubings over 3, 7, and 14 day periods by microbial species (Staphylococcus epidermidis and Proteus mirabilis) commonly causing CAUTIs. Toxicity assessment demonstrates that the SNAP-impregnated catheters are fully biocompatible, as extracts of the catheter tubings score 0 on a 3-point grading scale using an accepted mouse fibroblast cell-line toxicity model. Consequently, SNAP-impregnated silicone Foley catheters can likely provide an efficient strategy to greatly reduce the occurrence of nosocomial CAUTIs.

Advanced micromachining of concave microwells for long term on-chip culture of multicellular tumor spheroids.

A novel approach based on advanced micromachining is demonstrated to fabricate concave microwell arrays for the formation of high quality multicellular tumor spheroids. Microfabricated molds were prepared using a state-of-the-art CNC machining center, containing arrays of 3D convex micropillars with size ranging from 150 μm to 600 μm. Microscopic imaging of the micropillars machined on the mold showed smooth, curved microfeatures of a dramatic 3D shape. Agarose microwells could be easily replicated from the metallic molds. EMT-6 tumor cells seeded in the primary macrowell sedimented efficiently to the bottom of the concave microwells and formed multicellular spheroids within 48 h. Dense and homogeneous multicellular spheroids were obtained after 10 days of culture, confirming the suitability of the proposed approach. To facilitate long term spheroid culture and reliable on-chip drug assay, polydimethylsiloxane microwells were also replicated from the metallic molds. A solvent swelling method was adapted and optimized to Pluronic F127 towards physically entrapping the block copolymer molecules within the polydimethylsiloxane network and in turn to improve long term cell-binding resistance. Homogeneous multicellular spheroids were efficiently formed in the concave microwells and on-chip drug assays could be reliably carried out using curcumin as a model anti-cancer drug. Advanced micromachining provides an excellent technological solution to the fabrication of high quality concave microwells.

Characterization of maleic anhydride-grafted ethylene–propylene–diene terpolymer (MAH-g-EPDM) based thermoplastic elastomers by formation of zinc ionomer

Thermoplastic elastomers (TPEs) composed of maleic anhydride-grafted ethylene–propylene–diene terpolymer (MAH-g-EPDM) and ZnO were characterized using IR, TGA, solvent extraction, crosslink density, and physical properties. The degree of the ionomer formation increased with increasing the zinc oxide content, and it was also enhanced by adding stearic acid or zinc stearate. The crosslink densities were measured using a solvent swelling method using toluene, xylene, and 1,2-dichlorobenzene. The crosslink density increased when increasing the zinc oxide content. By adding stearic acid or zinc stearate, heteroionic bonds were formed and the crosslink density notably enhanced. The physical properties were dependent on the crosslink densities.

Synthesis of ultrastable eu‐complex/polystyrene composite luminescent nanoparticles using a solvent swelling method

AbstractNanoparticles composed of Eu‐complex, Eu(TTA)3Phen, and polystyrene (PS) were successfully synthesized through an improved solvent swelling method. The unstable Eu(TTA)3Phen could be protected by the hydrophobic shell of PS nanoparticles. This method is very appropriate to embed unstable luminescent molecules into polymer nanoparticles. The as‐synthesized luminescent PS nanoparticles have been turned out to be water‐dispersible, strong red luminescent, ultrastable in strong acid and alkali, and luminescence lifetime enhanced. A cell imaging assay was further carried out and strong luminescent signal could be obtained, which showed that the as‐synthesized luminescent Eu‐complex/PS nanoparticles are a good candidate to be used as luminescent nanoparticles in tumor cell detection. This solvent swelling method is simple, easy to scale‐up, and has great potential in the preparation of other luminescent nanoparticles. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Preparation and characterization of γ‐irradiated crosslinked silicone rubber/organoattapulgite composites

AbstractSilicone rubber (SR)/organoattapulgite (OAT) composites were prepared with γ‐irradiation crosslinking at a dose range varied from 30 to 300 kGy. Natural fibrillar silicate attapulgite (AT) was modified by silane coupling agent, and the obtained OAT was used as reinforcing fillers in SR. The effect of irradiation doses on the degree of crosslinking of SR/OAT composites was determined by solvent swelling method. It was found that the molecular weight between crosslinks (Mc) reduced with the increase in irradiation doses. Moreover, the addition of OAT to SR matrix promoted an increase in the crosslinking density of the composites because of the presence of the active crosslinking sites of OAT. The mechanical properties of the SR/OAT composites including tensile strength, elongation at break, and Shore A hardness subjected to various irradiation doses were studied. The experimental results showed that the tensile strength, elongation at break, and Shore A hardness were all improved significantly in the presence of OAT, which indicated that OAT was an alternative reinforcing filler of SR. In addition, the effect of various irradiation doses on the mechanical properties of SR and SR/OAT composites was also investigated. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

96/03572 Promotion of nitrogen removal during coal pyrolysis by using iron catalyst impregnated by solvent swelling method

96/03572 Promotion of nitrogen removal during coal pyrolysis by using iron catalyst impregnated by solvent swelling method

Role of iron catalyst impregnated by solvent swelling method in pyrolytic removal of coal nitrogen

Role of iron catalyst impregnated by solvent swelling method in pyrolytic removal of coal nitrogen

Role of Iron Catalyst Impregnated by Solvent Swelling Method in Pyrolytic Removal of Coal Nitrogen

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRole of Iron Catalyst Impregnated by Solvent Swelling Method in Pyrolytic Removal of Coal NitrogenJun-ichiro Hayashi, Katsuki Kusakabe, Shigeharu Morooka, Michael Nielsen, and Edward FurimskyCite this: Energy Fuels 1995, 9, 6, 1028–1034Publication Date (Print):November 1, 1995Publication History Published online1 May 2002Published inissue 1 November 1995https://doi.org/10.1021/ef00054a014RIGHTS & PERMISSIONSArticle Views161Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Method for Estimating the Chemical Crosslink Densities of Cured Natural Rubber and Styrene-Butadiene Rubber

Abstract Chemical crosslink densities of gum and carbon black-filled natural rubber (NR) and styrene-butadiene rubber (SBR) were estimated by using a newly developed rheometer. The rheometer is the Rubber Process Analyzer (RPA 2000) which is designed specifically to measure dynamic properties such as shear storage modulus G′ and shear loss modulus G″ in cured and uncured rubber. It was found that the differences between the G′ values of dicumyl peroxide-cured NR and those of uncured samples yielded estimates of the crosslink densities which were nearly the same as the values inferred by chemical analysis. For TMTD-cured SBR, the same procedure yielded estimates of chemical crosslinks very close to those estimated by a tensile stress-strain method and by NMR. In addition, accelerated sulfur-cured natural rubber was also investigated. The agreement between the crosslink densities of these stocks determined from G′ values and from a solvent-swelling method was very good.

Physical and chemical modification of low-rank coals with alkyl chains and the roles of incorporated groups in pyrolysis

Methyl, ethyl, octyl, naphthylmethyl, or tetralylmethyl groups were introduced to acid-washed Morwell brown coal by O-alkylation (Liotta method). Then the alkylated coals as well as acid-washed raw coal were pyrolyzed at a heating rate of 10 °C/s. The role of alkyl groups as inhibitor of cross-linking reactions and stabilizer of fragment radicals during the pyrolysis was affected by their chain length. The increase in tar yield on the basis of alkyl-free coal mass was most significant with octylated coal. Further, Morwell and Wandoan coals were impregnated with higher paraffinic alcohols, 1-octanol and 1-octadecanol, by a thermally induced solvent swelling method and were pyrolyzed in a free-fall reactor at 700-900 °C

A glow discharge treatment to immobilize poly(ethylene oxide)/poly(propylene oxide) surfactants for wettable and non-fouling biomaterials

A non-fouling (protein resistant) polymer surface was achieved using an argon glow discharge treatment of a polyethylene surface which had been precoated with various poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymer surfactants. The surfactant is first deposited on the polymer surface via a solvent swelling and evaporation method. Then the coated surfactant is immobilized on the substrate surface by an inert gas discharge treatment. ESCA and water contact angle () measurements on treated and solvent washed surfaces show significant increases in both surface O/C ratios and surface water wettability (0 < 30°) compared to LDPE control surfaces, revealing the presence of PEO on the treated surfaces. A great reduction of fibrinogen adsorption on the modified surfaces is also observed for the highest PEO content surfactants. This simple surface modification process may have wide applicability to obtain wettable polymer surfaces in general, and non-fouling biomaterial surfaces in specific.