Solvent uptake as a tool for investigating polymer morphology

Attention is drawn to the potential value of measurement of the rate of solvent uptake as a technique for following changes in the morphology of a polymer specimen, and for detecting small morphological differences between specimens. Examples of each use are described. The rate of sorption of carbon tetrachloride by polypropylene film is very sensitive to the slow changes associated with physical ageing in a specimen, and the effect of different cooling rates after heat treatment is easily observed. For a variety of samples of drawn poly(ethylene terephthalate) it appears that the sorption of benzene or 1,2-dichloroethane is dependent upon two distinct types of orientation in the film.     

Near infrared (NIR) studies of PVC film photodegradation

Near infrared (NIR) spectroscopy was used to develop predictive models of color development for PVC film formulations subjected to accelerated weathering. The high correlations between color and NIR spectra result from the common polyene sequences origin of both measurements. The methodology should be applicable to transparent and filled systems. It provides a probe for investigating polyene sequence formation with minimal saturation effect limitations. The NIR technique can provide a complementary approach to mid‐IR and Raman studies of polymer photodegradation. J. VINYL. ADDIT. TECHNOL., 11:39–46, 2005. © 2005 Society of Plastics Engineers     

ATR-FTIR spectroscopy as a tool for studies of polymer-polymer miscibility

Summary Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy is a useful technique for studies on specific interactions between polymers in miscible blends. The application of ATR-FTIR spectroscopy is demonstrated for blends of chlorine containing vinylpolymers of varying chlorine content with different polycarbonates. The miscibility is correlated to specific interactions between polar groups, leading to shifts of the infrared absorption bands.     

Spin coating as a method for polymer molecular weight determination

The spin coating process was investigated using solutions of polystyrene dissolved in toluene. The residual film thickness depends not only on the spinning velocity and concentration, but also on molecular weight. Specific scaling exponents were determined. The molecular weight dependence was investigated in detail to reveal the type of molecular weight average. This enables a fast determination of the molecular weight by use of spin coating. The use of model molecular weight distributions yields a relation to number M_n and weight M_w average molecular weight. Received: 20 August 1996/Revised: 25 November 1996/Accepted: 27 November 1996     

Polyoxometalates/polymer composites for the photodegradation of bisphenol-A

Nowadays water scarcity represents a threat for human and living beings. Therefore, to satisfy the demands of people for clean and safe water, new technologies for wastewater treatment have been developed. Thus, photocatalysis has emerged as a green chemical approach for such treatment. In this context, new polyoxometalate (POM)/polymer composites with relevant photocatalytic properties have been developed via an easy and cheap photopolymerization process upon mild visible light irradiation at 405 nm. This fruitful association between POM and polymer allowed the obtention of shaped materials facile to collect and reuse at the end of the photocatalytic treatment avoiding then the usual time-consuming regeneration methods. The prepared photocomposites displayed excellent photocatalytic performance for the removal of bisphenol-A from water under different sources of irradiation. Hence, 100%, 88%, and 50% of this model compound were decomposed by the phosphomolybdic composite under just 90 min of UV lamp, solar and LED@375 nm irradiations, respectively. The effectiveness of these developed photocatalysts towards the degradation of other organic compounds, as well as the degradation mechanism based on the generation of highly reactive chemicals such as ^•OH radicals promoting the degradation were already reported. Bisphenol-A degradation pathway and the identification of the photoproducts were discussed using mass spectroscopy technique. Therefore, this paper highlighted the photocatalytic efficiency of the new manufactured materials for the photodegradation of the bisphenol-A, thus expanding their application fields, under different sources of irradiation and under pure solar irradiation which make their applications more interesting and less energy consuming.     

Radiation-modified atactic polypropylene as a sensitizer for photodegradation of polyethylene

Atactic polypropylene (APP) was dissolved in CCl₄ and irradiated with ⁶⁰Co gamma rays in various gas atmospheres (air, O₂, N₂, and Cl₂). A small amount of the irradiated APP was blended with polyethylene (PE) as a sensitizer for photodegradation of PE. There was no significant acceleration of decrease in yield strength of PE with UV exposure when oxidized APP or chlorinated APP was used. On the contrary, the use of the APP which was both oxidized and chlorinated caused a considerable acceleration of decrease in both yield strength and elongation. From the fact that the amount of carbonyl groups formed in the matrix PE with UV light exposure was closely related to both the amount of carbonyl groups and the amount of C? Cl bonds existing in the APP before the UV exposure, it was concluded that the combined action of carbonyl groups and C? Cl bonds in the sensitizer is important in the promotion of the photodegradation of the matrix polymer.     

The polymer blend technique as a method for designing fine carbon materials

The polymer blend technique is proposed as a method for designing fine carbon materials. In principle a blend consisting of polymers with and without carbon residue after heating is subjected to melt-spinning, stabilization and finally carbonization. A combination of two polymers and control of the blend texture are important for using the technique successfully. In this paper, three prepared fine carbon materials are introduced, i.e. carbon fibers including thin and long pores aligned parallel to the fiber, thin carbon fibers 200-300 nm in diameter and carbon nanotubes with 10-20-nm outer diameter. In particular the carbon nanotubes are described in detail to emphasize the great potential of the polymer blend technique. Further possibilities of the technique are also discussed briefly.     

Fullerene polymer film as a highly efficient photocatalyst for selective solar fuel production from CO2

C₆₀-based polymeric systems have been constantly anticipated for sustainable solar energy conversion. Reported, herein is a C₆₀ polymer film as visible light active photocatalyst for efficient and selective reduction of CO₂ for the first time. The C₆₀ polymer photocatalyst is synthesized via covalent coupling of C₆₀ monomer units consisting of tetra substituted C₆₀-pyrene conjugates through spacer groups. The synthesized C₆₀ polymer photocatalyst possesses an extended network of well-defined repeating monomer units with good stability and visible light-induced photocatalytic activity. The enhanced visible light harvesting ability of C₆₀ polymer photocatalyst reasonably yields it with higher catalytic ability than its monomer unit. The C₆₀ polymer film photocatalyst upon coupling with the biocatalyst carries out highly selective visible light driven reduction of CO₂ to HCOOH (239.46 μmol). The tandem way of incorporating C₆₀ into visible light active polymeric films for continuous use may be highly rewarding for their extended photocatalytic activity for solar fuel production from CO₂. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48536.     

Viscoelastic simulation of film casting process for a polymer melt

Numerical simulations of the film casting process were performed using a finite element method for Newtonian and viscoelasttc fluids. We simplified the governing equations by the assumption that the stress and velocity gradients in the thickness direction were negligible, and obtained the film thickness and mean value of stress and velocity components in the thickness direction as variables. Viscoelasticity was described by the Larson model with multiple relaxation times. Non‐isothermal conditions were considered by applying the time‐temperature superposition law. The simulation results for the several kinds of commercial low‐density polyethylenes wore compared to the experimental data for a laboratory‐scale process at l90°C and a commercial‐scale process at 310°C. The film width and film thickness distribution at chill roll, and the change of film width were in good agreement for the laboratory‐scale process, but the agreement for the commercial‐scale process was; not as good. In the simulation of the commercial‐scale process at high temperature, the value predicted by the use of the Viscoelasticity for the original pellet showed poor agreement owing to the change of Viscoelasticity in the process. The agreement was improved by the use of the Viscoelasticity for the processed resin, which was changed from the original one. Next, viscoelastic effects on neck‐in and edge bead phenomena were investigated. The neck‐in and edge bead phenomena were considered to be affected by both the uniaxial elongational viscosity and planar elongational viscosity.     

Dilatometer measurement method as a useful tool in fat study

A dilatometer, previously described by Salway, has been employed in the study of fats and their composition. Reproducibility of data in measuring fat volume change with temperature has been demonstrated. Fats and fat mixtures of widely different composition have been studied. The results show that fat differences as reflected in component fatty acid differences can be detected by use of a dilatometer.     

FT–NIR as a determination method for reinforcement of polymer nanocomposites

Layered silicates as nanoscale fillers have a great potential in improving polymer material properties. Depending on the composite structure (agglomerated, intercalated, or exfoliated) a significantly higher level of reinforcement of the virgin polymer can be achieved with a very small amount of filler. The morphology of the composites is usually characterized by XRD and microscopic methods (e.g., transmission electron microscopy). But the level of reinforcement of nanocomposites is not always proportional to morphology (delamination level of the silicate layers). A new approach for characterizing the material reinforcement level as a consequence of melt quality is to correlate the results of extensional rheometry (level of melt strength) with those of near infrared (NIR) spectroscopy. The advantage of the NIR technique is the suitability for in‐line implementation by using quartz based optics and optical fibers for the signal transfer from the measuring probe to the NIR spectrometer. The presented results show a direct correlation between the reinforcement level determined by rheotens measurements and the data analyzed from off‐line NIR measurements. The results of the chemometric analysis of the NIR data shows that this in‐line capable optical method provides quantitative information on the quality of the nanocomposite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of a porous conducting polymer film by electrochemical synthesis–solvent extraction method

Porous conducting polypyrrole (PPy) films have been obtained by electrochemical synthesis–solvent extraction method. The results of scanning electron microscopy (SEM) show that the size and the distribution of pores can be controlled during the electrochemical synthesis. The porous PPy films have sufficiently good mechanical properties, and electrochemical voltammetric studies imply that the porous films also have high electrical conductivity and good electrochemical reversibility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 303–307, 2004     

Multilayer polymer structures containing Ni/Cu nanoclusters as prepared by selective laser sintering

Selective laser sintering (SLS) process was used to prepare nanostructured porous 3D items consisting of Ni or/and Cu nanoclusters embedded into a polycarbonate (PC) matrix for potential use in nanoelectromechanical systems (NEMS). Liquid-phase SLS was performed (in air or Ar) with the Ni-PC powder mixtures taken in proportions of 1 : 1, 1 : 2 (Ni particle size 27–184 nm) and Cu-PC powder mixtures (1 : 9, 1 : 4, 3 : 7, Cu particle size 76–90 nm) using a cw YAG : Nd⁺³ laser (P = 4–10 W) and a scanned spot of slightly defocused beam. After sintering, the size of starting nanoparticles remained unaffected. Demonstrated was the feasibility of SLS production of functionally graded 3D items, which opens up a way to direct synthesis of NEMS devices. Process conditions for preparation of monolayers and 3D items were optimized. Functionally graded 3D items with alternating ferromagnetic Ni-PC and non-magnetic Cu-PC layers exhibited interesting electrophysical and magnetic properties.     

Carbon stable isotope analysis as a tool for tracing temperature during the El Tremedal underground coal gasification at great depth

The new opportunity given by the underground gasifier developed at Alcorisa in Spain (Province of Teruel) in the framework of an European experiment has promoted a better understanding of gasification in a natural reactor. The thermodynamical equilibria of gasification reactions and the repartition of the stable isotopes of carbon (¹³C/¹²C) in the produced gases have been used to monitor the process. An estimation of the temperatures inside the gasifier and at the exhaust has been performed. As shown by the isotopic balances, the tar formation is negligible or null and the pyrolysis zone spreads continuously. The study has confirmed the reality of the ¹³C isotopic abundance measurements for the system CO/CO₂ as an indicator of the temperature inside the gasifier. During the gasifier expansion, the temperature at the exhaust decreases whereas the temperature inside the gasifier is practically constant showing a slight increasing trend. As pointed out by the data, the oxygen enrichment of the gasifying agent plays an important role on the estimated temperatures.     

Effectiveness of ZnO/carbon-based material as a catalyst for photodegradation of acrolein

Acrolein (ACR) is a metabolite of cyclophosphamide (CYP) and induces hemorrhagic cystitis (HC). Here, we investigated the effectiveness of ZnO/carbon fiber (CF) composites as catalysts for removing ACR through photodegradation. Specimens composed of CF and zinc oxide (ZnO) were prepared and annealed at 200–400 °C in air. For the ZnO/CF specimen annealed at 200 °C (CZ200), a continuous and porous ZnO film was formed on the CF surface. Field-emission scanning electron microscopy and physisorption analysis indicated that this composite had a high specific surface area. X-ray diffraction analysis and photoluminescence spectroscopy showed that the ZnO film was amorphous, exhibiting a broad emission spectrum. An ultraviolet (UV) radiation-based degradation system and methylene blue (MB) solution were used to evaluate the feasibility of using the composites as photodegradation catalysts. CZ200 exhibited the highest MB photodegradation rate (95%). The photodegradation of ACR (75 ppm) under 4 W UV light was investigated using an untreated CF sample, an active carbon fiber (ACF) fabric sample, and the CZ200 specimen. CZ200 (45%) exhibited higher ACR degradation rate than CF (8%) and ACF (28%). Hence, we confirmed that ZnO/CF composites can be used to photodegrade ACR and have potential for use in preventing CYP-induced HC in chemotherapy patients.     

Oil-in-oil emulsions: a unique tool for the formation of polymer nanoparticles

Polymer latex particles are nanofunctional materials with widespread applications including electronics, pharmaceuticals, photonics, cosmetics, and coatings. These materials are typically prepared using waterborne heterogeneous systems such as emulsion, miniemulsion, and suspension polymerization. However, all of these processes are limited to water-stable catalysts and monomers mainly polymerizable via radical polymerization. In this Account, we describe a method to overcome this limitation: nonaqueous emulsions can serve as a versatile tool for the synthesis of new types of polymer nanoparticles. To form these emulsions, we first needed to find two nonmiscible nonpolar/polar aprotic organic solvents. We used solvent mixtures of either DMF or acetonitrile in alkanes and carefully designed amphiphilic block and statistical copolymers, such as polyisoprene- b-poly(methyl methacrylate) (PI- b-PMMA), as additives to stabilize these emulsions. Unlike aqueous emulsions, these new emulsion systems allowed the use of water-sensitive monomers and catalysts. Although polyaddition and polycondensation reactions usually lead to a large number of side products and only to oligomers in the aqueous phase, these new conditions resulted in high-molecular-weight, defect-free polymers. Furthermore, conducting nanoparticles were produced by the iron(III)-induced synthesis of poly(ethylenedioxythiophene) (PEDOT) in an emulsion of acetonitrile in cyclohexane. Because metallocenes are sensitive to nitrile and carbonyl groups, the acetonitrile and DMF emulsions were not suitable for carrying out metallocene-catalyzed olefin polymerization. Instead, we developed a second system, which consists of alkanes dispersed in perfluoroalkanes. In this case, we designed a new amphipolar polymeric emulsifier with fluorous and aliphatic side chains to stabilize the emulsions. Such heterogeneous mixtures facilitated the catalytic polymerization of ethylene or propylene to give spherical nanoparticles of high molecular weight polyolefins. These nonaqueous systems also allow for the combination of different polymerization techniques to obtain complex architectures such as core-shell structures. Previously, such structures primarily used vinylic monomers, which greatly limited the number of polymer combinations. We have demonstrated how nonaqueous emulsions allow the use of a broad variety of hydrolyzable monomers and sensitive catalysts to yield polyester, polyurethane, polyamide, conducting polymers, and polyolefin latex particles in one step under ambient reaction conditions. This nonpolar emulsion strategy dramatically increases the chemical palette of polymers that can form nanoparticles via emulsion polymerization.     

Time dependent light attenuation measurements used in studies of the kinetics of polymer crystallization

Results obtained for different samples of s-polypropylene and poly (ethylene-co-octene) demonstrated the usefulness of light attenuation measurements in investigations of polymer crystallization. The earlier stages with separated growing spherulites fall in the range of Rayleigh-Debye-Gans scattering. Known relationships describing the dependence of the linear attenuation coefficient on the radius and the index of refraction of the spherulite can be applied in evaluations. The sensitivity of attenuation measurements is higher than that of conventional tools.