Polyarylsulfones,synthesis and properties,

A new class of high molecular weight polyarylsulfones is described. Polymer synthesis and structure–property relationships are discussed. The polymers are prepared by Friedel-Crafts type polycondensation of aromatic sulfonyl chlorides with aromatic hydrocarbons. A number of Lewis acids in small quantities are useful as catalysts for the polymerization. The polymerization reaction is carried out at elevated temperatures in the melt or in solution. Inert, nonbasic solvents which are compatible with the Lewis acid catalysts such as nitrobenzene and dimethyl sulfone are useful for conducting the polymerization. Many of the polyarylsulfones are amorphous, rigid thermoplastics with unusually high softening points, having glass transition temperatures in the range of 200–350°C. Outstanding resistance to air oxidation at high temperatures is derived from incorporation of the deactivating sulfone groups in the aromatic polymer backbone. Melt stability and solubility in selected solvents are emphasized as basis for processibility by conventional solution casting and molding techniques. The combination of properties, which in addition to thermal stability includes a high level of mechanical and electrical properties, chemical inertness, and hydrolysis resistance makes these new arylsulfone polymers useful over a wide temperature range and in severe and corrosive environments.     

Structural adhesives with increased deformation resistance

The radiation-resistant cold-setting adhesive compositions with increased elasticity have been developed based on epoxy-diane resin modified by low-molecular two- and three-functional diluents. The presented adhesives can operate in the temperature range of −196 to +150°C, and they yield a high shear strength of the adhesive joint for aluminum alloys (16–23 MPa) and peeling strength for the joint between organic fabrics and aluminum alloys (1.75–2.4 kN/m).     

Glues based on carborane-containing siloxanes

The results of studying the effect of carborane groups on the properties of elementorganic adhesive systems are given. The modification of organosilicon compositions using bis(hydroxymethyl)carborane is shown to cause an increase in the strength characteristics of its adhesive composites and their resistance to 400°C.     

Heat-conducting adhesives based on modified epoxy resins

Main characteristics of heat-conducting adhesive materials used to withdraw heat from warming elements of devices and the joints of electrotechnical equipment are presented. The developed materials, i.e., TsMK-TP adhesive pastes and TPK convenient for application adhesives, are cold-curing compositions based on epoxy-diane resins modified with Laproxide products. They have heat conductivity coefficients of no less than 1.8 W/(m K), are workable in the temperature range of −196 to 150°C (up to 200°C for a short period of time), and do not contaminate optical elements due to minimal gas release under exposure to vacuum and increased temperatures.     

Investigation of Rheological Properties of Poly(Vinyl Butyral) Solutions in Methacrylic Monomers

Rheological feature of casting polymerizable compositions based on the solutions of poly(vinyl butyral), di(1-methacryloxy-3-chloropropoxy-2-)methylphosphonate, and 2-hydroxypropyl methacrylate at various ratios, which manifests itself in a two-element mechanical model involving viscous strain and plastic yielding, has been determined. The viscosity values of the solutions have been determined from the dependences of shear stress on the shear rate in the temperature range of 30–80°C. It has been determined that the solutions with the specified ratio of FOM-II-to-HPMA and the content of high-molecular component represented by poly(vinyl butyral) from 1 to 5 wt % are most processible at 30°C.     

Benzoxazine siloxanes as modifiers of epoxy resins for coatings

Coatings based on epoxy resin ED-20 modified with organosilicon 1,3-benzoxazines at a concentration of 1–10 wt % have been prepared and studied. According to the DSC data, the curing temperature of the modified compositions falls in the range of 130–150°C. It has been shown that the use of benzoxazine siloxanes as modifying additives significantly improves the adhesion and anticorrosive properties of epoxy coatings.     

Miscibility of poly(styrene‐co‐butyl acrylate) with poly(ethyl methacrylate): Existence of both UCST and LCST

A miscible homopolymer–copolymer pair viz., poly(ethyl methacrylate) (PEMA)–poly(styrene‐co‐butyl acrylate) (SBA) is reported. The miscibility has been studied using differential scanning calorimetry. While 1 : 1 (w/w) blends with SBA containing 23 and 34 wt % styrene (ST) become miscible only above 225 and 185 °C respectively indicating existence of UCST, those with SBA containing 63 wt % ST is miscible at the lowest mixing temperature (i.e., T_g's) but become immiscible when heated at ca 250 °C indicating the existence of LCST. Miscibility for blends with SBA of still higher ST content could not be determined by this method because of the closeness of the T_g's of the components. The miscibility window at 230 °C refers to the two copolymer compositions of which one with the lower ST content is near the UCST, while the other with the higher ST content is near the LCST. Using these compositions and the mean field theory binary interaction parameters between the monomer residues have been calculated. The values are χ_ST‐BA = 0.087 and χ_EMA‐BA = 0.013 at 230 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 369–375, 2000     

Compatibility studies of blends of polycarbonate and poly(ethylene terephthalate)

Blends of bisphenol-A polyarbonate (PC) and poly(ethylene terephthalate) (PET) has been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were prepared by screw extrusion and solution casting with weight fractions of PC in the blends varying from 0.90 to 0.10. From the measured glass transition temperature (T_g) and apparent weight fractions of PC and PET dissolved in each phase, it appears that PET dissolves more in the PC-rich phase than does the PC in the PET-rich phase. The composition-dependent values of the Flory–Huggins polymer–polymer–interaction parameter were determined and found to be from 0.054 to 0.037 for extruded blends at 275°C and from 0.058 to 0.040 for solution casting at 25°C. The interaction parameter decreases with increasing PET concentration. This result is consistent with the values of the T_gs, the microscopy study, and the measured extrudate swell ratios which show that compatibility increases more in the PET-rich compositions than in the PC-rich compositions. The PC–PET blends are not microscopically miscible for all the blend compositions.     

Polydimethylsiloxane–cristobalite composite adhesive system for aerospace applications

The effect of phase‐pure cristobalite (a high temperature crystalline polymorph of silica) on the adhesive characteristics of hydroxyl terminated polydimethylsiloxane (PDMS) was studied. The potential advantages of PDMS/cristobalite composite system as an adhesive for aerospace applications are also discussed. A PDMS/cristobalite composite adhesive system containing different filler contents (0–46 volume percentage, vol%) was prepared. The filler material, phase‐pure cristobalite, was synthesized by the pyrolysis of fused silica at 1400°C. The mechanical, rheological, and thermal characteristics of the composites were studied. A high yield stress (0.151 Pa), shear‐thinning index (1.051), and fast recovery rate were observed for ～34 vol% cristobalite loading, which indicate that PDMS retains its excellent adhesive and flow characteristics even at high filler loading with enhanced mechanical characteristics. Thermal analysis shows the onset of degradation of PDMS shifts to higher temperatures, 372–438°C and 317–417°C in nitrogen and air atmosphere respectively, which shows excellent thermal stability. The residual component yields after thermal degradation of PDMS/cristobalite composite system in nitrogen and air atmosphere show different degradation mechanisms. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of Cold Plasma Treatment on the Performance of Polyurethane Laminated Glass

The delamination of polyurethane (PU) laminated glass usually occurs at the interface between PU and inorganic glass. To prevent interlaminar delamination of PU and inorganic glass, PU was treated with cold plasma. The transparency of PU improved after cold plasma treatment. The cold plasma-treated PU showed 2 to 6 % higher transmittance than untreated PU. The adhesive strength of PU laminated glass increased by at least 96 % after cold plasma treatment. The adhesive strength of untreated PU samples rapidly decreased with increased hygrothermal aging time, whereas treated PU maintained almost 93 % of the original adhesive value even after hygrothermal aging for 30 days. FTIR analysis shows that –CO–O–C–, –C=O, and –CO–N groups appeared on the surface of cold plasma-treated PU, which resulted in the formation of hydrogen bonds at the interface between PU and silicate glass. After cold plasma treatment, the contact angle of PU changed from 105° to 79°, and the surface roughness of PU membranes changed from an average value of 19.74 to 57.16 nm.     

Novel epoxy compositions for vibration damping applications

Three epoxy compositions have been developed by using polyether amine hardeners having varying chain lengths of polyethers. Unlike normal epoxies, the compositions show low glass transition temperatures (0–45°C). Dynamic mechanical analysis and time–temperature superposition of the isotherms indicate that they have broad and high loss factor values over broad frequency and temperature ranges suggesting their application as viscoelastic materials in constrained layer damping of structural vibrations. Copyright © 2004 John Wiley & Sons, Ltd.     

Phase transformations in the systems Ti<Subscript>2</Subscript>Fe–H<Subscript>2</Subscript> and Ti<Subscript>2</Subscript>Fe–NH<Subscript>3</Subscript>

The interactions of two-phase alloy Ti₂Fe with hydrogen and ammonia at 100–500°C were studied, the compositions of the products were found, and the conditions for producing hydride and nitride phases were determined. The potential of using the two-phase alloy in a metal hydride hydrogen accumulator operating at 20–600°C was considered.     

Phase equilibria and critical phenomena in the cesium nitrate–water–pyridine ternary system

The solubilities of components, phase equilibria, and critical phenomena in the cesium nitrate–water–pyridine ternary system are studied in the 5–100°C temperature range by the visual–polythermal method. Cesium nitrate is found to exhibit a salting-out effect at temperatures above 79.9°C causing phase separation in homogeneous water–pyridine solutions. The temperature of formation of the critical monotectic tie line (79.9°C) and the compositions of solutions corresponding to the liquid–liquid critical points at three temperatures are determined. The pyridine distribution coefficients between the aqueous and organic phases of the monotectic state at 85.0, 90.0, and 100.0°C are calculated. Their values demonstrate that salting-out of pyridine from aqueous solutions by cesium nitrate increases at higher temperatures. The plotted isotherms of phase diagrams confirm the fragment of the scheme of topological transformation of the phase diagrams of salt–binary solvent ternary systems with salting-in and salting-out phenomena.     

Determination of the Cumulative Toxicity of Sealing Compositions Based on Polydimethylsiloxane and Hollow Inorganic Microspheres According to the Change of Bioluminescence Intensity

The cumulative toxicity of sealing compositions based on polydimethylsiloxane and hollow spherical glass and ceramic microspheres has been studied using bioluminescent method on a Biotoks-10M instrument. It has been shown that these compositions are nontoxic at room temperature. At 275°C, thermal destruction starts in the sealant and it becomes moderately toxic.     

High temperature solid state transformations in Jammu bauxite

Thermal reactions of Jammu bauxite heated to different temperatures from 950°–1900°C were studied by X-ray powder diffraction method. The formation of mullite by the aluminasilica reaction at temperature 1200°–1400°C and then the transformation of mullite to a glassy phase around 1900°C has also been discussed in detail.     

The applicability of adhesives in Arctic conditions

Analysis of properties of cold-setting epoxy adhesives and various types of film adhesives is carried out with reference to their applicability in Arctic conditions. Data on waterproofness, water absorption, and hygroscopic properties of the set adhesive films are determined. The application of adhesive joints at–60°C is considered.     

Die Konzentration an freiem molekularem Jod in wäßrigen PVP-jodhaltigen Systemen und ihre Änderung mit der Temperatur

The concentration of free iodine and its variation in the temperature range 10–40°C has been determined by the potentiometric method in nine commercial PVP-iodine products as well as in pure aqueous solutions (1, 5 and 10%) of PVP-iodine of the type 17/12 and 90/04. In addition, aqueous solutions of PVP-iodine 30/06 of the same concentrations have been measured in the temperatur range 0–70°C. The commercial products showed a remarkably great spread in the concentration of free iodine (0.2–10 ppm at 25°C), which may be attributed to the different compositions, especially the ratio of total iodine to iodide as well as the kind and quantity of organic-pharmaceutical constituents. All tested PVP-iodine systems showed a significant—and unexpectedly similar—change of the concentration of free iodine by the temperature. The results concerning its relative alteration fit to an exponential function of the form $$\Delta \% [I_2 ]_{\Delta t} = 100[10^{(0.23 \pm 0.0026)\Delta t} 1]$$ which is valid from 10 to 40°C. Following this equation [I₂] increases about 5.4 resp. 100% if the temperature raises about 1.0 resp. 13.1°C. This increase of [I₂] must be considered in the application of PVP-iodine preparations as disinfectants or antiseptics at living tissues. Because of their higher temperature (c. 30–36°C) the applicated PVP-iodine preparations exhibit a significant higher [I₂] than at room temperature (Δt=10–16°C: Δ% [I₂]=70–130%). Therefore also a significant higher degerming efficiency can be expected compared toin vitro experiments, which are conducted in general at room temperature.     

Ambient temperature thermotropic liquid crystalline viologen bis(triflimide) salts

Two dicationic salts with bis(triflimide) as counterions exhibited crystal-to-smectic liquid crystalline phase transitions (T _m=41 and 37°C) and smectic-to-isotropic liquid phase transitions (T _i=112, 136°C). They had a broad liquid crystalline phase range (71–99°C) and an excellent range of thermal stability (360–364°C). Their mixtures of various compositions also displayed liquid crystalline properties from r.t. to an extended range of temperatures. They exhibited fluorescence in 1, 2-dimethoxyethane and methanol.     

Comparison of sodium zirconium phosphate and calcium zirconium phosphate structures for the retention of fluoride

Fluoride anion interaction has been explored for the first time to investigate how the structure of sodium zirconium phosphate (NZP) and calcium zirconium phosphate (CZP) can be altered in its presence. Different compositions were made by adding NaF and CaF₂ in CZP and NZP matrices respectively. Fluoride interaction differs with NZP and CZP structure as suggested by F-NMR data. The addition of fluoride to the NZP or CZP structure enables to stabilize the structure at a low temperature of 600–700 °C under microwave conditions.     

Compatibility of poly(ethylene oxide)–poly(vinyl acetate) blends

The compatibility of poly(ethylene oxide)–poly(vinyl acetate) (PEO-PVA) blends was examined at five compositions covering the complete range. Samples were prepared by coprecipitation and solution casting. Dynamic mechanical properties were studied at 110 Hz between ?120 and 65°C for dry, quenched, and annealed samples. The study also included tensile testing at 25°C, examination of blend morphology, and DSC measurements at elevated temperatures. Optical microscopy revealed that crystallization of PEO proceeds essentially unhindered at up to 25% poly(vinyl acetate) content by weight. Higher levels of this component drastically reduce spherulite size, and at the highest PVA compositions there was no evidence of crystallization. Thermomechanical spectra of quenched and annealed samples indicate limited mixing of the two components except for the higher (>75%) PVA compositions. Tensile properties show a mutual reinforcement at 10-25% PVA content due to possible polymer segment association. The melting-point depression of PEO is significant above 25% PVA and has been attributed to morphological changes of the PEO crystalline phase.