The formation of coupling agent monolayers on the surface of mica

The interaction of very dilute solutions of a cationic vinylbenzyl silane (CVBS), a methacrylate functional silane (γ-MPS), and an isopropyl-tri-(dioctylpyrophosphato) titanate (IDT) with a mica surface has been studied by carbon analysis. For all three coupling agents the dependence of adsorption with time of treatment follows a step-like curve, where each step corresponds to a monolayer coverage on the mica. Under the operating conditions used it was noted that a particular monolayer is always completed before the next is started. The adsorption of γ-MPS was found to be very sensitive to the time allowed for hydrolysis of the silane, while the adsorption of CVBS was relatively independent of the hydrolysis time when it is varied from 0 to 5400 s. The results indicate that γ-MPS and CVBS near the mica surface form a dense structurally regular multilayer phase with the silane molecules oriented normal to the surface. IDT molecules occupy a surface area on mica which is characteristic of their branched nature.     

The interaction of a cationic silane coupling agent with mica

Carbon analysis was used as a method for measuring the quantity of a cationic vinyl benzyl silane (CVBS) adsorbed onto the surface of mica. The results obtained indicate that CVBS can be applied from aqueous solution over a wide pH range with best treatment in neutral and acidic media. The amount adsorbed depends on the concentration of the treating solution in the lower concentration range while in the higher range, the adsorption is less dependent on concentration. The relationship, silane adsorption vs. time of treatment, shows a steplike dependence. It is suggested that each step corresponds to a monolayer coverage. The data indicate that CVBS on mica is a highly ordered and closely packed multilayer phase with the silane molecules oriented normal to the surface. The multilayer adsorption of silane onto silane in this system may be compared in some respects to polymer crystal growth.     

Effect of Particle Size of Mica on the Properties of Poly[Ether Ether Ketone] Composites

A study on high performance PEEK composites prepared by incorporating with three different particle sizes of mica was fabricated by compression molding. The effects of particle size of mica on the mechanical, thermal and morphological properties were studied. The incorporation of mica increased tensile modulus. The percentage crystallinity of PEEK mica composites was studied by using modulated DSC. The storage modulus changed significantly with the variation of the mica particle size and content in the PEEK matrix. Composite containing 20 wt% mica exhibited about a 79% increase in the storage modulus at 50°C and about a 68% increase at 250°C.     

Thermal properties of silane-grafted water-crosslinked polyethylene

Vinyl trimethoxysilane grafting reactions of low-density polyethylene (LDPE) were performed in an extruder, followed by crosslinking with boiled water. The thermal properties of both silane-grafted and silane-grafted water-crosslinked LDPE were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC data showed that the silane grafts on the LDPE molecules were thermal stable in the absence of moisture under 130°C under which the silane-grafted LDPE could be processed or recycled. The silane grafts on the LDPE molecules reduced the melting point of LDPE and gave rise to an endotherm shoulder at about 85°C. TGA data showed that the decomposition temperature of the silane-grafted LDPE was much higher than that of LDPE. It was demonstrated that the cause of the increase in the decomposition temperature was not due to the silane grafts but due to the peroxide-induced crosslinking reactions during the silane grafting reactions performed in an extruder. Silane-grafted water-crosslinked LDPE displayed multiple melting behavior resulting from phase separation during crosslinking of LDPE with water. The phase separation gave rise to two melting points, including one at about 94°C, and the other at about 107°C. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1075–1082, 1998     

Solubility behaviour of polystyrene: thermodynamic studies using gas chromatography

Studies of thermodynamic parameters and solution properties of polystyrene with various solvents have been performed by gas-liquid chromatography (g.l.c.). A range of solvents has been selected for this purpose. Experiments were performed at 162.31°C, 171.84°C, 219.77°C and 229.43°C. From the chromatographic retention data obtained at these temperatures, the solubility behaviour of polystyrene with each of the solvents selected has been observed and the Flory-Huggins interaction parameters, infinite dilution activity coefficients and heats of solution were determined. The glass transition temperature of polystyrene was determined experimentally.     

Bismaleimide‐modified methyl‐di(phenylethynyl)silane blends and composites: Cure characteristics,thermal stability,and mechanical property

Reactive blends of organic‐inorganic hybrid monomer, methyl‐di(phenylethynyl)silane (MDPES) and a modified bismaleimide resin (BMI/DBA) have been prepared. The thermal and oxidative stabilities of MDPES‐BMI/DBA blends were characterized by thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis, dynamic mechanical analysis, and flexural strength retention at 240°C. Scanning electron microscopy was employed to study the surface morphology of MDPES‐BMI/DBA composite after thermal oxidative treatment. With the increase of concentration of BMI/DBA, flexural strength of composites increased from 78 to 331 MPa. The results showed that MDPES‐BMI/DBA blends exhibited excellent thermal and thermal oxidative properties, and the interface between MDPES and glass fiber was improved by the incorporation of BMI/DBA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Strength degradation in γ-aminopropyl triethoxy silane primed α-Al2O3/nylon 6 peel joints in a wet environment

Unprimed sapphire/nylon 6 peel joints (2.13 ± 0.27 Kg/cm) are found to be stronger than sapphire/polyethylene joints (0.06 ± 0.02 Kg/cm). Priming the sapphire with γ-aminopropyl triethoxy silane (γ-APS) improves the strength significantly resulting in adherend failure in the nylon. The rate and extent of degradation is lower with priming. The optimal silane thickness is about 1900 Å, obtained with a 0.3 percent γ-APS solution, for a five day exposure to water at 25°C. Peel joints made with 0.3 percent γ-APS film, both dried at 25°C (standard conditions) and dehydrated at 110°C under vacuum, fail cohesively when exposed at 25°C. Increasing the exposure to 55°C in a second step results in strength degradation only with dehydrated films. Lower joint strengths are obtained with five days exposure as compared to one day exposure. However, if the temperature is raised to 65°C the joints primed with standard dried films now begin to degrade and lose 90 percent of their strength in five days. Further, the nylon 6 peel joints made with a 0.3 percent γ-APS film, dehydrated for three days prior to lamination, show 10 times greater wet strengths than the corresponding PE joints. Failure surface analyses by ESCA and SEM suggest that failure locus due to water degradation is within the γ-APS layer and the failure mode is cohesive. Failure mechanics during testing the wet peel joints may also cause a partial interfacial failure mode. The effects of the silane film thickness, dehydration condition, time, and temperature dependence of the peel strength degradation indicates that the structure of the γ-APS layer plays an important role in the promotion and retention of adhesion with a thermoplastic polymer system capable of limited primary interactions through possible interdiffusion with the silane layer.     

Recovery of indan derivatives from polystyrene waste

The recovery of indan derivatives from polystyrene waste for the purpose of efficient utilization of plastic wastes was studied. An attempt was made to construct the apparatus, in which thermal decomposition of polystyrene and catalytic reaction of its decomposition products over silica–alumina catalyst could be controlled continuously at the same time. The reaction temperature for thermal decomposition of polystyrene in the upper part of a reactor tube was 420°C, while that for catalytic reaction of the thermal decomposition products in the bottom of a reactor tube was 300°C. These results indicated that the composition of thermal decomposition products of polystyrene could be controlled by the use of a flow reactor. The indan derivatives recovered were two 1-methyl-3-phenylindans, one 1-methyl-1-phenylindan, and 1-phenylindan. The yields of these indan derivatives were 20% of the weight of the liquid products recovered. On the basis of the results obtained in the present work, the most suitable reaction conditions to recover indan derivatives from polystyrene waste is discussed.     

Effect of thermal treatment on the electrothermographic and electrical properties of poly(acrylonitrile butadiene styrene)

Studies on the electrothermographic and conductivity behaviour of poly(acrylonitrile butadiene styrene) (ABS) films of different thermal pretreatments were carried out. The resistivity in ABS layers stored at 50°C was found to be low (～ 10¹⁵ Ω · cm). The charge acceptance and its retention also is poor. The reason for that is the adsorption of water molecules. The layers, when thermally treated at 100°C or more for 5 h, show an enhanced resistivity (～ 10¹⁷ Ω · cm at 50°C) and hence an improvement in charge acceptance as well as in charge retention. Environmental and storage conditions as well as thermal treatment during layer preparations have no effect on the temperature dependence of the resistivity beyond 110°C.     

Physical and mechanical properties of heat‐damaged structural concrete containing expanded polystyrene syntherized particles

Materials recycling for sustainable concrete constructions are favoring the replacement of ordinary aggregate with waste materials, in the form of either solid particles or small void‐formers. This is the case of expanded polystyrene syntherized (EPS) concrete containing EPS particles—or beads—whose high‐temperature residual behavior is investigated in this project. Two EPS mixes and one reference mix (f_c = 25–30 MPa) are tested in compression and tension after a thermal cycle at the reference temperature of 20°C, 150°C, 300°C, 500°C, and 700°C. The thermal diffusivity and the mass loss up to 700°C are investigated as well. The normalized mechanical decay of the two EPS concretes turns out to be slightly higher than that of ordinary concrete, but on the whole, the behaviors are rather close, while the thermal diffusivity of EPS concrete is definitely lower, to the advantage of its insulating capability. Damage indexes are also worked out on the basis of the elastic modulus and of the ultrasonic velocity, in order to have information on the possible void‐induced nonlinear effects. The still open problem, however, is whether the game (polystyrene recycling and mass reduction) is worth the candle (more cement and additives). Copyright © 2014 John Wiley & Sons, Ltd.     

Comparative evaluation of thermal stabilities of novel sulphonic acid resins from anhydride modified polystyrene with commercial polystyrene based resins,Indion-225 and Zeo-carb 225

Non-isothermal as well as isothermal stabilities of sulphonic acid resins from polystyrene, electrophilically substituted with phthalic anhydride, pyromellitic dianhydride, trimellitic anhydride and cis-1,2,3,6 tetra-hydrophthalic anhydride have been studied and compared by d.t.a., t.g.a. and isothermal degradation of these resins at 250° ± 10°C for 72 h in air. The modified resins thus obtained exhibit better thermal stability relative to the unmodified sulphonated polystyrene. The d.t.a. and t.g.a. studies of the modified polystyrene based resins have revealed a better thermal stability compared to sulphonated polystyrene as well as commercial polystyrene divinyl benzene resins like Zeo-carb 225 and Indion 225 (available in India). Isothermal degradation of the commercial resins was studied at 250° ± 10°C for 72h in air and the analysis of the degraded product has also been carried out. Finally, attempts have been made to rationalize these observations on the basis of the structural characteristics of all the resins.     

Silane grafting and moisture crosslinking of polypropylene

Peroxide initiated vinylsilane grafting of polypropylene in an intensive mixer, and the subsequent water crosslinking process were studied. Different concentrations of vinyl trimethoxysilane and dicumyl peroxide were used. The materials obtained after mixing in the rheocord were hot pressed at 190°C. The melt viscosity of the obtained sheets, the melting enthalpy and melting temperature (DSC, differential scanning calorimetry), the mechanical properties and the thermal decomposition behavior (TG, thermogravimetric analysis) were studied. No evidence of grafting during the rheocord processing was observed. Nevertheless, for the hot pressed sheets with concentrations higher than 4 phr of vinyl silane an important increase in the melt viscosity was observed. This increase agrees with the change observed in the mechanical properties, which show a maximum for the water crosslinked samples containing 4 phr of vinyl silane. The modulus increases by 39% at 90°C and 33% at 130°C, while the tensile strength rises by ～22% at both temperatures. The silane grafted water crosslinked samples show a more stable thermal behavior than both the silane grafted samples and the unmodified polypropylene.     

Effect of silane coupling agent on the curing,tensile, thermal,and swelling properties of ethylene‐propylene‐diene monomer rubber (EPDM)/mica composites

The influence of silane (bis[3‐triethoxysilylpropyl] tetrasulfide) coupling agent on the properties of ethylene‐propylene‐diene monomer rubber (EPDM)/mica composites was studied. Both EPDM/mica composites with silane and those without silane were compounded by using a two‐roll mill at various filler loadings (i.e., 100/0, 100/10, 100/30, 100/50, 100/70). The tensile and thermal properties as well as the fracture surfaces of the composites were investigated by using an Instron Universal Testing Machine, a thermal gravimetric analyzer, and a field emission scanning electron microscope. The results indicated that the optimum cure time (t₉₀) and scorch time (t_s2) values were shorter, whereas the maximum torque (M_H) value was slightly higher, for EPDM/mica composites with silane compared to those without silane. The tensile properties, modulus at 100% elongation, and modulus at 300% elongation increased for the composites made with silane, and the optimum filler loading for those properties was 50 parts by weight per hundred parts of rubber. In addition, thermal stability and swelling ratio for both composites improved with increased filler loading. However, the composites with silane showed better thermal stability and swelling ratio because of stronger linkage at the rubber‐filler boundary, which promoted filler dispersion. J. VINYL ADDIT. TECHNOL., 20:116–121, 2014. © 2014 Society of Plastics Engineers     

The effect of temperature on the stability of ion-exchange resins in aqueous medium

The effect on ion-exchange resins of the polystyrene type of a thermal treatment has been studied by heating strong cation and strong anion resins in water at 95°C and 250°C and obtaining the IR spectra of the remaining resins as well as those of the decomposition products extracted by the water. The degradation of the resins is highly dependent on their ionic form. The ? (OH^?) and the ? (H⁺) forms are more labile, losing completely their exchange capacity at 250°C, while the ? (Li⁺) form retains considerable ion-exchange capacity. On the other hand, the hydrothermal process affects differently the backbone of the anion and the cation resins. There are similarities in the type of decomposition products found after hydrothermal treatment with those observed after radiolytic exposure of the resins. Heating the resins in water reduces the crosslinking of the polystyrene matrix.     

Mechanical and thermal properties of blends of low‐density polyethylene and ethylene vinyl acetate crosslinked by both dicumyl peroxide and ionizing radiation for wire and cable applications

Formulations of chemically crosslinked and radiation‐crosslinked low‐density polyethylene (LDPE) containing an intumescent flame retardant such as ammonium polyphosphate were prepared. The influence of blending LDPE with a poly(ethylene vinyl acetate) copolymer (EVA) and the effects of various coadditives, including polyethylene grafted with maleic anhydride (PEgMA), vinyl silane with boric acid, and talc, on the mechanical and thermal properties were investigated. Chemical crosslinking by dicumyl peroxide and crosslinking by ionizing radiation from an electron‐beam accelerator were both used and compared. Improved mechanical properties were observed by the partial replacement of LDPE with EVA. Similar mechanical or thermal properties were observed with coadditives such as PEgMA and vinyl silane with boric acid. The addition of a small amount of talc improved the tensile strength of the formulations. All crosslinked formulations showed good thermal stability on the basis of the retention of mechanical properties after thermal aging for 168 h at 135°C and a hot‐set test. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The Use of Thin Film Thermocouples to Determine the Thermal Conductivity and Young's Modulus of Coatings and Interfaces

Linear and differential thin film thermocouples, typically 500-1000Å thick, were fabricated on flexible polymer and paper substrates by thermal evaporation. Both types of thermocouples had thermal sensitivities of approximately 4 μ V/°C, for temperatures between 20°C and 40°C, on the paper and polymer-coated paper substrates. The transverse thermal conductivity (k^t), i.e., thermal conductivity in the direction perpendicular to the plane of the films, of polyimide (Kapton-H®) films, of a clay-coated paper, and of a polystyrene coating on paper were determined by depositing linear thermocouples on both sides of the films and raising the temperature of one junction and measuring the heat flux and, at equilibrium, the temperature of the other junction. Shear and Young's moduli of the polymer films were estimated from the measured thermal conductivity values, assuming the Debye model of thermal conductivity.     

Silane grafting reactions of low-density polyethylene

Reactions of vinyl trimethoxysilane grafting onto low-density polyethylene (LDPE) were investigated using Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermal gravimetric analysis. The silane grafting reactions were induced by a fixed amount of dicumyl peroxide at 0.2 part of reagent per hundred parts with respect to LDPE. Fourier transform infrared data demonstrated that the extent of the silane grafting reaction was increased as the amount of silane used, the reaction time, or the reaction temperature was increased. The apparent activation energy of the silane grafting reaction was 9.7 kJ mol⁻¹. Differential scanning calorimetry was used to follow the silane grafting reactions in situ at a heating rate of 20°C per minute. The silane grafting reaction was exothermic starting at about 150°C and ending at about 230°C, indicating a completion of the reaction in 4 min. The grafting reaction heat has linear relations to the amount of silane used. The grafting reaction heat of about 1 J/g of sample was generated during reaction per part of reagent per hundred parts of silane used. The reaction heat of silane grafting onto LDPE per mol of silane used was 14.5 kJ mol⁻¹ silane, and the reaction heat of peroxide that reacted with LDPE was −12 kJ mol⁻¹ peroxide. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 255–261, 1998     

Degradation of polystyrene in supercritical n-Hexane

Degradation of polystyrene was carried out in supercritical n-hexane under reaction temperature ranging from 330 °C to 390 °C, pressure ranging from 30 bar to 70 bar and reaction duration of 90 min. The conversion of polystyrene increased with rising temperature and pressure. The degradation performance was influenced by the temperature rather than applied pressure. Polystyrene rapidly degraded in 30 min after reaching a prescribed temperature ranging from 350 °C to 390 °C. At a prescribed temperature of 390 °C, the degree of degradation was higher than 90%. The degradation reaction was examined experimentally at a relatively low temperature of 330 °C. The degradation of polystyrene by using supercritical n-hexane has been found to be more effective compared to general pyrolysis (thermal degradation). Among the selectivity of liquid products, that of a single aromatic ring group like styrene at 390 °C increased up to 65% in 90 min. It was found from the analysis by a gel permeation Chromatograph (GPC), that high molecular-weight compounds decreased but oligomers increased with rising temperature.     

Processing and properties of Nextel™ 720 fiber reinforced alumina-zirconia ceramic matrix composites

The continuous Nextel? 720 fiber-reinforced zirconia/alumina ceramic matrix composites (CMCs) were prepared by slurry infiltration process and precursor infiltration pyrolysis (PIP) process. The introduction of submicron zirconia powders into the aqueous slurry was optimized to offer comprehensively good sintering activity, high thermal resistance and good mechanical properties for the CMCs. Meanwhile, the zirconia and alumina preceramic polymers were used to strengthen the porous ceramic matrix through the PIP process. The final CMC sample achieved a high flexural strength of 200 MPa after one infiltration cycle of alumina preceramic polymer and thermal treatment at 1150 °C for 2 h. The flexural strength retention of the improved CMC sample was 104% and 89% respectively after thermal exposure at 1100 °C and 1200 °C for 24 h.     

Effect of coupling agents on the mechanical properties of mica/epoxy and glass fiber/mica/epoxy composites

The effect of coupling agents, two silane and one zirconate, on the mechanical properties of mica/epoxy and glass fiber/mica/epoxy composites has been investigated. The results showed that tensile modulus and flexural strength and modulus values were improved by the surface treatment of the coupling agents. The property retention was also found to be better in the case of coupling agent-treated mica/epoxy samples after boiling in water for 2h. In the case of glass fiber/mica/epoxy composites, the flexural modulus and interlaminar shear strength values improved with increase in mica content, but the effect of coupling agents was not pronounced.