Studies on mechanical,rheological, thermal and morphological properties of in situ silica-filled butadiene rubber composites

Silica is introduced in butadiene rubber (BR) in situ by solution sol–gel method at low and high content. This results in uniformly dispersed spherically shaped silica in rubber matrix as revealed from Scanning electron microscopy study. Incorporation of in situ silica imparts moderate reinforcement to BR composite. Mechanical property and silica distribution are eventually improved by using a silane coupling agent as a surface modifier. Thermal, rheological, morphological, mechanical and melting behaviours of the composites are evaluated and analysed in a comparative manner.     

Flow properties of aqueous solution of methylcellulose

Flow properties of aqueous solution of methylcellulose, especially nonlinear viscoelasticity, were investigated. The peculiar flow properties of the aqueous solution of methylcellulose were compared with the existing theories of non-Newtonian viscosity of concentrated polymer solutions and the experimental results obtained for the aqueous solution of sodium alginate which behaves as polyelectrolyte in solution. The characteristic time for the formation of entanglement couplings between molecular chains was mainly examined. To investigate the elastic behavior under steady-shear flow, normal stress difference was measured with a coaxial cylinder apparatus, and extinction angles were determined with a flow birefringence apparatus. The values of normal stress difference obtained by the mechanical and the optical methods coincided with each other. For the aqueous solution of methylcellulose as reported for solutions of nonpolar polymers, the relation between normal stress difference and shear stress was represented by a single curve irrespective of temperature and concentration. Non-Hooken behavior was observed for the relation between recoverable shear and shear stress and attributed to the strong intermolecular interactions and the stretching-out effect of structural networks.     

Viscoelastic properties of aqueous solution of methylcellulose

The viscoelastic properties of aqueous solution of methylcellulose were investigated using three types of rheometers, which enabled us to cover more than 8 decades of frequency range. At first, the entanglement density X/q at various temperatures was estimated by comparing G′, and G″ curves and relaxation spectra experimentally obtained with those calculated from Hayashi's theory. At lower temperatures, the concentration dependence of X/q was small as observed for polyelectrolytes, but increased at higher temperatures. The same tendency was observed in the concentration dependence of the entanglement function GeN. It is supposed that water molecules adsorbed on methylcellulose and depressing the entanglement formation dissociate with increasing temperature. The relaxation mechanism was then examined from the concentration dependences of G′, η′, and ηo at various temperatures and frequencies. It is concluded that the structural networks in a solution become closer with increasing temperature, and the corresponding viscoelastic mechanism varies from the intermolecular interaction such as entanglements to the intramolecular motion with increasing frequency.     

Structural interpretation of the interfacial properties of aqueous solutions of methylcellulose and hydroxypropyl methylcellulose

Interfacial properties of aqueous solutions of methyl and hydroxypropyl methyl ethers of cellulose are important in foam and emulsion stability, detergency and many other applications involving surface activity of these cellulose ethers. Interfacial tensions of aqueous solutions of these cellulose ethers are measured using a spinning drop interfacial tensiometer. A general correlation is found between interfacial tension and the degree of substitution of methoxyl and hydroxypropyl groups. From thermodynamic considerations it is proposed that these cellulose ethers, for a constant degree of substitution, should exhibit the lowest interfacial tension values for a polymer having the most uniform distribution of substituent groups along the backbone. Other factors which influence the interfacial tension values are surface gelation of adsorbed polymer, molecular weight, concentration of cellulose ether in water phase, ageing time, temperature, and the type of organic phase.     

Effect of titanate coupling agent on the mechanical,thermal, dielectric,rheological, and morphological properties of filled nylon 6

Fillers are used along with various commodity as well as engineering polymers to improve the properties of polymers. The performance of filled polymers is generally decided on the basis of the interface attraction of filler and polymers. Fillers of widely varying particle size and surface characteristics are responsive to the interfacial interactions with polymers. The present study deals with the effect of a coupling agent, tetra isopropyl titanate (TPT), on the properties of flyash filled nylon 6. It is observed that tensile strength, impact strength, and heat distortion temperature improved with the addition of TPT as compared to without the coupling agent filled nylon 6. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 266–272, 2006     

Composites of high density polyethylene and different grades of calcium carbonate: Mechanical,rheological, thermal,and morphological properties

Calcium carbonate (CaCO₃)/high density polyethylene (HDPE) composites were prepared in a HAAKE twin screw extruder, using the experimental conditions defined by the factorial experimental design presented in a prior study. In this study, the effect of different grades (Ca₁ and Ca₂) and CaCO₃ content (varying from 0 to 15 wt %) on the mechanical, rheological, thermal, and morphological properties was evaluated. The results showed that the addition of the filler provoked a decrease on the impact strength, stress at break, and yield stress properties in relation to the pure HDPE. A consequent increase on the modulus of elasticity, indicating an increase on the rigidity of the composite, was observed. It was also verified a tendency to increase the toughness and the viscosity of the composites as CaCO₃ was added. Scanning electron micrographs showed that as the filler was incorporated to HDPE matrix, CaCO₃ particles tended to agglomerate, especially that grade constituted of particles of smaller size. The thermal analysis showed that the addition of mineral filler caused a decrease on the crystallinity degree. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2559–2564, 2006     

Thermal,stability, morphological,and conductivity characteristics of polypyrrole prepared in aqueous medium

The aqueous polymerization of pyrrole with varying FeCl₃/Py mol ratio produces black insoluble powders. IR characterization reveals the shifting of the N? H stretching band to higher frequency with increasing FeCl₃ amount in the feed composition due to lowering of intermolecular H-bonding. SEM shows a spongy texture of the polymer. TGA indicates the initial decomposition temperatures (180°–237°C) to be somewhat dependent on the FeCl₃/Py feed ratio. DSC suggests the glass-transition temperature to be in the range 160–170°C for the polymers prepared with various feed compositions. The conductivity is also dependent on the FeCl₃/Py feed composition and levels off at a value of ～3 ohm^?1cm^?1. © 1994 John Wiley & Sons, Inc.     

Studies on thermal,mechanical, morphological,and viscoelastic properties of polybenzimidazole fiber reinforced high density polyethylene composites

High density polyethylene (HDPE) and polybenzimidazole fiber (PBI) composites were prepared by melt blending in a twin screw extruder. The thermomechanical properties of PBI fiber reinforced HDPE composite samples (1%, 4%, and 8%) of fiber lengths 3 mm and 6 mm were investigated using differential scanning calorimeter (DSC), universal testing machine, rheometer, and scanning electron microscopy (SEM). The effects of fiber content and fiber lengths on the thermomechanical properties of the HDPE‐PBI composites were studied. The DSC analysis showed a decrease in crystallinity of HDPE‐PBI composites with an increase of fiber loading. SEM images revealed homogeneous distribution of the fibers in the polymer matrix. The thermal behavior of the composites was evaluated from thermogravimetric analysis and the thermal stability was found to increase with the addition of fibers. The evidence of homogeneous distribution was verified by the considerably high values of tensile strength and flexural strength. In the rheology study, the complex viscosities of HDPE‐PBI composites were higher than the HDPE matrix and increased with the increasing of PBI fiber loading. POLYM. COMPOS., 5–13, 2016. © 2014 Society of Plastics Engineers     

Influence of molecular weight on rheological,thermal, and mechanical properties of PEEK

This study focuses on the influence of molecular weight on the rheological, thermal, and mechanical behavior of poly(ether‐ether‐ketone) (PEEK), a semicrystalline high‐performance polymer. The results show that the molecular weight of PEEK has significant influence on its rheological, thermal, and mechanical behavior. It was found that PEEK has the unique characteristic of two shear‐thinning regions. The shear viscosity and the stress relaxation time of PEEK increase significantly as molecular weight increases. In general, the Cox‐Merz rule is valid for all grades of PEEK. As molecular weight increases, the melting temperature of PEEK decreases slightly, but its isothermal and nonisothermal crystallization temperatures drop dramatically. As molecular weight increases, the crystallinity, the crystallization rate, and the magnitude of crystallization activation energy decrease. The crystallization kinetics study indicates that PEEK tends to form spherical crystalline structures, regardless of its molecular weight. As molecular weight increases, the tensile strength at yield, the tensile modulus, and the flexural modulus of PEEK decrease slightly, whereas the tensile strength at break, the tensile strain at break, the modulus of toughness, and the impact strength of PEEK increase significantly. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Effect of the chemical characteristics of mesoporous silica MCM‐41 on morphological,thermal, and rheological properties of composites based on polystyrene

Mesoporous silica nanoparticles (MCM‐41) with an average diameter of ～ 20 nm were synthesized by a sol‐gel method using binary surfactant system. Polystyrene (PS) composites containing mesoporous silica nanoparticles were prepared by in situ polymerization of styrene monomers. Similar in situ polymerized PS composites were prepared based on the modified silica functionalized with methyl and vinyl groups. The effects of silylation on thermal and rheological properties of the PS/silica composites are investigated. Of particular importance is that the in situ polymerization of monomers within the mesoporous silica may trap some polymer chains, if not all, thereby affording a greater physical interaction between polymer and the porous fillers, whereas the chemical modification of silica surface promotes the polymer–filler interaction, which in turn enhances the thermal stability of composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Morphological,thermal, and rheological properties of nylon/acrylonitrile-butadiene-styrene alloys

Melt blends of nylon-6/modified ABS (acrylonitrile-butadiene-styrene terpolymer) have been prepared using a single screw extruder. Electron microscopic observations revealed that the rubber particles are as finely dispersed as in ABS. Both the heat of fusion and the dynamic storage modulus of the blends were linear functions of the blend composition. The melting point of nylon crystallites and glass transition temperatures of poly(acrylonitrile-co-styrene) (AS) and the rubber phase in ABS and the amorphous phase in nylon were almost independent of the composition. Very high Izod impact strength was achieved over a broad compositional range. These facts suggest that the nylon and the modified ABS are not mixed on a molecular level although there must be sufficient interaction between them. The melt viscosities were increased with an increase in the ABS component. In the region of less than 65% ABS, the viscosities bend off to the zero-shear viscosity at low shear rates. Above 65% ABS, the viscosity curves were expressed by a power law fluid. The power law index decreased with an increase in the ABS content. The activation energy of flow vs. composition curve indicated a discontinuous point between 60% and 70% ABS. The phase inversion takes place at about 65% ABS, judging from the rheological point of view.     

PA1212的热性能及流变性能研究

采用DTA/TG方法研究了PA1212的热降解过程,用平板流变仪和XLY-Ⅱ型毛细管流变仪对聚酰胺1212(PA1212)的流变性能进行了研究。结果表明:在氮气中,PA1212最大热降解温度约为431.73℃。PA1212熔体流动行为为假塑性流动,随着温度的升高,非牛顿指数下降,假塑性减弱。比较2种流变仪的测量结果发现:平板流变仪在低剪切速率范围内数据较好,毛细管流变仪则在较高剪切速率范围类比较好,且测定的非牛顿指数偏大。     

Influence of compatibilizer on mechanical,morphological and rheological properties of PP/ABS blends

The objective of this work was to study the compatibilizer effect on polypropylene (PP) and acrylonitrile butadiene styrene (ABS) blends. The blends were coextruded and injection molded in various ratios of ABS with and without compatibilizers. Universal testing machine was employed to analyze the tensile properties of basic PP/ABS binary blends. From the mechanical testing, the impact and tensile properties of PP/ABS blend were optimized at 80/20 weight ratio. Various compatibilizers such as PP-g-MAH, SEBS-g-MAH and ethylene α-olefin copolymer were used and their comparative performance on binary blend was enumerated. Hybrid compatibilization effect was also studied and reported. However, the addition of compatibilizers showed the maximum increase in impact strength attributed to rubber toughening effect of ABS. The effect of compatibilizers on morphological properties was examined using scanning electron microscopy (SEM). SEM micrographs depicted the more efficient dispersion of ABS particles in PP matrix with the addition of compatibilizers. Further, interparticle distance analysis was carried out to evaluate the rubber toughening effect. The ABS droplet size in compatibilized PP/ABS blend was brought to minimum of 3.2 μm from 9.9 μm with the addition of compatibilizers. The melt rheology of PP/ABS blend systems was investigated through parallel plate arrangement in frequency sweep. Linear viscoelastic properties like storage (G′) and loss (G″) modulus and complex viscosity (η*) have been reported with reference to the virgin materials. It is understood that the combination of compatibilizers (hybrid compatibilizer) had a considerable effect on the overall blend properties.     

Dynamic mechanical,rheological, and thermal properties of intercalated polystyrene/organomontmorillonite nanocomposites: Effect of clay modification on the mechanical and morphological behaviors

Polystyrene (PS)/organomontmorillonite nanocomposites were prepared by melt processing with a twin‐screw extruder. Sodium montmorillonite was organically modified with stearyl trimethyl ammonium chloride to evaluate the effect of clay modification on the performance of the nanocomposites. A comparative account of nanocomposites prepared with the commercial clay Cloisite 20A (C20A) is presented. X‐ray diffraction studies indicated that the clay layers were completely dispersed, and a delaminated structure was formed in the case of C20A/PS and organomontmorillonite/PS nanocomposites. The dispersion characteristics of the clays within the matrix polymer were further investigated through transmission electron microscopy analysis. Mechanical tests revealed increases in the tensile, flexural, and impact strengths of 83, 55, and 74%, respectively, for C20A/PS nanocomposites at a 5% clay loading. The viscoelastic response of the nanocomposites, studied with dynamic mechanical analysis, also showed a substantial increase in the storage modulus of the nanocomposites with the incorporation of organically modified nanoclays. Furthermore, the melt‐state rheology of the organically modified nanocomposites displayed three distinct regions—glassy, plateau, and terminal—from the high‐frequency region to the low‐frequency region, with a considerable increase in the storage modulus in the glassy and terminal regions. Differential scanning calorimetry and thermogravimetric analysis were also used to evaluate the effect of the addition of nanoclays on the glass‐transition temperature and thermal stability of the PS matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Viscoelastic properties of dilute aqueous solution of methylcellulose at ultrasonic frequencies

The viscoelastic properties of dilute aqueous solutions of methylcellulose at ultrasonic frequencies were investigated by a torsional method using quartz crystal resonators. The concentration dependences of G′ and G″ – ωη_s increased with increasing temperature at 13 kHz, but at higher frequencies G′ and G″ – ωη_s were simply proportional to the concentration irrespective of temperature. These results may be explained by the difference of corresponding viscoelastic mechanism at measuring frequencies. In order to examine the configuration of methylcellulose in water, which changes remarkably with temperature, the intrinsic values at various temperatures were experimentally obtained by extrapolation to zero concentration, and the frequency dependence of intrinsic dynamic viscosity was examined. The values of components of the complex intrinsic viscosity at various temperatures and their frequency dependences were quantitatively compared with those calculated from the Tschoegl theory. The values of hydrodynamic strength parameter in the Tschoegl theory for an aqueous solution of methylcellulose increased with increasing temperature, and an effect of the internal viscosity due to the aggregation of methylcellulose was observed at higher temperatures. However, on the whole, the viscoelastic behavior was relatively close to Rouse-like behavior.     

Dispersion and rheological properties of concentrated silicon aqueous suspension

This work focuses on the optimization of the rheological properties of silicon suspensions by changing the concentration of a dispersant and the pH value of the dispersing medium. The zeta potential and rheological properties of silicon suspensions as a function of tetramethyl ammonium hydroxide (TMAH) concentration were carried out. The results show that the isoelectric point of the silicon particles was at pH 1.6. A silicon suspension with 46 vol.% particles displayed a minimum viscosity at pH 9.6. The results also show that TMAH is an efficient dispersant by enhancing the absolute value of the zeta potential of silicon particles. The optimum dosage of the dispersant was 0.4 wt.% of silicon particles.     

Preparation and characterization of low density polyethylene‐agar biocomposites: Torque‐rheological,mechanical, thermal and morphological properties

Low density polyethylene (LDPE) and agar were blended by using the former as an internal mixer and varying the amount of agar. Resulting blends were hot pressed and characterized with regard to their torque‐rheological, mechanical, dynamic‐mechanical, thermal, and morphological properties. The torque rheological properties were determined using classical power law model. Tensile properties of LDPE‐agar biocomposites showed that agar improves the tensile modulus (stiffness), but compromise the tensile strength and elongation at break. Viscoelastic behavior of the matrix is clearly influenced by the presence of agar biofiller as shown by the dynamic mechanical analysis (DMA). Thermal behavior of the biocomposites was also investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Morphological observations by scanning electron microscopy (SEM) show the ductile to brittle fracture of LDPE‐agar biocomposites subjected to tensile test. This work is an initial reference to identify potential applications of biocomposites based‐on agar as a biofiller. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Effect of nanoclay on morphological,thermal, and barrier properties of albumin bovine

The bionanocomposite of albumin bovine with nanoclay (albumin/clay) has been successfully prepared by solution technique using CuSO₄/glycine chelate complex as the catalyst with various percentage of nanoclay loading. The uniform dispersion of nanoclay with the albumin bovine matrix was achieved by continuous sonication technique. The micro structural interactions of albumin bovine with nanoclay were evidenced by Fourier transform infrared spectroscopy. The structure of the albumin bovine/clay composites was investigated by X‐ray diffraction and high resolution transmission electron microscopy. The thermal stability of the albumin/clay composites was more than that of the virgin albumin and remarkable increase in thermal property was obtained with increase in clay content. The oxygen barrier property of albumin/clay composites was measured and it was observed that the oxygen permeability was substantially reduced due to increase in nanoclay loading. The biodegradable property of albumin and its composites were measured. It was noticed that the pure albumin was degradable in 5 days whereas the albumin/clay bionanocomposites were stable up to 180 days. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers