Function Of Blend Composition Research Articles

Structural relaxation around the glass transition temperature in amorphous polymer blends: temperature and composition dependence

The thermally stimulated depolarization current technique has been used to study the relaxation behaviour in solvent-cast blends of poly(vinyl chloride) (PVC) and acrylonitrile-butadiene-styrene (ABS). The effects of the forming conditions (field, temperature and time) on depolarization have been investigated. The data on blends with components in various weight ratios indicate that the blends are not compatible enough to show one relaxation peak and the 40:60 PVC/ABS blend shows the greatest depolarization current. The blends show two relaxation processes corresponding respectively to the glass transitions of PVC and ABS. Partial polarization and peak-cleaning techniques have been used to obtain both α peaks as a function of blend composition. Curve fitting was carried out and the activation energy E a and the pre-exponential factor τ 0 were calculated. The data have been used for investigations of relaxations that obey an Arrhenius-like law. Analysis of the data shows that it is possible to study the relaxation behaviour in this system, which was found to be controlled by the free-volume mechanism described by the Williams-Landel-Ferry equation.

Breakage properties of ore blends

The blending of different ore types is common practice to provide a consistent feed to a process either in terms of uniform assay or rock hardness. When several different deposits of varying grindabilities are blended prior to grinding, the hardness of the ore blend is usually estimated as the average of the component grindabilities. It is often suspected that this is not the real case. Investigations were therefore carried out to determine the variation of the Bond Work Index ( W i ) of an ore blend as a function of blend composition. Bond Work Index measurements were carried out on a sample of 100% pure hard rock ( W i = 14) and 100% soft rock ( W i = 6) and three blends of the two components. The work indices were measured by the Bond method and the Magdalinovic method. Both methods gave comparable results for the pure components but differed markedly for the blends. The work index, as measured by the Bond method, did not give a linear relationship with blend composition but was weighted towards the harder component. This would indicate that it is mainly the harder component which is comprising the circulating load. In the Magdalinovic method, no recycle streams are employed and the resultant work index measurement more closely follows a linear relationship with blend composition. As an aid to the understanding of the grinding mechanisms and interactions taking place in the mill, analysis of the breakage properties (breakage distribution function and breakage rate) of each pure component and the blends were also carried out. Qualitative analysis of the breakage properties suggests there is an interaction between the components of the blend which affects their individual breakage rates. From these results, breakage properties of the harder material appears to have a greater influence on the overall breakage properties and the Bond Work Index of the blend than the softer material. Attempts were made to use the measured breakage parameters and the batch grinding equation to simulate the Bond Work Index test and hence calculate the W i .

Miscibility studies of polymer blends by viscometry methods

AbstractThe intrinsic viscosities of blends of poly(vinyl chloride)/poly(ethylene‐co‐vinyl acetate) (PVC/EVA), poly(vinyl chloride)/poly(styrene‐co‐acrylonitrile) (PVC/SAN), and poly(ethylene‐co‐vinyl acetate)/poly(styrene‐co‐acrylonitrile) (EVA/SAN) have been studied in cyclohexanone as a function of blend composition. In order to predict the compatibility of polymer pairs in solution, the interaction parameter term, Δb, obtained from the modified Krigbaum and Wall theory, and the difference in the intrinsic viscosities of the polymer mixtures and the weight average intrinsic viscosities of the two polymer solutions taken separately are used. © 1994 John Wiley & Sons, Inc.

Dynamics of each component in miscible blends of polyisoprene and polyvinylethylene

The dynamics of the individual components in 1,4-polyisoprene/polyvinylethylene (PIP/PVE) miscible blends are studied using dynamic stress-optical measurements. While the homopolymers are thermorheologically simple and obey the stress-optic rule, the blends show failure of time-temperature superposition and complex stress-optic behavior. The way in which the stress-optic rule fails reveals the relaxation dynamics of each species. The dynamic modulus and complex birefringence coefficient are analyzed to infer the relaxation of each component. The entanglement molecular weight, M e , and monomeric friction coefficient, ζ0, of each species as a function of blend composition and temperature are determined from the contribution of each species to the dynamic modulus. The effect of blending on M e of each component is small; however, its effect on ζ0 of each species is dramatic. Blending strongly speeds the rate of relaxation of the high T g component (PVE), while more modestly slowing the relaxation of the low T g component (PIP). The dynamics of each species have different temperature dependencies in the blend, which leads to the failure of the superposition principle. Furthermore, both the difference between the friction coefficients of the two species and the difference in their temperature dependencies is greater in blends rich in the high T g material (PVE).

Study of the temperature dependence of isothermal spherulitic growth rate data for poly(pivalolactone) in blends with poly(vinylidene fluoride): a link between coherent secondary nucleation theory and mixing thermodynamics

The spherulitic growth rates of α-phase poly(pivalolactone) (PPVL) in blends with poly(vinylidene fluoride) (PVF 2) were measured by polarized optical microscopy as a function of blend composition and isothermal crystallization temperature T x between 160 and 215°C. The PPVL weight fraction in the blends ranges from 100 to 10 wt%, which constitutes the largest compositional range investigated in any such study. Using the Lauritzen-Hoffman kinetic theory of crystallization, the composition dependent equilibrium melting temperatures T m the nucleation constants K g(II) and K g(III) and the surface free energy product σσ e were determined directly from the temperature dependence of the spherulitic growth rate data for each blend. The equilibrium melting temperature, the nucleation constants and the product of the fold and lateral surface free energies of PPVL a-phase crystals are observed to decrease with increasing PVF 2 content. The observed depression in equilibrium melting temperature was successfully analysed following the treatment proposed by Nishi and Wang and based on Scott's expression for chemical potentials in a binary polymer mixture to yield a negative interaction parameter ( ξ=−0.13±0.05). The magnitude of this interaction parameter is consistent with that found in earlier studies of poly(vinylidene fluoride)/poly(methyl methacrylate) blends. Finally, the observed decrease in crystal/melt surface free energy product is discussed in the context of a recent model correlating the lateral crystal/melt interfacial free energy with the characteristic ratio of the crystallizable polymer chain. Our analysis suggests that the lateral crystal/melt interface thickness should increase with PVFZ concentration in the blend in order to minimize the demixing of a crystallizable chain as it diffuses into the melt/crystal interface to become physically adsorbed onto the crystal growth front.

A study of surface enrichment in polystyrene/poly(vinyl methyl ether) blends using attenuated total reflectance infra-red spectroscopy: 1

Surface enrichment of one-phase and phase-separated blends of polystyrene (PS) and poly(vinyl methyl ether) (PVME) by the latter component, which has the lower surface free energy, has been examined using attenuated total reflectance infra-red spectroscopy. The apparent surface concentration of PVME, determined by assuming compositional homogeneity within the depth probed, as a function of blend composition, agrees well with data derived by other methods. Although no effect due to variations in the PS molecular weight was evident, star-shaped PS appears to behave differently from linear PS.

Microstructure and kinetics study of polymeric electrolytes precursor based on poly(ethylene oxide)/polyphosphazene blends

AbstractThis work reports on the microstructural study of the system: poly(ethylene oxide) (PEO) and a poly(fluoroalkoxyphosphazene) (PPz) and comprises both isothermal and non‐isothermal crystallization kinetics as a function of blend composition, as well as the analysis of spherulite growth, nucleating energy and nucleation density.In addition, compatibility studies were conducted based on glass transition temperature on the one hand, and on the other hand on the determination of the Flory‐Huggins interaction parameter via melting point depression.

Studies on the thermodynamic compatibility of blends of poly(vinyl chloride) and nitrile rubber

Inverse gas chromatography has been used to investigate the thermodynamic compatibility of blends of poly(vinyl chloride) (PVC) and nitrile rubber (NBR) as a function of blend composition and acrylonitrile (AN) content of NBR. The values of the polymer-polymer thermodynamic interaction parameters ( X′ 23 and B 23) and the solubility parameter (δ) of the polymers and their blends were determined with the help of the measured retention data for various polar and non-polar probes in the pure and mixed stationary phases of these polymers. Out of all the probes studied only dioxane and cyclohexanone have similar δ values to those of the blends. The B 23 values for the PVC/NBR blends were ∼ −0.1 and −1.1 cal ml -1 depending on the AN content of NBR. Thus, the two polymers are fairly compatible and show increased compatibility with increase in AN content of NBR.

Intermolecular interactions in blends of poly(vinyl alcohol) with poly(acrylic acid)—1. FTIR and DSC studies

The i.r. spectra and the melting behaviour of blends of poly(vinyl alcohol) (PVAI) and poly(acrylic acid) (PAA) have been studied as a function of blend composition. Replacement of H-bonding interactions in pure PAA and PVAI by intermolecular interactions has been proved by analysis of the OH and CO stretching region in the i.r. spectra. The efficiency of these intermolecular interactions results in a rapid decrease of the crystallinity of PVAI when the PAA content increases and its complete supression when the PAA content equals or exceeds 50 wt%. A very high negative value has been obtained for the interaction parameter by measurement of the melting point depression.

Melt‐rheological properties of PP/EVA blend

AbstractThis paper describes a study of melt‐rheological properties of the binary blend of isotactic polypropylene (PP) and ethylene–vinyl acetate copolymer (EVA) at varying blending ratios (from 0 to 40 wt % EVA content) and using three samples of EVA containing different vinyl acetate contents (VA %), viz. 9, 12, and 19%. Measurements made on a capillary rheometer at three different temperatures (210, 220, and 230°C) in a shear stress range of 104–106 Pa (shear rate 101–104 s−1) are presented and discussed for the effects of blend composition and shear stress on the flow curves, melt viscosity and melt elasticity. Morphology of the blend studied through scanning electron microscopy revealed distinct differences in size and number density of dispersed EVA droplets, which are discussed in terms of the variation of average size and number density of the dispersed EVA droplets as a function of blend composition and shear stress. Melt‐rheological properties and morphology of dispersion are correlated and found quite consistent.

Mechanical properties and morphology of high‐density polyethylene/linear low‐density polyethylene blend

AbstractThe binary blend of high‐density polyethylene (HDPE) and linear low‐density polyethylene (LLDPE) in the range of composition from 100% HDPE to 100% LLDPE has been investigated for tensile and flexural properties and the morphology in the deformed state on tensile fracture. Tensile properties (initial modulus, yield stress, and elongation‐at‐yield, ultimate tensile strength and elongation‐at‐break, and work of yield and work of rupture) and flexural properties (flexural modulus and flexural yield stress) are studied as a function of blend composition. Behavior, in terms of these properties, is distinguishable in three zones of blend composition, viz. (i) HDPE‐rich blend, (ii) LLDPE‐rich blend, and (iii) the middle zone. In zones (i) and (ii), the variations of these properties are more or less linear, whereas in the middle region [i.e., zone (iii)], there is a reversal of trends in variation or sometimes a behavior opposite to the expected one. The results are explained on the basis of the effects of cocrystallization and the presence of octene‐containing segments in the amorphous phase. Scanning electron micrographs of the tensile fracture surfaces are presented to illustrate the occurrence of transverse bands interconnecting the fibrils.

Miscibility of poly( para-phenylene vinylene) model compounds with PMMA studied by solid-state NMR

Molecular proximity of trans,trans-1,4-bis(2-(3,4,5-trimethoxyphenyl)ethenyl)benzene (MPV) and poly(methyl methacrylate) (PMMA) in MPV-poor mixtures up to a weight ratio MPV/PMMA = 1 1.5 is shown by 1H combined rotation and multiple pulse spectroscopy (CRAMPS) using 2D exchange experiments. The MPV-rich blends ( MPV/PMMA = 1 1.4, 1/1.2 ) are heterogeneous, but have homogeneous domains, while the blend with a weight ratio MPV/PMMA = 1 0.7 is fully heterogeneous. The comparison of the CP/MAS 13C NMR spectra of pure MPV and of MPV blended with PMMA shows significant changes in chemical shift and line broadening in the case of intimate mixing, whereas heterogeneity causes an increase of resolution. This was confirmed by proton spin-locking relaxation time measurements ( T1 ϱH) on the blends. On intimate mixing, T1 ϱH is averaged out and varies linearly as a function of blend composition.

Crystallization, tensile, and impact behavior of polypropylene/polybutadiene blend

AbstractA blend of isotactic polypropylene (PP) and polybutadiene (PBu), in the composition range 5–35 wt % PBu content, prepared by mixing in a two‐roll mill, is studied for crystallization, tensile, and impact behavior. Variations in crystallization behavior and the resulting morphology and structure are observed in both differential scanning calorimetry (DSC) and X‐ray diffraction measurements on this blend as a function of blend composition. Impact and tensile properties are studied in the entire blend composition range. Analysis of tensile properties data in terms of the various theoretical models is attempted to obtain better insight into the interphase adhesion and stress concentration effect in this blend. The effects of blend composition on the state of dispersion and morphology of dispersed phase droplets and correlation of tensile properties with the crystallization parameters of PP component are also presented.

Small angle neutron scattering studies of interactions and chain dimensions in bimodal polystyrene blends

The nature of mixing in bimodal polystyrene homopolymer blends has been investigated by using small-angle neutron scattering. Blends were made from deuterated high ( M ≈ 110 000) and hydrogenous low ( M ≈ 1000–3000) molecular weight fractions. The interaction parameter χ and the statistical segment length were obtained as a function of blend composition and the molecular weight of the low M component. Blend compositions ranged from 0 to 50% of the high M component in the low M matrix. A significant level of non-ideal mixing was observed for the lowest molecular weight of the low M component, as evidenced by χ values of the order of 0.02 and chain dimensions associated with the high M component that were smaller than those expected for polystyrene in the bulk state. With increasing molecular weight of the low M component, χ decreased toward the value intrinsic to blends of deuterated and hydrogenous polystyrene, and the chain dimensions became essentially ideal. The molecular weight effect and magnitude of χ were consistent with a non-ideal mixing effect associated with the initiator fragment remaining from the polymerization.

Etude ultrasonore de melanges de polyethylene et de polystyrene. Correlation avec la microstructure

Measurements of velocity and damping coefficient of longitudinal and transverse waves were performed on polyethylene/polystyrene blends in the temperature range − 70°C to + 20°C. The complex moduli were calculated and studied as a function of blend composition. Finally, a relation between ultrasonic velocity and absorption is examined.

Solubility of a styrene oligomer in a polystyrene ionomer

A dynamic mechanical analysis of a microphase-separated polystyrene ionomer blended with a styrene oligomer (molar mass = 800) is presented. In particular, the extent of plasticization by the oligomer of the ionomer glass transition ( T g) and of the so-called ionic transition ( T i) as a function of blend composition and three ion contents was examined. It was noted that, with increasing oligomer concentration, the T g (which represents the less polar regions of the ionomer) initially decreases rapidly compared to T i (which represents the more polar microphase-separated regions of the ionomer), and then more slowly at a rate comparable to T i. The T g decrease is less than that predicted by the Fox equation (in contrast to a lower molar mass non-polar diluent); furthermore, it deviates more strongly with oligomer concentration the higher the ion content of the ionomer. At high oligomer concentrations, gross phase separation of the oligomer from the plasticized ionomer occurs. These results are discussed in terms of the solubility of the oligomer in the two ionomer phases.

Blends of polycarbonate and poly(hexamethylene sebacate): IV. Polymer blend intrinsic viscosity behavior and its relationship to solid-state blend compatibility

The intrinsic viscosities of blends of bisphenol-A polycarbonate and poly(hexamethylene sebacate) have been measured in chloroform as a function of blend composition for a variety of molecular weight species. The compatibility of the polymer blend mixtures is characterized by the parameter δb, from the Krigbaum and Wall theory. Using Tg of the blend as a measure of bulk solid-state compatibility, a correlation is obtained with the Krigbaum and Wall parameter δb for each of the molecular weight pairs studied. Slopes of the correlation are invariant, as expected, as the chemical composition is the same for the different molecular weight pairs studied.

Miscible blends from plasticized poly(vinyl chloride) and epoxidized natural rubber

AbstractMiscible blends from plasticized poly(vinyl chloride), and epoxidized natural rubber having 50 mol% epoxidation level were prepared in a Brabender Plasticorder by the melt‐mixing technique. Changes in Brabender torque and temperature, density, dynamic mechanical properties, and differential scanning calorimetry of the samples were examined as a function of blend composition. The plasticized poly(vinyl chloride)/epoxidized natural rubber blends behaved as a compatible system at all composition ranges as evident from their single glass‐rubber transition temperature (Tg) obtained from dynamic mechanical analysis as well as from differential scanning calorimetry. Profound changes in the nature of the glass‐rubber transition were noted with respect to blend composition. The Tg‐width values of blends lie between those of plasticized poly(vinyl chloride) and epoxidized natural rubber.

Miscible blends of poly(aryl ether ketone)s and polyetherimides

AbstractA new class of high performance engineering resins, poly(aryl ether ketone)s, has emerged with a property balance not offered by existing polymeric materials. Blends of poly(aryl ether ketone)s with other polymers have not been described in the open literature, although several patents have revealed interesting and important properties of certain blend combinations. Ultem polyetherimide has been found to be miscible over the entire composition range and as a consequence is a very effective heat distortion temperature builder, particularly if the poly(aryl ether ketone) is allowed to crystallize. Crystallization kinetics and mechanical properties were studied as a function of blend composition and poly(aryl ether ketone) melting point. The blends exhibited a maximum in toughness at intermediate compositions along with an accompanying maximum in poly(aryl ether ketone) crystallinity. The chemical resistance of the polyetherimide is significantly improved with the addition of a poly(aryl ether ketone). In organic chemicals, the improvement was expected when tensile stress was plotted vs. log time to rupture. However, in aqueous bases, the resistance of the blends was much greater than anticipated. This property profile suggests that these blends will be useful as thermoplastic composite matrix resins.

Viscoelastic behaviour of non-compatible polymer blends: Polystyrene-polycarbonate

The linear and non-linear viscoelastic properties of a series of non-compatible polymer blends (polystyrene-bisphenol A polycarbonate) have been studied in the temperature range 180–250°. Glass transition temperature measurements show a small degree of compatibility at low PS contents. Variations of zero-shear viscosities as a function of blend composition have been related to the glass transitions and to the values of the thermodynamic interaction parameter λ 23 reported by Lipatov. An attempt was made to derive the linear viscoelastic properties of the blends as a function of the composition of the dispersed phase, given the viscoelastic behaviour of the pure components, using phenomenological models. Morphology of the dispersed phase has also been studied using scanning electron microscopy.