Dynamic Mechanical Properties Of Blends Research Articles

Comparative Study on Experimental and Kerner Model Predictions of Viscoelastic Properties of Polyamide 6/ Polyvinyl Alcohol Blends

The Polyamide 6 (PA6) / Polyvinyl alcohol (PVOH) blends of different compositions (80/20, 60/40 and 50/50) were prepared by melt mixing in a Haake Rheomixer. The selected blend systems (80/20 and 60/40) were modified with dicumyl peroxide (DCP) and tertiary butyl cumyl peroxide (TBCP). The dynamic mechanical properties of blends were systematically investigated with special reference to the effect of blend ratio and effect of presence of peroxide over a temperature range -20°C to 110°C. The effect of change in the composition of the polymer blends on tan δ was studied to understand the damping characteristics. The mean field theory developed by Kerner has been used to estimate the dynamic properties and the estimated values are compared with the experimental values. The loss tangent curve of the blend exhibited single transition peak corresponding to the glass transition temperature (Tg) of Polyamide 6. Kerner model was found to satisfactorily predict the viscoelastic properties of the blends with polyamide content in the range 50 to 80 wt% assuming PA6 as matrix and for all compositions except 80/20 assuming PVOH as matrix. The Kerner model predictions for the selected blend systems with peroxides are not satisfactory and the co-continuous morphology of the peroxide treated blends were revealed by SEM observations.

Application of mean-field theory in PP/EVA blends by focusing on dynamic mechanical properties in correlation with miscibility analysis

Multi frequency measurement of dynamic mechanical properties including storage modulus, loss modulus and loss tangent of binary blends of an isotactic polypropylene (PP) and ethylene/vinyl acetate copolymer (EVA) at varying blending ratios was performed. Molecular mechanisms of various transitions were explained. The effect of blend ratio on miscibility of the blends using different approaches was studied. It was found that miscibility of blends increases at around 60 wt. % of EVA loading. Also, molecular origins of this phenomenon were proposed. The Arrhenius relationship was used in order to calculate the apparent activation energy (Ea) for the glass transitions of blend components. The Ea were compared at different compositions. The composition dependency of Ea could be explained based on miscibility of the blend components. Morphological parameters such as particle size and its distribution were obtained from SEM micrographs. The differences observed in morphological parameters and also morphological evidence of increased miscibility near 60 wt.% of EVA loading could be explained. In order to predict the dynamic mechanical properties of blends from those of their pure components, mean-field theories developed by Kerner were applied and theoretical values were calculated by solving of the appropriate equations using iteration method. Comparatively, a good agreement between theoretical and experimental data, especially in the upper and lower temperature zones was obtained. It was found that differences between experimental and theoretical values are significant in transition zone. Finally, the different causes of deviations between theoretical and experimental results were discussed.

Effect of glycerol on thermal and mechanical properties of polyvinyl alcohol/starch blends

AbstractThe paper reports the results of studies on the effect of glycerol content on thermal, mechanical, and dynamic mechanical properties of blends of starch and polyvinyl alcohol (PVA). Degree of crystallinity of the starch/PVA blends (4 g/4 g ratio) remains almost constant up to 3.78 g of glycerol as determined by differential scanning calorimetry (DSC) and x‐ray diffraction studies. At higher loading of glycerol the crystallinity decreases. DTG thermograms revealed occurring of one maximum degradation temperature closer to that of starch in blends containing up to 3.78 g of glycerol. At higher glycerol content there gradually occur two distinct peaks of maximum degradation temperature, one occurring close to that of starch and other occurring close to the PVA peak, indicating phase separation of the blend components. Results of stress–strain studies indicate lowering of tensile properties and energy at break particularly at higher glycerol content (beyond 3.78 g). Dynamic mechanical studies reveal a sharp drop in dynamic modulus at higher glycerol content at all temperatures. The blend with low glycerol content shows transitions of starch, while the blend containing high glycerol content beyond 3.78 g display the transitions due to both starch and PVA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Thermal and dynamic mechanical properties of blends of bitumen with metallocene catalyzed polyolefins

A high penetration grade bitumen has been blended with up to 50 wt% of two different grades of metallocene catalyzed linear low density polyethylene (m-LLDPE) in order to investigate the potential of these and similar copolymers as a substitute for styrene butadiene styrene triblock copolymers in polymer-modified bitumens (PMB). A continuous polymer-rich phase was observed at m-LLDPE contents as low as 5–10 wt%, along with a significant decrease in the effective glass transition temperature of the PMBs with increasing polymer concentration, suggesting benefits for low temperature flexibility. The m-LLDPE-based PMBs also showed relatively low dynamic shear viscosities up to high polymer contents in the range of temperature and shear rate corresponding to typical PMB processing conditions. However, the presence of bitumen in the m-LLDPE-rich phase led to a significant reduction in the melting points of the m-LLDPE, and softening of the PMBs at temperatures as low as 40–50 °C, depending on the composition and the melting point of the pure polymer. PMBs based on the m-LLDPE with the higher melting point remained fully elastic in this temperature range, but at the expense of increased crystallinity and a higher glass transition temperature, which limit improvements in low temperature flexibility. On the other hand, the potentially broad composition and property windows associated with m-LLDPEs suggest considerable scope for the fine tuning of PMB properties by using combinations of different m-LLDPEs and/or other polyolefins as a means to optimize performance.

Dynamic Mechanical Analysis of Electron Beam Irradiated Waste Polyethylene and its Blends with Virgin High Density and Low Density Polyethylene

Dynamic mechanical properties of blends of waste polyethylene and virgin high density as well as low density polyethylene have been investigated before and after exposure to electron beam irradiation. Effect of radiation dose on the loss modulus, storage modulus, and damping factor of the blends has been reported. An increase in relaxation temperatures on exposure to radiation has been observed. Peak broadening has also been observed on exposure to radiation. The storage modulus and loss modulus of the blends increase, while that of tan δ decreases on irradiation.

Dynamic mechanical properties of acrylic rubber blended with phenolic resin

AbstractThe dynamic mechanical properties of blends of phenolic resin (PF) and acrylic rubber (ACM) were investigated. PF had good compatibility with ACM and played an important role in the damping of the ACM/PF blends. With the increase of PF content and molecular weight, the peak of loss factor (tan δ) of blends shifted to a higher temperature and became much wider, indicating the convenience to adjust the value of tan δ peak and the temperature range. Fourier Transform infrared spectroscopy detected that the intermolecular hydrogen bonding between the PF hydroxyl groups and the ACM carbonyl groups had made a great contribution to the improvement of damping. Compared with the organic small molecule used in our previous study, PF gifted the blends with equivalent damping performance and much better stability and a lower cost for the application of damping materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Morphology and Mechanical Properties of Nylon 6/PBT Blends Compatibilized with Styrene/Maleic Anhydride Copolymer

Abstract The mechanical properties and dynamic mechanical properties of blends composed of Nylon 6 and poly (butylenes terephthalate) (PBT), with styrene/maleic anhydride (SMA) as compatibilizer, were studied. The observation on the morphologies of the etched surfaces of the cryogenically fractured specimens via scanning electron microscopy (SEM) demonstrated that in the compatibilized Nylon 6/PBT blends, there exists a finer and more uniform dispersion induced by the in-situ interfacial chemical reactions during the preparation than that in the corresponding uncompatibilized blends. On the other hand, the overall mechanical properties of the compatibilized blends could be remarkably improved compared with those of the uncompatibilized ones. Moreover, increasing the amount of the compatibilizer SMA leads to a more efficient dispersion of the PBT phase in Nylon 6/PBT blends. Furthermore, there exists an optimum level of SMA added to achieve the maximum mechanical properties. As far as the mechanism of this reactive compatibilization is concerned, the enhanced interfacial adhesion is necessary to obtain improved dispersion, stable phase morphology, and better mechanical properties.

Rheological and viscoelastic properties of multiphase acrylic rubber/fluoroelastomer/polyacrylate blends

AbstractDynamic viscoelastic properties and dynamic mechanical properties of blends of acrylate rubber (ACM), fluoroelastomer and polyacrylate plastics have been investigated with a rheometer (ARES RDA III) at a frequency (ω) range of 0.1 to 100 rad.s−1. The analysis of thermorheological properties revealed that the dynamic moduli and dynamic viscosity of blends varied with the composition of the ACM/FKM blend and the level and type of polyfunctional acrylates. The blends showed negative deviation of the dynamic viscosity additive rule. Higher polyfunctional acrylates induced phase separations and showed temperature dependency. It was found that the data of the blends did not follow the Cole‐Cole plot of miscibility and the plot of log G′‐log G″ of the blend showed composition dependency. The dynamic mechanical analysis exhibited lower tan δ values for blends containing higher functional acrylates. Stress relaxation measurements showed longer periods of relaxation for all blends.

Dynamic Mechanical Studies of the Sulfonated Butyl Rubber Ionomers and Their Blends

Dynamic mechanical properties of sulfonated butyl rubber ionomers neutralized with different amine or metallic ion (zinc or barium) and their blends with polypropylene (PP), high-density polyethylene (HDPE), or styrene-butadiene-styrene (SBS) triblock copolymer were studied using viscoelastometry. The results showed that glass transition temperatures of ion pair–containing matrix and ionic domains (T g1 and T g2, respectively) of amine-neutralized ionomers were lower than those of ionomers neutralized with metallic ions, and the temperature range of the rubbery plateau on the storage modulus plot for amine-neutralized ionomers was narrower. The modulus of the rubbery plateau for amine-neutralized ionomers was lower than that of ionomers neutralized with zinc or barium ion. With increasing size of the amine, the temperature range for the rubbery plateau decreased, and the height of the loss peak at higher temperature increased. Dynamic mechanical properties of blends of the zinc ionomer with PP or HDPE showed that, with decreasing ionomer content, the T m of PP or HDPE increased and T g1 decreased, whereas T g2 or the upper loss peak temperature changed only slightly. The T g1 for the blend with SBS also decreased with decreasing ionomer content. The decrease of T g1 is attributed to the enhanced compatibilization of the matrix of the ionomer-containing ion pairs with amorphous regions of PP or HDPE or the continuous phase of SBS due to the formation of thermoplastic interpenetrating polymer networks by ionic domains and crystalline or glassy domains.

Dynamic properties of NR/EVA polymer blends: Model calculations and blend morphology

The dynamic mechanical properties of blends of natural rubber (NR) and the ethylene–vinyl acetate copolymer (EVA), a thermoplastic elastomer, were investigated in terms of the storage modulus and loss tangent for different compositions, using dynamic mechanical thermal analysis (DMTA) covering a wide temperature range. Mean-field theories developed by Kerner were applied to these binary blends of different compositions. Theoretical calculations were compared with the experimental small strain dynamic mechanical properties of the blends and their morphological characterizations. Predictions based on the discrete particle model (which considers one of the components as a matrix and the other dispersed as well-defined spherical inclusions embedded in the matrix) agreed well with the experimental data in the case of 30/70 NR/EVA but not in the case of 70/30 NR/EVA blends. A 50/50 blend, where a cocontinuous morphology was revealed by SEM studies, was found to be approximately modeled by the polyaggregate model (where no matrix phase but a cocontinuous structure of the two is postulated). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 165–174, 1999

Mechanical and dynamic mechanical properties of miscible blends of epoxidized natural rubber and poly(ethylene- co-acrylic acid)

The mechanical and dynamic mechanical properties of blends of poly(ethylene- co-acrylic acid) (PEA) and epoxidized natural rubber (ENR-50) have been studied after reactive blending in various proportions in a Brabender Plasticorder. The miscibility of the blends has been studied by using a computer simulation method and experimentally confirmed by dynamic mechanical analysis. The dynamic properties of the blends exhibit single glass transition temperature ( T g) values, thus conforming to the law of miscibility. A positive deviation from the Fox equation (theoretical T g) is a clear indication of miscibility via chemical interaction. A new β-transition peak in the blends appeared, and this is assumed to be due to the side-chain ester group vibration, confirming a chemical reaction between the in situ generated OH groups of the ENR and free COOH groups of the PEA. This leads to miscibility between the constituents forming the grafted structure, i.e. PEA- g-ENR. The mechanical properties exhibit a synergism above that calculated via the additivity rule. The chemical interactions have been further confirmed by swelling studies in a common solvent.

Miscibility and shear creep resistance of acrylic pressure‐sensitive adhesives: Acrylic copolymer and tackifier resin systems

AbstractThe miscibility between an acrylic copolymer and a tackifier resin was investigated in terms of phase diagrams, glass transition temperatures (Tg's), and dynamic mechanical properties of blends. Shear creep resistance (holding power, tb) of the blends was measured as a function of both temperature and stress (σ0) in order to obtain the master curves. It was found that the shear creep resistance of the pressure‐sensitive adhesives (PSAs) was closely related to the miscibility between the components and viscoelastic properties of the blends. The master curve of the miscible blends shifts toward a longer time scale as the amount of tackifier resin in the blend is increased as a result of the modification of the bulk properties, and their behavior greatly depends on the glass transition temperature (Tg) and storage modulus (G′) of the blends. However, the master curve of immiscible blends where two phases exist in the system does not shift greatly toward a longer time scale, because Tg and the storage modulus of the blend do not change greatly. © 1995 John Wiley & Sons, Inc.

Morphology and dynamic mechanical properties of nylon 66/ poly(ether imide) blends

AbstractThe morphology and dynamic mechanical properties of blends of poly(ether imide) (PEI) and nylon 66 over the full composition range have been invesigated. Torque changes during mixing were also measured. Lowertorque values than those calculated by the log‐additivity rule were ontained, resulting from the slip at the interface due to low interaction between the componeents. The particle size of the dispersed phase and morphology of the blends were examined by scanning electron microscopy. The composition of each phase was calculated. The blends of PEI and nylon 66 showed phase‐seoarated structures with small spherical domains of 0.3 ∼ 0.7 μm. The glass transition temperatures (Tgg) of the blends were shifted inward, compared with those of the homopolymers, which implied that the blends were partially imiscible over a range of compositions. Tg1, corresponding to nylon 66‐rich phase. This indicated that the fraction of PEI mixed into nylon 66‐rich phase increased with decreasing PEI content and that nylon 66 was rerely mixed into the PEI‐rich phase. The effect of composition of the secondary relaxations was examined. Both Tβ, corresponding to the motion of amide groups in nylon 66. and Tγ′, corresponding to that of either groups in PEI, were shifted to higher temperature, probably because of the formation of intermolecular interactions between the components.

Dynamic mechanical properties of epoxy resin/epoxidized rubber blends: Effect of phase separated rubber

AbstractThe dynamic mechanical properties of blends of diglycidyl ether of bisphenol‐A‐based epoxy resin and internally epoxidized polybutadiene rubber have been studied. It is shown that the influence of the composition of the continuous phase and of the dispersed phase can be studied not only from the variations of the glass transition temperature but also from the changes in the apparent enthalpy of activation associated with this transition. As the initial rubber content increases, the composition of the dispersed phase remains practically constant while more rubber is able to dissolve in the continuous phase. Analysis of the rubbery plateau region reveals that the shear modulus of the blends is not much affected by the presence of dissolved rubber in the continuous phase but strongly depends on the volume fraction of dispersed phase. This volume fraction can be obtained from the relative drop in shear modulus after modeling the results with the Kerner equation. The results compares well with independent measurements by scanning electron microscopy. © 1994 John Wiley & Sons, Inc.

Composition of the continuous phase in partially miscible blends of epoxy resin and epoxidized rubber by dynamic mechanical analysis

The dynamic mechanical properties of blends of diglycidyl ether of bisphenol-A based epoxy resin and internally epoxidized polybutadiene rubber have been studied as a function of initial rubber content, stoichiometry and cure cycle of the epoxy resin. It is shown that both the glass transition temperature of the epoxy-rich continuous phase, T g E (r) . and the apparent enthalpy of activation associated with this transition, ΔH a E(r) , are sensitive to the state of the rubber in the sample. Specifically, dynamic mechanical analysis can be used to distinguish between rubber dissolved in the matrix (plasticizer), incorporated into the network (flexibilizer) or phase separated (toughener). Furthermore, it is demonstrated that the Gordon-Taylor equation rather than the more commonly used Fox equation should be used to model the effect of dissolved rubber on T g E (r) and that the Gordon-Taylor equation can also be extended to describe the variations of ΔH a E(r) . Ultimately this equation can be generalized to predict the glass transition temperature of a sample containing both dissolved and phase separated rubber.

Studies on the effect of blend ratio and crosslinking system on thermal, X-ray and dynamic mechanical properties of blends of natural rubber and ethylene-vinyl acetate copolymer

Differential scanning calorimetry (d.s.c.), X-ray, dynamic mechanical and microscopy studies were carried out using a series of blends of natural rubber (NR) and ethylene-vinyl acetate copolymer (EVA) in the crosslinked and uncrosslinked states. The crosslinking system (sulfur, peroxide and mixed) and blend ratio do not influence significantly the melting temperature ( T m) of EVA. The decrease in percentage crystallinity of EVA with NR content is related to the incomplete crystallization, as indicated by the lower heat of fusion ( ΔH). The glass transition temperature ( T g) of NR in the uncrosslinked blend did not change substantially and this indicated incompatibility. However, in the case of crosslinked systems, depending on the type of crosslinking agents used, the T g of the NR phase in the blend was shifted to higher temperatures. This has been explained with reference to the predominant crosslinking of the NR phase. From X-ray diffraction patterns, the interplanar distances ( d values) were calculated. With the addition of NR there was a tendency for the d values to increase in all systems. The crystallinity was measured by X-ray and the results were in line with those of d.s.c. measurements. The dynamic mechanical properties such as tan δ, storage modulus and loss modulus of the blends were evaluated. The existence of separate T g values in dynamic mechanical thermal analyser studies indicates that the blends are incompatible. The morphology of the uncrosslinked blends has been studied by scanning electron microscopy.

Morphologies and properties of polyblends: 1. Blends of poly(methylmethacrylate) and a chlorine-containing polycarbonate

The morphologies and dynamic mechanical properties of blends of poly(methylmethacrylate) and a chlorine-containing polycarbonate, cast from dichloromethane solutions, have been studied. The results are discussed in terms of a phase diagram which has been determined for the system. It is demonstrated that the blends do not have equilibrium morphologies, which are virtually impossible to attain: nevertheless, their properties and morphologies can be related to the phase diagram and sample histories. Apparently anomolous variations in miscibility with composition are shown to be a consequence of an assymetric phase diagram and preferential solubility of polycarbonate in poly(methylmethacrylate).

Dynamic melt properties of polymer blends

AbstractThe dynamic mechanical properties of blends of polymer melts were measured using the orthogonal rheometer. Two‐phase blends, polyethylene‐polystyrene, polyethylene‐poly‐(methylmethacrylate), and polystyrene‐polymethylmethacrylate, were studied. The in‐phase and out‐of‐phase moduli were measured over the range of composition and at frequencies between 10−4 and 10 revolutions/sec.The out‐of‐phase modulus increases in a monotonic manner with composition. The in‐phase modulus, however, shows a maximum with composition in two cases. Examination of the relaxation spectra of these blends shows that when no maximum occurs it can be written as an additive function of the spectra of the components. In the case where a maximum is observed in the modulus the measured spectrum of the blend is shifted in frequency relative to the calculated one. This is tentatively attributed to slight interpretation and solubility of one phase in the other in these cases.