Damping Properties of Ethylene-Vinyl Acetate Rubber/Nitrile Butadiene Rubber Blends

The damping and mechanical properties of ethylene-vinyl acetate rubber (EVM)/nitrile butadiene rubber (NBR) blends, with BIPB (bis (tert-butyl peroxy isopropyl) benzene) as curing agent, were investigated by DMA. It was proved by mechanical performance, DMA and crosslink density data that a chemical crosslinking reaction occurred between EVM and NBR. A new tan δ peak appeared between 40°C and 60°C in EVM/NBR = 80/20, which we suggest was due to a new molecular chain generated between EVM and NBR. Thus, the effective damping temperature range (EDTR) of EVM/NBR = 80/20 was widened from 31.6°C of EVM and 31.7°C of NBR to 40.7°C. The addition of sulfur, as a curing agent for NBR, greatly raised the height of the damping peak of EVM/NBR blend, but only slightly widened the EDTR at a cost of deterioration of mechanical performance. Zinc diacrylate (Zn (Ac)₂), as a possible graft addition to the blends, enlarged the damping peak of EVM/NBR, especially widening the EDTR of EVM/NBR = 80/20 to 50.9°C, but with a decline of mechanical properties. PVC was partially miscible with EVM/NBR blends and dramatically widened the EVM/NBR = 80/20 EDTR to 62.4°C.     

Morphology,miscibility and mechanical properties of PMMA/PC blends

This study deals with some results on morphology, miscibility and mechanical properties for polymethyl methacrylate/polycarbonate (PMMA/PC) polymer blends prepared by solution casting method at different concentration between 0 and 100 wt%. Dynamic storage modulus and tan δ were measured in a temperature range from 30 to 180°C using dynamical mechanical analyzer (DMA). The value of the storage modulus was found to increase with the addition of the PC in the matrix. Transition temperature of pure PMMA and pure PC is found to be 83.8 and 150°C, respectively. The result shows that the two polymers are miscible for whole concentration of PC in PMMA. The distribution of the phases in the blends was studied through scanning electron microscopy (SEM). Also the mechanical properties like elongation at break and fracture energy of the PMMA/PC blends increase with the increase in concentration of PC in PMMA.     

Temperature and frequency dependent electrical properties of 50 MeV Li3+ ion irradiated polymeric blends

The polymeric blends of polyvinyl chloride (PVC) and polyethylene terephthalate (PET) with equal composition by weight have been irradiated with 50 MeV Li³⁺ ions at different fluences. The AC electrical properties of polymeric blends were measured in the frequency range 0.05–100 kHz, and at temperature range 40–150 ^°C using LCR meter. There is an exponential increase in conductivity with log of frequency and effect is significant at higher fluences. The value of tan δ and dielectric constant are observed to change appreciably due to irradiation. The loss factor (tan δ) versus frequency plot suggests that the capacitors of polymeric blend of PVC and PET may be useful below 10 kHz. No change in dielectric constant was observed over a wide temperature range up to 150 ^°C. Thermal stability was studied by thermogravimetric analysis. Thermal analysis revealed that chain scission is the dominant phenomena in the polymeric blends resulting in the reduction of its thermal stability. It appears from differential scanning calorimetry studies that the melting temperature decreases as fluence increases. FTIR spectra measurements also revealed that the material suffered severe degradation through bond breaking beyond the fluence of 2.3×10¹³ ions/cm².     

Nonisothermal Crystallization Kinetics of Miscible Blends of Polycaprolactone and Crosslinked Carboxylated Polyester Resin

The nonisothermal crystallization process of polycaprolactone (PCL)/crosslinked carboxylated polyester resin (CPER) blends has been investigated for different blend concentrations by differential scanning calorimetry (DSC). The DSC measurements were carried out under different cooling rates namely: 1, 3, 5, 10, and 20°C/min. Thermally induced crosslinking of CPER in the blends was accomplished using triglycidyl isocyanurate as a crosslinking agent at 200°C for 10 min. The cured PCL/CPER blends were transparent above the melting temperature of PCL and only one glass transition temperature, T_g, located in the temperature range between the two T_gs of the pure polymer components, was observed, indicating that PCL and crosslinked CPER are miscible over the entire range of concentration. The nonisothermal crystallization kinetics was analyzed based on different theoretical approaches, including modified Avrami, Ozawa, and combined Avrami–Ozawa methods. All of the different theoretical approaches successfully described the kinetic behavior of the nonisothermal crystallization process of PCL in the blends. In addition, the spherulitic growth rate was evaluated nonisothermally from the spherulitic morphologies at different temperatures using polarized optical microscope during cooling the molten sample. Only one master curve of temperature dependence of crystal growth rate could be constructed for PCL/CPER blends, regardless of different blend concentrations. Furthermore, the activation energy of nonisothermal crystallization process (ΔE_a) was calculated as a function of blend concentration based on the Kissinger equation. The value of ΔE_a was found to be concentration dependent, i.e., increasing from 83 kJ/mol for pure PCL to 115 and 119 kJ/mol for 75 and 50 wt% PCL, respectively. This finding suggested that CPER could significantly restrict the dynamics of the PCL chain segments, thereby inhibit the crystallization process and consequently elevate the ΔE_a.     

Damping Properties of Blends Based on EVM

The mechanical and damping properties of blends of ethylene-vinyl acetate rubber (VA content >40% wt) (EVM)/ethylene-propylene-diene copolymer (EPDM) and EVM/nitrile butadiene rubber (NBR), both with 1.4 phr BIPB (bis (tert-butyl peroxy isopropyl) benzene) as curing agent, were investigated by dynamic mechanical analysis (DMA). The effect of added polyvinyl chloride (PVC), amido donor N-cyclohexyl-2-benzothiazole sulfonamide (CZ), and dicumyl peroxide (DCP) as a substitute curing agent, on the damping and mechanical properties of both rubber blends were studied. The results showed that in EVM/EPDM/PVC blends, EPDM was immiscible with EVM and could not expand the damping range of EVM at low temperature. PVC was miscible with EVM and dramatically improved the damping property of EVM at high temperature while keeping good mechanical performance. In EVM/NBR/PVC blends, PVC was partially miscible with EVM/NBR blends and remarkably widened the effective damping temperature range (EDTR) from 41.1°C for EVM/NBR to 62.4°C. Curing agents BIPB and DCP had a similar influence on EVM/EPDM blends. DCP, however, dramatically raised the height of tan δ peak of EVM/NBR = 80/20 and expanded its EDTR to 64.9°C. CZ had no obvious influence on the EVM/EPDM blends cured with BIPB. However, a small content of CZ enlarged the tan δ peak of EVM/NBR = 80/20 in both height and width, but at the cost of a deterioration of mechanical performance.     

A Study on Compatibility and Properties of POE/PS/SEBS Ternary Blends

Ethylene‐α‐olefin copolymer (POE)/polystyrene (PS)/poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) blends were prepared via melt blending in a co‐rotating twin‐screw extruder. The effects of SEBS copolymer on the morphology and rheological and mechanical properties of the blends were studied. Scanning electron microscopy (SEM) photos showed that the addition of SEBS copolymer resulted in finer dispersion of PS particles in the POE matrix and better interfacial adhesion between POE and PS compared with POE/PS blends, which exhibited a very coarse morphology due to the immiscibility between them. Interestingly, the tensile strength increased from 12.5 MPa for neat POE to 23.5 MPa for the POE/PS/SEBS (60/10/30) blend, whereas the tensile strengths of POE/PS (85.7/14.3) blend and POE/SEBS (66.7/33.3) blend were only 10.5 and 16.5 MPa, respectively. This indicates that both SEBS copolymer and PS have a synergistic reinforcing effect on POE. Dynamic mechanical thermal analysis (DMTA) and dynamic rheological property measurement also revealed that there existed some interactions between POE and SEBS as well as between SEBS and PS. DMTA results also showed that the storage modulus of POE increased when PS and SEBS were incorporated, especially at high temperature, which means that the service temperature of POE was improved.     

Effect of Polydispersity on the Phase Behavior of Polystyrene (PS)/Poly (Vinyl Methyl Ether) (PVME)

The thermodynamics and kinetics of phase separation in partially miscible blends of poly (vinyl methyl ether) (PVME) and two kinds of polystyrene (PS) with the same weight average molecular weight but different polydispersity were studied. The miscibility of PS/PVME with the monodisperse PS was better than that of PS/PVME with the polydisperse PS. Different morphology was observed for the two kinds of PS/PVME (10/90) blends during the nonisothermal phase separation process. The blend with monodisperse PS presented a co-continuous structure while the blend with polydisperse PS presented a viscoelastic phase separated network structure at a quench depth of 29°C. With increase of the heating rate, the increase of cloud point of PS/PVME (30/70) with polydisperse PS was smaller than that of PS/PVME (30/70) with monodisperse PS. During the isothermal phase separation of the critical composition (20/80) of PS/PVME with a quench depth of 30°C, it was found that the phase morphology of the two kinds of blends was nearly the same at the early stage of phase separation. However, as the dispersed phase, an approximately spherical droplet structure was observed in the blend with monodisperse PS at the late stage of phase separation, which did not appear in the blend with polydisperse PS.     

Proton spin relaxation in bisphenol-a polycarbonate,butyl rubber,and their composites

Proton spin-lattice relaxation times of bisphenol-A polycarbonate, butyl rubber, and blends of the two polymers were studied at 18 Mc/sec in the temperature range 90°-450°K. The proton spin-lattice relaxation is primarily dipolar in each polymer, due to methyl group reorientation and to reorientation of chain segments. In a blend of bisphenol-A polycarbonate with 7 and 10 wt of butyl, a nonexponential decay of magnetization was observed in the temperature range 280°-380°K. This was explained by the existence of two spin temperatures in these blends, indicating that processes which bring about the equilibrium within the spin system are slow compared to the spin-lattice relaxation times of the two components of the blend.     

The development of Li<Superscript>+</Superscript> conducting polymer electrolyte based on potato starch/graphene oxide blend

Solid polymer electrolytes based on potato starch (PS) and graphene oxide (GO) have been developed in this study. Blending GO with PS has improved the ionic conductivity and mechanical properties of the electrolytes. In this work, series of polymer blend consisting of PS and GO as co-host polymer were prepared using solution cast method. The most amorphous PS-GO blend was obtained using 80 wt% of PS and 20 wt% of GO as recorded by X-ray diffraction (XRD). Incorporation of 40 wt% lithium trifluoromethanesulfonate (LiCF₃SO₃) into the PS-GO blend increases the conductivity to (1.48 ± 0.35) × 10^?5 S cm^?1. Further enhancement of conductivity was made using 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]). The highest conductivity at room temperature is obtained for the electrolyte containing 30 wt% of [Bmim][Cl] with conductivity value of (4.8?0 ± 0.69) × 10^?4 S cm^?1. Analysis of the Fourier transform infrared spectroscopy (FTIR) spectra confirmed the interaction between LiCF₃SO₃, [Bmim][Cl], and PS-GO blend. The variation of the dielectric constant and modulus studies versus frequency indicates that system of PS-GO-LiCF₃SO₃-[Bmim][Cl] obeys non-Debye behavior.     

Microhardness Studies of the Interphase Boundary in Rubber‐Softened Glassy Polymer Blends Prepared with/without Compatibilizer

Abstract

The interphase boundary of incompatible polymer blends such as poly(methyl methacrylate) (PMMA)/natural rubber (NR) and polystyrene (PS)/NR, and of compatible blends such as PMMA/NR/epoxidized NR (ENR) and PS/NR/styrene–butadiene–styrene (SBS) block copolymer, where ENR and SBS were used as compatibilizers, was studied by means of microindentation hardness (H) and microscopy. Cast films of neat PMMA and PS, and blended films of PMMA/NR, PS/NR, PMMA/NR/ENR, and PS/NR/SBS were prepared by the solution method using a common solvent (toluene). Hardness values of 178 and 173 MPa were obtained on the surfaces of the neat PMMA and PS, respectively. After the inclusion of soft phases, the binary (incompatible) and the ternary (compatible) blend surfaces show markedly lower H‐values. Scanning electron and optical microscopy reveal a clear difference at the phase boundary of the surface of compatible (smooth boundary) and incompatible (sharp boundary) blends. The compatibilized blends were characterized by using microhardness measurements, as having the thinnest phase boundary (～30 µm), while incompatible blends were shown to present a boundary of about 60 µm. The hardness values indicate that the compatibilizer is smoothly distributed across the interface between the two blend components. Results highlight that the microindentation technique, in combination with microscopic observations, is a sensitive tool for studying the breadth and quality of the interphase boundary in non‐ or compatibilized polymer blends and other inhomogeneous materials.     

The effect of electric field stress on pure poly(vinyl chloride), poly(methyl methacrylate) and their polyblend samples

The TSDC and transient currents measurement have been carried out on pure poly(vinyl chloride), poly(methyl methacrylate) and polyblends of various weight ratios as a function of electric fields at constant poling temperature. For PVC and different blend samples single peak in the temperature range 100–170 °C has been observed in TSDC thermograms, however, for PMMA samples two peaks were observed at around 90 and 165 °C. The various TSDC parameters i.e. activation energy, charge released and relaxation times have been calculated. Results suggest that dipolar and space charge mechanism are dominant for observed current.     

Phase change behavior of polyethylene glycol in blends with cellulose

Thermodynamic properties and phase change behaviors of polyethylene glycol (PEG) in blends with cellulose (CELL) were found to be completely different than those of pure PEG. When the CELL fraction of the blend was larger than 5 wt%, PEG within the blend did not melt into a liquid state, as was the case with pure PEG, even at a temperature over 50°C above its melting point. Instead of fusion, a solid-solid phase transition was found in these PEG-CELL blends with an enthalpy as large as 100 J/g.     

Rheological properties and impedance spectroscopy of PMMA-PVdF blend and PMMA gel polymer electrolytes for advanced lithium batteries

In the present study, blend ionic conducting membranes formed by poly(methylmethacrylate (PMMA) / poly(vinilydenefluoride) (PVDF) (blend ratio PMMA/PVdF=80/20), lithium perchlorate (LiClO₄) as a salt and a mixture of ethylene carbonate (EC)-propylene carbonate (PC) as plasticizer are prepared and characterized by impedance spectroscopy and dynamic rheological experiments. We compared the results obtained on the blends with those on PMMA gel-based polymer electrolytes incorporating the same EC/PC mixture of plasticizer and the same quantities of salt. The main focus of this study is to illustrate the rheological data of the gels and blends electrolytes to point up their mechanical stability with the temperature in sight of the technological application. The conductivity values are reported in the 20–100 °C temperature range for different lithium salt contents, while the rheological behaviour has been recorded up to 140 °C. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Dielectric relaxation in polyvinylidenefluoride–polysulfone blends

Dielectric properties of polymer blend of polyvinylidenefluoride (PVDF) and polysulfone (PSF) of different wt. % have been studied to understand the molecular motion and their relaxation behavior in the frequency range of 100 Hz to 10 kHz at different temperatures between 30 and 190 °C. The dielectric constant of the blend decreased with frequency and increased with the increasing temperature and PSF content in the blend. The magnitude of dielectric loss also increased with increase in temperature and PSF content. The observed characteristic has been consistently explained in terms of dipolar motions and the plasticization effect brought about by blending of PSF with PVDF. At constant frequency and temperature, the blend follows a linear relationship between logarithm of their dielectric constant and different ratios of blend. The appearance of a peak for each concentration in dielectric loss suggests the presence of relaxing dipoles in the blend. In addition of PSF with PVDF, the peak shifts toward higher frequency side suggesting the speed up the relaxation process. AC dielectric data is also combined with thermally stimulated depolarization current (TSDC) data which is generally studied for low-frequency dielectric properties of polymers blends so as to produce the results in a wide frequency range. The glass transition temperature (T_g) of the blend was studied by differential scanning calorimetric technique (DSC), the T_g was compared and correlated with TSDC peak. The blend samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to study the formation of blend and micro structural properties of the materials. The shifting of peak toward lower diffraction angle side confirms the reduction in particle size with increasing amorphous content in the blend.     

Solution blends of polyacrylonitrile with segmented polyurethanes: Effect of soft segments

Solution blends of a modified polyacrylonitrile (PAN) with polyurethane (PU) obtained from 4, 4′-diphenylmethane diisocyanate (MDI) and two different types of polyols– i.e., ether-linked polytetramethylene ether glycol (PTEG) and ester-linked polytetramethylene adipate glycol (PTAG) – were prepared in N, N-dimethylformamide (DMF). The domains in the PTAG-PU blends were much finer than those in the PTEG-PU blends. Shift of the soft segment transition temperatures (T _gs) of PU toward lower temperature with increasing PAN was more significant for PTAG-PU blends. Miscibility was also examined through Fourier transform infrared spectra. These showed clear carbonyl peak shifts due to the different types of hydrogen bonding. The PTAG-PU/PAN (30/70) blend had the maximum draw ratio at failure, measured in 100°C water; it was over 2.5 times that of pure PAN.     

STRUCTURE-PROPERTY RELATIONS IN REACTION-INDUCED,PHASE-SEPARATED POLY(2-PHENOXYETHYL ACRYLATE)/POLYSTYRENE BLENDS

Structure-property relations were studied in reaction-induced, phase-separated polymer blends. An amorphous-amorphous system consisted of polystyrene (PS) dissolved in the monomer 2-phenoxyethyl acrylate (POA). When the POA was polymerized to poly(2-phenoxyethyl acrylate) (PPOA), phase separation and phase inversion were induced, and a polymer blend was formed. The reaction kinetics were measured by monitoring the reduction in the intensity of the C╤C stretching vibration band in the Raman spectrum of POA. The phase separation kinetics were determined using light transmission experiments and were combined with the reaction kinetics so that a ternary phase diagram could be defined for the reactive system. Structure development was monitored using small-angle laser light scattering (SALLS) and optical microscopy, which showed that spinodal decomposition was the mechanism of liquid-liquid phase separation. Plots of the relative invariant with time showed an increase in the degree of phase separation. The Fourier transforms of the microscopy images had peaks in the radial intensity distributions, again implying that spinodal decomposition was the phase separation mechanism. Tensile testing showed that PPOA was soft and rubbery at 20°C. Both PS and PPOA had comparable toughness when tested to failure; however, the blend containing 17 wt% PS had a toughness more than 10 times that of either PS or PPOA in isolation. Both modulus and tensile strength increased with PS content, while the ultimate strain decreased. The Nielsen model best described the tensile modulus data, providing further evidence for co-continuous phase structure.     

Preparation and Evaluation of the Morphology,Flammability, and Mechanical Properties of the Acrylonitrile‐Butadiene‐Styrene/Poly (vinyl chloride) Blends

Blends of two grades of acrylonitrile‐butadiene‐styrene (ABS) with three different compounds of poly (vinyl chloride) (PVC) were prepared via melt processing and their morphology, flammability, and physical and mechanical properties were investigated. SEM results showed that the ABS/PVC blend is a compatible system. Also, it can be inferred from fracture surface images that ABS/PVC blends are tough, even at low temperatures. It was found that properties of these blends significantly depend on blend composition and PVC compound type; however, the ABS types have only a small effect on blend properties. On blending of ABS with a soft PVC compound, impact strength, and melt flow index (MFI) increased, but tensile and flexural strength decreased. In contrast, blending of ABS with a rigid PVC compound improved fire retardancy and some mechanical properties and decreased MFI and impact strength.     

Solid electrolyte membranes from semi-interpenetrating polymer networks of PEG-grafted polymethacrylates and poly(methyl methacrylate)

Solid polymer electrolyte membranes were prepared as semi-interpenetrating networks by photo-induced polymerization of mixtures of poly(ethylene glycol) (PEG) methacrylate macromonomers in the presence of poly(methyl methacrylate) (PMMA) and lithium bis(trifluoromethanesulfonyl)imide salt. The composition of the membranes was varied with respect to the PMMA content, the degree of cross-linking, and the salt concentration. Infrared analysis of the membranes indicated that the lithium ions were coordinated by the PEG side chains. Calorimetry results showed a single glass transition for the blend membranes. However, dynamic mechanical measurements, as well as a closer analysis of the calorimetry data, revealed that the blends were heterogeneous systems. The ionic conductivity of the membranes increased with the content of PEG-grafted polymethacrylate, and was found to exceed 10^− 5 S cm^− 1 at 30 °C for membranes containing more than 85 wt.% of this component in the polymer blend.     

Morphological Aspects of In-Situ Compatiblized Binary Polymer Blends With Variable Viscosity Ratios of Components

The in-situ compatiblized binary polymer blend polypropylene(PP)/polystyrene(PS)/ anhydrous aluminum chloride(AlCl₃) was selected as a model system of a reactive polymer blend to investigate the effect of viscosity ratio of components at a constant shear rate on the phase morphological behavior in in-situ compatibilized systems. The results showed that the well-known interfacial compatibilization effect was related to variations of viscosity ratios of components in the reactive PP/PS blends with different contents of AlCl₃ catalyst. The phase morphology evolution of the in-situ compatiblized reactive blend was determined by both the interfacial compatibilization and the variation of the viscosity ratio of components under the fixed mixing conditions, which showed characteristics obviously different from and much more complex than those in binary polymer blends generally compatiblized by added compatiblizers. The results implied that the variation of the viscosity ratio of components should be checked carefully and taken into account if necessary, when the phase morphology of binary polymer blends is investigated, especially in complex in-situ compatiblized reactive polymer blends.     

Nanocomposites based on polymer blends: enhanced interfacial interactions in polycarbonate/ethylene-propylene copolymer blends with multi-walled carbon nanotubes

In this article, the phase separation in the melt blended polycarbonate (PC) and ethylene propylene copolymer (EPC) has been studied with dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). Two glass transition temperatures on the tan δ curves were detected. This confirms the immiscibility of PC and EPC phases. Different content of multi-walled carbon nanotubes (MWCNTs) were added to the PC/EPC blends and the interfacial adhesion between MWCNTs and PC/EPC blend were shown using transmission electron microscopy (TEM). The MWCNTs were located in the PC phase and at the interfaces of PC and EPC phases. Moreover, the storage modulus (E′) of polymer blends was changed by the increasing content of EPC elastomer and MWCNTs. The value of E′ of PC decreased with an incorporation of EPC. While, along with an addition of MWCNTs in the PC/EPC blends an increase of E′ was visible. The strong interfacial interactions between the matrix and MWCNTs played the main role in increasing the values of the E′ of the nanocomposites.