Mechanical behavior of polycarbonate/phenoxy blends before and after interchange reactions

Melt-mixed blends of polycarbonate/phenoxy were obtained before and after Interchange reactions by controlling the processing time. The dynamic mechanical analysis of the physical and reacted blends confirmed the immiscibility of the pair and the displacement of the glass-transition temperatures of the mixtures; this displacement was seen more clearly in the reacted mixtures, and at phenoxy-rich contents, even a single phase can appear. The exchange reactions resulted in a mechanical behavior that showed both a higher modulus and greater tensile strength in the reacted blends. The ductility was close to linearity for the physical blends and probably would be improved in the reacted mixture with a lower processing time.     

Phase behavior of ternary PBT–PC/phenoxy blends

Ternary polymer blends were obtained by melt mixing, mixing up to 30% poly(butylene terephthalate) (PBT) with polycarbonate (PC) and phenoxy in an attempt to improve the miscibility of the PC/phenoxy binary blend. Although most of the blends with a PBT content higher than 10% appear as transparent, two T_g's appeared at all the blend compositions. These T_g's correspond to PC-rich and phenoxy-rich phases where a low amount of the main component of the other phase and all PBT are dissolved in amounts that are a function of the PC/phenoxy ratio of the blend. Increasing the PBT contents in the blends closes to linearity the torque versus composition plot, so that a relationship between miscibility level and viscosity exists in these blends.     

The phase behavior and mechanical properties of polyarylate and polycarbonate blends

The phase behavior and mechanical properties of a series of polyarylate/polycarbonate blends were studied. The polymers are known to transesterify, the extent of which depends upon the thermal and shear history and affects phase behavior and properties. Single screw extrusion, twin screw extrusion, and solution casting were employed for blend preparation. Two transition temperatures, corresponding to a polycarbonate-rich phase and to a polyarylate-rich phase, were seen in blends that were solution cast or compounded in a single screw extruder at 285°C. But after injection molding a single T_g was observed, When annealed at 180°C for several hours the molded blend was found to phase separate. Blends that were compounded in a twin screw extruder exhibited a single T_g and could not be phase separated. The flexural and tensile properties of blends that were prepared in a twin screw extruder show a small positive synergism. But the impact properties were substantially below the rule of mixtures values, probably the result of advanced exchange reaction and thermal degradation.     

Characterization of ternary blends containing polycarbonate,tetramethyl polycarbonate,and poly (ϵ-caprolactone)

The phase behavior of ternary blends of bisphenol-A polycarbonate (PC), tetramethyl bisphenol-A polycarbonate (TMPC), and poly (?-caprolactone) (PCL), where each binary pair forms completely miscible blends, was investigated. The ternary blends were found to be miscible for all compositions and do not phase separate prior to thermal decomposition. The melting point depression method based on both the Flory-Huggins theory and the equation of state theory of Sanchez-Lacombe was used to evaluate interaction parameters for each pair.     

Binary and ternary blends of polylactide, polycaprolactone and thermoplastic starch

In this study binary and ternary blends of polylactide (PLA), polycaprolactone (PCL) and thermoplastic starch (TPS) are prepared using a one-step extrusion process and the morphology, rheology and physical properties are examined. The morphology and quantitative image analysis of the 50/50 PLA/TPS blend transverse phase size demonstrate a bimodal distribution and the addition of PCL to form a ternary blend results in a substantial number of fine dispersed particles present in the system. Focused ion beam irradiation, followed by atomic force microscopy (AFM) shows that dispersed PCL forms particles with a size of 370 nm in PLA. The TPS phase in the ternary blends shows some low level coalescence after a subsequent shaping operation. Dynamic mechanical analysis indicates that the temperature of the tan δ peak for the PLA is independent of TPS blend composition and that the addition of PCL in the ternary blend has little influence on the blend transitions. Both the α and β transitions for the thermoplastic starch are highly sensitive to glycerol content. When TPS of high glycerol content is blended with PLA, an increase in the ductility of the samples is achieved and this effect increases with increasing volume fraction of TPS. The ternary blend results in an even greater ductility with an elongation at break of 55% as compared to 5% for the pure PLA. A substantial increase in the notched Izod impact energy is also observed with some blends demonstrating three times the impact energy of pure PLA. The mechanical properties for the ternary blend clearly indicate a synergistic effect that exceeds the results obtained for any of the binary pairs. Overall, the ternary blend approach with PLA/TPS/PCL is an interesting technique to expand the property range of PLA materials.     

Phase behavior and rheology of blends containing polycarbonate and a thermotropic polyester

The phase behavior and rheology of binary blends of polycarbonate (PC) and a liquid crystalline polymer (LCP) have been investigated. The thermotropic LCP employed was a semiflexible polyester synthesized by melt condensation of t-butylhydroquinone and 4,4′ dichloroformyl-α,ω-diphenoxyhexane. It shows a distinct nematic-to-isotropic transition in the pure state and in the blends. Results of DSC and optical microscopy indicate that the LCP is solubilized in the mixture for weight fractions of LCP less than about 0.05 and shows partial miscibility with PC over the rest of the composition range. The phase separation is considered to be driven by both isotropic and anisotropic interactions between constituent chains. Dynamic oscillatory measurements show that there is some interaction between the separate isotropic and anisotropic phases, with complex viscosities of the blends being intermediate between those of pure components and showing significant deviation from a logarithmic rule-of-mixtures. © 1996 John Wiley & Sons, Inc.     

Development of interchange reactions in ternary PBT-PC/phenoxy blends

Ternary PBT-PC/phenoxy blends were melt mixed for periods of time up to 110 min to determine the development of interchange reactions among the blend components. This development was evaluated by means of solvent extraction and DSC measurements on blends obtained after characteristic blending times shown in the torque vs. blending time curve. PBT reacts, after very short blending times and, probably due to residual catalyst, mainly with phenoxy. Although at high phenoxy contents a single torque peak is observed, at low phenoxy contents two peaks are observed that correspond to the two stages in which the reaction takes place: at the beginning in the phenoxy-rich phase and later in the overall blend.     

The flow-induced phase morphology of fluoroelastomer and polycarbonate blends during extrusion

The flow-induced phase morphological development under different extrusion conditions was studied in terms of the rheological property and interfacial tension of various elastomers and thermoplstics. The interfacial tension for elastomers and thermoplastics was investigated by using a breaking thread method (1-4). We found that the method is suitable for measuring interfacial tension without degradation. The droplet-fibrillation transition phenomenon was observed in various extrudates of fluoroelastomer/polycarbonate blends. The criteria for the flow-induced morphology, in particular the droplet-fibrillation transition, are critically discussed in this paper.     

Phase behavior of ternary polymer blends

The effect of varying interaction parameters on the phase diagrams of ternary polymer blends was explored by simulating spinodals through use of the Flory-Huggins lattice theory. Results indicate that miscibility is favored for the case of ternary mixtures of marginally miscible or marginally immiscible pairs where all pair interactions are nearly athermal. Miscibility is restricted for asymmetric ternary blends when one of the polymer pairs is either strongly miscible or strongly immiscible. For symmetric blends of partially immiscible pairs, both two-phase and three-phase miscibility gaps are predicted.     

Electrospun polycaprolactone/polyglyconate blends: Miscibility,mechanical behavior,and degradation

Electrospun blends of polycaprolactone and polyglyconate were prepared for the first time to evaluate the synergistic properties. The morphology and thermal properties of the blends were used to determine the degree of miscibility. Dynamic mechanical analysis was used to evaluate the mechanical performance and viscoelastic properties of the blends. In vitro degradation studies in phosphate buffered saline (pH of 7.3) were carried out to investigate the hydrolytic degradation of the polymer system. FT-IR and SEM analysis, DSC, and mechanical testing were performed to evaluate the degradation profiles of the blends. A 3:1 ratio of polyglyconate to polycaprolactone was concluded to be a partially miscible blend with enhancements in tensile strength, flexibility, and percent elongation to failure over neat polyglyconate. In addition, the 3:1 ratio of polyglyconate to polycaprolactone scaffold exhibited a stable morphology, modulus of elasticity, and mass up to 6 weeks in vitro.     

Crystallization behavior and rheological properties of polycarbonate and polypropylene blends

Crystallization behavior and rheological properties of blends of bisphenol-A polycarbonate (PC) and polypropylene (PP) prepared by screw extrusion have been investigated by differential scanning calorimetry (DSC), polarized-light microscopy, scanning electron microscopy, and a Rheometrics Mechanical Spectrometer. In the study of thermal analysis of PC-PP blends by DSC, double crystallization peaks were observed in the PC-rich compositions. In the study of spherulite of 7/3 PC-PP blend, large droplets (>25 μm) of PP were crystallized between 115°C and 105°C, and then small droplets (<10 μm) of PP were crystallized at about 90°C. This result is consistent with the double crystallization behavior such that heterogeneous and homogeneous nucleations have been observed at about 105°C and about 85°C, respectively, by DSC measurements. From the results of rheological properties of the PC-PP blends, the storage modulus of the PC-PP blends at low frequencies has larger value than that of the simple mixing rule. The elasticity increase from the simple mixing rule is consistent with the emulsion model for a dispersed system.     

Analysis of mechanical,thermal, and morphological behavior of polycaprolactone/wood flour blends

In the present study, the properties of polycaprolactone (PCL) and wood flour (WF) blends were examined by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), Instron mechanical tester, and scanning electron microscopy (SEM). As for results, the mechanical properties of PCL were lowered obviously, due to the poor compatibility between the two phases, when it was blended with wood flours. A fine dispersion and homogeneity of wood flour in the polymer matrix could be obtained when the acrylic acid grafted PCL (PCL‐g‐AA) was used to replace PCL for manufacture of blends. This better dispersion is due to the formation of branched and crosslinked macromolecules since the PCL‐g‐AA copolymer had carboxyl groups to react with the hydroxyls. This is reflected in the mechanical and thermal properties of the blends. In comparison with pure PCL/WF blend, the increase in tensile strength at break was remarkable for PCL‐g‐AA/WF blend. The PCL‐g‐AA/WF blends are more easily processed than the PCL/WF ones since the former had lower melt viscosity than the latter. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1000–1006, 2004     

The phase behavior,mechanical, and rheological characteristics of blends containing nitrile polymers and poly(ethylene-co-maleic anhydride)

The phase behavior of binary blends of acrylonitrile/methyl acrylate/butadiene terpolymer (B210) and poly(ethylene-co-maleic anhydride) (PEMA) was examined based on thermal analysis and optical microscopy. Miscibility of these polymer blends was recognized over a wide range of compositions. The appearance of phase separation during subsequent heatings above the glass transition temperature (T_g) of these blends was associated with a lower critical solution temperature (LCST) behavior. Rheological characteristics such as shear storage modulus (G′), loss modulus (G″) and complex viscosity have been shown to depend on the amount of PEMA in the blend. Mechanical properties including the tensile strength and flexural modulus also were found to be related to the composition of the blend. © 1993 John Wiley & Sons, Inc.     

Phase behavior of polycarbonate blends with selected halogenated polymers

Bisphenol A polycarbonate is shown to be miscible with a vinylidene chloride based polymer containing 13.5% by weight of vinyl chloride. On the other hand, polycarbonate is found to be immiscible with poly(vinyl chloride), poly(vinylidene fluoride), and polyepichlorohydrin.     

Thermal properties and crystallization behavior of polyolefin ternary blends

Crystallization behaviors, spherulite growth and structure, and the crystallization kinetics of polypropylene (PP)/ethylene‐α‐olefln copolymer (mPE)/high‐density polyethylene (HDPE) ternary blends and of mPE/HDPE binary blends have been studied using polarizing optical micrography (POM) and differential scanning calorimetry (DSC). In mPE/HDPE blends, large pendant groups of mPE disturbed spherulite growth of HDPE, leading to a different crystallite morphology and isothermal kinetics. Non‐isothermal properties, morphology, and isothermal crystallization kinetics of PP in ternary blends were significantly influenced by the composition and crystallization behavior of the mPE/HDPE binary blends as well as the crystallization condition. Polym. Eng. Sci. 44:1858–1865, 2004. © 2004 Society of Plastics Engineers.     

Polymeric antiplasticization of polycarbonate with polycaprolactone

Physical blends of polycarbonate (PC) with polycarprolactone (PCL), containing 0 to 30% PCL were prepared by melt mixing. The compatible blends were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), mechanical testing, rheological and density measurements. Yield strength, elastic modulus, and density of the blends were found to attain maximum values, depending on PCL content, while T_g continuously decreased. PCL presence resulted in the embrittlement of PC as detected by impact and tensile tests. These combined data lead to propose a mechanism of polymeric antiplasticization in the PC/PCL system; a phenomenon uncommon in polymer-polymer blends. Simultaneously, the PC's β-transition intensity was depressed, as detected by DMA. Activation energy of PC secondary relaxation process was found to be higher for PC/PCL blends than for PC. Thus, local, intermolecularly non-cooperative motions, usually associated with β-relaxation, are restricted in the presence of PCL. The addition of PCL to PC results in increased shear sensitivity and lower high shear rates viscosity, improving processability.     

Melting and crystallization behavior of miscible copolyester–polycarbonate blends

The melting and crystallization behavior of Kodar, a copolyester formed from 1,4-cyclohexanedimethanol and a mixture of terephthalic and isophthalic acids, and its miscible blends with polycarbonate was examined. The results of the melting behavior are discussed in terms of crystallization-induced chemical rearrangements and the copolymeric character of Kodar and interchange reactions between components when polycarbonate is present in the blend. For various reasons, the melting behavior cannot be extrapolated to infinite crystal size using the Hoffman–Weeks approach. Crystallization kinetics follows the Avrami equation, with rates being higher when the crystallization temperatuare is approached from the glass rather than from the melt. The kinetic data are discussed in terms of modern theories. An approximate melting point depression analysis is used to estimate the interaction parameter for the blend, and the result obtained is compared to a value from another technique.     

Miscibility,phase behavior,and mechanical properties of ternary blends of poly(vinyl chloride)/polystyrene/chlorinated polyethylene-graft-polystyrene

The effectiveness of chlorinated polyethylene-graft-polystyrene (CPE-g-PS) as a polymeric compatibilizer for immiscible poly(vinyl chloride)/polystyrene (PVC/PS) blends was investigated. The miscibility, phase behavior, and mechanical properties were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Izod impact tests, tensile tests, and scanning electron microscopy (SEM). DSC and DMA studies showed that PVC is immiscible with chlorinated polyethylene (CPE) in CPE-g-PS, whereas the PS homopolymer is miscible with PS in CPE-g-PS. The PVC/PS/CPE-g-PS ternary blends exhibit a three-phase structure: PVC phase, CPE phase, and PS phase that consisted of a PS homopolymer and PS in CPE-g-PS. The mechanical properties showed that CPE-g-PS interacts well with both PVC and PS and can be used as a polymeric compatibilizer for PVC/PS blends. CPE-g-PS can also be used as an impact modifier for both PVC and PS. SEM observations confirmed, after the addition of CPE-g-PS, improvement of the interfacial adhesion between the phases of the PVC/PS blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 995–1003, 1998