Poly(butylene terephthalate)–polyarylate blends

In this paper we focus on miscible blends of two engineering polymers: poly(butylene terephthalate) (PBT) and a polyarylate (PAr). The issue of transesterification in these blends will be addressed, followed by a discussion of the crystallization kinetics of PBT, poly(ethylene terephthalate) and several PBT/PAr blends. The ability to estimate polymer–polymer interaction parameters in blends from melting point depression will also be discussed. The amorphous phase behavior of the PBT/PAr blends has been explored primarily using dielectric spectroscopy. For blends in which PBT has crystallized, we observe two relaxations associated with T_g-like motion, and this behavior is interpreted in light of our recent work on order–disorder interphases in crystalline blends.     

X-ray scattering and thermal analysis study of the effects of molecular weight on phase structure in blends of poly(butylene terephthalate) with polycarbonate

Blends of Poly(butylene terephthalate), PBT, with Polycarbonate, PC, were studied for a range of molecular weights and blend compositions. Blends were available in PBT/PC compositions 80/20 and 40/60, and with M_w designated by H (high) or L (low). Samples were prepared by melt crystallization, or by cold crystallization following a rapid quench from the melt. Addition of PC reduces the crystallization kinetics of PBT so that the resulting crystals are more perfect than those which form in the homopolymer. Degree of crystallinity of the blends followed the rank ordering: L/L > L/H > H/L = H/H. The glass transition behavior was investigated using dynamic mechanical analysis (DMA) and modulated differential scanning calorimetry (MDSC). All blends exhibited two glass transitions at intermediate temperatures between the T_gs of the homopolymers, indicating existence of a PBT-rich phase and a PC-rich phase. Blends L/L were most, and H/H the least, miscible. Small-angle X-ray scattering was performed at room temperature on cold crystallized blends, or at elevated temperature during melt crystallization. The long period was consistently larger, and the linear stack crystallinity was consistently smaller, in blends L/L or H/L. These results indicate that in blends containing low M_w PC, there is more PC located within the PBT-rich phase. The long period was consistently smaller in cold crystallized samples, while the linear stack crystallinity was nearly the same, regardless of melt or cold crystallization treatment. Reduction of the average long period in cold crystallized samples could result from crystallization of PBT within the PC-rich phase. This is consistent with thermal analysis results, which indicate that cold crystallized samples have greater overall crystallinity than melt crystallized samples. A hypothetical liquid phase diagram is presented to explain the differences between melt and cold crystallized blends. © 1996 John Wiley & Sons, Inc.     

聚环氧乙烷(PE0)与聚双酚A羟基醚(PBHE)共混体系的研究

 用偏光显微镜(PLM)、扭辫(TBA)、IR及WAXD对PEO/PBHE共混体系结晶形态进行了研究。结果表明,PEO含量在50％以上的共混体系,几乎完全被PEO球晶充满,非晶态PBHE作为微区分散在大球晶之间或球晶之中。PEO含量为40％和30％的照片上呈现树枝晶。PEO含量为20％以下时照片中不再看到结晶出现,PEO与PBHE形成单一非晶相。PEO/PBHE共混体系的组分之间存在着氢键相互作用,这种作用强于PBHE分子间的氢键作用。共混体系的结晶度及T_g随PBHE组分含量的增加,前者减小后者增加并符合FOX方程揭示的规律。PEO与PBHE具有很好的相容性。     

Miscible blends prepared from two crystalline polymers

Differential scanning calorimetry was used to determine the miscibility behavior of several polyester/Saran blends, the two polymers forming these blends being semicrystalline. It was found that Saran is miscible with polycaprolactone (PCL), polyvalerolactone, poly(butylene adipate), and poly(hexamethylene sebacate) since a single glass transition temperature T_g was observed at each composition. However, immiscibility was found between Saran and poly(ethylene adipate), poly-(ethylene succinate), poly(β-propiolactone), and poly(α-methyl-α-n-propyl-β-propiolactone) since two T_g's were recorded at several compositions. Blends were then obtained containing, over a wide range of composition, a miscible amorphous phase and two different types of crystals. From melting-point depression data on PCL and Saran crystals, thermodynamic interaction parameters χ were calculated and found to be different for PCL-rich blends and for Saran-rich blends. This result suggests a variation of χ with composition. Saran is a polymer which does not contain α-hydrogens and its miscibility with polyesters may result from a β-hydrogen bonding interaction or a C?O/C? Cl dipole-dipole interaction.     

Miscibility of a polyarylate with a liquid crystalline copolyester

The miscibility has been investigated for binary blends of a polyarylate (PAr) with a liquid crystalline copolyester of p-hydroxybenzoate and ethylene terephthalate units in a 6/4 molar ratio (PET/PHB). The binary blends were prepared by solution precipitation. The transitions of the PET/PHB have been measured with a rheometrics dynamic spectrometer. The phases in blends have been studied with a differential scanning calorimeter, by ther-mogravimetry and with a polarizing optical microscope. The blends exhibit two glass transitions (T_gs) over the composition range 10–90 wt %. The amorphous PET phase from the PET-PHB is found to be partially miscible with PAr, which leads to a decrease of the PAr T_g. The amount of this partially miscible portion of PET has been estimated by the Couch-man equation. On heat treatment of the blends at 250 to 300°C, transesterficiation takes place, as judged by the shift of the higher of the two T_gs. © 1993 John Wiley & Sons, Inc.     

Steady-state permeation of carbon dioxide through a miscible,glassy polymer blend

Steady-state permeation measurements are reported for carbon dioxide (CO₂) through quenched, amorphous films of a miscible blend of poly(butylene terephthalate) (PBT) and a random copolyester of bisphenol-A and iso/terephthalate acids (PAr). Permeabilities were determined at 35°C on blends with up to 60 wt % PBT and for CO₂ pressures up to 300 psi (2.06 MPa). At a fixed blend composition, the permeability, P̄, decays with driving pressure, p, as described by dual-mode models for gas transport in glassy polymers. From regression fits of the data to dual-mode model predictions for P̄(p), high-and low-pressure limiting permeabilities are determined. These decrease with PBT content in a manner indicating strong, favorable energetic interactions between the PBT and PAr components in the blend. © 1996 John Wiley & Sons, Inc.     

Miscible blends containing a crystallizable component: poly(vinyl alcohol)/poly(ethyleneimine)

Blends of poly(vinyl alcohol) (PVAI) with poly(ethyleneimine) (PEI) were prepared by casting from a common solvent. All blends show a single, composition dependent glass transition temperature (T_g), indicating that the blends are miscible in the amorphous state and in the melt. The overall crystallization rate of PVAI in the blend decreases with increasing PEI content. The crystallinity index of PVAI in the blend does not decrease greatly with PEI content up to a composition of 70/30 PVAI/PEI, since the T_g of the crystallizable component PVAI is larger than that of the non-crystallizable component PEI. The T_g of the system PVAI/PEI decreases with increasing PEI content. The interaction parameter B of the two polymers in the melt was found to be −24 J/cm³.     

Compatibility studies of blends of polycarbonate and poly(ethylene terephthalate)

Blends of bisphenol-A polyarbonate (PC) and poly(ethylene terephthalate) (PET) has been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were prepared by screw extrusion and solution casting with weight fractions of PC in the blends varying from 0.90 to 0.10. From the measured glass transition temperature (T_g) and apparent weight fractions of PC and PET dissolved in each phase, it appears that PET dissolves more in the PC-rich phase than does the PC in the PET-rich phase. The composition-dependent values of the Flory–Huggins polymer–polymer–interaction parameter were determined and found to be from 0.054 to 0.037 for extruded blends at 275°C and from 0.058 to 0.040 for solution casting at 25°C. The interaction parameter decreases with increasing PET concentration. This result is consistent with the values of the T_gs, the microscopy study, and the measured extrudate swell ratios which show that compatibility increases more in the PET-rich compositions than in the PC-rich compositions. The PC–PET blends are not microscopically miscible for all the blend compositions.     

Miscibility and interactions in blends of two proton‐donating polymers: Poly(acrylic acid)/poly(p‐vinylphenol) blends

Blends of poly(acrylic acid) (PAA) and poly(p‐vinylphenol) (PVPh) were prepared from N,N‐dimethylformamide (DMF) and ethanol solutions. The DMF‐cast blends exhibited single T_g's, as shown by modulated differential scanning calorimetry, whereas the ethanol‐cast blends had double T_g's. Fourier transform infrared spectroscopy showed that there was a specific interaction between PAA and PVPh in the DMF‐cast blends. The single‐T_g blends cast from DMF showed single‐exponential decay behavior for the proton spin–lattice relaxation in both the laboratory frame and the rotating frame, indicating that the two polymers mixed intimately on a scale of 2–3 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 789–796, 2003     

Preparation and characterization of poly(butylene terephthalate)/poly(ethylene terephthalate) copolymers via solid‐state and melt polymerization

To increase the T_g in combination with a retained crystallization rate, bis(2‐hydroxyethyl)terephthalate (BHET) was incorporated into poly(butylene terephthalate) (PBT) via solid‐state copolymerization (SSP). The incorporated BHET fraction depends on the miscibility of BHET in the amorphous phase of PBT prior to SSP. DSC measurements showed that BHET is only partially miscible. During SSP, the miscible BHET fraction reacts via transesterification reactions with the mobile amorphous PBT segments. The immiscible BHET fraction reacts by self‐condensation, resulting in the formation of poly(ethylene terephthalate) (PET) homopolymer. ¹H‐NMR sequence distribution analysis showed that self‐condensation of BHET proceeded faster than the transesterification with PBT. SAXS measurements showed an increase in the long period with increasing fraction BHET present in the mixtures used for SSP followed by a decrease due to the formation of small PET crystals. DSC confirmed the presence of separate PET crystals. Furthermore, the incorporation of BHET via SSP resulted in PBT‐PET copolymers with an increased T_g compared to PBT. However, these copolymers showed a poorer crystallization behavior. The modified copolymer chain segments are apparently fully miscible with the unmodified PBT chains in the molten state. Consequently, the crystal growth process is retarded resulting in a decreased crystallization rate and crystallinity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 882–899, 2007.     

A dielectric study of poly(ethylene-co-vinylacetate)–poly(vinyl chloride) blends. I. Miscibility and phase behavior

Measurements of the complex permittivity were used to study miscibility and phase behavior in blends of poly(vinyl chloride) (PVC) with two random ethylene—vinyl acetate (EVA) copolymers containing 45 and 70 wt % of vinyl acetate. The dielectric β relaxation of the pure polymers and blends was followed as a function of temperature and frequency for different blend compositions and thermal treatments. Blends of EVA 70/PVC were found to be miscible for compositions of about 25% EVA 70 and higher. Blends of lower EVA 70 content showed evidence of two-phase behavior. EVA 45/PVC blends were found to be miscible only at the composition extremes; at intermediate compositions these blends were two-phase, partially miscible. Both blend systems showed lower critical solution temperature behavior. Phase separation studies revealed that in the EVA 45/PVC blends, PVC was capable of diffusing into the higher T_g phase at temperatures below the T_g of the upper phase. In the blends, ion transport losses were significant above the loss peak temperatures, and in the two-phase systems, often obscured the upper temperature loss process. It was shown possible, however, to correct the loss curves for this transport contribution.     

Melting behavior,miscibility, and hydrogen-bonded interactions of poly(ε-caprolactone)/poly(4-hydroxystyrene-co-methoxystyrene) blends

The miscibility of poly(4-hydroxystyrene-co-methoxystyrene) (HSMS) and poly(ε-caprolactone) (PCL) was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). HSMS/PCL blends were found to be miscible in the whole composition range by detecting only a glass transition temperature (T_g), for each composition, which could be closely described by the Fox rule. The crystallinity of PCL in the blends was dependent on the T_g of the amorphous phase. The greater the HSMS content in the blends, the lower the crystallinity. The polymer–polymer interaction parameter, χ₃₂, was calculated from melting point depression of PCL using the Nishi-Wang equation. The negative value of χ₃₂ obtained for HSMS/PCL blends has been compared with the value of χ₃₂ for poly(4-hydroxystyrene) (P4HS)/PCL blends. The specific nature, quantitative analysis, and average strength of the intermolecular interactions in HSMS/PCL and P4HS/PCL blends have been determined at room temperature and in the molten state by means of Fourier transform infrared spectroscopy (FTIR) measurements. The FTIR results have been in good correlation with the thermal behavior of the blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 95–104, 1998     

Linear unsaturated polyester + poly(?-caprolactone) blends: Calorimetric behaviour and morphology

Blends of a linear unsaturated polyester (LUP, commercially named Al100) with poly(?-caprolactone) (PCL) of different molecular weights have been studied. The miscibility and crystallinity have been analyzed through FT-IR spectroscopy, differential scanning calorimetry (DSC) and environmental scanning electronic microscopy (ESEM). All the blends were subjected to the same heat treatment consisting of crystallizing during 45 min at constant temperature (10, 20, 30 or 40 °C). The glass transition temperature, T_g, and fusion temperature, T_fus, have been determined in the whole composition range for each blend. The T_g-composition dependence and the high degree of crystallinity detected at intermediate blend compositions denote an anomalous behaviour that could indicate the lack of homogeneity (phase separation) in the different blends studied. The ESEM measurements confirm the lack of homogeneity of the amorphous region in blends with high content of LUP. The results have been discussed as a function of the crystallization temperature and the molecular weight of PCL.     

Thermal and dynamic mechanical properties of PES/PPS blends

Blends of poly(ether-sulfone) (PES) and poly(phenylene sulfide) (PPS) with various compositions were prepared using an internal mixer at 290°C and 50 rpm for 10 min. The thermal and dynamic mechanical properties of PES/PPS blends have been investigated by means of DSC and DMA. The blends showed two glass transition temperatures corresponding to PPS-rich and PES-rich phases. Both of them decreased obviously for the blends with PES matrix. On the other hand, T_g of PPS and PES phase decreased a little when PPS is the continuous phase. In the blends quenched from molten state the cold crystallization temperature of PPS was detected in the blends of PES/PPS with mass ratio 50/50 and 60/40. The melting point, crystallization temperature and the crystallinity of blended PPS were nearly unaffected when the mass ratio of PES was less than 60%, however, when the amount of PES is over 60% in the blends, the crystallization of PPS chains was hindered. The thermal and the dynamic mechanical properties of the PPS/PES blends were mainly controlled by the continued phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of copolymer composition of polyestercarbonate on miscibility with poly(butylene terephthalate)

Blends of poly(butylene terephthalate) (PBT) and polyestercarbonate (PEC), copolyesters consisting of polycarbonate (PC) and polyarylate (PAr), have been studied by thermal analysis to determine miscibility. The PBT blends with PAr and PEC containing 30 wt % of carbonate unit or less appeared to be miscible, and the tendency for stable single‐phase was observed to decrease as the content of carbonate unit in PEC copolymer increased. As determined with the crystalline phase behavior, the miscibility of PEC with PBT appeared to have a maximum around 10 ∼ 30 wt % of carbonate content in PEC copolymer, and this result was attributed to the internal repulsion effect between ester and carbonate repeating units in PEC copolymer. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 803–811, 2000     

Styrene 4‐vinylbenzocyclobutene copolymer for microelectronic applications

Styrene and 4‐vinylbenzocyclobutene (vinyl‐BCB) random copolymers were prepared by free radical polymerization and studied for suitability as a dielectric material for microelectronic applications. The percentage of vinyl‐BCB in the copolymer was varied from 0 to 26 mol % to optimize the physical and mechanical properties of the cured copolymer as well as the cost. Copolymer in which 22 mol % of vinyl‐BCB was incorporated along with styrene produced a thermoset polymer which, after cure, did not show a T_g before decomposition at about 350 °C. The polymeric material has a very low dielectric constant, dissipation factor, and water uptake. The fracture toughness of the copolymer was improved with the addition of 20 wt % of a star‐shaped polystyrene‐block‐polybutadiene. Blends of the poly(styrene‐co‐vinyl‐BCB) with the thermoplastic elastomer provided material that maintained high T_g of the cured copolymer with only a slight decrease in thermal stability. The crosslinked styrenic polymer and toughened blends possess many properties that are desirable for high frequency‐high speed mobile communication applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2799–2806, 2008     

Phase behavior and interactions in blends of poly[(butylene adipate)-co-poly(butylene terephthalate)] copolyester with poly(4-vinyl phenol)

Miscibility with a linear T _g–composition relationship was proven for blend of poly(butylene adipate-co-butylene terephthalate) [P(BA-co-BT)] with poly(4-vinyl phenol) (PVPh). In comparison to the blends of PBA/PVPh and poly(butylene terephthalate) (PBT)/PVPh, the Kwei’s T _g model fitting on data for the P(BA-co-BT)/PVPh blend yields a q value between those for the PBA/PVPh and PBT/PVPh blends. The q values suggest that the interaction strength in the P(BA-co-BT)/PVPh blend is not as strong as that in the PBT/PVPh blend. Upon mixing the PVPh into the immiscible blend of PBA and PBT, the ternary PBA/PBT/PVPh blends only exhibits partial miscibility. Full-scale ternary miscibility in whole compositions is not possible owing to the significant ∆χ effect (χ _ij  – χ _ik ). The wavenumber shifts of the hydroxyl IR absorbance band indicates that the H-bonding strength is in decreasing order—PBT/PVPh > P(BA-co-BT)/PVPh > PBA/PVPh—and shows that the BA segment in the copolymer tends to defray interactions between P(BA-co-BT) and PVPh in blends.     

Segmental and secondary dynamics in hydrogen‐bonded poly(4‐vinylphenol)/poly(methyl methacrylate) blends

Broadband dielectric spectroscopy was used to study the segmental (α) and secondary (β) relaxations in hydrogen‐bonded poly(4‐vinylphenol)/poly(methyl methacrylate) (PVPh/PMMA) blends with PVPh concentrations of 20–80% and at temperatures from ?30 to approximately glass‐transition temperature (T_g) + 80 °C. Miscible blends were obtained by solution casting from methyl ethyl ketone solution, as confirmed by single differential scanning calorimetry T_g and single segmental relaxation process for each blend. The β relaxation of PMMA maintains similar characteristics in blends with PVPh, compared with neat PMMA. Its relaxation time and activation energy are nearly the same in all blends. Furthermore, the dielectric relaxation strength of PMMA β process in the blends is proportional to the concentration of PMMA, suggesting that blending and intermolecular hydrogen bonding do not modify the local intramolecular motion. The α process, however, represents the segmental motions of both components and becomes slower with increasing PVPh concentration because of the higher T_g. This leads to well‐defined α and β relaxations in the blends above the corresponding T_g, which cannot be reliably resolved in neat PMMA without ambiguous curve deconvolution. The PMMA β process still follows an Arrhenius temperature dependence above T_g, but with an activation energy larger than that observed below T_g because of increased relaxation amplitude. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3405–3415, 2004     

Synthesis of a random copolymer and its compatibility for thermotropic liquid crystalline polymer/poly(ether ether ketone) blends

A random copolymer (RCP) containing poly(ether ether ketone) (PEEK) and thermotropic liquid crystalline polymer (TLCP) segments was synthesized. Its chemical structure and liquid crystalline properties were characterized by FT‐IR, differential scanning calorimetry (DSC) and polar light microscopy (PLM) respectively. A single glass transition temperature (T_g) at 134.0°C, a melting temperature (T_m) at 282.0°C and a temperature of ignition (T_i) at 331.3°C can be observed. Blends of PEEK and TLCP with and without RCP as compatibilizer were prepared by extrusion and the effect of RCP on the thermal properties, dynamic mechanical properties, morphology and static tensile mechanical properties of blends was investigated by means of DSC, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), etc. Dynamic mechanical measurements indicated that there appeared to be only a single tan δ peak resulting from the glass transition of the PEEK‐rich phase and the T_g value shifted towards higher temperature due to the presence of compatibilizer, as suggested partial compatibility. Morphological investigations showed that the addition of RCP to binary blends reduced the dispersed phase size and improved the interfacial adhesion between the two phases. The ternary compatibilized blends showed enhanced tensile modulus compared to their binary blends without RCP. The strain at break decreased for the ternary blends due to embrittlement of the matrix by the incorporation of some RCP to the matrix phase. Copyright © 2007 John Wiley & Sons, Ltd.     

Positron annihilation and differential scanning calorimetry studies of polyacrylamide and poly(dimethylacrylamide)/poly(ethylene glycol) blends

Positron annihilation lifetime spectroscopy and differential scanning calorimetry (DSC) measurements were performed for blends of polyacrylamide (PAM) and poly(ethylene glycol) (PEG) and blends of poly(dimethylacrylamide) (PDMAM) and PEG. The samples were prepared by codissolution in a concentration range of 0–100 wt % PEG. The thermal behavior, characterized by DSC measurements, showed similar variations of the glass‐transition temperatures (T_g's) with the PEG concentration for the two systems. Pure PAM and PDMAM presented T_g's of 188 and 111 °C, respectively. A relatively small and nearly linearly decreasing T_g was observed for the two systems in the range of 20–80 wt % PEG. PEG crystals were present in all blend compositions, and no melting point depression was observed. The thermal results pointed to the partial miscibility of the blends. The degree of crystallinity of PEG increased with increasing PEG concentration for the PDMAM/PEG systems. The ortho‐positronium lifetime (τ₃) increased with increasing PEG concentration for both blends. However, the parameter of the ortho‐positronium formation probability (I₃) decreased with the PEG concentration. The product τI₃, which was proportional to the total free volume fraction, was approximately constant with the PEG concentration for PDMAM blends and increased with the PEG concentration for PAM systems. This result may be interpreted as a consequence of a more heterogeneous structure in PAM blends. Scanning electron microscopy micrographs of blends with 40 and 80 wt % PEG provided evidence of the regions associated with PEG crystallites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1493–1500, 2003