Polyarylate Research Articles

Compatibilizing effect of polyarylate-nylon 6 block copolymers on polyarylate/nylon 6 blends: 1. Synthesis of polyarylate-nylon 6 block copolymer and its miscibility in binary blends with polyarylate or nylon 6

Polyarylate (PAR)-nylon 6 block copolymers of various block lengths were prepared by the anionic polymerization of ε-caprolactam using the polymeric activator from hydroxy-difunctional PAR and toluene diisocyanate. Phase-separated morphology of PAR-nylon 6 block copolymer was observed by transmission electron microscopy and the thermal properties were measured by differential scanning calorimetry (d.s.c.). Partial miscibility between PAR and nylon 6 segments was more evident with shorter constituent blocks. In binary blends of PAR or nylon 6 with PAR-nylon 6 block copolymer, molecular-level mixing of homopolymers with corresponding blocks of block copolymer was supposed from the thermal properties measured by d.s.c.

各種ポリマーのブレンドによる酸素富化膜の製造

We studied permeation behavior for blended or laminated membrane of polydimethylsiloxane (PDMS), polyarylate (PAR), poly (4-methylpentene-1) (PMP) and 1, 2-polybutadiene (1, 2-PB).As a result shows, in blended system, separation factor of PAR /1, 2-PB system is a value of 4.80, and laminated system of PAR /1, 2-PB system is 5.51.In the case of laminated membranes, PDMS or 1, 2-PB laminating on the high strength film such as PAR and PMP, obtain significantly excellent separation membranes. These are because of progressing oxygen affinity of PDMS or 1, 2-PB on laminating film.

Cooperative relaxations in amorphous polymers studied by thermally stimulated current depolarization

Thermally stimulated current depolarization (t.s.c.) was used to study the relaxations in amorphous polymers including poly (ethyl methacrylate) (PEMA), poly (methyl methacrylate) (PMMA), polystyrene (PS), polycarbonate (PC) and polyarylate (PAR) over temperature ranges covering the β and α (glass transition) regions. A.c. dielectric was used to obtain activation energies ( E a) for PS and PC to verify the accuracy of those values determined by the t.s.c. thermal sampling method. At temperatures below the glass transition ( T g) the values of E a were found to agree with those predicted using an activated states equation with a zero activation entropy. This is evidence of the localized, non-cooperative nature of the low temperature secondary β relaxations which are found to be characterized by a continuous variation of activation energies as a function of temperature. The measured values of E a depart from the zero activation entropy curve and exhibit a prominent maximum at T g. This behaviour is known to be due to an enhanced degree of cooperativity of segmental relaxations near T g. The results indicate that the main advantage of the thermal sampling method is the high sensitivity and high temperature resolution for cooperative relaxations. For the polymers studied here, only PEMA and PMMA show a substantial population of cooperative relaxations more than 60°C below T g. This is tentatively explained in terms of structural heterogeneity due to variable tacticity in the methacrylates. Compensation of the t.s.c. relaxation spectra plotted in Arrhenius or Eyring plots was found for all polymers to differing degrees. Some discussion of compensation is made in terms of independently measured values of the coefficient of thermal expansion.

Orientation and Mechanical Property Development in the Melt Spinning of Fibers from Polyetherimide and Polyarylate

Abstract An experimental study of structure development in melt spinning polyetherimide (PEI) and polyarylate (PAR) is presented. PEI was melt spun at 320° and 350°C and PAR at 310° and 340°C to drawdown ratios of up to 1 000. The melt spun fibers were found to be totally amorphous but to have significant levels of birefringence which increased with draw-down ratio. The birefringence was found to vary linearly with the spinline stress for both polymers and the data was independent of the melt spinning temperature. The proportionality constants are interpretable as equivalent to stress optical constants for the corresponding melts and have values of 9 400 Brewsters for the PEI and 7 400 Brewsters for the polyarylate. The mechanical properties of the melt spun fibers were determined in uniaxial extension. It was found that Young's modulus and tensile strength increased with spinline stress or birefringence while elongation to break decreased. The mechanical properties were found to be similar to polyether ether ketone, poly-p-phenylene sulfide, and polyethylene terephthalate in similar correlations, but as compared to polypropylene at the same spinline stress had higher Young's modulus and tensile strength but lower elongation to break. We were not able to successfully draw these materials over a hot plate at temperatures above their glass transition temperature.

Hydrolytic Stability of Polyphenylene Sulfide/Polyarylate Blends

Abstract In the immiscible blends of poly(phenylene sulfide) (PPS) and polyarylate (PAR), absorbed moisture partitioned into each phase according to the equilibrium value of the homopolymers. The water diffusivity was observed to decrease with increasing PPS concentration and at >45%, when PPS became the major component in the skin region, the diffusivity was equal to that of neat PPS. The molecular weight of the PAR fraction was found to degrade linearly with time due to hydrolysis.

Poly(ethylene terephthalate)/polyarylate blends: Influence of interchange reactions on the melting behavior of poly(ethylene terephthalate)

AbstractThe influence of the interchange reactions of poly(ethylene terephthalate) (PET)/polyarylate (PAr) blends on the melting behavior of isothermally crystallized PET has been studied. PET shows three melting endotherms in the pure state and also when mixed with PAr. These endotherms are explained in terms of primary and secondary crystallization processes as well as recrystallization during the calorimetric scan. It is also shown that interchange reactions hinder the crystallization processes of PET.

Melt rheology of poly(ethylene terephthalate), polyarylate, and their blends

AbstractRheological properties of two polyesters; poly(ethylene terephthalate) (PET) and bisphenol A‐50/50 isophthalic/terephthalic acid based polyarylate (PAR), and their 85/15, 50/50, and 30/70 (PET/PAR) blends were investigated using a RDS rheometer, 290–310°C. Measurements included complex viscosity and modulus. Activation energy for flow and relaxation spectrum were subsequently calculated. Results indicated that PET/PAR blends are rheologically incompatible, i.e., zero‐shear viscosities of the blends showed a negative deviation from the averages of the two homopolymers with a sharp minimum at 85/15 composition. The relaxation spectrum for 85/15 blend also showed a relaxation plateau, a characteristic of rigid particle suspension. The morphology of the polymer blends was examined from cryogenically fractured and etched surface using a scanning electron microscopy (SEM). Morphological observation indicated that PAR‐rich phases, order of 0.1μm, were finely dispersed in PET phase for 85/15 blend, whereas the dispersion of PET phase in PAR‐rich phase was in spherical form, order of 0.5μm in diameter, for the 50/50 blend.

Polyarylate/polyamide 6 blends: A calorimetric study

A calorimetric study has been done of the miscibility of blends composed of polyarylate (PAr) and poly(e-caprolactam) (polyamide 6, nylon 6). The thermal transitions of blends subjected to two different thermal treatments have been determined. Two glass transitions have been observed in the blends irrespective of the thermal history. These glass transitions indicate the existence of two amorphous phases in the blends, a practically pure nylon phase and a mixed PAr/nylon 6 phase. The variation of the melting temperature of nylon with the blend composition is in good agreement with the existence of phase separation in the blends. However, the melting heat shows a slightly positive deviation from linearity when it is represented against the blend composition.

Polybenzimidazole (PBI) and polyarylate blends

The discovery of new polymeric alloys by blending commercially available polymers is an exciting trend in materials development. The ability to tailor existing materials to a new /unique set of property /performance /price specifications through combinations of materials is the key reason for this growth. Recently, various miscible blends based on Hoechst Celanese's polybenzimidazole ( PBI ) and commercially available polyimides (PI) were di~covered.'-~ Blend miscibility was evidenced in the form of changes in IR spectra, single Tg's, and well-defined single tan 6 relaxations. The intermolecular interaction involving the =NH and carbonyl groups was the major driving force for the miscibility. We therefore conducted a program focused on the fabrication of high-performance blend fibers based on PBI. After a thorough investigation, we found that PBI not only has superior thermal / chemical properties, but also exhibits unique reactivity that enables it to interact with other functionalized polar molecules and to possibly form compatible binary system^.^^^ As a result of PBIs reactivity, the molecular interactions between PBI and polyarylate ( PA) polymers have recently been discovered at Hoechst Celanese Research Division? In this paper we present information regarding the assessment of PBI/PA compatibility, the preparation /characterizations of solution and blend film, as well as the development of PBI/PA fibers.

Film and membrane properties of polybenzimidazole (PBI) and polyarylate alloys

AbstractBlends of a poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (FBI) polymer with polyarylate (PA) yield films exhibiting synergistic mechanical properties. The break strength of the blended materials exceeded the strength of the stronger polymer in its 100% form. The molecular interaction and compatibility of PBI/PA have been investigated and confirmed by infrared, dynamic mechanical analysis and thermogravimetric analysis. For example, interactions were typically found between the carbonyls and the imidazole in these systems, and there was a shift of the carbonyl band to lower frequency. DMA study of a (40/60) PBI/PA film blend revealed the existence of two Tg values (e.g., 245 and 362°C). The shift of the Tg from each individual component strongly suggested that FBI and PA interact on a molecular scale. Membranes made from a solution of a 60/40 (weight %) mixture of PBI and polyarylate exhibited excellent UF properties: a flux of 60–80 gfd at 50 psi and a rejection of 90–99% of cytochrome‐c (MW = 12,000). The HPLC results confirmed the red color species (Vitamin 12 and cytochrome‐c) were quantitatively removed. Further experiments indicated that the excellent UF properties were due to the novel combination of PBI and PA which offered a unique absorption and ionic‐exchange characteristics.

Phase morphology of as‐molded and annealed blends of polyarylate/copolyester

AbstractThe phase morphology of injection molded blends of polyarylate (PAR) and a copolyester (PCTG‐5445) was studied by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The use of ultramicrotomy to prepare ⋍ 50 nm thin section TEM specimens and solvent etching to dissolve the PAR phase revealed PCTG as the matrix phase in the as‐molded state which crystallized into PCTG spherulites upon annealing. The most consistent morphological information vs. concentration of PCTG and the highest structural integrity of the PCTG spherulites was obtained from thin sections treated with a mixture of 75% methylene chloride as the solvent for the PAR and 25% 2‐propanol as the nonreactive diluent. XRD results from the annealed PCTG/PAR blends show crystalline reflections of 0.59, 0.53, 0.46, 0.38, and 0.35 nm, which disappear into the amorphous background below 50% PCTG.

An apparent double glass transition of polyphenylene sulfide in blends with polyarylate

Injection molded blends of polyphenylene sulfide (PPS) and polyarylate (PAR) are phase separated as evidenced by transmission electron microscopy (TEM) micrographs and the existence of glass transition temperatures (Tg's) near 100 °C (PPS) and 190 °C (PAR). Upon annealing, blends that contain 15% to 40% by weight PPS exhibited unusual double glass transition temperatures (aside from PAR's Tg at 190 °C) at ca. 88 °C and 110 °C. These transitions coincide, respectively, with the Tg's of amorphous and crystalline PPS homopolymer. PPS crystallinity and average domain size distribution were found to be larger in the skin region than in the core region. It is believed that the double Tg's are brought about by different PPS domains with two types of amorphous material.

Solvent‐induced embrittlement in a crystallizable polyarylate

AbstractThe effects of solvent‐induced crystallization on the micromechanical properties of thin films of polyarylate (PAr) were studied. Under uniaxial extension amorphous polyarylate was observed to deform exclusively by shear deformation with no evidence of crazing. Upon exposure to methylethyl ketone, vapor, or liquid, PAr crystallizes and is subsequently embrittled. Our transmission electron microscopy results clearly show that this embrittlement results from a transition in plastic deformation mechanism from shear yielding to crazing. A detailed examination of the samples revealed that the crazes formed preferentially within the noncrystalline regions and that the craze tips followed a complex trajectory around the crystallites. In some cases the craze tip advance deviated by as much as ±30 from a direction normal to the tensile axis. Because crazes are inherently more susceptible to forming cracks than shear deformation zones, crystallization reduces the fracture toughness of the polymer. This type of embrittlement, via a transition in plastic deformation mechanism, is believed to be a general behavior for solvent‐crystallizable thermoplastics.

On Some Properties of Blends Based on Thermotropic Liquid Crystalline Polymers

An investigation of the flow, mechanical, tribological properties, such as tensile, bending, impact strengths, friction and wear rate was conducted for various blends of three polymers, namely, LCP (liquid crystalline polymer), PAR (polyarylate) and PA (polyamide).The results were summarized as follows;1) The tensile and bending strength of blends of LCP 25/75 PAR (LCP 25%, PAR 75%) was greater than that of neat PAR.2) The frictional coefficient and wear rate of blends of LCP 25/75 PAR and LCP 25/75 PA were smaller than that of neat LCP, neat PAR and neat PA.3) The dependence of frictional speed on the frictional coefficient and wear rate of blends approached to that of neat LCP with increasing of LCP content.

Degradation of aromatic polymers—I. Rates of crosslinking and chain scission during thermal degradation of several soluble aromatic polymers

Five kinds of aromatic polymers [polycarbonate(PC), polyarylate(PAR), polyetherimide(PEI), polysulfone(PSF), polyethersulfone(PESF)] were degraded at 380° in vacuum. The molecular weights and molecular weight distributions of degraded samples were measured by gel permeation chromatography, using dichloromethane as eluent. It was found that crosslinking takes place during degradation of each aromatic polymer studied; chain scission occurs simultaneously to a lesser extent. A novel simulation method, with theoretical calculation of molecular weights of the degraded sample, allowed evaluation of both the crosslinking rate and the chain scission rate. The crosslinking rate decreases in the order PEI > PAR > PC ⪢ PSF ⋍ PESF , and chain scission rate decreases in the order PC > PAR > PEI > PSF > PESF. It is suggested that the isopropylidene moiety and carbonate linkage increase the rate of chain scission, while the aryl sulfone moiety decreases the rate of radical reaction.

Phase morphology studies of polyarylate/copolyester blends by transmission electron microscopy (TEM) and x-ray diffraction (XRD)

Injection molded blends of polyarylate (PAR) (ARDEL D-100,AMOCO) and a copolyester (PCTG) (PCTG-5445, EASTMAN CHEMICALS) were found to be single phase and transparent. Upon annealing, above the glass transition temperature, but below the melt temperature of each blend, a single glass transition temperature remained but blends up to 50% PAR become opaque due to crystallization of the PCTG. These morphological changes with annealing have necessitated this study.Cross sections of blends containing 85%, 70%, 50% and 30% PCTG, annealed at l60°C-1h, l60°C-4h, l85°C-4h and l85°C-16h respectively, were prepared for TEM using an LKB Ultramicrotome III with diamond knife. Thin, approx. 50 nm sections, supported on carbon film substrates on TEM grids were examined, as sectioned, by bright field TEM (BF TEM), in a JEOL 2000FX TEM operated at 200 keV. Additional thin sections of each blend were examined by BF TEM and selected area electron diffraction (SAED) after they were treated with a solvent mixture (methylene chloride(MeCl)/dioxane(Diox)) to remove the amorphous fraction and reveal the crystalline portion of the PCTG.

Solvent‐induced crystallization of a compatible polymer blend

AbstractWe studied solvent‐induced crystallization (SINC) in a compatible blend of poly (butylene terephthalate) (PBT) and a polyarylate (PAr) over a range of blend compositions and temperatures; liquid acetone was the crystallizing agent. Acetone transport kinetics were followed by mass uptake measurements in thin films and by optical microscopy. Crystallization kinetics were followed by density measurements. For the 0.2 mm thick films used, those with higher weight fractions of PST (50 to 60 percent by weight) exhibit diffusion controlled transport and crystallization over the entire range of temperatures studied (0 to 55°C). Those with lower weight fractions of PBT (∼30 percent by weight) display Case II sorption and crystal growth controlled crystallization at 0°C. The latter is rare for SINC in homopolymers and results from a sharp reduction in the PBT crystallization rate in the presence of the noncrystallizable PAr.

Viscosity and relaxation times temperature behaviour above the glass transition in some glassy polymers

We have performed mechanical and dielectric dynamic measurements above the glass-transition temperature range of two glassy-polymers: Poly(Hydroxyether of Bisphenol-A) and Poly(Carbonate of Bisphenol-A). From these measurements the temperature dependence of mechanical and dielectric mean relaxation times has been calculated. Results obtained have been compared with the viscosity temperature behaviour of the same polymers, which has been reported elsewhere. Both, relaxation times and viscosity temperature behaviour can well be described by Doolittle functional forms, exp{1/[αf(T-To)]}, with the same values of To but different values of the apparent free-volume expansion coefficient, αf. This difference in the experimental behaviour has been addresed in the framework of the free-volume model ideas. In this context, the different values of αf obtained from viscosity and relaxation times temperature behaviour can be understood assuming different values of critical volume controlling the molecular motions associated to viscosity and relaxation processes. Similar conclusions have also been obtained by means of a fine revision of the viscosity and relaxation times data of another two glassy-polymers: Poly(Arylate) and Poly(Sulfone of Bisphenol-A), reported previously.

Ester exchange reactions in polyarylate/poly(ethylene terephthalate) blends

Blends coagulated by a solution/precipitation procedure of a polyarylate (PAr) based on bisphenol A and tere/isophthalates with poly(ethylene terephthalate) (PET) have been studied by a variety of experimental methods. Differential scanning calorimetry experiments have shown that in blends containing more than 30% PET, conditioning of the blends at high temperatures required for calorimetric measurements resulted in progressive ester exchange reactions. The 10% and 20% PET mixtures, in which this extreme conditioning was not required, showed a single glass transition, contrary to the behaviour of the other PET compositions. These differences may be attributed to the shape of the spinodal curve, which has been simulated according to the McMaster model for polymer mixtures. The progression of the interchange reactions has been followed by solvent extraction of the resulting products and subsequent Fourier transform infra-red spectroscopy analysis. A parallel decrease in the PET heat and temperature of fusion in the insoluble fractions was observed. In our opinion this was due to the incorporation of PAr units in the PET chains, which caused a decrease in their crystallizable segment length.

Ternary polymer mixtures: Polyarylate/phenoxy/poly(butylene terephthalate)

AbstractThe intended objective of this work was to bring together two immiscible polymers, polyarylate (PAr) and Phenoxy [poly(hydroxy ether of bisphenol‐A)], preparing ternary mixtures with a third component, poly(butylene terephthalate) (PBT). Experimental results showed that ternary mixtures containing 30% or more PBT gave single glass transition temperatures by DSC. Moreover, the PBT melting point depended on the composition of the mixtures. These results, which could be indicative of the existence of a single amorphous phase in these blends, have been discussed. Nevertheless, results must be considered with caution, given the peculiarities of the Tg–composition diagrams for the miscible pairs PAr/PBT and Phenoxy/PBT. Hypothetic interchange reactions during melting have been found to be unimportant.