Transport properties of poly(ethylene terephthalate)/Rodrun 3000 blends

The transport properties of incompatible blends of poly(ethylene terephthalate) (PET) and a thermotropic liquid crystalline polymer (TLCP) composed of 40 mol% of PET and 60 mol% of p-hydroxybenzoic acid (Rodrun 3000) have been investigated using dichloromethane as permeant. Films, obtained by a blown film extrusion process, were analyzed and compared with the same samples stored 2 and 15 days at 60°C. With respect to the as-blown films, blends submitted to physical aging show a decrease in permeability by a percentage that increases with the amount of the LC phase present and a larger contribution derived from the polymeric matrix. The decrease of permeability is essentially attributed to a lowering of sorption because diffusional behavior for the different samples is the same.     

Basic aspects of microindentation in multilayered poly(ethylene terephthalate)/polycarbonate films

The microhardness H of multilayered poly(ethylene terephthalate) (PET)/polycarbonate (PC) films, produced by continuous layer multiplying coextrusion has been determined. These materials present rather uniform laminates up to thousands of layers in the micrometre and submicrometre range. The micromechanical properties have been investigated as a function of layer thickness of the single polymer components, the total number of layers, the film thickness and the influence of heat treatment. The microhardness of the microlayered structure has also been determined across the profile in the parallel direction to the packing of the layers. The hardness in the vicinity of the PET/PC phases has been examined. Results reveal that the influence of the interphase on the H values for the samples with a large number of layers is rather small. The most important parameter in determining the final hardness of the multilayered films is the ratio of the penetration depth to the thickness of the layer. Upon heating, a microhardness increase is observed as a consequence of a double contribution: the crystallization of the PET layers, on the one hand, and the physical ageing of the PC zones on the other.     

Confined crystallization in phase-separated poly(ethylene terephthalate)/poly(ethylene naphthalene 2,6-dicarboxilate) blends

The isothermal cold crystallization of poly(ethylene terephthalate)(PET) in cryogenic mechanical alloyed blends of PET and Poly(ethylene naphthalene 2,6-dicarboxilate)(PEN) 1:1 by weight has been investigated by simultaneous small and wide angle X-ray scattering (SAXS and WAXS) and dielectric spectroscopy (DS). For transesterification levels higher than 23% the blends tend to transform into a one-phase system and the crystallization of PET is strongly inhibited due to the significant reduction of the PET segment length. For lower levels of transesterification the blends are phase separated and the overall crystallization behaviour can be explained considering the confined nature of the PET domains in these blends. The formation of a rigid amorphous phase in the intra-lamellar stack amorphous regions is reduced in the blends due to a lower probability of stack formation in the confined PET-rich domains. The more effective filling of the space by the lamellar crystals in the blends provokes a stronger restriction to the amorphous phase mobility of PET in the blends than in pure PET.     

Rheological,thermal, and mechanical properties of poly(ethylene naphthalate)/poly(ethylene terephthalate) blends

Structural, Theological, thermal, and mechanical properties of blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) obtained by melt blending were investigated using capillary rheometry, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) observation, tensile testing. X-ray diffraction, and ¹H nuclear magnetic resonance (NMR) measurements. The melt Theological behavior of the PEN/PET blends was very similar to that of the two parent polymers. The melt viscosity of the blends was between that of PEN and that of PET. Thermal properties and NMR measurement of the blends revealed that PEN is partially miscible with PET in the as molded blends, indicating that an interchange reaction occurs to some extent on melt processing. The blend of 50/50 PEN/PET was more difficult to crystallize compared with blends of other PEN/PET ratios. The blends, once melted during DSC measurements, almost never showed cold crystallization and subsequent melting and definitely exhibited a single glass transition temperature between those of PEN and PET during a reheating run. Improvement of the miscibility between PEN and PET with melting is mostly due to an increase in transesterification. The tensile modulus of the PEN/PET blend strands had a low value, reflecting amorphous structures of the blends, while tensile strength at the yield point increased linearly with increasing PEN content.     

Calorimetric study of polyethylene terephthalate)/poly(butylene terephthalate) blends

Poly(ethylene terephthalate)/poly(butylene terephthalate) blends [xPET/(l-x)PBT] were prepared by ultraquenching of the melt between two metal rolls rotating in a liquid nitrogen bath. Both DSC and WAXS studies indicate that immediately after preparation, the blends are amorphous regardless of the composition. Two glass transition temperatures are found for the as-quenched 0.5 PET/0.5 PBT blend. The activation energies determined from the dependence of each glass transition temperature on the heating rate are approximately the same. Furthermore, they are equal to the mean activation energy for the overall crystallization. This can be explained in terms of the percolation threshold theory.     

Aromatic poly(ester carbonate)/poly-(ethylene terephthalate) alloys

When mixtures of poly(ester carbonate) (PEC) and poly(ethylene terephthalate) (PET) containing up to two-thirds of the latter are melt extruded, they produce a single-phase amorphous “alloy.” This alloy is characterized by a sharp, single, composition-dependent glass transition temperature, T_g. When annealed below T_g, the alloy remains unaltered, but when annealed above its T_g, the alloy separates into minute pure-PET crystallites and an amorphous PEC/PET phase. The thermal and dynamic mechanical behavior, crystallization kinetics, and SAXS patterns all strongly suggest the PEC-rich alloys to be solid solutions in which the PET molecules are dispersed individually or in small aggregates containing only a few PET molecules each. Calculations of the interaction parameter and assumed interfacial layer thickness tend to support this suggestion. Use of appropriate solvents allows one to selectively dissolve the PEC and recover from the alloys both PET and PEC in the original purity and molecular weights. Diffusion constants of PET molecules through the amorphous alloys were obtained from studies of PET crystallization above T_g of the alloys. The magnitude of the constants are in the range of expectation. The mechanical properties of the amorphous alloys in the glassy state do not deviate greatly from simple additivity of the respective properties of the parent polymers. However, the melt viscosity of the PEC-rich alloys and their plateau modulus above T show drastic decreases from straight additivity. A qualitative, but not quantitative, explanation of these observations is offered.     

Molecular dynamics of poly(ethylene terephthalate)/poly(phenylene sulfide) nanocomposites with barium titanate

The relaxation processes and the properties of polymer/ceramic nanocomposites have been studied by the ¹H nuclear magnetic resonance methods. Nanocomposites of poly(ethylene terephthalate) PET and poly(phenylene sulfide) PPS with 0.25, 2.5 and 5% wt. barium titanate BT were prepared using a twin screw extruder and injection moulding machine. The spin-lattice relaxation time T₁, second moment M₂ and the motional parameters as e.g. the activation energies in the nanocomposites were investigated.     

The compatibility and transesterification for blends of polyethylene terephthalate)/poly(bisphenol-A carbonate)

A study has been made of the influence of transesterification on the miscibility in binary blends of poly(ethylene terephthalate) and poly(bisphenol-A carbonate). The blends were melt mixed in the range 260–300°C and studied by differential scanning calorimetry, dynamic mechanic analysis, and by Fourier transform infrared spectrometry. It was found that copolymer produced by a transesterification reaction can enhance the miscibility of this system. The new compositions were uniquely identified by FTIR. Gel permeation chromatography showed that molecular weight decreases were not the origin of miscibility. The ester exchange reaction itself was found to be initiated by the residual catalyst in the commercial polymers selected for study. This has been shown by the absence of reaction after polymer purification by solution and reprecipitation prior to melt mixing.     

Glass transition of poly(ethylene terephthalate)

It has been found that commercial poly(ethylene terephthalate) film exhibits current glow curves which have maxima at 73.5 ± 3.4°C and at 105.3 ± 3.4°C. These current glow curves were obtained by measuring the current flowing under zero bias as the temperature was raised 1°C/min. A typical curve, for untreated 1-mil du Pont Mylar A, is seen in Fig. 1. Although a paper on this study will shortly be submitted for publication, some conclusions of that paper may be stated here.     

Direct-current conductivity of poly(ethylene terephthalate)

There have been several previous studies of the dc conductivity of poly(ethylene terephthalate). Disagreement among the various authors indicates the difficulties inherent in this measurement: several authors [1,2] found evidence for ionic conduction through a hopping process; others [3,4] proposed conduction by electrons injected through a barrier.     

Electron induced modification in poly(ethylene terephthalate)

Abstract

The effect of 100 kGy dose of 2 MeV electron irradiation on Poly(ethylene terepthalate) (PET) has been studied by different characterisation techniques such as the Fourier transformed IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction analysis. Oxidative degradation leading to amorphisation of the polymer has been observed from spectral analysis. The thermal stability of the polymer was found to decrease due to electron irradiation. The thermal decomposition temperature as well as the melting temperature in case of irradiated PET was found to be decreased due to electron bombardment. A decrease in crystallinity of the polymer has also been observed after irradiation.     

Superstructure in chemically etched poly(ethylene terephthalate)

The new technique of contact etching has been utilized to study the bulk morphology of polyethylene terephthalate by the echant, n-propylamine. A variety of films and fibers with different mechanical and thermal histories have been subjected to contact etching. The sample surfaces have been studied principally by scanning electron microscopy. A network superstructure with its characteristic dimension (thickness) of from 700 to 3000 Å, depending on sample history, has been observed. In the oriented samples the network superstructure aligns perpendicular to the direction of sample orientation. A simple model is proposed to describe the network superstructure which is believed to be moderately crystalline.     

Antistatic performance and morphological observation of ternary blends of poly(ethylene terephthalate), poly(ether esteramide), and Na-neutralized poly(ethylene-co-methacrylic acid) copolymers

Blends of poly(ethylene terephthalate) (PET) and poly(ether esteramide) (PEEA), which is known as an ion conductive polymer, were prepared by melt mixing using a twin screw extruder. Antistatic performance of the molded plaques of the binary blends was investigated and the effects of adding sodium ionomer, Na-neutralized poly(ethylene-co-methacrylic acid) (E/MAA) Copolymers, in comparison with NaI, were also investigated. We found Na-neutralized E/MAA significantly improved static dissipation performance when blended with above PET/PEEA system whereas NaI was only effective when PEEA amount was larger than 25 wt%. Morphological study of these ternary blends system was conducted by using TEM and it was observed that PEEA domain formed platelet structure in PET matrix when PEEA content was 30%. The domain shape changed from sphere particle to platelet structure via string shape with the increase of PEEA content. And the thickness of the PEEA layers was confirmed as thin as 10 nm. Specific interaction between PEEA and Na-neutralized E/MAA was found by TEM. The Na-neutralized E/MAA domain was encapsulated by PEEA, which could increase the surface area of PEEA in PET matrix. This encapsulation effect explains the unexpected synergy for the static dissipation performance on addition of Na-neutralized E/MAA to PET/PEEA blends.     

Preparation and Properties of Poly(ethylene terephthalate)/Silica Nanocomposites

A kind of poly(ethylene terephthalate) (PET)/Silica nanocomposite (PETS) was synthesized via in situ polymerization using the compatibility between silica nanoparticles and ethylene glycol (EG). Transmission electron microscopy (TEM) micrographs revealed that the silica nanoparticles were well dispersed in the PET matrix, the particle size was about 10 nm with narrow distribution, and there existed strong interaction between the particles and the polymer chains. Differential scanning calorimetry (DSC) results indicated that the thermal properties of PETS with 2 wt% silica (PETS‐2) are different from those of pure PET (PETS‐0). The properties of the as‐spun fibers show that the tenacity and LASE‐5 (load at a specified elongation of 5%) of PETS‐2 were higher than those of PETS‐0, while the heat shrinkage of PETS‐2 was lower than that of PETS‐0. We suggest that the increasing of crystallinity and the strong interface interaction of the nanocomposite caused the fibers of PETS‐2 to not only have higher tenacity and LASE‐5 but also to have lower heat shrinkage.     

Structural changes in glassy poly(ethylene terephthalate)

Structural changes in glassy poly(ethylene terephtbalate) and their effects on its crystallization, melting, and various properties were studied. Quenched, annealed below T_g, crystallized, and drawn samples were studied using calorimetry, wide-and small-angle X-ray diffraction, mechanical spectroscopy, and stress-strain analysis. All results indicate some level of order in the glassy polymer which can be increased by annealing below T_g. This order still exists at tempertures above T_g and affects the properties of the polymer.     

Synthesis of ultrahigh molecular weight poly(ethylene terephthalate)

Poly(ethylene terephthalate) of number-average molecular weight of the order of 120,000 was prepared from commercial-grade material in the solid state with a gas chromatograph apparatus. Parameters studied were the catalyst, particle size, the molecular weight of the starting material, the reaction temperature and time, and the nature and flow rate of the carrier gas.     

Angle dependent laser nanopatterning of poly(ethylene terephthalate) surfaces

Interference effects can lead to the formation of ripple structures at laser-irradiated poly(ethylene terephthalate) surfaces. Poly(ethylene terephthalate) surface was irradiated with linearly polarized light of a pulsed 157 nm laser. In a certain range of irradiation parameters, the irradiation resulted in the formation of coherent ripples patterns. The dimension of the pattern depends on the angle of the laser beam incidence. The surface morphology of the nano-patterned poly(ethylene terephthalate) was analyzed by atomic force microscopy and focused ion beam-scanning electron microscopy. Oxygen concentration in the modified polymer surface was studied by angular resolved X-ray induced photo-electron spectroscopy. Gold nano-layers were consecutively sputtered onto the laser irradiated poly(ethylene terephthalate) surfaces. The morphology of the sputtered gold nano-layers was investigated with atomic force microscopy too. We found that the morphology of the gold nano-layers changes and depends on the surface pattern of the laser irradiated poly(ethylene terephthalate). Formation of gold “nano-hills” is observed at the ridges of the ripple structures. The amount of oxygen together with the morphology of prepared polymer pattern may be the dominant factors controlling the gold layer growth. The present results are compared with those obtained earlier on PET irradiated with krypton fluoride laser.     

Electron beam induced modification of poly(ethylene terephthalate) films

Electron beam processing of poly(ethylene terephthalate) (PET) films is found to promote significant changes in the melting heat, intrinsic viscosity and polymer film-liquid (water, isooctane and toluene) boundary surface tension. These properties are featured with several maximums depending on the absorbed dose and correlating with the modification of PET surface functionality. Studies using adsorption of acid-base indicators and IR-spectroscopy revealed that the increase of PET surface hydrophilicity is determined by the oxidation of methylene and methyne groups. Electron beam treatment of PET films on the surface of N-vinylpyrrolidone aqueous solution provided graft copolymerization with this comonomer at optimum process parameters (energy 700 keV, current 1 mA, absorbed dose 50 kGy).     

Poly(butylene terephthalate)/phenoxy blends: Synergistic behavior in mechanical properties

The mechanical properties of miscible poly(butylene terephthalate) (PBT)/poly (hydroxy ether of bisphenol A) (phenoxy) blends obtained by melt mixing have been studied by means of the tensile test. The crystallinity of the blends has been studied by means of DSC and density measurements. A synergistic behavior, principally in the break properties, at high PBT contents in the blends is observed. As can be seen from the torque and density data, this synergistic behavior is related with the high level of miscibility which seems to exist at high PBT contents compared with that of the high phenoxy content region.     

Radiothermoluminescence of poly(tetra fluoroethylene) and poly(ethylene terephthalate) pretreated by xenon ions

Low-temperature (77–300 K) RadioThermoLuminescence (RTL) investigations of Poly(Tetra FluoroEthylene) (PTFE) and Poly(Ethylene TerePhthalate) (PET) foils previously treated by different flux (Φ = 10⁶–10¹¹ cm⁻²) of Xenon ions with energy 1.1 MeV/nucleon have been showed an essential ion-induced changes in RTL of the both polymers under study. In PET as well as in PTFE significant changes of RTL light yield observed at the ion flux more than 10⁹ cm⁻². Variation of RTL light yield in PTFE accompanied by appearance of new TL temperature maxima on the glow curve. An existence of correlation between observed changes of molecular mobility in ion-irradiated polymer and optical (PET) and strength (PTFE) properties have been found.