Interfacial tension of poly(p-phenylene sulfide) with other polymer melts

The interfacial tension of poly(p-phenylene sulfide) (PPS) with various thermoplastics of different compostion and polarity has been carried out using the breaking thread and pendent drop methods. The value of the polyethylene (PE)/PPS interfacial tension is found to be intermediate between PE/polysulfone and PE/polycarbonate. The highest interfacial tension for PPS found in the systems studied was with polyamide-6 followed by PE. The lowest values were with polysulfone followed by polystyrene. The effects of small additions of polysulfone and polystyrene in PPS on interfacial tension is studied with various thermoplastics. © 1994 John Wiley & Sons, Inc.     

聚苯硫醚热氧化处理研究

研究了聚苯硫醚在空气环境下经过热处理的合成化学改性.采用高温凝胶渗透色谱、光电子能谱、热失重、红外光谱和高压毛细管流变技术对聚苯硫醚进行表征.结果表明:低相对分子质量的聚苯硫醚和高相对分子质量的聚苯硫醚经过热处理,相对分子质量都会大幅提高;聚苯硫醚经过热处理过程会同时发生氧化反应、氧化交联反应、热交联反应和链增长反应.     

Electronic structure of poly(p-phenylene sulfide)

The electronic structure of poly(p-phenylene sulfide) (PPS) was studied through steady state photocurrent spectra and temperature dependence of dark conductivity for undoped film, by changes in the in situ optical absorption and ESR spectra under photoirradiation, and optical absorption spectra for doped film. The charge carriers in the undoped state are electronic since the photoconductivity is large and the kink point in the temperature dependence of dark conductivity is higher than the glass transition temperature. A sharp peak near the absorption edge in the photocurrent spectrum of undoped PPS is caused by the diffusion of photocarriers in a sheet with high surface recombination under conditions of low applied field. The in situ optical absorption and ESR spectra of SO₃-doped PPS were similar to those of di-p-tolyl sulfide (a monomer unit of PPS) and the formation of sulfur-centered radical cations was suggested rather than bipolaron states. The stable conduction of SO₃-doped PPS after exposure to atmosphere was analyzed by the classical Lorentz model and the existence of nearly free carriers within subchains was suggested. Their conductivity and mobility were estimated to be 2 S/cm and 3.6 cm²/Vs, respectively. Inter-chain conduction appears to be very low.     

Surface modification and bonding of poly(p-phenylene sulfide)

It is demonstrated that both chemical oxidation, e.g. by using acetic acid/hydrogen peroxide or chromosulfuric acid, and plasma treatment of poly(p-phenylene sulfide) (PPS) surfaces introduce polar groups. The changes of the surface chemistry are detected by FTIR spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. The increased polarity is partially responsible for better adhesion as verified by lap shear measurements using acrylic adhesive. Another important contribution to the improved adhesion originates from increased surface roughness after surface modification as measured by atomic force microscopy. This effect is very pronounced for PPS surfaces treated with chromosulfuric acid.     

A thermoanalytical study on solid-state cure of poly(p-phenylene sulfide)

Differential scanning calorimetry (DSC) was used to investigate the solid-state cure process of poly(phenylene sulfide)(PPS) resin. Virgin PPS resin in an open sample pan was cured in DSC cell. Either air or oxygen was used as a curing atmosphere. Cure temperatures were in the range of 200 and 250 °C, which are below the melting point of PPS resin. Cure temperature as well as atmospheric condition influenced the cure behavior of PPS in the solid state. Both the rate and the amount of cure increased with increasing cure temperature. On the other hand, the time to reach the maximum cure rate was independent of cure temperature. Changing the atmosphere from air to oxygen increased both the cure rate and the amount of cure. The size effect of PPS particles on the cure reaction was also discussed.     

Electron microscopy of high pressure crystallised poly (p-phenylene sulfide)

Abstract

High pressure crystallised poly (p-phenylene sulfide) (PPS) samples were investigated with wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The striation appearance, which is the most common feature of polymer extended chain crystals, was clearly observed. Poly (p-phenylene sulfide) extended chain crystals with a C-axis thickness around 10 μm were formed at high pressure. The DSC results showed that the melting temperature of high pressure crystallised PPS samples was up to 332·3°C, which was higher than the values of ideal PPS perfect crystals used by some researchers. Other morphologies formed at high pressure, including crystalbars and regular polygonal crystals of different characteristics, were also presented with the SEM measurements. The obtained PPS extended chain crystals may be used in the re-evaluation of certain parameters crucial to the processing of PPS products such as the equilibrium melting point and melting enthalpy of ideal crystal.     

Electrical conductivity of plasma-treated poly(p-phenylene sulfide) doped with iodine

Plasma treatment of poly(p-phenylene sulfide) (PPS) doped with I₂ is found to increase both the electrical conductivity and the stability of the material. The average conductivity of plasma-treated samples reaches an apparently saturated value of 1.7 × 10^?3s cm^?1, which is about six orders of magnitude higher than that of the same material without plasma treatment, and this conductivity remains practically unchanged under exposure to ambient environment for 10 days. Infrared and secondary ion mass spectra of the samples before and after plasma treatment suggest that the charge-transfer complexes are formed in PPS doped with I₂ after plasma treatment. This is also consistent with the temperature dependence of conductivity results which show that the activation energy for electrical conduction decreases from 2.0 eV for pure PPS to 0.2 eV for plasma-treated I₂-doped PPS. Using isothermal potential and current decay techniques, we have also measured the trap density distribution. Plasma treatment, on the one hand, does create more traps in PPS, but, on the other hand, it enhances conductivity. The mechanism of electrical conduction is briefly discussed.     

Thermal degradation of poly(phenylene sulfide) and perfluoropoly(phenylene sulfide)

The thermal and oxidative degradation of poly(phenylene sulfide) and perfluoropoly(phenylene sulfide) have been studied by a weight-loss method. The products of breakdown in vacuum have also been analyzed. The poly(phenylene sulfide) is more thermally stable in inert and oxidizing atmospheres than the fully fluorinated analog. The breakdown products can be accounted for by chain scission and transfer reactions. The formation of a large proportion of residue implies that crosslinking reactions play an important part in the degradation.     

Synthesis and characterization of poly(p-phenylene sulfide sulfone/ketone) copolymer

Summary High molecular weight poly(phenylene sulfide sulfone/phenylene sulfide ketone) copolymer was synthesized by the step polycondensation of sodium sulfide (Na₂S·xH₂O) with 4,4^′-dichlorobenosulfone (DCDPS), 4,4^′-difldibenzophenone (DFBP) between 180∼202 °C at normal pressure. The copolymer was characterized by FT-IR spectrum, UV spectrum, ¹H-NMR spectrum, X-ray diffraction and small angle light scattering (SALS), DSC and TGA. The more ketone in the copolymer chain, the better thermal properties of the PPSS/Ks resins have. The copolymer was found to be amorphous but has little local ordering structures with the content of ketone in the range of 0∼45% which is different from other high pressure polymerization.     

Oxidative degradation of poly(ethylene sulfide)

Poly(ethylene sulfide) which is a strong, stiff, solvent-resistant thermoplastic resin, upon preparation and molding, undergoes rapid degradation upon aging in air with significant loss in impact strength and other physical properties. This is attributed to surface crazing and shrinking caused by molecular breakdown and crystallization. Infrared spectral studies show the rapid formation of sulfoxide, sulfone, and carbonyl moities in the polymer and mass spectral analysis shows the principal gaseous degradation products to be acetaldehyde, carbon dioxide, sulfur dioxide, and water. The addition of antioxidants, blending with other resins, and polymer modification give only minor improvement in oxidation resistance. This poor oxidation resistance has prohibited the development of poly(ethylene sulfide) as a commercial thermoplastic.     

Cationic degradation of poly (cyclohexene sulfide)

Summary The polymerization of cyclohexene sulfide initiated by triethyloxonium tetrafluoroborate is quantitative in a few minutes (at 0°C) but is followed by a complete degradation of the polymer to cyclic tetramer and an equimolar mixture of a 1,2,5-trithiepane derivative and cyclohexene. Also poly(cyclohexene sulfide), obtained by coordinative polymerization, degrades to the same compounds when it is treated with a trace of triethyloxonium tetrafluoroborate. The active species for the polymerization as well as for the degradation is believed to be the thiiranium ion. A revised mechanism for the trithiepane formation is proposed.     

Phase morphology and mechanical properties of blends of poly(p-phenylene sulfide) and polyamides

An experimental study of the blending, thermal transitions, phase morphology, and mechanical properties of poly(p-phenylene sulfide) (PPS)/polyamide blends is presented. Nylon-6, rubber modified nylon-6, nylon-66, nylon-11, nylon-12, and two partially aromatic amorphous polyamides were included in the study. Generally, blends of PPS with aromatic amorphous polyamides exhibit better mechanical properties than those with aliphatic polyamides. The blends with nylon-12 exhibit the best characteristics among the aliphatic polyamides.     

Synthesis and characterization of poly(phenylene sulfide). I. Studies on the synthesis and the property differences of poly(phenylene sulfide) with terminal chloro groups and poly(phenylene sulfide) with terminal thiohydroxy groups

In this article, two kinds of poly(phenylene sulfide) (PPS) with terminal groups predominated by chloro and thiohydroxy groups have been synthesized using endcapping by adding monomer. Compared with PPS with terminal thiohydroxy groups, PPS with terminal chloro groups possesses a greater crystallinity, larger crystallite dimensions, a larger particle size, higher thermal stability, and a longer gelation time. © 1993 John Wiley & Sons, Inc.     

Characteristics of binary and ternary blends of poly (p-phenylene sulfide) with poly(bis phenol A) sulfone and polyetherimide

An experimental study of the phase morphology and mechanical properties of binary blends of poly(p-phenylene sulfide) (PPS) with both polyetherimide (PEI) and poly(bis phenol A) sulfone (PSF) is described. We also study the ternary system PPS-PEI-PSF. Differential scanning calirometry indicated the blends are immiscible; these findings were confirmed by scanning electron microscopy. Both PEI and PSF were found capable of improving the impact strength and elongation-to-break characteristics of PPS in binary blends and ternary systems.     

Crystallization kinetics and nucleating agents for enhancing the crystallization of poly(p-phenylene sulfide)

An experimental study of crystallization kinetics and the influence of nucleating agents on the solidification of poly(p-phenylene sulfide) (PPS) is described. The effect of molecular weight is considered by investigating PPS samples having different viscosity levels. We studied the effect of a range of nucleating agents including aluminum oxide, calcium oxide, silicon dioxide, titanium dioxide, kaolin, and talc. All of these compounds were found to enhance the rate of crystallization; in particular, silicon dioxide, kaolin, and talc were the most effective nucleating agents. An effort to study particle size effects of the silicon dioxide showed that the nucleation was very sensitive to the source of the material. These studies did, however, show that nucleation rates tended to increase with decreasing particle size and increasing loading of silicon dioxide. Comparison of PPS crystallization rates with those of other polymers indicates that it crystallizes much more slowly than polyethylene or isotactic polypropylene and is slower than polyetherether-ketone, when comparisons are made on an equivalent basis. PPS crystallizes at similar rates to polyethylene terephthalate (PET). However, our nucleated PPS does not crystallize as rapidly as nucleated PET.     

Electronic processes in poly(p-phenylene) and related compounds I. Paramagnetic and electrical properties of doped poly(p-phenylene)

Poly(p-phenylene) (PPP) was prepared by polymerization of benzene and was exactly purified from oligomers and the catalyst. IR spectra of the resulting material indicated only para substitution and a DP about 20. PPP is a polycrystalline substance with a small degree of crystallinity and is thermally resistant up to 798 K. The annealing of pristine polymer produced a material with higher crystallinity and crystallite size. In our investigations we examined the electrical properties of doped (AlCl₃) and undoped PPP at different temperatures. The mechanism of conductivity is explained assuming the existence of the Schottky barriers between polycrystalline grains and intergrain regions. The WAXS and ESR data are compared with the electrical results.     

The crystallinity of poly(phenylene sulfide) and its effect on polymer properties

The crystallinity and crystallizability of poly(phenylene sulfide) have been examined by a number of common techniques. Several provided qualitative information, but only one, x-ray diffraction, was considered sufficiently reliable and reproducible to allow quantitative comparisons. Based on x-ray measurements, an approximate degree of crystallinity, termed crystallinity index (C_i), could be readily assigned. According to this method, virgin polymer possesses significant crystallinity (C_i ≈ 65%). Curing (crosslinking) the resin below its melting point did not change the crystallinity but did affect the crystallizability. Lightly cured resin suitable for molding and film extrusion was easily quenched from the melt to give amorphous polymer. The amorphous samples crystallized rapidly when heated to temperatures > 121°C (250°F). At mold temperatures below 93°C (200°F), moldings with very low surface crystallinity were produced. Annealing (204°C, 400°F) caused rapid crystallization of such moldings, and changes in crystallinity were correlated with observed changes in physical properties. The resin crystallizes so rapidly that these quenched moldings possessed a crystallinity gradient, the internal crystallinity being substantially greater. At high mold temperatures (121–204°C, 250–400°F), moldings very similar to fully annealed specimens were obtained.     

A kinetic analysis on thermal degradation of poly(phenylene sulfide ether)

Thermal degradation of poly(phenylene sulfide ether) (PPSE) was investigated by using thermogravimetry (TG) under air and nitrogen atmosphere. It was found that the existence of oxygen depressed the thermal stability of PPSE and changed the mechanism of thermal degradation. The influences of molecular weight and heating rate on the decomposition of PPSE were also investigated under N₂ atmosphere. The results showed that the thermal stability of PPSE was excellent and can be further enhanced by increasing molecular weight. A simple kinetic model concerning two parallel reactions in overall temperature range was proposed to describe the thermal degradation process of PPSE in nitrogen. Kinetic analysis of the dynamic TG curves for PPSE was carried out by using Kissinger, Flynn–Wall–Ozawa, and Coats–Redfern methods. The kinetics of PPSE degradation displayed that the two parallel reactions were in accordance with the first‐order equation. The kinetic model was further validated by comparing the experimental and calculated results. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009