Crystallization Of PPS Research Articles

Effect of high-performance polymers on crystallization and multiple melting behavior of poly(phenylene sulfide)

The crystallization and multiple melting behavior of poly(phenylene sulfide) (PPS) and its blends with amorphous thermoplastic bisphenol A polysulfone (PSF) and phenolphthalein poly(ether ketone) (PEK-C), crystalline thermoplastic poly(ether ether ketone) (PEEK), and thermosetting bismaleimide (BMI) resin were investigated by a differential scanning calorimeter (DSC). The addition of PSF and PEK-C was found to have no influence on the crystallization temperature (Tc) and heat of crystallization (ΔHc) of PPS. A significant increase in the value of Tc and the intensity of the Tc peak of PPS was observed and the crystallization of PPS can be accelerated in the presence of the PEEK component. An increase in the Tc of PPS can also be accelerated in the BMI/PPS blend, but was no more significant than that in the PEEK/PPS blend. The Tc of PPS in the PEEK/PPS blends is dependent on the maximum temperature of the heating scans and can be divided into three temperature regions. The addition of a second component has no influence on the formation of a multiple melting peak. The double melting peaks can also be observed when PPS and its blends are crystallized dynamically from the molten state. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 637–644, 1998

Poly(phenylene sulfide)/liquid crystalline polymer blends: 1. Non-isothermal crystallization kinetics

The non-isothermal crystallization behaviour of poly(phenylene sulfide) (PPS) in blends with thermotropic liquid crystalline polymer (TLCP) was studied by means of differential scanning calorimetry. The TLCP chosen for the investigation was poly(oxybenzoate- co-ethylene terephthalate). It was observed that the Ozawa equation is valid not only for neat PPS, but also for the blends. The PPS crystallization temperature was found to increase markedly upon addition of the TLCP. A notable reduction in Avrami exponents for the PPS/LCP blend systems suggests that the nucleated process leads to rod-shaped growth with thermal nucleation. The cooling crystallization function, which represents the rate of non-isothermal crystallization, was found to decrease with decreasing temperature and/or increase in LCP content. It has been concluded that the non-isothermal crystallization of PPS is strongly accelerated by the presence of TLCP.

A study on the ternary blends of polyphenylenesulfide, polysulfone, and liquid crystalline polyesteramide

AbstractTernary blends of poly(p‐phenylenesulfide) (PPS), thermotropic liquid crystalline polyesteramide (LCP), and polysulfone (PSF) were investigated in terms of processing characteristics, blend morphology, and physical properties. In the incompatible PPS/LCP blends, LCP imparted a nucleating effect to the crystallization of PPS. Up to 10wt% LCP content, the tensile properties of PPS/LCP blends were enhanced with increasing LCP content, but they deteriorated if the LCP content exceeded 20wt%. Addition of a third component, PSF, to the 90/10 PPS/LCP blend promoted development of rodlike or threadlike fibrillar structure and orientation of the deformed LCP domains, which led to improvement of tensile strength up to 20%.

Infrared spectroscopic analysis of poly( p-phenylene sulfide)

Fourier transform infrared (FTIR) spectroscopy is employed to examine poly( p-phenylene sulfide) (PPS). The fundamental vibrations of PPS are assigned based on those of known para-substituted benzene modes. Spectra of annealed and quenched PPS are obtained. Based on these spectra, the enhanced crystalline FTIR spectra of PPS are obtained. The spectra of PPS are interpreted based on the symmetry of the molecules. A heated cell is used to study in situ the IR spectroscopic changes upon melt-state and solid-state crystallization of PPS. Changes upon crystallization are identified from the different spectra. The cured and melt-state PPS spectra are also examined. Spectra of high and low molecular weight PPS are also studied.

Sequential crystallization kinetics of poly(p‐phenylene sulfide) doped with carbon or graphite particles

AbstractIsothermal crystallization kinetics were investigated by differential scanning calorimetry (DSC) for poly(p‐phenylene sulfide) (PPS) doped with amorphous carbon or crystalline graphite particles. Both types of carbon forms have been found to affect the crystallization behavior of PPS to different extents. The crystalline graphite particles have a more pronounced effect on the overall rate as well as mechanisms of PPS crystallization than do the amorphous carbon particles. Relative contributions and competition from crystallizations of two different crystals in the later‐stage crystallization of PPS have been found to cause the phenomenon of deviation from linearity in the Avrami plots. A sequential crystallization model has been shown to describe well the crystallization behavior of the PPS doped with the particles. © 1995 John Wiley & Sons, Inc.

The Nucleating Effect of a Semiflexible Liquid-Crystalline Polymer for the Crystallization of Poly(Phenylene Sulfide)

Abstract Blends of poly(phenylene sulfide) and a semiflexible liquid-crystalline polymer have been prepared, in the whole range of concentration, by melt mixing. The effect of the LCP phase on the crystallization of PPS has been studied by non-isothermal and isothermal calorimetry. It has been found that the addition of only 2-5% LCP into PPS strongly increases the crystallization rate of the latter polymer. This effect has been interpreted as the result of an increased nucleation density. The morphology of the blends, studied by scanning electron microscopy, has shown that the two polymers are incompatible, although the phase dispersion is good. Under elongational flow, the dispersed phase shows a distinct tendency toward fibrillation.

Non-isothermal crystallization kinetics of poly(phenylene sulfide)/Vectra-B blends

The non-isothermal crystallization behaviour of blends of poly(phenylene sulfide) (PPS) with the thermotropic liquid-crystalline copoly(ester amide) Vectra-B950 (VB) was studied by means of differential scanning calorimetry. The PPS crystallization temperature and the crystallization rate coefficient were found to increase markedly upon addition of 2–50% VB. It was shown that the Ozawa equation is valid not only for neat PPS but also for the blends. The values of the Avrami exponents are in fair agreement with those found previously by isothermal analysis, and do not depend on the presence and the concentration of VB. It has been suggested that the slope of the plots of the cooling crystallization function versus T can be a criterion for the overall non-isothermal crystallization rate. It has been concluded that the non-isothermal crystallization of PPS is strongly accelerated by the presence of the VB phase, whereas the type of nucleation and the geometry of crystal growth do not change, and no reduction of the PPS degree of crystallinity could be noticed.

Gamma irradiation of poly(phenylene sulfide): Effects on crystallization behavior

Abstract The irradiation of polymers can bring about significant changes in the polymer structure and ultimately in their performance. Poly-(phenylene sulfide) (PPS) is an engineering polymer which is mostly used in applications where it is subjected to high-energy radiation. This paper reports the results of gamma irradiation of PPS. The technique of differential scanning calorimetry was used to monitor the changes in the melting and crystallization parameters of irradiated PPS. The heat of fusion was found to decrease upon irradiation, indicating a lower degree of crystallinity; however, a marginal increase was observed in the melting point. The nonisothermal crystallization of irradiated PPS indicated reduced crystallizability. This contention is also supported by the isothermal crystallization studies in which the crystallization rate for irradiated PPS was found to be decreased. The retardation in the crystallization of irradiated PPS has been attributed to the possible changes in the structure of th...

Effect of a China‐made poly(aryl‐ether‐ketone) on the crystallization kinetics of poly(1,4‐phenylene sulfide)

The investigation of isothermal crystallization kinetics of poly(phenylene sulfide) (PPS) and poly(phtalidylidene-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenyleneoxy-1,4-phenylene) (PEK-C)/PPS blends reveals that amorphous PEK-C exerts a dual influence on the crystallization rate of PPS in the blends: a nucleation effect which acelerates the crystallization of PPS and an obstruction to PPS diffusion which lowers the crystallization rate

Crystallization of poly(phenylene sulfide) in blends with high density polyethylene and poly(ethylene terephthalate)

The crystallization kinetics of poly(phenylene sulfide) (PPS) in blends with high density polyethylene (HDPE) and poly(ethylene terephthalate) (PET) is reported. Although the crystallization of PPS took place in the presence of the molten phase of the second component in both cases, the changes observed in the crystallization behaviour of PPS were different. Isothermal crystallization studies indicated that the crystallization of PPS was accelerated in PPS/PET blends whereas it was retarded in PPS/HDPE blends. The presence of the molten phase of the second component was found to affect the crystallization of PPS through changes in both nucleation and growth processes. The differences observed in the crystallization behaviour of PPS are explained on the basis of the physical state of the melt and the possibility of chemical interactions.

Thermal analysis of poly(phenylene sulfide) polymers. I: Thermal characterization of PPS polymers of different molecular weights

AbstractThermal properties of Fortron®®Registered trademark of Hoechst Celanese Corporation. poly(phenylene sulfide) (PPS) polymers of different molecular weights were studied by DSC. Crystallization studies revealed that the ability of these polymers to crystallize decreases with increasing molecular weight. The Avrami equation poorly describes the isothermal crystallization of PPS. Lamellar crystallization was observed for the lowest molecular weight sample. For the other, higher molecular weight polymers the Avrami exponent is always between 2 and 3, suggesting development of distorted spherulites with heterogeneous nucleation. The temperature dependence of the solid and melt heat capacities have been determined. The solid specific heat capacity did not exhibit a molecular weight dependence. The heat capacity increase at the glass transition, Tg, has been calculated to be 28.1 J°C−1 mole−1. The equilibrium melting point of PPS has been estimated to be 348.5°C using the Hoffman–Weeks method. The Tg of PPS increases with molecular weight. The Tg of the highest molecular weight evaluated is 92.5°C. A DMA relaxation peak corresponding to the onset of the phenylene ring rotation occurs at −92°C. Only the highest molecular weight could be quenched to a completely amorphous state.

Crystallization of fiber‐reinforced poly(phenylene sulfide) composites. I. Experimental studies of crystallization rates and morphology

AbstractThe isothermal crystallization from the melt of unreinforced poly(phenylene sulfide) (PPS) and of model carbon, aramid, and glass‐fiber‐reinforced PPS composites was studied by differential scanning calorimetry and optical microscopy. Crystallization was studied as a function of temperature, and the fiber contents in the composites were varied over a wide range. The results indicate that the influence of fibers on PPS crystallization is not only fiber specific, but also strongly dependent on the surface treatment (size). In general, fiber‐reinforced systems crystallized faster than unreinforced (PPS), and the degree of crystallinity was less under comparable crystallization conditions. It was also observed that the rate of crystallization was enhanced in those systems which exhibited transcrystallinity in thin PPS film/single fiber composites as compared to those systems which did not exhibit transcrystallinity. Furthermore, the degree of crystallinity showed a nonlinear crystallization temperature dependence for those systems that exhibited transcrystallinity.

Melting behaviour of poly (phenylene sulphide): 2. Multiple stage melt crystallization

Multiple stages of melt crystallization have been used in this study to investigate the origin of the multiple melting behaviour of poly(phenylene sulphide), PPS. In a companion study we reported results of single-stage melt crystallization of PPS and presented a model to explain the observation of multiple melting and crystallization temperature dependency of the melting peaks. In our model, the degree of undercooling determines whether the existence of preformed crystals or reorganization of imperfect crystals dominates the observed endothermic response. In this work, multiple sequences of crystallization and annealing from the melt have been used to vary the perfection of the crystals. At low crystallization temperature (high degree of undercooling), very imperfect crystals are formed which can reorganize during the d.s.c. scan. In Ryton V-1, triple melting peaks are observed, and the endothermic response depends strongly on annealing time and scan rate. Annealing at elevated temperature, which perfects the crystals, or increasing the scan rate, which reduces the chance for reorganization, both result in a decrease in the size of the uppermost endotherm. However, at high crystallization temperature (low degree of undercooling), the pre-existing crystals are much more perfect and less susceptible to reorganization. Studies of multiple stage crystallization indicate that it is possible to generate many distinct crystal populations by step-wise crystallization from the melt. The pre-existing crystals display their own melting points, each in response to a separate stage of crystallization. As many as seven melting points can be seen after five stages of melt crystallization, indicating that morphology (pre-existing crystals) dominates the appearance of the endothermic response after multiple stages of melt crystallization.

Sorption and dilation properties of poly(p‐phenylene sulfide) under high‐pressure carbon dioxide

AbstractSorption and dilation properties of the system poly(p‐phenylene sulfide) (PPS) and carbon dioxide have been investigated at pressures up to 50 atm over the temperature range 25–85°C. The shapes of the sorption isotherms are in agreement with those predicted by the dual‐mode theory. Analysis of the sorption and dilation isotherms confirms the occurrence of an isothermal glass transition. This occurrence and its corresponding disappearance in the range investigated is discussed. Values of the partial molar volume of CO2 sorbed in PPS are calculated below and above the isothermal transition. Compared with sorption by other polymers, these values were about the same in the glassy state, but were smaller in the rubbery state. Under 50 atm CO2 at 85°C crystallization of amorphous PPS was observed. The crystallinity estimated from the solubility before and after crystallization is about 20%.

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

AbstractAn 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.

Effects of fibers on the crystallization of poly(phenylene sulfide)

AbstractThe isothermal crystallization of unreinforced poly(phenylene sulfide) (PPS) and PPS filled with glass, carbon, and aramid fibers was studied by differential scanning calorimetry. The Avrami exponent and rate constant are reported, but the crystallization half‐times were used to compare the effects of different fibers on the rate of PPS crystallization. The aramid and carbon fibers decreased the crystallization half‐time with the aramid fiber having the most pronounced effect. The glass fibers affected the crystallization half‐time only at the higher crystallization temperatures. The aramid filled PPS exhibited anomalous degree of crystallinity behavior in that the degree of crystallinity passed through a minimum as a function of temperature. The other systems all exhibited increasing degree of crystallinity with increasing crystallization temperature. Finally, the Avrami plot for the aramid filled PPS is not linear, and the data are fitted better with two linear regions indicating that two types of crystallization processes may be present.