Nonisothermal crystallization behavior of SPS/APS blends

The nonisothermal crystallization behavior of syndiotactic polystyrene (SPS)/atactic polystyrene (APS) blends was studied with differential scanning calorimetry to investigate the effects of APS on the crystallization behavior of SPS. Polarized optical microscopy and wide‐angle X‐ray diffractometry were also used to observe the morphology of the SPS crystalline structure. From a cyclic heating/cooling temperature program, we obtained found that APS retarded the crystallization (and recrystallization) of SPS and made the crystal less perfect, but the ultimate crystallinity of SPS did not change with the addition of APS. We also observed that APS was disposed in the interfibrillar region of SPS spherulites and did not change the crystalline form of SPS. This result will be helpful for improving SPS applications through blending with rubber‐toughened APS. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3001–3008, 2000     

Miscibility and isothermal crystallization behavior of polyamide 6/poly(vinyl alcohol) blend

An investigation of miscibility and isothermal crystallization behavior of Polyamide 6 (PA6)/Poly(vinyl alcohol) (PVA) blends was conducted. Fourier transform infrared spectra (FTIR) analysis indicated that the interactions between the carbonyl groups of PA6 and hydroxyl groups of PVA increase as the weight ratios of PA6 to PVA of PA6/PVA specimens increase. This interaction between PA6 and PVA leads to their miscibility in the amorphous region and even some extent effects on their crystal phase, respectively. Further isothermal crystallization behavior of PA6/PVA indicate that the miscibility of PVA in PA6 leading difficulty in crystallization of PA6. Several kinetics equations are employed to describe the effects of PVA on the crystallization properties of PA6 in PA6/PVA blends in detail. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1360–1368, 2008     

Miscibility of polystyrene (PS)/polyphenylsilsesquioxane (PPSQ) blends

PS/PPSQ blends with different compositions were prepared by two methods: (1) casting film of PS/PPSQ from the solution of two polymers, and (2) PS/PPSQ blends by in situ polymerization. After studying by solid-state NMR, PS and PPSQ in the casting films are miscible on the scale of several thousand nanometers. Miscibility of PS/PPSQ blends obtained by the second approach was investigated by DMA, SEM, x-ray energy spectrometer, x-ray diffraction, and fluorescence techniques. Only one glass transition temperature could be observed in their DMA curves. There are two phases observable in their SEM micrographs. X-ray diffraction patterns and fluorescence excited spectra of this blend indicate that there is some interaction between molecules of PS and PPSQ in both the continuous phase and dispersed phase. PS and PPSQ in the in situ blends are partially miscible when the percentage of PPSQ is not more than 10%. © 1996 John Wiley & Sons, Inc.     

由结晶动力学评价含结晶聚合物共混物相容性的研究进展

介绍了用结晶动力学分析的方法评价含结晶聚合物共混物的混合状态的基本理论和解析原理,综述了最新研究进展.     

Nonisothermal crystallization behavior of syndiotactic polystyrene/montmorillonite nanocomposites

X‐ray diffraction methods and differential scanning calorimetry were used to investigate the crystalline structure and crystallization kinetics of syndiotactic polystyrene (sPS)/clay nanocomposites. X‐ray diffraction data showed the presence of polymorphism in sPS/montmorillonite (MMT) nanocomposites, which was strongly dependent on the processing conditions (premelting temperature and cooling rate) of the sPS/MMT nanocomposites and on the content of MMT in the sPS/MMT nanocomposites. The α‐crystalline form could be transformed into β‐crystalline forms at higher premelting temperatures. The nonisothermal melt‐crystallization kinetics and melting behavior of the sPS/MMT nanocomposites were also studied at various cooling rates. The correlation of the crystallization kinetics, melting behavior, and crystalline structure of the sPS/MMT nanocomposites was examined. The results indicated that the addition of a small amount of MMT to sPS caused a change in the mechanism of nucleation and the crystal growth of the sPS crystallite. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 560–570, 2003     

Crystallization kinetics and crystallization behavior of syndiotactic polystyrene/clay nanocomposites

We investigated the effects of montmorillonite (clay) on the crystallization kinetics of syndiotactic polystyrene (sPS) with isothermal differential scanning calorimetry analyses. The clay was dispersed into the sPS matrix via melt blending on a scale of 1–2 nm or up to about 100 nm, depending on the surfactant treatment. For a crystallization temperature of 240 °C, the isothermal crystallization data were fitted well with the Avrami crystallization equation. Crystallization data on the kinetic parameters (i.e., the crystallization rate constant, Avrami exponent, clay content, and clay/surfactant cation‐exchange ratio) were also investigated. Experimental results indicated that the crystallization rate constant of the sPS nanocomposite increased with increasing clay content. The clay played a vital role in facilitating the formation on the thermodynamically more favorable all‐β‐form crystal when the sPS was melt‐crystallized. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2097–2107, 2001     

Miscibility and biodegradability of silk fibroin/carboxymethyl chitin blend films

Blend films of silk fibroin and carboxymethyl chitin were prepared by solution casting using water as a cosolvent. The blend films were subjected to post-treatment with an aqueous methanol solution to induce beta-sheet formation of silk fibroin. The miscibility of the blend films both before and after methanol treatments was investigated in terms of chemical interactions, morphologies, thermal properties, and crystal structures by using FTIR spectroscopy, SEM, DSC, and XRD. The results indicate that the blend between silk fibroin and CM-chitin was semi-miscible because only the amorphous parts of the polymers were compatible with each other. The enzymatic degradation showed that the incorporation of CM-chitin enhanced biodegradability and swelling ability of silk fibroin.     

Miscibility and crystallization behavior of solution-blended PEEK/PI blends

Miscibility and crystallization behavior of solution-blended poly(ether ether ketone)/polyimide (PEEK/PI) blends were investigated by using DSC, optical microscopy and SAXS methods. Two kinds of PIs, YS-30 and PEI-E, which consist of the same diamine but different dianhydrides, were used in this work. The experimental results show that blends of PEEK/YS-30 are miscible over the entire composition range, as all the blends of different compositions exhibit a single glass transition temperature. The crystallization of PEEK was hindered by YS-30 in PEEK/YS-30 blends, of which the dominant morphology is interlamellar. On the other hand, blends of PEEK/PEI-E are immiscible, and the effect of PEI-E on the crystallization behavior of PEEK is weak. The crystallinity of PEEK in the isothermally crystallized PEEK/YS-30 blend specimens decreases with the increase in PI content. But the crystallinity of PEEK in the annealed samples almost keeps unchanged and reaches its maximum value, which is more than 50%. The spherulitic texture of the blends depends on both the blend composition and the molecular structure of the PIs used. The more PI added, the more imperfect the crystalline structure of PEEK. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2267–2274, 1998     

PET和TCL共聚酯共混体系相容性

利用热分析研究了聚对苯二甲酸乙二醇酯（ＰＥＴ）与对苯二甲酸乙二醇酯（ＥＴ）－己内酯（ＣＬ）共聚物（ＴＣＬ）共混体系的相容性，同时考察了体系中ＴＣＬ组成分布不均一性及高温热处理对体系相容性的影响。     

LLDPE／LDPE共混体系的相容性与性能

ＬＬＤＰＥ／ＬＤＰＥ共混体系的相容性与性能杨毓华，花荣，白春霞，于旻李三喜，葛铁军（中国科学院长春应用化学研究所长春１３００２２）（沈阳化工学院高分子系沈阳）关键词ＤＳＣ，ＷＡＸＤ，力学性能，ＬＬＤＰＥ，ＬＤＰＥ，共混，相容性非晶－非晶－结晶共混体系...     

Miscibility and crystallization behavior of PBT/epoxy blends

The miscibility and the isothermal crystallization kinetics for PBT/Epoxy blends have been studied by using differential scanning calorimetry, and several kinetic analyses have been used to describe the crystallization process. The Avrami exponents n were obtained for PBT/Epoxy blends. An addition of small amount of epoxy resin (3%) leads to an increase in the number of effective nuclei, thus resulting in an increase in crystallization rate and a stronger trend of instantaneous three‐dimensional growth. For isothermal crystallization, crystallization parameter analysis showed that epoxy particles could act as effective nucleating agents, accelerating the crystallization of PBT component in the PBT/Epoxy blends. The Lauritzen–Hoffman equation for DSC isothermal crystallization data revealed that PBT/Epoxy 97/3 had lower nucleation constant K_g than 100/0, 93/7, and 90/10 PBT/Epoxy blends. Analysis of the crystallization data of PBT/Epoxy blends showed that crystallization occurs in regime II. The fold surface free energy, σ_e = 101.7–58.0 × 10^?3 J/m², and work of chain folding, q = 5.79–3.30 kcal/mol, were determined. The equilibrium melting point depressions of PBT/Epoxy blends were observed and the Flory–Huggins interaction parameters were obtained. It indicated that these blends were thermodynamically miscible in the melt. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1320–1330, 2006     

O-(4-喹唑啉)羟肟酸硫代酯(酰胺)类化合物的合成及生物活性

用差示扫描量热分析研究了间规聚苯乙烯（ｓＰＳ）的非等温结晶及其动力学，并分别用Ｏｚａｗａ和Ｊｅｚｉｏｒｎｙ两种方法来处理ｓＰＳ的非等温结晶数据．结果表明，在２５～４０℃／ｍｉｎ的冷却速率范围内，ｓＰＳ的半结晶时间随冷却速率增大而呈指数式下降，ｓＰＳ非等温结晶过程遵循Ｏｚａｗａ动力学方程，但不符合Ｊｅｚｉｏｒｎｙ方法中的Ａｖｒａｍｉ动力学方程．所得到的ｓＰＳ非等温结晶Ａｖｒａｍｉ指数ｎ在３６～４１之间，高于等温结晶时的ｎ值     

Inter-spherulitic/inner-spherulitic localization of PBSU during crystallization of PVDF in PVDF/PBSU blend

In this work, the miscibility effect on the localization of poly(butylene succinate) (PBSU) during the crystallization of PVDF in their blend has been investigated. After annealed at 200 °C and 240 °C, homogeneous and phase-separated structures can be obtained respectively, which was followed by isothermal crystallization at 141 °C. In the case of 200°C, PBSU tends to enrich in inner-spherulitic regions because of the excellent miscibility of the blend and the higher growth rate of PVDF crystals. When the specimen was annealed at 240 °C, phase separation produces PVDF and PBSU domains. Upon cooling to 141 °C, one part of PBSU is miscible with , while the other part of it remains as phase-separated domains due to the high viscosity and slow relaxation of them. The former accounts for the distribution of PBSU in inner-spherulitic regions. In the latter, however, phase-separated structures depress the diffusion of PVDF during its crystallization, leading to the lower magnitude of growth rate of spherulites. Both of them contribute to the localization of PBSU in inter-spherulitic regions. The distribution of PBSU among PVDF spherulites has been validated by long periods, pore size, and mechanical performance of the porous PVDF membranes.     

Morphological and Structural Studies of sPS/aPS Blends

Inrecentyears,thenewsedricrystallinepolymersyndiotacticp0lystyrene(sPS)hasat-ITactedmuchattentionduetoitsg0odchendcalresistanceandenhancedmechanicalperformanceatelevatedtemPeratUre.'H0wever,itexhibitshighbrittlenessandpoorimPact-resistanceandtCar-resistance.2Therefore,itisnecessarytomodifyitwithtougheningpolyIners.AsimPlemeth0dto0verc0methedriscibilityofatwo-phaseblendofsPSandatougheningpolymristotwrovetheinterfacialaffmity,wheretheadditionofablockcoP0lymerisconsideredtobemosteffective.3…     

Novel phosphate glass/polyamide 6 hybrids: Miscibility,crystallization kinetics,and mechanical properties

The miscibility, crystallization kinetics, and mechanical properties of a novel low T_g phosphate glass (Pglass)/polyamide 6 hybrid material were investigated. Here, we report the first evidence for miscibility of inorganic phosphate glass and organic polymer prepared by blending both components in the liquid phase using conventional polymer processing methods. From classical melting point depression measurements, we obtained a chi interaction parameter (χ) of −0.067 for the Pglass/polyamide 6 hybrid, indicating that the inorganic glass and polyamide 6 are miscible. The crystallization kinetic parameters for the hybrids were determined using the Avrami approach and found to depend on the volume fraction of Pglass present in the system. In addition, we studied both the dynamic and static mechanical behavior of the hybrids. The results showed a single T_g that decreased by up to 10 °C with increasing phosphate glass volume percent for the hybrids, giving further evidence for the hybrid component miscibility and plasticizing action of the phosphate glass in the pure polyamide 6, respectively. The tensile (static) mechanical properties of the hybrids were found to be remarkably similar to those obtained from typical polymers plasticized with relatively low molecular weight compounds. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 441–450, 2006     

Study of bundle formation during crystallization in polymer blends

The development of texture which exists in polymer spherulites grown from single phase melts containing an appreciable amount of noncrystallizable material was investigated. This texture generally consists of lamellar bundles separated by amorphous regions, both of which are typically 0.1–1 μm thick. A space–time finite element model previously developed by us was used to simulate the growth of a group of polymer lamellae. The model determines the impurity concentration field in the melt surrounding the growing lamellae and tracks the growth of each lamella. Important variables are the initial melt concentration of noncrystallizable material, the mass diffusion coefficient of noncrystallizable species, lamellar thickness, long period, and the rate of molecular attachment at the growth front. Under certain conditions, bundles did indeed develop during the simulations. These results were used to predict bundle thicknesses. The predictions of bundle texture were compared to actual textures observed in blends of syndiotactic and atactic polystyrene. It was found both experimentally and numerically that bundle thickness was a strong function of crystallization temperature and a relatively weak function of both the initial composition of noncrystallizable species and the degree of crystallinity of the lamellar stack. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 873–888, 1998     

Surface enrichment and crystallization of polyamide and polytetrafluoroethylene blend

The blend surface of polyamide 6 and polytetrafluoroethylene (PA 6/PTFE) and its change as a function of annealing time are investigated by means of attenuated total reflection (ATR)‐FTIR spectroscopy, contact angle (CA) measurement, as well as atomic force microscopy (AFM) under ambient condition; meanwhile the surface elemental compositions are obtained by X‐ray photoelectron spectroscopy (XPS). The results show that the addition of fluoro content can decrease the surface energy compared with the pure polyamide, while, an evident influence on the surface energy has not been detected with increasing fluoro contents. Upon annealing at 120 °C, there is a profound enrichment of the low‐surface energy component to the sample surface; yet this situation becomes more complex when samples are annealed at 150 °C—not only the segregation effect from the low surface energy PTFE, but also the crystallization of the PA 6 will come into play for the blend with 50% PTFE. These observations are ascribed to the presence of the polar group of the polyamide component, as well as its strong tendency to crystallize when subjected to thermal treatment at sufficiently high temperatures, and this behavior would basically offset the segregation tendency of fluoro component to the sample surface. This assumption is further corroborated by the XPS measurement in the current researches. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 138–152, 2007     

Thermal and mechanical properties of syndiotactic polystyrene/organoclay nanocomposites with different microstructures

The fabrication of syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process with poly(styrene‐co‐vinyloxazolin) (OPS), that is, melt intercalation of OPS into organoclay followed by blending with sPS. The microstructure of nanocomposite mainly depended on the arrangement type of the organic modifier in clay gallery. When organoclays that have a lateral bilayer arrangement were used, an exfoliated structure was obtained, whereas an intercalated structure was obtained when organoclay with a paraffinic monolayer arrangement were used. The thermal and mechanical properties of sPS nanocomposites were investigated in relation to their microstructures. From the thermograms of nonisothermal crystallization and melting, nanocomposites exhibited an enhanced overall crystallization rate but had less reduced crystallinity than a matrix polymer. Clay layers dispersed in a matrix polymer may serve as a nucleating agent and hinder the crystal growth of polymer chains. As a comparison of the two nanocomposites with different microstructures, because of the high degree of dispersion of its clay layer the exfoliated nanocomposite exhibited a faster crystallization rate and a lower degree of crystallinity than the intercalated one. Nanocomposites exhibited higher mechanical properties, such as strength and stiffness, than the matrix polymer as observed in the dynamic mechanical analysis and tensile tests. Exfoliated nanocomposites showed more enhanced mechanical properties than intercalated ones because of the uniformly dispersed clay layers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1685–1693, 2004     

Molecular dynamics simulations of monodisperse/bidisperse polymer melt crystallization

We use large scale coarse‐grained molecular dynamics simulations to study the kinetics of polymer melt crystallization. For monodisperse polymer melts of several chain lengths under various cooling protocols, we show that short chains have a higher terminal crystallinity value compared to longer ones. They align at the early stages and then cease evolving. Long chains, however, align, fold into lamella structures and then slowly optimize their dangling ends for the remaining simulation time. We then identify the mechanism behind bidisperse blend crystallization. To this end, we introduce a new algorithm (called Individual Chain Crystallinity) that allows the calculation of the crystallinity separately for short and long chains in the blend. We find that, in general, bidispersity hinders crystallization significantly. At first the crystallinity of the long chain components exceeds that of the monodisperse melt, but subsequently falls below the corresponding monodisperse melt curve after a certain “crossover time.” The time of the crossover can be attributed to the time required for the full crystallization of the short chains. This indicates that at the early stages the short chains are helping long chains to crystallize. However, after all short chains have crystallized they start to hinder the crystallization of the long chains by obstructing their motion. Lastly, polymer crystallization upon various thermodynamic protocols is studied. Slower cooling is found to increase the crystallinity value. Upon an instantaneous deep quench and subsequent isothermal relaxation, the crystallinity grows rapidly with time at early stages and subsequently saturates. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2318–2326     

Effects of the oriented mesophase on the cold crystallization of syndiotactic polystyrene and its blend with poly(2,6‐dimethyl‐1,4‐phenylene oxide)

The effects of molecular orientation on the crystallization and polymorphic behaviors of syndiotactic polystyrene (sPS) and sPS/poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) blends were studied with wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry. The oriented amorphous films of sPS and sPS/PPO blends were crystallized under constraint at crystallization temperatures ranging from 140 to 240°C. The degree of crystallinity was lower in the cold‐crystallized oriented film than in the cold‐crystallized isotropic film. This was in contrast to the case of the cold crystallization of other polymers such as poly(ethylene terephthalate) and isotactic polystyrene, in which the molecular orientation induced crystallization and accelerated crystal growth. It was thought that the oriented mesophase was obtained in drawn films of sPS and that the crystallization of sPS was suppressed in that phase. The WAXD measurements showed that the crystal phase was more ordered in an sPS/PPO blend than in pure sPS under the same annealing conditions. The crystalline order recovered in the cold‐crystallized sPS/PPO blends in comparison with the cold‐crystallized pure sPS because of the decrease in the mesophase content. The crystal forms depended on the crystallization temperature, blend composition, and molecular orientation. Only the α′‐crystalline form was obtained in cold‐crystallized pure sPS, regardless of molecular orientation, whereas α′, α″, and β′ forms coexisted in the cold‐crystallized sPS/PPO blends prepared at higher crystallization temperatures (200–240°C). The β′‐form content was much lower in the oriented sPS/PPO blend than in the isotropic blend sample at the same temperature and composition. It was concluded that the oriented mesophase suppressed the crystallization of the stable β′ form more than that of the metastable α′ and α″ forms during the cold crystallization of sPS/PPO blends. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1665–1675, 2003