The β-nucleation of polypropylene random copolymer filled by nano-CaCO3 supported β-nucleating agent

In this article, ??-nucleation of nano-CaCO₃ (CC) supported ??-nucleating agent (Sup-??-NA) for random polypropylene copolymer (PPC) crystallization was studied by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction. The results showed that Sup-??-NA not only increased the peak temperature of the crystallization of PPC but also induced PPC to form almost pure ??-modification. It indicated that Sup-??-NA possessed effective ??-nucleation. The content of Sup-??-NA had little influence on the crystallization behavior and melting characteristics together with the ??-modification content of PPC, but those were affected by the mass ratio of CC/??-NA (calcium pimelate) in the Sup-??-NA. The final temperature of the melt between 300 and 180?°C did not affect the ??-nucleation of Sup-??-NA, although the ??-nucleation of Sup-??-NA would be decreased with the final temperature of the melt lower than 170?°C. In addition, DSC multiple heating and cooling scanning had little influence on the thermal stability of ??-nucleation of Sup-??-NA.     

Effect of β-nucleation on crystallization of photodegraded polypropylene

The work deals with crystallization of photodegraded polypropylene containing various amounts of β-nucleating agent based on N,N′-dicyclohexylnaphthalene-2,6-dicarboxamide. Compression-moulded samples were irradiated by UV-light, melted and subsequently non-isothermally crystallized. The results showed that the crystallization temperature decreased with increasing irradiation time. The irradiation caused the splitting of crystallization exotherms into two peaks indicating two crystallization mechanisms. The presence of β-nucleating agent in the material suppressed the peak splitting; the higher was the amount of nucleating agent in the sample, the later was the splitting observed.     

Preparation and crystallization of isotactic polypropylene composites filled by titanium dioxide-supported montmorillonite with a β-nucleating surface

To obtain multi-functional β-iPP composites, β-iPP composites are always filled by multiple fillers with α-nucleating ability. To prepare β-iPP/TiO₂/MMT composites, TiO₂-supported MMT with a β-nucleating surface was prepared through hydrolysis reaction of Tetra-n-butyl titanate and chemical reaction between pimelic acid and calcium ion. X-ray diffraction and scanning electron micrograph confirmed the formation of TiO₂ on the surface of MMT. The differential scanning calorimeter and X-ray diffraction illustrated that the β-iPP composites filled by TiO₂ and MMT had lower relative β-phase contents than β-iPP. It is observed by polarized optical microscope that addition of TiO₂-supported MMT with a β-nucleating surface into iPP can increase the spherulite nuclei density and decrease the spherulite size significantly and obtain the β-iPP/TiO₂/MMT composites with high relative β-phase content.     

Synergistic mechanical effects of calcite micro- and nanoparticles and β-nucleation in polypropylene copolymers

For improving the understanding of mechanical effects in micro- and nanocomposites based on polypropylene (PP) copolymers and precipitated or ground calcium carbonate (PCC or GCC), especially in the presence of significant portions of the β-modification, a set of compounds based on different PP grades and fillers with optional β-nucleation prepared by melt compounding was studied. A synergistic improvement of mechanical properties by a combination of calcite particles and β-nucleation was found for two of the investigated high-impact base polymers up to 20 wt.% of nanofiller. While in the past research positive toughness effects were always limited to PP homopolymers with a moderate original impact strength and to particles of less than 100 nm average diameter, the toughness of high impact ethylene–propylene impact copolymers could be increased by more than 150% even at sub-zero temperatures where the failure behaviour is determined by the disperse elastomer phase.     

A novel β-cyclodextrin polymer modified by sulfonate groups

Based on the special properties and advantages of β-cyclodextrin (β-CD), β-CD polymers have been widely studied and used in recent years. A lot of researches have focused on the adsorption and separation properties of β-CD polymers. In this paper, β-CD polymer modified by sulfonate groups, which was named S-β-CDP, was prepared using epichlorohydrin as crosslinker and tiron (1,2-dihydroxybenzene-3,5-disulfonic acid disodium salt) as modifier. β-CD polymer without modification, which was named β-CDP, was also prepared for comparison. Infrared spectra, elemental analysis and adsorption tests of S-β-CDP were carried out and compared with β-CDP. The content of sulfonate groups in S-β-CDP was obtained from elemental analysis. The dramatically increased adsorption capability toward methylene blue and basic magenta confirmed the existence and chemical activity of sulfonate groups in S-β-CDP. Due to the convenient preparation process and modified adsorption properties, S-β-CDP will find its applications in various fields such as water purification, drug loading, separation and analysis.     

Nonisothermal crystallization kinetics of isotactic polypropylene nucleated with a novel supported β-nucleating agent

The introduction of β-nucleating agent into isotactic polypropylene (iPP) is the most effective method to prepare β-iPP. In this paper, iPP nucleated with a novel highly efficient supported β-nucleating agent (NA100), calcium pimelate (CaHA) supported on the surface of nano-CaCO₃, was prepared and its nonisothermal crystallization kinetic, melting characteristic, and crystallization activation energy are investigated and compared with those of pure iPP, nano-CaCO₃ filled iPP, and β-nucleating agent CaHA nucleated iPP. The results indicate that addition of nano-CaCO₃ increases the crystallization temperature of iPP and has no influence on the crystal form of iPP. iPP and nano-CaCO₃ filled iPP mainly crystallize in the form of α-crystal. Although NA100 and CaHA induce iPP to mainly form β-crystal, NA100 nucleated iPP shows higher crystallization temperature, melting temperature, and β-phase content than that nucleated with CaHA without supports. Nonisothermal crystallization kinetic is well described by the equations of Avrami and Mo, and the crystallization activation energy was calculated from Kissinger’s method. It was found that the decreased crystallization activation energy is favorable to increase the crystallization rate and the content of β-crystal. Although the content of CaHA in 5 wt% NA100 nucleated iPP was less than that in 0.1 wt% CaHA nucleated iPP, the former formed more β-iPP than the latter, indicating that the β-nucleating agent CaHA supported on the surface of nano-CaCO₃ exhibits higher efficiency for preparation of β-iPP than pure CaHA powder.     

DSC and morphological studies on the crystallization behavior of β-nucleated isotactic polypropylene composites filled with Kevlar fibers

The crystallization behavior of β-nucleated isotactic polypropylene (PP) composites filled with Kevlar fibers (KFs), as well as that of non-nucleated PP/KF composites for comparison, was investigated using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The morphological observations revealed that the KF addition could induce thick α-transcrystalline layer around their surfaces in PP/KF composites, while no obvious transcrystalline layer could be detected in β-nucleated PP/KF composites. Detailed DSC investigations suggested that for the PP/KF composites, the dominant modification was α-form, and the crystallization process of matrix was promoted by KF addition, as illustrated by faster isothermal crystallization rate, shorter induction time, and higher crystallization temperature. However, for β-nucleated PP/KF composites, the main modification was β-form, and their crystallization characteristics were independent of KF addition, indicating that the α-nucleating effect of KFs was absent in this system. The DSC results were confirmed by further rheological and wide angle X-ray diffraction (WAXD) studies. The mechanism of the formation of transcrystalline layer was also discussed.     

Preparation of core–shell composite polymer particles by a novel heterocoagulation based on hydrophobic interaction

Submicron-sized cationic polystyrene shell particles with active ester groups were effectively self-assembled on hydrophobic surfaces of cross-linked polystyrene (PST) particles, uncharged core particles with ca. 8.5-µm diameter in aqueous systems. The hydrophobic interactions between the shell particles and core particles play a key role in heterocoagulation. The resulting heterocoagulates were highly physically stable in water, and the morphology was controlled by several factors including the solid content of latex, self-assembling time, and electrolyte concentration. Composite polymer particles with a core–shell structure were successfully obtained from the heterocoagulates by heat treatment for 3 h at a temperature above the glass transition temperature (T_g) of the cationic polymer shell particles.     

Improved lithium exchange at LiFePO4 cathode particles by coating with composite polypyrrole–polyethylene glycol layers

The polypyrrole–LiFePO₄ composites were synthesized by simple chemical oxidative polymerization of pyrrole (Py) monomer directly on the surface of LiFePO₄ particles. Properties of resulting polypyrrole–LiFePO₄ (PPy-LiFePO₄) samples (especially conductivity) are strongly affected by the preparation technique, polymer additives, and conditions during synthesis. For increasing of PPy-LiFePO₄ conductivity, we used polyethylene glycol (PEG) as additive during polymerization. The electrochemical behavior of the samples was examined by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that PPy/PEG composite polymer decreased the particle to particle contact resistance. Impedance measurements showed that the coating of PPy/PEG significantly decreases the charge transfer resistance of LiFePO₄ electrodes.     

Determination of phenolic compounds in environmental water samples after solid-phase extraction with β-cyclodextrin-bonded silica particles coupled with a novel liquid-phase microextraction followed by gas chromatography-mass spectrometry

A novel approach for the sample pre-treatment and determination of eight phenolic compounds in environmental water samples has been developed by hyphenating solid-phase extraction (SPE) and liquid-phase microextraction (LPME) techniques based on solid organic drop combined with gas chromatography-mass spectrometry detection (GC-MS). After pre-concentration and purification of the sample through column containing 60 mg of β-cyclodextrin-bonded silica particles as stationary phase, under the optimum conditions, LPME technique has been performed on the eluent solution. Under the selected conditions, limit of detection (LOD) of 0.002-0.04 μg/L (S/N=3), limit of quantification (LOQ) of 0.007-0.15 μg/L (S/N=10), pre-concentration factor of 752-3135 and linearity range of 0.01-25 μg/L have been obtained. A reasonable repeatability (RSD≤9.5%, n=5) with satisfactory coefficient of determination has been obtained between 0.9981 and 0.9997. The relative recoveries of the waste, sea, river and well water samples were higher than 79%.     

A novel oxygen-dependent deoximation by nitric oxide

A variety of aldoximes and ketoximes were oxidized to corresponding aldehydes and ketones by nitric oxide in the presence of oxygen.A presumed mechanism was suggested.     

A novel olefination of carbonyl compounds with α-bromoacetic ester mediated by tri-n-butylstibine

Tri-n-butylstibine has been found to mediate the olefinatlon of carbonyl compounds by α-bromoacetic ester to give corresponding olefins in good yields.     

β-Crystallisation tendency and structure of polypropylene grafted by maleic anhydride and its blends with isotactic polypropylene

Crystallization, melting and structure of three different commercial types of isotactic polypropylene (iPP) grafted by maleic anhydride (PP-g-MAH) with different maleic anhydride content (AC) and their β-nucleated versions were studied by X-ray diffractometry (WAXS), differential scanning calorimetry (DSC), polarised light microscopy (PLM) and scanning electron microscopy (SEM). The presence of maleic anhydride units disturbs the chain regularity, hereby decreases the crystallization tendency of iPP in general and the β-crystallisation ability in particular. β-modification of iPP (β-iPP) forms only in β-nucleated PP-g-MAH polymers studied if the anhydride content is not larger than 0.5 mass%. The influence of AC of PP-g-MAH on the feature the spherulitic structure is demonstrated by PLM and SEM micrographs. The β-nucleated iPP/PP-g-MAH blends containing 10 mass% PP-g-MAH crystallise predominantly in β-form independently of AC of the latter. The β-nuceated blends of iPP and PP-g-MAH with lowest AC crystallise in β-form in whole concentration range. The interaction parameter between iPP and PP-g-MAH polymers calculated by Nishi-Wang equation indicate limited interaction between the components.     

Crystallization and melting behaviors of polypropylene admixed by graphene and β-phase nucleating agent

In this work, the crystallization and melting behaviors of different polypropylene (PP) materials containing a certain amount of graphene, β-phase nucleating agent (β-NA), and their mixture, respectively, were comparatively investigated. The results showed that graphene exhibited the typical sheet structure in the PP matrix, and the presence of β-NA did not change the dispersion of graphene apparently. Both graphene and β-NA exhibited great nucleating effect for the crystallization of PP. However, the nucleation efficiency of β-NA was much larger than that of graphene. With the simultaneous presence of graphene and β-NA, the crystallization ability of PP matrix was greatly improved, which indicated that there was a synergistic effect between graphene and β-NA in accelerating crystallization of PP matrix. Furthermore, it was proved that the synergistic effect was greatly dependent upon the crystallization conditions. The higher the isothermal crystallization temperature or the bigger the cooling rate, the more apparent the synergistic effect was.     

Formation mechanism of anomalous “golf ball-like” composite polymer particles by seeded emulsion polymerization

Recently, the authors found that anomalous polystyrene/polybutyl acrylate composite particles, whose surfaces had many dents, were produced by emulsifier-free seeded emulsion polymerization of butyl acrylate with polystyrene seed particles. Such a particle was named a golf ball-like particle. In this article, the morphology and the formation mechanism of the golf ball-like composite polymer particles were studied.Part CLV of the series Studies on Suspension and Emulsion     

A novel synthesis of β-lactone precursors of pyramidalized alkenes

β-Lactone precursors 11 and 12 of pyramidalized alkenes 3,n = 1and 2, have been synthesized by a two-step route involving transannular Paterno-Buchi reaction of methyleneketones 7 and 8, followed by RuO₄ oxidation of the resulting oxetanes 9 and 10. Evidence for the formation of alkene 3,n = 2, by pyrolysis of 12 is presented.     

A novel synthesis of α, β-unsaturated γ-hydroxy carbonyl compounds from enones with carbon homologation

The alkylation of enone with 1-chloroalkyl phenyl sulfoxide followed by treatment with thiophenolate afforded α-phenylthio-β, γ-unsaturated carbonyl compound, which was oxidized and then hydrolyzed to give α, β-unsaturated γ-hydroxy carbonyl compound in good yield.     

Liposome solubilization induced by complexation with dimeric β-cyclodextrin

Dimeric β-cyclodextrins (β-CD) were prepared from the reaction of native β-CD with epichlorohydrin under basic conditions, and the effects on the diacetylene (DA) and polydiacetylene (PDA) liposomes have been investigated. Vesicular DA was solubilized in the presence of dimeric β-CD with the consequent inhibition of polymerization. The result is attributed to the formation of a complex between dimeric β-CD and DA liposomes, and it is clearly differentiated from that of monomeric β-CD. Furthermore, the ordered supramolecular structure of PDA was perturbed by the dimeric β-CD, which was detected from the visible color change. Finally, the morphological characteristics and size of PDA in the absence and presence of dimeric β-CD were examined using transmission electron microscopy and dynamic light scattering The results show fused structure of size more than 200 nm along with the deformation of the vesicles, and they represent a novel phenomenon of liposome structure induced by complexation with dimeric β-CD. The evaluated physicochemical characteristics can be applied to the development of carbohydrate-based detergents.     

A novel hydrogen peroxide-initiated reaction of difluorodiiodomethane with alkynes

The reaction of difluorodiiodomethane with alkynes (4a-e) in the presence of hydrogen peroxide afforded the corresponding β-iodo-α,β-unsaturated carboxylic acids.When propargylic alcohol was used as the substrate,β-iodo-α,β-unsaturated γ-butyrolactone (5f) was produced.The mechanism of the reaction was suggested.     

Coordination compounds of uranium and thorium with a novel double β-diketone

A novel double -diketone 1,6-bis(1-phenyl-3-methyl-5-oxo-pyrazol-4-yl) hexanedione-[1,6] (BPMOPH) was further studied on its coordination compounds with uranium and thorium, respectively. The IR, UV, and¹H-NMR spectra were examined, and the proposed structure is discussed.