Low-density polyethylene superhydrophobic surface by control of its crystallization behavior

A simple and inexpensive method for forming a low-density polyethylene (LDPE) superhydrophobic surface by controlling the crystallization behavior of LDPE by adjusting the crystallization time and nucleation rate has been proposed. The resulting porous surface, with hierarchical micro- and nanostructures on the beautiful floral designs, has a water contact angle of 173.0degrees +/- 2.5degrees.

Effect of poly(propylene carbonate) on the crystallization and melting behavior of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate)

The crystallization and melting behavior of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (PHBV) and a 30/70 (w/w) PHBV/poly(propylene carbonate) (PPC) blend was investigated with differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR). The transesterification reaction between PHBV and PPC was detected in the melt-blending process. The interaction between the two macromolecules was confirmed by means of FTIR analysis. During the crystallization process from the melt, the crystallization temperature of the PHBV/PPC blend decreased about 8 degreesC, the melting temperature was depressed by 4 degreesC, and the degree of crystallinity of PHBV in the blend decreased about 9.4%; this was calculated through a comparison of the DSC heating traces for the blend and pure PHBV. These results indicated that imperfect crystals of formed, crystallization was inhibited, and the crystallization ability of PHBV was weakened in the blend. The equilibrium melting temperatures of PHBV and the 30/70 PHBV/PPC blend isothermally crystallized were 187.1 and 179 degreesC, respectively.

Fractionated crystallization of dispersed PA6 phase of PP/PP-g-MAH/PA6 blends

Fractionated crystallization behavior of dispersed PA6 phase in PP/PA6 blends compatibilized with PP-g-MAH was investigated by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), polarized light microscopy (PLM), and wide-angle X-ray diffraction (WAXD) in this work. The lack of usual active heterogeneities in the dispersed droplet was the key factor for the fractionated crystallization of PA6. The crystals formed with less efficient nuclei might contain more defects in the crystal structures than those crystallized with the usual active nuclei. The lower the crystallization temperature, the lesser the perfection of the crystals and the lower crystallinity would be. The fractionated crystallization of PP droplets encapsulated by PA6 domains was also observed. The effect of existing PP-g-MAH-g-PA6 copolymer located at the interface on the fractionated crystallization could not be detected in this work.

Thermal and crystalline properties of random copolymer of CL and DTC prepared by La(OAr)(3)

Thermal and crystalline properties of random copolymer of epsilon-caprolactone (CL) and 2,2-dimethyl trimethylene carbonate (DTC) prepared by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)(3)) have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and wide-angle X-ray diffraction (WAXD). Fox equation interprets the relationship between glass transition temperature (T-g) and copolymer compositions. T-g decreases from PDTC (16.7degreesC) to PCL (-65.1degreesC), reflecting the internal plasticizing effect of CL units on DTC units in the copolymers. The introduction of CL units to PDTC can effectively improve its heat resistance. Small amount of DTC (5% molar) in PCL chain improves the mechanical properties of the polymer, which had elongation of 1000, much higher than that of PCL (8.8).

Morphology, tensile strength and thermal behavior of isotactic polypropylene/syndiotactic polystyrene blends compatibilized by SEBS copolymers

The effects of three triblock copolymers of poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) of different molecular weight (MW) on the morphology, tensile strength and thermal behavior of isotactic polypropylene/syndiotactic polystyrene (iPP/sPS, 80/20) blend are investigated. Morphology observation shows that both the medium MW and the lower MW SEBS are more effective than the higher MW SEBS in compatibilizing the blends. Tensile tests revels both the medium and low MW compatibilizer lead to a significant improvement in tensile strength, while the higher MW compatibilizer is efficient in increasing the elongation at break of the blends. The localization of compatibilizers in the blends is observed by mean of SEM and the correlation between the distribution of the compatibilizers and mechanical properties of the blends is evaluated. The mechanical properties of the iPP/sPS blends depend on not only the interfacial activity of the compatibilizers but also the distribution of the compatibilizer in the blend. Addition of the compatibilizers to the blend causes a remarkable decrease in the magnitude of the crystallization peak of sPS at its usual T-c. Vicat softening points demonstrate that the heat resistance of iPP/sPS blend is much higher than that of the pure iPP.

Solvent-induced crystallization of spherical micelles formed by copolymer blends

We have followed the morphological evolution and crystallization process of spherical micelles formed by the mixture of polystyrene-b-poly(acrylic acid) (PS-b-PAA) and polystyrene-b-poly(2-vinylpyridine)b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) (the core of the spherical micelles was made of P2VP and PAA blocks through hydrogen bonding in neutral solvent N,N-dimethylformamide, DMF) via DMF vapor treatment. Different phenomena, such as rupture of the film, formation of cylinder aggregates and regular square lamellae, were observed when the micelle film was treated in DMF for different times. At the early stage of annealing in DMF vapor, the micelle film became unstable and ruptured. Cylinder aggregates, within which the PEO blocks achieved the association and primary chain folding, formed as the mesophases before the nucleation of the PEO single crystals at this stage. Further treatment in DMF vapor resulted in the nucleation of the PEO blocks at the corners of quasi-square lamellae. Then a quite regular "sandwich" lamellar structure, constructed by a PEO single-crystal layer covered by two tethered layers of other amorphous blocks on the top and bottom crystal basal surfaces, formed when the film of micelles was annealed in DMF vapor for sufficient times.

Formation of a unique crystal morphology for the poly(ethylene glycol)-poly(epsilon-caprolactone) diblock copolymer

The crystallization behaviors of the poly(ethylene glycol)-poly(epsilon-caprolactone) diblock copolymer with the PEG weight fraction of 0.50 (PEG(50)-PCL50) was studied by DSC, WAXD, SAXS, and FTIR. A superposed melting point at 58.5 degrees C and a superposed crystallization temperature at 35.4 degrees C were obtained from the DSC profiles running at 10 degrees C/min, whereas the temperature-dependent FTIR measurements during cooling from the melt at 0.2 degrees C/min showed that the PCL crystals formed starting at 48 degrees C while the PEG crystals started at 45 degrees C. The PEG and PCL blocks of the copolymer crystallized separately and formed alternating lamella regions according to the WAXD and SAXS results. The crystal growth of the diblock copolymer was observed by polarized optical microscope (POM). An interesting morphology of the concentric spherulites developed through a unique crystallization behavior. The concentric spherulites were analyzed by in situ microbeam FTIR, and it was determined that the morphologies of the inner and outer portions were mainly determined by the PCL and PEG spherulites, respectively. However, the compositions of the inner and outer portions were equal in the analysis by microbeam FTIR.

Crystallization and phase behavior of crystalline syndiotactic 1,2-polybutadiene/isotactic polypropylene blends in solution-cast thin films

Crystallization and phase behavior in solution-cast thin films of crystalline syndiotactic 1,2-polybutadiene (s-1,2-PB) and isotactic polypropylene (i-PP) blends have been investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM) techniques. Thin films of pure s-1,2-PB consist of parallel lamellae with the c-axis perpendicular to the film plane and the lateral scale in micrometer size, while those of i-PP are composed of cross-hatched and single-crystal-like lamellae. For the blends, TEM and AFM observations show that with addition of i-PP, the s-1,2-PB long lamellae become bended and i-PP itself tends to form dispersed convex regions oil a continuous s-1,2-PB phase even when i-PP is the predominant component, which indicates a strong phase separation between the two polymers during film formation. FESEM micrographs of both lower and upper surfaces of the films reveal that the s-1,2-PB lamellae pass through i-PPconvex regions from the bottom, i.e. the dispersed i-PP regions lie on the continuous s-1,2-PB phase. The structural development is attributed to an interplay of crystallization and phase separation of the blends in the film forming process.

Melt rheological properties of polypropylene-polyarnide6 blends compatibilized with maleic anhydride-grafted polypropylene

The melt rheological properties of binary uncompatibilized polypropylene -polyamide6 (PP-PA6) blends and ternary blends compatibilized with maleic anhydride-grafted PP (PP-PP-g-MAH-PA6) were studied using a capillary rheometer. The experimental shear viscosities of blends were compared with those calculated from Utracki's relation. The deviation value delta between these two series of data was obtained. In binary PP-PA6 blends, when the compatibility between PP and PA6 was poor, the deformation recovery of dispersed PA6 particles played the dominant role during the capillary flow, the experimental values were smaller than those calculated, and delta was negative. The higher the dispersed phase content, the more deformed the droplets were and the lower the apparent shear viscosity. Also, the absolute value of delta increased with the dispersed phase composition. In ternary PP-PP-g-MAH-PA6 systems, when the compatibility between PP and PA6 was enhanced by PP-g-MAH, the elongation and break-up of the dispersed particles played the dominant role, and the experimental values were higher than calculated. It was observed that the higher the dispersion of the PA6 phase, the higher the delta values of the ternary blends and the larger the positive deviation.

Nonisothermal crystallization behavior of glass-bead-filled polypropylene

The effects of the glass-bead content and size on the nonisothermal crystallization behavior of polypropylene (PP)/glass-bead blends were studied with differential scanning calorimetry. The degree of crystallinity decreased with the addition of glass bead, and the crystallization temperature of the blends was marginally higher than that of pure PP at various cooling rates. Furthermore, the half-time for crystallization decreased with an increase in the glass-bead content or particle size, implying the nucleating role of the glass beads. The nonisothermal crystallization data were analyzed with the methods of Avrami, Ozawa, and Mo. The validity of various kinetic models for the nonisothermal crystallization process of PP/glass-bead blends was examined. The approach developed by Mo successfully described the nonisothermal crystallization behavior of PP and PP/glass-bead blends. Finally, the activation energy for the nonisothermal crystallization of pure PP and PP/glass-bead blends based on the Kissinger method was evaluated.

Reactive blending of modified polypropylene and polyamide 12: Effects of compatibilizer content on crystallization and blend morphology

The crystallization behavior and morphology of nonreactive and reactive melt-mixed blends of polypropylene (PP) and polyamide (PA12; as the dispersed phase) were investigated. It Was found that the crystallization behavior and the size of the PA12 particles were dependent on the content of the compatibilizer (maleic anhydride-modified polypropylene) because an in situ reaction occurred between the maleic anhydride groups of the compatibilizer and the amide end groups of PA12. When the amount of compatibilizer was more than 4%, the PA12 did not crystallize at temperatures typical for bulk crystallization. These finely dispersed PA12 particles crystallized co-incidently with the 1313 phase. The changes in domain size with compatibilizer content were consistent with Wu's theory. These investigations showed that crystallization of the dispersed phase Could not be explained solely by the size of the dispersion. The interfacial tension between the polymeric components in the blends may yield information on the fractionation of crystallization.

Compositional differences of propylene-ethylene block copolymers manufactured by degradation and hydrogenation techniques

The purpose of the present work is to investigate the compositional difference of polypropylene-polyethylene block copolymers (PP-b-PE) manufactured industrially by the process of degradation and hydrogenation, respectively. Each of the PP-b-PE copolymers was fractionated into three fractions with heptane and chloroform. The compositions of the three fractions were characterized by C-13 nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy, as well as differential scanning calorimetry (DSC) and thermal fractionation. The results showed that the Chloroform-soluble fraction was amorphous ethylene-propylene rubber, and the content of the rubber in PP-b-PE manufactured by hydrogenation was less than that by degradation. The degree of crystallinity of the chloroform-insoluble fraction of the PP-b-PE manufactured by hydrogenation is higher than that of by degradation.

Phase transition in polyamide-66/montmorillonite nanocomposites on annealing

The crystalline-phase transition in polyamide-66/montmorillonite nanocomposites before melting was investigated by in situ X-ray diffraction and is reported for the first time in this work. The phase-transition temperature in the nanocomposites was 170 degreesC, 20 degreesC lower than that in polyamide-66. The lower phase-transition temperature of the nanocomposites could be attributed to the gamma-phase-favorable environment caused by silicate layers. Meanwhile, the addition of silicate layers changed the crystal structure of the polyamide-66 matrix and influenced the phase-transition behavior.

Miscibility and crystallization behavior of poly(3-hydroxyvalerate-co-3-hydroxyvalerate)/poly(propylene carbonate) blends

Blends of synthetic poly(propylene carbonate) (PPC) with a natural bacterial copolymer of 3-hydroxybutyrate with 3-hydroxyvalerate (PHBV) containing 8 mol % 3-hydroxyvalerate units were prepared with a simple casting procedure. PPC was thermally stabilized by end-capping before use. The miscibility, morphology, and crystallization behavior of the blends were investigated by differential scanning calorimetry, polarized optical microscopy, wide-angle X-ray diffraction (WAXD), and small-angle Xray scattering (SAXS). PHBV/PPC blends showed weak miscibility in the melt, but the miscibility was very low. The effect of PPC on the crystallization of PHBV was evident. The addition of PPC decreased the rate of spherulite growth of PHBV, and with increasing PPC content in the PHBV/PPC blends, the PHBV spherulites became more and more open. However, the crystalline structure of PHBV did not change with increasing PPC in the PHBV/PPC blends, as shown from WAXD analysis. The long period obtained from SAXS showed a small increase with the addition of PPC.