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Isotactic Poly (isotactic + poly)
Selected AbstractsSynthesis and Structure,Efficiency Relations of 1,3,5-Benzenetrisamides as Nucleating Agents and Clarifiers for Isotactic Poly(propylene),MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2010Frank Abraham Abstract This paper presents the synthesis and properties of 1,3,5-benzenetrisamides with a particular focus on structure-efficiency relationships of nucleation and optical property enhancement of isotactic poly(propylene) (i -PP). A family of twenty 1,3,5-benzenetrisamide derivatives was synthesized, in which the direction of the amide linkage between the core and the peripheral substituents, as well as their length (C-3 to C-6) and flexibility were systematically varied. Dissolution- and recrystallization temperatures of the additives in the polymer melt, the crystallization temperature of i -PP, and the optical properties clarity and haze were determined in the additive concentration range from 200 to 2,500,ppm. Within the reported series of compounds, few exhibited very good nucleating and clarification abilities, only one with outstanding characteristics, whereas other, very closely related derivatives were found to be incapable to nucleate or clarify i -PP, although, intriguingly, most are structural isomers. We conclude that it is the particular chemical structure of the additive that determines its crystallization/self-assembly process, and, therewith, the structure of the heterogeneous nuclei, and at a higher hierarchical level the morphology of the poly(propylene) solid state and its final properties; and, hence, that a predictive understanding is still elusive. [source] Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2008Cristian Hedesiu Abstract Changes in phase composition and chain mobility in injection-molded isotactic poly(propylene), crystallized from the melt with slow cooling rate and subsequently quenched, associated with aging at temperature well above Tg for 150 and 1 000 h, are studied using time-domain 1H solid-state NMR and XRD. All sample exhibit physical aging when exposed to elevated temperatures, and the physical aging kinetics was observed to depend on the morphology of the homopolymer iPP and aging temperatures. The significant increase in the tensile modulus in time was observed for injection-molded iPP. The observed property changes induced by aging are attributed to microstructural changes within the semi-rigid and amorphous fractions. [source] Thermal Behavior of Isotactic Poly(propylene)/Maleated Poly(propylene) BlendsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2007Catalin Vīlcu Abstract This paper analyzes the thermal and thermo-oxidative degradation behavior, phase separation, melting, and crystallization of blends consisting of isotactic poly(propylene) (IPP) and poly(propylene) grafted with maleic anhydride (PP- g -MA). It has been established that, depending on the blend composition and crystallization/preparation procedure, the blends of IPP and PP- g -MA can either co-crystallize or evidence phase separation. This conclusion has been attained by comparing the DSC results of crystallization under dynamic and isothermal conditions with X-ray diffraction results. On the basis of the obtained results, the optimum mixing ratios have been established as 95,85 wt.-% IPP/5,15 wt.-% PP- g -MA. Thermo-oxidative behavior has been studied by thermogravimetry and differential thermal analysis. [source] Rheological Investigations in Understanding Shear-Enhanced Crystallization of Isotactic Poly(propylene)/Multi-Walled Carbon Nanotube CompositesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2007Ke Wang Abstract A novel experimental technique to follow the crystallization processes of poly(propylene)/MWCNT composites that experience a steady shear deformation using dynamic melt rheometry is described. The effects of heterogeneous nucleation, temperature, and preshear on the crystallization behaviors were determined. A quantitative evaluation of crystallization kinetics difference between quiescent and preshear conditions could be achieved. By combining rheology with POM, we demonstrate that two different crystallization processes account for the shear-enhanced crystallization at low and high temperatures, respectively. [source] Isotactic Poly(propylene)/Monoalkylimidazolium-Modified Montmorillonite Nanocomposites: Preparation by Intercalative Polymerization and Thermal Stability StudyMACROMOLECULAR RAPID COMMUNICATIONS, Issue 24 2004Aihua He Abstract Summary: Poly(propylene)/monoalkylimidazolium-modified montmorillonite (PP/IMMT) nanocomposites were prepared by in situ intercalative polymerization of propylene with TiCl4/MgCl2/MMT catalyst. The PP synthesized possessed high isotacticity and molecular weight. Both wide-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the nanocomposite formation with exfoliated MMT homogeneously distributed in the PP matrix. A thermal stability study revealed that the nanocomposites possess good thermal stability. X-ray diffraction patterns of PP/IMMT (MMT,=,2.2 wt.-%) nanocomposite before and after processing. [source] Synthesis and Functionalization of Isotactic Poly(propylene) Containing Pendant Styrene GroupsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004Junfeng Zou Abstract Summary: Copolymerization of propylene and 1,4-divinylbenzene was successfully performed by a MgCl2 -supported TiCl4 catalyst, yielding isotactic poly(propylene) (i -PP) polymers containing a few pendant styrene groups. With a metalation reaction with butyllithium and a hydrochlorination reaction with dry hydrogen chloride, the pendant styrene groups were quantitatively transformed into benzyllithium and 1-chloroethylbenzene groups, respectively, which allowed the synthesis of i -PP-based graft copolymers by living anionic and atom transfer radical (ATRP) polymerization mechanisms. The incorporation of styrene pendant groups into isotactic poly(propylene) using a Zeigler,Natta catalyst gave functionalized polymers able to undergo living anionic and atom transfer radical (ATRP) polymerizations. [source] Strain-Controlled Tensile Deformation Behavior and Relaxation Properties of Isotactic Poly(1-butene) and Its Ethylene CopolymersMACROMOLECULAR SYMPOSIA, Issue 1 2004Mahmoud Al-Hussein Abstract The tensile deformation behaviour of poly(1-butene) and two of its ethylene copoloymers was studied at room temperature. This was done by investigating true stress-strain curves at constant strain rates, elastic recovery and stress relaxation properties and in-situ WAXS patterns during the deformation process. As for a series of semicrystalline polymers in previous studies, a strain-controlled deformation behaviour was found. The differential compliance, the recovery properties and the stress relaxation curves changed simultaneously at well-defined points. The strains at which these points occurred along the true stress-strain remained constant for the different samples despite their different percentage crystallinities. The well-defined way in which the different samples respond to external stresses complies with the granular substructure of the crystalline lamellae in a semicrystalline polymer. [source] Metalloorganic Polymerization Catalysis as a Tool To Probe Crystallization Properties of Polymers: The Case of Isotactic Poly(1-butene),ANGEWANDTE CHEMIE, Issue 52 2009Claudio De, Rosa Prof. Alter wird sie nicht beugen: Stereodefekte isotaktische Polybutenproben, die mit einzentrigen Metallocenkatalysatoren synthetisiert wurden, kristallisieren aus der Schmelze in der stabilen Form,I (siehe Bild) und gehen beim Altern keine Phasenumwandlung ein. Damit bleiben auch die physikalischen und mechanischen Eigenschaften von Objekten, die aus diesen Materialien gegossen werden, beim Altern unverändert. [source] Stereospecific and Stereoselective Polymerization of 4-Methyl-1-hexene by Enantiomeric Binaphthyl-Bridged Salen Dichlorozirconium (IV) ComplexesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 18-19 2007Maria Strianese Abstract Two enantiomers of a chiral binaphthyl-bridged salen dichlorozirconium (IV) complex (namely R-,- 1 and S-,- 1) were synthesized and tested as pre-catalysts for 4-methyl-1-hexene (4MH) polymerization. Their behavior was compared with that of the same complex in its racemic form. Isotactic poly(4-methyl-1-hexene) was produced in both cases, but the polymerization of racemic 4MH promoted by the optically active catalysts preferentially consumed one antipode, showing some stereoselectivity for the process. [source] On the Cascade Polymerization Process Consisting of Metallocene Polymerization and ATRP to Prepare i -PP-Based Polar Block CopolymersMACROMOLECULAR REACTION ENGINEERING, Issue 2-3 2009Qingfeng Yi Abstract Isotactic poly(propylene)s bearing a terminal hydroxyl group (i -PP- t -OH) with high degrees of end-group functionality were synthesized by a metallocene/methylaluminoxane (MAO)-mediated propylene polymerization process via a preferential aluminium chain transfer reaction assisted by a hydroalumination process at the end of polymerization. Despite the highly isotactic configuration and relatively high molecular weight ( as high as 60,800 g,·,mol,1) of the polymers, the hydroxyl group located at the i -PP chain terminal was efficiently transformed to an atom transfer radical polymerization (ATRP) initiator moiety of i -PP- t -Br via a reaction with 2-bromopropionyl chloride at 60,°C in toluene. Well-defined i -PP- b -PMMA and i -PP- b -PS block copolymers of controllable structure and compositions were then prepared with efficient ATRPs of MMA and St using i -PP- t -Br. [source] Small and wide-angle X-ray scattering study of metallocene isotactic poly(propylene)JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000P.S. Dai We report a study of metallocene isotactic poly(propylene) (m-iPP) which crystallizes into , and , crystal modifications. Simultaneous in-situ small- and wide-angle X-ray scattering (SAXS and WAXS) were used to study kinetics during crystallization. Both techniques provide information about time development of crystallinity, while WAXS gives also kinetics of formation of , and , crystals. During the earliest stages of crystal formation, the SAXS Bragg peak occurs simultaneously, or slightly lags, the appearance of crystalline WAXS reflections. We conclude crystallization occurs by a nucleation and growth process in this m-iPP. [source] Synthesis and Structure,Efficiency Relations of 1,3,5-Benzenetrisamides as Nucleating Agents and Clarifiers for Isotactic Poly(propylene),MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2010Frank Abraham Abstract This paper presents the synthesis and properties of 1,3,5-benzenetrisamides with a particular focus on structure-efficiency relationships of nucleation and optical property enhancement of isotactic poly(propylene) (i -PP). A family of twenty 1,3,5-benzenetrisamide derivatives was synthesized, in which the direction of the amide linkage between the core and the peripheral substituents, as well as their length (C-3 to C-6) and flexibility were systematically varied. Dissolution- and recrystallization temperatures of the additives in the polymer melt, the crystallization temperature of i -PP, and the optical properties clarity and haze were determined in the additive concentration range from 200 to 2,500,ppm. Within the reported series of compounds, few exhibited very good nucleating and clarification abilities, only one with outstanding characteristics, whereas other, very closely related derivatives were found to be incapable to nucleate or clarify i -PP, although, intriguingly, most are structural isomers. We conclude that it is the particular chemical structure of the additive that determines its crystallization/self-assembly process, and, therewith, the structure of the heterogeneous nuclei, and at a higher hierarchical level the morphology of the poly(propylene) solid state and its final properties; and, hence, that a predictive understanding is still elusive. [source] Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2008Cristian Hedesiu Abstract Changes in phase composition and chain mobility in injection-molded isotactic poly(propylene), crystallized from the melt with slow cooling rate and subsequently quenched, associated with aging at temperature well above Tg for 150 and 1 000 h, are studied using time-domain 1H solid-state NMR and XRD. All sample exhibit physical aging when exposed to elevated temperatures, and the physical aging kinetics was observed to depend on the morphology of the homopolymer iPP and aging temperatures. The significant increase in the tensile modulus in time was observed for injection-molded iPP. The observed property changes induced by aging are attributed to microstructural changes within the semi-rigid and amorphous fractions. [source] Effect of Sample Configuration on the Morphology of Foamed LDPE/PP Blends Injection Molded by a Gas Counterpressure ProcessMACROMOLECULAR MATERIALS & ENGINEERING, Issue 6 2007Georgi Kotzev Abstract Blends of isotactic poly(propylene) and low-density polyethylene with different composition ratios were prepared through direct melt compounding on a twin-screw extruder. The specimens with various geometric configurations were injection-molded using a gas counterpressure process, using blends to which 0.5 wt.-% of a blowing agent was added. The influence of blend composition and specimen geometry on the structure and morphology of the samples was investigated by SEM and WAXS. The thermal behavior of the blends was analyzed by DSC. It was found that the morphology of each region depended on the composition ratio and specimen geometry. [source] Thermal Behavior of Isotactic Poly(propylene)/Maleated Poly(propylene) BlendsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2007Catalin Vīlcu Abstract This paper analyzes the thermal and thermo-oxidative degradation behavior, phase separation, melting, and crystallization of blends consisting of isotactic poly(propylene) (IPP) and poly(propylene) grafted with maleic anhydride (PP- g -MA). It has been established that, depending on the blend composition and crystallization/preparation procedure, the blends of IPP and PP- g -MA can either co-crystallize or evidence phase separation. This conclusion has been attained by comparing the DSC results of crystallization under dynamic and isothermal conditions with X-ray diffraction results. On the basis of the obtained results, the optimum mixing ratios have been established as 95,85 wt.-% IPP/5,15 wt.-% PP- g -MA. Thermo-oxidative behavior has been studied by thermogravimetry and differential thermal analysis. [source] Synthesis and Functionalization of Isotactic Poly(propylene) Containing Pendant Styrene GroupsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004Junfeng Zou Abstract Summary: Copolymerization of propylene and 1,4-divinylbenzene was successfully performed by a MgCl2 -supported TiCl4 catalyst, yielding isotactic poly(propylene) (i -PP) polymers containing a few pendant styrene groups. With a metalation reaction with butyllithium and a hydrochlorination reaction with dry hydrogen chloride, the pendant styrene groups were quantitatively transformed into benzyllithium and 1-chloroethylbenzene groups, respectively, which allowed the synthesis of i -PP-based graft copolymers by living anionic and atom transfer radical (ATRP) polymerization mechanisms. The incorporation of styrene pendant groups into isotactic poly(propylene) using a Zeigler,Natta catalyst gave functionalized polymers able to undergo living anionic and atom transfer radical (ATRP) polymerizations. [source] The Role of Allylanisole in Metallocene-Catalyzed Propylene Polymerization and Synthesis of End-Capped OligomersMACROMOLECULAR REACTION ENGINEERING, Issue 4 2008Muhammad Atiqullah Propylene was copolymerized with allylanisole (AA) using Me2Si(Ind)2ZrCl2 and Et(Ind)2ZrCl2, and the methylaluminoxane MAO cocatalyst at 70,°C and a cocatalyst to catalyst (Al:Zr) molar ratio of 1,000. It was fed at 8.5 bar(g). The weight-average molecular weight, , for both metallocenes decreased as the AA feed concentration increased. Therefore, allylanisole acted as an in situ chain transfer agent. The chain transfer constants, ktr/kp, of AA for Et(Ind)2ZrCl2 and Me2Si(Ind)2ZrCl2 turned out to be 0.33 and 0.40, respectively. The characterization of the resulting products by 1H NMR demonstrated that AA end-capped the isotactic poly(propylene) chains which showed to be low molecular weight oligomers; 4.96,×,103,,,,,,9.80,×,103. An appropriate chain transfer mechanism for AA has been proposed. [source] Encapsulation of magnetic self-assembled systems in thermoreversible gelsMACROMOLECULAR SYMPOSIA, Issue 1 2003Jean-Michel Guenet Abstract We describe two different ways of encapsulating within the fibrils of thermoreversible polymer gels the filaments of a supermolecular polymer formed by self-assembly of a bicopper complex. Heterogeneous nucleation is brought about with gels made from isotactic poly(styrene) while compound formation occurs with gels made from poly(hexyl isocyanate). These ways depend upon the interaction between the wings of the supermolecular polymer and the side groups of the polymer. In all cases, the filaments retain their 1-D structure. Preliminary results from magnetic susceptibility measurements show a striking difference between the pure and the encapsulated supermolecular polymer. [source] Effects of malonic acid treatment on crystal structure, melting behavior, morphology, and mechanical properties of isotactic poly(propylene)/wollastonite compositesPOLYMER COMPOSITES, Issue 6 2010Lin Li Wollastonite is treated with a new surface modifier (malonic acid). The influence of malonic acid treatment on the crystallization and mechanical properties of polypropylene (PP)/wollastonite composites has been studied. The results of differential scanning calorimetry, wide angle X-ray diffractometry, and polarized light microscopy prove that malonic acid-treated wollastonite increases the relative content of ,-crystal form of PP. The scanning electron microscopy shows that malonic acid-treated wollastonite has better compatibility with PP matrix than the untreated wollastonite. Higher ,-phase contents, smaller spherulite sizes, and better compatibility with PP matrix of the composites containing malonic acid-treated wollastonite result in improved impact strength and tensile strength, but lower flexural modulus. The results of Fourier transform infrared spectroscopy show that malonic acid reacts with the Ca2+ of wollastonite to form the calcium malonate, which acts as an effective ,-nucleating agent. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] Syndiotactic poly(propylene)/organoclay nanocomposite fibers: influence of the nano-filler and the compatibilizer on the fiber propertiesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2005Zita Mlynar, ķkovį Abstract Melt spinning of nanocomposites prepared from syndiotactic poly(propylene) (sPP) and organolayered silicate (M-ODA), containing bound octadecyl ammonium chains, was investigated. The influence of the nano-filler reinforcement and the role of the addition of maleic anhydride grafted isotactic poly(propylene) (iPP-g-MA) as compatibilizer with respect to the fiber proportion was examined. The presence of nano-filler, the drawing ratio, and the compatibilizer addition afforded increased tenacity of the fibers. Only in the presence of the compatibilizer high drawing ratio of the sPP nanocomposite fibers was achieved. Transmission electron microscopy (TEM) was applied to monitor morphology development during nanocomposite fiber spinning in the presence and the absence of the compatibilizer. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effects of SBS on phase morphology of iPP/aPS blendsPOLYMER ENGINEERING & SCIENCE, Issue 10 2000The supermolecular structure of binary isotactic polypropylene/poly(styrene- b -butadiene- h -styrene) (iPP/SBS) and isotactic polypropylene/atactic polystyrene (iPP/aPS) compression molded blends and that of ternary iPP/aPS/SBS blends were studied by optical microscopy, scanning and transmission electron microscopy, wide-angle X-ray diffraction and differential scanning calorimetry. Nucleation, crystal growth, solidification and blend phase morphology are affected by the addition of amorphous components (SBS and aPS). As a compatiblizer in immiscible iPP/aPS blends, SBS formed interfacial layer between dispersed honeycomb-like aPS/SBS particles and the iPP matrix, thus influencing the crystallization process in iPP. The amount of SBS and aPS, and compatibilizing efficiency of SBS, determine the size of dispersed aPS, SBS, and aPS/SBS particles and, consequently, the final blend phase morphologies: well-developed spherulitic morphology, cross-hatched structure with blocks of sandwich lamellae and co-continuous morphology. The analysis of the relationship between the size of spherulites and dispersed particles gave the criterion relation, which showed that, in the case of a well-developed spherulitization, the spherulites should be about fourteen times larger than the incorporated dispersed particles; i.e. to be large enough to engulf dispersed inclusions without considerable disturbing of the spherulitic structure. [source] | |||||||||||||