Home About us Contact
|
Home About us Contact | ||
|
|
||
Liquid Crystalline Polymers (liquid + crystalline_polymer)
Kinds of Liquid Crystalline Polymers Selected AbstractsPhotoluminescent Color and Polarized Light Emission Tuning of Fluorene Derivatives Using a Photoreactive H-Bonded Liquid Crystalline PolymerMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Nobuhiro Kawatsuki Abstract Three fluorene (FL) derivatives with pyridine end groups were synthesized to control the photoluminescence (PL) wavelength and polarized light emission using a photoreactive H-bonded polymer containing cinnamic acid side groups (P6CAM). The FL derivatives, which possessed pyridine end groups, formed H-bonds with cinnamic acid, and changed the PL behavior of the derivatives. The controllability ,max of the PL depended on the position of the N-atom at the pyridine end group and the degree of the photoreaction of the P6CAM. For F1, ,max of the PL was tuned from 470 to 518,nm. Employing P6CAM as the photoalignment layer to reorient the cinnamic acid side groups realized polarized PL up to PL||/PL,,=,3.9. Furthermore, photopatterning of the PL color and the direction of the polarized light emission using patterned P6CAM films were demonstrated. [source] Main-Chain Liquid Crystalline Polymers Based on Bis-Etherified 9,9-Dihexyl-2,7-bis(4,-hydroxy-1,1,-biphen-4-yl)fluorenesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 13 2007Tanja Sovi Abstract A series of liquid crystalline compounds based on 2,7-bis(biphenyl)fluorenes was synthesised by a Suzuki cross-coupling reaction and subsequent etherification with different bromoalkenes. By simple variations of the chain lengths the temperature range in which the nematic mesophase is present could be tuned. The described approach offers the possibility of covalent incorporation of the mesogens into polymers via olefin metathesis techniques, resulting in enlarged stability of the mesophase. Monomers and polymers could be easily aligned on rubbed polyimide substrates as revealed by polarised absorption spectroscopy. [source] Dynamic mechanical behavior of LCP fiber/glass fiber,reinforced LLDPE compositesPOLYMER COMPOSITES, Issue 2 2001S. A. R. Hashmi Liquid crystalline polymer (LCP) fibers and glass fibers have been used to rein force linear low density polyethylene (LLDPE) by using an elastic melt extruder and the compression molding technique. The impact behavior of hybrid composites of different composition is compared and is explained on the basis of the volume frac tion of the fibers. Addition of glass fibers decreases the Izod impact strength LLDPE. The impact strength of the composites increases when glass fibers are placed by LCP fibers. Dynamic mechanical , and , relaxations are studied and effect of variation of fiber composition on these relaxations is reported in the tem perature range from ,50 to 150°C at 1 Hz frequency, a relaxation shifts toward higher temperatures with addition of fibers in LLDPE. Addition of fibers increases the storage modulus of LLDPE. [source] Liquid-Crystalline Polymer with a Block Mesogenic Side Group: Photoinduced Manipulation of Nanophase-Separated StructuresADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Kunihiko Okano Abstract In this report, a novel type of photoresponsive liquid crystalline polymer with a block mesogenic side-group is demonstrated. The block mesogene is an amphipathic molecule containing a hydrophobic mesogene (azotolane moiety) and hydrophilic oligooxyethylene moieties in the same unit. The block mesogene in the polymer plays a role in liquid crystalline, amphiphilic and photoresponsive properties. As expected, a film prepared from the polymer exhibits phase separation of a lamellar structure due to cooperative motion between liquid crystal assembly and nanophase separation. The morphology of the lamellae can be aligned upon irradiation of linearly polarized light. Moreover, a photochemical phase transition induced by unpolarized UV irradiation erases the surface morphology. The erased nanostructure can be recovered by annealing or irradiation of linearly polarized light, meaning that the surface morphology is rewritable via a photochemical process. [source] On the flow-phase diagram for nematic liquid crystalline polymer under magnetic fieldJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009Shufang Fu Abstract The effect of magnetic fields on molecular configuration of liquid crystalline polymers under shear flows are numerically analyzed using the extended Doi theory in which a molecular shape parameter is admitted. The evolution equation for the probability density function of the LCP molecules is directly solved without any closure approximations. One case is considered that the magnetic field makes 45° with respect to the flow direction. We can find that the magnetic fields strongly affect on the transition among flow-orientation modes, such as tumbling, wagging, and aligning modes. And a new aligning flow-orientation mode emerges at low shear rate, which is macroscopically same as the ordinary aligning mode, but is microscopically quite different from the ordinary one. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Carboxylated multiwall carbon nanotube-reinforced thermotropic liquid crystalline polymer nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Sang Ki Park Abstract Thermotropic liquid crystalline polymer (TLCP) nanocomposites reinforced with carboxylated multiwall carbon nanotube (c-MWCNT) were prepared through melt compounding in a twin screw extruder. The thermal stability of TLCP/c-MWCNT nanocomposites increased with even a small amount of c-MWCNT added. The rheological properties of the TLCP/c-MWCNT nanocomposites were depended on the c-MWCNT contents. The contents of c-MWCNT have a slight effect on the complex viscosity of TLCP/c-MWCNT nanocomposites due to the high-shear thinning of TLCP. The storage modulus of TLCP/c-MWCNT nanocomposites was increased with increasing c-MWCNT content. This result can be deduced that the nanotube,nanotube interactions were more dominant, and some interconnected or network-like structures were formed in the TLCP/c-MWCNT nanocomposites. Incorporation of very small amount of c-MWCNT improved the mechanical properties of TLCP/c-MWCNT nanocomposites, and this was attributed to the reinforcement effect of c-MWCNT with high aspect ratio and their uniform dispersion through acid treatment in the TLCP matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Tailoring the liquid crystalline property via controlling the generation of dendronized polymers containing azobenzene mesogenJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2010Chang-An Yang Abstract The first- and second-generation dendronized polymers containing azobenzene mesogen were designed and successfully synthesized via free radical polymerization. The chemical structures of the monomers were confirmed by elemental analysis, 1H NMR, and 13C NMR. The molecular characterizations of the polymers were performed with 1H NMR and gel permeation chromatography. The phase structures and transition behaviors were studied using differential scanning calorimetry, polarized light microscopy, and small-angle X-ray scatter experiments. The experiment results revealed that the first-generation dendronized polymer exhibited liquid crystalline behavior of the conventional side-chain liquid crystalline polymer with azobenzene mesogen, that is, the polymer exhibited smectic phase structure at lower temperature and nematic phase structure at higher temperature. However, the second-generation dendronized polymers exhibited more versatile intriguing liquid crystalline structures, namely smectic phase structure at lower temperature and columnar nematic phase structure at higher temperature, and moreover, the phase structure still remained before the decomposition temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1149,1159, 2010 [source] In situ reinforcement of poly(butylene terephthalate) and butyl rubber by liquid crystalline polymerPOLYMER COMPOSITES, Issue 5 2009S. Kumar Ternary in situ butyl rubber (IIR)/poly(butylene terephthalate) (PBT) and liquid crystalline polymer (LCP) blends were prepared by compression molding. The LCP used was a versatile Vectra A950, and the matrix material was IIR/PBT 50/50 by weight. Morphological, thermal, and mechanical properties of blends were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry, and thermogravimetric analysis (TGA). Microscopy study (SEM) showed that formation of fibers is increasing with the increasing amount of LCP A950. Microscopic examination of the fractured surface confirmed the presence of a polymer coating on LCP fibrils. This can be attributed to some interactions including both chemical and physical one. The increased compatibility in polymer blends, consisting of IIR/PBT, by the presence of LCP A950 may be explained by the adsorption phenomena of the polymer chains onto the LCP fibrils. SEM and AFM images provided the evidence of the interaction between IIR/PBT and the LCP. Dynamic mechanical analyses (DMA) and TGA measurements showed that the composites possessed a remarkably higher modulus and heat stability than the unfilled system. Storage modulus for the ternary blend containing 50 wt% of LCP exhibits about 94% increment compared with binary blend of IIR/PBT. From the above results, it is suggested that the LCP A950 can act as reinforcement agent in the blends. Moreover, the fine dispersion of LCP was observed with no extensional forces applied during mixing, indicating the importance of interfacial adhesion for the fibril formation. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Compatibilizing effect of ethylene,propylene,diene grafted maleic anhydride terpolymer on the blend of polyamide 66 and thermal liquid crystalline polymerPOLYMER COMPOSITES, Issue 6 2006Qunfeng Yue Polyamide 66,thermal liquid crystalline polymer (PA66/TLCP) composites containing 10 wt% TLCP was compatibilized by ethylene,propylene,diene-grafted maleic anhydride terpolymer (MAH- g -EPDM). The blending was performed on a twin-screw extrusion, followed by an injection molding. The rheological, dynamic mechanical analysis (DMA), thermal, mechanical properties, as well as the morphology and FTIR spectra, of the blends were investigated and discussed. Rheological, DMA, and FTIR spectra results showed that MAH- g -EPDM is an effective compatibilizer for PA66/TLCP blends. The mechanical test indicated that the tensile strength, tensile elongation, and the bending strength of the blends were improved with the increase of the content of MAH- g -EPDM, which implied that the blends probably have a great frictional shear force, resulting from strong adhesion at the interface between the matrix and the dispersion phase; while the bending modulus was weakened with the increase of MAH- g -EPDM content, which is attributed to the development of the crystalline phase of PA66 hampered by adding MAH- g -EPDM. POLYM. COMPOS., 27:608,613, 2006. © 2006 Society of Plastics Engineers [source] Kinetic analysis of thermo-oxidative degradation of PEEK/thermotropic liquid crystalline polymer blendsPOLYMER ENGINEERING & SCIENCE, Issue 2 2006M. Naffakh The thermal degradation behavior of blends of poly(aryl ether ether ketone), PEEK, with a thermotropic liquid crystalline polymer (TLCP), Vectraź, were investigated in an oxidative atmosphere, using thermogravimetric analysis under dynamic conditions. The theoretical weight loss curves of the blends were compared with the experimental curves in order to explain the effect of blending on the thermal stability of the pure polymers. The thermo-oxidative degradation of PEEK/Vectraź blends of different compositions takes place in various steps and the characteristic degradation temperatures and the kinetic parameters such as activation energy are strongly influenced by blending. Polymer blends based on this TLCP polymer had not been previously studied from kinetic viewpoint. POLYM. ENG. SCI. 46:129,138, 2006. © 2005 Society of Plastics Engineers [source] The rotational molding of a thermotropic liquid crystalline polymerPOLYMER ENGINEERING & SCIENCE, Issue 3 2005Eric Scribben Thermotropic liquid crystalline polymers (TLCPs) exhibit a number of mechanical and physical properties such as excellent chemical resistance, low permeability, low coefficient of thermal expansion, high tensile strength and modulus, and good impact resistance, which make them desirable as a rotationally molded storage vessel. However, there are no reports in the technical literature of the successful rotational molding of TLCPs. In this article, conditions are identified that lead to the successful rotational molding of a TLCP, Vectra B 950. First, a technique was developed to produce particles suitable for rotational molding because TLCPs cannot be ground into a free-flowing powder. Second, because the viscosity at low shear rates can be detrimental to the sintering process, coalescence experiments with isolated particles were carried out to determine the thermal and environmental conditions at which sintering should occur. These conditions were then applied to static sintering experiments to determine whether coalescence and densification of the bulk powder would occur. Finally, the powders were successfully rotationally molded into tubular structures in a single axis, lab-scale device. The density of the molded structure was essentially equivalent to the material density and the tensile strength and modulus were approximately 18 MPa and 2 GPa, respectively. POLYM. ENG. SCI., 45:410,423, 2005. © 2005 Society of Plastics Engineers [source] Thermal properties of biaxially deformed in situ compositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2004Youngwook P. Seo The thermal properties of biaxially blown poly(etherimide) (PEI) films containing a thermotropic liquid crystalline polymer (TLCP) were studied using differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction and dynamic mechanical thermal analysis. The effects of the compatibilizer and thermal annealing on the thermal properties of biaxially oriented TLCP films were investigated. Though the compatibilizer (poly(ester imide)) improved deformation of the TLCP phase (poly ester amide) and adhesion between the matrix and the TLCP phase, which improved mechanical properties, it did not significantly affect the thermal properties of the in situ composite films. The film degradation behavior corroborated the role of the compatibilizer. Since a relatively small amount of TLCP (10 wt%) was added to the matrix and the matrix PEI was amorphous, the effect of annealing on the TLCP structure was not obvious. By the same token, while the effect of the deformation in the circumferential direction (a change in the blow-up ratio) was manifest in mechanical property improvements, its effect on the thermal properties was not obvious. All films showed similar thermal expansion behaviors, regardless of the thermal history and of the compatibilizer addition. Thus, there is an optimum amount of the compatibilizer required to obtain optimal mechanical properties for in situ composite films without causing a deterioration of their thermal properties. Polym. Eng. Sci. 44:1419,1428, 2004. © 2004 Society of Plastics Engineers. [source] Crystallization and melting behavior of zenite thermotropic liquid crystalline polymers,POLYMER ENGINEERING & SCIENCE, Issue 2 2002K. P. Pramoda The crystallization and melting behavior of a DuPont ZeniteTM series, namely, Z 6000 and Z 8000B, thermotropic liquid crystalline polymer (TLCP) have been investigated by differential scanning calorimetry (DSC). Both, non-isothermal and isothermal crystallizations were carried out. From the non-isothermal experiments, the crystallization temperature was found to be 234°C for a cooling rate of 10°C/min whereas it was only 228°C for 40°C/min for Z 8000B, and was found to be 296°C and 290°C, respectively, for Z 6000. In the isothermal experiment both the thermal and crystallization behaviors were studied as a function of the annealing temperature and annealing time. Two types of transition processes were evidence in the low temperature region of the isothermal crystallization. One is fast transition, which may be regarded as liquid crystal transition, and is characterized by the enthalpy, which is independent of annealing time. The other is slow process, related to crystal perfection, and it shows increases in the transition temperature and enthalpy, which is dependent on annealing time. [source] Barrier properties of blends based on liquid crystalline polymers and polyethylenePOLYMER ENGINEERING & SCIENCE, Issue 9 2000G. Flodberg Blends of an extrusion-grade polyethylene and two different liquid crystalline polymers of Vectra type were prepared by melt mixing using poly(ethylene-comethacrylic acid) as compatibilizer. Oxygen and water vapor permeability, transparency and welding strength of compression molded and film blown specimens were studied. The compression molded blends showed gas permeabilities conforming to the Maxwell equation assuming low permeability liquid crystalline polymer spheres in a high permeability polyethylene matrix. One of the liquid crystalline polymers with suitable rheological properties formed a more continuous phase in the film blown blends and a substantial decrease in oxygen and water vapor permeability was observed in these blends. The compression molded blends with 50% liquid crystalline polymer and some of blow molded blends showed very high gas permeabilities. It is believed that voids forming continuous paths through the structure were present in these samples. The blends showed significantly higher opacity than pure polyethylene. [source] Thermal properties, structure and morphology of PEEK/thermotropic liquid crystalline polymer blendsPOLYMER INTERNATIONAL, Issue 12 2003Mohammed Naffakh Abstract The dynamic crystallization and subsequent melting behaviour of poly(aryl ether ether ketone), PEEK, and its blends with a thermotropic liquid crystalline polymer, Vectraź, have been studied using differential scanning calorimetry, optical microscopy and wide-angle and small-angle X-ray diffraction (WAXS and SAXS) techniques in a wide compositional range. Differences in crystallization rates and crystallinities were related to the structural and morphological characteristics of the blends measured by simultaneous real-time WAXS and SAXS experiments using synchrotron radiation and optical microscopy. The crystallization process of PEEK in the blends takes place in the presence of the nematic phase of Vectra and leads to the formation of two different crystalline families. The addition of Vectra reduces the crystallization rate of PEEK, depending on composition, and more perfect crystals are formed. An increase in the long period of PEEK during heating was generally observed in the blends at all cooling rates. Copyright © 2003 Society of Chemical Industry [source] Specific Functionalization of Carbon Nanotubes for Advanced Polymer NanocompositesADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Nanda Gopal Sahoo Abstract A novel approach to chemically functionalize multiwalled carbon nanotubes (MWCNTs) for making advanced polymeric nanocomposites with liquid crystalline polymers (LCPs) is presented. In this approach, two types of chemical moieties (i.e., carboxylic and hydroxyl benzoic acid groups) are selectively introduced onto the sidewalls of the MWCNTs. Fourier transform IR and Raman spectroscopy are used to examine the interaction between the functionalized MWCNTs and the LCP. The strong interaction between the functionalized MWCNTs and the LCP greatly improved the dispersion of MWCNTs in the polymer matrix as well as the interfacial adhesion. The dispersion of the MWCNTs in the LCP matrix is observed by optical microscopy and field-emission scanning electron microscopy. As a result, the addition of 1,wt% MWCNTs in the LCP resulted in the significant improvement (41 and 55%) in the tensile strength and modulus of the LCP. [source] On the flow-phase diagram for nematic liquid crystalline polymer under magnetic fieldJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009Shufang Fu Abstract The effect of magnetic fields on molecular configuration of liquid crystalline polymers under shear flows are numerically analyzed using the extended Doi theory in which a molecular shape parameter is admitted. The evolution equation for the probability density function of the LCP molecules is directly solved without any closure approximations. One case is considered that the magnetic field makes 45° with respect to the flow direction. We can find that the magnetic fields strongly affect on the transition among flow-orientation modes, such as tumbling, wagging, and aligning modes. And a new aligning flow-orientation mode emerges at low shear rate, which is macroscopically same as the ordinary aligning mode, but is microscopically quite different from the ordinary one. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Synthesis and properties of mesogen-jacketed liquid crystalline polymers containing bistolane mesogenJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Zhen Lin Zhang Abstract On the basis of the concept of mesogen-jacketed liquid crystalline polymers, a series of new methacrylate monomers, (2,5- bis[2-(4,-alkoxyphenyl) ethynyl] benzyl methacrylate (MACn, n = 4, 6, 8, 10, and 12) and 2,5- bis[2-(6,-decanoxynaphthyl) ethynyl] benzyl methacrylate (MANC10), and their polymers, PMACn (n = 4, 6, 8, 10, and 12) and PMANC10 were synthesized. The bistolane mesogen with large ,-electron conjugation were side-attached to the polymer backbone via short linkages. Various characterization techniques such as differential scanning calorimetry, wide-angle X-ray diffraction, and polarized light microscopy were used to study their mesomorphic phase behavior. The polymer PMACn with shorter flexible substituents (n = 4) forms the columnar nematic (,N) phase, but other polymers with longer flexible tails (n = 6, 8, 10, and 12) can develop into a smetic A (SA) phase instead of a ,N phase. The PMANC10 containing naphthyl can also form a well-defined SA phase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Synthesis and characterization of side-chain liquid crystalline polymers bearing cholesterol mesogenJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2009Suk-Kyun Ahn Abstract A series of new norbornene carboxylic cholesteryl ester monomers with and without alkyl spacers, NBCh, and NBCh-n, respectively, were synthesized. New side-chain liquid crystalline homopolymers, PNBCh and PNBCh-n, were cleanly prepared using NBCh and NBCh-n, respectively, with Grubbs 2nd generation catalyst. Molecular and structural characterization of monomers and polymers were carried out by nuclear magnetic resonance, NMR, Fourier transform infrared, FT-IR, spectroscopy, and gel permeation chromatography, GPC. The thermal and liquid crystalline properties of the homopolymers were investigated by differential scanning calorimetry, DSC, thermogravimetric analysis, TGA, and polarized optical microscopy, POM. Small angle and wide angle X-ray studies of PNBCh-n in powder and fiber states not only confirmed the formation of smectic A mesophases, but also established their morphologies. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2690,2701, 2009 [source] Jacketed polymers: Controlled synthesis of mesogen-jacketed polymers and block copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2009Long-Cheng Gao Abstract The controlled radical polymerization of mesogen-jacketed liquid crystalline polymers has triggered great interests in synthesis of complex structures as well as well-defined linear homopolymers with controlled molecular weight and narrow molecular weight distributions. This review highlights the synthetic strategies of controlled radical polymerization of linear homopolymers, star polymers, superbranched polymers, graft polymers, block copolymers, star block copolymers, and so on. The employed living methods include nitroxide-mediated radical polymerization and atom transfer radical polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 319,330, 2009 [source] Photoinduced Microphase Separation in Block Copolymers: Exploring Shape Incompatibility of Mesogenic Side GroupsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2010Yi Zhao Abstract Photoinduced microphase separation in block copolymers (BCP) was achieved for the first time, using a rationally designed diblock copolymer composed of two side-chain liquid crystalline polymers (SCLCP). The miscibility of the two blocks was promoted by the miscibility between the two types of mesognic side groups, while upon UV exposure inducing the trans,cis isomerization of azobenzene mesogens on one SCLCP, the shape incompatibility of bent cis isomers with an ordered liquid crystalline phase drove the separation of the two blocks resulting in a microphase separated morphology. This result shows the perspective of using light to process and organize BCP morphology and related nanostructures in a lithography-free manner. [source] Properties of films from polypropylene and thermotropic liquid crystalline polymer blendsPOLYMER COMPOSITES, Issue 3 2000L. Incarnato In this paper the effect of the inclusion of two different thermotropic liquid crystalline polymers, namely Rodrun 3000 and Vectra A950, in a PP matrix is analyzed with particular attention to the gas transport and mechanical properties of the extruded blend films. The experiments, conducted on PP/Rodrun 3000 and PP/Vectra A950 films, have shown that the presence of TLCPs, also at low percentages, modify the properties of the thermoplastic matrix in a manner depending on the degree of compability and interfacial adhesion between the two components of the blends. Moreover, the effect of a maleic anhydride grafted PP (MAP), used as compatibilizing agent, on the properties and morphology of the PP/Rodrun 3000 system was examined. It was found that the addition of the MAP determines an increase in the barrier properties and in toughness of the films compared to those without MAP. [source] The rotational molding of a thermotropic liquid crystalline polymerPOLYMER ENGINEERING & SCIENCE, Issue 3 2005Eric Scribben Thermotropic liquid crystalline polymers (TLCPs) exhibit a number of mechanical and physical properties such as excellent chemical resistance, low permeability, low coefficient of thermal expansion, high tensile strength and modulus, and good impact resistance, which make them desirable as a rotationally molded storage vessel. However, there are no reports in the technical literature of the successful rotational molding of TLCPs. In this article, conditions are identified that lead to the successful rotational molding of a TLCP, Vectra B 950. First, a technique was developed to produce particles suitable for rotational molding because TLCPs cannot be ground into a free-flowing powder. Second, because the viscosity at low shear rates can be detrimental to the sintering process, coalescence experiments with isolated particles were carried out to determine the thermal and environmental conditions at which sintering should occur. These conditions were then applied to static sintering experiments to determine whether coalescence and densification of the bulk powder would occur. Finally, the powders were successfully rotationally molded into tubular structures in a single axis, lab-scale device. The density of the molded structure was essentially equivalent to the material density and the tensile strength and modulus were approximately 18 MPa and 2 GPa, respectively. POLYM. ENG. SCI., 45:410,423, 2005. © 2005 Society of Plastics Engineers [source] An experimental study of morphology and rheology of ternary Pglass-PS-LDPE hybridsPOLYMER ENGINEERING & SCIENCE, Issue 6 2003Peter C. Guschl Ternary blends of low-density polyethylene (LDPE), polystyrene (PS), and a low Tg tin-based phosphate glass (Pglass) were prepared at compositions ranging from 0,50 vol% Pglass in which either LDPE or PS was the continuous matrix phase. Differential scanning calorimetry was used to investigate the phase behavior of the pure components, PS-LDPE blends and binary Pglass-polymer hybrids. Interesting steady-shear and transient rheology was observed for the hybrids. In particular, the steady shear viscosity curves for the hybrids of ,Pglass , 30% exhibited unusual, four-region flow behavior, similar to that of liquid crystalline polymers. Two Newtonian plateaus at low ( , 0.1 s,1) and moderate (0.4 , , s,1) shear rates connected by two distinct shear-thinning regimes were apparent. This observed rheology is ascribed to a unique composite morphology of these multi-component systems. Rheological data on the binary Pglass-polymer systems suggest that the presence of the Pglass within both PS and LDSE contributes significantly to this unusual behavior, perhaps because of the interfacial behavior between the phases. Micrographs obtained via scanning electron microscopy reveal preferential placement of the Pglass phase dispersed within the PS-phase and surrounding the LDPE phase. Optical shearing data confirmed the evolution of this microstructure under specific shear conditions. [source] Crystallization and melting behavior of zenite thermotropic liquid crystalline polymers,POLYMER ENGINEERING & SCIENCE, Issue 2 2002K. P. Pramoda The crystallization and melting behavior of a DuPont ZeniteTM series, namely, Z 6000 and Z 8000B, thermotropic liquid crystalline polymer (TLCP) have been investigated by differential scanning calorimetry (DSC). Both, non-isothermal and isothermal crystallizations were carried out. From the non-isothermal experiments, the crystallization temperature was found to be 234°C for a cooling rate of 10°C/min whereas it was only 228°C for 40°C/min for Z 8000B, and was found to be 296°C and 290°C, respectively, for Z 6000. In the isothermal experiment both the thermal and crystallization behaviors were studied as a function of the annealing temperature and annealing time. Two types of transition processes were evidence in the low temperature region of the isothermal crystallization. One is fast transition, which may be regarded as liquid crystal transition, and is characterized by the enthalpy, which is independent of annealing time. The other is slow process, related to crystal perfection, and it shows increases in the transition temperature and enthalpy, which is dependent on annealing time. [source] Blends of two thermotropic liquid crystalline polymers: The influence of reactions during injection molding on the phase structure and the mechanical behaviorPOLYMER ENGINEERING & SCIENCE, Issue 7 2001F. J. Vallejo Blends of two different thermotropic liquid crystalline polymers, poly(p-hydroxy benzoic acid-co-2, 6-hydroxy naphthoic acid), VA, and poly(p-hydroxybenzoic acid-co-terephthalic acid-co-aminophenol), VB, were obtained by direct injection molding throughout the full composition range. The blends were almost fully immiscible apart from a low degree of reaction. This, as well as the nature of the blends, probably influenced their mechanical properties. Enhanced properties were obtained both in the modulus of elasticity and in the tensile strength, at all the compositions studied, with absolute maxima at VB contents between 50% and 75%. These synergisms were mainly due to a greater orientation of the components in the blends than in the pure components. [source] Barrier properties of blends based on liquid crystalline polymers and polyethylenePOLYMER ENGINEERING & SCIENCE, Issue 9 2000G. Flodberg Blends of an extrusion-grade polyethylene and two different liquid crystalline polymers of Vectra type were prepared by melt mixing using poly(ethylene-comethacrylic acid) as compatibilizer. Oxygen and water vapor permeability, transparency and welding strength of compression molded and film blown specimens were studied. The compression molded blends showed gas permeabilities conforming to the Maxwell equation assuming low permeability liquid crystalline polymer spheres in a high permeability polyethylene matrix. One of the liquid crystalline polymers with suitable rheological properties formed a more continuous phase in the film blown blends and a substantial decrease in oxygen and water vapor permeability was observed in these blends. The compression molded blends with 50% liquid crystalline polymer and some of blow molded blends showed very high gas permeabilities. It is believed that voids forming continuous paths through the structure were present in these samples. The blends showed significantly higher opacity than pure polyethylene. [source] Electrorheological Effect of "Side-on" Liquid Crystalline PolysiloxaneCHEMPHYSCHEM, Issue 17 2008Kosuke Kaneko Dr. Electric field and viscosity: In expectation of a large electrorheological (ER) effect, the authors study a side-on liquid crystalline polysiloxane compound and demonstrate that a larger ER effect occurs in the low-viscosity nematic phase of "side-on" liquid crystalline polymers (LCPs) as compared to "side-end" LCPs (see figure). [source] | ||||||||||