Enhanced fibrillation of LCP by CaCO3 whisker in polysulfone matrix through increasing elongational stress

Induced by different fillers, various hydrodynamic effects enhance the fibrillation of liquid crystalline polymer (LCP) in in situ hybrid composites. Through choosing CaCO₃ whisker as the filler and polysulfone (PSF) as the matrix, the effect of the filler size and the affinity between components on the morphological evolution of LCP droplets has been investigated. In contrast to the spherical or ellipsoidal droplets of LCP formed in binary PSF/LCP blends, the fibrillation of LCP was promoted by the introduction of whisker particles in all ternary blends at shear rates studied. The analysis of the flow field indicated that the predominant factors promoting the fibrillation of LCP were the vortex enhanced and elongational stress increased by the whisker in the converging flow area at the entrance of capillary, rather than the viscosity ratio and capillary number.     

Experimental measurement and numerical simulation of viscosity reduction effects in HMMPE containing a small amount of exfoliated organoclay-modified TLCP composite

A small amount (1 wt%) of organoclay-modified thermotropic liquid crystalline polymer (TLCP) acting as a viscosity reduction agent in high molecular mass polyethylene (HMMPE) was characterized and compared with purified TLCP (1 wt%) in HMMPE at 190 °C and 230 °C, respectively, where the TLCP displayed nematic and nematic-isotropic biphase structures. In the TLCP/PE blend at 190 °C and 230 °C, dramatic reductions in viscosity were observed with significant improvement in extrudate surface smoothness and an enlarged processing window. For the organoclay-modified TLCP in PE, the viscosity reduction ability of TLCP was further enhanced with viscosity dropped by up to >98.5% and >97.4% at 190 °C and 230 °C and processing window enlarged to >700 s⁻¹ and >900 s⁻¹ respectively in comparison to that of PE. Moreover, yielding stress, initial transition shear rate and transition region decreased to lower magnitudes than those of the TLCP/PE blend. A phenomenological model was applied to elucidate the mechanism of organoclay, TLCP and PE conformation before and after yielding in the confined capillary environment. A binary flow pattern model was applied to successfully predict the rheological behavior of the blends at 190 °C.     

液晶高分子分子设计及合成方法的研究进展

综述了液晶高分子(LCP)分子设计的一般原则及其合成方法。着重介绍了热致主链型LCP、溶致主链型LCP及侧链LCP的分子设计与合成技术,并列举了国内外各种类型LCP的合成研究先例。     

Transport and adhesion properties of an unlined and a liquid‐crystalline polymer–lined vinyl ester thermoset exposed to severe environments

The application of liquid‐crystalline polymers (LCP) as lining materials for fiber‐reinforced plastics was investigated. The lining consisted of one uniaxially and one biaxially oriented LCP and, for comparison, a fluorinated ethylene propylene copolymer. The lining was attached to a glass‐fiber–reinforced vinyl ester thermoset. The laminates were examined with respect to their chemical resistance, transport/barrier properties, and lining/matrix adhesion behavior. The transport properties were determined by gravimetric desorption measurements and cup tests. It was shown that the LCP was suitable as a lining in organic solvent and nonoxidizing acid environments. Diffusivities, equilibrium concentrations, and transmission rates of water, methanol, toluene, and trichloroethylene were obtained in the LCP, the fluorinated ethylene propylene copolymer, and also, in the case of the vinyl ester, of hydrochloric acid. In general, the diffusivity and transmission rate in the LCP were one to several orders of magnitude lower than those of the fluorinated ethylene propylene copolymer and the vinyl ester. The reinforcement in the glass‐fiber–reinforced plastic led to an increase in the water and methanol diffusivities and transmission rates, which was probably attributable to liquid capillary diffusion. The lap‐shear bonding strength between the LCP and the vinyl ester was poor, but it was improved almost sixfold by a combined abrasive and oxygen plasma treatment. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 797–806, 2005     

Evolution of the morphological and rheological properties along the extruder length for compatibilized blends of a commercial liquid‐crystalline polymer and polypropylene

In a previous article, we reported on the evolution of the morphological and rheological properties along the length extruder for blends of a liquid‐crystalline polymer (LCP), Rodrun LC3000, and polypropylene (PP). In this work, we extended this study to compatibilized PP/Rodrun LC3000 blends, containing 10 wt % LCP and different compatibilizers, to determine the influence of the addition of a compatibilizer during the processing and, consequently, on the final properties of such systems. The results revealed that the addition of compatibilizers led to a decrease in the mean diameters of the LCP structures, in comparison with those presented by the noncompatibilized blend containing the same LCP content. This phenomenon occurred more quickly for those blends in which compatibilization was carried out in an efficient way. Linear oscillatory shear was mainly sensitive to the type of morphology present in the blends, whereas nonlinear oscillatory shear was more sensitive to the evolution in the droplet/fibril size and along the extruder length. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 347–359, 2006     

Formation and morphologies of ethylcyanoethyl cellulose/poly(ε‐caprolactone) blending films

The texture of ethylcyanoethyl cellulose [(ECE)C]/poly(ε‐caprolactone) (PCL)/dichloroacetic acid (DCA) solutions and the morphology of the (ECE)C/PCL blending films were studied by polarizing optical microscope. The critical concentration of the (ECE)C/PCL/DCA solutions, at which the mesophase began to appear, was not influenced by the addition of PCL molecules, and the evolution of the cholesteric texture varied with different contents of PCL in the blends. Spherulites with a ringed extinction pattern in the (ECE)C/PCL blending films were formed below an (ECE)C concentration of 25 wt %. Moreover, the bright band distance of the alternative ringed extinction pattern decreased with increasing (ECE)C concentration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 550–554, 2004     

Synthesis and liquid‐crystalline properties of poly(4‐vinylpyridinium) bromides N‐substituted with dialkyloxyterphenyl groups

Poly(4‐vinylpyridine)s (P4VPs) fully and partially quaternized with dialkyloxyterphenyl groups were synthesized and characterized. These new polymers developed both liquid‐crystalline (LC) properties and a light emission (luminescence) in the blue region. The mesomorphic behavior of the polymers was initially characterized by differential scanning calorimetry and polarizing optical microscopy and was further corroborated by X‐ray diffraction analyses. The X‐ray diffraction patterns showed in the low‐angles region several equidistant diffraction peaks (d₀₀₁, d₀₀₂, d₀₀₃, …) and in the wide‐angles region a broad peak typical of nonordered mesophases. From d₀₀₁ and the length of the monomers, we deduced that the molecular arrangement in the mesophase corresponded to a double‐layered stacking of molecules with mesogens tilted with respect to the smectic plane and the backbones sandwiched between. In this arrangement, the different parts of mesogens are segregated from one another in layered domains. The longer smectic periods observed for copolymers indicated that the nonsubstituted pyridine cycles were sandwiched between two smectic layers. The emission spectra of these polymers were characterized by a broad signal centered at 365 nm. The combination of LC properties with luminescence in the polymers is interesting for the preparation of thin films with aligned emitters, particularly for linearly polarized light emission. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

In situ compatibilization of PEN/LCP blends by ultrasonic extrusion

In situ compatibilization of immiscible blends of PEN and thermotropic LCP was achieved by the ultrasonically‐aided extrusion process. Ultrasonically‐treated PEN underwent degradation, leading to a decrease of its viscosity. Viscosity of LCP was unaffected by ultrasonic treatment. Because of reduced viscosity ratio of PEN to LCP at high amplitude of ultrasonic treatment, larger LCP domains were observed in molding of the blends. LCP acted as a nucleating agent, promoting higher crystallinity in PEN/LCP blends. Ultrasonically‐induced copolymer formation was detected by MALDI‐TOF mass spectrometry in the blends. Ultrasonic treatment of 90/10 PEN/LCP blends improved interfacial adhesion in fibers spun at intermediate draw down ratios (DDR), improving their ductility. The lack of improvement in the mechanical properties of fibers spun at high DDR after ultrasonic treatment was attributed to the disturbance of interfacial copolymer by high elongation stresses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Organoclay/thermotropic liquid crystalline polymer nanocomposites. Part VI: Effects of intercalated organoclay on nanocomposite morphology,thermal and rheological properties

A study of a typical intercalated structure of a thermotropic liquid crystalline polymer (TLCP) with organoclay was performed to elucidate the influence of intercalated organoclay on the TLCP molecules, especially on their liquid crystallinity, thermal and rheological properties. The intercalated structures were confirmed in TLCP and organoclay formed molecular interactions with TLCP molecules in the system. Such intercalated structures caused the glass transition temperature of the nanocomposite to become invisible in thermal measurement and also caused loss of liquid crystallinity. The TLCP molecules inside the organoclay galleries showed higher thermal stability and transition temperatures, but the orderly structure of the TLCP molecules outside the galleries was destroyed by the organoclay, causing the TLCP to display lower thermal stability and transition temperatures than pristine TLCP. At 185°C, where TLCP is in the nematic phase, the nanocomposite had three orders of magnitude higher viscosity in the linear viscoelastic region than that of TLCP, with chain mobility and relaxation time slowed due to the intercalated effects in the nanocomposite. Steady shear altered the domain sizes and oriented the highly anisotropic organoclay layers or tactoids along the shear direction.     

由芳香族聚酯LCP废弃物回收4,4′-联苯二酚

以1,4-二氧六环为溶剂,NaOH为催化剂,对废弃的含4,4'-联苯二酚(BP)单元的芳香族聚酯型液晶高分子(LCP),在常压下通过水解反应回收制备4,4'-联苯二酚进行了研究。在反应混合物的质量比m(LCP)∶m(溶剂)∶m(H2O)∶m(NaOH)=1∶4∶1.5∶0.6的最优条件下,液晶高分子的水解率达97%以上。通过在水解液中加入HCl并控制其pH在8.5,沉淀得到4,4'-联苯二酚。4,4'-联苯二酚经水洗、干燥、甲醇重结晶后,液相色谱检测其纯度可达99.9%,从废弃液晶高分子中制备4,4'-联苯二酚的收率为70%。