Thermotropic Liquid Crystalline Polymer Research Articles

Mechanical Properties of 3D-Printed Liquid Crystalline Polymers with Low and High Melting Temperatures.

Additive manufacturing allows for the production of complex components using various types of materials such as plastics, metals and ceramics without the need for molding tools. In the field of high-performance polymers, semi-crystalline polymers such as polyetheretherketone (PEEK) or amorphous polymers such as polyetherimide (PEI) are already successfully applied. Contrary to semi-crystalline and amorphous polymers, thermotropic liquid crystalline polymers (LCPs) do not change into an isotropic liquid during melting. Instead, they possess anisotropic properties in their liquid phase. Within the scope of this work, this special group of polymers was investigated with regard to its suitability for processing by means of fused filament fabrication. Using an LCP with a low melting temperature of around 280 °C is compared to processing an LCP that exhibits a high melting temperature around 330 °C. In doing so, it was revealed that the achievable mechanical properties strongly depend on the process parameters such as the direction of deposition, printing temperature, printing speed and layer height. At a layer height of 0.10 mm, a Young's modulus of 27.3 GPa was achieved. Moreover, by employing an annealing step after the printing process, the tensile strength could be increased up to 406 MPa at a layer height of 0.15 mm. Regarding the general suitability for FFF as well as the achieved uniaxial mechanical properties, the LCP with a low melting temperature was advantageous compared to the LCP with a high melting temperature.

Thermal conductivity and orientation of liquid crystal polymer filled with boron nitride

This work focuses on the study of effect of hexagonal boron nitride (BN) on the self-orientation, rheology and thermal conductivity of thermotropic liquid crystalline polymer (LCP), which possesses a semirigid-rod molecular structure. The LCP/BN composites are prepared by extrusion and injection molding processes. The 2D-WAXD analysis evidences the presence of self-orientation and typical “skin-core” structure of LCP and LCP composites. As a consequence, there are abundant macro fibrils in the matrices. The role of the lateral dimension of BN on the properties of LCP was investigated. It is confirmed that BN with a larger lateral size can more effectively improve the TC and thermal stability of LCP. Being filled with 30% BN with a large lateral size of 50 μm, the thermal conductivity of LCP/BN50-30 composite is increased by 88.11% compared with pure LCP, in contrast, the increment ratio of 38.43% and 43.93% when the LCP is filled with BN with lateral size of 0.5 μm and 5.0 μm at the same loading.

The Preparation of Monomer Casting Polyamide 6/Thermotropic Liquid Crystalline Polymer Composite Materials with Satisfactory Miscibility.

It is highly expected to develop a simple and effective method to reinforce polyamide 6 (PA6) to enlarge its application potential. This is challenging because of frequently encountered multi-component phase separations. In this paper, we propose a novel method to solve this issue, essentially comprising two steps. Firstly, a kind of poly (amide-block-aramid) block copolymers, i.e., thermotropic liquid crystalline polymer (TLCP)-polyamide 6 (TLCP-PA6), that contains both rigid aromatic liquid crystal blocks, and flexible alkyl blocks were synthesized. It is unique in that TLCP is chemically linked with PA6, which is advantageous in excellent chemical and physical miscibility with the precursors of monomer casting polyamide 6 (MCPA6), i.e., ε-caprolactam. Secondly, such newly synthesized block copolymer TLCP-PA6 was dissolved in the melting ε-caprolactam, and followed by in situ polymerization to obtain composite polymer blends, i.e., MCPA6/TLCP-PA6. The thermodynamic, morphological, and crystalline properties of MCPA6/TLCP-PA6 can be easily manipulated by tailoring the loading ratios between TLCP-PA6 and ε-caprolactam. Especially, at the optimized condition, such MCPA6/TLCP-PA6 blends show an excellent miscibility. Systematic characterizations, including nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimeter (DSC), and polarizing optical microscope (POM), were performed to confirm these statements. In view of these results, it is anticipated that the overall mechanical properties of such PA6-based polymer composites will be satisfactory, which should enable applications in the modern plastic industry and other emerging areas, such as wearable fabrics.

Intrinsic flame retarding and non-dripping liquid crystal polyethylene terephthalate copolyesters for fire safety system

The notorious issue of high fire hazards, including the generation of considerable heat and melt dripping, is recognized as the bottleneck of extensive use of polyethylene terephthalate (PET). Although various techniques have been adopted for the fabrication of flame retardant PET, how to address the contradiction of flame retardancy and anti-dripping while maintaining its good processability in an environment-friendly method is still challenging. Hence, we design and prepare an intrinsic flame retardant copolyester based on PET and thermotropic liquid crystalline polymer (PET/TLCPx) via a simple and efficient one-step melt copolymerization to address the above challenges. On the one hand, the mesogen units not only allow copolyesters to show a typical liquid crystalline behavior with excellent processability but also constructs a highly rigid main chain to endow PET/TLCPx with outstanding thermal stability, fire resistance, and non-dripping. Furthermore, the resultant PET/TLCP3 exhibits a much lower (by 72 %) peak heat release rate than that of PET, which is attributed to the formation of a denser char layer (char yield ∼ 37 %) for excellent fire resistance. Meanwhile, the melt dripping of PET/TLCPx is suppressed with the increase of complex viscosity and the growth of molecular weight due to the post-condensation during combustion. The resultant high-performance copolyesters are highly valuable for high-end applications that have strict requirements for fire safety and thermal stability, such as fire alarm and rescue systems based on triboelectric effect and shape memory behaviors.

Experimental study on thermotropic side-chain liquid crystalline photo-sensitive polymers

When the chalcone moiety and methylene spacers are bonded to polymer backbone, they are expected to incorporate photosensitive and liquid crystalline properties, respectively. The thermotropic side-chain liquid crystalline photosensitive polymers were synthesized using 4-phenyl styryl carbonyl (phenyl-4-oxy-4-hexyl) methacrylate (PSCPOHMA) and 4-phenyl styryl carbonyl (phenyl-4-oxy-4-decyl) methacrylate (PSCPODMA) monomers by free-radical polymerization using benzoyl peroxide (BPO) as an initiator. The structures of the synthesized monomers and polymers were confirmed by FT-IR, 1H NMR and 13C NMR techniques. The thermal stability and glass transition temperature of the poly (PSCPOHMA) were higher than that of the poly (PSCPODMA). The photocrosslinking of the polymers on irradiation with UV light established that the polymers followed 2π + 2π cyclo addition. The rate of crosslinking increased with increase in the length of the methylene chain. The mesophase of the polymers was also characterized using x-ray diffraction analysis. The liquid crystalline behavior of the polymers was confirmed by DSC and Hot stage optical polarized microscopy (HOPM).The polymers exhibited nematic phase in HOPM. So the polymers have high potential for application in photo resists and electro optic technology.

Reaction mechanism study on transesterification in synthesis of thermotropic liquid crystalline polymer catalyzed by zinc(II) carboxylate: A combination of DFT and kinetics analyses

A deep insight into the reaction mechanism is essential to control the polymerization process with the desired macromolecular structure for high-performance thermotropic liquid crystalline polymer. In this work, density functional theory (DFT) was used to investigate the catalytic polymerization mechanism for the synthesis of thermotropic liquid crystalline polymer catalyzed by zinc(II) carboxylate. The polymerization of 4-acetoxybenzoic acid was studied as a typical reaction. Based on DFT calculations, the rate-limiting step is located in the transesterification between phenol and anhydride acid. The energetically favored pathway was found with the free energy barrier of 51.84 kcal/mol in the presence of zinc acetate, which is significantly lower than the energy barrier without a catalyst. In addition, the effects of the carboxylate group of zinc(II) carboxylate on the catalytic efficiency were revealed by DFT calculations and experiments. Compared with zinc acetate, zinc pivalate has a higher catalytic activity with the rate constant of 1.69 × 10-2 min−1∙M−1 fitted with a second-order reaction model. The HOMO-LUMO gap of zinc pivalate was the smallest among the chosen catalyst, indicating that the chemical activity was strengthened by the methyl substituted. Furthermore, due to the enhanced orbital interactions and the decreased distortion energy in the transition state using zinc pivalate, the energy barrier of the rate-limiting step decreased to 51.36 kcal/mol. These results provide valuable guidance for modeling the catalytic mechanism in aromatic polyester systems.

Effect of the Molecular Structure Change of a Matrix Polymer (Nylon 6) on the Deformation of Dispersed Phase (a Thermotropic Liquid Crystalline Polymer) Droplets in Shear Flow.

In this work, we investigated the effect of a change in the molecular structure and ensuing molar mass change of a matrix polymer (polyamide 6, Ny 6) on droplet deformation of a dispersed thermotropic liquid crystalline polymer (TLCP, a poly(ester amide)) in shear flow. This study focuses on a total capillary number (the sum of the shear capillary number and the elasticity capillary number) and the viscosity ratio between the TLCP and Ny 6, for the morphological development and mechanical performance of TLCP/Ny 6 blends. In contrast to Ny 6, which has a lower melt viscosity than the TLCP melt, a modified Ny 6 (m-Ny 6) with ca. 2 orders higher melt viscosity than that of Ny 6 at a shear rate of 1 s–1 was found to facilitate the deformation of the TLCP phase. A total capillary number was defined to characterize the viscoelasticity effect on droplet deformation in the blend system. The first normal stress difference obtained from the viscosity curve using Steller’s method was used for the evaluation of the elasticity capillary number. The total capillary number for the Ny 6 blend was far less than the critical capillary number and was insufficient for the dispersed TLCP droplets to be deformed. The shear capillary number of the m-Ny 6 blend was greater than the critical capillary number but was still insufficient for droplet deformation into fibril shapes. The total capillary number, including the elastic capillary number, was sufficiently greater than the critical capillary number for deformation of the dispersed TLCP droplets. Morphological observations and a comparison with the theoretical work confirmed the importance of the viscoelasticity of the melt in the immiscible Ny 6/TLCP blends for in situ composite fabrication in shear flow. Both the high viscosity and the first normal stress difference of m-Ny 6 promote the deformation and fibrillation of the dispersed TLCP droplets.

Reaction Mechanism Study on Transesterification in Synthesis of Thermotropic Liquid Crystalline Polymer Catalyzed by Zinc(Ii) Carboxylate: A Combination of Dft and Kinetics Analyses

Reaction Mechanism Study on Transesterification in Synthesis of Thermotropic Liquid Crystalline Polymer Catalyzed by Zinc(Ii) Carboxylate: A Combination of Dft and Kinetics Analyses

Generation of nylon copolymer reinforced with carbon nanotubes and thermotropic liquid crystalline polymers for use in fused filament fabrication

AbstractMultiscale thermoplastic composites consisting of nylon copolymer (PAc) reinforced with thermotropic liquid crystalline polymer (TLCP) and carbon nanotubes (CNTs) were generated in the form of strands and then processed via fused filament fabrication (FFF). The tensile modulus and strength of the laid‐up strands were found to be similar to those reported for polymer reinforced with nearly continuous carbon fibers. In this paper, 1 wt% CNTs were discovered to significantly enhance tensile properties of a nylon copolymer (PAc) reinforced with 20, 30, and 40 wt% TLCP wholly thermoplastic composite (WTC). The WTC filaments were then laid down via fused filament fabrication (FFF). Based on the previous work carried out in our lab, 1 wt% CNTs were the crucial concentration to efficiently enhance carbon fiber (CF) reinforced multiscale composites. The deagglomerated CNT dispersion in the WTCs was accomplished by using supercritical carbon dioxide (scCO2). The effects of TLCP concentration and printing patterns in the lay‐down processes were explored. The most improvement in tensile properties due to the 1 wt% addition of CNTs was observed to be for the 20 wt% TLCP/1 wt% CNTs/PAc samples. The resulting composite filaments exhibited 225% and 80% improvement in the tensile modulus and strength, respectively, compared to the wholly thermoplastic composites (WTCs) without CNTs. In addition, 40 wt% TLCP/1 wt% CNT/PAc 3D printed specimens with filaments laid parallel to the printing direction exhibited excellent tensile modulus and strength of 38.92 GPa and 127.16 MPa, respectively. The measured tensile modulus of 40 wt% TLCP reinforced WTC is even higher than the reported 69 wt% long glass fiber (LGF) or 26 wt% long carbon fiber (LCF) reinforced nylon in fused filament fabrication with the same printing pattern.

Thermotropic liquid crystalline polymer reinforced polypropylene composites enhanced with carbon nanotubes for use in fused filament fabrication

AbstractThe objective of this research was to enhance the mechanical properties of wholly thermoplastic composites (WTCs) used in fused filament fabrication (FFF). Multiscale thermoplastic composites, which were based on the use of polypropylene (PP) reinforced with thermotropic liquid crystalline polymer (TLCP) and carbon nanotubes (CNTs), were prepared by a method combining supercritical carbon dioxide (scCO2)‐aided exfoliation and dual‐extrusion technologies. Significant enhancement of tensile properties was observed by using 1 wt% exfoliated CNTs to reinforce WTCs consisting of PP with and without maleic anhydride‐grafted polypropylene (MAPP, 16 wt%). With 1 wt% CNTs and 16 wt% MAPP dual reinforcement, 20 wt% TLCP reinforced WTCs based on PP exhibited 265%, 274%, and 182% improvement in the tensile modulus of the filaments, laid up specimens in the concentric pattern, and laid up specimens in ±45° rectilinear pattern, respectively. For tensile strength, 1 wt% CNTs reinforcement combined with 16 wt% MAPP improved the 20 wt% TLCP reinforced WTC filaments, laid down parts in the concentric pattern, and ±45° rectilinear patterns by 73%, 53%, and 65%, respectively. The tensile modulus and strength of multiscale WTC based on MAPP/PP specimens laid down with a concentric pattern are higher than those reported for PP/40 wt% short carbon fiber and PP/48.5 wt% short glass fiber laid down specimens. The advanced tensile modulus properties of 1 wt% CNTs reinforced WTCs are competitive with 9 wt% continuous carbon fiber reinforced nylon composite materials in FFF. Scanning electron microscopy analysis showed extremely strong interfacial adhesion between the TLCP fibrils and the matrix in multiscale WTC filaments and laid down parts, compared to the WTCs with no CNTs reinforcement. The advanced interfacial adhesion between TLCP fibrils and matrix resulted in an enhancement in the tensile strength. The exfoliated CNTs were premixed with the matrix, but they were trapped at and aligned with TLCP fibrils, which may be the primary reason for tensile modulus enhancement.

Fiber Formation and Structural Development of HBA/HNA Thermotropic Liquid Crystalline Polymer in High-Speed Melt Spinning.

High-speed melt spinning of thermotropic liquid crystalline polymer (TLCP) resin composed of 4-hydroxybenzoic acid (HBA) and 2-hydroxy-6-napthoic acid (HNA) monomers in a molar ratio of 73/27 was conducted to investigate the characteristic structure development of the fibers under industrial spinning conditions, and the obtained as-spun TLCP fibers were analyzed in detail. The tensile strength and modulus of the fibers increased with shear rate in nozzle hole, draft in spin-line and spinning temperature and exhibited the high values of approximately 1.1 and 63 GPa, respectively, comparable to those of industrial as-spun TLCP fibers, at a shear rate of 70,000 s−1 and a draft of 25. X-ray diffraction demonstrated that the mechanical properties of the fibers increased with the crystalline orientation factor (fc) and the fractions of highly oriented crystalline and non-crystalline anisotropic phases. The results of structure analysis indicated that a characteristic skin-core structure developed at high drafts (i.e., spinning velocity) and low spinning temperatures, which contributed to weakening the mechanical properties of the TLCP fibers. It is supposed that this heterogeneous structure in the cross-section of the fibers was induced by differences in the cooling rates of the skin and core of the fiber in the spin-line.

Thermotropic liquid crystalline polymer reinforced polyamide composite for fused filament fabrication

Varying reinforcement concentrations (20–60 wt%) of thermotropic liquid crystalline polymer (TLCP) were successfully incorporated into a polyamide (PA) matrix using a dual extrusion process for the manufacture of filament for use in fused filament fabrication (FFF). Rheological analyses were used to select the processing conditions for the dual extrusion process that utilized the supercooling behavior of TLCP and minimized the degradation of PA. The optimum 3D-printing temperature was determined as the temperature yielding the printed component with the best mechanical properties. By combining the dual extrusion process with additive manufacturing, it enabled us to generate TLCP/PA composites having greater stiffness (tensile modulus 24.7 GPa) than 3D printed conventional fiber reinforced composites.

The influence of processing conditions on tensile properties of wholly thermoplastic composites reinforced with nanotubes

AbstractThis paper is concerned with novel wholly thermoplastic composites (WTCs) reinforced with supercritical carbon dioxide‐aided exfoliated multi‐walled carbon nanotubes (MWCNTs) and the enhancement of mechanical properties. The bicomponent in situ injection molded plaques consist of polyamide 6 (PA6) and microfibers of thermotropic liquid crystalline polymer (TLCP) with miss‐matched melting temperature. Multiple mixing histories with MWCNTs and processing temperatures were studied and tested for minimizing matrix thermal degradation and maximizing tensile properties of the multi‐scale WTCs. The optimum in situ injection molding temperature was found at 300°C with melt blending nylon 6 matrix and exfoliated MWCNTs in advance. Exfoliated MWCNTs acted as bridging elements between the TLCP and the nylon 6 matrix, which lead to effective stress transfer from the nylon 6 matrix to the TLCP fibrils. Compared to the WTCs without MWCNTs reinforcement, tensile modulus and tensile strength in longitudinal and latitudinal directions were both improved. Furthermore, with the reinforcement of TLCP and exfoliated MWCNTs, the tensile modulus and tensile strength of nylon 6 were enhanced by 173% and 35% in the fluid flow direction, respectively. These experimental results for 20 wt% TLCP/PA6 were even better than the mechanical properties of 20 wt% carbon fiber (CF)/PA6 reported in the literature.

Reactive Processing Route to Thermotropic Polyesters with a Low Processing Temperature and Enhanced Relaxation Time

The processing temperature of thermotropic liquid crystalline polymers (LCPs) can be reduced by increasing the flexibility of the backbone, simultaneously decreasing the relaxation time and resulti...

Sequence segregation in the melt and viscoelasticity of thermotropic liquid crystalline polymer. A rheo-X-ray scattering study

The influence of shear rate on the monomeric sequence segregation of molten thermotropic random copolyester was investigated in-situ using wide-angle X-ray scattering, and the microstructure was correlated with the viscoelastic properties. The X-ray pattern of the aligned macromolecules exhibited the 002 reflection in the melt, which confirmed periodicity along the polymer chains. The azimuthal spread of the 002 reflection is a measure of the degree of longitudinal register of neighboring chains. Increasing the shear rate increased the degree of macromolecular alignment, as measured by P‾2, the order parameter, and the azimuthal spread of the 002 reflection was reduced indicating the increase of the degree of longitudinal register. Small-strain oscillatory shear demonstrated that the monomeric sequence segregation appears to act as transient (physical) crosslinks, the liquid crystalline phase exhibited unusual elasticity and exhibited a well-defined rubber-like regime where G’>>G”. Hence, the van-Gurp-Palmen plot displayed a minimum. The presence of segregated sequences in the melt explains the unusual crystallinity in the random copolymer, the predominantly elastic behavior in the melt, and enables tuning the physical properties by controlling the microstructure.

Shear‐induced textures and viscoelasticity in the nematic and isotropic phase of semiflexible thermotropic polymers. A rheo‐optical study

The striking similarities in response to shear flow of nematic semi‐flexible thermotropic liquid crystalline polymers (LCPs) is reported. Insights into their complex flow was gained by in‐situ polarized optical microscopy (POM) whereas spatial correlations below optical resolution were characterized by small‐angle light scattering (SALS). The LCPs contained mesogenic units separated by ten (10) alkyl spacers, the polyether TPB10 of = 17 kDa and the polyester PSHQ10 of = 53 kDa. The quiescent nematic phase consisted of microdomains randomly oriented, that is, polydomain texture. Shear stretched and aligned the μm‐sized domains. After cessation of shear the texture sprang back and relaxed, PSHQ10 produced banded texture, whereas TPB10 only produced a disordered texture. Strikingly, high shear rate induced monodomains. Upon shear cessation the monodomain in PSHQ10 slowly relaxed to a polydomain, whereas TPB10 maintained a defect free texture. Shear reversal induced crisscross structure in both LCPs and SALS showed asymmetric “butterfly” patterns revealing a tilted microstructure. Shear rheometry in the nematic phase revealed that: (i) PSHQ10 displayed a terminal and rubbery regime, indicating the existence of entanglements; (ii) TPB10 exhibited only a liquid‐like behavior where G″ ≫ G′. The rubbery modulus Ge of PSHQ10 was ca. five times higher in the isotropic than in the nematic phase indicating that a change of conformation is involved in the nematic‐to‐isotropic transition. This study has resulted in correlations between rheological properties and shear‐induced microstructure thus developing new insights into their underlying deformation mechanisms.

Biobased liquid crystalline poly(coumarate)s composites and their potential applications

Poly(coumarate)s has been widely recognised as biobased liquid crystalline polymers and their monomers are used for developing photoreactive materials. In addition, the monomers are synthesized via shikimate pathway in plants and bacteria. Further, these monomers are used as precursors for developing polyesters with enhanced mechanical properties. The biobased monomers such as p-hydroxy cinnamic acid (4HCA), ferulic acid (MHCA) and dihydroxycinnamic acid (DHCA) are used to develop thermotropic liquid crystalline polymers via polycondensation. In this report, various biobased liquid crystalline polymers, their properties and liquid crystalline biohybrids are reviewed.

Development of Recyclable and High-Performance In Situ Hybrid TLCP/Glass Fiber Composites

By combining the concepts of in situ thermotropic liquid crystalline polymer (TLCP) composites and conventional fiber composites, a recyclable and high-performance in situ hybrid polypropylene-based composite was successfully developed. The recycled hybrid composite was prepared by injection molding and grinding processes. Rheological and thermal analyses were utilized to optimize the processing temperature of the injection molding process to reduce the melt viscosity and minimize the degradation of polypropylene. The ideal temperature for blending the hybrid composite was found to be 305 °C. The influence of mechanical recycling on the different combinations of TLCP and glass fiber composites was analyzed. When the weight fraction ratio of TLCP to glass fiber was 2 to 1, the hybrid composite exhibited better processability, improved tensile performance, lower mechanical anisotropy, and greater recyclability compared to the polypropylene reinforced by either glass fiber or TLCP alone.

The influence of mechanical recycling on the properties of thermotropic liquid crystalline polymer and long glass fiber reinforced polypropylene

The effect of mechanical recycling on the properties of injection-molded polypropylene (PP) reinforced with thermotropic liquid crystalline polymer (TLCP) or long glass fiber (GF) has been investigated. The 30 and 50 wt% in situ TCLP and GF reinforced composites were mechanically recycled for three processing cycles, using an injection molding machine with an end-gated plaque mold. The processing temperatures used in the mechanical recycling were determined using rheological and thermogravimetric analyses to minimize the degradation of polypropylene. Recycled TLCP/PP maintained its mechanical properties, and recycling had no significant influence on its morphological, thermal, rheological, and thermo-mechanical properties. Morphological investigation illustrated the regeneration of TLCP fibrils during the mold filling process of each recycle. By the addition of maleic anhydride-grafted polypropylene (MAPP), significant improvements in the mechanical properties of TLCP/PP without impact on recyclability were observed. In contrast, the tensile strength of 50 wt% glass fiber reinforced composite decreased 30% while the tensile modulus decreased 5% after the third recycle. Glass fiber filled polypropylene exhibited significant fiber shortening and was not able to regenerate fibers in processing. Fiber length attrition during the recycling process led to the deterioration of the mechanical properties of the recycled glass filled composites.

On the banded texture and nematic elasticity in a thermotropic liquid crystalline polymer. In situ optical microscopy and light scattering

Optical banded texture after cessation of shear was investigated in a semi‐flexible thermotropic liquid crystalline polymer (LCP) by in situ polarized optical microscopy (POM) and small‐angle light scattering (SALS). The LCP is a random copolymer consisting of mesogenic units separated by alkyl spacers. The quiescent state of the nematic phase exhibited a polydomain texture, with microdomains randomly oriented. Upon application of shear the texture aligned along the shear axis. In situ X‐ray scattering demonstrated that the texture alignment corresponded to macromolecular alignment along the shear axis. Above certain shear rate the aligned texture relaxed and produced a banded texture upon cessation of shear. Shearing at higher shear rate further aligned the texture to produce a monodomain. Stopping the shear spatially uncorrelated structures orthogonal to the shear direction were developed with incubation time in the 100 seconds of second. Hence, there is a threshold of texture alignment to produce banded texture. Shear rheometry showed that the liquid crystalline phase is viscoelastic with features akin to entangled linear polymer melts, for example, a minimum in mechanical damping tan δ [=G”/G']. Furthermore, the nematic phase exhibited considerable recoverable strain after creep. The elastic recoil after cessation of flow would be responsible to produce banded texture. Increasing the creep time reduced the recoverable strain, correlating with longer time to produced banded texture. In contrast, wholly aromatic LCPs exhibit much shorter recovery times after creep and shorter incubation time for banded texture formation.