Reinforcement of mechanical properties of a poly(ethylene terephthalate) and polycarbonate blend by the addition of thermotropic liquid crystalline polymer

Mechanical properties of the ternary blends of poly(ethylene terephthalate) (PET), polycarbonate (PC), and thermotropic liquid crystalline (TCLP, Vectra A950) were investigated. The ternary blends were prepared by varying the amount TLCP but fixing the ration of PET and PC. The fiber fallen freely through the capillary die had the highest initial modulus (1.46 GPa)/tensile strength (73 MPa) when 10% of TLCP was added. Above this TLCP content, however initial modulus and tensile strength decreased. The scanning electron microscope (SEM) micrographs of the TLCP phase which was extracted by dissolving PET/PC matrix from the blend showed the fine fibrils formed at 5 and 10% of TLCP, while the aggregated TLCP phases at 20 and 30% of TLCP. It was suggested that the decrease of the mechanical properties of the resulting blend was caused by the aggregation of TLCP phase above 10% of TLCP. A high draw ratio gave a rise to the formation of highly oriented fibrils of TLCP phase in the PET/PC matrix and the improvement of mechanical properties of the ternary blend.     

Fabrication of High Performance PET/TLCP Fibers through the Synergistic Interfacial Enhancement and Compatibilization of Functional 1D and 2D Carbon Nanomaterials

The maleic anhydride functionalized graphene oxide (GO-MA) is fabricated by an efficient and solvent-free Diels–Alder reaction. Polyethylene terephthalate (PET)/thermotropic liquid crystal polyester (TLCP), PET/TLCP/GO-MA, PET/TLCP/aminated multi-walled carbon nanotubes (MWCNTs-NH₂), and PET/TLCP/GO-MA/MWCNTs-NH₂ composite fibers are systematically melt-spun. The structure and compatibilizing effects of GO-MA and MWCNTs-NH₂ on the mechanical, thermal, and crystallization properties of the composite fibers are indicated. The non-isothermal crystallization kinetics and X-ray diffraction (XRD) data show that TLCP and nanofillers can change the crystalline morphology of PET. The mechanical properties of the fibers rise with increasing TLCP content. The tensile strength 929 MPa and modulus 17.5 GPa of the fibers with 7 wt% TLCP and 0.25 wt% nanofillers (0.1 wt% GO-MA and 0.15 wt% MWCNTs-NH₂) are significantly higher than those with 7 wt% TLCP (tensile strength 622 MPa and modulus 16.1 GPa) and even higher than those with 15% TLCP (tensile strength 836 MPa, and modulus 18.0 GPa). When the GO-MA and MWCNTs-NH₂ co-exist, the anti-dripping phenomenon is improved. Therefore, the TLCP, GO, and MWCNTs synergistically strengthens the mechanical properties. This is promising for the industrial fabrication of high-strength fibers.     

Fibers from blends of PET and thermotropic liquid crystalline polymer

Blends of poly(ethylene terephthalate-Co-p-oxybenzoate), PET/PHB, with poly(ethylene terephthalate), PET, have been studied in the form of as-spun and drawn fibers. DSC melting and crystallization results show that the PET is compatible with LCP and the crystallization of PET decreases by the addition of LCP in the matrix. Upon heating above the crystal melting temperature of PET, the blend shows good dispersion of LCP in the PET matrix. Wide angle X-ray diffraction of drawn blended fibers show the possible formation of LCP oriented domains. The mechanical properties of drawn fiber up to 10 wt% LCP composition exhibit significant improvement in tensile modulus and tensile strength with values of 17.7 GPa and 1.0 GPa, respectively. Values of modulus are compared with prediction from composite theory, assuming the blend system as nematic domains of LCP. dispersed in PET matrix.     

PET初生纤维在存放和热处理时结构和性能的变化

用声速法、密度和双折射法研究了PET的POY和LOY丝在存放和热处理中的变化。结果表明,用声速法可以跟踪卷绕所得初生纤维在早期结构重排产生的变化。取决于PET初生纤维在热处理前的双折射、热处理温度和热处理时间,可以观察到分子取向的弛豫或结晶,初生纤维具有完全不同的性能。     

Morphological and mechanical properties of PET-LCP blend fibers

Blends of poly(ethylene terephthalate-co-p-oxybenzoate) (PET–PHB) with poly(ethylene terephthalate) (PET) have been studied in the form of as-spun and drawn fibers. Mechanical properties of drawn blend fibers (DR-6.0) up to 10 wt % liquid crystalline polymer (LCP) component exhibit significant improvement in modulus and strength. With the addition of 10 wt % LCP content in PET matrix, the modulus increases from 11.78 to 17.72 GPa, and the strength increases from 0.76 to 1.0 GPa in comparison to the PET homopolymer. With further addition of LCP content, the properties drop down. Scanning electron microscopy studies of drawn blend fibers show that up to 10 wt % LCP content the blends contain the LCP domains in the size range of 0.07–0.2 μm and are well distributed in the PET matrix. © 1995 John Wiley & Sons, Inc.     

Structure–property relationship in fibers spun from poly(ethylene terephthalate) and liquid crystalline polymer blends. I. The effect of composition and processing on fiber morphology and properties

Poly(ethylene terephthalate) (PET) matrix was modified by blending with a specially prepared thermotropic liquid crystalline polymer (TLCP), in the hope to make the in situ composite during fiber spinning. It has been found that the TLCP did not fibrillate in the PET matrix at any concentration under given processing conditions, although it did in the polycarbonate matrix. This was explained by the low interaction parameter (low surface tension) and partial degree of mixing of PET and TLCP. The TLCP was an excellent processing aid even at very low concentrations, but it had an adverse effect on the strength of highly drawn fibers. The modulus of both undrawn and highly drawn fibers increases slightly with increasing TLCP concentration. © 1995 John Wiley & Sons, Inc.     

Structure and properties of blend fibers from poly(ethylene terephthalate) and liquid crystalline polymer

The structure and properties of the as-spun fibers of poly(ethylene terephthalate) (PET) blends with a thermotropic liquid crystalline polymer (LCP), Vectra A900, were studied in detail. The DSC results indicate that the LCP component may act as a nucleating agent promoting the crystallization of the PET matrix from the glassy state but which inhibits its crystallization from the melt due to the existence of an LCP supercooled mesophase. The effect of the drawdown ratio on the orientation of the as-spun blend fibers is highly composition-dependent, which is mainly associated with the formation of LCP fibrils during melt spinning. The modulus of the as-spun blend fibers has a significant increase as the content of LCP reaches 10%, while the tensile strength has a slightly decreasing tendency. The mechanical properties of the as-spun blend fibers could be well improved by heat treatment because of a striking increase in the crystallinity of the PET matrix. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 217–224, 1997     

Preparation of high performance PET fiber by solution spinning technique

High molecular weight poly(ethylene terephthalate) (PET, IV = 3.30 dL/g) was extruded in attempts to prepare high performance fiber using the solution spinning method. Solution preparation, fiber coagulation, and mechanical properties of resultant fibers were examined. An as-spun fiber exhibited high deformability when appropriate coagulation conditions were used. Tenacity and modulus of the resultant drawn fibers achieved 12.9 and 230 gpd, respectively, at draw ratio above 10. © 1995 John Wiley & Sons, Inc.     

Reinforcing properties of poly(trimethyleneterephthalate) by a thermotropic liquid crystal polymer

A thermotropic liquid crystalline copolymer (TLCP) having a trimethylene terephthalate (TT) unit and a triad terephthaloyl mesogenic unit was synthesized and its blends with poly(trimethylene terephthalate) (PTT) were prepared for TLCP‐reinforced fiber spinning. The TLCP, PTT, and their blends were characterized in terms of their thermal, mechanical, and morphological properties. In the hot‐drawn fibers of 20 wt % TLCP/PTT blend, the well‐oriented fibrils were observed at higher temperature (>T_m) than the PTT melt by polarizing optical microscope. With scanning electron microscopy images of cryogenically fractured surfaces of the blends, the TLCP were well dispersed in 0.3 to 0.5 µm in domain size. Interfacial adhesion between the TLCP and PTT seemed fairly good. The TLCP acted effectively as a reinforcing material in PTT matrix, it led to an increase of initial modulus and tensile strength of the blend fibers as TLCP's content increased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41408.     

Modification of the processing window of a thermotropic liquid crystalline polymer by blending with another thermotropic liquid crystalline polymer

This paper is concerned with properties and processing performance of two thermotropic liquid crystalline polymers (TLCPs) produced by DuPont (HX6000 and HX8000) with widely varying melting points and blends of these two TLCPs. This work was carried out in an effort to develop a TLCP suitable for generating poly(ethylene terephthalate) (PET) composites in which the melting point of the TLCP was higher than the processing temperature of PET. Strands of the neat TLCPs and a 50/50 wt % TLCP–TLCP blend were spun and tested for their tensile properties. It was determined that the moduli of the HX8000, HX6000, and HX6000–HX8000 blend strands were 47.1, 70, and 38.5 GPa, respectfully. Monofilaments of PET–HX6000–HX8000 (50/25/25 wt %) were spun with the use of a novel dual extruder process. The strands had moduli as high as 28 GPa, exceeding predictions made using the rule of mixtures and tensile strengths around 275 MPa. The strands were then uniaxially compression molded at 270°C. It was found that after compression molding, the modulus dropped from 28 GPa to roughly 12 GPa due to the loss of molecular orientation in the TLCP phase. However, this represents an improvement over the use of HX8000. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2209–2218, 1999     

含TLCP的PET共混纤维结构和性能

以热致性液晶共聚酯——聚对苯二甲酸乙二酯／对羟基苯甲酸（ＰＥＴ／ＰＨＢ）作为添加剂与ＰＥＴ共混纺丝，研究该ＰＥＴ／ＴＬＣＰ（热致性液晶高聚物）共混物的可纺性，并用ＤＳＣ、Ｘ光衍射、声速和应力－应变等方法对纤维的热性能、结晶和取向结构以及力学性能进行了表征。结果表明，ＴＬＣＰ质量含量为５％左右的ＰＥＴ共混物可纺性良好。ＴＬＣＰ对ＰＥＴ从熔体结晶具有阻止作用，共混初生纤维的玻璃化转变和冷结晶温度均因ＴＬＣＰ的存在而升高。ＴＬＣＰ质量含量为５％的共混物纤维结晶结构与纯ＰＥＴ纤维相似，但晶粒尺寸较小，且晶粒尺寸大小与共混物组成、喷丝头拉伸比和后拉伸比有关。ＴＬＣＰ含量增加，共混纤维取向度和模量增大，而强度下降，但后拉伸可使纤维强度有较大的提高。     

建筑增强用聚丙烯腈纤维的耐海水腐蚀性研究

模拟混凝土应用的海洋环境,在常温(25℃)、氯化物浓度为5610 mg/L的海水中对建筑增强用聚丙烯腈(PAN)纤维进行浸泡处理,研究建筑增强用PAN纤维的耐海水腐蚀性,并与聚对苯二甲酸乙二醇酯(PET)增强纤维和聚丙烯(PP)增强纤维进行对比。结果表明:海水浸泡50 d后,建筑增强用PAN纤维的主要吸收特征峰无明显变化,且无新的吸收特征峰出现,纤维超分子结构变化较小,晶区取向度基本保持不变,结晶度略有增加;海水浸泡50 d后,建筑增强用PAN纤维的拉伸强度为1261 MPa、降幅0.63%,初始模量为18.6 GPa、增幅8.14%,其拉伸强度与PET增强纤维相当、约为PP增强纤维的1.8倍,初始模量约是PET增强纤维的1.4倍、PP增强纤维的3.2倍;建筑增强用PAN纤维、PET增强纤维、PP增强纤维的拉伸强度耐蚀系数分别为99.4%,99.2%,100.0%,建筑增强用PAN纤维的耐海水腐蚀性介于PP增强纤维和PET增强纤维之间,但其在海水中环境中具有优异的模量保持优势,可以更好地提高混凝土在海水环境中的耐受力。     

Polybenzimidazole and polysulfone blends

Polybenzimidazole (PBI) and polysulfone (PS) do not form miscible blends; however, the tensile modulus and strength of their blend fibers are comparable to, or better than, that of PBI fibers, depending on process conditions. Fibers spun from an 80/20 PBI/PS solution blend have PBI-like LOI (limiting oxygen indices) and flame shrinkage behavior. Sulfonation and stabilization of this fiber improve its thermal properties. The process window for these blend fibers has been determined. There was no aging phenomenon on as-spun PBI/PS blend fibers, while as-spun fibers made from PBI/polyarylate (PA) and PBI/high modulus aramides (HMA) exhibited remarkable aging effects on fiber properties. This difference probably arises from the fact that (1) the former is not a miscible blend, while the latter are; and (2) the former does not have hydrolysis groups, such as ester and amide groups, as that in the PA and HMA systems.     

热致性液晶共聚酯-PET共混体的可纺性及纤维的性能

通过流变性能、表面张力等的测试对 PHB/PET(60/40)共聚酯与 PET 共混体的可纺性及加工条件进行了讨论。用改制的熔融指数仪纺制了不同配比的共混纤维,并测定了初生纤维及拉伸丝的力学性能,通过偏光显微镜、扫描电镜、DSC 测定了纤维结构。共混体在300℃熔融,280℃纺丝,当共聚酯含量在6.6%以下时,共混体有较好的可纺性。共聚酯含量在3.3%时,纤维有较好的强度与模量,与同等条件下纺制的纯 PET 纤维相比,强度提高70%,模量可提高两倍多。     

热致性液晶聚芳酯纤维的后固相聚合宏观动力学

以热致性液晶聚芳酯(TLCP)初生纤维为原料,通过初生纤维后续的热处理(即后固相聚合)提高纤维力学性能,对纤维后固相反应的宏观动力学行为进行了研究。结果表明:在热处理初期,纤维质量损失率增加迅速,说明聚芳酯相对分子质量增长速率较快;当达到一定程度后,相对分子质量增长速率变慢;热处理温度对其影响显著,热处理温度越高,相对分子质量升高越快;热处理前后期的表观活化能分别为94.4 kJ/mol和38.4 kJ/mol。     

Stability of blends of thermotropic liquid crystalline polymers with thermoplastic polymers

Breakup of fibers of a thermotropic liquid crystalline polymer (TLCP) above the melting temperature in various ordinary polymers has been studied by capillary instability experiments on single TLCP fibers and by annealing experiments on extruded TLCP/thermoplast blends. The TLCP was an aromatic copolyester, Vectra A900, the matrix polymers were PP, PS, PC, PEL PES, and PEBT. Both types of experiments show that the fiber/matrix morphology is, in general, highly unstable in the molten state. The TLCP fibers break up into droplets by a combination of Rayleigh distortions, end-pinching and retraction, depending on the system and shape of the fiber. Fibers of a thickness of ～1 μm can break up in a few seconds. Breakup times of fibrous blends and individual fibers are in agreement provided size effects are accounted for. Rayleigh distortions develop exponentially in time up to relative distortions of 0.5 to 0.6. Breakup occurs within a range of wave numbers rather than at one distinct dominant wave number, which is shown to be the consequence of relatively large initial distortions. Apparent values for the interfacial tensions calculated with Tomotika's theory turned out to be of the correct order of magnitude, ranging from 7 mN/m for Vectra/PES to 24 mN/m for Vectra/PP and to yield correct values of the interfacial tensions of PP/PS, PP/PC, and PS/PC using Antonow's rule.     

Blends of thermotropic liquid crystalline polyesters and poly(butylene terephthalate): Thermal,mechanical, and morphological properties

Blends of poly(butylene terephthalate) (PBT) with three different thermotropic liquid crystalline polyesters (TLCPs) were prepared. The first TLCP (HBH-6) consists of diad aromaticester type mesogenic units and the hexamethylene spacers along the main chain, and the second (TB-S6) is a wholly aromatic polyester TLCP having alkoxy side groups on the terephthaloyl moiety. The last (TR-4,6) is an LC copolymer comsisting of triad aromatic ester type mesogenic units and two differents spacers; tetramethylene and hexamethylene units. Blends of TLCP with PBT were melt spum at different LCP contents and differnt draw ratios to produce monofilaments. For the HBH-6/PBT and TB-S6/PBT blends, the ultimate tensile strength showed a maximum value at the 5 wt% level of LCP in the blends, and then it decreased when the LCP content was increased up to 20%. On the other hand, the initial modulus monotonically increased with increasing LCP content in all cases. The blends with TB-S6 showed the highest tensile properties of the three blends systems. This can be ascribed to the highest rigidity of the polymer chain, which still carries relatively long alkoxy substituents that promote sufficient adhesion between the LCP and PBT matrix. When compared with the PBT fiber itself, the fibers obtained from the 5% TB-S6/PBT blends exhibited an improvement in tensile strength by > 25% and in tensile modulus by ～ 200%.     

Noticeable viscosity reduction of polycarbonate melts caused jointly by nano‐silica filling and TLCP fibrillation

Nano‐SiO₂ was introduced into in‐situ composites of polycarbonate (PC) and a thermotropic liquid crystalline polymer (TLCP) using a twin‐screw extruder. The rheology of these composites was characterized with capillary rheometry, and the morphology of the dispersed TLCP observed with scanning electron microscopy. The rheological data revealed that the viscosity decrease of PC melts by only the addition up to 20 wt% TLCP remained smaller than 30%, while it became ～48% upon further addition of only about 1 wt% nano‐SiO₂ and larger than 60% upon ～9 wt% nano‐SiO₂ filling, in contrast to a 50% viscosity increase of PC melts with increase in nanosilica loading up to ～9 wt%. These silica‐filled composites exhibited markedly low viscosity, especially at relatively high shear rates. The morphology of TLCP extracted from unfilled and silica‐filled composites indicated that the largest viscosity reduction was correlated well with the fibrillation of TLCP droplets enhanced by nano‐SiO₂. The TLCP/SiO₂/PC composites exhibited rheological hybrid effect with fillers at nanometer scale. POLYM. ENG. SCI., 47:757–764, 2007. © 2007 Society of Plastics Engineers     

Structure and property relationship of thermotropic liquid crystal polymer and polyester composite fibers

Poly(ethylene 2,6‐naphthalate) (PEN) and poly(ethylene terephthalate) (PET) composite fibers reinforced with a thermotropic liquid crystal polymer (TLCP) were prepared by the melt blending and spinning process to achieve high performance fibers with improved processability. Polymer composite fibers consisting of cheap polyester and small quantity of expensive TLCP are of interest from an economic point of view and from an industrial perspective. The increase in the birefringence and density of the TLCP/PEN/PET composite fibers with the spinning speed was attributable to the enhancement of the molecular orientation and effective packing between chains in the TLCP/PEN/PET composite fibers. Annealing process resulted in the formation of more ordered and perfect crystalline structure and higher crystallinity, improving the mechanical properties of the TLCP/PEN/PET composite fibers. The increase in the crystallite size and the degree of chain extension with increasing spinning speed resulted in the gradual increment of the long period for the TLCP/PEN/PET composite fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006.     

TEMPO-oxidized cellulose nanofibril/poly(vinyl alcohol) composite drawn fibers

PVA/TOCN composite fiber with a weight ratio of 100:1 was prepared from a mixture of aqueous poly(vinyl alcohol) (PVA) solution and 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-oxidized cellulose nanofibril (TOCN) dispersion using spinning, drawing, and drying processes. The as-spun PVA/TOCN composite fiber was further drawn, up to a draw ratio of 20 by heating at up to 230 °C. The maximum tensile modulus of the PVA/TOCN composite drawn fiber reached 57 GPa, remarkably higher than that of commercial PVA drawn fibers. Moreover, the PVA/TOCN composite drawn fiber had storage modulus higher than that of the PVA drawn fiber at each temperature in the range from 28 to 239 °C. Structural analyses showed that amorphous PVA regions in the composite drawn fiber were more oriented than those in neat PVA fiber after the addition of the small amount of TOCN used. These results indicate that TOCN elements were individually dispersed in the PVA matrix without aggregation and formed hydrogen bonds with amorphous PVA molecules in the composite drawn fiber.