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.     

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     

Speculation on interfacial adhesion and mechanical properties of blends of PET and thermotropic polyester with flexible spacer groups

A thermotropic liquid crystalline polyester (LCP) with a long flexible spacer group in the main chain was prepared by melt polymerization and mixed with poly(ethylene terephthalate) (PET). Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) studies revealed that the crystallization of PET was accelerated by the addition of LCP in the matrix. Interfacial adhesion between PET and LCP was much improved by introduction of a long flexible spacer in the main chain. Fibers of the blend with 30 wt percent of LCP had fine microfibrillar structure with a large aspect ratio formed in the matrix. Initial modulus and ultimate strength were highly elevated by the addition of LCP due to good interfacial adhesion and microfibrillar structure of LCP in the blend.     

聚酯/液晶聚合物共混纤维的热处理

采用Ｘ射线衍射法、双折射法以及声速法研究了ＰＥＴ及其与液晶聚合物（ＬＣＰ）的共混初生纤维以及经过热处理后纤维的结晶结构和取向结构,并用应力－应变（Ｓ－Ｓ）法测定其断裂强度和初始模量。结果表明,ＬＣＰ的加入使初生纤维取向度和结晶度均下降,而喷头拉伸率增大则使共混初生纤维的结晶度和取向度均提高;由较大喷丝头拉伸率得到的共混纤维经热处理后取向度下降,而结晶度增大;当ＬＣＰ含量大于或等于１０％时,经热处理后共混纤维取向度下降;纤维２１０℃热处理后的晶粒尺寸明显大于１８０℃处理的,且前者的纤维各晶面的晶粒尺寸随着ＬＣＰ加入均有增大;纯ＰＥＴ纤维经热处理后力学性能提高,而ＰＥＴ／ＬＣＰ共混纤维热处理前后力学性能则呈较复杂的变化。     

Effect of composition and molecular structure on the LC phase of PHB-PEN-PET ternary blend

Poly(p-hydroxybenzoic acid) (PHB)–poly(ethylene terephthalate) (PET) 8/2 thermotropic liquid crystalline copolyester, poly(ethylene 2,6-naphthalate) (PEN), and PET were mechanically blended to pursue the liquid crystalline (LC) phase of ternary blends. The torque values of blends with increasing PHB content abruptly decreased above 40 wt % of PHB content because the melt viscosity of ternary blends dropped. Glass transition temperature and melting temperature of blends increased with increasing PHB content. The tensile strength and initial modulus of blends were low at 10 and 20 wt % PHB. However, the blends containing above 30 wt % PHB were improved with increasing PHB content due to the formation of fibrous structure. The blend of 20 wt % PHB formed irregularly dispersed spherical domains, and the blends of 30–40 wt % PHB showed LCP ellipsoidal domains and fibrils. In the polarized optical photographs, the blends of 40 wt % PHB showed pseudo LC phases. The degree of transesterification and randomness of blends were increased with blending time. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1065–1073, 1998     

A novel TLCP blended with PET and PC matrices

This investigation focused on the potential of improving the performance of poly(ethylene terephthalate) (PET) and polycarbonate (PC) fibers by incorporating a novel thermotropic liquid crystalline copolymer (TLCP). The degree of mechanical enhancement obtained in the fibers incorporating 20 wt % TLCP depended upon the chosen matrix material and the processing conditions. The PET matrix systems did not exhibit any modulus improvements until after posttreatment of the fibers. Following posttreatment, the blends exhibited a modulus of 24 GPa, an increase of 40% compared to the PET control fiber. The PC systems exhibited a 1 GPa modulus increase in the as-spun fiber blends, but improvement was negligible after fiber posttreatment. The morphologies of the as-spun and posttreated fibers suggest that different mechanisms of reinforcement are occurring depending upon the matrix material selected. © 1994 John Wiley & Sons, Inc.     

Reactive blending of poly(ethylene terephthalate) with a liquid crystalline copolyester and polyhydroxyether

Poly(ethylene terephthalate) modified with a dianhydride (PET–anhydride) was melt‐blended with a liquid crystalline copolyester (Vectra A) in the presence of a small amount of a liquid crystalline polyhydroxyether. The mechanical properties of a blend consisting of PET–anhydride/Vectra A/polyhydroxyether were drastically improved compared to blends without polyhydroxyether or without anhydride. Melt‐spun fibers of PET–anhydride/Vectra A/polyhydroxyether in a 80/20/0.75 weight ratio displayed a much higher tensile modulus (17 GPa) and tensile strength (214 MPa) than did a 80/20 PET–anhydride/Vectra A blend (4 GPa and 60 MPa, respectively). A similar increase in modulus and strength was found for a 90/10/0.75 relative to a 90/10 blend. The tensile moduli of the blends can well be described by the Tsai–Halpin equation. A better fibril formation was observed, which was attributed to an improved viscosity ratio. Reactions between the various functional groups during melt processing were indicated by viscosity measurements. The polyhydroxyether may act as a reactive compatibilizer which improves the interfacial adhesion, chemically and/or physically. WAXD recordings of both blends showed a crystalline and highly oriented Vectra phase. The PET phase was unoriented and amorphous in a PET/Vectra blend and semicrystalline and weakly oriented in a PET/Vectra/polyhydroxyether blend. Postdrawing of the various blend fibers to λ = 4 increased the modulus by about 40% and the tensile strength by more than 100%, mainly through orientation of the PET phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1107–1123, 1999     

Morphology and mechanical properties of fibers from blends of a liquid crystalline polymer and poly(ethylene terephthalate)

The domain morphology and mechanical properties of fibers spun from blends of a thermotropic liquid crystalline polymer, Vectra A-900, and poly(ethylene terephthalate) (PET) have been studied across the entire composition range. The PET phase was removed by etching to reveal fibrillar LCP domains in the blends of all compositions. The 0.5μm fibril appeared to be the basic structural entity of the LCP domains. A primary effect of composition was the change from discontinuous fibrils when the composition was 35 and 60% by weight LCP to continuous fibrils when the composition was 85 and 96% LCP. This transition had major ramifications on the mechanical properties: the modulus increased abruptly between 60 and 85% LCP, and a change in the fracture mode from brittle fracture to a splitting mode was accompanied by an increase in fracture strength. Different models were required to describe the mechanical properties of the discontinuous and continuous fibril morphologies. Analytic models for short aligned fibers of Nielsen, and Kelly and Tyson were applicable when the LCP fibrils were discontinuous, while modulus and strength of blend fibers with continuous LCP fibrils were discribed by the rule of mixtures.     

Rheological behavior of polyester blend and mechanical properties of the polypropylene–polyester blend fibers

The article deals with method of preparation, rheological properties, phase structure, and morphology of binary blend of poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) and ternary blends of polypropylene (PP)/(PET/PBT). The ternary blend of PET/PBT (PES) containing 30 wt % of PP is used as a final polymer additive (FPA) for blending with PP and subsequent spinning. In addition commercial montane (polyester) wax Licowax E (LiE) was used as a compatibilizer for spinning process enhancement. The PP/PES blend fibers containing 8 wt % of polyester as dispersed phase were prepared in a two‐step procedure: preparation of FPA using laboratory twin‐screw extruder and spinning of the PP/PES blend fibers after blending PP and FPA, using a laboratory spinning equipment. DSC analysis was used for investigation of the phase structure of the PES components and selected blends. Finally, the mechanical properties of the blend fibers were analyzed. It has been found that viscosity of the PET/PBT blends is strongly influenced by the presence of the major component. In addition, the major component suppresses crystallinity of the minor component phase up to a concentration of 30 wt %. PBT as major component in dispersed PES phase increases viscosity of the PET/PBT blend melts and increases the tensile strength of the PP/PES blend fibers. The impact of the compatibilizer on the uniformity of phase dispersion of PP/PES blend fibers was demonstrated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4222–4227, 2006     

Acrylic polymer–silk fibroin blend fibers

Blends of acrylic polymer (containing acrylonitrile 91.7%, methyl acrylate 7%, and sodium methyl propenyl sulfonate 1.3% [wt %], denoted as PAC) with silk fibroin (SF) were studied in the form of drawn fibers with varied compositions. The strength, elongation, and specific work of rupture of the blend fibers decrease with increase of the SF content, whereas the modulus has a slight increase up to 20% (wt) SF and then decreases. With the addition of up to 30% (wt %) SF in the PAC matrix, the moisture absorption increases from 2.06 to 6.2% in comparison with the PAC. Scanning electron microscopy studies show that the blend fibers have a sheath–core structure, with SF mainly in the sheath and PAC in the core. FTIR, ATR, and X-ray diffraction results of the blend fibers are also presented. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:959–966, 1997     

Blends of acrylonitrile–butadiene–styrene/waste poly(ethylene terephthalate) compatibilized by styrene maleic anhydride

Waste poly(ethylene terephthalate) (PET) from thin bottles was blended with acrylonitrile–butadiene–styrene (ABS) copolymer in different proportions, up to 10 wt %. Styrene maleic anhydride (SMA) copolymer was used as a compatibilizer. The tensile strength and heat deflection temperature of the blend were higher than that of virgin ABS. Flexural modulus remained unaffected, although a slight decrease in impact property was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2593–2599, 2001     

In situ composite fibers: Blends of liquid crystalline polymer and poly (ethylene terephthalate)

To augment the concept of in situ composites as alternatives to fiber-reinforced composites, polyblends of a thermotropic liquid crystalline polymer (LCP) and poly(ethylene terephthalate) (PET) were prepared. Fiber-spinning of the blends was performed on a piston-driven plastorneter. Blends of LCP and a low-intrinsic-viscosity PET resin showed poor mechanical performance, which was attributed to their processing behavior. Blends of LCP and a high intrinsicviscosity PET manifested an almost additive behavior with regard to tensile modulus and strength. Elongation of the blends, however, displayed a radical decline, which is reminiscent of fiber-reinforced composites. Heat treatment of the blend fibers modestly increased the tensile properties of the LCP-rich compositions. Blend fibers from PET-rich compositions exhibit a moderate decline in tensile properties owing to thermal relaxation of PET. The data demonstrate that in situ composites or blends of thermotropic LCPs and isotropic polymers present challenging alternatives to fiber-reinforced composite systems because of their ease of processing.     

Toughening of recycled poly(ethylene terephthalate)/glass fiber blends with ethylene–butyl acrylate–glycidyl methacrylate copolymer and maleic anhydride grafted polyethylene–octene rubber

The aim of this study was to improve the toughness of recycled poly(ethylene terephthalate) (PET)/glass fiber (GF) blends through the addition of ethylene–butyl acrylate–glycidyl methacrylate copolymer (EBAGMA) and maleic anhydride grafted polyethylene–octene (POE‐g‐MAH) individually. The morphology and mechanical properties of the ternary blend were also examined in this study. EBAGMA was more effective in toughening recycled PET/GF blends than POE‐g‐MAH; this resulted from its better compatibility with PET and stronger fiber/matrix bonding, as indicated by scanning electron microscopy images. The PET/GF/EBAGMA ternary blend had improved impact strength and well‐balanced mechanical properties at a loading of 8 wt % EBAGMA. The addition of POE‐g‐MAH weakened the fiber/matrix bonding due to more POE‐g‐MAH coated on the GF, which led to weakened impact strength, tensile strength, and flexural modulus. According to dynamic rheometer testing, the use of both EBAGMA and POE‐g‐MAH remarkably increased the melt storage modulus and dynamic viscosity. Differential scanning calorimetry analysis showed that the addition of EBAGMA lowered the crystallization rate of the PET/GF blend, whereas POE‐g‐MAH increased it. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

Effect of a filler on the rheological and mechanical properties of the liquid‐crystalline polyester–poly(methyl methacrylate) blends

The rheological and mechanical properties of the blends of liquid‐crystalline polyester (LCP) and poly(methyl methacrylate) (PMMA) filled with aluminum borate whiskers have been studied. It was established the combined action of reinforcing LCP and filler onto the property of PMMA matrix leads to marked reinforcing of PMMA. At 10% of filler and 30% of LCP, the tensile strength of PMMA increases by 30% and elasticity modulus by 110%, the processability being no worse. The viscosity of the blend PMMA + 30% LCP + 10% filler practically is the same as the PMMA melt viscosity at 220°C. With increasing concentration of LCP up to 30%, the filler effect in binary matrix becomes more essential. The possible reason is the preferential adsorption of LCP at the filler interface (surface segregation) and additional ordering of LCP near the surface, possible, due to additional stretching of nematic phase in the convergent flow zone. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 993–999, 2000     

Recycled poly(ethylene terephthalate)/linear low‐density polyethylene blends through physical processing

Poly(styrene‐ethylene/butylene‐styrene) (SEBS) was used as a compatibilizer to improve the thermal and mechanical properties of recycled poly(ethylene terephthalate)/linear low‐density polyethylene (R‐PET/LLDPE) blends. The blends compatibilized with 0–20 wt % SEBS were prepared by low‐temperature solid‐state extrusion. The effect of SEBS content was investigated using scanning electron microscope, differential scanning calorimeter, dynamic mechanical analysis (DMA), and mechanical property testing. Morphology observation showed that the addition of 10 wt % SEBS led to the deformation of dispersed phase from spherical to fibrous structure, and microfibrils were formed at the interface between two phases in the compatibilized blends. Both differential scanning calorimeter and DMA results revealed that the blend with 20 wt % SEBS showed better compatibility between PET and LLDPE than other blends studied. The addition of 20 wt % of SEBS obviously improved the crystallizibility of PET as well as the modulus of the blends. DMA analysis also showed that the interaction between SEBS and two other components enhanced at high temperature above 130°C. The impact strength of the blend with 20 wt % SEBS increased of 93.2% with respect to the blend without SEBS, accompanied by only a 28.7% tensile strength decrease. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

SELF REINFORCING COMPOSITE BASED ON EPR/LCP BLEND

Blends of ethylene propylene rubber (EPR) and thermotropic liquid crystalline polymer (TLCP) have been prepared by melt-mixing technique. Processing studies indicated the decrease in the viscosity of the blends with the addition of LCP. The mechanical properties like tensile strength and modulus increased up to 10% of LCP and then decreased. The crystallinity increased with an increase in the LCP content. At higher levels of LCP, crystal growth is favored. Thermal studies indicated the endothermic signals that were more prominent at all the peak temperatures. The surface degradation increases with an increase in elastomer (EPR) content in the blend. The relaxation phenomena, as observed from Dynamic Mechanical Thermal Analysis (DMTA) analysis, are changing depending on the blend ratio. The dynamic modulus and stiffness increased with the addition of LCP in the blend. Under dynamic application, at higher levels of LCP, it was observed from scanning electron microscope that there were no cracks at the interface between the EPR and the glass fibers suggesting the better wetting of the fibers by the EPR.     

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     

Mechanical,morphological, and thermal properties of poly(ethylene 2,6-naphthalate) and copolyester LCP blends

Binary blends of a liquid crystalline polymer (LCP) and poly(ethylene 2,6-naphthalate) (PEN) were melt blended and injection molded. The mechanical properties were studied as a function of LCP content. Both the ultimate tensile strength and Young's modulus are higher than the theoretical values predicted by the rule of mixtures and they display a synergistic behavior at 70 wt % LCP content. However, the tensile strength decreases with LCP content and Young's modulus remained unchanged at lower LCP contents (10 to 30 wt %). The poor mechanical property is attributed to the immiscibility between PEN and LCP and the fibrillation behavior of LCP as revealed by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) results. However, LCP and PEN are found to be partially miscible at higher LCP content, ascertained by DSC and dynamic mechanical analysis (DMA). This is attributed to the transesterification reaction between PEN and PET moiety in the LCP molecules. SEM micrographs reveal a skin/core morphology in the tensile bars, that is, the LCP is better oriented in the skin than in the core region. At lower LCP content, the dispersed LCP phase is spherical in the core and ellipsoidal in the skin, with long axes oriented in the flow direction. DSC studies show that the crystallization rate is significantly enhanced by the presence of LCP up to 50 wt %, where the LCP acts as a nucleating agent for PEN crystallization. The melting temperature decreases with LCP content, probably as a result of imperfect crystals formed in the presence of LCP heterogeneous nucleating centers and the increasing miscibility between LCP and PEN. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 477–488, 2001     

Effect of Blend Ratio and Draw Ratio on the Mechanical Properties of PET/PP Blended Conjugate Fibers

This study analyzes the influence of blend ratio and draw ratio on the fiber properties of blend fibers composed of poly (ethylene terephthalate), or PET, and polypropylene, or PP, (hereafter referred to as PET/PP conjugate fibers). For a comparison, PET and poly (butylene terephthalate), or PBT blends, (hereafter referred to as PET/PBT conjugate fibers) are also investigated. Various blend ratios of fibers are melt spun and drawn in a multistep drawing method. The conjugate fibers are evaluated using tenacity, Young's modulus, wide-angle X-ray diffraction, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) tests. The results show that multistep drawing using a lower first-step draw ratio provides a higher tenacity and Young's modulus. Furthermore, when the blend ratio is 75/25 in a PET/PP conjugate fiber and 50/50 in a PET/PBT conjugate fiber, the polymer components undergo a phase inversion phenomenon. A PP sub-micron (10^?1 ～ 10⁰ micron) fiber of about 0.0001 ～ 0.00017 tex in fineness, or about 0.4 ～ 0.5 micron in diameter, can be obtained when PET/PP conjugate fiber is treated with a 25% NaOH aqueous solution by weight. However, A PBT sub-micron fiber cannot be achieved using a PET/PBT conjugate fiber.