热致液晶共聚酯—聚碳酸酯原位复合体系的性能

液晶共聚酯６０ＰＨＢ／ＰＥＴ（ＴＬＣＰ）与聚碳酸酯（ＰＣ）共混可制备原位复合材料,两者１：１的共聚物（ＴＬＣＰ－ｂ－ＰＣ）可作其共混体系的相容剂。本文对该原位复合体系的流变性能、力学性能、纺丝性能和微观形态作了讨论。结果表明：该体系为切力变稀流体;ＰＣ：ＴＬＣＰ：ＴＬＣＰ－ｂ－ＰＣ组成为７９：１９：２时,综合力学性能最优;不同原位复合体系最佳纺丝温度各不相同;相容剂对提高界面粘合力起了良好的作用。     

相容剂对PC/PLA共混体系性能的影响

研究了不同相容剂对聚碳酸酯/聚乳酸(PC/PLA)共混体系性能的影响,找出了增容效果明显的相容剂EMG,并进一步研究了EMG对PC/PLA共混体系相容性及力学性能的影响。结果表明:相容剂EMG的加入,促使共混体系中PC的玻璃化转变温度有所下降,PLA的玻璃化转变温度进一步提高,增强了两相间的界面黏结作用,改善了PC/PLA之间的相容性;EMG的加入,提高了PC/PLA共混物的力学性能,当相容剂质量分数为9%时,拉伸强度、断裂伸长率和缺口冲击强度均达到最大值。     

PC/PET合金的制备与性能研究

利用熔融共混法制备了聚碳酸酯/聚对苯二甲酸乙二醇酯(PC/PET)合金,讨论了PC/PET配比、相容剂、酯交换抑制剂对PC/PET合金物理力学性能的影响。结果表明:在PC/PET共混物中添加相容剂可以提高共混物的力学性能,添加磷酸三苯酯(TPP)可以有效抑制PC/PET的酯交换反应;当相容剂用量为5%、PC/PET/TPP为70/30/0.5时,共混合金的综合性能最佳。     

相容剂对PBT／PC共混物力学性能的影响

利用聚对苯二甲酸丁二醇酯(PBT)与聚碳酸酯(PC)之间的酯交换反应制备了几种PBT与PC的相容剂。相容剂对PBT／PC共混物力学性能的影响的研究表明：加入相容剂改善了PBT与PC两相间的相容性，共混体系力学性能得到提高。通过红外光谱分析得知，PBT、与PC之间的酯交换反应促进了PBT／PC共混体系的相容性，酯交换反应越强烈，得到的产物作为相容剂对PBT／PC共混体系的增容作用越明显；酯交换反应程度适中，得到的产物作为相容剂增容作用适中，共混体系综合力学性能较好。     

相容剂对PC/TPU共混体系性能的影响

研究了自制的相容剂聚碳酸酯聚氨酯(PCU)对PC/TPU共混体系相容性及力学性能的影响.结果表明,相容剂PCU的加入,促使共混体系中PC的玻璃化温度进一步降低,增强了两相间的界面黏结作用,改善了 PC/TPU之间的相容性;PCU的加入,提高了PC/TPU共混物的冲击性能,当相容剂用量为6份时,缺口冲击强度达到最大值,为未加相容剂时的5倍.     

PET/TLCP原位共混的研究

研究了PET／TLCP原位共混体系的热性能、流变性能、力学性能。结果表明,在PET中加入少量TLCP可起到结晶成核剂的作用,提高PET基体的结晶性能,并使共混物的熔体粘度降低;催化剂二月桂酸二丁基锡的加入,可增加共混物的熔体粘度,降低分散相的尺寸,增强经物两相间的界面粘接,从而提高PET／TLCP共混体系的力学性能。     

玻璃纤维增强PA 6/PBT低吸湿共混物的力学性能

以马来酸酐接枝乙烯-辛烯共聚物(POE-g-MAH)和乙烯-甲基丙烯酸丁酯-丙烯酸缩水甘油酯三元共聚物(PTW)为复合相容剂,在平行同向双螺杆挤出机上熔融共混,制备了玻璃纤维增强聚酰胺(PA)6/聚对苯二甲酸丁二酯(PBT)共混物。考察了复合相容剂对增强共混材料力学性能的影响,并探讨了共混物的吸湿性与力学性能的关系。结果表明:相容剂的复合使用有协同作用;PA 6/PBT共混体系随w(PBT)增加,力学性能下降,w(PBT)增加到32.0%时,拉伸强度、弯曲强度、简支梁缺口冲击强度分别下降25.2%,15.8%,45.3%;并且随w(PBT)增加,共混体系对吸湿的敏感性降低。     

PET／TLCP原位共混的研究

研究了PET／TLCP原位共混体系的热性能、流变性能、力学性能。结果表明，在PET中加入少量TLCP可起到结晶成核剂的作用，提高PET基体的结晶性能，并使共混物的熔体粘度降低；催化剂二月桂酸二丁基锡的加入，可增加共混物的熔体粘度，降低分散相的尺寸，增强共混物两相间的界面粘接，从而提高PET／TLCP共混体系的力学性能。     

相容剂对PC/ABS共混物性能的影响

本文分别研究了马来酸酐接枝ABS(ABS-g-MAH)与甲基丙烯酸甲酯/丁二烯/苯乙烯共聚物(MBS)作为相容剂对PC/ABS共混体系相容性、力学性能、形态结构的影响.研究结果表明:当相容剂MBS加入PC/ABS共混体系中后,不仅能够显著改善PC/ABS共混物的相容性,明显降低分散相的粒径,而且能够使PC/ABS共混物在保持较高的拉伸强度的同时,大幅度地提高共混物的缺口冲击强度和断裂伸长率;而相容剂ABS-g-MAH的加入对共混体系的缺口冲击强度的改善不明显,但其断裂伸长率增幅较大.     

环氧型扩链剂ADR改性PBT/PA6共混体系及其性能研究

通过双螺杆挤出机制备环氧型扩链剂ADR增容对苯二甲酸丁二醇酯(PBT)/聚酰胺6(PA6)共混物,并对共混体系的流变性能、热稳定性、结晶性能以及力学性能进行研究。结果发现:随着相容剂含量的增加,共混体系的熔融指数下降,剪切粘度增大;相容剂的加入提高了共混体系的热稳定性,增强了共混体系的机械性能,降低了共混体系的结晶性能。当相容剂含量为0.6%时,共混物的力学性能达到最佳。     

Properties of a thermotropic liquid crystalline polymer blended with different thermoplastics

Thermal, rheological, morphological, and mechanical properties of a thermotropic liquid crystalline polymer, TLCP (copolyester Vectra A-950 from Hoechst), blended with a polycarbonate (PC), a polyethylene glycol terephthalate (PETG), and a blend of PC and PETG (20/80) are presented and discussed. Important supercooling effects are observed for the TLCP. For the blends the glass transition temperature of the matrix is shown to decrease slightly, suggesting partial miscibility of the components. A finer dispersion is observed for the TLCP/PC blends, at least for TLCP concentrations lower than 20%, for which the mechanical properties are quite good. For higher TLCP concentrations, as well as for the other two matrices, the mechanical properties follow more or less the mixing rule, and the morphology of the blends suggests poor adhesion. We were unable to obtain fibrillar structures by extruding the blends through a capillary rheometer; in the TLCP/PC blends, the TLCP domains were too small, and for the other blends the extrudates had not enough melt strength.     

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.     

Study on the miscibility and rheological properties of thermotropic liquid crystalline polymers in thermoplastic matrices

The interfacial properties of polymer blends of the engineering thermoplastics (TPs) polycarbonate (PC) and polyethersulfone (PES) with thermotropic liquid crystalline polymers (TLCPs) were studied using FTIR and DSC. The TLCP/TP blend systems were mainly immiscible. The viscosity properties of the TLCP/TP blends were analysed. The mechanism of the viscosity variation of the blends is discussed. Based on the assumptions given in this paper, a reasoned theoretical formula of the blend viscosity is derived to express the viscosity reduction of the TLCP/TP blends.     

Study of the Processing and Mechanical Properties of In Situ Composite Materials of Thermoplastics with Thermotropic Liquid Crystalline Polymers

By blending thermoplastics (TPs)—polycarbonate (PC) and polyethersulfone (PES)—with thermotropic liquid crystalline polymers (TLCPs)—KU9221 and KU9231—and then extruding the blends to form fibers, the in situ reinforcing characteristics were studied. The injection experiment of blends was compared with the extrusion experiment. According to the experimental results, in situ reinforcing characteristics of these processes were analyzed theoretically. These researches have come to some important conclusions. TLCP domains can be transformed to form fibers that are oriented in the direction of flow during processing; these TLCP microfibers result in improved mechanical properties of the TP/TLCP blends. The extruding flow is more effective in orienting TLCP domains and results in better in situ reinforcement than that of injection molding, and the extruded fibers have better mechanical properties. The mechanical properties of the blend fibers are improved greatly with increasing tensile ratio of melt drawing and the content of TLCPs.     

Structure and properties of thermotropic liquid crystal polymer and poly(ethylene 2,6‐naphthalate) blend fibers

BACKGROUND: The melt blending of thermotropic liquid crystal polymers (TLCPs) using conventional thermoplastics has attracted much attention due to the improved strength and tensile modulus of the resulting polymer composites. Moreover, because of their low melt viscosity, the addition of small amounts of TLCPs can reduce the melt viscosity of polymer blends, thereby enhancing the processability. RESULTS: In this study, TLCP/poly(ethylene 2,6‐naphthalate) (PEN) blend fibers were prepared by melt blending and melt spinning to improve fiber performance and processability. The relation between the structure and the mechanical properties of TLCP/PEN blend fibers and the effect of annealing on these properties were also investigated. The mechanical properties of the blend fibers were improved by increasing the spinning speed and by adding TLCP. These properties of the blend fibers were also improved by annealing. The tensile strength of TLCP5/PEN spun at a spinning speed of 2.0 km h^?1 and annealed at 235 °C for 2 h was about three times higher than that of TLCP5/PEN spun at a spinning speed of 0.5 km h^?1. The double melting behavior observed in the annealed fibers depended on the annealing temperature and time. CONCLUSION: The improvement of the mechanical properties of the blend fibers with spinning speed, by adding TLCP and by annealing was attributed to an increase in crystallite size, an increase in the degree of crystallinity and an improvement in crystal perfection. The double melting behavior was influenced by the distribution in lamella thickness that occurred because of a melt‐reorganization process during differential scanning calorimetry scans. Copyright © 2007 Society of Chemical Industry     

Inhibited transesterification and enhanced fibrillation of TLCP by nano-SiO2 in polycarbonate matrix

Hybrid composites composed of a thermotropic liquid crystalline polymer (TLCP), nano-SiO₂ and polycarbonate (PC) were prepared by melt blending in a twin-screw extruder. Infrared spectroscopy analysis indicated that the transesterification between PC and TLCP molecules during melt blending was significantly reduced in TLCP/PC blends filled with nano-SiO₂, compared to the unfilled TLCP/PC one. Scanning electron microscopy (SEM) observation showed that better compatibility and finer TLCP dispersion were reached in the unfilled blend, which made the fibrillation of TLCP difficult in capillary flow even at high shear rate. In contrast to this, well-developed TLCP fibrils were formed by capillary flow in nano-SiO₂ filled TLCP/PC blends. By increasing the nano-SiO₂ concentration and shear rate, the fibrillation of TLCP was significantly enhanced. Thermodynamically the interfacial tension between these components and dynamically the viscosity ratio of TLCP to PC were used to investigate the mechanism of nano-SiO₂ in inhibiting the transesterification and enhancing the fibrillation of TLCP droplets in these hybrid composites.     

Thermotropic liquid‐crystalline copolyester/thermoplastic elastomer in situ composites. I. Rheology,morphology, and mechanical properties of extruded strands

A thermotropic liquid‐crystalline polymer (TLCP), a copolyester with a 60/40 molar ratio of p‐hydroxy benzoic acid and poly(ethylene terephthalate), was blended with a styrene/ethylene butylene/styrene thermoplastic elastomer with a twin‐screw extruder. The rheological behavior, morphology, and mechanical properties of the extruded strands of the blends were investigated. The rheological measurements were performed on a capillary rheometer in the shear rate range of 5–2000 s^?1 and on a plate‐and‐plate rheometer in the frequency range of 0.6–200 rad s^?1. All the neat components and blends exhibited shear thinning behavior. Both the shear and complex viscosities of all the blends decreased with increasing TLCP contents, but the decrease in the shear viscosity was more pronounced. The best fibrillar morphology was observed in the extruded strands of a blend containing 30 wt % TLCP, and a lamellar structure started to form at 40 wt % TLCP. With an increasing concentration of TLCP, the tensile modulus of the blends was greatly enhanced, whereas the tensile strength was almost unchanged. The elongation at break of the blends first slightly decreased with the addition of TLCP and then sharply dropped at 40 wt % TLCP. The tension set measured at 200% deformation slightly increased with increasing TLCP contents up to 30 wt %, over which the set value was unacceptable for a thermoplastic elastomer. A remarkable improvement in the dynamic mechanical properties of the extruded strands was observed in the blends with increasing amounts of TLCP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2676–2685, 2003     

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.     

聚苯硫醚／热致液晶高分子共混体系的结构与性能研究

本文研究了聚苯硫醚(PPS)与两种热致型液晶聚合物(TLCP)共混体系的热性能、力学性能及形态。结果表明,TLCP的加入对于PPS的结晶性及热稳定性都有一定影响。当半芳聚酯类液晶用量少于5份时,共混体系的力学性能优于纯PPS。形态表明,共混物中的TLCP多以取向度较小的椭球体形式存在。     

Self‐reinforcing elastomer composites based on polyolefinic thermoplastic elastomer and thermotropic liquid crystalline polymer

In situ reinforcing elastomer composites based on Santoprene thermoplastic elastomer, a polymerized polyolefin compound of ethylene–propylene–diene monomer/polypropylene, and a thermotropic liquid crystalline polymer (TLCP), Rodrun LC3000, were prepared using a single‐screw extruder. The rheological behavior, morphology, mechanical, and thermal properties of the blends containing various LC3000 contents were investigated. All neat components and their blends exhibited shear thinning behavior. With increasing TLCP content, processability became easier because of the decrease in melt viscosity of the blends. Despite the viscosity ratio of dispersed phase to the matrix phase for the blend system is lower than 0.14, most of TLCP domains in the blends containing 5–10 wt % LC3000 appeared as droplets. At 20 wt % LC3000 or more, the domain size of TLCP became larger because of the coalescence of liquid TLCP threads that occurred during extrusion. The addition of LC3000 into the elastomer matrix enhanced the initial tensile modulus considerably whereas the extensibility of the blends remarkably decreased with addition of high TLCP level (>.20 wt %). The incorporation of LC3000 into Santoprene slightly improved the thermal resistance both in nitrogen and in air. Dynamic mechanical analysis results clearly showed an enhancement in dynamic moduli for the blends with 20–30 wt % LC3000. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008