Synthesis and properties of liquid crystalline polymers with low Tm and broad mesophase temperature ranges

Novel thermotropic liquid crystalline polymers (TLCP) with improved processability and lower cost than Vectra^® were synthesized by esterification and melt polycondensation. Aromatic compounds, 6-hydroxyl-2-naphthoic acid, 2,6-naphthlenedicarboxylic acid, 4-hydroxybenzoic acid or terephthalic acid, were used as polycyclic stiff rod-like mesogenic groups. Aliphatic diol, ethylene glycol or 1,4-butanediol was used as flexible spacers to form semi-flexible main chain TLCP. The LCP products were characterized by FT-IR and ¹H NMR to identify their chemical structures. The analytical results showed the polymers had inherent viscosities of 0.35-0.54 dL/g. The crank shaft structure of the naphthalene decreased the melting temperature (T_m) of LCP (181-272 °C) to facilitate extrusion or injection molding, and maintained relatively high heat deflection temperature for high performance engineering plastics applications. The 5% weight loss decomposition temperatures were above 400 °C. LCPs have good solvent resistance and low hygroscopicity. The SEM morphology showed strong orientation on the surface in the flow direction and many micro-fibers structure in a sectional drawing. The optical textures of polymers observed by POM revealed a strong birefringence in the melts and indicated that they form nematic mesophase. All polymers have broad mesophase temperature (ΔT_meso) ranges.     

溶剂对PET纤维聚集态结构的影响

用密度法、DSC,偏光显微镜(PLM)和测定收缩率研究了1,2-二氯乙烷对不同纺速PET纤维聚集态结构的影响。结果表明,纺速不同,溶剂诱导结晶(SINC)及其动力学过程不同。高速纺纤维系取向晶态结构,对溶剂扩散有抑制作用。低、中速纺纤维基本为非晶态结构,SINC过程易于进行,但中速纺纤维取向非晶态含量高,溶胀度和收缩率较小。从而印证了关于不同纺速PET纤维结构特征的结论。     

Comparison of solution intercalation and melt intercalation of polymer-clay nanocomposites

Polymer-clay nanocomposites of poly(ethylene oxide)/Na-montmorillonite (PEO/MMT) and PEO/organo-modified bentonite (B34) systems prepared via solution intercalation and melt intercalation have been compared by X-ray diffraction and Fourier transform infrared (FTIR) analysis. The gallery size of solution-intercalated hybrids in both PEO/MMT and PEO/B34 systems increases with PEO content up to a plateau level at 15%. However, the gallery size of melt-intercalated PEO/MMT and PEO/B34 hybrid remains the same regardless of the PEO concentration. FTIR analysis shows no difference in spectrum of samples prepared by solution intercalation compared to melt intercalation. The PEO conformation in the PEO/clay intercalated hybrids is concluded to be a distorted helical structure.     

Thermoplastic extrusion—the mechanism of the formation of extrudate structure and properties

Systems processed by thermoplastic extrusion can be regarded as heterophase polymer melts of incompatible water-plasticized biopolymers. In the process of thermoplastic extrusion, proteins and polysaccharides are melted at high pressure and temperature below the temperature region of their thermal decomposition. Dispersed particles of these systems can be deformed in flow. The mixed-melt anisotropic structure, formed in flow, is fixed by rapid conversion of the melt jet that lets the extruder die from a viscous state to a rubber-like state and then to a glassy state caused by cooling and drying. Incompatibility of proteins and polysaccharides in their water-plasticized melt mixtures impacts on structure formation and texturization during thermoplastic extrusion. Presented at the 20th ISF World Congress and 83rd AOCS Annual Meeting and Expo, May 10–14, 1992, Toronto, Ontario, Canada.     

用CS－1高效催化剂生产聚丙烯树脂的纺丝试验

研究了用ＣＳ－１高效催化剂生产聚丙烯树脂的纺丝性能，得出采用该催化剂并结合分子量调节剂可以得到熔融指数较大，分子量分布较窄的聚丙烯树脂，其纺丝及力学性能都比较好。     

直纺熔体输送管道的设计

介绍了熔体管道设计中管道壁厚选择、熔体流量、熔体管道流动压力降和熔体流速等计算方法和设计要点。     

Higher order structures and mechanical properties of bacterial homo poly(3-hydroxybutyrate) fibers prepared by cold-drawing and annealing processes

Pure bacterial homo poly(3-hydroxybutyrate) (PHB) fibers were prepared by melt spinning, followed by cold-drawing in an amorphous state at a temperature just above its glass transition temperature. Cold drawn fibers obtained were further drawn at higher temperatures, followed by annealing at various temperatures under tension. Relations among the processing conditions, higher order structures and mechanical properties were investigated using wide- and small-angle X-ray diffractions (WAXD and SAXD, respectively), birefringence, differential scanning calorimetry (DSC), and tensile measurements. PHB has two different crystalline forms, 2₁ helix conformation (α-form) and planar zigzag conformation (β-form). A single broad reflection of β-form was detected even in a PHB fiber drawn once at a temperature just above its T_g immediately after quenching and it tended to be stronger after 2nd drawing at higher temperatures. Annealing under low temperature and high tension facilitates the occurrence of β-form. It is suggested that the β-form crystal is formed not only from the tie chains between α-form lamella, but also from completely free amorphous chains. Changes in the amount of two types of crystals were analyzed using the WAXD integrated intensity. Birefringence of these fibers shows negative and positive values, depending on process conditions. Changes in higher order structure on the mechanical properties are also discussed.     

特种竹节纱的生产实践

通过改造传统的FA506细纱机,并调整纺纱工艺,纺出了在一根纱线上有2种颜色变化的特种竹节纱.传统的生产竹节纱的方法是用一根粗纱纺制,而本文中的纺制方法是将两根由不同原料制成的粗纱同时喂入,通过后续的染整加工整理,达到在一根纱上出现2个甚至更多颜色变化的效果.     

膨松型转杯纺棉／PVA长丝复合材料的性能

对转杯纺棉/PVA长丝复合材料及传统的转杯纺织材料等3种材料进行性能测试,涉及到的纺织材料性能指标有强伸性能、条干均匀度、毛羽、膨松度等,侧重于对材料物理性能的研究。研究表明,经溶解的复合材料的膨松度明显上升,断裂强力下降,断裂伸长增加,毛羽增加明显,条干均匀度明显下降。     

不同混纺比甲壳素/长绒棉混纺纱工艺与性能研究

应用东华大学自行研制的小型环锭纺纱整套系统纺出10/90、20/80、30/70、40/60、50/50等5种不同混纺比的19.5 tex甲壳素/棉混纺纱,阐明了各个工序的工艺参数,测定了混纺纱的断裂强度、断裂伸长率、条干CV值和毛羽,分析了混纺比对混纺纱性能的影响.结果表明,10/90甲/棉混纺纱的强伸度最好;20/...