BHET-PHB热致液晶聚合物的合成及表征

以对苯二甲酸乙二醇酯（BHET）和对羟基苯甲酸（PHB）为原料，采用熔融缩聚法合成了BHET－PHB热致液晶共聚酯。合成的共聚酯化学结构通过红外和核磁来验证，并用DSC、偏光显微镜和X射线衍射研究了其液晶行为，证明BHET－PHB共聚酯为典型的向列型液晶。     

PBT／PHB热致液晶共聚酯的原位乙酰化合成与表征

采用原位乙酰化法，合成了对羟基苯甲酸(PHB)摩尔分数不同的PBT／PHB共聚酯，研究了其组成与相转变和液晶性之间的关系。结果表明，采用PHB的原位乙酰法合成的PBT／PHB共聚酯，当PHB刚性基元的摩尔分数为20％～80%时，PBT／PHB共聚酯为向列型热致性液晶，并存在明显的双玻璃化现象；当PHB的摩尔分数达到60％后，共聚酯表现出两个熔点。这种多重相转变与PBT／PHB共聚酯中存在不同程度的富PBT相和富PHB相有关。采用PHB的原位乙酰化法代替乙酰氧基苯甲酸的酯交换法，一定程度上抑制了PHB嵌段链的形成。     

PBT/PHB热致液晶共聚酯的原位乙酰化合成与表征

采用原位乙酰化法，合成了对羟基苯甲酸(PHB)摩尔分数不同的PBT／PHB共聚酯，研究了其组成与相转变和液晶性之间的关系。结果表明，采用PHB的原位乙酰法合成的PBT／PHB共聚酯，当PHB刚性基元的摩尔分数为为20％～80％时，PBT／PHB共聚酯为向列型热致性液晶，并存在明显的双玻璃化现象；当PHB的摩尔分数达到50％后，共聚酯表现出两个熔点。这种多重相转变与PBT／PHB共聚酯中存在不同程度的富PBT相和富PHB相有关。采用PHB的原位乙酰化法代替乙酰氧基苯甲酸的酯交换法，一定程度上抑制了PHB嵌段链的形成。     

PET／60PABA 热致型液晶共聚酯的合成与表征

将对羟基苯甲酸（PHB）的乙酰化产物对乙酰氧基苯甲酸（PABA）引入聚酯（PET）分子主链结构中,成功制备出共聚酯 PET /60PABA,研究了聚合温度和催化剂浓度对共聚酯合成的影响。通过差示扫描量热（DSC）、X 射线衍射（XRD）、超导核磁共振（NMR）、凝胶渗透色谱（GPC）、偏光显微镜（POM）和毛细管流变仪等手段对共聚酯的分子结构与液晶形态进行表征,结果表明,共聚酯 PET /60PABA 几乎为完全无规共聚,熔融状态下具有向列型热致液晶聚合物的典型特征。     

60PHB/PET液晶共聚酯与聚碳酸酯的相容剂及其影响

制备了液晶共聚酯 6 0 PHB/ PET与聚碳酸酯共混体系的相容剂 TL CP- b- PC,利用索氏抽提器、 DSC、红外光谱、偏光显微镜探讨了相容剂的合成、表征及其对共混体系微观形态的影响。     

TPA／EG／PHB三元液晶共聚酯的液晶行为研究

提高PET/PHB的无规性是近年来人们很关心的问题,因为它涉及到如何进一步提高 PET/PHB 的性能,我们以前的研究结果表明用 PET 齐聚物为原料制备的TPA/EG/PHB 三元液晶共聚酯比 PET/PHB 具有更高的无规性。本文进一步研究了TPA/EG/PHB 的液晶行为,并与 PET/PHB 进行了对比。     

热致液晶性PHB／PET共聚酯的热性能

以对羟基苯甲酸(PHB)和聚对苯二甲酸乙二酯(PET)为原料,经熔融缩聚制备了一系列不同配比的液晶性PHB/PET共聚酯;并研究了这些共聚酯的热转变行为和热稳定性。结果丧明:20PHB/PET共聚酯的冷结晶温度比PET高,而结晶温度比PET低,表明PHB/PET在未形成液晶相的情况下,少量PHB的刚性链段阻碍了PET链节的运动,使其比纯PET更难结晶;在空气介质中,共聚酯的第一热分解温度均高于380℃。PHB含量少于80mol%时,第一热分解温度变化不大,多于80mol%时则迅速上升;第二热分解温度均高于490℃,且随PHB含量增加而呈直线上升。     

一种新型热致性液晶聚酯酰亚胺的合成与表征

在Higashi直接缩聚法的基础上,利用分步投料法,以N,N-己二撑-1,6-双苯偏三酸酰亚胺二胺(IA6)、对羟基苯甲酸(PHB)和对苯二酚二对羟基苯甲酸酯(PHQ)为主要原料,合成了一种新型三元共聚液晶聚酯酰亚胺(IA6PP)。采用FTIR、DSC、TGA、POM和WAXD等方法研究了单体种类对所合成的聚合物结构和性能的影响。结果表明:IA6PP呈现出典型的向列型液晶的特征,液晶温度区间为252~365℃,热稳定性明显高于由4,4-二羟基二苯甲酮(DHBP)、IA6和PHB合成的液晶聚酯酰亚胺(IA6PD)。     

PET／PHB热致液晶共聚酯的合成

本文研究了反应温度、反应时间、催化剂体系和催化剂浓度对PET/PHB(40/60)热致液晶共聚酯共缩聚反应的影响。结果表明,当反应温度为290℃、真空度≤67Pa、使用组合催化剂Sb_2O_3/Zn(CH_3COO)_2·2H_2O、[Cat]/[PHB]=15×10~(-4)摩尔/摩尔、反应时间5小时左右,能获得特性粘度达0.8～0.9、断裂强度和弹性模量都较高的共聚酯。     

热致性液晶全芳共聚酯的设计合成及其性能研究

通过熔融酯交换法,合成了一系列五元全芳共聚酯。利用热台偏光显微镜(PLM)、示差扫描量热法(DSC)等测试分析手段对所合成的产物进行了表征。研究发现,二羟基二苯酮在二酚单体中相对含量较高的情况时聚合产物具有较好的液晶性和成纤性能,表明该单体有利于合成高成纤性、高强度和低熔融加工温度的全芳液晶共聚酯。     

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     

Kinetics of thermal degradation of thermotropic poly(p‐oxybenzoate‐co‐ethylene‐2,6‐naphthalate) by single heating rate methods

The kinetics of thermal degradation of thermotropic liquid crystalline poly(p‐oxybenzoate‐co‐ethylene‐2,6‐naphthalate) (PHB/PEN) with the monomer ratio of 60 : 40 and PEN in nitrogen was studied by dynamic thermogravimetry (TG). The kinetic parameters, including the activation energy E_a, the reaction order n, and the frequency factor ln(Z) of the degradation reaction for PHB/PEN (60 : 40) and PEN were analyzed by the single heating rate methods of Friedman and Chang. The effects of the heating rate and the calculating method on the thermostable and degradation kinetic parameters are systematically discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3915–3920, 2004     

高分子量PET／60PHB热致性液晶共聚酯的结构与性能

研究了固相缩聚过程中PET/60PHB共聚酯结构性能的变化。随着反应的进行,分子量增大,分子量分布宽度指数变小;玻璃化温度略增,熔融温度增加幅度较大;热稳定性明显提高。预聚体中主要存在PET的低共熔物或部分同二质晶,固相缩聚反应使PET结晶消失,PHB结晶形成并完善。固相缩聚大大改善了共聚酯的可纺性,用[η]为0.95dL/g的共聚酯制得断裂强度达到高强范围(1GPa)的初生纤维。     

Analysis of the tensile modulus of poly(p‐hydroxybenzoate)/poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) ternary polyester composite fibers

Liquid crystalline polymer reinforced plastics were prepared by compounding (PHB/PEN/PET) blends. A fibrillar PHB structure was formed in situ in the PEN/PET matrix under a high elongational flow field during melt‐spinning of the composite fibers. The formation of PHB microfibrils in the composite fiber with different PHB contents and winding speeds was observed. The PHB microfibril reinforced PEN/PET composite fibers exhibited an unexpectedly low tensile modulus. We have evaluated the tensile modulus of the fibers using the non‐modified 22 and a modified 23 Halpin–Tsai model. From the analysis of both models, large differences were found between the theoretical and experimental values of the tensile modulus, and the low value of the tensile modulus of the composite fiber could not adequately be explained by either model. Thus, we analyzed the observed modulus values using the Takayanagi model, 24 which describes the concept of mechanical discontinuities in semi‐crystalline polymers. Using the Takayanagi model, the effective fraction of continuous or discontinuous microfibrils was evaluated. Consequently, we could successfully explain the very low modulus of the PHB/PEN/PET composite fiber, having a large number of PHB microfibrils, using the Takayanagi model. Copyright © 2003 Society of Chemical Industry     

PHB/PET/HQ-TPA液晶共聚酯纤维的制备及结构性能研究

对所合成的ＰＨＢ／ＰＥＴ／ＨＱ－ＴＰＡ三元液晶共聚酯进行纺丝实验，制备了初生纤维并对其进行了热处理。利用ＤＳＣ，ＷＡＸＤ，密度，Ｓ－Ｓ曲线等方法对初生纤维及热处理后纤维的结构与性能进行了研究。结果表明：该体系的液晶共聚酯具有较好的可纺性，初生纤维在ＤＳＣ升温过程中有冷结晶峰和熔融双峰现象产生，初生纤维经热处理后，可使其微晶尺寸有较大提高，力学性能得到一定程度改善，但未使其取向性能得到进一步改善。     

60PHB/PET共聚酯纤维的结构与性能

将两种不同分子量(特性粘数分别为0.800dL/g和0.534dL/g)的60PHB/PET共聚酯在小型模拟纺丝机上挤压纺丝。通过物性测试对共聚酯纤维进行了结构与性能分析。结果表明:共聚酯纤维具有高结晶、高晶区取向及高分子链取向的高度规整的原纤化结构。这些结构特征赋予纤维具有超高拉伸模量及动态拉伸模量和低延伸、低收缩。     

Sandwich injection molding of thermotropic copolyesters and filled polyester

Mold filling studies have shown that thermotropic liquid crystalline copolyesters of p-hydroxybenzoicacid (PHB) and polyethyleneterephthalate (PET) fill by an advancing front mechanism similar to flexible chain polymers. The structure and orientation developed during filling as determined on solid specimens by an etching method, X-ray diffraction, and shrinkage study on thin microtomed samples appear to be most pronounced at the surface. Based on this information copolymers of 60 and 80 mole percent PHB/PET were co-injection molded with filled PET under various processing conditions. Because of the low viscosity of the copolyesters, they readily coated filled PET under most processing conditions to give a sheath/core structure. The bending modulus of co-injection molded bars with as little as 35 percent PHB/PET was as high as the sample consisting of 100 percent liquid crystalline copolyester. Electron micrographs of fracture surfaces revealed excellent adhesion between the two polymers.     

60PHB／PET热致液晶共聚酯的流动特征相转变及热处理的影响

在２９０℃下经熔融共聚制得６０ＰＨＢ／ＰＥＴ热致液晶共聚酯。用毛细管流变仪测定流动性能，表明此共聚酯为切力变稀流体；其非牛顿指数、屈服应力在２６０℃均有突变。结合ＤＳＣ，ＤＬＩ，ＴＯＴ等研究，共聚酯在２５５～２５８℃为ＰＨＢ微晶向向列型液晶转变点。流变特征与相态有关。经高温处理（＞２６０℃）的共聚酯熔体在较低温度下呈保持高温流动特征。而经不同温度热处理后冷却样品，其相转变热焓、相转变温度均随热处理温度的增加而增加，尤其是在２６０℃以上热处理后冷却样品，其相转变热焓增加较大，而２８０℃以上热处理后冷却样品的相转变热焓达到最大值。     

PET/PHB液晶共聚酯的合成及液晶性能

将对羟基苯甲酸（ＰＨＢ）单元引入聚对苯二甲酸乙二酯（ＰＥＴ）中,合成液晶共聚酯,１步法工艺优于２步法。就１步法工艺研究缩聚温度、时间、催化剂用量及ＰＨＢ含量对ＰＥＴ／ＰＨＢ共聚酯对数比浓粘数的影响。用偏光显微镜研究结果表明,ＰＥＴ／ＰＨＢ共聚酯呈丝纹形结构,属向列型液晶。用差示扫描量热仪研究的结果也反映出向列型液晶的特征。