PBT/PC/E-MA-GMA三元共混体系的力学性能与亚微相态

将乙烯-丙烯酸甲酯-甲基丙烯酸缩水甘油酯(E-MA-GMA)三元共聚物与聚碳酸酯(PC)增韧聚对苯二甲酸丁二酯(PBT),研究了其力学性能、亚微相态和强韧化机制。结果表明,当m(PBT)／m(PC)为50:50,三元共混体系在w(E-MA-GMA)为10％时,缺口冲击强度达93 kJ／m2,同时拉伸强度达到54 MPa。扫描电子显微镜观察发现,E- MA-GMA作为柔性界面层,起到反应性增容作用,使PC分散相的相畴尺寸变小。PC相特有的相形态以及柔性界面层的存在是三元共混体系强韧化的主要机制。     

Thermotropic polyester: the influence of the spacer on the physical properties

Thermotropic polyesters prepared from series of 4,4-dihydroxy-,w-diphenoxy alkanes and 4,4-dichloroformyl-,w-diphenoxy alkanes are well known. The substitution of a methylenic spacer by an oxyethylenic spacer in the main chain of these polyesters drastically modifies their physical properties, particularly the mesogenic transition temperatures, as can be observed by DSC and thermooptical analysis. The thermal stability and the polymer solubility in common organic solvents of these polymers did not show a significant change. The physical properties of the two thermotropic polyesters prepared in diphenyl ether were evaluated.     

Thermotropic phase behavior of in vivo extracted human stratum corneum lipids

The thermotropic phase behavior of lipids extracted either in vivo from inner forearm (SCLE) or plantar callus (PC) was investigated by differential scanning calorimetry and small angle X-ray diffraction. PC composition was chromatographically modified (MPC) by eliminating the more polar lipids in order to evaluate their role. Analysis of composition confirms the potential use of PC as a source of stratum corneum lipids. MPC and SCLE exhibit similar differential scanning calorimetry (DSC) profiles with a main transition around 50°C attributed to the solid-to-liquid phase transition of the ceramides. The absence of a transition around 50°C for PC suggests the possible perturbation of ceramide packing by the significantly high proportion of phospholipids. X-ray data suggest a high miscibility of sebum components in stratum corneum lipids with possible modification of chain packing. The MPC patterns show a lipid phase separation which underscores the role of polar lipids in cholesterol/free fatty acids/sterol esters/ceramides structural cohesion.     

Thermotropic polyester: The influence of the spacer on physical properties. II

The thermal transitions of liquid crystalline polyesters have been studied by differential scanning calorimetry and thermooptical microscopy. The physical properties of these thermotropic polyesters, particularly the glass transition and the crystallization temperatures have been investigated. The influence of the spacer type on the transitions has been considered. A glass transition at 64°C was observed of the polyester with oxyethylenic group as flexible spacer while a glass transition could not be observed of the polyester with methylenic groups.     

Effect of third-phase properties on benzyl-n-butyl ether synthesis in phase transfer catalytic system

The production of benzyl-n-butyl ether from benzyl chloride and n-butanol is studied in phase transfer catalytic system. A third phase is formed when polyethylene glycol (PEG) and dodecane are used as the phase transfer catalyst (PTC) and an organic solvent, respectively. The production rate at the three-phase system is higher by seven times than that at the two-phase system. The ether production rate and its selectivity are dependent on the initial concentration of n-butanol. These are affected by the properties of the third phase, especially the concentrations of n-butanol and water in the third phase.

n-Butanol reacts with benzyl chloride and potassium hydroxide simultaneously. The reaction between n-butanol and potassium hydroxide occurs in the aqueous phase. Then, the selectivity of ether on a basis of initial n-butanol is below 0.6 in a stirred tank batch reactor. The selectivity is much improved at 0.9 by using a static triphase batch reactor in which the organic and aqueous phases are separated by the third phase. The interphase mass transfer can be accelerated by ultrasonic device.     

High-pressure phase equilibria for the water/methane system

A semitheoretical method has been established for superimposing the residual thermodynamic properties of pure methane and of pure water over wide ranges of pressure (0.01 to 1,000 MPa) and temperature (triple point to twice the critical temperature). Using reasonable mixing rules with two binary parameters, this superposition also gives mixture properties, including high-pressure vapor-liquid equilibria.     

Thermotropic polyesters: Synthesis and properties of poly(p-oxybenzoate-co-m-phenylene terephthalate)s

DSC, TMA, hot-stage microscopy and WAXS have been used to examine the effect of concentration of angular units and molecular weight on the thermal transitions of poly(p-oxybenzoate-co-m-phenylene terephthalate)s. Copolymers containing molar fractions of m-phenylenedioxy units between 0·20 and 0·30 are melt processable nematogenic materials. In contrast, poly(p-oxybenzoate-co-p-phenylene isophthalate)s remain nematogenic over a wider concentration range (0·20–0·40) of angular isophthaloyl units. Comparison of fibres produced from copolymers with the same fraction of angular units (0·25) indicates that those with isophthaloyl units have a higher modulus than those with m-phenylenedioxy units. These differences are ascribed to differences in planarity of chains containing isophthaloyl and m-phenylenedioxy units, respectively.     

Visco-elastic properties related to the phase morphology of 60/40 PC/SAN blend

Stress relaxation and dynamic mechanical measurements have been performed on a 60/40 blend of polycarbonate of bisphenol A (PC) and poly (styrene-co-acrylonitrile) (SAN). This paper clearly demonstrates that the phase morphology of an immiscible co-continuous polymer blend is an important parameter in determining visco-elastic behavior. The dynamic mechanical properties are discussed in terms of the visco-elastic form of a Kerner equation as a function of the reciprocal Chalkey parameter, which has been used to quantify the co-continuous phase morphology. The effective volume fraction of the SAN phase has been found to decrease as the phase structure coarsens during annealing above T_g of both SAN and PC. This is probably the result of phase break-up and subsequent inclusion of SAN domains in the PC matrix during the coarsening process, which modifies the structure produced during melt compounding and injection molding.     

石蜡/水相变乳液的制备与性能

低温石蜡/水相变乳液作为一种潜热蓄冷流体,具有储能密度高、可泵送的特点,可取代水作为传热介质应用于集中供冷系统中,降低二次循环水泵的运行能耗。基于集中供冷系统的应用要求,选择不同的组分制备相变乳液,包括石蜡、表面活性剂以及晶核剂,并研究其组分含量对乳液分散相粒径分布、热力学性能与流变性能的影响,最终确定相变乳液的制备方法与性能参数。采用所述方法制备的相变乳液具有良好的稳定性,其储能容量为水的2～6倍,且过冷度不高于2 K。     

Thermotropic LCP/CNF nanocomposites prepared with aid of ultrasonic waves

Ultrasound assisted twin screw extrusion process was developed to disperse carbon nanofibers (CNFs) in a polymer matrix. CNFs were separately added into the melt stage to reduce the breakage of CNFs and to avoid intense stresses in the feed zone. The effect of ultrasound and CNFs loading on die pressure, rheological, mechanical, electrical and morphological properties of liquid crystalline polymer (LCP) filled with 0-20 wt% CNFs was studied. Ultrasonic treatment caused a reduction in die pressure and a decrease in electrical percolation threshold value of treated samples. It was also found that mechanical properties of ultrasonically treated LCP/CNF nanocomposite moldings were preserved, improved or slightly decreased in comparison with those of LCP. This is in contrast to available literature typically showing a deterioration of mechanical properties with addition of CNFs. SEM studies have indicated an improved dispersion of CNFs and a reduction of LCP rich area in nanocomposites upon ultrasonic treatment.     

热塑性聚合物／热致液晶聚合物原位复合材料的制备

介绍了热塑性聚合物 /热致液晶聚合物原位复合材料 (TP/TLCP)的加工。系统阐述了热塑性聚合物 /热致液晶聚合物原位复合材料制备过程中流场、剪切速率、拉伸比、加工温度和冷却速率对材料微纤形成和力学性能的影响。同时 ,将现有的加工方法归结为传统加工方法、新加工方法和其他加工方法三类 ,并详细分析了各种加工方法的优缺点。最后指出 ,今后对热塑性聚合物 /热致液晶聚合物原位复合材料的研究应致力于改善界面相容性、优化加工条件和开发新的加工方法     

Liquid crystal polymers: 21. Thermotropic properties and crystallization-induced reactions of aromatic copolyesters

A series of copolyesters containing both mesogenic and non-mesogenic aromatic ester units connected by a flexible spacer were prepared and characterized for their liquid crystalline properties. Samples containing 75 mole percent mesogenic units were heated at temperatures either below or above their melting points to determine if the initially random copolyester could be reorganized to a blocky structure by the process referred to in earlier studies as a ‘crystallization-induced reaction’. This type of reorganization was observed to occur in both the solid state and liquid crystalline state for these copolyesters.     

热致液晶共聚酯PET／60PHB缩聚反应动力学研究

通过反应过程分析及实验数据的处理发现:255℃反应的0～4小时以及265℃和275℃反应的0～2小时范围内,PET与PABA共聚反应属于二级反应,其反应活化能为187.6kJ/mol,符合时-温等效性原理。通过对275℃下制得的PET/60PHB共聚酯的~1H—NMR及~(13)C—NMR谱图进行分析,求得ψ值为0.0714,表明PET与PABA几乎完全是无规共聚的。     

Surface properties of the system: Hard metal/Co coating/electrolyte

The surface properties of hard metal were studied usingin situ electrochemical methods (cyclic voltammetry, potentiostatic and galvanostatic methods) in conjunction withex situ techniques (SEM and X-ray diffraction). The samples were prepared by sintering 91% WC and 9% Co binder in vacuum. The present work was inspired by the possibility of eliminating the low wettability of tungsten carbide by means of electrochemical modification of the surface. The hard metal surface was electrocoated with cobalt. In order to improve adhesion of the Co layer an electrolytic method was developed by which the carbide phase was dissolved anodically at 0.2 V with respect to SCE in 4m NaOH solution. Surface investigations by SEM and X-ray diffraction revealed that electrolytic dissolution of the tungsten carbide leaves the cobalt network (the spongy cobalt layer) with a face-centered cubic lattice (-cobalt). Considering the substrate's influence on adhesion and the coating quality, particular attention was given to the conditions of electrodeposition of -cobalt. Low pH values, low temperature, higher current densities strongly promote the deposition of the -modification of cobalt.A paper presented at the 11th International Corrosion Congress, Florence, Italy, April 1990.     

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。     

Thermotropic behavior of cholesterol-linked polysaccharides

Cholesterol-linked polysaccharides were prepared by reacting monocholesterylsuccinate (ChMS) with cellulose acetate [AC; degree of substitution (DS) 1.00, 1.80, and 2.33], ethyl cellulose (EC; DS 2.46), starch, and hydroxyethyl starch (HES; molar substitution, 0.05–0.07). The degree of ChMS substitution ranged from 0.27 to 1.29. The polymers were characterized by IR, NMR, DSC, and hot-stage coupled polarizing microscopy. Polymers with a higher DS of ChMS showed a thermotropic liquid crystalline behavior. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 195–201, 1998     

热致液晶聚酯—热塑性塑料合金的性能和应用前景

热致液晶聚酯(TLCP)—热塑性塑料(TP)合金是近年开发的新型高性能材料之一。本文介绍了该类合金的流变性能、加工特点、以及组成、温度、剪切速率、拉伸比、加工方式等对力学性能的影响。指出,该合金从性能和成本两方面看,是一种具有良好应用前景的新型高性能材料。     

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。