聚氨酯弹性体的结晶行为

聚氨酯弹性体是两相结构聚合物，软段相可能存在ａ型和β型球晶，硬段相可能存在三种类型球晶，即Ⅰ，Ⅱ，Ⅲ型。ＰＵ软段的Ｍ在２０００以上，硬段中二苯甲烷－４，４＇－二异氰酸酯的含量为２－４ｍｏｌ时才可能在各自相中分别产生结晶。随聚合反应时间和室温老化时间的延长，结晶数量增加，ＰＵ结晶度高，球晶尺寸，岢提高ＰＵ的初始模量，杨氏模量、拉伸强度和韧性，能使伸长率下降。     

浅析形状记忆聚氨酯弹性体

形状记忆聚氨酯弹性体是以软链段的结晶-熔融实现形状记忆功能,简述了形状记忆聚氨酯的设计要求,阐述了影响形状记忆的因素,最后简要介绍了形状记忆聚氨酯的应用。     

聚氨酯弹性体的制备

本文利用聚乙二醇与TDI反应制备异氰酸酯基封端的聚氨酯弹性体,并研究了反应温度、反应时间、原料配比等对聚合反应的影响,确定了最优化的反应条件。研究结果表明,聚氨酯弹性体合成反应的最佳温度为60℃,最佳反应时间为70～90 min,水分的存在对反应十分有害,应对参加反应的聚乙二醇严格抽真空脱水。对聚氨酯弹性体的红外光谱分析表明,羟基基本反应完全,得到了预期产物。     

扩链剂对聚氨酯弹性体形态结构的影响

综述了扩链剂对聚氨酯弹性体形态结构的影响及扩链剂作用机理,对扩链剂的开发应用具有重要参考价值。     

聚氨酯微孔弹性体的制备与探讨

一、前言聚氨酯微孔弹性体与一般橡胶相比,具有较好的弹性、较高的抗伸强度和撕裂强度。其最突出特点是具有吸收冲击性能,因而广泛应用于制造防震缓冲材料。随着汽车工业的迅速发展,特别是轿车工业的发展,空气滤清器对材料的要求越来越高,而聚氨酯微孔弹性体具有其突出特点,用聚氨酯微孔弹     

医用新型聚氨酯弹性体

聚氨酯弹性体系由软链段和硬链段交替镶嵌组成的、含有许多－NHC－O－O基的极性高聚物,通过选择适当的软、硬链段结构及其比例,就可合成出具有良好物理机械性能,同时具有血液相容性和生物相容性的医用高分子材料。在本世纪５０年代,聚氨酯弹性材料已在修补骨骼裂缝上得到应用,后来又用于血管外科手术缝合修补的外涂层。美国犹他大学人造器官系最早采用聚氨酯材料制作人工心脏左心房分流泵的泵腔,并获得最佳临床研究结果,１９８２年美国牙科医生克拉克首例移植聚氨酯人工心脏获得成功。我国１９７９年试制成功聚氨酯胃镜软管,１９…     

一步法制备高硬度聚氨酯弹性体

通过对低聚物多元醇和扩链剂的选择,采用一步法研制出邵D硬度大于70,缺口冲击强度大于6kJ/m^2的高硬度聚氨酯弹性体,该体系的凝胶时间大于10min,既适合物工浇注又合机器浇注。     

热塑性聚氨酯弹性体力学性能和结晶性能的研究

采用预聚法合成聚氨酯弹性体,分别对预聚反应的时间、温度进行了考察,确定了合适的反应条件。讨论了软段的种类和数均相对分子质量对其结晶性能的影响,采用DSC和WAXD对弹性体的结晶性能和微相分离进行了分析,并对软段结构、扩链剂的类型、异氰酸酯的结构和助剂等进行了研究,结果表明,弹性体的结晶性能随软段结晶性的增加和数均相对分子质量的增大而增强,力学性能随软段结晶性的增强而增加,随扩链剂和异氰酸酯结构不同而差别较大,适当添加助剂对弹性体性能有补强作用。     

Low-temperature behavior of polyurethane elastomers

A study of the performance at low temperatures of various polyurethane elastomer systems, prepared from polyether and polyester diols with 2,4-toluene diisocyanate and 4,4′-methylenebis(2-chloroaniline), p,p′-diphenylmethane diisocyanate and 1,4-butanediol, and 4,4′-methylenebis(cyclohexylisocyanate) and methylenedianiline, has shown the polytetramethylene ether diols to impart the best low-temperature behavior to the elastomers. The properties studied were the apparent modulus of rigidity with the Clash and Berg torsional apparatus, the hardness with a Shore D Durometer, and the resiliency with the Bashore Resiliometer.     

Microphase-separated structure and mechanical properties of novel polyurethane elastomers prepared with ether based diisocyanate

A diisocyanate baring ether bonds, 1,2-bis(isocyanate)ethoxyethane (TEGDI), was used for the preparation of polyurethane elastomers (PUEs). The PUEs were synthesized with either TEGDI or HDI, poly(oxytetramethylene) glycol (PTMG), and curing agents by a prepolymer method. 1,6-Hexamethylene diisocyanate (HDI) was also used as a control diisocyanate. The TEGDI-based PUEs exhibited highly softened property on account of flexibility of TEGDI itself and weaker phase separation. Another TEGDI-based PUEs were prepared with either poly(oxypropylene) glycol (PPG) or poly(caprolactone) glycol (PCL). Microphase-separated structure of these TEGDI-based PUEs are quite different from those with general diisocyanates and the PUEs were made be greatly softened.     

Characterization of polyurethane network elastomers

Polyester urethane network elastomers with incorporated hard segment oligomers have been prepared by poly(ethylene adipate)glycol (PEA), 2,4-tolylene diisocyanate (TDI), and 1,4-butanediol (BD). These hard segment oligomers were hydroxy-terminated oligomers ([BD-TDI]n-BD; n=1,3), obtained by reacting BD with TDI. Concentrations of allophanate as a cross-linking site were determined by the amine degradation method. Hard segment moieties were obtained by a novel selective hydrolysis of soft segments in the elastomers. Molecular weight distributions of hard segment were measured by means of GPC. Mechanical and thermal properties were measured. Dependence of rubber elasticity on physical cross-linking between normal elastomers and the elastomers with incorporated hard segment oligomers were discussed.     

聚氨酯弹性体的新进展

简要分析了近几年来国内外聚氨酯弹性体的投资、生产和消费情况,综述了聚氨酯弹性体生产技术及应用方面的进展情况。     

Effects of low molecular weight aliphatic diols on the polyurethane elastomers prepared from hydroxyl-terminated polybutadienes

Hydroxyl-terminated polybutadienes were prepared by using azo initiators such as di(4-hydroxybutyl)-2,2′-azobisisobutyrate and di(3-hydroxybutyl)-2,2′-azobisisobutyrate, one of which contains primary and the other secondary hydroxyl groups. The effects of aliphatic diols and 2,4-toluene diisocyanate (TDI) in the presence of dibutyltindilaurate (DBTDL) as catalyst, on crosslinking of primary and secondary hydroxyl groups, were studied. Polyurethane elastomers from these polymers are prepared by using different ratios of diols, 2,4-toluene diisocyanate and catalyst. Physical properties such as hardness, tensile strength, 100% modulus, and elongation at break of these polymers were studied with a view to compare them with the physical properties of elastomers prepared from ARCO R-45M.     

Rheological characterization of thermoplastic polyurethane elastomers

The relationship between the rheological properties and composition of eight thermoplastic polyurethane elastomers (TPUEs) was evaluated using a stress‐controlled rheometer. The composition of the TPUEs was changed by varying the OH/NCO ratio, the chain extender and the molecular weight of the macroglycol used in the synthesis. A high molecular weight macroglycol and a low OH/NCO ratio improved the rheological properties of the TPUEs due to the formation of longer or more abundant soft segments, respectively. The nature of the chain extender influenced the rheological properties to a lesser extent. © 2000 Society of Chemical Industry     

Microstructure of as-polymerized thermoplastic polyurethane elastomers

Ten segmented polyether-urethane thermoplastics were studied in the as-polymerized state. Polyethersegment, number-average molecular weight and molecular weight distribution were varied among the set of polymers, as were the molar ratios of diisocyanate to diol chain extender to polyether glycol. Experimental techniques included differential scanning calorimetry, dynamic mechanical analysis, volume-temperature measurements, X-ray diffraction and hot-stage, polarized-light microscopy. At room temperature the materials possessed non-impinging spherulites, about 10 μm in diameter, in a non-birefringent matrix. X-ray diffraction from these same films showed no crystallinity, except in two cases. The spherulites irreversibly disappeared in the temperature range 350–400 K, accompanied by sharp decreases in dynamic modulus and a small thermal transition. Thermal disruption of urethane-dominated domains was observed at considerably higher temperatures, from 400–520 K, depending on molecular structure. Polyether crystallite melting was seen only below 305 K. These observations can be explained by a polymerization-solidification scenario which assumes: (1) de-mixing of isocyanatecapped prepolymers to form spatial gradients based on the urethane weight fraction of the prepolymer chains, and (2) decomposition of the polymerizing melt by nucleation and growth on a molecular scale to form polyurethane-rich spherulites during the reaction.     

Thermal behavior of cast polyurethane elastomers

Thermal properties like glass transition temperature (T_g), initial decomposition temperature (idt), integral procedural decomposition temperature (ipdt), and temperature at various % weight loss of a number of polyurethane systems are reported in this paper. Glass transition temperature was determined on TMA, and other thermal properties were determined by thermogravimetry. The experiments were designed to understand various factors such as length of chain extender moiety, flexibility of chain extender units by substitution of ether link in the diol chain, nature of bonds (unsaturation) in the extender unit, and nature of diisocyanates.     

耐热型聚氨酯弹性体的合成

催化合成了甲苯二异氰酸酯的部分三聚体异氰脲酸酯,然后与聚醚二元醇反应,用二步法手工浇注成异氰脲酸酯改性的聚氨酯弹性体。用红外光谱法证实了产物中异氰脲酸酯的存在。根据用二正丁胺法测得的NCO基团的质量分数可计算出异氰脲酸酯的质量分数,用热重法分析了产物的热稳定性。结果表明,与普通聚氨酸弹性体相比,合成的改型聚氨酯弹性体的热稳定性得到了明显提高。     

Effect of a homogeneous magnetic field on the viscoelastic behavior of magnetic elastomers

Viscoelastic behavior of highly elastic magnetic elastomers has been studied by three different experimental techniques: elongation, static and dynamic shears. It has been shown that the elastic modulus of the materials increases considerably in an external homogeneous magnetic field of up to 0.3 T (100-fold increase of the tangential modulus has been observed at small 1-4% deformations). The appearance of the new effect of pseudo-plasticity induced by the magnetic field has been observed leading to a considerable (up to 100-fold) increase in the shear loss modulus of the composites.