微相分离对聚氨酯弹性体耐热性能的影响研究

在聚氨酯弹性体固化过程中添加微相分离促进荆,对不同温度下的热失重分析（TGA）和力学性能高温保持率进行了对比分析,分析表明,添加了微相分离促进剂的聚氨酯弹性体耐热性能得到了提高。     

微相分离促进剂对MDI型聚氨酯弹性体的耐热性能影响研究

在聚氨酯弹性体固化过程中添加微相分离促进剂,通过差示扫描量热分析（DSC）和动态力学性能测试（DMA）表明,微相分离促进剂的加入提高了4,4′-二苯基甲烷二异氰酸酯（MDI）弹性体的微相分离程度;通过不同温度下的热失重分析（TGA）和力学性能高温保持率对比分析表明,添加了微相分离促进剂的聚氨酯弹性体耐热性能得到了提高。     

聚氨酯弹性体耐热性的影响因素

综述了近年来聚氨酯弹性体耐热性方面的研究进展,讨论了低聚物多元醇、异氰酸酯、催化剂、交联剂、扩链剂等对弹性体耐热性的影响。有机杂环引入、产生交联结构、加入无机填料、与纳米材料复合等对弹性体耐热性能有明显改善,可以使弹性体材料在较高的温度下具有优异的机械性能。     

聚氨酯弹性体结构与耐热性能的研究

简述了聚氨酯弹性体的结构特点及近年来对聚氨酯弹性体耐热性方面的改性研究进展,包括通过改变聚合物多元醇结构,选择适当的异氰酸酯及扩链剂,在聚氨酯分子内引入杂环,加入填料,以及改变工艺条件等。     

聚氨酯弹性体耐热性的影响因素

讨论了多异氰酸酯，聚合物多元醇，扩链剂，分子内基团，杂环，离子基团对聚氨酯弹性体耐热性能的影响。指出开发新原料，引入热稳定杂环，严格控制反应条件和原料的纯度及配比，是提高聚氨酯弹性体耐热性的有效途径。     

提高聚氨酯弹性体耐热性能的研究

在２，４，６－三（二甲氨基甲基）苯酚催化剂作用下，使－ＮＣＯ三聚生成异氰脲酸酯。采用异氰酸酯三聚法和预聚物三聚法，对聚氨酯弹性体，进行ＩＳ耐热改性，考察了改性方式及改性程度对ＰＵＥ性能的影响。     

聚氨酯弹性体的力学性能影响因素研究

研究了合成方法,软段及硬段组成结构,熟化条件等因素对聚氨酯弹性和学性能的影响,结果表明,聚氨酯弹性体的结构与组成,以及由此引起微相分离程度的变化,是影响弹性体性能的重要因素,不同的低聚物二醇,二异氰酸酯及扩链剂合成的弹性体性能不同,采用预聚法,以及适当熟化有助于提高弹性体的性能。     

NDI型聚氨酯弹性体的合成与其耐热性能研究

以1,5-萘二异氰酸酯(NDI)和甲苯二异氰酸酯(TDI)分别与聚己二酸乙二醇丙二醇酯二醇(PEPA)合成了聚氨酯弹性体,通过热失重分析和差示扫描量热分析发现,NDI型聚氨酯弹性体的热分解温度比TDI型聚氨酯弹性体高,说明NDI型聚氨酯弹性体具有更好的耐热性能;通过不同温度下弹性体的力学性能高温保持率对比分析,也说明了NDI型聚氨酯弹性体的耐热性能优于TDI型聚氨酯弹性体。     

聚氨酯弹性体耐热性能的改善

1 前言 聚氨酯弹性体(PUE)在工业上已得到广泛应用,但由于PUE的耐热性差,制约了它在高温环境、高动态环境中的应用。因此改善PUE的耐热性是PUE研究领域中十分重要的课题。2 PUE硬段结构与耐热性能的关系 PUE是嵌段共聚物,软段相是橡胶态,硬段相呈玻璃态或半结晶态,两相的不相溶性形成了二相结构,两相分离的越好,PUE的耐热性能越好,耐热性主要由硬段相结构     

助剂对透明聚氨酯弹性体耐黄变性能的影响

通过正交试验考察了在不同环境下不同的抗氧剂、紫外线吸收剂、助抗氧剂以及光稳定剂对透明聚氨酯弹性体耐黄变性能影响,优化了不同环境下的最佳助剂组成.结果表明:在室内避光条件下影响材料耐黄变性能的助剂主次顺序为助抗氧剂＞紫外线吸收剂＞光稳定剂＞抗氧剂;在室内日光灯照射条件下影响材料耐黄变性能的助剂主次顺序为紫外线吸收剂＞助抗...     

聚醚-聚硅氧烷嵌段共混聚氨酯弹性体的研究

用共聚混合法制成聚硅氧烷-聚醚型嵌段聚氨酯,结果表明:在聚合物主链引入硅氧烷后,弹性体力学性能略有升高,对三元乙丙橡胶,异戊二烯橡胶的粘合剥离强度得到提高。NCO/OH当量比、硅氧烷和MOCA用量对材料的物理性能有很大的影响。DSC的分析表明,引入的聚硅氧烷链段主要分布于弹性体分子中的软段,使弹性体的相分离更加明显。     

Hierarchical structure of phase‐separated segmented polyurethane elastomers and its effect on properties

Polyurethanes were prepared from 4,4′‐methylenebis(phenyl isocyanate), 1,4‐butanediol and poly(1,4‐butanediol adipate) polyester polyol. The hydroxyl functional group ratio of polyol/total diol was kept constant at 0.4, while the ratio of the isocyanate and hydroxyl groups (NCO/OH ratio) changed between 0.90 and 1.15. The polymers were prepared by one‐step bulk polymerization in an internal mixer. They were characterized using a number of methods including Fourier transform infrared spectroscopy, wide‐ and small‐angle X‐ray scattering, differential scanning calorimetry, dynamic mechanical analysis, light transmittance and tensile testing. Changing the stoichiometry modifies the molecular weight in accordance with the laws of stepwise polymerization, and the relative concentration of end groups also changes at the same time. Competitive interactions among various groups including chain‐end functional groups lead to the formation of slightly ordered phases of sub‐nanometre size at both ends of the composition range. These structures assemble into larger units at the 10 nm level, which associate further to even larger entities of micrometre size causing scattering of light and a decreased transparency of the samples. The order of the primary units, together with the number and size of assemblies at both higher levels, decrease as the composition approaches equimolar stoichiometry. The amount of less ordered amorphous phase has a maximum in this range. The stiffness of the polymers is determined by the amount of this phase, while ultimate properties are influenced also by molecular weight and the number of physical crosslinks formed. Copyright © 2010 Society of Chemical Industry     

耐热型聚氨酯的合成研究

以自制的含硅聚醚、聚氧化丙烯二醇(N-210)和2,4-甲苯二异氰酸酯(TDI)为主要原料,以氨丙基三甲氧基硅烷(DB-550)作为封端剂,制备耐热型PU(聚氨酯)。采用红外光谱(FT-IR)法、热失重分析(TGA)法对改性PU的结构和热稳定性能进行了分析,并探讨了各种因素对PU及其预聚体性能的影响。结果表明:当R值为1.5、预聚时间为3 h、预聚温度为40℃和m(自制含硅聚醚)∶m(N-210)=1∶7时,改性PU的耐热性和综合性能较好。     

The effect of mixed soft segment on the microstructure of thermoplastic polyurethane

In this work, we fixed the hard segment content (Ch%) and synthesized thermoplastic polyurethane (TPU) elastomers with one-soft segment (HTPB-PU, PTMG-PU, and PCL-PU) and bi-soft segment (PTMG-HPU and PCL-HPU), using 4,4′-diphenylmethane diisocyanate, 1,4-butanediol, and different oligomer diols as raw materials. This work was used to explore the impact of two polar diols (polytetrahydrofuran diol [PTMG]; polycaprolactone diol [PCL]) of the hydroxy-terminated polybutadiene (HTPB)-based TPU on the microstructure and macroscopic properties. Using Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry to characterize TPU, the results showed that the introduction of PCL was better than PTMG in promoting microphase mixing and crystallization, and reducing microphase separation. This result was closely related because the carbonyl group in PCL was stronger than the ether bond in PTMG in forming hydrogen bonds with ─NH bond. Through mechanical test and isopropyl alcohol (IPA) resistance test, the results showed that HTPB-based TPU with PCL (PCL-HPU) significantly improved tensile strength and elongation at break, and only a small reduction of Young's modulus was observed. PCL-HPU had the best retention of the IPA resistance of HTPB-based TPU.     

软段结构对聚氨酯弹性体性能的影响

分别以聚四氢呋喃二醇(PTMG)、聚己内酯二醇(PCL)、高顺式端羟基聚丁二烯(HTPB)和自由基聚合制得的端羟基聚丁二烯(FHTPB)为软段,采用溶液聚合两步法制得了四种聚氨酯弹性体(PUE)。通过拉伸试验、动态力学性能分析(DMA)、差示扫描量热(DSC)和热重分析等手段,考察了软段结构对它们室温及低温下力学性能、热性能等的影响。结果表明,四种PUE低温(-30℃)下的拉伸强度和断裂伸长率均大于室温下的对应值。这不仅与低温下软段诱导结晶所产生的自增强效应有关,也与软、硬两段的微相分离程度增大有关。相较于其他三种PUE,HTPB-PUE软段不仅玻璃化温度(T _g)最低,而且极性也最弱,因而微相分离程度高,具有优异的柔性,-30℃下其断裂伸长率仍达660%以上。PCL-PUE和PTMG-PUE因软段易结晶,且软段与硬段的微相分离程度低,则刚性强。低温循环拉伸试验表明,-30℃下HTPB-PUE和FHTPB-PUE有较强的弹性恢复能力,而PCL-PUE和PTMG-PUE则相对较差。DSC和DMA结果显示HTPB-PUE的T _g远低于其他三种PUE,其T _g(DSC)低至-103℃。此外,四种PUE的初始分解温度十分相近,均在270℃左右。     

耐热氨纶的研究现状

介绍了氨纶的生产现状;对比分析了干法纺丝、熔融纺丝、湿法纺丝和化学反应法的氨纶生产方法;阐述了聚氨酯脲和聚氨酯弹性体耐热性的改进原理和方法;详述了通过聚氨酯软段及硬段、扩链剂、交联剂、添加剂、熔融纺丝等手段改进氨纶耐热性的研究进展;指出使用合适的添加剂和扩链剂或多种改性方法综合运用将是今后提高氨纶的耐热性的主要方向。     

Cast polyurethane elastomers with improved dynamic fatigue resistance

Cast polyurethane (PU) elastomers have been widely used in dynamic applications, such as rollers and wheels, where a low heat buildup, high-loading resistance, and good cut-growth resistance are desired. Because of their different molecular structure, cast PU elastomers do not perform in the same way in highly demanding dynamic applications. Small variations in the viscoelastic properties can result in significant differences in the longevity of the wheels and rollers that are subjected to a large number of cyclic compressive deformations. Therefore, it is of great interest to understand dynamic performance of urethane elastomers based on various backbones. Dynamic mechanical analysis (DMA) is commonly used to differentiate the dynamic performance of elastomers, but it only provides characterization of the dynamic behavior of a given elastomer at small deformation in the linear viscoelastic regime, where information such as the heat buildup and load-bearing capability of elastomers cannot be obtained. As such, we developed a stress-controlled flexometer on the basis of the ISO4666/4 method that enabled measurement of the heat buildup and load-bearing capabilities of urethane elastomers in a large dynamic deformation environment. Moreover, a dynamometer was constructed to evaluate wheels based on different urethane elastomers under load at various speeds; this allowed close simulation of the urethane elastomers in a real application environment. In this article, the viscoelastic properties of cast urethane elastomers based on different backbones were studied by DMA. The heat buildup and load-bearing capabilities of the elastomers were investigated via the stress-controlled flexometer, and the performance of the wheels based on various prepolymer systems were evaluated with the dynamometer. Correlations between the material viscoelastic behavior and the heat buildup were established. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermoplastic polyurethane elastomers from modified oleic acid

Two novel potentially biodegradable thermoplastic polyurethane elastomers with unique structure and morphology were prepared from modified oleic acid. The hardness and mechanical properties were controlled by adjusting the soft segment concentration (SSC). Epoxidized methyl oleate was converted to methyl‐9‐ or ?10‐hydroxystearate (hydroxystearate) by catalytic hydrogenation. The formed hydroxystearate was transesterified with 1,6‐hexanediol to obtain polyesterpolyol with molar mass 2500. Segmented polyurethanes with 50% and 70% SSC were prepared using the prepolymer method by reacting polyesterpolyol with diphenylmethane diisocyanate and 1,4‐butanediol as chain extender. Thermal and mechanical properties of the polymers indicated good micro‐phase separation. Both soft and hard segments displayed a certain degree of crystallization. Tensile strengths were 18 and 2.4 MPa for samples with 50% and 70% SSC, respectively. Elongations of 130% (50% SSC) and 43% (70% SSC) were somewhat lower than in comparable materials, presumably due to lower molar mass. © 2014 Society of Chemical Industry