不同硬段含量嵌段聚脲合成及性质的研究

用两步溶液聚合法合成了硬段含量不同的一系列热塑性嵌段聚脲.研究了影响反应的各种因素.所得聚脲是线性和无定形的.用DSC和DMS法初步研究了这些聚脲的性质,随硬段含量增加.聚脲从软弹性体转变为高模量的硬塑料.     

硬链段浓度对RIM交联聚氨酯结构和性能的影响

用l-MDI/1,4-BDO/PPO-EO快反应体系,考察硬段浓度对聚氨酯结构与性能的影响。发现样品的交联度、模量和抗张强度随硬段浓度增加而提高,交联趋向均匀,断裂伸长率在浓度30％处出现最大值。ATR-FTIR和DSC分析表明,微相分离程度随硬段浓度增大而降低。     

RIM聚氨酯脲的微相分离的DSC研究──硬段结构和含量对微相分离的影响

用ＤＳＣ法研究了二乙基甲苯二胺和４，４＇－氨基二苯基甲烷（ＭＤＡ）扩链的硬段含量为２７％～６０％的两个系列的反应注射成型（ＲＩＭ）聚氨酯脲（ＰＵＵ）弹性体的微相分离。聚合反应动力学对ＲＩＭＰＵＵ的微相分离有很大影响．随着硬段浓度的增加微相分离程度下降，ＭＤＡ扩链系列聚合总反应速度快，微相分离驱动力弱，在硬段生成反应比软段生成反应快的条件下，该系列的微相分离程度较低。聚合总反应快，且硬段间氢键化作用很强的性质造成ＲＩＭＰＵＵ非平衡的形态。聚合总反应速度的增加相当于微相分离驱动力的下降。     

不同硬段含量脂肪族聚脲的结构与性能研究

通过端氨基聚醚、异佛尔酮二异氰酸酯和异佛尔酮二胺反应 ,合成了一系列不同硬段含量的脂肪族聚脲 ,并用DSC和FTIR等考察了硬段含量对聚脲的微观结构与力学性能的影响 .研究结果表明 ,聚脲呈现部分微观分相的形态 ,随硬段含量增加 ,聚脲中软段和硬段间的相容性提高 ,脲羰基的氢键化程度增加 ,但软段的玻璃化转变温度变化不大 ;此外 ,材料的拉伸强度、撕裂强度和硬度等也随着硬段含量的增加而显著提高 .     

CAMDA扩链聚氨酯脲的硬段对形态与性能的影响

由红外光谱、核磁共振及质谱分析证实了所合成的3-氯-3’-甲氧基-4,4’-二氨基二苯基甲烷(CAMDA)具有预期的化学结构.用RIM方法制成的CAMDA基聚氨酯脲(PUU)性能接近于DETDA扩链的PUU.用快速手工浇注法制备了一系列由CAMDA扩链的不同硬段含量的PUU样品.采用DSC、SEM观察了硬段含量由10％增加到45％PUU形态的变化,并测量了力学性能.实验结果表明:随着硬段含量增加,PUU的形态由平行间隔的软、硬链段富集区经相互穿叉的软、硬段富集区,进一步聚集成硬链段富集球状超级结构,强度亦相应提高.     

多嵌段聚硅氧烷聚脲共聚物及双离子型聚硅氨酯的表面性质的研究

本文利用光电子能谱(ESCA)和表面接触角研究了多嵌段聚硅氧烷聚脲共聚物(PUSE)和双离子型聚硅氨酯(PUSM)的表面性质,发现PUSE和PUSM中的软段聚硅氧烷均在表面富集;提高本体的相分离程度,更有利于软段的表面富集;但在50层内,硬段仍有一定的比例,表面层仍是多相结构。在PUSE中,接触角和凝血时间随聚硅氧烷软段比例增加而增加,在PUSM中,随离子化程度的提高,亲水性提高,接触角变小,凝血时间缩短。     

嵌段聚酯型聚脲氨酯弹性体的动态力学性能

聚氨酯(PU)的微区结构和宏观力学性能之间的关系是PU的一个重要课题。本文用动态力学方法对基于4,4'-二苯基甲烷二异氰酸酯(MDI),乙二胺(ED)和聚已二酸丁二醇酯(PBA)的嵌段聚酯型聚脲氨酯(PUU)弹性体进行了研究,探讨了不同软段分子量和硬段     

聚合物反应注射成型

本文简要地介绍了反应注射成型(RIM)的发展,RIM的化学体系,RIM过程和制品的成型,RIM过程的主要特点及RIM聚氨酯的主要组分。     

Thermal Aging Effect on Mechanical Properties of Polyurethane

This study concerns the effect of thermal aging on mechanical properties of polyurethane. Polyurethane samples were exposed at 85° and 120°C under inert atmosphere. Mechanical tests were carried out on these samples the aging period. Tensile tests were performed to see the effect of aging on elastic modulus (E), stress (σ_r), and strain (?_r) at break. It was shown that there are two distinct periods. Due to aging, E and σ_r increase in the first period, then they decrease in the second period. ?_r decreases first and then increases. Fatigue tests were performed on unaged and aged samples. It was shown that the fatigue behavior of polyurethane (PU) is improved the same way during the first stage of aging. In the second step, the number of cycles to failure increases due to aging. The results show that aging has an important effect on mechanical properties of PU. The strain at break decreases during the first step of aging due to post-cross-linking and then increases due to chain scission in the network. Based on these results, the effect of cross-linking and chain scission on the mechanical properties of PU was discussed.     

Dynamic mechanical analysis of RIM nylon-6

The β relaxation process was shown to occur at different temperatures and exhibit a different activation energy for dry and wet samples prepared by reaction injection molding (RIM) of Nylon-6. By employing a low operating frequency and controlled low moisture levels, it became possible to distinguish the two β relaxation processes, β₁ and β₂, in one sample by dynamic mechanical spectroscopy. It was shown that while β₁ was associated with moisture in the sample, β₂ was related to a structural mechanism independent of moisture. The effect of moisture content on the chain-chain association (α relaxation process) and chain-water association (β₁, relaxation process) in nylon-6 was assessed. The annealing mechanism of RIM Nylon-6 at 85°C was probed by both dynamic mechanical spectroscopy and x-ray diffraction.     

Thermal and Mechanical Properties of Esterified Lignin in Various Polymer Blends

Lignin is an abundant polymeric renewable material and thus a promising candidate for incorporation in various commercial thermoplastic polymers. One challenge is to increase the dispersibility of amphiphilic lignin in lipophilic thermoplastic polymers We altered Kraft lignin using widely available and renewable fatty acids, such as oleic acid, yielding more than 8 kg of lignin ester as a light brown powder. SEC showed a molecular weight of 5.8 kDa with a PDI = 3.80, while the T_g of the lignin ester was concluded to 70 °C. Furthermore, the lignin ester was incorporated (20%) into PLA, HDPE, and PP to establish the thermal and mechanical behavior of the blends. DSC and rheological measurements suggest that the lignin ester blends consist of a phase-separated system. The results demonstrate how esterification of lignin allows dispersion in all the evaluated thermoplastic polymers maintaining, to a large extent, the tensile properties of the original material. The impact strength of HDPE and PLA blends show substantial loss upon the addition of the lignin ester. Reconverting the acetic acid side stream into acetic anhydride and reusing the catalyst, the presented methodology can be scaled up to produce a lignin-based substitute to fossil materials.     

星形SIS嵌段共聚物的动态力学性能

本文报导了用粘弹谱仪对组成相同、支链分子量相同而支化度不同的,以及支化度相同、支链分子量不同的系列星形SIS嵌段共聚物的测试结果,实验发现:支链分子量是影响各相玻璃化转变温度和动态杨氏模量E′的主要因素,支化度对各相玻璃化温度影响很小,但是对E′影响是明显的。     

微孔聚乳酸支架材料的热稳定性与动态热机械特性

采用无溶剂二氧化碳固态发泡技术,在2.5、3.5、4.0和5.0 MPa饱和压力下制备了泡孔孔径为350-20μm的聚乳酸支架材料.利用热重分析技术、动态热机械分析技术和扫描电子显微镜技术,测定了材料的起始分解温度、分解速率、储存/损耗模量和损耗因子等参数,并利用Kissinger、Ozawa-Doyle和Vyazovkin方程进行了热分解动力学计算,推算了氮气环境下材料的降解时间和使用寿命.结果表明,随着发泡压力的减小,支架材料的泡孔孔径增大,材料的柔韧性增强,表观活化能降低,降解时间缩短.     

Cast Polyurethanes: Effect of Chain Extenders on Thermal Mechanical and Dynamic Mechanical Properties

Effects of various diol chain extenders on thermal, mechanical, and viscoelastic properties of polyurethanes are discussed. Elastomers were prepared by using polyester (polyethylene-co-propylene adipate), toluene-2,4-diisocyanate, and α,ω-aliphatic diols. The properties imparted by the extenders are explained on the basis of the number of methylene carbons in the extenders. Butanediol-extended polymer showed superior properties, which are ascribed to regularity in the backbone chain of the polymer and ease of formation of hydrogen bonds.     

FTIR快速跟踪聚氨酯脲的反应注射成型研究

ＦＴＩＲ快速跟踪聚氨酯脲的反应注射成型研究罗宁，潘肇琦，王得宁，应圣康（华东理工大学材料科学研究所，上海，２００２３７）关键词聚氨酯脲，红外光谱，反应注射成型，动力学，相分离反应注射成型（ＲＩＭ）是生产聚氨酯制品的重要技术。以二醇扩链的聚氨酯的ＲＩＭ...