A smart hollow filament with thermal sensitive internal diameter

In this work, a thermoplastic shape memory polyurethane was prepared via melt polymerization and a corresponding shape memory hollow fiber was fabricated via melt spinning. The fiber mechanical properties, especially shape memory effect, were characterized by static tensile, thermo‐mechanical cyclic tensile testing. The hollow fiber switching temperature was the melting transition temperature of the soft segment phase at about 41°C. The tenacity of the hollow fiber was about 1.14 cN/dtex, and breaking elongation was 682%. The shape fixity ratio was above 87% and the recovery ratio was above 89%. The internal diameter of the hollow fiber could be noticeably changed and the deformed fiber cross‐section could be well fixed. Once heated above the soft segment phase melting transition temperature, the hollow fiber internal hole recovered to its original diameter. The results from differential scanning calorimetry, X‐ray diffraction, and dynamic mechanical analysis were used to illustrate the mechanism governing the mechanical properties and shape memory effect especially. Due to the changes of the hollow fiber and the internal diameter affect of the physical properties of the prepared products, this fiber may be used in smart textiles for thermal management, or as stuffing of pillows and mattresses, which can adjust to body contours. Furthermore, the findings suggest that this kind of hollow fiber with thermal sensitive internal diameter could be used in smart filtration, drug‐controlled release, and liquid transportation in vivo. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of superfine silk protein powders on mechanical properties of wet‐spun polyurethane fibers

Mechanical measurements were employed to investigate the effects of three types of superfine silk protein powder on tensile strength, elongation, and elasticity of wet‐spun Pellethane^® 2363‐80AE polyurethane (PU) fiber. These superfine silk protein powders included undegummed silk (with both native silk fibroin and sericin, water insoluble), native silk fibroin (with native silk fibroin only, water insoluble), and regenerated silk fibroin (with regenerated silk fibroin only, water soluble) in powder form. Experimental data derived from the mechanical measurements illustrated that the miscibility between the PU and regenerated silk fibroin were superior to that between PU and the other two silk proteins. This may be attributed to the similar chemical structure and microphase separation of PU and regenerated silk fibroin with lower molecular weight than native silk fibroin. This preliminary work may provide some information for biomimetic processing of silk‐inspired PU biofibers, which combine elasticity of synthetic PU with biofunction of natural silk fibroin for special biomedical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Flexible cross‐linking by both pentaerythritol and polyethyleneglycol spacer and its impact on the mechanical properties and the shape memory effects of polyurethane

A series of polyurethane (PU) polymers cross‐linked laterally by pentaerythritol and polyethyleneglycol (PEG) spacers were compared with linear PU. The PU was composed of 4,4′‐methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol), 1,4‐butanediol (BD), pentaerythritol, and PEG‐200 as a spacer. PEG‐200 connected the pentaerythritol hydroxyl groups of two PU chains with MDI as a connecting agent. The phase separation between hard and soft segments was disrupted by the PEG crosslinking, and T_m did not change with an increase in cross‐linking content. Instead, the cross‐link density increased with an increase of pentaerythritol content. A significant increase in maximum stress compared with linear PU was attained, together with an increase in strain. The combination of both pentaerythritol and PEG‐200 in the PU resulted in the improvement of both stress and strain, unlike in the conventional cross‐linking method. The shape recovery increased to 90% and did not decrease after three test cycles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

水性聚氨酯胶黏剂的改性研究进展

水性聚氨酯胶黏剂含有极性很强、化学活泼性很高的异氰酸酯基（-NCO）和氨酯基（-NHCOO-）,使之具有优良的化学粘接力,其不污染环境,应用领域、用途也愈来愈广泛。阐述了水性聚氨酯的制备方法、分类,并对自乳化法制备工艺中的几种方法作了一个简单的比较。通过分析环氧树脂、丙烯酸酯、有机硅改性水性聚氨酯胶黏剂的研究状况及优缺点,进而介绍了丙烯酸树脂和有机硅对水性聚氨酯的多重复合改性及其应用,提出了对水性聚氨酯胶黏剂发展的几点看法。     

水性双组分聚氨酯金属涂料及其在线施工工艺的研究

以水性聚氨酯树脂为原料研制了金属用水性双组分聚氨酯涂料,并对其在线施工工艺进行了探索研究。经上线试验,证明其涂膜性能接近或优于技术指标要求。     

聚氨酯固化剂合成反应动力学

以具有三官能分枝的三羟甲基丙烷(TMP)为扩链剂,与甲苯二异氰酸酯(TDI)合成了聚氨酯固化荆.采用红外光谱(FT-IR)分析和化学滴定法分析反应体系中的-NCO浓度,考察了三羟甲基丙烷与甲苯二异氰酸酯的加成反应动力学.实验结果表明,当羟基浓度较大时,TDI与TMP反应遵循二级反应动力学.其表观二级反应速率常数随反应温度和羟基浓度的增加而增大.     

短切玻纤对硬质聚氨酯力学性能和形态结构的影响

采用一步法制备了玻纤增强硬质聚氨酯的复合材料(RPU).与长径比为20和100的玻纤相比,长径比为40的玻纤增强材料的弹性模量增加了55%,而前者增强材料的弹性模量仅分别提高38.7%和41.7%;该材料增强的压缩弹性模量与拉伸弹性模量规律几乎一致.SEM图表明:适宜长径比的纤维本身的拉伸强度对于硬泡塑料的力学性能增强起了重要作用.     

水性聚氨酯合成的红外光谱研究

通过红外光谱（IR）研究了DMPA不同加入方法对产物结构影响;跟踪分析了整个水性聚氨酯（WPU）合成反应的过程;剖析了用CMA1044或T1136合成的水性聚氨酯成膜物在水解前后;分析了水性聚氨酯在成膜前后的基团变化。结果表明：DMPA不同加入方法对产物结构影响不大;聚酯T1136合成的水性聚氨酯在耐水解性方面较CMA-1044所合成的水性聚氨酯好;内乳化阴离子水性聚氨酯的成膜机理主要是粒子的聚集而不存在化学反应。     

水性聚氨酯的原位细乳液聚合规律(Ⅰ)加聚/水解反应的竞争

采用异佛尔酮二异氰酸酯(IPDI)与憎水性二醇进行原位细乳液聚合制备水性聚氨酯,根据已建立的FTIR定量分析方法来表征聚合产物结构,通过产物中氨酯键/脲键的浓度比来研究主反应（加聚）与副反应（水解）的竞争。考察了憎水性二醇、乙烯基单体、反应温度、催化剂和乳化剂等因素对主副反应竞争情况的影响,并建立细乳液中加聚与水解反应竞争的物理模型。研究发现,二醇的反应活性越高越有利于加聚反应;乙烯基单体的引入能够抑制水解反应,促进加聚反应,而且其水溶性越小,加聚反应更容易在竞争中占优势;降低反应温度和增加催化剂浓度可促进加聚反应,抑制水解反应。     

车灯用湿气固化热熔胶的研制

用多元醇、二苯基甲烷4,4-二异氰酸酯（MDI）,合成了车灯用湿固化聚氨酯热熔胶粘剂。研究了胶粘剂的黏度、黏度稳定性和初粘力等性能,结果表明,当高结晶性聚酯和热塑性聚酯用量在10％和15％时,胶粘剂剥离强度达到980N／25mm耐热性达到180℃,基本上满足了汽车灯具密封与装配的要求。