Effect of nanoparticles orientation on morphology of polymeric nanocomposite foams: preparation of foamed nanocomposite fibers by supercritical carbon dioxide

ABSTRACT

Polymeric foams have received increasing attention in both academic and industrial communities. Using of nanoparticles as heterogeneous nucleation agent has been verified as one of the most valid means to enhance cell nucleation and improve cell morphology. However, few researches have been conducted to investigate the effect of the nanoparticles’ spatial orientation on their nucleation efficiency. In this work, to study the influence of the orientation of nanoparticles on their performance in improving morphology of polymeric foam, thermoplastic polyurethane (TPU) composite fibers with different nanoparticles (carbon nanotubes, graphene and SiO₂) were prepared by using different traction speeds. The different traction speeds lead to different orientation state of the nanoparticles which then resulted different nucleation effect. It was found that carbon nanotubes (CNTs) were easily oriented and aligned along the fiber length direction under the high traction speed, while graphene and SiO₂ nanoparticles did not show orientation under the traction speed in this study. As a result, the foam of TPU/CNTs composite fibers from high traction speed exhibited a much smaller cell size and higher cell density compared to the foams of the fibers from low traction speeds, while TPU/graphene, and TPU/SiO₂ composite fibers with different traction speeds showed almost similar cell size and size density after foaming, indicating that the orientated nanoparticles possessed higher heterogeneous nucleation efficiency. To our best knowledge, this work, for the first time, demonstrated the high nucleation effect of the aligned nanoparticles, which hopefully open a new path for improving the cell morphology of polymeric foam materials.     

Flexible poly(styrene-ethylene-butadiene-styrene) hybrid nanofibers for bioengineering and water filtration applications

Among the thermoplastic elastomers that play important roles in the polymer industry due to their superior properties, styrene-based species and polyurethane block copolymers are of great interest. Poly(styrene-ethylene-butadiene-styrene) (SEBS) as a triblock copolymer seems to have the potential to meet many demands in different applications due to various industrial requirements where durability, biocompatibility, breaking elongation, and interfacial adhesion are important. In this study, the SEBS triblock copolymer was functionalized with natural (Satureja hortensis, SH) and synthetic (nanopowder, TiO₂) agents to obtain composite nanofibers by electrospinning and electrospraying methods for use in biomedical and water filtration applications. The results were compared with thermoplastic polyurethane (TPU) composite nanofibers, which are commonly used in these fields. Here, functionalized SEBS nanofibers exhibited antibacterial effect while at the same time improving cell viability. In addition, because of successful water filtration by using the SEBS composite nanofibers, the material may have a good potential to be used comparably to TPU for the application.     

高弹性MXene/TPU纳米纤维纱线的制备及其应变传感性能

采用静电纺丝技术制备了热塑性聚氨酯弹性体(TPU)纳米纤维膜,并通过“Biscrolling”的方法制备高弹性过渡金属碳化物/氮化物（Ti3C2Tx MXene）改性TPU纳米纤维纱线。通过SEM、电阻测试、传感性能测试等对复合纳米纤维纱线进行结构和性能表征。结果显示,随着MXene负载量增加,复合纱线的强度先增加后降低,断裂伸长率可高达459%以上,展现出优异的弹性和弹性回复性;MXene片可在纳米纤维纱线表面及内部形成连续导电薄膜,赋予复合纱线较好的导电性（电阻76 Ω/cm）。纱线的应变传感性能测定实验表明,MXene/TPU纳米纤维纱线的传感系数可高达477.86,线性度高达0.995,高于绝大多数文献报道的纱线传感器,并且可以监测人体的各种运动状态,展现出较好的应变传感性能,在智能可穿戴领域展现出广泛的应用前景。     

热塑性聚氨酯弹性体加工成型技术及应用

研究和介绍热塑性聚氨酯弹性体原料的生产，制品的热加工成型过程。尤其对制品加工过程中材料准备、着色剂填加、回收料使用、注射模塑、挤出、压延、粘接及成品的后处理等作了较详细的论述。最后给出了挤出，注射两大主要成型制品在工业上的一些主要应用。     

TPU／ABS塑料合金的研制

通过熔融共混法制备了ＴＰＵ／ＡＢＳ塑料合金，并以此材料试制了塑料纬纱管。讨论了ＴＰＵ含量，共混工艺等因素对合金力学性能和形态结构的影响，结果表明，在ＴＰＵ含量为５－２０％时，所制ＴＰＵ／ＡＢＳ塑料合金具有良好的综合性能，尤其在冲击强度和耐磨性能方面都有明显改进。用此材料制造的纬纱管，经检测，各项性能均达到了各颁标准，经有关厂家初步应用认为，达到了纺机配件的使用要求。     

聚甲醛的强韧化改性研究

分别以热塑性聚氨酯和短切玻璃纤维为增韧剂和增强剂，以传统的共混方式，对聚甲醛进行了增韧和增强改性研究，获得了强度和韧性同时提高的改性材料。     

PC／TPU共混物的流变性能

用毛细管流变仪研究了聚碳酸酯（ＰＣ）及聚碳酸酯／热塑性聚氨酯弹性体（ＰＣ／ＴＰＵ）共混物的流变性能。实验结果表明：ＰＣ熔体粘度对剪切速率（γ）不敏感，而对温度（Ｔ）敏感。温度升高，ＰＣ粘度降低。加入ＴＰＵ大大改善了共混物的流动性能，使共混物的成型加工变得容易进行。当ＴＰＵ含量为４０份时，共混物的熔体粘度出现一极小值。加入不同第三组分对于降低共混物的熔体粘度效果不同，第三组分Ｅ对共混物有增粘作用     

TPU增韧改性PBT的研究

分别采用醚型和酯型热塑性聚氨酯(TPU)对聚对苯二甲酸丁二醇酯(PBT)进行增韧改性，并对共混物的性能、形态结构及流变性能进行了研究。结果表明：醚型TPU对PBT有较好的增韧效果，共混物有明显的两相，PBT为连续相，TPU为分散相，当m(PBT)／m(TPU)=100／75时，拉伸屈服强度可达41．7MPa，缺口冲击强度326 J／m，是纯PBT的两倍，断裂伸长率330％；醚型TPU对PBT共混物的表观粘度有较大的影响，当m(PBT)／m(TPU)=100／50时．共混物表观粘度只有纯PBT的20％。     

车辆起步车速测量技术的研究

介绍了装有自动机械式变速箱 (automaticmechanicaltransmission ,AMT)的车辆起步车速的测量技术。起步车速的精确测量对离合器控制规律 ,尤其是离合器半接合点的确定至关重要。由于选用了霍尔式零速传感器和单片机MC6 8376的TPU模块以及相应的检测软件 ,使得车辆起步车速的测量更加精确 ,从而为离合器的优化控制提供了可靠的依据     

热塑性弹性体(TPE)及其在纺织器材上的应用

简要介绍了几种常用TPE的结构、性能、应用特点及其在纺织器材上的应用。