【作者】 杨鹏飞；

【导师】 付鹏；

【作者基本信息】 郑州大学 ， 高分子化学与物理， 2022， 硕士

【摘要】 形状记忆聚合物(SMPs)是一种智能材料,能对外界刺激作出响应。根据驱动方式的不同,SMPs可以分为热驱动型、电流驱动型、光驱动型、磁驱动型和溶剂驱动型SMPs。常见的SMPs大多数为热驱动型SMPs,热驱动型SMPs的形状记忆过程需要外部环境提供持续存在的热源,而间接驱动的方式使SMPs可以在一些特殊场所被应用,例如外太空,人体等。根据形状记忆过程是否可逆,SMPs可以分为单向SMPs(1W-SMPs)和双向SMPs(2W-SMPs)。1W-SMPs经过几十年的发展,对1W-SMPs结构与性能的关系已经相当成熟,但1W-SMPs由于形状记忆过程的不可逆性大大限制了其应用领域。2W-SMPs的形状记忆过程是可逆的,在一次编程之后即可多次使用。目前,大多数对2W-SMPs的研究都集中在化学交联结晶性聚合物方面,但对于物理交联结晶性聚合物的构效关系研究尚不明确。热塑性聚酰胺弹性体(thermoplastic polyamide elastomer,TPAE)是由聚酰胺硬段和聚酯或聚醚软段缩合聚合而成的(AB)_n型嵌段共聚物,其软硬链段的结晶性使TPAE具有两个温度相差较大的熔融转变温度和微相分离结构,这使TPAE具有实现双向形状记忆效应的潜力,因此对TPAE材料的热驱动双向形状记忆效应和电流驱动双向形状记忆效应的研究意义重大。本论文的主要内容如下:(1)不同软硬链段配比热塑性聚酰胺弹性体的双向形状记忆性研究以四种不同软硬链段配比的TPAE材料为研究对象,将其通过真空热压法制备成薄膜样条。TG测试结果表明四种TPAE材料具有良好的热稳定性,DSC和XRD结果显示在真空热压法制备的未经处理的四种TPAE材料中,T12材料和T22材料的硬段和软段都能结晶,而T11和T21材料只有硬段可以结晶。对储能模量和力学性能的测试结果表明,四种TPAE材料都具有优异的力学性能,并且四种TPAE材料的α转变温度大致在50℃附近,而β转变温度大致在-40℃左右。四种TPAE材料都能表现出准双向形状记忆效应和可逆双向形状记忆效应,并且四种TPAE材料的准双向形状记忆效应和可逆双向形状记忆效应受到TPAE材料的软硬链段配比、拉伸温度、降温速率、拉伸应力、形状回复温度等多种因素的影响,其中在T12材料准双向形状记忆效应的研究中,在8 MPa的拉伸应力下其响应应变变化量可达16.4%,形状回复率也接近100%;在T12材料可逆双向形状记忆效应的研究中,在300%的拉伸应变和20℃的形状回复温度时其响应应变变化量可达9.7%,形状回复率也接近100%。(2)热塑性聚酰胺弹性体复合材料的电流驱动双向形状记忆性研究以多壁碳纳米管(CNTs)为导电填料,T12粉末(0-150 um)为高分子基体,通过超声分散-溶剂蒸发法制备了T12/CNTs复合材料。研究表明T12/CNTs复合材料的导电逾渗阈值为3 wt%,T12/CNTs复合材料的表面最大温度随着电压和CNTs含量的增加而增加,并且当CNTs的含量为5 wt%时,T12/CNTs复合材料通电(110-150 V)产生的焦耳热足以触发T12/CNTs复合材料的形状回复行为。DMA结果表明,CNTs的含量对于准双向形状记忆效应和可逆双向形状记忆效应的影响是一致的,即较低CNTs含量时,T12/CNTs复合材料的响应程度和响应应变变化量要大于纯T12材料的响应程度和响应应变变化量;只有在较高CNTs含量的时候,T12/CNTs复合材料的响应程度和响应应变变化量才小于纯T12材料的响应程度和响应应变变化量,并且随着CNTs含量的增加,两者在下降。设计的双层SEBS/T12/CNTs-5复合样条通电后立刻产生了形状回复,其响应角度变化量为30°,并且可以通过电压和时间的调控来控制双层SEBS/T12/CNTs-5复合样条的响应角度变化量。更多还原

【Abstract】 Shape memory polymers(SMPs)are smart materials that can respond to external stimuli.According to the different actuation methods,SMPs can be divided into thermal-driven SMPs,current-driven SMPs,light-driven SMPs,magnetic-driven SMPs and solvent-driven SMPs.Most of the common SMPs are mainly thermal—driven SMPs which shape memory process requires the external environment to provide a persistent heat source.But the indirectly driving method enables SMPs can be applied in some special places,such as outer space,human body.According to the reversibility of the shape memory process,SMPs can be divided into one-way SMPs(1W-SMPs)and two-way SMPs(2W-SMPs).After decades of development,the relationship between 1W-SMPs structure and performance has been quite matured,but their application fields have greatly been limited due to the irreversibility of the shape memory process.The shape memory process of 2W-SMPs is reversible and can theoretically be used many times once programming.At present,most studies on 2W-SMPs focus on chemically cross-linked crystalline polymers,but the relationship between the structure and properties of physically cross-linked crystalline polymers is still unclear.Thermoplastic polyamide elastomer(TPAE)is a(AB)_n-type block copolymer formed by the condensation polymerization of polyamide hard segments and polyester or polyether soft segments.The crystallinity of the soft and hard segments of TPAE enables TPAE to have two widely different melting transition temperatures and a microphase-separated structure,which makes TPAE have the potential to realize the two-way shape memory effect.Therefore,it is of great significance to study the thermally driven two-way shape memory effect and the electric-driven two-way shape memory effect of TPAE materials.The main contents of this paper are as follows:(1)Two-way shape memory effect of thermoplastic polyamide elastomers with different ratios of soft and hard segmentsTaking four TPAE materials with different ratios of soft and hard segments as the research object which were prepared into thin film splines by vacuum hot pressing method.The TG test results show that the four TPAE materials have good thermal stability.The DSC and XRD results show that in the four untreated TPAE materials prepared by vacuum hot pressing,the hard and soft segments of the T12 material and the T22 material can be Crystallization,while T11 and T21 materials only have hard segments that can crystallize.The test results of storage modulus and mechanical properties show that all four TPAE materials have excellent mechanical properties,and theαtransition temperature of the four TPAE materials is roughly around 50℃,while theβtransition temperature is roughly around-40℃.All four TPAE materials can exhibit quasi-two-way shape memory effect and reversible two-way shape memory effect which are affected by various factors such as the ratio of soft and hard segments of the TPAE material,stretching temperature,cooling rate,tensile stress,etc.Among them,in the study of the quasi-bidirectional shape memory effect of T12 material,the response strain change can reach 16.4%under the tensile stress of 8 MPa,and the shape recovery ratio is also Close to 100%;in the study of the reversible two-way shape memory effect of T12 material,the response strain change can reach 9.7%at a tensile strain of 300%and a shape recovery temperature of 20℃,and the shape recovery ratio is also close to 100%.(2)Study on the current-driven two-way shape memory effect of thermoplastic polyamide elastomerT12/CNTs composites were prepared by ultrasonic dispersion-solvent evaporation method using multi-walled carbon nanotubes(CNTs)as conductive fillers and T12powder(0-150 um)as polymer matrix.The research shows that the conductive percolation value of T12/CNTs composites is 3 wt%,the maximum surface temperature of T12/CNTs composites increases with the increase of voltage and CNTs content,and when the content of CNTs is 5 wt%,the joule heat from energization(110-150 V)of the T12/CNTs composite is sufficient to trigger the shape recovery behavior of the T12/CNTs composite.The DMA results show that the content of CNTs has the same effect on the quasi-two-way shape memory effect and the reversible two-way shape memory effect,that is,when the content of CNTs is lower,the response degree and the change of the response strain of the T12/CNTs composite are larger than those of the pure T12 material.The response degree of T12/CNTs composites is smaller than that of pure T12 material only when the CNTs content is higher,and both decrease with the increase of CNTs content.The designed bilayer SEBS/T12/CNTs-5 composite spline produced a shape recovery immediately after energization,and its response angle varied by 3°.And the change of the response angle of the bilayer SEBS/T12/CNTs-5 composite spline can be controlled by the regulation of voltage and energization time.更多还原