基于共混物的形状记忆材料制备及其结构性能关系

发布时间：2018-06-22 15:48

本文选题：共混复合材料 + 动态交联反应　；参考：《西南交通大学》2017年硕士论文

【摘要】：形状记忆聚合物是一种具有大变形、刺激响应等特点的智能材料,在众多领域中均有潜在的应用,如航空航天、生物医疗、电子器件等。目前,在形状记忆聚合物领域中,人们研究最广泛的热致形状记忆聚合物是通过直接加热的方式来实现其形状记忆效应。关于这种热致形状记忆聚合物的研究虽已有很多,但还不能全面地了解热驱动形状记忆过程中微观结构的变化,仍需要深入探索。此外,相比于直接加热来实现形状记忆效应,光、电、磁等新型驱动方式有非接触、可远程控制等优势。因此,通过采用具有操作简单、实验周期短等优点的物理方法来开发新型响应的形状记忆聚合物,以及可满足特殊需求的多响应型形状记忆聚合物,成为了人们关注的热点。在此背景下,本论文采用熔融共混法和溶液共混法成功制备了共混型/复合型的形状记忆聚合物,深入研究了热致形状记忆共混物的结构性能关系及其形状记忆过程中的分子机理,获得了电场、水以及红外光响应的新型形状记忆聚合物,并阐述了相应响应形状记忆聚合物的发生机制。首先,为了阐明热驱动形状记忆过程中的结构变化与宏观性能之间的关系,采用双螺杆挤出的方式制备了一系列的聚乙烯-醋酸乙烯酯(Poly(ethylene-co-vinyl aetate),EVA)/聚乳酸(Poly(L-lactide),PLLA)共混物和动态交联EVA/PLLA共混物。研究表明:1)对于EVA/PLLA共混物,样品相结构的变化明显影响了其形状记忆性能,只有在共混物为双连续结构时,样品的形状记忆性能达到最佳。此外,由于EVA组分玻璃化转变对共混物样品的影响,在样品升温回复过程中存在一个明显的临界温度(53℃)。当回复温度低于53 ℃时,PLLA抑制样品回复;当回复温度高于53 ℃时,PLLA促进样品回复;2)对于动态交联EVA/PLLA共混物,PLLA结晶的引入使得共混物内存在两种固定相结构,一种是EVA组分中化学交联的网络结构,一种是PLLA结晶作为物理交联点的网络结构。通过调节PLLA结晶度的大小,探索了物理交联网络和相形貌对共混物形状记忆性能的影响,结果发现,PLLA的结晶能提高共混物的回复率,降低固定率,且具有高含量EVA的共混物表现出最优的形状记忆性能。进一步阐述了具有双连续结构的共混物在形状记忆过程中,其分子链结构、交联网络及结晶结构对形状记忆的作用。其次,为了获得三重形状记忆聚合物和电致形状记忆聚合物,采用密炼的方式制备了交联EVA/聚己内酯(Polycaprolactone,PCL)共混物,以及在质量比为60/40的EVA/PCL共混物中引入碳纳米管(Carbon nanotubes,CNTs)进一步获得了EVA/PCL/CNT复合材料。研究发现:1)对于交联EVA/PCL共混物,过氧化二异丙苯(Dicumyl peroxide,DCP)含量的增加明显改善了 EVA化学交联的程度,使得EVA组分中的交联网络更加完善。同时交联反应也提高了 EVA组分的粘度,使得共混物趋于呈现典型的双连续相结构。结果表明,具有典型的双连续相结构和完善化学交联网络的样品能够从临时形状完全回复到初始形状,表现出三重形状记忆的效果。2)预先理论估计了 CNTs的分散状态,并通过直接观察确认了在EVA/PCL/CNT复合材料中CNTs选择性分散于EVA组分。进一步计算获得复合材料的逾渗阈值为0.95 wt%。当CNTs的导电网络比较完善时,复合材料在外加电场下能够产生足够的焦耳热,导致样品温度升高到其转变温度,使得复合材料表现出优秀的电致形状记忆效应。再者,为了获得水致形状记忆聚合物,利用了 EVA的高弹性和聚乙烯醇(Polyving akohol,PVA)的亲水性,通过采用溶液共混的方式制备了 EVA/PVA共混物。结果发现由于EVA和PVA之间的相互作用,进而难以从共混物的相形貌中清晰地分辨出相应的组分;由于PVA的模量比EVA的高,共混物的模量会随着PVA含量的增加而增加。但又因水分子对PVA组分的亲和性及增塑作用,共混物的溶胀度和模量会随着样品浸水时间的增加而有明显的下降。正是基于共混物在不同含水程度下模量的差异,使得具有较高PVA含量的共混物能够表现出很好的水致形状记忆效应。最后,通过向聚氨酯(Polyurethane,PU)和PCL质量比为50/50的PU/PCL共混物中引入石墨烯纳米片(Graphene nanoplate,GNP),成功制备了具有光电双驱的形状记忆PU/PCL/GNP复合材料。研究表明,在以PCL/GNP为母料制备的复合材料中GNP能够实现良好的分散且不影响PU/PCL的相容性;当GNP的含量比较高时,PCL的结晶结构会发生变化,同时GNP也能够在PU/PCL基体中形成逾渗网络结构。从电学性能测试结果可知GNP的逾渗阈值为1.62wt%,随着GNP含量的增加,复合材料中GNP导电逾渗网络越加完善,在适当外加电场作用下,复合材料会表现出很好的电致形状记忆效应。此外,GNP的光热转换特性也使得复合材料在光照射下表现出优良的光热转换性能进而导致在相同的光照条件下,复合材料比共混物具有更快的回复速度。进一步利用GNP的光热,具有取向结构的复合材料能够实现复杂形状变化和自驱动性能。
[Abstract]:Shape memory polymer (shape memory polymer) is a kind of intelligent material with large deformation and stimulus response. It has potential applications in many fields, such as aeronautics and Astronautics, biological medicine and electronic devices. At present, in the field of shape memory polymers, the most widely studied thermo induced shape memory polymers are realized by direct heating. Its shape memory effect. Although there is a lot of research on this type of thermotropic shape memory polymer, it is still unable to fully explore the change of microstructure in the process of heat driven shape memory. In addition, the new type of driving mode, such as light, electricity and magnetism, can be remotely compared to the direct heating to realize shape memory effect. Therefore, it has become the focus of attention by using physical methods with the advantages of simple operation and short period of experiment to develop new response shape memory polymers and multi response shape memory polymers which can meet special needs. In this context, this paper uses melt blending and solution blending method. A blend / composite shape memory polymer was successfully prepared. The structural properties of the thermoinduced shape memory blends and the molecular mechanism in the shape memory process were studied. A new shape memory polymer with electric field, water and infrared response was obtained, and the mechanism of the response to shape memory polymers was described. First, in order to clarify the relationship between structural change and macro performance in the process of heat driven shape memory, a series of polyethylene vinyl acetate (Poly (ethylene-co-vinyl aetate), EVA) / polylactic acid (Poly (L-lactide), PLLA) blends and dynamic crosslinked EVA/PLLA blends were prepared by twin screw extrusion. The study showed that: 1) The shape memory properties of the EVA/PLLA blends affected the shape memory properties of the blends. Only when the blends were double continuous structures, the shape memory properties of the samples reached the best. In addition, there was a significant critical temperature (53 C) in the process of heating and recovery of the samples due to the effect of the glass transition of the EVA component on the blend samples. When the recovery temperature is below 53 C, PLLA inhibits the sample recovery; when the recovery temperature is higher than 53, the PLLA promotes the sample recovery; 2) for the dynamically crosslinked EVA/PLLA blends, the introduction of PLLA crystallization makes the blends in two fixed phase structures, one is the network structure of the chemical crosslinking in the EVA component, and the other is the PLLA crystallization as a physical crosslinking. The effect of physical crosslinking network and phase appearance on the shape memory properties of blends was explored by adjusting the size of PLLA crystallinity. The results showed that the crystallization of PLLA could improve the recovery rate of the blends, reduce the fixation rate, and the blends with high content of EVA showed the best shape memory properties. In the process of shape memory, the molecular chain structure, the crosslinking network and the crystalline structure have the effect on the shape memory in the shape memory process. Secondly, in order to obtain the three heavy shape memory polymer and the electroinduced shape memory polymer, the crosslinked EVA/ polyhexyl hexyl (Polycaprolactone, PCL) blends are prepared by the method of dense refining, and the quality of the blend is prepared and in the quality. EVA/PCL/CNT composites were further obtained by introducing carbon nanotube (Carbon nanotubes, CNTs) in the EVA/PCL blends with a ratio of 60/40. The study found that 1) the increase of the content of peroxide two isopropyl benzene (Dicumyl peroxide, DCP) significantly improved the degree of EVA chemical crosslinking for the crosslinked EVA/PCL blends, making the cross-linking network in the EVA component more effective. At the same time, the crosslinking reaction also improves the viscosity of the EVA component, making the blends tend to have a typical double continuous phase structure. The results show that the samples with typical double continuous phase structure and perfect chemical crosslinking network can be completely recovered from the temporary shape to the initial shape, and the effect of the three heavy shape memory is.2) in advance. The dispersion state of CNTs is estimated, and the selective dispersion of CNTs in the EVA/PCL/CNT composite is confirmed by direct observation. The percolation threshold of the composite material is further calculated to be 0.95 wt%.. When the conductive network of CNTs is perfect, the composite material can produce enough Joule heat under the applied electric field, resulting in the sample temperature. In order to obtain water induced shape memory polymers, the high elasticity of EVA and the hydrophilicity of polyvinyl alcohol (Polyving akohol, PVA) were used to prepare the EVA/PVA blends by means of solution blending. The results were found to be due to EVA and PVA. It is difficult to distinguish the corresponding components clearly from the phase appearance of the blends. Because the modulus of PVA is higher than that of EVA, the modulus of the blends will increase with the increase of PVA content. But because of the affinity and plasticization of the water molecules to the PVA component, the swelling and modulus of the blends will increase with the soaking time of the samples. The blends with high PVA content can show a good water induced shape memory effect based on the difference in the modulus of the blends at different water content. Finally, the graphene nanoscale (Graphene nanop) is introduced into the PU/ PCL blends of polyurethane (Polyurethane, PU) and the mass ratio of PCL to 50/50. Late, GNP), the shape memory PU/PCL/GNP composite with optoelectronic double drive was successfully prepared. The study shows that GNP can achieve good dispersion in the matrix prepared with PCL/GNP and does not affect the compatibility of PU/PCL. When the content of GNP is high, the crystalline structure of PCL will change, and GNP can also be found in the PU/PCL matrix. The percolation network structure is formed. The percolation threshold of GNP is 1.62wt% from the electrical performance test results. With the increase of GNP content, the GNP conductive percolation network in the composite is more perfect. Under the appropriate applied electric field, the composite will show a good shape memory effect. In addition, the properties of the photothermal conversion of GNP also make the composite material The material exhibits excellent photothermal conversion performance under light irradiation, which leads to a faster recovery rate than the blends under the same illumination conditions. Further using GNP's light and heat, the composite material with orientation structure can achieve complex shape change and self driving performance.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O631.11

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