發(fā)布時間：2018-06-22 15:48

  本文選題：共混復合材料 + 動態(tài)交聯(lián)反應��； 參考：《西南交通大學》2017年碩士論文

【摘要】：形狀記憶聚合物是一種具有大變形、刺激響應等特點的智能材料,在眾多領域中均有潛在的應用,如航空航天、生物醫(yī)療、電子器件等。目前,在形狀記憶聚合物領域中,人們研究最廣泛的熱致形狀記憶聚合物是通過直接加熱的方式來實現(xiàn)其形狀記憶效應。關于這種熱致形狀記憶聚合物的研究雖已有很多,但還不能全面地了解熱驅(qū)動形狀記憶過程中微觀結構的變化,仍需要深入探索。此外,相比于直接加熱來實現(xiàn)形狀記憶效應,光、電、磁等新型驅(qū)動方式有非接觸、可遠程控制等優(yōu)勢。因此,通過采用具有操作簡單、實驗周期短等優(yōu)點的物理方法來開發(fā)新型響應的形狀記憶聚合物,以及可滿足特殊需求的多響應型形狀記憶聚合物,成為了人們關注的熱點。在此背景下,本論文采用熔融共混法和溶液共混法成功制備了共混型/復合型的形狀記憶聚合物,深入研究了熱致形狀記憶共混物的結構性能關系及其形狀記憶過程中的分子機理,獲得了電場、水以及紅外光響應的新型形狀記憶聚合物,并闡述了相應響應形狀記憶聚合物的發(fā)生機制。首先,為了闡明熱驅(qū)動形狀記憶過程中的結構變化與宏觀性能之間的關系,采用雙螺桿擠出的方式制備了一系列的聚乙烯-醋酸乙烯酯(Poly(ethylene-co-vinyl aetate),EVA)/聚乳酸(Poly(L-lactide),PLLA)共混物和動態(tài)交聯(lián)EVA/PLLA共混物。研究表明:1)對于EVA/PLLA共混物,樣品相結構的變化明顯影響了其形狀記憶性能,只有在共混物為雙連續(xù)結構時,樣品的形狀記憶性能達到最佳。此外,由于EVA組分玻璃化轉(zhuǎn)變對共混物樣品的影響,在樣品升溫回復過程中存在一個明顯的臨界溫度(53℃)。當回復溫度低于53 ℃時,PLLA抑制樣品回復;當回復溫度高于53 ℃時,PLLA促進樣品回復;2)對于動態(tài)交聯(lián)EVA/PLLA共混物,PLLA結晶的引入使得共混物內(nèi)存在兩種固定相結構,一種是EVA組分中化學交聯(lián)的網(wǎng)絡結構,一種是PLLA結晶作為物理交聯(lián)點的網(wǎng)絡結構。通過調(diào)節(jié)PLLA結晶度的大小,探索了物理交聯(lián)網(wǎng)絡和相形貌對共混物形狀記憶性能的影響,結果發(fā)現(xiàn),PLLA的結晶能提高共混物的回復率,降低固定率,且具有高含量EVA的共混物表現(xiàn)出最優(yōu)的形狀記憶性能。進一步闡述了具有雙連續(xù)結構的共混物在形狀記憶過程中,其分子鏈結構、交聯(lián)網(wǎng)絡及結晶結構對形狀記憶的作用。其次,為了獲得三重形狀記憶聚合物和電致形狀記憶聚合物,采用密煉的方式制備了交聯(lián)EVA/聚己內(nèi)酯(Polycaprolactone,PCL)共混物,以及在質(zhì)量比為60/40的EVA/PCL共混物中引入碳納米管(Carbon nanotubes,CNTs)進一步獲得了EVA/PCL/CNT復合材料。研究發(fā)現(xiàn):1)對于交聯(lián)EVA/PCL共混物,過氧化二異丙苯(Dicumyl peroxide,DCP)含量的增加明顯改善了 EVA化學交聯(lián)的程度,使得EVA組分中的交聯(lián)網(wǎng)絡更加完善。同時交聯(lián)反應也提高了 EVA組分的粘度,使得共混物趨于呈現(xiàn)典型的雙連續(xù)相結構。結果表明,具有典型的雙連續(xù)相結構和完善化學交聯(lián)網(wǎng)絡的樣品能夠從臨時形狀完全回復到初始形狀,表現(xiàn)出三重形狀記憶的效果。2)預先理論估計了 CNTs的分散狀態(tài),并通過直接觀察確認了在EVA/PCL/CNT復合材料中CNTs選擇性分散于EVA組分。進一步計算獲得復合材料的逾滲閾值為0.95 wt%。當CNTs的導電網(wǎng)絡比較完善時,復合材料在外加電場下能夠產(chǎn)生足夠的焦耳熱,導致樣品溫度升高到其轉(zhuǎn)變溫度,使得復合材料表現(xiàn)出優(yōu)秀的電致形狀記憶效應。再者,為了獲得水致形狀記憶聚合物,利用了 EVA的高彈性和聚乙烯醇(Polyving akohol,PVA)的親水性,通過采用溶液共混的方式制備了 EVA/PVA共混物。結果發(fā)現(xiàn)由于EVA和PVA之間的相互作用,進而難以從共混物的相形貌中清晰地分辨出相應的組分;由于PVA的模量比EVA的高,共混物的模量會隨著PVA含量的增加而增加。但又因水分子對PVA組分的親和性及增塑作用,共混物的溶脹度和模量會隨著樣品浸水時間的增加而有明顯的下降。正是基于共混物在不同含水程度下模量的差異,使得具有較高PVA含量的共混物能夠表現(xiàn)出很好的水致形狀記憶效應。最后,通過向聚氨酯(Polyurethane,PU)和PCL質(zhì)量比為50/50的PU/PCL共混物中引入石墨烯納米片(Graphene nanoplate,GNP),成功制備了具有光電雙驅(qū)的形狀記憶PU/PCL/GNP復合材料。研究表明,在以PCL/GNP為母料制備的復合材料中GNP能夠?qū)崿F(xiàn)良好的分散且不影響PU/PCL的相容性;當GNP的含量比較高時,PCL的結晶結構會發(fā)生變化,同時GNP也能夠在PU/PCL基體中形成逾滲網(wǎng)絡結構。從電學性能測試結果可知GNP的逾滲閾值為1.62wt%,隨著GNP含量的增加,復合材料中GNP導電逾滲網(wǎng)絡越加完善,在適當外加電場作用下,復合材料會表現(xiàn)出很好的電致形狀記憶效應。此外,GNP的光熱轉(zhuǎn)換特性也使得復合材料在光照射下表現(xiàn)出優(yōu)良的光熱轉(zhuǎn)換性能進而導致在相同的光照條件下,復合材料比共混物具有更快的回復速度。進一步利用GNP的光熱,具有取向結構的復合材料能夠?qū)崿F(xiàn)復雜形狀變化和自驅(qū)動性能。
[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.
【學位授予單位】：西南交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O631.11

【參考文獻】

相關期刊論文 前1條

1 張新民;;智能材料研究進展[J];玻璃鋼/復合材料;2013年Z2期

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本文編號：2053328