【作者】 郝艳萍；

【导师】 张清华；

【作者基本信息】 东华大学 ， 材料科学与工程， 2017， 博士

【摘要】 自2004年单层石墨烯被发现以来,因其具有独特的二维结构和优异性能成为化学、物理等领域的研究热点。石墨烯及石墨烯/聚合物纳米材料具有奇异的结构和性能,展现出重大的科学意义和应用价值,但真正实现石墨烯及其复合材料的产业化应用,还面临着许多问题和挑战。本论文通过化学方法功能化氧化石墨烯,并分别以聚丙烯(PP)和聚酰亚胺(PI)为基体制备复合材料,研究功能化后氧化石墨烯在这些聚合物中的分散性,讨论氧化石墨烯的加入对材料形态结构、力学性能、结晶特性、热稳定性等行为的影响,为氧化石墨烯/聚合物复合材料的规模化制备和应用积累相关数据和资料。主要研究内容如下:(1)氧化石墨烯的表面改性。针对石墨烯在聚合物基体中不易分散的问题,通过十八烷基异氰酸酯对氧化石墨烯(GO)进行功能化改性,成功制备了烷基化改性氧化石墨烯(iGO)。采用FT-IR、Raman、TEM、TGA、元素分析等测试方法对iGO进行了表征测试。结果证明,烷基链被成功地通过共价键接到了GO的片层表面上,且石墨烯片层中每4个碳接有一个烷基链;与GO相比,iGO在有机溶剂中有更好的分散性。(2)氧化石墨烯/PP复合材料的制备及其性能。以具有结晶特性的聚丙烯为基体,采用溶液共混的方法分别制备了GO/PP和iGO/PP复合材料,研究了复合材料的动态力学性能、热稳定性、物理机械性能和结晶行为等。结果表明,GO/PP复合材料的玻璃化转变温度(Tg)比纯PP略微向高温方向迁移,而iGO/PP复合材料的玻璃化转变温度为16.3℃,向低温方向移动了2℃。与PP相比,GO/PP和iGO/PP复合材料的热稳定性比纯PP有较大提升,失重率为5%时GO/PP对应的热分解温度比PP高27℃,iGO/PP比PP高42℃。与纯PP相比,iGO/PP复合材料拉伸强度略有下降,但杨氏模量却提升了42%左右。XRD测试表明,所制备的GO/PP和iGO/PP复合膜的晶体形态均以α球晶为主。在此基础上,进一步对GO/PP及iGO/PP进行结晶动力学研究。GO和iGO在PP等温结晶过程中均起了异相成核剂的作用,加快了PP的结晶速率。Avrami方程可以用来分析GO/PP及iGO/PP的等温结晶过程,GO及iGO的加入降低了PP的等温结晶活化能。Ozawa模型和Mo模型均可以很好地描述GO/PP及iGO/PP复合材料的非等温结晶过程。(3)氧化石墨烯/PP/PS聚合物共混物的制备及其性能。为研究氧化石墨烯对聚合物共混物的界面及性能的影响,以PP/PS共混物为制备聚合物共混物材料的基体,通过熔融共混方法制备了氧化石墨烯/PP/PS聚合物共混物,重点分析了iGO/PP/PS共混物的相形态的变化,并讨论加工过程(共混次序)对聚合物共混物在相结构和性能上的影响。研究表明GO对PP/PS共混物增容作用不明显,而iGO可以明显促进PP/PS共混物的两相间的相容性。iGO较少的填充量对PP/PS共混物的相结构有增容作用,iGO含量较大时因iGO的团聚使PP/PS共混物相容性变差。DMA分析发现,石墨烯的加入使PP和PS的Tg均明显向高温方向迁移,且iGO比GO的影响更加明显;同样,GO和iGO均使PP/PS共混物中的PP的结晶速率变快,结晶度变小,而iGO的作用更明显。GO对PP/PS共混物力学性能的提升作用有限,而iGO却明显提升PP/PS共混物力学性能,在iGO的添加量为0.2wt%时拉伸强度比PP/PS共混物增加35%。GO和iGO都可以提高PP/PS共混物的热稳定性,在失重为10%时iGO/PP/PS共混物的热分解温度比PP/PS复合材料提升了近30℃,比GO/PP/PS复合材料提升了25℃。加工过程中iGO与PP及PS先后共混次序的不同对PP/PS共混物力学性能有很大的影响。在各组份同时加入共混熔融制备的iGO/PP/PS共混物样品中,iGO主要集中于相界面及相邻区域,在相界面间形成“过渡区”,对共混物增容效果明显,相应力学性能提升;iGO先与PS熔融共混再加PP制备的(PS/iGO)/PP共混物中,iGO主要集中于PS相和相界面相邻区域,也可在相界面间形成“过渡区”,促进PP相与PS相的容合,力学性能也有所提升;但添加次序为先PP和iGO共混,再加入PS制备的(PP/iGO)/PS共混物,iGO主要集中于PP相内,材料出现相分离的趋势,相应力学性能下降。(4)氧化石墨烯/聚酰亚胺复合材料及其性能。通过溶液共混方法,制备成功了氧化石墨烯/聚酰亚胺复合膜和功能化氧化石墨烯/聚酰亚胺复合膜,并成功纺丝制备了功能化氧化石墨烯/聚酰亚胺复合纤维。研究发现,iGO对聚酰胺酸(PAA)环化为聚酰亚胺(PI)的过程有诱导作用。相比GO,iGO与PI基体界面相互作用较好,随着iGO含量的增加,iGO/PI复合膜界面相互作用先变好后变差,在添加量为3wt%时相对最好。在添加量同为1wt%的情况下,GO/PI复合材料的玻璃化转变温度略微高于PI,而iGO/PI复合材料的玻璃化转变温度则明显低于PI。力学性能方面,在iGO的添加量为1 wt%时,iGO/PI复合膜的拉伸强度比纯PI增加了80%;在iGO添加量为0.5 wt%时iGO/PI复合纤维与纯PI纤维相比,拉伸强度增加了93%,模量也提升了192%。更多还原

【Abstract】 Since the graphene was found in 2004,the nano material has become a research hotspot in chemistry,physics and other fields,due to its unique two-dimensional structure and excellent performance.The graphene and graphene/polymer nano-materials show great scientific significance and application value in both theory and experimental research.However,in order to realize the industrialization application of graphene and the composite,there exist still a lot of problems and challenges.In this paper,the graphene oxides/polymer composite materials with excellent mechanical and thermal properties were prepared and the relationship between the interfacial morphology and properties of graphene oxides/polymer composite materials were discused.The main research contents are following:(1)Functionalization of graphene oxides.In order to overcome the dispersion of the graphene in the polymer matrix,the isocyanate-treated graphene oxides(iGO)has been successfully fabricated by grafting octadecyl isocyanate onto the suface of the graphene oxides(GO)with isocyanicacid octadecyl ester.The iGO was characterized by FT-IR,Raman,TEM,TGA,element analysis.The results show that 18 carbon atoms in the alkyl chain are successfully covalently bonded to the surface of the GO,and one alkyl chain unit is incorporated for every 4 graphene carbons.Compared with the GO,the iGO shows the better dispersion in organic solvents.(2)Preparation and properties of graphene oxides / polypropylene nanocomposites.The graphene oxide/polypropylene(GO/PP)and the functional graphene oxide /polypropylene(iGO/PP)composite materials were prepared by solution blending method.The structure,the dynamic mechanical properties,thermal stability,tensile mechanical properties and the crystallization behavior of the composite materials were analyzed and discussed.As a result,compared with PP,the glass transition temperature of GO/PP increases slightly and iGO/PP composite materials decreases by 2 ℃.The thermal stability property of these composites also increases.The thermal decomposition of 5 % weight temperature of the GO/PP and the iGO/PP are 27 ℃ and 42 ℃ higher than that of PP,respectively.Based on XRD data,the crystal morphology of GO/PP and iGO/PP composites are dominated by the a spherulite.The crystallization kinetics of iGO/PP and GO/PP is investigated by means of several methods.The isothermal crystallization kinetics of iGO/PP and GO/PP composite are analyzed by Avrami model based on the differential scanning calorimetry data.The results show that the well dispersed graphene nanosheets acts as a heterogeneous nucleating agent and decreases the activation energies,leading to an acceleration of crystallization during the PP isothermal crystallization process.The non-isothermal crystallizing data are analyzed with the Ozawa and Mo et al.models,and it is demonstrated that both two models are successful to describe the non-isothermal crystallization process for GO/PP and iGO/PP composite.(3)Preparation and properties of graphene oxides / PP / PS blends.The graphene oxides/PP/PS blends materials were prepared by melt blending method.The impact of the phase morphology and related properties of PP/PS blends materials with the modified graphene oxides were analyzed,and the effect of processing order on the phase structures and properties of the polymer blends were discussed.As a result,the compatibilization of GO for PP/PS blends materials is not obvious,but iGO can significantly promote the compatibility between two phases of the PP/PS blends.The aggeragation of iGO results in the poor compatibility of PP/PS blends with a high content of iGO.GO has a little effect on dynamic mechanical properties of PP/PS blends,while iGO performs more impact,which induces the Tg of PP and PS,were significantly migrate to the higher temperatures.Both of GO and iGO can increase crystallization rate of PP in PP/PS blends,leading to the low crystallinity,and the influence of iGO is more obvious.The enhancement of GO in the mechanical properties of PP/PS blends is limited,and iGO enhances the tensile mechanical properties of PP/PS blends.The tensile strength increases by 35 % compared with PP/PS blends with a loading of 0.2 wt% GO.What’s more,GO and iGO can promote to improve the thermal stability of the PP/PS blends,in which iGO exhibits a greater performance.When weightlessness is 10 %,the decomposition temperature of iGO/PP/PS blends improved nearly 30 ℃ than PP/PS composites and GO/PP/PS composites 25 ℃,respectively.In addition,the blending order of iGO,PP and PS has a great influence on interface structure,phase morphology and related performance of PP/PS blends in the fabrication process.When melt-blend all the ingredients to prepare iGO/ PP/PS blends at the same time,the iGO concentrates on the phase interface and adjacent areas,and form a "transition zone" in the phase interface to improve the compatibilization effect and enhance the corresponding mechanical properties.When firstly melt iGO with PS following with mixing of PP,the iGO concentrates on the PS phase and the phase interface adjacent areas in the prepared(PS/iGO)/PP blends.And,a "transition zone" between the phase interface forms to facilitate the improved compatibilization effect between PP and PS phases and mechanical properties has been raised.However,when firstly melt iGO with PP following with mixing of PS,the iGO exists mainly in the PP phase of the prepared(PP/iGO)/PS blends,which induce the phase separation and the decrease of corresponding mechanical properties.(4)Preparation and properties of graphene oxides / polyimide composites.We have successfully prepared graphene oxides/polyimide composite films,functionalized graphene oxides/polyimide composite films and functionalized graphene oxides/polyimide composite fibers.As a result,functionalized graphene oxides provides a induced action for cyclizing the polyamic acid(PAA)to polyimide(PI).The interface between PI and iGO is much better than the GO/PI.Dynamic mechanical analysis exhibits that the glass transition temperature(Tg)of GO/PI composite is slightly higher than that of the PI,while the Tg of the iGO/PI composite is significantly lower than that of the PI at the loading of 1 wt% iGO.The iGO effectively improves the mechanical properties of the PI compared with GO.The tensile strength of iGO/PP composite films with a laoding of 1 wt% iGO increases by 80% than that of PI films,while the tensile strength of iGO/PP composite fibers increases by 93 % and tensile modulus increases by 192 % compared with PI fibers with a laoding of 0.5 wt% iGO.更多还原