【作者】 吴新锋；

【导师】 江平开；

【作者基本信息】 上海交通大学 ， 材料学， 2013， 博士

【摘要】 超高分子量聚乙烯（UHMWPE或UPE）以其优越的物理机械性能如抗冲击性、耐磨损性、自润滑性、无毒性和耐低温性等性能而应用于医疗、采矿业、油气资源开发、纺织、化工及体育运动器械等领域，特别是在人工关节和耐磨管道方面的应用。但是在使用过程中，一方面因为UPE本身是线性结构，另外一个方面因为导热系数低，磨擦生热使材料温度升高，UPE仍然容易发生蠕变和强度疲劳而影响材料的磨擦等性能。因此本论文从两个大的方面对UPE进行改性:（1）通过添加辐照敏化剂进行辐照交联的方法使UPE形成交联网络，改变UPE的线性结构，使UPE不易产生塑性变形等蠕变现象。（2）提高UPE的导热系数，把因磨擦生热而产生的热量导出，从而降低因温度升高而导致的蠕变，导热部分主要研究包括：UPE本征导热；比较内容中包括添加Al₂O₃制备UPE/Al₂O₃、LLDPE/Al₂O₃和Epoxy/Al₂O₃复合材料；添加碳材料（石墨NG、碳纤维CF和石墨烯GS）制备UPE/NG、UPE/CF和UPE/GS复合材料。具体研究内容及结论如下:1. UPE、TMPTMA/UPE和TPGDA/UPE复合材料通过引入交联助剂TMPTMA和TPGDA到UPE中，后经电子束辐照交联，可保证在降低辐照剂量的同时提高UPE材料的交联程度。通过FTIR和溶胀平衡测试、DSC、电子拉力机、磨擦试验机、SEM对辐照前后的材料的结构、凝胶含量、交联点间分子量、结晶度、力学性能、磨擦性能、磨擦形貌进行了表征和研究。主要结论如下：（a） FTIR和凝胶含量测试结果表明复合材料中均发生了交联反应，TPGDA/UPE和TMPTMA/UPE的凝胶含量均高于纯UPE的凝胶含量，TMPTMA和TPGDA的加入有利于在降低辐照剂量的同时提高UPE的交联程度。（b）辐照后材料的结晶度均有所增加，而且TMPTMA/UPE和TPGDA/UPE的结晶度高于UPE的结晶度，说明TMPTMA和TPGDA这两种交联助剂小分子的加入有利于UPE结晶。（c） UPE材料结晶度的提高和交联度的提高有利于UPE磨擦性能的提高，如1%TMPTMA/UPE（100kGy）和1%TPGDA/UPE（100kGy）的磨损率分别为1.89×10-7mm3/（N m）和4.28×10-7mm3/（N m）,分别为UPE（100kGy）磨损率（4.28×10-7mm3/（N m））的44.2%和100%。表明TMPTMA对于降低UPE的磨损率是有效的，而TPGDA因为增塑作用却几乎没有作用。SEMs的结果也表明1%TMPTMA/UPE（100kGy）的表面最光滑，溶胀平衡实验结果也表明1%TMPTMA/UPE（100kGy）的交联点间分子量（Mc=3141g/mol）低于UPE（100kGy）的交联点间分子量（Mc＝5055g/mol）。2. UPE本征导热通过控制降温程序的方法提高UPE材料的本征导热性能。通过DSC法研究了UPE材料的熔融重结晶过程，主要结论如下：（a）降温速率、保温温度和保温时间均会影响材料的结晶，降温速率越慢，在125℃保温，且保温时间越长越有利于UPE材料结晶度的提高和结晶的规整性。（b）通过DSC法研究发现随机冷却最有利于UPE材料结晶度的提高和熔点的提高，也有利于材料密度的增加和导热系数的提高，拉伸强度有所提高。随机冷却的UPE的导热系数为0.593W/（m K）比10min水压冷的UPE材料的导热系数0.503W/（m K）高17.9%。（c） UPE导热系数的提高是由于UPE中的一个一个球晶连成的晶桥来实现的，即导热提高的机理为结晶晶桥导热机理，随机冷却的方式相当于拓宽了晶桥的宽度，从而有利于导热声子的传递，导热系数提高。3. UPE/Al₂O₃、LLDPE/Al₂O₃和Epoxy/Al₂O₃复合材料对比性研究通过在乙醇熔液共混热压法（UPE和Al₂O₃的粉末混合、包覆、热压法）制备了UPE/Al₂O₃复合材料，并对UPE/Al₂O₃复合材料进行了退火热处理，哈克密炼法制备了LLDPE/Al₂O₃复合材料，真空浇注法制备了Epoxy/Al₂O₃复合材料，研究高结晶材料和低结晶材料、结晶材料和非晶材料、热处理对材料导热性能的影响。通过SEM、TGA、DSC、导热仪、介电谱仪和高阻计对形成的复合材料的分散性、热性能、结晶情况或玻璃化转变温度、导热系数、介电性能和电阻率。主要结论如下：（a）本征导热高的基体，形成的复合材料的导热系数也高。DSC测试表明树脂基体结晶度大小次序为LLDPE<UPE<UPE （热处理），复合材料的导热系数次序为LLDPE/Al₂O₃<UPE/Al₂O₃<UPE/Al₂O₃（热处理）。（b）热处理可以提高结晶复合材料的结晶度和结晶规整性，同时可以提高材料的导热系数。热处理后的UPE/Al₂O₃（100phr）的熔融热比热处理前分别提高了18.5%，熔点提高了3.8℃，导热系数可以提高到了1.960W/（m K），比处理前的导热系数1.554W/（m K）高出约35.4%。（c）无定形聚合物Epoxy的导热系数小于结晶聚合物PE的导热系数，添加相同份数的Al₂O₃填料后导热系数增加的倍数也小。UPE/Al₂O₃（12.0vol%）、LLDPE/Al₂O₃（12.0vol%）和Epoxy/Al₂O₃（13.8vol%）三种复合材料的导热系数分别为1.160W/（m K）、0.909W/（m K）和0.425W/（m K），分别比各自树脂基体的导热系数提高了132.0%、102.4%和72.8%。（d）添加Al₂O₃后，复合材料的热稳定性能都有所提高。UPE/Al₂O₃（100phr）、LLDPE/Al2O（3100phr）和Epoxy/Al₂O₃（100phr）的5%热失重温度为467℃、461℃和366℃，分别比纯基体提高了11.5℃、13℃和34℃。三种复合材料均获得了较好介电性能和电性能。4. UPE/NG、UPE/CF和UPE/GS复合材料用改性的Hummers法制备了氧化石墨烯，氧化石墨烯在水-乙醇溶液的混合液中和UPE混合，水合肼还原，然后再通过热压的方法制备了UPE/GS复合材料。通过在乙醇溶液混合和热压成型的方法制备了UPE/NG、UPE/CF复合材料。研究三种高导热高导电碳材料对于UPE材料导热导电性能的影响。主要结论如下：（a）利用FT-IR、XRD等手段对石墨烯进行了结构表征；利用AFM和TEM对石墨烯形貌进行了表征；用TGA方法研究了其热稳定性，结果表明制备了石墨烯材料。（b）复合材料越致密、导热晶体结构越规整越有利于导热通路的形成。复合材料的导热性能次序为：UPE/NG>UPE/CF>UPE/GS，这与复合材料的结构有关，UPE/NG的结构规整，材料密度随着填料的增加而逐渐增加；UPE/CF复合材料的结构整体上规整，但还是有有一定的团聚现象，但宏观上的TGA测试还是比较均匀的，材料的密度变化不大；UPE/GS复合材料的密度随着GS的增加反而是下降的，GS的加入引入了很多空隙。UPE/NG（60phrNG）、UPE/CF（60phr CF）和UPE/GS（10phr GS）的导热系数为分别为3.257W/（m K）、0.778W/（m K）和0.52W/（m K），分别比UPE的导热系数提高了556.7%、56.9%和4.8%。（c）填料为10phr时，复合材料的导电次序为UPE/CF>UPE/GS>UPE/NG。电导率次序和导热性能次序不一样，导电机理为电子导电，电子可以很容易地跨越界面壁垒，受界面影响不大；而导热机理为逾渗理论，且导热主要以声子导热为主，导热声子很难跨越界面壁垒，受界面影响较大。所以说并不能把导热机理等同于导电机理。更多还原

【Abstract】 Ultra High Molecular Weight Polyethylene （UPE） with its excellent mechanical propertiessuch as high impact resistance, wear resistance, self-lubrication, non-toxic and low temperatureresistance and other properties has been used in the fields of medical, mining, oil and gasexploitation, textile chemical and sports equipment, especially in the application of artificial jointsand wear-resistant pipe. However, the liner structure of UPE and frictional heat during the usemake UPE creep weak and the strength fatigue, and then affect the wear property of UPE. So UPEis modified from two aspects:（1） the irradiation sensitizer is added into UPE to form a crosslinkednetwork to change the linear structure of UPE to make UPE difficult to produce plasticdeformation and creep.（2） Improving the thermal conductivity of UPE is used to export frictionalheat to reduce creep caused by elevated temperature. The method consists of three parts: theimprovement of UPE intrinsic thermal conductivity, Preparation of UPE/Al₂O₃, LLDPE/Al₂O₃andEpoxy/Al₂O₃composites; Preparation of UPE/NG, LLDPE/CF and Epoxy/GS composites. Thedetail contents and conclusions are as follows:1UPE/Al₂O₃, LLDPE/Al₂O₃and Epoxy/Al₂O₃compositesTMPTMA and TPGDA are dispersed on the UPE powders by the solution method. UPE,TMPTMA/UPE和TPGDA/UPE composites were made by compression-molded and thencrosslinked by EB. The method above can reduce the irradiation dose at the same time to increasethe crosslinking degree of UPE. FTIR, Swelling balance test, DSC, Electronic tensile testingmachine, friction tester, SEM are used to test the structure changes before and after irradiation, thegel content, crosslinking point between molecular weight, degree of crystallinity, mechanicalproperties, friction properties, friction morphology. The main conclusions are as follows:（a） FTIR and gel content show that the crosslink reaction happens in the composite,. The gelcontent of TMPTMA/UPE和TPGDA/UPE composites are all higher than that of UPE. The addingof TMPTMA and TPGDA can reduce the irradiation dose at the same time to increase thecrosslinking degree of UPE. （b） The degree of crystallinity of all specimens increases after irradiation. The degree ofcrystallinity of TMPTMA/UPE和TPGDA/UPE composites are all higher than that of that of UPE,showing that the adding of TMPTMA and TPGDA are useful to increasing the degree ofcrystallinity.（c） The increasing of the degree of crystallinity and the degree of crosslinking are useful toincreasing the wear resistance of UPE. The wear rate of1%TMPTMA/UPE（100kGy） and1%TPGDA/UPE（100kGy） is1.89×10-7mm3/（N m） and4.28×10-7mm3/（N m）,respectively, about44.2%and100%of the wear rate of UPE（4.28×10-7mm3/（N m））.2UPE intrinsic thermal conductivityThe intrinsic thermal conductivity of the material of the UPE is improved by controlling thecooling process. The melting and recrystallization process of UPE is studied by DSC method.Themain conclusions are as follows:（a） Cooling rate, holding temperature and holding time will affect the degree of crystallinityof UPE. The slower the cooling rate, the holding temperature at125℃and the longer theholding time are useful to improve the degree of crystallinity and crystallization tacticity of UPE.（b） Stochastic cooling is most useful to increase the degree of crystallinity and melting pointof UPE by the DSC method, and also helpful to improve the tensile strength of UPE. Thermalconductivity of UPE （Stochastic cooling） is0.593W/（m K）,17.9%higher than thermalconductivity of UPE（press with water for10min）（0.503W/（m K））.（c） The improvement of thermal conductivity of UPE is due to the connection of the crystalbridge formed by UPE spherulites. The heat conduction mechanism of UPE is the crystal bridgeconduction mechanism. Stochastic cooling manner is equivalent to widening the width of thecrystal bridge, thereby useful to the transmission of the thermal conductivity phonons, so thethermal conductivity is improved.3UPE/Al₂O₃, LLDPE/Al₂O₃and Epoxy/Al₂O₃compositesUPE/Al₂O₃composite is prepared by powder mixing in ethanol and compression-moldedmethods. Then UPE/Al₂O₃composite is thermal treated at200℃. LLDPE/Al₂O₃composite ismade by Huck mixing method. Epoxy/Al₂O₃composite is made by vacuum casting method.Thermal Conductivity between Highly crystalline materials and low-crystalline materials,crystalline materials and amorphous materials, thermal treatment and un-thermal treatment are studied. The dispersion, thermal properties, crystalline or glass transition temperature, thermalconductivity, dielectric properties and resistivity of UPE/Al₂O₃, LLDPE/Al₂O₃and Epoxy/Al₂O₃composites are measured by SEM, TGA, DSC, thermal analyzer, dielectric spectroscopy and highresistance meter. The main conclusions are as follows:（a） If intrinsic thermal conductivity of the polymer matrix is high, thermal conductivity of theforming composite is also high. The degree of crystallization order is LLDPE <UPE <UPE（thermal treatment）, thermal conductivity order of the composites is: LLDPE/Al₂O₃<UPE/Al₂O₃<UPE/Al₂O₃（thermal treatment）.（b） Thermal treatment can increase the degree of crystallinity and the crystalline regularity ofthe crystalline of the composite, at the same time can improve the thermal conductivity of thematerial. After thermal treatment, the heat of fusion and the melting point are18.5%,3.8℃higher than that of UPE/Al₂O₃（100phr） composite before thermal treatment, respectively. Thermalconductivity of UPE/Al₂O₃（100phr） after thermal treatment is1.960W/（m K）,35.4%higherthan that of UPE/Al₂O₃（100phr） before thermal treatment （1.554W/（m K））.（c） Thermal conductivity of Epoxy（Amorphous polymer） is lower than thermal conductivityof PE（crystalline polymer）. After adding the same content of Al₂O₃filler, thermal conductivityincreasing proportion of Epoxy composite is also lower than that of PE composite. Thermalconductivity of UPE/Al₂O₃（12.0vol%）、LLDPE/Al₂O₃（12.0vol%） and Epoxy/Al₂O₃（13.8vol%）are1.160W/（m K）,0.909W/（m K） and0.425W/（m K），respectively,132.0%，102.4%and72.8%higher than that of each of the resin matrix.（e） Thermal stability of the composite after adding Al₂O₃filler,5%weight loss temperatureof UPE/Al₂O₃, LLDPE/Al₂O₃and Epoxy/Al₂O₃are467℃,461℃and366℃, respectively,11.5℃13℃and34℃，higher than the pure matrix. Three composites all have good dielectricproperties and electrical properties.4UPE/NG, UPE/CF and UPE/GS compositesGraphene oxide（GO） is prepared by modified Hummers method. GO is mixed with UPE inwater-ethanol solution, then GO is reduced by hydrazine hydrate. At last, UPE/GS is prepared bythe hot press method. UPE/NG and UPE/CF composites are prepared by powder mixing in ethanoland compression-molded methods. Influences of the three kinds of carbon materials on electricconductivity and thermal conductivity performances of UPE composites. The main conclusions are as follows:（a） FT-IR and XRD is used to characterize the structure of graphene. AFM and TEM are usedto characterize the graphene morphology. TGA is used to study the thermal stability of graphene.The results above show that the graphene is prepared.（b） If the composite is more dense and the crystal structure of the filler is more regular, thethermal conductive path will be easy to formed. Thermal conductivity of the composite order isUPE/NG>UPE/CF>UPE/GS, which is related to the structure of the composites. UPE/NGcomposite has regular structure and the density gradually increases with the increasing filler.UPE/CF composite is regular on the overall structure of the material, but still has a certainagglomeration, and the density has little change. The density of UPE/GS material decreases withthe increasing GS, GS join introduces a lot of gaps. Thermal conductivities of UPE/NG（60phrNG）、UPE/CF（60phr CF）and UPE/GS（10phr GS）composites are3.257W/（m K）、0.778W/（m*K） and0.52W/（m K）, respectively,556.7%,56.9%and4.8%higher than that of UPE matrix.（c） When the filler content is10phr, electric conductivity order of the three composites isUPE/CF>UPE/GS>UPE/NG. The electric conductivity order is not same as thermal conductivityorder, showing that the electric conductivity mechanism is not same as the thermal conductivitymechanism. Electric conductivity mechanism is mainly affected by the electronic conductivity, notaffected by the interface so large. Thermal conductivity mechanism is percolation theory andthermal is mainly transmitted by phonon combined with some electronic thermal conductivity.Thermal conductivity is also influenced by the interface and the interface effect is very big. Soelectric conductivity mechanism cannot simply be transformed to thermal conductivity mechanism.The two mechanism are not the same thing.更多还原