【作者】 张小伟；

【导师】 余永富； 朱瀛波；

【作者基本信息】 武汉理工大学 ， 矿物加工工程， 2011， 博士

【摘要】 云母作为绝缘材料用于各种电气、电机工业中,具有优良的性能。随着大片优质云母资源的枯竭,利用碎云母制备的云母纸因其厚度均匀、介电强度波动小、电晕起始电压高而稳定成为云母绝缘材料的主力军。云母纸是将破碎后的细小鳞片在造纸机上抄造成大面积的纸张,它的成形主要靠鳞片间的静电引力和范德华力。然而,这两种力较小,抄造的云母纸强度低不能直接应用,需要预先补强,通常的方法是在粘结剂的作用下将云母纸和补强材料粘合在一起形成云母纸材料。然而,这种补强工艺需要大量的粘结剂,极大的降低了材料中云母的含量,影响材料的绝缘性能、使用寿命等。为了保持云母材料的绝缘性能,并提高材料的机械强度,新的补强材料和补强工艺是云母纸材料发展的方向。芳纶纤维具有极高的强度,且具有优良的绝缘性能,芳纶纤维与云母鳞片通过合适的工艺复合提高云母纸材料的强度是新兴研究的热点。本文添加8%含量的芳纶纤维与云母鳞片复合制备芳纶云母纸复合材料,选择合适的云母原料、制浆方式获得云母浆料后,通过云母鳞片的表面改性和芳纶纤维的分散、改性,提高芳纶纤维与云母鳞片的界面结合强度、均匀度等。在添加8%含量的芳纶纤维的情况下制备的芳纶云母纸复合材料的性能基本达到了国外添加50%芳纶纤维抄造的复合云母纸的水平,极大的提高了纸张的强度,省去了以往云母纸材料需要浸胶、补强的工艺,可直接使用,简化了工艺流程。通过大量的试验研究,获得了各项工艺参数的最佳条件,主要得到以下结果：1.选定了云母原料后,通过对比水力制浆法和煅烧化学制浆法制备的云母浆料抄造的云母纸和芳纶云母纸的性能,可知煅烧化学制浆法制备的云母浆料更利于提高纸张的介电强度和拉伸强度；通过正交试验获得了煅烧化学制浆工艺的最佳条件。进行了云母浆料粒度组成对芳纶云母纸复合材料性能的影响研究,并通过正交试验获得了最佳的云母鳞片粒度组成用于芳纶云母纸的制备。2.尽量减少生产用水中杂质金属离子、悬浮物,避免碱性水质是提高芳纶云母纸强度性能的前提；净化水质后,可选用不同的改性剂对云母鳞片进行表面改性提高云母鳞片的表面性质；通过对比几类不同的改性剂可知,聚丙烯酰胺类改性剂和淀粉类改性剂对云母鳞片的改性效果明显。其中淀粉类改性剂较好,以阳离子淀粉改性剂为最佳；当阳离子淀粉改性剂的用量为10kg/t,改性云母浆料浓度为16%,改性时间30min改性后的云母鳞片抄造的芳纶云母纸比未经改性云母鳞片抄造的芳纶云母纸的拉伸强度提高了277.5%,改性效果十分明显,且改性剂的添加不影响材料的介电性能；3.通过不同的改性方式对芳纶纤维进行表面改性研究,发现超声波改性对提高芳纶纤维的表面活性,促使纤维表面微纤维、帚化较有利；同时,辅以硅烷偶联剂改性,可有效的提高芳纶纤维的表面力,提高材料的强度。经过600W的超声波改性5min,再辅以30kg/t的硅烷偶联剂改性5h后的芳纶纤维与云母鳞片混合抄造的芳纶云母纸的拉伸强度由23.97N/cm提高至28.56N/cm,提高了19.1%,改性效果明显。聚氧化乙烯和十二烷基苯磺酸钠同时使用作为芳纶纤维的分散剂,可实现芳纶纤维的均匀分散,提高抄造的芳纶云母纸的均匀度。4.通过对比三种不同的抄造成形工艺,最终确定了最适合芳纶云母纸抄造的工艺：混浆抄造工艺,其工艺流程简单,操作方便,芳纶纤维的补强效果好,极大的提高了云母纸材料的强度。5.进行了芳纶云母纸的热压操作,获得了最佳的热压工艺参数,即在平板硫化机上以240℃的温度,22MPa的压力下热压1h。经过热压后,芳纶云母纸的拉伸强度可达33.65N/cm,介电强度33.84KV/mm、耐折度1.74,材料的密实度、柔软性能增强。并对比了自制芳纶云母纸与NOMEX418纸的各项性能,包括机械性能、耐温性能、绝缘性能和使用稳定性,自制芳纶云母纸的拉伸强度、介电强度较高,耐温性能和稳定性与NOMEX418类似,体积电阻率和介质损耗有待进一步提高。课题研究中,芳纶云母纸均在实验室条件下制得,工业化生产时纸张的性能会进一步提升。6.探讨了芳纶云母纸复合增强的机理：云母鳞片的级配提高了材料的密实度,减少了材料内部的裂隙,降低了材料从裂隙处破坏的几率；改性剂在云母鳞片表面的物理吸附和化学键和提高了云母鳞片的表面力,超声波空化作用和偶联剂的偶联作用提高了芳纶纤维的表面活性,有效的改善了材料的界面结合性能,增加了材料的塑性,提高了材料的整体性能。芳纶云母纸复合材料的研制具有重要的意义。首先,本课题芳纶云母纸的制备可填补国内无相关产品的空白,打破对国外产品的依赖。其次,芳纶纤维的补强云母纸基材料可以达到很高的强度,制备的芳纶云母纸可直接使用,无需再添加补强材料,提高了材料中云母的含量,有利延长云母纸材料的使用寿命,提高电气设备的安全性。通过合适的工艺流程,可一次成形,省去了传统工艺的浸胶、补强工艺,简化了工艺流程。再次,芳纶纤维的使用,有利于减薄了纸基绝缘的厚度,对电气设备的小型化有重要的意义。最后,添加少量的芳纶纤维极大的降低了芳纶云母纸生产的成本,增加了产品的经济效益。更多还原

【Abstract】 As insulation material mica is used in kinds of electrical and motor industry, showing superior performance. With the exhausting of large mica resource, mica papers made of mica flakes become main mica insulations because of its uniform width, small ripple dielectric strength and high initial voltage of corona. Mica papers are made from mica flakes using paper making machine. They are formed by static electricity and Van der Waals force which are too small to provide enough strength to directly use without any binders and reinforcement materials. However, the adding of binders and reinforcement materials reduces contents of mica in the material, so as to the insulation property. For the purpose of maintaining the insulation properties and improving mechanical strength, high strength composite material is made by mica and other material. Aramid fiber has extremely high strength and excellent insulation performance. The composite of mica and aramid fiber can improve strength of material.In this paper,8% of aramid fibers are added to mica pulp to make aramid mica paper. The strength of interface bonding is improved by proper mica material, pulp making methods, mica surface modification, aramid fiber dispersing and modification, so as to the strength of composite. Properities of aramid/mica paper with 8% of aramid fibers contents are similar to products of Dupont which 50% of aramid fibers were added. Process of producing can be simplified by manufacturing of this kind of composite without process of gluing and reinforcement. Through the experiments best conditions of process parameters are determined, conclusions as follows are obtained:1. Calcinations chemical pulp making method is chosen as the better pulp making method by the properties of mica paper and aramid mica paper made of those pulps. Particle size of mica pulp is discussed to get the conclusion that wide particle size range is better for the property improvement of composite material.2. Avoiding ions, SS and alkaline water which can effect the strength of aramid/mica paper is the basement to produce high performance paper. Kinds of modifiers are used to the modification of mica. Among those modifiers polyacrylamide and starch have excellent modification effects. Starch if better than polyacrylamide and cationic starch get the best. Aramid mica paper made of mica flakes modified by starch modifier is 277.5% times better than that without any modification. The best conditions of adding modifier are 10kg/t dosage,16% concentration of pulp,30min modification time. The adding of modifier has no effects to the dielectric property of composite material. 3. Among the modification methods of aramid fiber ultrasonic modification has benefit to the improvement of surface activity and micro fibrosis. Meanwhile, complementary with silane coupling agent modification, surface force of fibers and strength of materials are improved. Composite paper made of modified aramid fibers and mica flakes have a tensile strength of 28.56N/cm compares with 23.97N/cm, 19.1% high than without any modification of aramid fibers. PEO combining with dodecylbenzenesulfonic acid sodium is benefit for the dispersing of aramid fibers which can improve the uniformity and softness of composite material.4. Pulp mixing process is better than the other two processes for the paper making of composite material, and best process parameters are determined.5. Hot press process is also discussed so as to get the best process parameters. After hot press tensile strength, dielectric strength, fold resistance degree, density and softness of aramid mica paper are tested and compared with NOMEX 418 including mechanical strength, high temperature resistance, insulation property and stability. Among those properties, aramid mica paper has better tensile strength and dielectric strength, same high temperature resistance and stability, just a little poor in volume resistivity and dissipation factor.6. The enhancement mechanism of aramid mica paper compound is discussed. The modification of mica flakes and aramid fibers can improve interface bonding performance, plasticity and overall performance.The producing of aramid/mica paper is important to mica insulation material. Firstly, the emergence of aramid mica paper ends the situation of without concerned high performance products. Secondly, aramid/mica paper can reach a high strength which can be usded directly without any other reinforcement material. Improvement of mica contents can extense application time of material and improve security. With proper process mica insulation can form easily. Thirdly, the use of aramid fiber is useful to get thinner insulation which can be used in smaller electrical equipments. Finally, small amount of aramid fiber contents is benefit to cut the costs. It is significance to enlarge the category of mica insulation productions.更多还原