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题名	由菱镁矿制备高分散片状氢氧化镁及其表面改性研究
作者	杨素萍
学位类别	硕士
答辩日期	2012-05-23
授予单位	中国科学院研究生院
导师	卢旭晨
关键词	菱镁矿 氢氧化镁 球磨 水热 表面改性
其他题名	Preparation and surface modification of high dispersive lamellar magnesium hydroxide particles from magnesite
学位专业	化学工程
中文摘要	氢氧化镁阻燃剂具有无毒、热稳定性高、抑烟效果好等特点，是近年来广泛应用的一类新型无机阻燃剂。综合考虑氢氧化镁阻燃剂的发展前景以及我国菱镁矿资源的优势，本文采用菱镁矿为原料，通过煅烧、湿法球磨、水热处理、表面改性制备高分散的片状MH阻燃剂，并将其应用至室温硫化硅橡胶（RTVSR）中考察其阻燃性能。本文较系统地研究了湿法球磨与水热处理对MH颗粒晶体结构、形貌、分散性等性能的影响，初步探讨了本工艺MH颗粒的晶体生长机理。研究了湿法球磨工艺条件对MH颗粒表面改性效果的影响以及MH颗粒性质对改性效果及阻燃效果的影响。 通过考察煅烧温度和时间对轻烧氧化镁活性以及活性氧化镁含量的影响得到菱镁矿的最佳煅烧工艺。当煅烧温度为650℃，煅烧时间为3.5h，轻烧氧化镁的活性较好，活性氧化镁的含量最高，约为89.33%。 通过对轻烧氧化镁进行湿法球磨处理，发现湿法球磨可以加速MgO的水化速率，使大部分轻烧MgO快速水化成MH，为水热晶化处理提供分散性较好的前躯体。以聚乙二醇400(PEG400)或聚乙烯吡咯烷酮K30(PVP)为助磨剂，球料比质量为20:1?30:1时，对轻烧MgO湿法球磨2?4h，可明显改善水热产物MH颗粒的分散性，减小其粒径，缩小粒度分布。 通过对湿法球磨后的浆料进行水热处理，可快速地使浆料中残留的MgO水化成MH，且进一步完善原有片状MH颗粒的晶体结构和形貌。水热温度、水热时间、碱浓度均是影响MH颗粒晶体结构和粒径的重要因素。 初步探讨了通过湿法球磨-水热处理工艺制备的MH颗粒的晶体生长机理：在湿法球磨过程中，大部分的MgO快速溶解、水化成MH初级粒子，这些初级粒子通过取向连接形成片状MH颗粒。在水热处理过程中片状MH颗粒在原有基础上不断发育完全，而残余的MgO可能通过溶解作为MH晶粒进一步生长的原料。 为改善MH颗粒的有机相容性，采用湿法球磨的方式对市售的氢氧化镁和自制的氢氧化镁进行表面改性。研究发现球磨工艺条件，如球磨时间、球料比、水料比和表面改性剂用量等均是影响MH颗粒改性效果的重要因素。此外，MH颗粒的自身性质，如表面电性、极性和比表面积也严重影响着MH颗粒的表面改性效果。MH颗粒经过表面改性后表面吸附有改性剂，且MH颗粒与改性剂之间形成了新的化学键，MH颗粒的表面极性减弱，在RTVSR基底材料中具有较好的相容性和阻燃性。MH颗粒的自身性质，如粒径和形貌，影响其阻燃效果，在分散性好的前提下，片状的、粒径小的MH颗粒阻燃效果好。
英文摘要	Magnesium hydroxideis (MH) is widely used as a kind of inorganic flame retardant recently due to its advantages, such as toxic-free, high decomposition temperature, good smoke suppression. Taking the good development of MH flame retardant and abundent magnesite resources in China into consideration, we used magnesite as raw material and prepared lamellar MH with high dispersion by calcination, wet milling, hydrothermal treatment and surface modification. And lastly we employed the MH particles in room temperature vulcanized silicone rubber as flame retardant and tested the flame retardancy of the composite materials. In the thesis, we studied the effect of wet milling and hydrothermal treatment on the crystal structure, morphology and dispersibility of the MH particles, and discussed the crystal growth mechanism of the MH particles. In addition, we discussed the effect of wet milling factors on surface modification and the effect of MH properties on surface modification and flame retardancy. The optimum calcination conditions were determined by studying the effect of calcining temperature and time on the activity of calcined magnesite and the content of actived MgO. The calcined magnesite had higher activity and the content of actived MgO was 89.33% when magnesite was calcined at 650℃ for 3.5h. Calcined magnesite was wet milled first. It’s found that wet milling can accelerate the hydration reaction of calcined magnesite and most of MgO can be hydrated to MH fast in the process. Most importantly, wet milling can provide MH precursors with high dispersion for the following hydrothermal treatment. When PEG400 or PVP was used as grinding aid to mill the calcined magnesite for 2?4 h with ball?powder mass ratio between 20:1?30:1, the dispersibility of MH particles was largely improved, and the particle size and size distribution of MH particles also decreased. Subsequently, the wet milled slurry was hydrothermal treated. MgO crystals that remained in the slurry could be rapidly hydrated to MH and the crystal structure and morphology of lamellar MH particles prepared by wet milling could be improved during the process of hydrothermal treatment. The hydrothermal temperature, hydrothermal time, alkali concentration are important factors affecting the crystal structure and particle size of MH particles. The crystal growth mechanism of MH particles prepared by wet milling-hydrothermal treatment was disussed. It’s considered that wet milling can accelerate the dissolution rate of MgO crystals and the dissolved MgO crystals are hydroxylated into MH primary particles which aggregate to produce large lamellar particles through oriented attachment before hydrothermal treatment. Moreover, the crystalline structure and morphology of MH particles can be improved and the remained MgO crystals may act as nutrition for the MH particles growth during hydrothermal treatment. In order to improve the organic compatibility of MH particles, surface modification of the commerce MH and prepared MH was carried out. The study shows that milling conditions, such as milling time, ball-powder mass ratio, water-powder mass ratio and surfactant content are important factors affecting the modification results. And the properties of MH particles, such as surface charge, surface polarity and specific surface area also affact the modification results. After the surface modification, surfactants were absorbed on the surface of MH particles with new chemical bonds forming and the surface polarity of the MH particles was weakened. The surface-modified MH particles had better compatibility and flame retardancy when filled into RTVSR. And the properties of MH particles, such as particle size and morphology affact the flame retardancy. The results show that lamellar and small size MH particles with good dispersion have better flame retardancy.
语种	中文
公开日期	2013-09-25
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/1838]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	杨素萍. 由菱镁矿制备高分散片状氢氧化镁及其表面改性研究[D]. 中国科学院研究生院. 2012.

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