聚合物/层状硅酸盐纳米复合材料（PLSN）

摘 要
聚合物/层状硅酸盐纳米复合材料（PLSN）因其优越的力学性能、热稳定性、气体阻隔性等，受到广泛的关注。本文在大量文献调研的基础上，综述了聚合物/层状硅酸盐纳米复合材料的最新研究进展。作者采用常规熔融插层法制备了ABS/OMT、PC/OMT、PA6/OMT、PC-ABS合金/OMT等聚合物/蒙脱土纳米复合材料，研究了材料结构与性能特别是其与热稳定性能和燃烧性能的关系，着重讨论了OMT在PC/ABS合金中自聚集过程及其对合金性能的影响。在Alexandre工作的基础上，作者提出了制备PLSN的“新一步法”，对所制备的纳米复合材料的结构、性能及其插层机理进行了研究。本文还就PLSN在阻燃技术中的应用进行了详细的研究，制备了阻燃PA6和ABS纳米复合材料，研究了OMT在不同阻燃纳米复合体系中的阻燃机理。
本论文归纳起来主要分以下五个部分：

第一部分工作中，采用离子交换法对蒙脱土进行有机修饰，制备了有机蒙脱土（OMT），对其制备工艺、配方进行了研究，给出了制备OMT的优化中试工艺条件，XRD测试表明：该中试工艺制备的OMT质量稳定，层间距可控制在2.4－2.5nm。

第二部分工作中，通过熔融共混法成功制备了ABS/OMT、PC/OMT、PA6/OMT纳米复合材料。作者利用XRD、TEM、HREM、锥形量热仪等研究方法详细讨论了OMT的粒径对ABS/OMT纳米复合材料结构和燃烧性能的影响，结果表明粒径小的OMT有利于形成层离型纳米复合材料，粒径大有利于形成插层型纳米复合材料，且插层型纳米复合材料比层离型纳米复合材料更能有效地降低ABS热释放速率。利用XRD、TEM等研究方法详细讨论了OMT表面有机修饰的比例对PA6/OMT复合材料的结构及结晶形态的影响，分析表明，以纳米尺度分散的OMT能够促进PA6的 γ晶型的形成，而OMT表面有机修饰比例太高或太低都不利于OMT在PA6中的纳米分散。

第三部分工作中，利用XRD，TEM，TGA等方法研究了OMT在PC-ABS合金及PA6-ABS合金两相中分散状态及结构，研究发现：在PC-ABS合金/OMT纳米复合材料中，OMT主要分布于ABS相中，而在PA6-ABS合金/OMT纳米复合材料中，OMT分布于PA6和ABS两相，但主要集中在PA6相中。PC/OMT和ABS熔融共混过程中，随着共混时间的延长OMT会动态自聚集在ABS单一物相中。研究同时表明：存在于PC相中的OMT会促进PC的热分解，在PC-ABS合金/OMT纳米复合体系中，由于OMT主要分布于ABS相中，能够消除或降低OMT对PC热分解的催化作用，增加PC-ABS合金的热稳定性。

第四部分工作中，作者对Alexandre提出的“一步法”进行了详细的研究，在此基础上作者提出“新一步法”，即使用MMT和有机改性剂预先共磨，然后再与聚合物熔融共混制备PLSN，研究表明：“新一步法”制备的PA6/MMT纳米复合材料，其蒙脱土的分散性及其拉伸性能都与传统方法制备的PA6/OMT纳米复合材料相当并优于“一步法”制备的PLSN。本文同时探讨了“新一步法”制备聚合物纳米复合材料的结构影响因素及其插层机理，研究表明：改性剂用量和种类是影响PLSN结构的关键因素。 “新一步法”是制备PLSN的一种有效的方法，既简化了粘土水相体系改性的工艺，降低了成本，又改善了“一步法”中有机修饰剂的扩散受聚合物基体限制这一不足，在制备过程中有机修饰剂（如C16）不仅能对MMT片层表面进行有机修饰，同时还能作为聚合物分子链插层的载体，促进MMT纳米复合结构的形成。

第五部分工作中，选用OMT配合不同的阻燃体系对聚合物进行阻燃，制备了PA6和ABS的阻燃纳米复合材料。采用锥形量热、UL-94 V-0垂直燃烧，限氧指数（LOI）三种测试方法综合评价材料的阻燃性能，详细研究了OMT在不同阻燃体系中的作用。研究发现DB-AO-OMT对PA6有良好的协效阻燃作用，在满足UL-94 V-0的阻燃级别的同时，热释放速率（HRR）峰值也比常规阻燃PA6-DB-AO降低38％。而MCA-OMT对PA6不能形成有效的阻燃体系，虽然HRR峰值有所降低，但达不到UL-94 V-0。OMT对MH-RP含磷阻燃体系阻燃ABS有较好的促进作用，加入5％的OMT可使LOI提高1－1.5，同时5％的OMT代替10％MH可达到相同的阻燃效果。在热释放速率（HRR）、UL-94垂直燃烧、氧指数测定中，ABS-DB-OMT和ABS-DB-AO-OMT阻燃纳米复合材料都表现出良好的性能。最后作者从阻燃机理的匹配性、OMT和阻燃剂的协效作用等多个角度总结了影响聚合物阻燃纳米复合材料阻燃性能的因素。

Abstract
Polymer/layered silicate nanocomposites (PLSN) is a novel type of advance composites, which has been become the focus of research in recent years. Due to their unique structures as well as mechanical、 thermal and gas/liquid barrier properties compared with their conventional counterparts, PLS nanocomposites has broadened applying potentiality in industry. The new progress about PLSN was reviewed in this paper based on the recent references as well as the relative works in our group. We prepared ABS/OMT, PC/OMT, PA6/OMT, PC-ABS alloys/OMT nanocomposites by conventional melt-mixing technique. Then the relationship between structure and properties especially thermal stability and flammability properties of PLSN was studied. The self-organization of OMT in PC/ABS polymer alloys and the thermal stability of PC-ABS alloys/OMT were discussed in details. Base on the work of Alexandre, we firstly provided “new one step” method to prepare PLSN and studied on the preparation, characterization and intercalative mechanism of PA6/MMT nanocomposites made by “new one step” method. Finally, the application of PLSN in flame retardancy was studied.
In summery, this dissertation is composed of five parts.
In the first part, modified montmorillonite (OMT) was prepared by ion exchange reaction using hexadecyltrimethyl ammonium bromide (C16) in 1000 litre retort, the quality of OMT was controlled at range of 2.4－2.5nm by XRD test.
In the second part, ABS/OMT, PC/OMT, PA6/OMT nanocomposites were prepared using direct melt intercalation technique by blending polymer matrix and OMT. The effect of particle size of OMT on the structure and flammability property of ABS/OMT nanocomposite was characterized by XRD, transmission electron microscopy (TEM), high resolution electronic microscope (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results revealed that the smaller particle size of OMT was favor to the formation of exfoliated structure of nanocomposite, while the larger one was favor to the formation of intercalated structure, furthermore an intercalated structure was more effective than an exfoliated structure as far as heat release rate (HRR) was concerned. The structure and thermal stability of PC/OMT nanocomposite were studied using XRD, TEM and TGA. The results indicated that nanodispersed OMT enhanced the thermal decomposition of PC matrix. The modified degree of clay surface was chosen as factors to study the morphology of PA6 hybrids and crystalline phase transition of PA6. The results indicated that there was an optimal grafting density for forming PA6/OMT nanocomposites and the dispersion of PA6 molecules in confinement condition of silicate layers would greatly affect the phase transition of PA6.
In the third part, PC-ABS polymer alloys/OMT and PA6-ABS polymer alloys/OMT nanocomposites were prepared using direct melt intercalation technique. Their structures were characterized by XRD and TEM. The results of TEM showed that the silicate layers dispersed differently in two phases. In PC-ABS/OMT nanocomposite, the silicate layers were self-organized in ABS phase, while in PA6-ABS/OMT nanocomposite, the silicate layers were dispersed in both phases but mainly in the PA6 phase. Furthermore, the PC/OMT nanocomposite was melt-mixed with pure ABS, and the changed morphology of the hybrid with the prolonged time of melt-mixing was characterized by XRD and TEM, in order to study the dynamic self-assembly of clay layers in polymer alloys. The study of TGA indicated that adding OMT (5wt%) enhanced the thermal degradation of PC while by adding ABS to PC could avoid this catalytic effect. OMT enhanced the formation of char and improved the thermal stability of PC/ABS alloys.
In the fourth part, we have studied the “one step method” reported by Alexandre in details, and provided “new one step method”, that was firstly grinding MMT and compatibilizer together thoroughly in a mortar and pestle, and then, melt-mixing with polymer matrix to yield hybrids. PA6/MMT nanocomposites were prepared by melt intercalation technique direct from MMT using “new one step” method. Several cation and anion surfactants were chosen as clay/matrix reactive compatibilizers. The intercalation spacing and degree of dispersion were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicated that the “new one step” method was superior to “one step” method as far as the dispersion degree of clay layers and the tensile strength of PLSN were concerned. Moreover, in “new one step” method, C16 served to modify the clay layers as well as swelled the clay layers and could act as a carrier to transport the chains of matrix into the interlayer of clay simultaneously.
In fifth part, flame retardant PA6/OMT and ABS/OMT nanocomposites were prepared using direct melt intercalation technique by blending PA6 or ABS, organophilic clay and different conventional fire retardants together. Their morphology and combustion properties were characterized by XRD, transmission electron microscopy (TEM), UL-94 test, limiting oxygen index (LOI) test and cone calorimeter experiments. The study of UL-94 and cone calorimeter experiments indicated that the PA6-OMT/DB-AO satisfied both UL-94 and cone calorimeter experiments while PA6-OMT/MCA satisfied only cone calorimeter experiment and failed UL-94 V-0 test. OMT could enhance the flame retardancy of MH-RP system in ABS matrix. LOI increased 1~1.5 when adding 5wt.% while kept the same content of MH and MRP, or, using 5wt% OMT as a substitute for 10wt% of MH, the values of LOI almost kept the same. Flame retardant ABS-OMT/DB and ABS-OMT/DB-AO nanocomposites evaluated by cone calorimeter experiment and conventional testing methods using limiting oxygen index (LOI) as well as the vertical burning test (UL-94) all showed improved properties in comparison to microcomposites. The roles of OMT in flame retardant PLSN were studied in the aspect of compatibility of fire retardant mechanism and the synergetic effect among OMT, conventional fire retardants and polymer matrix.

英文缩写对照表
ABS 丙烯腈－丁二烯－苯乙烯共聚物
AO 三氧化二锑
CEC 离子交换容量
DB 十溴联苯醚
DSC 差热扫描热分析
EVA 乙烯－醋酸乙烯酯共聚物
FTIR 傅立叶红外光谱仪
HDPE 高密度聚乙烯
HREM 高分辨透射电子显微镜
HRR 热释放速率
LOI 极限氧指数
MCA 三聚氰胺三聚氰酸盐
MMT 蒙脱土
OMT 改性蒙脱土（有机蒙脱土）
PA6 尼龙6
PA6-ABS (or PA6/ABS) 尼龙6－ABS合金
PC 聚碳酸酯
PC-ABS (PC/ABS) 聚碳酸酯－ABS合金
PE 聚乙烯
PLS 聚合物/层状硅酸盐
PLSN 聚合物/层状硅酸盐纳米复合材料
PS 聚苯乙烯
PU 聚氨酯
SEM 扫描电子显微镜
TEM 透射电子显微镜
TGA 热失重分析XRD X射线衍射