【作者】 葛春华；

【导师】 施利毅；

【作者基本信息】 上海大学 ， 材料学， 2010， 博士

【摘要】 聚合物基无机纳米复合材料是现代材料学研究的重点课题之一,其开发和应用具有重要意义。针对当前国内纤用聚酯生产能力过剩,聚对苯二甲酸乙二酯(PET)工程塑料生产能力低的现状,本文选用新型无机功能填料—纳米重晶石(barite),采用熔融共混的方法制备了PET/Barite纳米复合材料。系统地研究了纳米barite对PET结晶性能、动态力学性能和力学性能等的影响,以及马来酸酐接枝乙烯—辛烯共聚物(POE-g-MA)、乙烯—丙烯酸甲酯—甲基丙烯酸缩水甘油酯(E-EA-GMA)和微胶囊化红磷(MRP)的加入对PET/Barite纳米复合材料性能的影响,并对改性机理进行了探讨,以指导高性能PET工程塑料的制备。主要内容和研究结果如下：1.研究了纳米barite表面性质和含量对PET结晶性能、动态力学性能和力学性能等的影响。结果表明,纳米barite在PET结晶过程中起到了明显的异相成核作用,加快了结晶速率。在等量添加下,硬脂酸改性纳米重晶石(SABarite)比未改性纳米重晶石(UNBarite)具有更高的成核活性,PET结晶速率提高更快。WAXD分析表明,PET大分子链与SABarite纳米粒子之间的强界面作用导致晶面发生择优取向,倾向于生成PET的典型晶面衍射峰。无机纳米粒子自身的高刚性,并且加入的纳米barite与PET基体之间形成了一种刚性的界面层,提高了PET的储能模量E’和玻璃化转变温度Tg。SABarite纳米粒子表面的长烷基链与PET分子之间发生物理缠结,限制了PET分子链段的运动,随着SABarite含量的增加,PET的E’和Tg升高。纳米粒子的高异相成核活性,使纳米复合材料中非晶区的分子链具有更大的活性,导致相同含量下,PET/SABarite纳米复合材料的E’和Tg值比PET/UNBarite纳米复合材料要低。纳米barite促进PET结晶,从而对基体产生明显的增强作用。热变形温度的研究表明,纳米barite提高了纳米复合材料的热稳定性。SABarite纳米粒子表面包覆的有机小分子降低了纳米复合材料的热稳定性,但仍高于纯PET。2.研究了纯PET和PET/Barite纳米复合材料的等温结晶过程特征。结果表明等温结晶过程中,纯PET的二次结晶现象严重,加入纳米barite能减少PET的二次结晶,提高晶体的完善程度。纯PET的Avrami指数n大都大于4。纳米复合材料的n值在2～4之间,晶体以三维方式生长,伴随着从瞬时成核到散现成核的成核机理转变。加入两种无机纳米粒子均能降低成核能垒,从而降低等温结晶活化能ΔEa,其中又以SABarite效果更显著。3.研究了纯PET和PET/Barite纳米复合材料的非等温结晶过程,并用Jeziorny、Ozawa和Mo方法进行动力学分析。结果表明,Mo法能很好地分析纯PET和PET/Barite纳米复合材料的非等温结晶过程。动力学数据表明,加入纳米barite提高了PET的结晶速率,其中以SABarite纳米粒子促进结晶的效果更明显。引入纳米UNBarite,晶核的生成加快,PET结晶更易进行,非等温结晶活化能ΔE低于纯PET;而SABarite纳米粒子和PET分子链间的强界面作用,使链段重排受限,减慢了晶体的生长过程,导致纳米复合材料的ΔE大于纯PET,并且ΔE随着SABarite含量的增加而增加,但其成核作用仍占主导地位。4.研究了两种官能团化聚烯烃弹性体POE-g-MA和E-EA-GMA对PET/SABarite纳米复合材料进行增韧改性。结果表明在不同弹性体含量时,三元复合材料都发生脆韧转变,增韧效果显著。等量添加下,E-EA-GMA的增韧效果明显好于POE-g-MA。DSC分析表明,弹性体的加入,严重阻碍了PET分子链段的运动,减慢PET/SABarite结晶速率,降低PET晶体的完善程度。5.研究了纳米SABarite与MRP的复配阻燃PET。结果表明,MRP与较高含量的纳米SABarite之间有较好的协同阻燃效应；当PET/MRP/SABarite质量比为100/5/10时,复合材料的氧指数为32.7%,垂直燃烧可达UL94V-0级,此时复合材料力学性能较好,熔滴现象得到缓解。热重分析表明纳米粒子的存在提高了PET的热稳定性和促进成炭。将研究结果应用于高性能PET工程塑料制备,并与美国杜邦公司同类产品进行比较分析。结果表明,各项性能基本相当,完全可以替代。更多还原

【Abstract】 Current domestic production of fiber-forming polyester is overcapacity, while the production status of poly(ethylene terephthalate) (PET) engineering plastics just the reverse. Used a novel functional nanoparticle—nano-barite as filler, PET/Barite nanocomposites were prepared by direct melt compounding. The effects of surface nature and contents of barite nanoparticles on the crystallization, dynamic mechanical and mechanical properties were investigated systematically. In order to improve the mechanical properties and flammability of PET/Barite nanocomposites, maleic anhydride grafted polyethylene octane copolymer (POE-g-MA), ethylene-ethylacrylate-glycidylmethacrylate copolymer (E-EA-GMA) and microencapsulated red phosphorus (MRP) were employed to modify them, and to prepare PET engineering plastics with high performance. Furthermore, the modification mechanism was also discussed. The main content and results were as follows:1. The effects of surface nature and contents of barite nanoparticles on the crystallization behaviors and mechanical properties of PET were studied. The results showed that a small amount of UNBarite or SABarite added into PET matrix can act as efficient nucleating agents and improve the crystallization rate of PET but SABarite shows higher efficiency. SABarite nanoparticles induce preferential lamellae orientation because of the strong interfacial interaction between PET chains and SABarite nanoparticles, which is not the case in UNBarite filled PET as determined by WAXD. The rigid inorganic nanoparticles possess high rigidity and induce an increase in the interfacial stiffness, thus PET/Barite nanocomposites have the higher value of storage modulus (E’) and glass transition temperature (Tg) than pure PET, which would increase with increasing SABarite content. SABarite nanoparticles have excellent interfacial interaction with PET through physical entanglement of alkyl chains at the interface. The increased interfacial interaction constrains motion of PET molecular chain segments, leading to an increase of Tg·Surprisingly, both E’ and Tg of PET nanocomposites filled with SABarite were a little lower than that of unmodified UNBarite at the same concentration, which could be attributed to the higher heterogeneous nucleating activity of SABarite than that of UNBarite, therefore resulting in an increase of crystallization rate, i.e. polymer molecular chains in amorphous region exhibit higher mobility and thus reduce the E’ and Tg·Barite nanoparticles can facilitate the crystallization process and thus clearly reinforce the PET matrix. Compared with pure PET, the maximum tensile strength and flexural modulus of PET/SABarite nanocomposites increase by 18.5 and 21.7 at 0.5 and 3.0 wt% and that of PET/UNBarite nanocomposites increase by 9.4 and 21.9 both at 3.0 wt%, respectively. The thermal stability of the nanocomposites is enhanced by addition of barite nanoparticles. The incorporation of organic small molecule group on the surface of modified nanoparticles reduce the thermal stability of the nanocomposites, but still higher than that of pure PET.2. Isothermal crystallization process of pure PET and PET/Barite nanocomposites were analyzed. In the isothermal crystallization process, pure PET demonstrate stronger secondary crystallization process than that of PET nanocomposites, in which more homogeneously sized spherulites formed from barite nucleation. The crystalline phase in PET/Barite nanocomposites is more perfect than that of pure PET. The strong nucleation activity of the SABarite nanoparticles could further increase the crystal perfection. The Avrami exponent n for pure PET is more than 4 by and large. For PET nanocomposites, the n ranges between 2 and 4, the spherulites are thought to be grown in a 3D morphology from heterogeneous nuclei, accompanied by the change in nucleation mechanism from instantaneous nucleation to sporadic nucleation. The addition of barite nanoparticles decreases the isothermal crystallization activation energy. The enhanced interfacial interaction reduces the crystallization free energy barrier for nucleus formation.3. The nonisothermal melt crystallization kinetics of pure PET and PET/Barite nanocomposites was also studied, where a kinetic analysis was made by Jeziorny, Ozawa and Mo methods. The results demonstrated that Mo method is successful in describing the nonisothermal crystallization kinetics of pure PET and its nanocomposites. Analysis of the crystallization process shows that the crystallization rate increases with adding barite nanoparticles. UNBarite nanoparticles promote the overall crystallization process of PET matrix by improving the nucleation process, so the occurrence of crystallization is more easily than that of pure PET due to the lower△E. However, SABarite nanoparticles retard the rearrangement of PET chain segments to some extent due to the strong interfacial interaction between two phases, thereby decreasing the crystallization ability, but the nucleation effect is still dominant role on the crystallization of PET matrix.4. Two types of functional polyolefin elastomers were employed to toughen the PET/SABarite nanocomposites. At the appropriate elastomer content, brittle-to-ductile transition of ternary compositions takes place, indicating that both elastomers have a significant toughening effect on PET. Found that, at the same content, E-EA-GMA is more effective in toughening PET/SABarite nanocomposites than POE-g-MA, which resulted from its better compatibility with PET. Differential scanning calorimetry analysis showed that the addition of elastomers restrict the mobility of PET molecular segments, lower the crystallization rate and reduce the crystal perfection of PET/SABarite nanocomposites.5. The flame retardancy, mechanical and thermal behaviors of PET filled with complex flame retardant composed of SABarite and MRP have been studied. Combination of MRP and SABarite shows effective synergistic effect. Limited oxygen index (LOI) value decreases and subsequently increases with the addition of nanoparticles as the content of MRP is designated at 5 wt%. When the mass proportion of PET, MRP and SABarite is 100/5/10, the LOI is 32.7%, UL94 rating is V-0. Meanwhile, flame-retardant nanocomposites exhibit good mechanical properties and antidropping behavior. TGA analysis shows that the introduction of nanoparticles can greatly enhance the thermal stabilities and charring abilities of PET. Glass fiber reinforced and/or halogen-free flame-retardant PET engineering plastics prepared in present thesis can be used as a substitute for similar products provided by Dupont.更多还原