二维纳米材料改性线性低密度聚乙烯

LINEAR LOW DENSITY POLYETHYLENE MODIFIED BY TWO-DIMENSIONAL NANOMATERIALS

李涛

11749100

硕士

材料学

孙大陟

2019-05-24

2019-07-11

哈尔滨工业大学

深圳

磷酸氢锆（ZrP）是一类具有层状结构的无机化合物，作为一种新型的二维纳米材料，除了具有层状材料共同优势外，还具有尺寸大小可控、结晶度高、纯度高、优良的机械性能和热性能等。因此可将其用于高分子复合材料当中，增加复合材料的韧性和拉伸程度，提升材料的稳定性，抗氧化性和抗老化性。线性低密度聚乙烯作为第三代聚乙烯也越来越多的得到人们的关注，优异的耐环境应力开裂性能、抗老化性能、耐酸碱性能等使其被应用于各行各业，但是线性低密度聚乙烯的耐热性能较差，强度较低，因此需要通过改性来提高强度和耐热性能。本文通过ZrP来增强改性LLDPE，探讨了该复合材料的力学性能和热稳定性能。首先，通过超声插层法将异辛胺插入到ZrP层间和表层制得了OZrP。XRD和SEM表征手段证明了异辛胺成功插入到ZrP层间，使得层间距由初始的0.76 nm扩张为2.12 nm，而且OZrP仍然保持较完整的晶体结构。FT-IR结果表明，异辛胺的胺基和ZrP层间的羟基发生了氢键作用，使得异辛胺插入到层间。热重分析实验表明，插层后OZrP仍然具有良好的热稳定性。其次，通过共混法和注射成型制备了不同含量的LLDPE/ZrP纳米复合材料。拉伸性能结果表明，ZrP不仅可以提升LLDPE基体的模量，还可以大幅提升LLDPE的断裂伸长率。SEM结果表明，ZrP可以很好地分散在LLDPE树脂基体中，但是当含量超过10 wt.%后，团聚发生。XRD结果显示，LLDPE/ZrP纳米复合材料中ZrP仍然保持初始的晶体结构，未被LLDPE分子链插层和剥离；而LLDPE基体的晶体结构和形貌受到了一定影响，再结合DSC表征手段表明，ZrP起到异质成核效应，提高了LLDPE基体的结晶度。DMA结果表明ZrP可以提高LLDPE基体的储能模量，结果与机械性能一致。另外通过DMA结果估算得到的热变形温度也说明了，ZrP可以提升LLDPE的耐热性能。最后，通过相同的工艺手段制备了不同比例的LLDPE/OZrP复合材料，并与LLDPE/ZrP纳米复合材料的性能进行了对比。SEM表明，有机胺改性过的OZrP与LLDPE基体的相容性比无机ZrP更好。XRD结果显示，复合之后，OZrP仍然保持初始结构，未发生插层和剥离。拉伸性能表明，OZrP同样可以提升复合材料的模量和韧性，其对于材料模量的提升效果低于ZrP，但对于韧性的提升效果高于ZrP。DSC表明，OZrP对于材料结晶度影响较小。DMA数据表明，OZrP对于材料热变形温度的提升效果也低于ZrP。

As a new type of two-dimensional layered inorganic compound, α-zirconium phosphate (ZrP) not only shares the common advantages of the traditional layered materials, but also has excellent characteristics such as controllable size, high crystallinity and purity, excellent mechanical and thermal properties and so on. Therefore, ZrP can be used in polymer composites to increase the strength, toughness and thermal stability. At the same time, the oxidation resistance, aging resistance, friction resistance and acid and alkali resistance of the composites can be improved. As a third-generation polyethylene, linear low-density polyethylene (LLDPE) has been increasingly favored. Due to its excellent environmental stress crack resistance, anti-aging performance, acid and alkali resistance, etc., LLDPE has been applied to various industries. However, LLDPE has poor heat resistance and low strength, so it needs to be modified to improve strength and heat resistance. In this paper, the properties of LLDPE nanocomposites are improved by the ZrP. Meanwhile, the mechanical and thermal properties of LLDPE/ZrP nanocomposites have been characterized by various techniques. Firstly, the organophilic α-zirconium phosphates (OZrP) is prepared by ultrasonic intercalated method which means the isooctyl amine is inserted into the interlayers and surface of ZrP. XRD and SEM characterization methods are used to prove that isooctyl amine has been inserted into ZrP successfully, and the interlayer spacing has been changed from 0.76 nm to 2.12 nm. Moreover, the structure of OZrP is still remained. The FT-IR results show the hydrogen bonding interaction between isooctyl amine amino and hydroxyl, which is happened between the interlayers of OZrP. In addition, the experimental results of thermogravimetric analysis show that OZrP still remain good thermal stability after the intercalation.Secondly, the LLDPE/ZrP nanocomposites with different concentration are prepared by the blending method and the injection molding. The tensile tests show that not only can ZrP improve modulus of nanocomposites, but also can boost elongation at break of nanocomposites. Moreover, the SEM images indicate that the ZrP could be well dispersed in LLDPE matrix. However, the agglomeration would be formed when the content of ZrP is more than 10 wt. %. The XRD patterns show that the crystal structure of ZrP is still maintained in LLDPE/ZrP composites and has not been intercalated or exfoliated by LLDPE molecular chain. However, the crystal structure and morphology of LLDPE matrix are influenced by ZrP. It indicates that ZrP has heterogeneous nucleation effect to increase the crystallinity of LLDPE matrix combined with data of DSC characterization. In addition, it can be seen from the DMA results that ZrP could improve the storage modulus of LLDPE nanocomposites, and these results are consistent with the mechanical properties mentioned above. Moreover, the thermal distortion temperature (HDT) is estimated through the DMA results, and it can be noted that ZrP could improve heat resistant properties of LLDPE.Finally, the LLDPE/OZrP nanocomposites with different concentration are prepared by the same processing method, and the LLDPE/OZrP nanocomposites are compared with LLDPE/ZrP nanocomposites. As shown from SEM pictures, the compatibility between LLDPE matrix and OZrP modified by the organic amine is better than inorganic ZrP. XRD patterns indicate that the nanoplatelets remained the same crystal structures before and after being incorporated into the LLDPE matrices by melt compounding. The above phenomenon also suggests that no exfoliation of the embedded nanoplatelets occur during the melt processing. The tensile properties show that OZrP can also improve the modulus and toughness of the LLDPE nanocomposites. The effect of OZrP on the modulus of the material is lower than that of ZrP, but the effect of OZrP on the toughness of the materials is higher than that of ZrP. Moreover, the results of DSC indicate that OZrP has little effect on the crystallinity of the nanomaterials, and DMA data shows that OZrP has less effect on the improvement of thermal distortion temperature.

磷酸氢锆 线性低密度聚乙烯 复合材料 力学性能 耐热性能

zirconium phosphate linear low density polyethylene composites mechanical properties heat resistance

中文

联合培养

南方科技大学

李涛. 二维纳米材料改性线性低密度聚乙烯[D]. 深圳. 哈尔滨工业大学,2019.