氟化石墨/尼龙6复合材料结晶行为及力学性能的研究

CRYSTALLIZATION AND MECHANICAL PROPERTIES OF GRAPHITE FLUORIDE REINFORCED PA6 COMPOSITES

孙浩洋

11649146

硕士

材料工程

孙大陟

2018-06-01

2018-07-03

哈尔滨工业大学

深圳

材料轻量化是无人机、汽车、高铁、飞机等行业孜孜不倦追求的目标。实际生产生活中，常通过高分子复合材料代替金属材料这一方式来实现材料轻量化。材料轻量化能有效地减轻产品重量，从而达到提高交通工具的运输能力与运输速度、降低成本、节约资源与保护环境的目的。因此本文利用易剥离且超疏水的氟化石墨，通过简单的熔融共混的方法制备了适合轻量化高性能的氟化石墨/尼龙 6复合材料。并探究了氟化石墨的含量对尼龙 6 的结晶行为以及力学性能的影响。差示扫描量热法（DSC）测试结果表明相较于氟化石墨/尼龙 6 复合材料，纯尼龙6 拥有更完整的晶体结构，同时氟化石墨/尼龙 6 复合材料表现出了较高的开始结晶温度（To,c）表明氟化石墨在尼龙 6 中起到异质成核的作用。但是氟化石墨的加入阻碍了尼龙 6 晶体的生长，使氟化石墨/尼龙 6 复合材料的结晶度降低。X 射线衍射（XRD）分析证明氟化石墨/尼龙 6 复合材料中的结晶晶型以高模量的 α 晶为主，而纯尼龙 6 的结晶晶型以 γ 晶为主。氟化石墨/尼龙 6 复合材料拥有更低的 Tg表明氟化石墨能增加尼龙 6 分子的运动能力从而促进了 α 晶的形成。扫描电镜（SEM）分析与光学显微镜（OM）分析结果都表明，低浓度（≤1.0 wt%）的氟化石墨在尼龙 6 基体中分散良好，当氟化石墨的浓度大于 1.0 wt%时，氟化石墨在尼龙 6 基体中发生团聚。另一方面 SEM 结果也表明，熔融混炼能有效地将氟化石墨剥离成更薄的片层。同时通过 XRD 测试结果可以看出，在 0.5 wt%与 1.0 wt%氟化石墨含量的复合材料中，氟化石墨的特征衍射峰基本消失，证明氟化石墨能有效的剥离。拉伸测试结果表明，仅 0.5 wt%的氟化石墨就能使尼龙 6 的弹性模量提高21.4%左右，拉伸强度提高 9.8%左右。这是因为氟化石墨在基体中分散良好，且与尼龙 6 结合性强，另一方面氟化石墨能有效地促进 γ 晶向 α 晶转变。动态机械性能分析（DMA）结果也表明，氟化石墨/尼龙 6 复合材料不论在低温还是高温都有更好的力学表现。吸水测试表明，氟化石墨能有效地减少尼龙 6 的吸水率，且随氟化石墨的浓度增高，吸水量随之降低。随后的拉伸测试表明，相较于未吸水的尼龙 6 及其复合材料，吸水后尼龙 6 及其复合材料的断裂伸长率增加，但是拉伸强度降低。同时相较于吸水后的纯尼龙 6，氟化石墨能增强吸水后尼龙 6 的力学性能（断裂伸长率与拉伸强度）。因此氟化石墨/尼龙 6 复合材料是理想的轻量化材料。

Lightweight is one of the main goals pursued by the drone, automobile, high speed railway and aircraft industries. Usually, lightweight of materials is achieved bypreparing high-performance polymer composites with many advantages such asreducing weight, increasing transportation capacity and speed, reducing cost, saving resources and protecting environment. In our work, graphite fluoride (GrF) platelets, with easily exfoliated and superhydrophobicity properties, were directly incorporated into polyamide 6 (PA6) by simple melt processing without using any surfactant. The effects of GrF content on the crystallization and mechanical properties of PA6 were also investigated. Differential scanning calorimetry (DSC) results show that the crystal of neat PA6 is more perfect than that of GrF/PA6 composites. The higher starting crystallization temperature (To, c) of GrF/PA6 composites indicates that the GrF can service as heterogeneous nucleation agents in PA6 matrix. However, the addition of GrF hinders the growth of PA6 crystal, resulting in the decreased crystallinity of the composite. X-ray diffraction (XRD) analysis shows that the crystalline phase of the GrF/PA6 composites is dominated by high-modulus α crystal, while the neat PA6 is dominated by γ crystal. The favored formation of α crystal in the GrF/PA6 composites is due to the promoted movement of PA6 molecules by GrF, which is proved by the lower glass transition temperature (Tg) of GrF/PA6 composites. Scanning electron microscopy (SEM) and optical microscopy (OM) results indicate that the low concentration ( ≤ 1.0 wt%) GrF was dispersed well in PA6 matrix. When the concentration of GrF is exceeded than 1.0 wt%, the GrF show a slight aggregation in PA6 matrix. SEM results also indicate that after melting mixing, the GrF can effectivelyexfoliate to a thinner GrF platelet. At the same time, XRD results also exhibit that, for0.5 wt% and 1.0 wt% GrF/PA6 composites, the characteristic peaks of GrF disappear,indicating that the GrF can be effectively exfoliated. Tensile test results show that, compared with neat PA6, the elastic modulus and tensile strength of 0.5 wt% GrF/PA6 composites are increased by about 21.4% and 9.8%, respectively. Dynamic mechanical analysis (DMA) results also show that, in comparison of neat PA6, the GrF/PA6 composites exhibit better mechanical performance at low temperature or elevated temperature. This is because that the GrF is well dispersed in the matrix, and GrF composites have a high content of α crystal. The water absorption test shows that GrFcan effectively reduce the water absorption of PA6. Tensile test results, for absorbed water PA6 and its composites, show that the elongation at break shows an increase, while the tensile strength has a decrease. Meanwhile, GrF can enhance the mechanical properties (elongation at break and tensile strength) of absorbed-water PA6. Therefore, the GrF/PA6 composites are ideal lightweight materials.

轻量化 二维材料 氟化石墨 尼龙 6 结晶性能 力学性能

lightweight graphite fluoride polyamide 6 crystallization mechanical properties

中文

联合培养

南方科技大学

孙浩洋. 氟化石墨/尼龙6复合材料结晶行为及力学性能的研究[D]. 深圳. 哈尔滨工业大学,2018.