【作者】 安晶晶；

【导师】 王海侨；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2010， 硕士

【摘要】 作为重要的工程塑料,聚酰胺66(俗称尼龙66)具有较好的拉伸强度,耐磨性,耐腐蚀性,白润滑和良好的加工性能。但是,由于含有极性基团,所以吸水率大,从而影响加工性能和尺寸稳定性,进而限制了尼龙66的应用。为了提高尼龙66的综合性能,本文采用双螺杆挤出机制备了一系列不同共混比例、不同原始颗粒尺寸PHE以及不同加工条件的PA66／PHE共混物。然后通过DSC、SEM、POM、WXRD和力学性能测试来对PA66／PHE共混物的结晶性能和力学性能进行测试。研究发现,不同颗粒尺寸的PHE以及改变加工条件主要是对共混物的相形态和力学性能有明显的影响,对共混物的结晶性能没有产生明显的影响。对PA66／PHE共混物的形态和力学性能的研究结果显示：随着PHE的加入,PA66／PHE共混物的形态发生了转变,由连续相-分散相转变为共连续相。当使用原始颗粒尺寸较小的PHE时,PA66／PHE共混物的相尺寸较小,而且分散均匀。同时,加工条件也会对相形态产生影响,我们发现在强的剪切作用下,PA66／PHE共混物的分散相尺寸更小。当使用小颗粒尺寸的PHE时,PA66／PHE共混物的冲击强度有所提高,拉伸强度则略高于纯的尼龙66,但是两者都呈现协同效应。当使用大颗粒尺寸的PHE时,共混物的冲击强度下降,而拉伸强度却得到提高,甚至高于小颗粒尺寸的PHE制备的共混物的拉伸强度。当其他条件相同时,与弱剪切作用相比,强剪切作用下制备的共混物的力学性能更好,特别是当PHE含量较低的时候。我们也通过DSC、WXRD和POM对PA66／PHE共混物的结晶、熔融行为进行了研究,结果显示：当PHE含量小于10%时,PHE的加入使得共混物的结晶温度增加,共混物中晶体的尺寸也减小；当PHE含量大于10%时,随着PHE含量的增加,共混物的结晶温度降低,晶体尺寸增大。原因可能是当PHE含量较少时,PHE是比较好的成核剂,从而加快了尼龙66的结晶速度,缩短了结晶时间,提高了结晶温度,以及使得共混物中的PA66晶体的尺寸减小；当PHE含量较多时,PA66／PHE共混物的形态发生转变,PHE开始阻碍尼龙66的结晶,降低结晶速度,从而延长了结晶的时间,进而使得尼龙66晶体的尺寸增大。由于PHE的加入起到稀释效应或是使得PA66晶体的完善程度降低,从而使得共混物的熔点降低。另外,测试结果还显示,相比较而言,PHE的加入促进了晶型的生长,阻碍了晶型的生长。更多还原

【Abstract】 Polyamide 66 (commonly known as nylon 66) is an important engineering plastics with high strength wear resistance, corrosion resistance, self lubrication and outstanding fluid processing properties. However, strong water absorption affect the processing properties and dimensional stability because of its rich of polar groups limited its application. In order to improve the integrated property of nylon 66, polyamide 66/poly(hydroxy ether of bisphenol A) (PHE) blends were prepared by a dual-screw extruder in the whole composition range. PHE with different sizes of raw materials were adopted in this research. The PA66/PHE blends were characterized by DSC, WXRD, POM, SEM and so on. The results show that the different size of original PHE and processing conditions remarkably affect the morphology and mechanical properties of PA66/PHE blends while have no influence on the crystalline of the blends.The investigation of the morphology and the mechanical properties of blends showed that the addition of PHE changed the morphology of PA66/PHE blends:from continuous phase-disperse phase to co-continuous phase. When smaller PHE particle is used as the original material, the phase size of PA66/PHE blends are more small and the dispersion and distribution are more homogeneous. The processing conditions can also affect the phase morphology. We find that under the stronger shear force the disperse phase of PA66/PHE blend are smaller.When PHE with small particle size (remarked as PHE-S) was used, the impact and tensile strength of PA66/PHE blends were improved by the addition of the PHE, and presented synergistic effect. When PHE with big particle size (remarked as PHE-B) was used, the impact strength of blends was reduced, but the tensile strength of blends was elevated even higher than that of the corresponding blend started by PHE-S. When other conditions are the same, compare to weaker shear force, stronger shear force leads to better mechanical properties, particularly at low PHE content.The melting and crystallization behaviors of PA66/PHE blends were also investigated in this work by differential scanning calorimetry (DSC), Wide-angle X-ray diffraction (WXRD) and Polarizing optical microscope (POM). The results showed when the content of PHE is below 10%, with the increasing of PHE content the crystallization temperature of blends decreased and the size of PA66 crystal were reduced. When the content of PHE is higher than 10%, the crystallization temperature then decrease with increasing of PHE content. The reasons may be that at low PHE content, the PHE was a good nucleating agent, which could evaluate the crystallization rate of PA66, shorten the half-time of crystallization, increase the crystallization temperature, and reduce the size of PA66 crystal; at high PHE content, the morphology of PA66/PHE blends is inversed, the PHE could hinder the crystallization of PA66, reduce the crystallization rate of PA66, which prolong the half-time of crystallization, and enlarged the size of PA66 crystal. The addition of PHE also reduced the melt temperature of blends, which result from the dilution effect of PHE that reduced the degree of PA66 crystal. The result also showed that the addition of PHE promoted the growth ofα2 crystal, and hindered the growth ofα1 crystal.更多还原