PAA膜结晶度和PEO结晶动力学的研究

【作者】 刘清泉；

【导师】 潘春跃；

【作者基本信息】 中南大学 ， 应用化学， 2003， 硕士

【摘要】 本文以聚丙烯酸(PAA)和聚氧化乙烯(PE0)为研究对象，以X射线衍射(XRD)和示差扫描量热(DSC)为主要表征手段，首先研究和探讨了聚丙烯酸及其盐的涂膜结晶度和亲水性之间的关系，然后研究了PEO及其与高氯酸锂复合体系的等温和非等温结晶动力学。 本文先分别合成聚丙烯酸、聚丙烯酸钠和聚丙烯酸锂。涂膜结晶度的测定鲜见报道。我们在确定X射线衍射法测量涂膜结晶度可行的基础上，分别测定和计算了以上三种涂膜的结晶度；再测定了水和甘油在其表面的接触角以及水在其表面的铺展过程，经计算分别得到各涂膜的表面张力、铺展速度常数值。将涂膜的结晶度、表面张力、铺展速度常数、以及平衡接触角与涂膜亲水性联系起来，深入讨论了它们之间的内在联系。结果表明：当涂膜化学成份不同时，阳离子的类型对表面性能的影响占主导作用；而当涂膜成份相同时，随涂膜结晶度的增大，涂膜表面张力增大，铺展速度常数增大，平衡接触角减小，即亲水性提高。 本文用DSC方法研究了PEO和复合体系的等温结晶动力学和非等温结晶动力学。用Avrami方法，Malkin方法对它们的等温结晶过程进行了分析，分别得到它们的动力学参数值。结果表明：PEO可能是按二维方式依热成核生长，复合体系的Avrami指数n与PEO体系的相差不大，可能是除了成核方式不同外，晶体的生长方式相同，且PEO体系在等温结晶的后期出现二次结晶现象；用Cebe等人提出的方法计算出它们的结晶成核和晶体生长活化能分别为：59.28KJ／mol、70.85 KJ／mol，表明PEO体系在等温条件下更易结晶。非等温条件下的DSC曲线表明，PEO在冷却速率逐渐减小的同时，放热峰出现拖尾现象，说明PEO随冷却速率的减小，二次结晶的程度增加。然后用Jeziorny方法和莫志深等人提出的一种新方法对其非等温结晶进行了分析，得到PEO在非等温条件下的动力学参数值；以Kissinger中南大学硕士论文摘要方法计算了其非等温结晶成核和生长活化能分别为:149.68KJ/m。1、159.51 KJ/mol，再次表明PEO体系更易结晶。动力学参数表明，较快的冷却速率可使过冷度较快增加从而为系统提供较大的能量，加速了聚合物链段的移动，更易使链段规整排列，结晶加快，导致结晶速率常数增大;同时由于分子链没有充足时间更好地堆砌而使结晶完善程度减小，结晶能力下降。更多还原

【Abstract】 The thesis was focused on the crystalline of polymer and subject were crystallimity of film and crystallization kinetics. Research objects were poly(acrylic acid) and PEO, and analytic methods were X-ray diffraction(XRD) and differential scanning calorimetry(DSC). At first, the relation between the hydrophilicity and crystallim’ty of the film of poly(acrylic acid)(PAA) and its salts were investigated. Isothermal and non-isothermal crystallization kinetics of PEO and its blend system with lithium perchlorate were discussed.The solution of poly(acrylic acid)(PAA), poly(acrylic acid sodium)(PAANa), poly(acrylic acid lithium)(PAALi) were synthesized respectively. The paintings were coated on aluminium fins by roll film method in this article. The film with different crystallinity was obtained by varying baking time and temperature.The measurement of crystallinity of film was rarely reported. Based on the feasibility of surveying film crystallinity using XRD, crystallinity of the above film were tested by XRD. Contact angles for distilled water and glycerin on the film were measured at room temperature using a contact angle tester, with a droplet technique. Water and glycerin were dropped about 10 cm above film and contact angles were recorded within 30 seconds. Surface tension of film and the spreading speed constants were calculated according to the method in reference. The relation of the film hydrophilicity, crystallinity, surface tension and spreading speed constant was deeply discussed. The studies indicated that surface tension and spreading speed constant increased, equilibrium contact angle declined with crystallinity of film increasing, that is to say, the hydrophilicity of film were improved with crystallinity of film increasing.Isothermal and non-isothermal crystallization kinetics of PEO and blend system with lithium perchlorate at different annealing temperatures and different cooling rates have been investigated by using DSC. Theisothermal crystallinity process was analyzed using Avrami, Malkin methods and its kinetics parameters were obtained. The results indicated that PEO were of two-dimension growth with athermal nucleation. The value n of blending system having little differential to PEO indicated that the growth style of crystal were uniform except nucleation style. Each curve of pure PEO show an initial linear portion, then subsequently tend to level off. This fact indicated the existence of a secondary crystallization, which was caused by spherulite impingment in the later stage of crystallization process of PEO. Activation energy associated with the overall process of PEO and its blend sysytem have been evaluated from the rates of crystallization by using Cebe method, and results testified that pure PEO formed crystal easier in isothermal condition than blend system.DSC curves of non-isothermal crystallization indicated that the degree of secondary crystallization increased as cooling rates decreasing for PEO. For non-isothermal studies, Jeziorny and a method combined the Avrami and Ozawa equation were employed to describe the non-isothermal crystallization process as well, and the kinetics parameters n, Zc, f0.5, F(T) with specific physical meaning were determined. The activation energies were 149.68KJ/mol, 159.51 KJ/mol for non-isothermal crystallization by Kissinger method, respectively. It confirmed again that pure PEO could form crystal easier than its blend system under both isothermal and non-isothermal condition.更多还原