高聚物非等温结晶过程的Monte Carlo法模拟

【作者】 董知之；

【导师】 张志英；

【作者基本信息】 天津工业大学 ， 材料学， 2004， 硕士

【摘要】 本文采用计算机模拟的方法,模拟了高聚物非等温结晶的过程,并根据模拟实验的结果,分别用Ozawa方程、改进的Ozawa方程、Jeziorny法、Ozawa方程和Avrami方程相结合的方法及等转化率法对数据进行了处理,从而对以上方程和方法的适用性进行了评价,得到了相应的结论。 首先建立高聚物非等温结晶过程的数学模型,模拟出高聚物在非等温结晶过程中相对结晶度随时间变化的曲线,并与DSC实验的结果进行对比,通过不断调整初值,模拟出与DSC实验相近的结晶曲线,从而确定了体系的起始结晶温度和晶核数目。 对模拟实验的数据用Ozawa方程处理,求出的Avrami指数n值稍低于理论值3,用改进的Ozawa方程处理,求出的线生长速率G与理论计算出的线生长速率基本吻合,但随着温度的降低,会出现实验值与理论值偏离的现象。用Jeziorny法处理实验数据,得到的Avrami指数n值远远超过理论值3,求出的结晶速率常数Z_c也不为一常数。用等转化率法处理实验数据,获得的结晶速率常数K,结晶活化能E_d,成核参数ψ等值,与计算机模拟实验所采用的理论值相近,但得到的线生长速率G值与计算机模拟实验所采用的G值相差很大,模拟实验采用的G值约为10^-1,而用等转化率法得到的G值均在10^-4。 数据处理结果表明,在预先成核、晶核无规分布的条件下,用Ozawa方程及改进的Ozawa方程解析结晶动力学参数是适用的;而用Jeziorny法描述高聚物非等温结晶过程时误差较大;用等转化率法适用于解析结晶速率常数K,结晶活化能E_d,成核参数ψ等参数,但不适用于求解线生长速率G。更多还原

【Abstract】 The non-isothermal crystallization process of polymer was simulated by using the Monte Carlo method. The results of the simulating experiment were analyzed by using the Ozawa equation, the modified Ozawa equation, the Jeziorny method, method of the combination of the Ozawa equation and the Avrami equation, and the iso-conversional method. The application of previous equation and the method were evaluated, and the conclusions were obtained respectively.Firstly, the computer simulating model of non-isothermal crystallization of polymer was established. The curves of the degree of crystallinity versus time were obtained. And compared with the results of DSC. By adjusting the starting value, the crystallinity curve obtained was close to the experimental one. So the initial temperature and the numbers of nuclei were confirmed by the previous method.The results of the simulating experiment were analyzed by using the Ozawa equation. The obtained values of the Avrami exponent n were smaller than 3. The linear growth rate obtained by the modified Ozawa method was in agreement with the real linear growth rate. However, with the decreasing of the temperature, the values of the experiment one were departed from the values of the theory one. The values of Avrami exponent n obtained by the Jeziomy method were far larger than 3 and the crystallization rate constant didn’t remain a constant. The crystallization rate constant K, the activation energy of crystallizing Ed, the nucleation parameter ψ obtained by the iso-conversional method was close to the real ones. But there was a discrepancy in the value of the liner growth rate G. G adopted in the simulating experiment was about 10^-1, whereas the G obtained by the iso-conversional method were all at 10^-4.It was shown that under condition of the predetermined nucleation and the irregular distribution of the nuclei, the Ozawa equation and the modified Ozawa equation were applicable in obtaining the kinetics parameters. It was shown that the Jeziomy method was unsuitable on the non-isothermal crystallization of polymers. The iso-conversional method was suitable to analyze at the crystallization rate constant K, the activation energy of crystallizing Ed, the nucleation parameter ψ, and was unsuitable to analyze the liner growth rate G.更多还原