赤泥改性PP复合材料制备及结晶性能与力学性能研究

采用赤泥作为无机填料,添加到聚丙烯(PP)中,制备出赤泥/PP复合材料。实验分别采用FTIR、DSC、PLM及力学性能测试仪器研究了改性前后赤泥的结构及对PP的熔融结晶性能和力学性能的影响。结果表明,赤泥的加入提高了PP的结晶温度和结晶速率,PP晶体尺寸细化。赤泥具有明显的异相成核作用,经表面修饰的赤泥(TRM)异相成核效果降低。当TRM含量为15%时,TRM/PP复合材料的冲击性能最佳,随着赤泥的含量的增加,复合材料弯曲强度逐渐提高。     

己二酸/无水硫酸钙晶须改性PP的等温结晶动力学

通过差示扫描量热(DSC)仪分析了己二酸(AA)和无水硫酸钙晶须(ACSW)复配改性聚丙烯(PP)的等温结晶行为,用偏光显微镜(PLM)观察了AA/ACSW复配改性PP的晶体形貌。DSC分析结果表明,随着结晶温度升高,半结晶时间和最大结晶时间增加,半结晶速率降低;与纯PP相比,ACSW和AA/ACSW复合改性都能使PP的结晶时间降低,结晶效率增加,说明ACSW和AA/ACSW对PP具有异相成核作用,并且AA/ACSW复合改性PP对提高PP的结晶性能有更好的效果,此外ACSW改性PP的等温结晶活化能最低。对改性PP的PLM的观察说明ACSW对PP具有异相成核作用,而AA/ACSW对PP的β晶成核具有协同促进作用。     

改性高岭土/聚丙烯复合材料的热性能及非等温结晶行为研究

以自制的剥离高岭(MK)、原高岭土(K)以及聚丙烯(PP)和马来酸酐接枝聚丙烯(PP-g-MA)等作为基本原料,通过熔融挤出、注塑成型,制备PP复合材料。采用XRD、DSC、TG研究复合材料的非等温结晶行为、结晶动力学以及热降解性能。结果表明:高岭土的加入,使结晶温度、结晶度、热稳定性都有所提高,且结晶速率加快,具有异相成核作用。与原高岭土相比,改性高岭土更能促进PP复合材料的PP异相成核,促进PP稳态晶型(α晶型)的转变,结晶速率较快。与纯PP和PP/PP-g-MA复合材料相比,PP/改性高岭土复合材料的结晶峰温度、最大热降解温度分别提高了16.7、7.8、9.7、12.6℃。     

滑石粉、碳酸钙填充聚丙烯复合材料等温结晶行为的对比研究

用熔融共混法分别制备了聚丙烯（PP）/滑石粉、PP/碳酸钙(CaCO3)复合材料,用差示扫描量热法(DSC)考察了PP及其复合材料的等温结晶过程,并用Avrami方程对纯PP及PP/滑石粉、PP/CaCO3复合材料的等温结晶动力学行为进行了分析。结果表明,PP、PP/滑石粉及PP/CaCO3复合材料的Avrami指数均小于2.3,存在均相成核和异相成核双重成核机理,且其结晶速率常数和结晶速率均随着结晶温度的升高而减小;在该体系中,滑石粉对基体PP有明显的异相成核作用,使PP的结晶速率加快、结晶时间缩短;而CaCO3则没有明显的异相成核作用。     

聚丙烯/聚磷酸铵复合材料的等温结晶行为

采用差示扫描量热法研究了聚丙烯(PP)聚/磷酸铵(APP)复合材料的等温结晶过程。引入APP后,PP/APP复合材料的平衡熔点升高,结晶速率大幅度提高。采用Avrami方程研究了该体系的结晶动力学,发现PP/APP复合材料呈现明显的异相成核特征,随w(APP)的增加,Avrami结晶速率常数增大,半结晶时间降低。     

柠檬石膏聚丙烯复合材料的非等温动力学

采用差示扫描量热(DSC)法研究了柠檬石膏/聚丙烯(PP)复合材料的非等温结晶动力学,对所得的数据采用的是修正Avrami方程的Jeziorny法和Mo法进行处理。结果表明:柠檬石膏的加入提高了PP的结晶温度Tp和结晶速率,同时降低了结晶活化能ΔE,使PP结晶更容易,未表面处理的柠檬石膏使结晶活化能ΔE下降最多,经过偶联剂表面处理的柠檬石膏使结晶活化能ΔE有小幅上升。结果还表明柠檬石膏有明显的异相成核的作用。     

聚丙烯／滑石粉复合材料的等温结晶动力学

用差示扫描量热法(DSC)研究聚丙烯(PP)及PP／滑石粉复合材料的等温结晶过程。用Avrami方程全面分析PP／滑石粉的等温结晶动力学，并由此获得相关的动力学参数；用Kissinger方程研究滑石粉对PP／滑石粉复合材料结晶活化能的影响。研究表明：加入滑石粉后明显提高PP／滑石粉复合材料的结晶速率和结晶度；证明滑石粉能促进PP材料的结晶，并在PP结晶过程中起到异相成核作用。PP／滑石粉复合材料的等温结晶过程属于典型的异相成核机理。     

增容剂对PP/r-PET共混物非等温结晶动力学的影响

采用差示扫描量热法研究了增容剂甲基丙烯酸缩水甘油酯接枝聚丙烯(PP-g-GMA)对聚丙烯(PP)/回收聚对苯二甲酸乙二酯(r-PET)共混物的非等温结晶动力学的影响。结果表明:在PP/r-PET共混体系中,r-PET起到异相成核的作用,PP的结晶峰温升高,半结晶时间减少;增容剂PP-g-GMA的加入使PP/r-PET的结晶温度降低,半结晶时间增大,但降低了PP的结晶活化能。     

废旧丁腈橡胶粉/聚丙烯复合材料的非等温结晶行为

采用熔融共混法制备了废旧丁腈橡胶粉/聚丙烯(WNBR/PP)和废旧丁腈橡胶粉/聚丙烯接枝马来酸酐/聚丙烯(WNBR/PP-g-MAH/PP)复合材料,采用差示扫描量热仪研究了PP、WNBR/PP及WNBR/PP-g-MAH/PP复合材料的非等温结晶过程,并通过Jeziorny方程研究了复合材料的非等温结晶动力学。结果表明,随降温速率的增大,所有试样的结晶峰温和结晶起始温度均向低温偏移,结晶度减小,结晶速率增大。WNBR能起到异相成核的作用,提高了PP的结晶速率,并且导致PP结晶成核和生长机理发生改变。     

聚丙烯/Mg2B2O5晶须复合材料的非等温结晶动力学研究

采用熔融共混法制备了Mg2B2O5晶须(MBOw)和经硼酸酯偶联剂(BE)改性后MBOw分别填充的聚丙烯(PP)基复合材料,通过光学显微镜分析研究了BE对MBOw表面性质的影响,用DSC法并结合莫志深方程研究了PP及其填充改性前后MBOw复合材料的非等温结晶动力学。结果表明,BE改性后的MBOw表面性质较改性前发生根本变化;莫志深方程能较好地描述PP及其复合材料的非等温结晶动力学,MBOw对PP具有异相成核的作用,加快了PP的结晶速率,且BE使MBOw的异相成核能力得到增强,更有利于PP结晶速率的提高。     

DPL—Ⅱ结晶速度仪在高聚物中的应用

介绍了采用基于解偏振光强度方法，热平衡时间很短的ＤＰＬ－Ⅱ结晶速度仪，分别测定了ＰＥＴ、ＰＰ、ＰＥ等在不同温度下等温结晶过程及等速升温条件下的晶体熔化过程，并解析出诱导期，结晶速率，结晶过程机理，Ａｖｒａｍｉ指数，ｎ、ｋ及熔点。     

Recent advances in the monitoring,modelling and control of crystallization systems

Crystallization is one of the most important unit operations used for the separation and purification of crystalline solid products. Appropriate design and control of the crystallization process is paramount to produce crystalline products with tailor-made-properties. This paper provides an overview of selected recent developments in the modelling, monitoring and control of crystallization processes. We consider the topics discussed in this review to be enabling technologies for the development of the next generation of crystallization processes with significantly improved predictability, robustness and controllability.     

Modeling Growth Rate Dispersion in Industrial Crystallizers

The phenomenon of healing appears to be a plausible explanation for the growth rate dispersion observed in many industrial crystallizers. In this paper a growth model is postulated, which describes the healing of plastically deformed attrition fragments. The rate of healing is assumed to be inversely proportional to the initial strain and to the rate of change of either the length, the area, or the volume of the crystal. The validity of the proposed model is verified by the simulation of growth of the smallest crystals (L₀) in time in a growth experiment for specific combinations of the model parameters. In addition, the applicability of the proposed model is evaluated through simulations of steady state experimental data obtained in a 75‐liter Draft Tube (DT) crystallizer. It is concluded that the proposed model is able to fit reasonably well the experimental crystal size distribution. The model predicts the existence of a ‘dead time’ during which attrition fragments with large initial strain do not grow and which may last several residence times.     

新型β成核剂NA对聚丙烯等温结晶行为的影响

合成了一种新型酰胺类β成核剂NA,该成核剂能明显提高聚丙烯的结晶速率,促进聚丙烯结晶。利用广角X射线衍射仪(WXRD)、差示扫描量热仪(DSC)和偏光显微镜(POM)研究了成核剂NA对聚丙烯结晶性能和结晶形态的影响。结果表明,当成核剂质量分数为0.5%时,β晶的相对含量为46.3%。Avrami方程研究表明,聚丙烯复合材料呈现明显的异相成核特征。     

聚丙烯/蒙脱土纳米复合材料的结晶性能研究

采用差示扫描量热法研究蒙脱土(MMT)对聚丙烯(PP)等温结晶性能的影响。结果表明：加入MMT后提高了PP的结晶速率，使结晶度增大，但对PP熔点的影响不大；加入相容剂PP-g-MAH后，使有机MMT对PP的成核作用更加明显，从而提高了PP／MMT。纳米复合材料的结晶度；PP／MMT纳米复合材料的n值在3左右，其成核方式是异相成核方式。     

聚合物型成核剂对HDPE结晶行为的影响

以丙烯酰氯、对羟基苯甲酸和对羟基苯甲醚为原料，采用酰化反应制备了一种乙烯基单体，并采用自由基聚合反应合成出聚合物型成核剂聚4-甲氧基-4′-丙烯酰氧苯甲酸苯酯(PMAPAB)；研究了PMAPAB对高密度聚乙烯(HDPE)结晶和熔融行为以及晶体形态的影响，并分析了HDPE的非等温结晶行为。结果表明：该聚合物用量为0．25％，1．5％时，均能促进HDPE的结晶，提高HDPE的结晶速率及结晶度，降低其晶粒的尺寸并使其分布更为均匀，当PMAPAB用量为0．25％时，能达到最佳的成核效果。     

Crystallization of alkaline protease as a means of purification process

A purification protocol of alkaline protease purification using crystallization was developed by investigating the effects of pH, temperature, initial enzyme concentration, salt (as crystal inducer) concentration, and the presence of impurity proteins. A commercial alkaline protease solution was used as a starting material and NaCl was used as a crystal inducing salt. The crude enzyme solution was first diafiltered against deionized water and then concentrated by ultrafiltration. To the enzyme concentrate appropriate amount of NaCl was added to induce the crystallization which was lasted for 24 hours, and the enzyme crystals formed were filtered and washed with deionized water before being resolubilized. Crystal habit was typical needle shape, and the reaction order of its formation was estimated to be 1.53. The crystallization was strongly influenced by initial enzyme concentration. Solubility of alkaline protease at 25°C was 24.8 mg/ml, which was about one half of that of 4°C. Enzyme recovery yield of the purification process including the crystallization step ranged 50 to 60 %. The crystallization step was shown to successfully exclude impurity proteins from their habits as evidenced by gel permeation chromatography. The optimum condition for the crystallization was: pH 9.0, 25°C temperature, ca. 53 mg/ml or higher enzyme concentration, and minimum 5 % (w/w) NaCl concentration. In summary, an enzyme purification protocol based on crystallization was established, which can be applied to obtain a higher-purity alkaline protease solution on a large scale.