等规聚丙烯/豆油体系的非等温结晶动力学

采用差示扫描量热仪(DSC)对等规聚丙烯(iPP)与豆油体系的非等温结晶动力学进行了研究,并用扫描电子显微镜(SEM)观察了等规聚丙烯在豆油中的结晶形态．对实验数据用Ziabicki理论和Jeziorny方法进行处理,求出结晶动力学指数、结晶速率常数和结晶能力等数据,分析了降温速率及iPP初始浓度等对结晶动力学参数的影响．     

成核剂对聚丙烯非等温结晶过程的影响

用DSC研究了IPP与25种成核剂样品的非等温结晶过程,发现降温速率β和成核剂种类对结晶温度T_c和结晶温度范围ΔT_c均有影响。有7种成核剂在不同β时均能使T_c明显升高和使ΔT_c增大,另有3种成核剂在β增大时效果明显,其余的对IPP的非等温结晶过程影响不大。个别成核剂使结晶曲线出现双峰,同时使结晶温度显著提高。     

纳米碳酸钙改性聚丙烯共聚物的非等温结晶动力学

用DSC手段考察了反应釜内原位共聚制备的含有成核剂及纳米碳酸钙的聚丙烯(PP)共聚物的非等温结晶行为。结果表明，成核剂使PP共聚物的结晶温度升高，结晶度降低，结晶速率略有提高。而纳米碳酸钙则大幅提高了PP共聚物的结晶温度和结晶速率，结晶度也增加了约10％。并采用Ozawa法和Caze法描述了非等温结晶动力学。     

蒙脱土填充聚丙烯的等温结晶动力学

用示差扫描量热法(DSC)研究蒙脱土对聚丙烯的等温结晶的影响，结果表明，蒙脱土对聚丙烯的结晶起到了异相成核的作用，提高了聚丙烯的结晶速率，结晶一半时的时间tl／2明显缩短，熔点升高，结晶度增大。用Avrami方程进行等温结晶动力学研究，参数n对结晶温度有依赖性，PP／Mont复合材料的k值随温度的升高而减小。     

羧酸盐类β晶成核剂与α晶成核剂的复合体系对等规聚丙烯成核结晶行为的影响

采用差示扫描量热(DSC)、广角X射线衍射(WAXD)以及力学性能分析等方式考察了两种α晶成核剂和一种羧酸盐类β晶成核剂复合后对等规聚丙烯(iPP)的结晶性能、晶型结构以及力学性能的影响。结果表明,α/β复合成核剂对聚丙烯的结晶峰值温度、晶型结构以及力学性能的影响都与复合体系中结晶峰值温度较高的单一成核剂相似,说明在α/β复合成核剂体系中,两种成核剂竞争成核,结晶峰值温度较高的成核剂在结晶过程中起主导地位,而结晶峰值温度较低的成核剂成核作用较小。     

成核PP注塑样品的非等温结晶行为与熔融特性

用DSC研究了两种成核剂成核PP的非等温结晶行为与熔融特性,致命伤中成核剂均使PP的降温结构温度提高,结晶峰半高宽变窄,结晶度与熔点略有提高,但结晶峰对称性变差,熔融峰半高宽加大,成核样品的结晶温度对冷却速率的依赖性较纯PP的小,根据过冷度和成核PP与纯PP的结晶温度之差,成核剂成核作用大小顺序为：A＞D。     

有机磷酸酯盐与羧酸盐复配成核剂对等规聚丙烯性能的影响

以2,2'-亚甲基-双-（4,6-二叔丁基苯基）磷酸钠 （NA-11）和双环[2,2,1]-庚烷-2,3-二羧酸钠 （NA-CA）2种成核剂进行复配,研究复配成核剂对等规聚丙烯（iPP）力学性能和结晶行为的影响。采用双螺杆挤出机为共混设备将成核剂与iPP共混,制备了NA-11/NA-CA/iPP复合材料。通过万能材料实验机、XRD、DSC、偏光显微镜（PLM）对其力学性能、结晶形态、微观结构进行了表征。结果表明:NA-11和NA-CA 2种成核剂复配能够显著提高iPP的拉伸性能和弯曲性能。NA-11和NA-CA复配成核剂诱导iPP形成α晶体。2种成核剂1∶1复配,添加量为0.4wt%时,iPP的结晶峰温度提高了20.3 ℃,结晶度提高了8.8%。PLM显示,NA-11和NA-CA复配成核剂使iPP球晶尺寸明显变小。NA-11和NA-CA复配成核剂具有很好的成核效果,这2种成核剂对改善聚丙烯的结晶性能和力学性能具有协同效应。      

r-PTFE对PBT非等温结晶动力学的影响

以回收聚四氟乙烯(r-PTFE)为成核剂,对聚对苯二甲酸丁二醇酯(BPT)进行成核结晶改性,采用差示扫描量热仪(DSC)研究了PBT/r-PTFE复合材料的非等温结晶行为,考察了不同降温速率对PBT/r-PTFE共混物结晶行为的影响,并对其DSC扫描数据采用Jeziorny法和Liu-Mo法进行处理,采用Kissiinger法计算体系结晶活化能。结果表明:r-PTFE对PBT具有异相成核作用,可明显提高PBT的结晶度及其结晶速率,且加入r-PTFE并不会改变PBT的成核和增长方式。由Kissinger法计算得出的结晶活化能结果表明,加入r-PTFE树脂能够明显降低PBT的结晶活化能,进一步验证r-PTFE对PBT具有成核促进作用。     

取代芳基杂环磷酸盐类成核剂改性聚丙烯的等温结晶研究

采用差示扫描量热法(DSC)对取代芳基杂环磷酸盐类成核剂改性聚丙烯的等温结晶过程及结晶动力学进行了研究.结果表明取代芳基杂环磷酸的一价金属盐成核剂的加入可大幅度缩短聚丙烯的半结晶时间t1/2,加快聚丙烯的结晶速度,而二价和三价的金属盐对聚丙烯结晶速度的改善不明显.对于iPP及成核iPP,其Avrami指数基本都在3左右,表明在等温条件下成核剂的加入对聚丙烯的结晶方式影响不大.同时采用Hoffman理论计算了聚丙烯和成核聚丙烯球晶生长的单位面积折叠表面自由能σe,结果表明取代芳基杂环磷酸一价金属盐的加入可显著降低聚丙烯的σe,而二价和三价的金属盐对σe的影响不明显.     

加成核剂聚丙烯的非等温结晶形态

研究了ＩＰＰ及其加２５种成核剂时的非等结晶形态，考查了成核剂和线性降温速率ａ对球晶尺寸ｄ的影响。发现纯ＩＰＰ的ｄ随ａ增大线性降低；接随ａ增大ｄ的变化，成核剂可分为３类：ｄ变化不大，均得大球晶；ｄ变化不大，均得小球晶，ｄ明显减小。     

混合稀释剂对热致相分离法制备等规聚丙烯微孔膜的影响

以邻苯二甲酸二丁酯(DBP)和大豆油混合物为稀释剂,利用热致相分离(ThermallyInduced Phase Separation,TIPS)法制备了等规聚丙烯(iPP)微孔膜.结果表明,稀释剂体系中DBP和大豆油的质量比对浊点温度影响较大,而对结晶温度影响较小;随着稀释剂体系中DBP含量的增加,在固定聚合物浓度及相同的冷却条件下,多孔膜由空间网状结构逐渐转变为腔胞状结构,表面孔径也有明显的增大趋势;稀释剂的加入降低了iPP球晶的生长速率,其组成对iPP球晶生长速率也有一定影响.     

Vibration-dependent morphology and crystal structure of isotactic polypropylene

A small homemade device was used to study the influence of mechanical vibration on the crystal structure and morphology of isotactic polypropylene (iPP) under different melting temperatures, vibration times, vibration frequencies, and cooling rates. The crystallite size, crystal structure, and crystallinity of iPP under or without vibration treatment were investigated by means of differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and polarized microscopy observation (PLM). The crystallization of iPP varied with the length of vibration time, vibration frequency, cooling rate, and melt temperature. Compared with the data of conventional samples measured by DSC, vibration could increase the crystallinity of iPP, make melting peak of α-crystal move toward higher temperature and make that of β-crystal shift to lower temperature. Meanwhile, WAXD measurements showed that the vibration could reduce the content of β-crystal evidently, particularly at the lower vibration frequency, lower cooling rate, and higher melting temperature. Furthermore, PLM measurements showed that the vibration made the spherulite size smaller.     

正交实验设计方法优化膜蒸馏用聚丙烯平板疏水微孔膜的制备条件

采用热致相分离方法制备了膜孔径分布为0.02~0.1μm的聚丙烯平板疏水微孔膜.用正交实验设计方法对聚丙烯平板膜的制备方法进行优化设计.在正交实验设计条件下,以纯水和浓度为0.5 mol/L的NaCl水溶液真空膜蒸馏实验特性,确定了聚丙烯平板疏水微孔膜优化制备条件.在研究范围内,此优化制备条件为:稀释剂为豆油、iPP(质量分数)为27%、等规聚丙烯(iPP)熔融指数(MI)为16.08 g/10 min、淬冷温度为20℃、成核剂己二酸含量(质量分数)为0.5%、萃取剂为正己烷、铸膜液温度为190℃、刮板温度为210℃.     

降冰片烯二羧酸盐类成核剂在等规聚丙烯中的成核效应

应用DSC考察了降冰片烯二羧酸盐对等规聚丙烯结晶和熔融行为的影响。结果表明,降冰片烯二羧酸盐的加入提高了聚丙烯的结晶温度和熔融温度。其中钠盐(BCHE11)和钙盐(BCHE20)成核效果较为显著,添加质量分数在0.2%时可使聚丙烯的结晶峰值温度提高10.8℃和9.4℃。应用Avrami方法对降冰片烯二羧酸盐成核的聚丙烯等温结晶动力学进行了研究,结果表明,成核聚丙烯半结晶时间都小于空白聚丙烯,尤其是BCHE11和BCHE20。成核聚丙烯的Avrami指数n都在3左右,这表明成核聚丙烯的结晶生长方式为异相成核的三维球晶生长方式。     

等规聚丙烯注塑成型冷却固化分子机制研究

针对等规聚丙烯(iPP)在注塑成型冷却过程中的液-固相变与大分子形构问题,采用分子模拟实验的方法,研究了iPP材料在注塑冷却过程中的分子固化与形态演化的分子机制。建立了聚合度依次为24、36、51、72、120,链数为36、24和16的iPP胞元体系,基于Smart Minimizer与SA算法实现了能量初始化;基于周期性边界并引入COMPASS力场及Velocity-Verlet算法,实现了体系冷却固化过程的分子模拟实验。结果表明:不同模拟体系的T_g结果符合Flory自由体积理论;固化前后iPP大分子链主链键长、键角等结构参数均呈高斯分布,温度越低键长与键角分布越集中,符合无外力加载条件下的缠结大分子链的冷却松弛过程;〈h〉和〈R_g〉均随聚合度的增大而增大,降温过程中〈h〉呈高斯分布状态,而〈R_g〉分布趋于集中,一方面表明冷却固化过程中大分子链由初始取向排布逐步恢复至缠结状态,另一方面体现了固化结晶过程;材料聚合度越大,降温过程中分子迁移或固化速率越小,且当温度高于T_g时,聚合度越小,降温过程体系扩散系数下降梯度越大,而温度下降至T_g以下则无明显规律。     

Preparation and characterization of wollastonite with a β-nucleating surface and its filled isotactic polypropylene composites

To transform α-nucleation into β-nucleation of wollastonite surface for isotactic polypropylene (iPP), the wollastonite with a β-nucleating surface was prepared through the chemical reaction between wollastonite and pimelic acid in both liquid mixing (method A) and powder mixing (method B). The wollastonite with a β-nucleating surface was confirmed using differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy analysis, wide-angle X-ray diffraction under different temperatures, thermogravimetry coupled with Fourier transform infrared spectrometry, and scanning electron microscopy. The crystallization and melting behavior and the crystalline morphology of iPP composites filled by wollastonite with a β-nucleating surface were investigated by DSC and optical microscopy. The results indicated that wollastonite filled iPP composites predominantly crystallize in the α-phase iPP and iPP composites filled by wollastonite with a β-nucleating surface mainly form β-phase iPP. It is proved that heterogeneous nucleating mechanism has been changed from α-nucleation into β-nucleation of wollastonite surface for iPP crystallization. What deserves to be mentioned is that the nucleation density of flat surface in the end of needle-like wollastonite is higher than that of curved surface of wollastonite.     

Design and properties of a novel nucleating agent for isotactic polypropylene

Three new nucleating agents TB, TD and TSD (titanate of benzoate or 4-tert-Butylbenzoate) were prepared. Isotactic polypropylene (iPP) nucleated were studied by using thermogravimetry analysis (TGA), X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The mechanical properties and Vicat softening temperature (VST) of iPP were also tested. The results indicated that these three nucleating agents were very effective in increasing the crystallization temperature (T_c) and crystallinity (X_c) of iPP. Mechanical properties of nucleated iPP were improved remarkably, especially nucleating agent TSD.