新型复合成核剂对PP/POE共混物结晶行为的影响

以低分子量聚酰胺6为主体制备了新型复合成核剂,采用高级流变仪、差示扫描量热仪、偏光显微镜等分析手段研究了几种成核剂对聚丙烯/乙烯-1-辛烯共聚物(PP/POE)共混物结晶温度、结晶形态及流变行为的影响。结果表明:新型复合成核剂均可以提高PP/POE共混物的结晶温度、结晶度和结晶速率,减小共混物的球晶尺寸,增加晶核密度,显著提高了PP/POE共混物的结晶性能。     

增容剂对PP/PA66共混物力学性能和结晶行为的影响

采用熔融共混法制备了聚丙烯(PP)/聚酰胺66(PA66)共混物,研究了聚丙烯接枝马来酸酐(PP-g-MAH)和乙烯-辛烯共聚物接枝马来酸酐(POE-g-MAH)作为增容剂对PP/PA66共混物力学性能和非等温结晶行为的影响。结果表明:PP-g-MAH提高了共混体系的拉伸强度,加入5份POE-g-MAH能显著提高共混物的断裂伸长率;PA66可起到异相成核作用,使PP的结晶峰温度升高;加入PP-g-MAH进一步提高了PP的结晶峰温度;PA66使PP的结晶活化能增大,增容剂的加入则使共混体系中PP的结晶活化能降低。     

回收PET共混物的非等温结晶和熔融行为

采用双螺杆挤出机制备了聚丙烯(PP)/回收聚对苯二甲酸乙二酯(r-PET)、r-PET/马来酸酐接枝PP(PP-g-MAH)和r-PET/甲基丙烯酸缩水甘油酯接枝PP(PP-g-GMA)共混物,并研究了共混物组成、熔融温度与时间以及降温速率对共混物非等温结晶与熔融行为的影响.结果表明,r-PET与PP共混,结晶温度均提高,这与组分间起到异相成核诱导结晶作用有关.r-PET结晶温度随PP-g-MAH用量增加而降低,但受PP-g-GMA用量影响较小;r-PET可提高PP-g-MAH结晶温度,但降低PP-g-GMA结晶温度.熔融温度提高,共混物中PP结晶温度和熔点均降低,r-PET熔融峰形和熔点取决于共混物的熔融温度及界面相互作用.     

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。     

聚丙烯／间同1，2-聚丁二烯共混物的等温结晶动力学

利用Avrami方程研究了聚丙烯（PP）及PP／间同1，2-聚T2烯（s—PB）共混物的等温结晶动力学。DSC研究表明：在相同的结晶温度下，如128℃时共混物的结晶速率为0．45min^-1，比纯PP的0．17min^-1大，s-PB起到了成核剂的作用，使共混物的结晶速率加快；共混物的Avrami指数n为2．71～323，共混物的结晶主要是以三维方式增长、异相成核。共混物的Arrhenius结晶活化能为309．35kJ·mol^-1比纯PP的338．11kJ·mol^-1低，结晶活化能的降低也证明了s-PB在共混物的结晶过程中起到了成核剂的作用并使结晶速率加快。     

PET/PP共混体系的熔融及非等温结晶行为

用熔融共混法制备了聚对苯二甲酸乙二醇酯(PET)/聚丙烯(PP)复合材料。对复合体系的形态结构、熔融及非等温结晶行为进行了研究。结果表明:两相界面或PP相对PET结晶无明显的异相成核效应;当PP为连续相时,已结晶的极性PET粒子对PP的异相成核作用较为明显;而当PP为分散相时,固态的PET在一定程度上阻碍了PP分子链的运动,促使PP结晶均相成核趋势增加。与纯PET或PP相比,共混体系中两组分结晶的完善程度都有所下降。     

马来酸酐化增容剂对PP/PET共混物性能的影响

采用熔融共混法制备了聚丙烯(PP)/聚对苯二甲酸乙二酯(PET)共混物,研究了马来酸酐接枝聚丙烯(PP-g-MAH)和马来酸酐接枝乙烯/辛烯共聚物(POE-g-MAH)作为增容剂对共混物力学性能和非等温结晶行为的影响。结果表明:PP-g-MAH提高了共混体系的拉伸强度,加入POE-g-MAH则显著提高共混物的断裂伸长率;当PP∶PET∶增容剂质量比为80∶20∶5时,共混体系的力学性能较好;PET起到异相成核的作用,使PP的结晶峰温升高,半结晶时间缩短;加入增容剂,使PP的结晶峰温降低,半结晶时间延长。     

增容剂对PP/PET原位微纤化共混物的影响

通过"熔融挤出-热拉伸-淬冷"的方法制备了原位微纤化共混物。采用扫描电镜、差示扫描量热仪和力学性能测试等方法研究了增容剂PP-g-GMA含量对共混物微观形态、力学性能和结晶性能的影响。结果表明,增容剂的加入可明显提高两相相容性,改善界面效果,明显降低拉伸前初始粒子的尺寸,但同时使拉伸后形成的微纤呈现一定的损坏,长径比有所降低。增容剂可以明显改善微纤化共混物力学性能,当其含量为2 %（质量分数,下同）时拉伸强度比未增容试样提高了11.0 %,弯曲强度都提高了11.3 %;当其含量为6 %时冲击强度也比未增容共混物提高了34.5 %。此外,PET微纤对PP有很好的异相成核作用,使其结晶温度提高了16.3 ℃,结晶时间为纯PP的32 %左右,而增容剂的加入使共混物中PP的结晶时间延长。     

PP/PP-g-MAH/EVOH共混物流变和结晶行为研究

采用马来酸酐接枝聚丙烯(PP-g-MAH)为相容剂,增容聚丙烯/乙烯-乙烯醇共聚物(PP/EVOH)共混体系。利用旋转流变仪研究PP-g-MAH含量对PP/PP-g-MAH/EVOH共混物流变和结晶行为影响。结果表明:随着PP-g-MAH含量的增加,PP/PP-g-MAH/EVOH共混物体系相容性逐渐改善,黏度、储能模量与损耗模量均先增加后减小。此外,随着PP-g-MAH含量的增加,PP/PP-g-MAH/EVOH共混物中PP相的成核温度(T_b)和生长温度(T_c)也逐渐向低温方向偏移,同时PP晶体后期成核速率和晶体长大速率逐渐减小。     

PET纤维对聚丙烯结晶行为与力学性能的影响

以聚丙烯(PP)、聚酯(PET)纤维为主要原料,马来酸酐接枝PP(PP-g-MA)为相容剂,经熔融共混、粉碎、注塑加工成样条后进行表征,并研究了其性能。结果表明:PET纤维对PP具有异相成核作用,主要诱导PP形成α晶,可提高PP结晶温度并降低球晶尺寸;PET纤维可显著提高PP的拉伸强度和弹性模量,但会降低其冲击强度;加入相容剂PP-g-MA对PP/PET纤维共混物的结晶性能基本无影响,但对其力学性能影响显著,与未增容的PP/PET纤维共混物相比,经PP-g-MA增容后,共混物的拉伸强度、冲击强度、弹性模量均得到显著提升。     

Effects of vibration blending on the subsequent crystallization behavior of polycarbonate/polypropylene blends

The effects of blending in a novel vibration internal mixer on the subsequent multiple crystallization of 70/30 w/w polycarbonate (PC)/polypropylene (PP) were investigated by differential scanning calorimetry, wide‐angle X‐ray diffractogram, and microscopy. The vibration internal mixer was reformed from a conventional internal mixer through parallel superposition of an oscillatory shear on a steady shear. For this polypropylene‐minor phase blend, three possible crystallization peaks were observed. The crystallization behavior was sensitive to the sizes and the size distribution of the dispersed polypropylene droplets. Larger amplitude and/or higher‐frequency vibration produced more small droplets (<2 μm) and increased the number of medium droplets (2–8 μm) as a result of the spatially wider and temporally quicker variation of shear rate. The resulting subsequent low‐temperature crystallization peak became larger and shifted to lower temperature, and the intermediate‐temperature peak became obvious. On the contrary, the coalescence of small droplets, resulting from the heating treatment, weakened the low‐temperature peak but strengthened the intermediate‐temperature peak and rendered the high‐temperature peak to be wider. Mixing at the too high amplitude produced the unstable, partially cocontinuous phase morphology restricting the medium droplets and enlarging the surface area, such that the intermediate‐temperature crystallization peak did not appear. Multiple crystallization was related to phase morphology and the nucleation density as well as surface effects. Double‐fusion endotherms of the PP component were also observed, corresponding to the melting of different forms of polypropylene crystals. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 92–103, 2002     

The effects of melt vibration blending on the subsequent crystallization and melting behavior of polypropylene/ultra high molecular weight polyethylene

Pure isotactic polypropylene (iPP) and 90/10 wt iPP/ultra high molecular weight polyethylene (UHMWPE) blends, prepared by a novel vibration internal mixer reformed from a coventional internal mixer via parallel superposition of an oscillatory shear on a steady shear, were investigated by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction. After plasticating pure iPP in the vibration field, the number of β form crystals of iPP was increased. The β form exhibited a single DSC melting peak different from that of the bulk α form crystals of iPP. After mixing of UHMWPE with iPP, the melting point of the UHMWPE component shifted to a lower temperature. For blends mixed at the higher‐frequency and/or larger‐amplitude vibrations, the melting point of the UHMWPE component was further gently lowered while the bulk melting point of the iPP component was slightly increased. The crystallization peaks of the two components overlapped into one single peak, and the total crystallinity became higher, together with a larger amount of the β iPP. These results showed that the two components influenced each other in blending. Hence, the resultant morphology affected the subsequent crystallization and melting behaviors. Additionally, vibration in mixing possibly affected the conformation of some polypropylene chains to favor the subsequent packing in the β form.     

Development of dispersed phase size and its dependence on processing parameters

Through measurement of phase dimension via laser scattering, phase morphology development in immiscible blends of polyamide 12/poly(ethylene glycol) (PEG) with an extremely high viscosity ratio was investigated. The blends were prepared by melt blending in a batch mixer. The objective was to examine the influence of mixing time, rotor speed, as well as blending temperature on the size distribution of the minor phase. It is of interest that the breakup process of the dispersed PA 12 phase was observed for the blend systems even for extremely high viscosity ratios of ≤ 10²–10³. Mixing time had a significant effect on the development of dispersed phase size distribution. It was found that the bulk of particle size reduction took place very early in the mixing process, and very small droplets with a diameter of 0.1–10 μm were produced. The number of small particles then decreased, resulting in a larger average particle size. With further prolonged mixing, the particle size levels off. The particle size and its distribution were also found to be sensitive to the rotor speed. The average particle size decreased with increased rotor speed. The effect of blending temperature on size and size distribution, which has seldom been studied, was also examined in this work. When the blending temperature altered from 190°C to 220°C, the size and its distribution of the dispersed phase varied considerably, and the change of viscosity ratio was found to be the key factor affecting the dispersed phase size. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3201–3211, 2006     

碳纳米管/聚丙烯复合材料的制备与研究

在制备碳纳米管/聚丙烯复合材料的过程当中,碳纳米管难以均匀的分散在聚丙烯基体中。要解决碳纳米管的分散性就需要对碳纳米管进行必要的修饰。基于此背景,本论文首先对碳纳米管进行了表面修饰,然后选择马来酸酐接枝聚丙烯（MAH-PP）作为聚合物基体,制备了碳纳米管/聚丙烯复合材料,研究了碳纳米管/聚丙烯复合材料的结晶行为。碳纳米管在聚丙烯复合材料中能起到异相成核作用,促使晶粒细化。     

Quantitative evaluation of fractionated and homogeneous nucleation of polydisperse distributions of water-dispersed maleic anhydride-grafted-polypropylene micro- and nano-sized droplets

The nucleation processes in waterborne Maleic Anhydride-grafted-Polypropylene micro- and nano-droplet suspensions have been studied. Compared to a previous report on this topic, an extended set of samples in combination with improved particle size distribution data of the samples have been used, which are both essential for the advancement of the analysis.Self-nucleation was utilized to ensure that the observed lowered fractionated crystallization (peak) temperatures – down to the extremely low value of 34 °C – are due to a lack of seeds in the droplets, which seeds for the polypropylene system used are normally active at the heterogeneous crystallization temperature of approximately 110 °C. An unusual self-nucleation behavior was observed in case of samples having a large amount of small droplets, requiring an extremely low self-nucleation temperature in order to suppress all crystallization at the lowest temperatures. Such behavior was observed for block copolymers but has not been reported so far for droplets dispersed in an immiscible matrix, polymeric or not. Another unusual behavior was observed for some self-nucleation temperatures for which apparently two different populations of self-nuclei are created that are suggestive of the α₁ and α₂ crystal structures of isotactic polypropylene.Next, two new methods are presented to quantify various crucial parameters of the nucleation process: one estimates the density of nucleants acting at different temperatures from the combination of dynamic DSC data and particle size distribution (PSD) data, and the other one focuses on the nature of the nucleation mechanism using both isothermal DSC data and PSD data, quantifying the nucleation rate at different temperatures. For the present MA-g-PP dispersions the latter method leads to the conclusion that the lowest crystallization temperatures reflect sporadic nucleation, probably by way of volume (homogeneous) nucleation.In the field of polymer crystallization, polymer dispersions are usually treated as being monodisperse, even though that is rarely the case. This simplification is inadequate for the present calculations, which is why polydispersity has been taken into account in order to quantify the density of nucleants and the kinetics of nucleation. Though in the present study DSC data are used for the calculations, the methods developed can be easily adapted to other techniques like time-resolved X-ray, rheometry and dilatometry.     

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℃。     

Characterization of carbon nanotube- and organoclay-filled polypropylene/poly(butylene succinate) blend-based nanocomposites with enhanced rigidity and electrical conductivity

In this study, immiscible polypropylene/poly(butylene succinate) (PP/PBS) blend-based nanocomposites were successfully prepared using an internal mixer. Carbon nanotube (CNT)/organo-montmorillonite (15A) and maleated PP (PPgMA) served as the reinforcing nanofillers and compatibilizer, respectively. Scanning electron microscopy results showed that PPgMA played an efficient role as compatibilizer for reducing the dispersed domain size of PBS in the blend. The added CNT was randomly distributed within the PP and PBS phases, whereas 15A was selectively located in the PBS domain. Differential scanning calorimetry results confirmed the nucleation effect of CNT on the PP/PBS crystallization, but 15A addition only facilitated the PBS crystallization. Thermogravimetric analysis revealed that CNT and 15A both enhanced the thermal stability of the blend under air environment. The rheological property measurements confirmed the significant change in microstructure of composites through developing the pseudo-network structure with CNT and/or 15A additions. The Young’s modulus (YM) of PP/PBS blend increased evidently with the inclusion of CNT. The incorporation of 2.5 phr CNT evidently increased the YM by approximately 243% compared with that of neat PBS. The electrical resistivity of the samples drastically reduced with the addition of CNT up to 10 orders of drop at a 3-phr CNT loading. The electrical percolation was constructed at a CNT content of 0.5 phr.     

Crystal Growth in Drowning‐Out Crystallization using a T‐Mixer

The kinetics of nucleation and crystal growth in drowning‐out crystallization using a T‐mixer were estimated using crystal size distribution, taking into account a size‐independent growth. At the conditions of the feed compositions investigated, the product weight mean size changed from 7–29 μm when the residence time varied between 0.32 and 0.61 s. Nucleation and growth rates were expressed simply as a function of the residence time. The T‐mixer can be used to generate high levels of supersaturation due to inducing micro‐mixing effects. The particle size correlated well with the ratio of growth rate to nucleation rate. Finally, the particle size obtained in drowning‐out crystallization using a T‐mixer was found to be proportional to the 1.69^th power function of the residence time.     

PP/PP-g-MAH/废PCB粉复合材料非等温结晶动力学研究

利用差示扫描量热法结合Avrami方程研究了聚丙烯（PP）、聚丙烯/聚丙烯接枝马来酸酐/废印刷电路板非金属粉复合材料（PP/PP-g-MAH/废PCB粉）的非等温结晶动力学行为,根据Avrami方程的Jeziorny法和莫志深法对数据进行处理。结果表明,废PCB粉在PP基体中起到异相成核作用,提高了PP的结晶温度,使其成核速率加快,晶粒分布变窄,结晶速率增大,但当废PCB粉含量过多时,复合材料体系黏度会增大,使PP链段扩散迁移并进行规整有序排列的速度受到影响,导致结晶速率下降。     

聚丙烯挤出发泡中的关键技术——发泡体系的性能和发泡机理研究

从聚丙烯挤出发泡体系的性能包括聚丙烯熔体的黏弹性、发泡剂的溶解度和扩散系数、聚丙烯的结晶行为和成核剂的性能以及聚丙烯挤出发泡的气泡成核机理和气泡增长机理系统介绍了聚丙烯挤出发泡中的一些关键技术。研究表明：具有显著应变硬化行为和高熔体强度的长链支化聚丙烯是获得优质PP发泡材料的前提；发泡剂的溶解度和扩散系数、聚丙烯的结晶行为和成核剂的种类和性能对发泡材料的泡孔密度、泡孔尺寸和泡孔尺寸分布有显著影响；气泡成核和气泡增长机理对于聚丙烯挤出发泡的配方设计、工艺确定和设备选型具有极其重要的意义。