聚丙烯／纳米碳酸钙原位聚合复合材料的结晶特性研究

采用DSC方法，研究了四种不同纳米CaCO3含量的PP／CaCO3纳米原位聚合复合材料的结晶特性，并通过偏光显微镜观察了其结晶结构，同时和纯PP进行了比较。结果表明，纳米CaCO3在PP中具有成核作用，PP以异相成核方式结晶，使PP的结晶温度提高，结晶速率增大，球晶颗粒变小。从纳米CaCO3含量对PP结晶特性的研究可知，其含量在2％～3％时，对PP的上述结晶行为影响最为明显。     

PP/纳米SiO2/POE复合材料的研究

采用熔融共混法制备PP/纳米SiO2/POE复合材料,并通过力学性能测试、DSC分析以及材料断面形貌分析等手段,对增强增韧效果进行研究.结果表明纳米SiO2和POE微粒显现了比较明显的协同增韧效果,当PP/纳米SiO2/POE为100/4/15时,综合力学性能最优.纳米SiO2的成核作用提高了PP的结晶温度和结晶速率.两种微粒在PP基体中达到均匀分散,其中纳米SiO2粒子平均粒径为150nm,与其二次粒子直径相当,表明熔融过程并未造成纳米粒子的团聚.     

SiO2-P(St-EMA)纳米微球的制备及在PP中的应用

采用多步乳液聚合法在纳米SiO2表面接枝苯乙烯(St)和甲基丙烯酸乙酯(EMA),制得具有核壳结构的SiO2-P(St- EMA)纳米微球,并通过熔融共混方法制备该微球和聚丙烯(PP)基复合材料,研究其力学性能和结晶性能.研究结果表明:SiO2-P(St-EMA)纳米微球具有以SiO2为核,P(St-EMA)为壳的核壳结构,可明显改善纳米SiO2的分散性;当SiO2-P(St-EMA)的填充量达到1％时,复合材料的拉伸强度和冲击强度就有明显的提高,并可在PP中起到异相成核作用,提高PP的结晶温度和熔融温度.     

SiO_2-g-PMMA/PP纳米复合材料的制备及其性能研究

采用熔融共混的方法,将经甲基丙烯酸甲酯(MMA)表面接枝的纳米二氧化硅(SiO2-g-PMMA)填充到聚丙烯(PP)中,研究了SiO2-g-PMMA纳米杂化粒子对PP的力学性能和结晶性能的影响。结果表明,SiO2-g-PMMA可以有效地提高PP的拉伸强度、弯曲强度以及洛氏硬度,且效果好于未改性的纳米SiO2。DSC测试结果表明SiO2-g-PMMA的异相成核效果优于未改性SiO2,PP熔融温度提高了2.7℃,结晶温度提高了3.0℃。SEM表明杂化纳米粒子具有一定的增韧作用。     

PP/纳米SiO2复合材料的非等温结晶动力学

采用差示扫描量热法研究了聚丙烯（PP）/纳米SiO2复合材料的非等温结晶动力学,研究了纳米粒子的成核活性及复合材料的结晶有效能垒。研究结果表明,纳米SiO2起到异相成核的作用,使PP的结晶峰温升高,结晶总速率增大;增容剂马来酸酐接枝聚丙烯(PP-g-MAH)提高了纳米SiO2的成核活性;添加纳米SiO2使复合材料的结晶有效能垒降低,PP-g-MAH使复合材料的结晶有效能垒增大,但低于纯PP的结晶有效能垒。     

PP-g-MAH对PP/纳米SiO_2复合材料性能的影响

采用熔融共混法制备了聚丙烯(PP)/纳米SiO2复合材料,研究了相容剂马来酸酐接枝聚丙烯(PP-g-MAH)对复合材料力学性能、结晶性能及界面作用的影响。结果表明:PP-g-MAH能有效地增强纳米SiO2与PP基体间的界面作用,提高复合材料的力学性能;同时,PP-g-MAH增强了纳米SiO2的成核活性,使PP的结晶温度升高,球晶细化。     

动态硫化法PP／EPDM／纳米SiO2双重粒子协同增韧改性研究

以三元乙丙橡胶（EPDM）作弹性粒子,以纳米SiO2作刚性粒子,通过动态硫化方法制备了PP／EPDM／纳米SiO2三元改性材料,并采用力学性能测试,动态力学试验,DSC分析和偏光显微镜观察等方法,研究了该材料的结构与性能。结果表明,纳米SiO2与EPDM对PP具有协同增韧和增强效应,这种效应与2种粒子的浓度比相关,当纳米SiO2质量分数为3％,EPDM质量分数为10％时,协同作用最明显,2种粒子使PP出现较大的低温损耗模量峰（E″）和内耗峰（tanδ),并具有成核作用,使PP结晶温度提高,结晶速率加快,形成的球晶细小而均匀,并同时提高结晶度和熔点。     

动态硫化法PP/EPDM/纳米SiO_2双重粒子协同增韧改性研究

以三元乙丙橡胶 (EPDM)作弹性粒子 ,以纳米SiO2 作刚性粒子 ,通过动态硫化方法制备了PP/EPDM/纳米SiO2 三元改性材料 ,并采用力学性能测试、动态力学试验、DSC分析和偏光显微镜观察等方法 ,研究了该材料的结构与性能。结果表明 ,纳米SiO2 与EPDM对PP具有协同增韧和增强效应 ,这种效应与 2种粒子的浓度比相关 ,当纳米SiO2 质量分数为 3 %、EPDM质量分数为 1 0 %时 ,协同作用最明显。 2种粒子使PP出现较大的低温损耗模量峰 (E″)和内耗峰 (tanδ) ,并具有成核作用 ,使PP结晶温度提高 ,结晶速率加快 ,形成的球晶细小而均匀 ,并同时提高结晶度和熔点。     

PP基纳米SiO2复合材料性能的研究

利用纳米SiO2、马来酸酐接枝聚乙烯（PE-g-MAH）和聚丙烯（PP）通过熔融共混的加工工艺制备了PP基纳米SiO2复合材料，考察了不同处理方法及用量的纳米SiO2对PP基体的影响。结果表明：经表面处理，用量4％（质量分数，下同）的纳米SiO2和4％PEgMAH协同作用，可以使复合材料的冲击强度提高40％，拉仲强度提高10％，耐热性较PP基体提高22℃。采用偏光显微镜（POM）、扫描电镜（SEM）对PP基纳米SiO2复合材料的微观结构进行了表征和分析，证明经表面改性的纳米SiO2（TS530）均匀地分散于PP基体中，从而起到良好的改性作用。     

PP/POE-g-GMA/纳米SiO2复合材料性能研究

采用熔融共混法制备了聚丙烯/甲基丙烯酸缩水甘油酯接枝POE/纳米二氧化硅(PP/POE-g-GMA/纳米SiO2)复合材料,研究了材料的力学性能、动态力学性能与结晶性能.结果表明:5%的POE-g-GMA和3%的氨基功能化纳米SiO2(SiO2-g-NH2)具有明显的协同增韧效应,冲击强度提高157%,使PP出现较大的低温损耗模量峰和内耗峰;POE-g-GMA和纳米SiO2对PP的结晶均有促进作用,SiO2-g-NH2的异相成核作用更明显;POE-g-GMA能诱导PPβ晶的形成,添加纳米SiO2使β晶含量降低.     

纳米SiO2增强增韧聚丙烯的研究

通过熔融共混法制备了SiO2分散很好的聚丙烯／纳米SiO2复合材料。力学性能测试结果表明，当使用2份纳米SiO2时，聚丙烯／纳米SiO2复合材料的力学最优：与纯PP相比，V形缺口冲击强度邮90％，弯曲强度提高了23％，拉伸强度提高了5％；成型收缩率增大，这是由于大量分散于PP中的超细SiO2使PP晶体变小引起的。     

Effects of crosslinked elastomer particles on heterogeneous nucleation of isotactic PP in dynamically vulcanized EPDM/PP and EOC/PP blends

The isothermal and non-isothermal crystallizations of PP in neat form and in the TPVs EPDM/PP and EOC/PP were investigated using differential scanning calorimetry (DSC). The crystallization of PP was systematically studied by fitting mathematical models, and was later confirmed by X-ray diffraction (XRD) and by scanning electron microscopy (SEM). The experiments revealed that crosslinked elastomer particles first accelerated the primary nucleation of the PP matrix, acting effectively as a nucleating agent that reduces the induction time while increasing the nucleation efficiency. In the secondary nucleation regime (growth of spherulites), the crosslinked elastomer particles enhanced crystal growth rate, reducing the nucleation energy contribution from PP chain folding. Moreover, the crosslinked elastomer particles increased the final thickness of PP lamellae from that of neat PP, and this was corroborated by the XRD results. On comparing the two types of elastomer, it was found that the EOC particles were more effective in heterogeneous cell nucleation than the EPDM particles. The morphological study by SEM revealed completely altered PP spherulite size and shape, as well as their altered distribution, affected by heterogeneous nucleation effects of the crosslinked elastomer particles.     

Solid‐state foaming of isotactic polypropylene and its composites with spherical or fibrous poly(butylenes terephthalate)

In this article, the foaming behavior of isotactic polypropylene (iPP) and its composites with spherical or fibrous poly(butylenes terephthalate) (PBT) using supercritical CO₂ as a blowing agent were investigated. Their foaming performances were also compared in relation to the crystal morphology and rheological behavior of PP. Results demonstrate that crystal structures significantly impacted the cell structures of foams. At relatively low temperature, microcells appeared at the centers of PP spherulites where the melting started. Particularly, bi‐modal cell structure formed in the foamed PP with increasing temperature. However, in the foamed PP composites with spherical or fibrous PBT, this structure almost disappeared due to the smaller PP spherulites. In foaming PP/PBT composites, the heterogeneous nucleation of spherical or fibrous PBT was effective at reducing cell size as well as improving cell density and cell uniformity. The fibrous PBT also acted as scaffolds for preserving cell shapes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41801.     

Preparation of micro/nanocellular polypropylene foam with crystal nucleating agents

Open‐cell, porous microcellular foams with nanofibrillated structures were prepared from high tacticity isotactic polypropylene (i‐PP) with a crystal nucleating and gelling agent. The 1,3:2,4 bis‐O‐(4‐methylbenzylidene)‐d ‐sorbitol gelling agent (Gel‐all MD) was used as the crystal nucleating and gelling agent, which enhanced the crystallization and gelation of i‐PP with a three‐dimensional network of highly connected nanofibrils. The core‐back foam injection molding technique was employed to foam the i‐PP with nitrogen (N₂) at a high expansion ratio, where the crystal nucleating agent induced bubble nucleation and bubble growth in the inter‐lamella region and opened the cell walls with a nanoscale‐fibrillated structure. The effects of the nucleating agent on the open cell content (OCC), density and crystallinity were thoroughly investigated. We prepared open‐cell micro/nanocellular foams with an average cell size of microscale voids of < 5 μm. Nanometer‐scale fibrillated structures were formed on the cell wall of the microscale void, the expansion ratio was five‐fold and the open cell content was over 90%. POLYM. ENG. SCI., 54:2075–2085, 2014. © 2013 Society of Plastics Engineers     

Effect of silicon dioxide on crystallization and melting behavior of polypropylene

The crystallization and melting behavior of isotactic polypropylene (iPP) and polypropylene copolymer (co‐PP) containing silicon dioxide (SiO₂) were investigated by differential scanning calorimeter (DSC). SiO₂ had a heterogenous nucleating effect on iPP, leading to a moderate increase in the crystallization temperature and a decrease in the half crystallization time. However, SiO₂ decreased the crystallization temperature and prolonged the half crystallization time of co‐PP. A modified Avrami theory was successfully used to well describe the early stages of nonisothermal crystallization of iPP, co‐PP, and their composites. SiO₂ exhibited high nucleation activity for iPP, but showed little nucleation activity for co‐PP and even restrained nucleation. The iPP/SiO₂ composite had higher activation energy of crystal growth than iPP, indicating the difficulty of crystal growth of the composite. The co‐PP/SiO₂ composite had lower activation energy than co‐PP, indicating the ease of crystal growth of the composite. Crystallization rates of iPP, co‐PP, and their composites depended on the nucleation. Because of its high rate of nucleation, the iPP/SiO₂ composite had higher crystallization rate than iPP. Because of its low rate of nucleation, the co‐PP/SiO₂ composite had lower crystallization rate than co‐PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1889–1898, 2006     

Crystallization Behaviors of amino-terminated polyurethane (ATPU)-grafted polypropylene

Summary A melt-grafting approach was employed to prepare a novel functional polypropylene(FPP)—amino-terminated polyurethane grafted polypropylene (PP-g-ATPU). The crystallization behaviors of PP and PP/FPP blends were characterized using differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and polarized optical microscopy (POM). The effects of FPP composition on crystallization behavior, crystal transformation, and morphology of PP/FPP crystalline were investigated. The results showed that at a low dosage (<2.0 wt%) ATPU acted as a heterogeneous nucleation agent during the crystallization of PP/FPP blends. However, when the content of ATPU reached 2.0 wt% or higher, ATPU deteriorated the crystallization of PP or PP/FPP blends. The crystallite size decreased and the number of crystallites increased as the ATPU content increased. The Avrami analysis was adopted to describe the isothermal crystallization process. The difference in the exponent n between PP and PP/FPP suggested that the isothermal crystallization kinetics of PP/FPP blends followed a three-dimensional growth via heterogeneous nucleation. In terms of the half-time of the crystallization, t_1/2, the crystallization rate of functional PP blends was faster than that of PP homopolymer at a given crystallization temperature.     

纳米粒子/聚烯烃复合材料的结晶性能研究

报道了无机纳米粒子／聚烯烃复合材料的结晶性能研究。探索了有机成核剂苯甲酸纳、纳米二氧化钛、纳米碳酸钙对聚丙烯(PP)、高密度聚乙烯(HDPE)及其共混物的结晶形态影响，并用差示扫描量热计分析了PP，HDPE和HDPE／PP及其纳米复合材料的结晶性能。结果表明，HDPE／PP共混使HDPE的熔点(Tm)下降，PP的Tm保持不变；成核剂的加入均会使材料的Tm向低温侧移动且结晶度下降；无机纳米粒子对材料晶粒细化作用大大优于有机成核剂，纳米二氧化钛的晶粒细化作用最佳。     

Crystallization behavior and mechanical properties of polypropylene/halloysite composites

In this work, halloysite nanotubes (HNTs), a new type of inexpensive filler, were used for the modification of polypropylene (PP). HNTs were first surface treated by methyl, tallow, bis-2-hydroxyethyl, quaternary ammonium, then melt mixed with PP. Scanning electron microscope (SEM) was used to examine the dispersion of HNTs in PP matrix. Differential scanning calorimetry (DSC), polarized light microscope (PLM), dynamic melt rheometry and wide angle X-ray diffraction (WAXD) were employed to investigate the crystallization behavior of the prepared PP/HNT composites. The mechanical properties were evaluated by Instron and impact tests. SEM results revealed that HNTs could be well-dispersed in PP matrix and had a good interfacial interaction with PP, even up to a high content of 10 wt%. DSC data indicated that HNTs could serve as a nucleation agent, resulting in an enhancement of the overall crystallization rate and the non-isothermal crystallization temperature of PP. PLM showed a constant spherulite growth rate and a decreased spherulite size at given isothermal crystallization temperature, suggesting that nucleation and growth of a spherulite are two independent processes. The result obtained by dynamic melt rheometry indicated that HNTs mainly promoted nucleation and had not much influence on the growth of PP crystallization. Nevertheless, by fast cooling the samples, almost constant spherulite size can be obtained for both pure PP and PP/HNT composites due to the limited nucleation effect of HNTs on PP crystallization. WAXD showed that HNTs mainly facilitated α-crystal form of PP. Though a good dispersion of HNTs in PP matrix was observed, out of our expectation, not much enhancement on mechanical properties of PP/HNT composites had been achieved, and this could be mainly ascribed to the constant crystallinity and spherulite size of PP as well as the small length/diameter ratio of HNTs.     

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。     

聚丙烯固相接枝双单体共聚物的等温结晶行为

用差示扫描量热法结合Avrami方程研究了聚丙烯(PP)与马来酸酐、甲基丙烯酸甲酯双单体固相接枝物的等温结晶行为；用Arrhenius公式分析了接枝支链对PP结晶活化能的影响。研究表明：接枝支链引起PP的结晶成核和结晶生长方式发生变化,既起到异相成核作用,又阻碍了分子链的运动,降低了晶体生长速率。