纳米碳酸钙微粒填充改性聚丙烯复合材料的力学性能和结晶行为研究

研究了两种不同粒径的纳米碳酸钙(Nano-CaCO3)熔融共混改性均聚聚丙烯(PP)材料的力学性能和结晶行为，结果表明，两种纳米CaCO3填料对PP的B晶形成均有不同程度的诱导作用，并可提高基体结晶温度和结晶速率，从而提高材料的冲击韧性．     

丙烯酸及其接枝物对纳米CaCO3/PP结晶与熔融行为的影响

制备了丙烯酸(AA)及其接枝聚丙烯(PP—g-AA)改性的纳米CaC03／PP复合材料。用DSC研究了纳米CaCO3对PP、PP-g-A和AA对纳米CaCO3／PP中PP结晶与熔融行为的影响。结果表明：随纳米CaCO3用量增加，PP结晶与熔融温度提高，PP—g—AA加入使PP结晶温度进一步提高，PP的结晶温度也随从用量增加而提高；在过氧化二异丙苯(DCP)存在下，少量AA能明显提高PP的结晶温度，但增加从用量对结晶温度的影响较小；WAXD证实纳米CaCO3／PP复合材料中存在β晶。     

聚丙烯/纳米蒙脱土复合材料的结晶动力学研究

采用热分析方法，研究了聚丙烯／纳米蒙脱土复合材料（PP／CLAY）的等温结晶行为，并分别用Avrami方程和赵志英方法对所得数据进行了分析，研究结果表明，纳米蒙脱土微粒对聚丙烯等温和非等温结晶行为均有不同程度的影响，可提高聚丙烯的结晶速率并改善结晶结构。     

具有包藏结构的三元聚丙烯纳米复合材料结构与性能关系的研究

制备了一种新型聚丙烯 丁苯橡胶 纳米碳酸钙三元纳米复合材料 .研究结果显示 ,复合材料中的大多数纳米碳酸钙粒子被包藏在丁苯橡胶中 ,并与之共同形成分散于聚丙烯树脂中的分散相 ,这种聚丙烯纳米复合材料具有高刚性、高韧性、高耐热性和高的结晶速率 .系统研究了成核剂苯甲酸钠的加入和纳米碳酸钙的用量对该类纳米复合材料相态结构、结晶形态和结晶动力学的影响 ,以及具有包藏结构的分散相粒径和PP中β晶含量对材料性能的影响 .结果表明 ,苯甲酸钠的加入和纳米碳酸钙用量的提高均可使体系中分散相粒径减小 ,结晶速率加快 ,进而使材料的韧性、刚性和耐热性提高 .     

表面接枝改性纳米二氧化硅填充聚丙烯的结晶行为

应用差示扫描量热方法研究了纳米二氧化硅 (SiO2 )及其表面接枝改性对聚丙烯 (PP)结晶过程、等温与非等温结晶动力学的影响 ,并研究了上述等温结晶的熔融行为和平衡熔点 .研究发现纳米SiO2 具有明显的异相成核效应 ,能够提高PP的结晶温度、熔融温度、结晶度和结晶速率 ,但降低聚丙烯结晶的完善程度 .粒子的表面接枝处理 ,因改善了粒子与基体的亲和性而有利于粒子成核效应的提高 ,而且此效应尚与粒子的分散相关     

多壁碳纳米管/聚丙烯复合材料的晶型及非等温结晶动力学

采用熔融共混法制备了多壁碳纳米管/聚丙烯(MWNT/PP)复合材料,利用X射线衍射法(XRD)、差示扫描量热法(DSC)分别研究了纯聚丙烯(PP)及MWNT/PP复合材料的晶型和非等温结晶动力学行为,并运用Mo法研究了纯PP及MWNT/PP复合材料的非等温结晶动力学行为。结果表明,多壁碳纳米管(MWNT)的加入使PP发生了由β晶型向α晶型的转变。MWNT在结晶过程中具有异相成核效应,提高了PP的结晶温度和结晶速率。MWNT/PP复合材料的结晶活化能均明显高于纯PP。MWNT的加入使PP在单位时间内达到一定结晶度所需的降温速率减小。     

聚丙烯/累托石纳米复合材料的非等温结晶动力学研究

在双螺杆挤出机上熔融共混制备了聚丙烯 (PP) 有机累托石 (OREC)纳米复合材料 ,采用广角X 射线衍射 (WAXD)定性地分析了PP OREC纳米复合材料及纯PP的结晶形态 ,由半峰宽定性地判断了对应晶面法向的晶粒的大小 .结果表明有机累托石没有改变聚丙烯的结晶晶型 (纳米复合材料主要还是α晶型 ) ,但是细化了晶粒的尺寸 .采用差示扫描量热法 (DSC)定量地研究了复合材料的非等温熔融结晶动力学 ,对所得数据分别用Jeziorny法的Mo法进行了处理 ,表明非等温结晶动力学参数Zc 及Avrami指数n随冷却速率的增加而增加 ,复合材料的Avrami指数n大于纯PP的n ;对相同配比的纳米复合材料 ,随着结晶度的增加 ,单位结晶时间里达到一定结晶度所需要的降温速率F(T)增大 ,对同一个设定的结晶度 ,纳米复合材料的F(T)比纯PP的小 ,说明需要的降温速率减小 .所有这些均说明有机累托石可作为聚丙烯的结晶成核剂 .     

阻燃聚丙烯体系结晶动力学研究

本工作利用JJY-1型结晶速率仪对几种典型的阻燃聚丙烯共混体系的结晶行为进行了研究,发现不同的阻燃剂对PP的结晶行为有不同的影响。阻燃剂APP对PP的结晶具有较强的成核作用。但过量的APP对PP结晶生长有明显的阻碍作用。阻燃剂TBE对PP结晶也体现异相成核作用。阻燃剂PER由于增加PP结晶过程的分子链段折叠能而对PP结晶起阻碍作用。阻燃剂TPP对PP的结晶行为影响较弱。     

聚丙烯“催化合金”组成对结晶行为的影响

用示差扫描量热仪(DSC)和偏光显微镜(POM)研究了聚丙烯“催化合金”(PP-cats)组成对等温结晶行为与动力学的影响,并与等规聚丙烯(iPP)进行比较.结果表明,与纯PP相比较,PP-cats的平衡熔融温度明显下降,表明PP-cats中作为主要组分的丙烯均聚物和乙丙无规共聚物之间存在较强的相互作用.PP-cats的结晶初期动力学可用Avrami模型很好地描述,结晶过程均为预先成核和三维生长方式.PP-cats的结晶速率随体系中乙丙共聚物含量的增加而增大,而PP-cats的晶体生长速率随体系中乙丙共聚物含量的增加而减小.由于PP-cats熔体的粘度远高于纯PP,使得PP-cats中PP分子链运动能力降低,导致了PP-cats较低的晶体生长速率.此外,与纯PP相比,PP-cats的成核密度大幅度提高,被认为是PP-cats具有快的结晶速率的主要原因.     

纳米CaCO_3/相容剂/PP中的界面相互作用研究

采用不同相容剂(PP-g-MAH、POE-g-MAH和EVA-g-MAH)制备了不同界面相互作用的纳米CaCO3(CC)/相容剂/PP体系,研究了相容剂/PP和相容剂/CC界面相互作用对PP/CC的结晶形态、结晶行为、熔融特性和力学性能的影响.观察到PP/CC界面相互作用提高PP结晶温度和PP/CC的模量和冲击强度,但降低了屈服强度.相容剂/CC界面相互作用进一步提高了PP/CC的结晶温度.PP/相容剂界面相互作用取决于PP与相容剂相容性.PP/PP-g-MAH相容性高有利于提高PP/CC的异相成核作用和PP/CC屈服强度和模量,但降低冲击强度.PP/POE-g-MAH部分相容对相容剂/CC界面的异相成核作用、PP/CC屈服强度和模量影响不大,可明显提高冲击强度.但PP/EVA-g-MAH不相容导致PP/CC冲击强度明显降低.     

Transcrystallization in nanofiber bundle/isotactic polypropylene composites: effect of matrix molecular weight

Polyamide 66 (PA 66) nanofiber bundles were first electrospun and then introduced into isotactic polypropylene (iPP) melts to prepare nanofiber bundle/iPP composites. To reveal the influences of matrix molecular weight (M _n ) on the transcrystalline layer, three kinds of iPP with different M _n were adopted. Polarized optical microscope was employed to investigate the transcrystallinity. In the presence of PA 66 nanofiber bundle, the heterogeneous nucleation distinctly happened in iPP melts. Moreover, the higher the iPP M _n , the denser the nuclei. Both a decrease in matrix M _n and an increase in isothermal crystallization temperature led to an increase in the induction time. The maximum temperature at which the transcrystalline layer can be optically observed increased with the increase of M _n . The growth rate of transcrystallinity decreased with the increasing M _n and crystallization temperature. Moreover, selective melting of the transcrystalline layers confirmed that it was merely composed of α form crystal for all composites.     

碳纤维对聚丙烯结晶行为的影响

本文用偏光显微镜和示差扫描量热计(DSC)方法研究了碛纤维对聚丙烯结晶行为的影响。碳纤维表面对聚丙烯结晶过程具有明显的促进作用,纤维表面成核密度轻高,结晶生长成为横穿结晶,结晶特征温度随碳纤维加入而有不同程度的升高。结晶动力学表明:结晶生长本质仍是球晶机理,促进聚丙烯结晶的原因是碳纤维使结晶过程的表面自由能降低。     

TGA analysis of polypropylene-carbon nanofibers composites

TGA investigations on the thermal degradation of isotactic polypropylene-vapor grown carbon nanofibers composites in nitrogen are reported. The mass evolution as a function of temperature is a single sigmoid for both polypropylene and polypropylene loaded with carbon nanofibers. The inflection temperature of these sigmoids increases as the concentration of carbon nanofibers is increased. The width of the degradation process narrows as the concentration of carbon nanofibers is increased due to a better homogenization of the local temperature provided by the high thermal conductivity of carbon nanofibers. Thermogravimetric analysis data indicate the formation of polymer-carbon nanofiber interface. Based on TGA data, a two-layer structure is proposed for carbon nanofibers-polypropylene interface. The external layer is soft and has a thickness of about 10² nm that confines most polymer molecules in interaction with nanofibers. The core layer is rigid and has a thickness of the order of few nanometers.     

Spectroscopic investigations on polypropylene‐carbon nanofiber composites. I. Raman and electron spin resonance spectroscopy

Isotactic polypropylene‐vapor grown carbon nanofiber composites containing various fractions of carbon nanofibers, ranging from 0 to 20 wt %, have been prepared. Raman spectroscopy was used to analyze the effect of the dispersion of carbon nanofibers within polypropylene and the interactions between carbon nanofibers and macromolecular chains. The as‐recorded Raman spectra have been successfully fitted by a linear convolution of Lorentzian lines. Changes of the Raman lines parameters (position, intensity, width, and area) of polypropylene and carbon nanofibers were analyzed in detail. The Raman spectra of the polymeric matrix—at low concentrations of nanofibers—show important modifications that indicate strong interactions between carbon nanofibers and the polymeric matrix reflecting by vibrational dephasing of macromolecular chains. The Raman spectrum of carbon nanofibers is sensitive to the loading with carbon nanofibers, showing changes of the resonance frequencies, amplitudes, and width for both D‐ and G‐bands. Raman data reveals the increase of the disorder, as the concentration of carbon nanofibers is increased. The presence of the typical ESR line assigned to conducting electrons delocalized over carbon nanofibers is confirmed and the presence of a spurious magnetic line due to catalyst's residues is reported. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1644–1652, 2009     

Effects of modified kaolin on the crystallization property of PP/Kaolin nanocomposites

Polymer-clay nanocomposites are a class of hybrid materials composed of organic polymer matrix in which layered inorganic particles with nano-scale di- mension are distributed with self-assembled pattern uniformly. These nanocomposites synergistically int…     

Effect of Clay/Diamond and Clay/Carbon Nanosystems on Structure-Properties Relationships of iPP

The effect of the addition of two combined fillers, smectite clay and diamond and smectite clay and carbon nanoparticles, on structure, morphology, isothermal and non isothermal crystallization behaviour, tensile and thermal properties of isotactic polypropylene (iPP) has been investigated by using several techniques: wide angle X-ray diffraction, optical and scanning electron microscopy, thermogravimetry, differential scanning calorimetry and tensile techniques. It was found that nanoparticles of diamond and carbon favour the nucleation of the β-form of iPP crystal, whereas the clay nanolayers do not have any influence on the crystal structure of iPP. The thermal stability of iPP/(clay+diamond) and iPP/(clay+carbon) is improved with respect to neat iPP, whereas no influence is detected when only clay is added to iPP. At the given crystallization conditions, the overall crystallization peak of iPP/(clay+diamond) almost exactly overlaps the crystallization peak of neat iPP, whereas in the case of iPP/clay and iPP/(clay+carbon) the maximum of the crystallization peaks is shifted to higher temperature. The spherulite growth rate, G values do not differ from one another. The iPP/(clay+carbon) system shows ductile behavior. The other systems show brittle behavior with failure before necking. These results were related with the very high percentage of beta phase present in the samples of iPP/(clay+carbon).     

Enhancement of conductivity by diameter control of polyimide-based electrospun carbon nanofibers

Oxydianiline-pyromellitic dianhydride poly(amic acid) (ODA-PMDA PAA) was polymerized with a catalyst support of triethyl amine for controlling molecular weight. This polymer was used for electrospinning in the preparation of PAA nanofibers, a precursor of carbon nanofibers. Here the amount of catalyst and concentration of PAA solution were optimized to produce polyimide-based carbon nanofibers approximately 80 nm in diameter. The effects of molecular weight of PAA, bias voltage, and spinning rate on the morphology of electrospun PAA and polyimide nanofibers have been evaluated. We showed that the conductivity of the carbon nanofiber mat decreased with increasing nanofiber diameter, where the conductivity of polyimide-based carbon nanofiber mat was much higher than those of other types of carbon nanofiber mat. The key ingredient to increase conductivity in a carbon nanofiber mat was found to be the number of cross junctions between nanofibers.     

HDPE solution crystallization induced by electrospun PA66 nanofiber

Nanohybrid shish?Ckebab (NHSK), induced by polyamide 66 (PA66) nanofiber, was successfully fabricated in high-density polyethylene (HDPE)/xylene solution via isothermal crystallization. The crystalline morphological features of NHSK were observed by scanning electron microscopy. In the structure of NHSK, PA66 nanofiber serves as shish and HDPE lamellae act as kebabs periodically surrounding the nanofiber. Additionally, it reveals that both HDPE solution concentration and crystallization time have significant effects on the size of HDPE kebab. That is, as the concentration and crystallization time increase, the diameter of the kebab increases. Moreover, when crystallization time further increases, the crystals decorated on PA66 nanofiber exhibit a three-dimensional growth (i.e., aggregate of crystallites) rather than a two-dimensional one (i.e., disk-like lamellae normal to the axis of nanofiber).     

热致液晶共聚酯对聚丙烯结晶的诱导作用

用差示扫描量热法和光学解偏振法研究了热致液晶性芳香共聚酯与聚丙烯共混物的等温和非多温结晶行为.结果表明,这一热致液晶聚合物对聚丙烯结晶有诱导成核和加速作用.当共聚酯含量在2-5％之间时,聚丙烯的结晶速率最快.偏光显微镜的观察揭示出在聚丙烯熔体中原位形成的液晶聚合物微纤诱导了聚丙烯横穿晶的形成.     

Effect of montmorillonite on polypropylene crystallization

The effect of additions of pure and modified montmorrilonite on the polypropylene crystallization rate was studied within the framework of Avrami model. In the presence of these fillers in amounts of 2.5–5.0 wt %, both the crystallization rate and the degree of crystallinity increase, and at the content of these fillers increased to 10% and higher values these parameters decrease. Introduction of fillers enhances the mechanical properties of polypropylene, which allows the developed material to be recommended for the production of packaging film.