Crystallization behaviors of polypropylene/montmorillonite nanocomposites

The isothermal crystallization kinetics of polypropylene/montmorillonite (PP/MMT) nanocomposites synthesized via intercalation polymerization were investigated by using differential scanning calorimeter and polarizing optical microscope (POM). The crystallinity of the nanocomposites decreased with the increase of the montmorillonite content, indicating that the MMT layers dispersed in the PP matrices confined the PP chains and hindered the crystallization of the PP chains. The POM photographs showed that the spherulites of the PP/MMT nanocomposites were greatly decreased in size as MMT was introduced. On the other hand, the crystallization rate increased dramatically with the increasing of MMT content. The interfacial free‐energy per unit area perpendicular to PP chains in PP/MMT nanocomposites decreased with increasing MMT content, suggesting that the MMT layers acted as heterogeneous nuclei in the nucleation of crystallization. The nucleus density increased with the increasing of MMT content, leading to a positive effect on the crystallization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1978–1985, 2002     

聚丙烯/蒙脱土纳米复合材料的湿热老化性能

用熔融插层法制备了2种聚丙烯/蒙脱土(PP/OMMT)纳米复合材料,考察了在90℃的水中进行0~80 d不同时长的湿热老化后的产物特征。添加少量纳米化蒙脱土的PP表面形貌被破坏时间可延长20 d左右,比纯PP拉伸强度保持率提高67.5%,冲击强度保持率提高12.4%。PP、PP/OMMT复合材料湿热老化的损伤主要是环境中的水分子的直接物理作用,其中PP/季铵型OMMT纳米复合材料优良的抗湿热老化能力是其较高的结晶度、剥离性纳米化OMMT片层对水分子和热的物理阻隔效应以及OMMT与PP间较强的相互作用的共同结果。     

不同工艺制备的PP/蒙脱土纳米复合材料的性能

选择一种新型有机蒙脱土（MMT）,分别通过直接注塑法和挤出一注射法（简称挤出法）将聚丙烯（PP）与有机MMT复合,制备出高抗冲PP／MMT纳米复合材料。透射电子显微镜观察表明。挤出法制备的复合材料为全插层型结构,MMT分散均匀,尺寸小;而直接注塑法制备的复合材料为部分插层型结构．MMT明显分散不均匀,尺寸较大,且有少量团聚产生。力学性能测试表明,随着MMT的增加．2种试样的缺口冲击强度都有显著提高,均在ω（MMT）为4％时达到极大值。此时,挤出法试样缺口冲击强度比纯PP提高102％。屈服拉伸强度、弹性模量也略有提高;直接注塑法试样的缺口冲击强度比纯PP提高82．6％,但屈服拉伸强度、弹性模量都明显降低。     

两步法制备聚丙烯/蒙脱土纳米复合材料及其性能研究

采用两步法制备聚丙烯/蒙脱土纳米复合材料PP/MMT,考察了工艺配方和制备条件对材料力学性能的影响。结果表明,两步法制备工艺对PP/MMT的力学性能有明显提高,最佳工艺配方:蒙脱土含量为2%,相容剂含量为15%,最佳制备条件:加工温度200℃,螺杆转速50 r/min。在此条件下制备的PP/MMT复合材料中蒙脱土达到纳米级分散。     

Influences of catalysis and dispersion of organically modified montmorillonite on flame retardancy of polypropylene nanocomposites

The degradation and flame retardancy of polypropylene/organically modified montmorillonite (PP/OMMT) nanocomposite were studied by means of gas chromatography‐mass spectrometry and cone calorimeter. The catalysis of hydrogen proton containing montmorillonite (H‐MMT) derived from thermal decomposition of (alkyl) ammonium in the OMMT on degradation of PP strongly influence carbonization behavior of PP and then flame retardancy. Brønsted acid sites on the H‐MMT could catalyze degradation reaction of PP via cationic mechanism, which leads to the formation of char during combustion of PP via hydride transfer reaction. A continuous carbonaceous MMT‐rich char on the surface of the burned residues, which work as a protective barrier to heat and mass transfer, results from the homogeneous dispersion of OMMT in the PP matrix and appropriate char produced. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and physical properties of wood/polypropylene/clay nanocomposites

Wood plastic composites (WPCs) are attracting a lot of interests because they are economic, environmentally friendly, and show fairly good performance. To improve the performance of a wood/polypropylene (PP) composite, an organoclay was incorporated as a nanosize filler in this work. WPCs were prepared by melt blending followed by compression molding, and their performance was investigated by universal testing machine, izod impact tester, dynamic mechanical analyzer, thermal mechanical analyzer, differential scanning calorimetry, and TGA. Maleic anhydride polypropylene copolymer (MAPP) was used to increase compatibility between the PP matrix and wood particles and also improve the dispersion and exfoliation of the organoclay in the PP matrix. XRD analysis showed that the matrix of the WPCs with organoclay had intercalated structure. The SEM images of the WPCs with MAPP showed improved interfacial adhesion between the matrix and wood particles. The degree of water absorption increased with immersion time, but it could be restrained by incorporating MAPP. The performance of the WPCs was improved by the incorporation of the organoclay. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Crystallization behavior of polypropylene/polyamide 6/montmorillonite nanocomposites

Polymer blended materials such as polyamide 6 (PA6)/polypropylene (PP) blends have received considerable attention in recent years. To improve the compatibility of PA6 and PP, compatibilizers like maleic anhydride‐g‐polypropylene (MPP) are often added. In addition, organically modified montmorillonite (MMT) is also used to improve the properties of various materials. In this work, the crystallization behavior of PP/PA6/MMT nanocomposites with MPP compatibilizer was investigated systematically. The annealing process effectively improved the crystallization of α‐PP. The crystallization temperature (T_c) of PA6 was increased by ca 2–3 °C on introducing MPP or MMT alone to the PP/PA6 system, whereas T_c of PP underwent no obvious change. However, when MPP and MMT were added simultaneously, T_c of PP and PA6 increased by 6.6 and 4.2 °C, respectively, and a new crystallization peak corresponding to PP‐g‐PA6 copolymer phase was observed at 162.5 °C. The combined effect of MPP and MMT led to better compatibility of PP with PA6. Moreover, the results of a non‐isothermal crystallization kinetics experiment revealed that the simultaneous introduction of MPP and MMT markedly shortened the crystallization time. Copyright © 2010 Society of Chemical Industry     

Preparation and properties of polyethylene/montmorillonite nanocomposites by in situ polymerization

Polyethylene (PE)/montmorillonite (MMT) nanocomposites were prepared by in situ coordination polymerization using a MMT/MgCl₂/TiCl₄ catalyst activated by Al(Et)₃. The catalyst was prepared by first diffusing MgCl₂ into the swollen MMT layers, followed by loading TiCl₄ on the inner/outer layer surfaces of MMT where MgCl₂ was already deposited. The intercalation of MMT layers by MgCl₂ and TiCl₄ was demonstrated by the enlarged interlayer spacing determined by WAXD. The nanoscale dispersion of MMT layers in the polyethylene matrix was characterized by WAXD and TEM. As a consequence, the crystallinity of the nanocomposite decreased sharply, whereas the tensile strength was significantly improved compared to that of virgin polyethylene of comparable molecular weight. The confinement of the nanodispersed MMT layers to molecular chain and the strong interaction between the nanoscale MMT layers and the resin matrix were thought to account for the decrease of crystallinity and the remarkable enhancement of strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3680–3684, 2003     

Intumescent flame retardant–montmorillonite synergism in polypropylene‐layered silicate nanocomposites

Polypropylene/clay nanocomposites have been prepared starting from pristine mont morillonite (MMT) and reactive compatibilizer hexadecyltrimethylammonium bromide (C16). The nanocomposite structure is evidenced by the X‐ray diffraction and high resolution electronic microscopy. Intumescent flame retardant has been added to polypropylene/clay hybrids. Their flammability behaviours have been evaluated using cone calorimetry. Synergy was observed between the nanocomposites and intumescent flame retardant. Copyright © 2003 Society of Chemical Industry     

线性低密度聚乙烯/有机蒙脱土纳米复合材料的制备及性能研究

通过熔融共混法制备了线性低密度聚乙烯／有机蒙脱土（LLDPEtOMMT）纳米复合材料,采用X-射线衍射分析（XRD）和透射电镜（TEM）对材料的结构进行表征,研究了OMMT的用量对LLDPE／OMMT纳米复合材料力学性能及阻燃性能的影响。结果表明,当OMMT的用量为30％（重量百分比）8寸,材料的极限氧指数（LOI）从180％提高到23．8％,热释放速率峰值（PHRR）从LLDPE的771．9kW／m2下降到5113kW／m2,下降幅度高达33．8％,表现出较好的阻燃性能;同时材料也呈现出良好的力学性能。     

熔体插层制备硅橡胶/蒙脱土纳米复合材料的性能研究

通过熔体插层成功制备了硅橡胶／蒙脱土纳米复合材料，通过XRD和SEM分析可知，在所选择的两步工艺务件下。蒙脱土被硅橡胶分子链插层剥离。获得剥离型的纳米复合材料。同时，测试了其力学性能和耐热性能。所得到的复合物的性能较纯硅橡胶有很大的提高，且与气相法白炭黑填充体系的性能相当。并且研究了硅烷偶联剂对填料-硅橡胶之间的增强作用。     

Morphology and mechanical properties of polypropylene/organoclay nanocomposites

Polypropylene (PP) nanocomposites were prepared by melt intercalation in an intermeshing corotating twin‐screw extruder. The effect of molecular weight of PP‐MA (maleic anhydride‐ modified polypropylene) on clay dispersion and mechanical properties of nanocomposites was investigated. After injection molding, the tensile properties and impact strength were measured. The best overall mechanical properties were found for composites containing PP‐MA having the highest molecular weight. The basal spacing of clay in the composites was measured by X‐ray diffraction (XRD). Nanoscale morphology of the samples was observed by transmission electron microscopy (TEM). The crystallization kinetics was measured by differential scanning calorimetry (DSC) and optical microscopy at a fixed crystallization temperature. Increasing the clay content in PP‐ MA330k/clay, a well‐dispersed two‐component system, caused the impact strength to decrease while the crystallization kinetics and the spherulite size remained almost the same. On the other hand, PP/PP‐MA330k/clay, an intercalated three‐component system containing some dispersed clay as well as the clay tactoids, showed a much smaller size of spherulites and a slight increase in impact strength with increasing the clay content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1562–1570, 2002     

The effect of organo‐montmorillonite on the compatibility and properties of nylon 66/polypropylene blend

Nylon 66/polypropylene (PP) blends containing maleated polypropylene and organo‐montmorillonite (OMMT) have been prepared by melt compounding using a well‐dispersed master‐batch of nylon 6/OMMT nanocomposite as the source of OMMT. The effects of OMMT platelets on the compatibility and properties of the blends have been investigated. The blend morphology has been observed by the use of field emission scanning electron microscopy, showing a sharp decrease in domain size. The dispersion and location of OMMT have been investigated by X‐ray diffraction and transmission electron microscopy. A high‐density occupation of OMMT at the interface (i.e. Nylon‐g‐PP interphase region) is revealed by Fourier transform infrared spectroscopy and thermogravimetric analysis of the extraction residue after the removal of nylon phase by formic acid. A significant gain in stiffness is realized with the use of OMMT while the toughness of the material is maintained. The possible mechanism of compatibilization also is discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

有机蒙脱土/丁基橡胶/聚丙烯热塑性硫化胶的制备与性能

采用动态硫化法制备了有机蒙脱土(OMMT)/丁基橡胶(IIR)/聚丙烯(PP)热塑性硫化胶(TPV),考察了OMMT的用量和IIR/PP的质量比对TPV的物理机械性能、动态力学性能及热性能的影响.结果表明,当OMMT的用量为20份时,TPV的物理机械性能较佳,Payne效应最弱,OMMT均匀地分布在基体中,阻尼性能较好...     

聚合物/蒙脱土纳米复合材料的研究进展

聚合物/蒙脱土纳米复合材料是近十年来研究最为广泛的复合材料之一,优异的热力学性能,独特的气 液阻隔性及阻燃性赋予它广泛的工业应用前景。本文就该复合材料在蒙脱土的有机改性处理、制备、制备条件对性能的影响、表征方法及手段、材料性能特征及应用等方面作一些简单总结。     

Study on rheological behavior of polypropylene/clay nanocomposites

Polypropylene/montmorillonite nanocomposites (PPCN) were prepared by melt intercalation with maleic anhydride modified low isotactic polypropylene as the compatibilizer. The linear and nonlinear rheological properties of polypropylene/montmorillonite nanocomposites were studied. The deviation from linear behavior occurred at a strain of 10⁰ that was quite less than that for the polymer matrix. The results of dynamic frequency scan showed that the percolation threshold of PPCN was near 3 wt %. Having been subjected to steady preshear, the tactoids could be oriented preferentially in the shear direction, and the percolation network was ruptured. The magnitudes of the stress overshoots observed in the reverse flow experiments were strongly dependent on the rest time, which indicated that the ruptured network could be reorganized even under quiescent conditions. Furthermore, PPCN displayed a strain‐scaling stress response to the startup of steady shear. The maxima of the stress overshoots appeared at the stain of 10⁰, which was consistent with the strain where the deviation of linear viscoelastic behavior started. It might imply that subjected to the deformation less than 10⁰, the network structure could be regard as elastic one. Additionally, the analogous strain‐scaling stress response to the startup steady shear elucidated the structural analogy between PPCN and liquid crystal polymer solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3609–3617, 2003     

Structure and properties of polybutadiene/montmorillonite nanocomposites prepared by in situ polymerization

Polybutadiene (PB)/Montmorillonite nanocomposites (NCs) were prepared by in situ polymerization through the anionic polymerization technique. The effects of treating method of organophilic MMT (OMMT), the type of OMMT, and the solvent used in polymerization were studied. The structure and properties of NCs were characterized using X‐ray Diffraction (XRD), transmission electron micrograph (TEM), H‐NMR spectrum, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The consumption of BuLi was varied with different treating methods. The molecular weight distribution of PB added with OMMT (DK1) was wide, and the molecular weight distribution became narrow when OMMT‐DK1B and DK4 were added. OMMT did not disperse stably in cyclohexane, but could form a homogeneous solution in toluene and xylene. XRD and TEM showed that exfoliated NCs were obtained by in situ polymerization through the anionic polymerization technique. From the H‐NMR spectrum of PB and PB/OMMT NCs, it could be seen that the content of 1, 2 units of PB increased ～100%, while 1, 4 units decreased when 6.2 wt % of OMMT was added. The results of DSC and DMA indicated that T_g and T_dc were increased when compared with those of PB. Both storage modulus and loss modulus were increased with the addition of OMMT, and tan δ was decreased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3615–3621, 2006     

凝聚共沉法制备的蒙脱土／天然橡胶纳米复合材料及其性能研究

以新鲜胶乳为主体材料,有机改性蒙脱土为填料,用凝聚共沉法制备了蒙脱土／天然橡胶复合材料,研究了复合材料的物理性能、动态力学性能及其热稳定性。结果表明,在天然橡胶中加入少量（3％-5％）的纳米蒙脱土,可以使橡胶的定伸应力、拉伸强度等性能大幅度提高,动态力学性能和耐热稳定性得到明显改善。     

Preparation and characterization of light‐cured methacrylate/montmorillonite nanocomposites

Polymer/clay nanocomposites were prepared from dimethacrylate monomers, commonly used in dental restorative resins, and an organically modified silicate (montmorillonite). The photopolymerization process was hardly affected by the presence of the silicate filler, and thus 2 mm thick samples containing 3 wt% clay were extensively cured. Transmission electron microscopy revealed that the montmorillonite platelets were either intercalated or exfoliated. Nevertheless, for all formulations, intermediate‐sized aggregates of about 1 µm were present and their fraction increased as the amount of filler increased. The presence of the clay was found to have no major effect on the flexural modulus and compressive yield strength of the nanocomposites. Moreover, the water uptake of nanocomposites containing 3 wt% clay was about 10–15% higher than that of unfilled monomers. Modification of the clay surface with alternative organic cations is certainly necessary in order to achieve an optimal dispersion of the clay in the polymer matrix. Copyright © 2010 Society of Chemical Industry     

Effects of montmorillonite on structures and properties of injection-molded polypropylene

A nanocomposite of polypropylene with montmorillonite (PP-MMT) was prepared via melt blending. The structures and properties of PP-MMT were studied by differential scanning calorimetry, polarized optical microscopy, transmission electron microscopy (TEM), and wide-angle X-ray diffraction (WAXD). The orientation behaviors of both MMT and PP in an injection-molded specimen were revealed by TEM and WAXD. The results indicate that the specimen displays a multilayer structure: in the inner layer, the long axes of MMT stacks are parallel to the transverse direction (TD) of the specimen and the b-axes of PP crystallites are perpendicular to the TD; whereas in the outer layer, the long axes of MMT are perpendicular to the TD and the b-axes of PP crystallites are parallel to the TD. The orientation of PP crystallites in PP-MMT is much lower than that in pure PP, which results in lower molding shrinkage of PP-MMT. Structure–property relationship of PP-MMT was discussed with a conclusion that a moderate improvement in performances of PP-MMT might be derived from the intercalated dispersion and special orientation of MMT stacks. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47442.