Effect of Comonomer Content on the Behavior of Propylene Copolymer/Compatibilizer/Clay Nanocomposites

A set of isotactic propylene copolymers with either 1‐hexene or 1‐octadecene were synthesized using a metallocene catalyst, and their nanocomposites with 5 wt.‐% of clay and 15 wt.‐% of compatibilizer were prepared and characterized. Clay intercalation and dispertion depend on the comonomer content in the matrix which improves at high short‐chain‐branching levels. The presence of both clay and compatibilizer increased the crystallization temperature of the matrix. A strong correlation between the elastic modulus of the matrix and its relative increase in the nanocomposite was observed. By adding clay and compatibilizer to the copolymer, the modulus can be increased by a factor of two. The results open new perspectives in the understanding of the effect of polyolefin topology on nanocomposites properties.

     

聚乙烯/蒙脱土纳米复合材料结构与力学性能的研究

制备了MMT/MgCl2/TiCl4插层型催化剂,并进行乙烯聚合。考察了MMT片层间距、复合材料形态及蒙脱土在其中的分布状态。考察了材料的冲击强度、拉伸强度等力学性能及蒙脱土的最佳含量。     

Influence of the Botanic Origin of Starch Nanocrystals on the Morphological and Mechanical Properties of Natural Rubber Nanocomposites

The structural and mechanical properties of natural rubber (NR) nanocomposites filled with starch nanocrystals (SNC) extracted from four different starch sources are investigated. The aim of this work is to explore the influence of botanic sources on final properties of nanocomposites and SNC reinforcing capability. A general trend seems to be that the higher the amylose content of native starch granules used for preparing SNC, the lower the water uptake and reinforcing effect (except for potato starch). It is postulated that SNC prepared from higher amylose content starch might release loosely bonded amylose chains during preparation and/or soaking in water and thus prevent SNC to participate in the formation of a reinforcing network.

     

Interfacial effects in polypropylene–silica nanocomposites

Grafted inorganic nanoparticles can greatly improve the mechanical performance of polymers. To examine the effects of the interfacial characteristics generated by the grafting polymer bonded to nanoparticle surfaces, we chemically grafted nano‐silica with different polymers and then melt‐mixed it with polypropylene (PP). We extracted the homopolymers produced during the graft polymerization from the grafted products before the composites were manufactured to get rid of the side effects of the nongrafting polymers. We tailored the interfacial interaction between the grafted nano‐SiO₂ and PP matrix by changing the amount of the grafting polymers on the nanoparticles, that is, the grafting percentage. Mechanical tests indicated that all the composites incorporated with grafted nano‐SiO₂ particles possessed much higher impact strength than untreated SiO₂/PP composites and neat PP. The greatest contribution of the particles was made at a low grafting percentage. Tensile measurements showed that the treated nanoparticles could provide PP with stiffening, strengthening, and toughening effects at a rather low filler content (typically 0.8 vol %) because of the enhanced interfacial adhesion resulting from molecular entanglement and interdiffusion between the grating polymers on the nanoparticles and matrix macromolecules. The presence of grafting polymers on the nanoparticles provided the composites with a tailorable interphase. The tensile performance of the composites was sensitive to the nature of the grafting polymers. Basically, a hard interface was beneficial to stress transfer, whereas a soft one hindered the development of cavities in the matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1771–1781, 2004     

环氧树脂/蒙脱土纳米复合材料的性能及增韧机理

将有机蒙脱土添加到环氧树脂中,制备环氧树脂/纳米复合材料,考察复合材料的力学和热学性能,研究发现,5%的添加量可以使环氧树脂的冲击、断裂强度得到大幅度的提高,添加3%的有机蒙脱土,热变形温度提高了6.1℃.通过SEM和AFM,对环氧树脂/蒙脱土纳米复合材料冲击断口进行微观研究,发现断口呈现出明显的韧性断裂.结合微观形貌,对有机蒙脱土增韧环氧树脂的各种机理进行探讨,认为符合基体剪切屈服增韧机理.     

Structure and Properties of CdS/Regenerated Cellulose Nanocomposites

Summary: Novel inorganic‐organic hybrid materials composed of cadmium sulfide (CdS) semiconducting nanocrystals and regenerated cellulose (RC) were prepared by using in situ synthesizing method. Cellulose was dissolved in a 6 wt.‐% NaOH/4 wt.‐% urea/thiourea aqueous solution at low temperature followed by addition of cadmium chloride (CdCl₂), resulting that the CdS nanocrystals were successfully grown in situ in the cellulose solution. Nanocomposite films containing homogeneous CdS nanoparticles were obtained by casting the resulting solution. Their structure and optical properties were characterized by X‐ray photoelectron spectroscopy, wide‐angle X‐ray diffraction, thermogravimetry analysis, dynamic mechanical analysis, atomic force microscopy, transmittance electronic microscope, UV‐vis spectroscopy, and photoluminescence spectroscopy. The experimental results confirmed that the CdS nanocrystalline existed in the composite films, and cellulose matrix provided a confined medium for CdS particle growth in uniform size. The CdS/RC composites showed narrow emission in photoluminescence spectra, and their optical absorbance in the UV range was higher than that of the cellulose film without CdS. This work provided a simple method to prepare cellulose functional materials in NaOH/urea aqueous solution.

Photoluminescence of CdS/RC nanocomposites and TEM image of CdS nanocrystals dispersed in RC matrix.     

BR/CB/OMMT纳米复合材料的结构与性能研究

采用溶液插层法与双辊混炼法制备了顺丁橡胶/炭黑/有机蒙脱土（BR/CB/OMMT）纳米复合材料,用透射电子显微镜（TEM）以及X射线衍射（XRD）方法对复合材料的亚微观结构进行了表征,并研究了复合材料的力学特性、耐磨耗性能以及硫化特性。结果表明：BR/CB/OMMT为插层型纳米复合材料;在OMMT含量小于4份时,BR/CB/OMMT纳米复合材料具有优异的力学性能和耐磨耗性能;OMMT起到了硫化促进剂的作用,降低了BR的焦烧时间（TS）和正硫化时间（T90）;低填充量OMMT可提高复合材料的交联密度。     

Heat Induced Structure Modifications in Polymer‐Layered Silicate Nanocomposites

Summary: The success of the use of layered silicates in polymer nanocomposites, to improve physical and chemical properties is strictly related to a deeper knowledge of the mechanistic aspects on which the final features are grounded. This work shows the temperature induced structural rearrangements of nanocomposites based on poly[ethylene‐co‐(vinyl acetate)] (EVA) intercalated‐organomodified clay (at 3–30 wt.‐% silicate addition) which occur in the range between 75 and 350 °C. In situ high temperature X‐ray diffraction (HT‐XRD) studies have been performed under both nitrogen and air to monitor the modifications of the nanocomposite structure at increasing temperatures under inert/oxidative atmosphere. Heating between 75 and 225 °C, under nitrogen or air, causes the layered silicate to migrate towards the nanocomposite surface and to increase its interlayer distance. The degradation of both the clay organomodifier and the VA units of the EVA polymer seems to play a key role in driving the evolution of the silicate phase in the low temperature range. The structural modifications of the nanocomposites in the high temperature range (250–350 °C), depended on the atmosphere, either inert or oxidizing, in which the samples were heated. Heating under nitrogen led to deintercalation and thus a decrease of the silicate interlayer space, whereas exfoliation was the main process under air leading to an increase of the silicate interlayer space.

Heat induced structural modification of EVA‐clay nanocomposite under nitrogen and air.     

The effect of high temperature annealing process on crystallization process of polypropylene,mechanical properties,and surface quality of plastic parts

This work studied the effects and action mechanism of high‐temperature annealing process parameters, such as annealing temperature, annealing duration and cooling speed, on the microstructural evolution of polypropylene (PP) on different thickness layers, the surface quality, and mechanical properties of PP plastic parts. The results show that when the PP plastic parts are annealed at slightly higher than 100°C, the resin on the surface and internal layers of plastic parts just generates the relaxation and rearrangement at the molecular level. Only at an enough high annealing temperature, the secondary crystallization and phase transformation process can be observed. The crystallinity of all annealed samples is higher than that of unannealed samples, but the crystallinity is decreased with the increase of cooling speed after annealing duration, and the annealing duration exceeding 60 min almost has no effect on the crystallinity. The microstructural change of PP on the internal layer of plastic parts is weaker than that on the surface layer. The surface hardness of the plastic parts mainly depends on the crystallinity of the surface layer, whereas the surface roughness of the plastic parts depends on not only the crystallinity, but also the space conformation of molecular chains and the residual stress. With the change of annealing process parameters, the tensile and impact strengths of plastic parts show a non‐monotonic change law. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42773.     

Synthesis of amine‐cured,epoxy‐layered silicate nanocomposites: The influence of the silicate surface modification on the properties

Fluorohectorites were rendered organophilic through the cation exchange of sodium intergallery cations for protonated monoamine, diamine, and triamine oligopropyleneoxides and octadecylamine, benzylamine, and adducts of octadecylamine and benzylamine with diglycidyl ether of bisphenol A (DGEBA). The influence of the silicate surface modification and compatibility on the morphology and thermal and mechanical properties was examined. Surface modification with protonated octadecylamine and its adduct with DGEBA promoted the formation of microscale domains of silicate layers separated by more than 50 Å, as evidenced by transmission electron microscopy and wide‐angle X‐ray scattering. Young's modulus of these two nanocomposites increased parabolically with the true silicate content, whereas conventionally filled composites exhibited a linear relationship. The highest fracture toughness was observed for conventionally filled composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2643–2652, 2002     

Preparation and characterization of thermoplastic polyurethane/organoclay nanocomposites by melt intercalation technique: Effect of nanoclay on morphology,mechanical, thermal,and rheological properties

Nanocomposites based on thermoplastic polyurethane (TPU) and organically modified montmorillonite (OMMT) were prepared by melt blending. Organically modified nanoclay was added to the TPU matrix in order to study the influence of the organoclay on nanophase morphology and materials properties. The interaction between TPU matrix and nanofiller was studied by infrared spectroscopy. Morphological characterization of the nanocomposites was carried out using X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy techniques. The results showed that melt mixing is an effective process for dispersing OMMT throughout the TPU matrix. Nanocomposites exhibit higher mechanical and thermal properties than pristine TPU. All these properties showed an increasing trend with the increase in OMMT content. Thermogravimetric analysis revealed that incorporation of organoclay enhances the thermal stability of nanocomposites significantly. Differential scanning calorimetry was used to measure the melting point and the glass transition temperature (T_g) of soft segments, which was found to shift toward higher temperature with the inclusion of organoclays. From dynamic mechanical thermal analysis, it is seen that addition of OMMT strongly influenced the storage and loss modulus of the TPU matrix. Dynamic viscoelastic properties of the nanocomposites were explored using rubber process analyzer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

粘土/SBR/BIIR纳米复合材料的结构与性能

采用溴化丁基橡胶(BIIR)与粘土/SBR复合胶制备粘土/SBR/BIIR复合材料,并对其结构与性能进行研究.结果表明:粘土/SBR/BIIR并用胶为以BIIR为连续相、以SBR为分散相的海岛结构,并且粘土基本分散于SBR分散相中,所制备的复合材料为隔离型纳米复合材料;BIIR与SBR的相容性不好,热力学上基本不相容;...     

A Study on Structure and Mechanical Properties of Polyurethane/Organic-Montmorillonite Nanocomposites

The intercalated nanocomposites of polyurethane (PU) with organic-montmorillonite (OMMT) treated by cetryltrimethyl ammonium bromide was prepared. The interlayer spacing of PU/OMMT nanocomposites was 3–4 nm. The interface interaction of PU/OMMT nanocomposites was improved compared to that of PU/montmorillonite (MMT) composites. The orderly arrangement of the PU chains was hindered because of strong interface interaction between the silicate layers dispersed in the nanometer and PU chains. By adding 2 wt% OMMT to PU, tensile strength and tear strength of the PU/OMMT composites were increased from 10.5 MPa and 36.4 KN/m to 13.8 MPa and 42.2 KN/m, respectively. The tensile strength and tear strength increased with OMMT content firstly, reaching its maximum when the OMMT content was 8 wt%. After that, the tensile strength and tear strength decreased with the further increase of the OMMT content. Compared to that of PU, the elongation at break of the PU/OMMT nanocomposites increased, indicating that the stretch of PU/OMMT nanocomposites increased.     

Nano‐/Microscale Investigation of Tribological and Mechanical Properties of Epoxy/MWNT Nanocomposites

The effects of MWNT content and aspect ratio on the properties of epoxy‐based nanocomposites are investigated using nanoindentation and nanoscratch methods. The Halpin‐Tsai model for predicting the elastic modulus and hardness is modified to include the effective aspect ratio factor. The modified model predicts the experimental results more accurately. The frictional behavior is investigated and a new equation is proposed that correlates the ploughing friction with the plasticity index. The dispersion state of MWNTs and the surface features of residual grooves are investigated using scanning electron micrographs and AFM profiles. The mechanisms of improvements in the properties are also discussed.

     

Comparative Review on Structure,Properties, Fabrication Techniques,and Relevance of Polymer Nanocomposites Reinforced with Carbon Nanotube and Graphite Fillers

Owing to their remarkable electrical, mechanical, thermal, catalytic, and optical properties as well as their unique structure, carbon nanotubes and graphite have been exploited to produce high performance and multifunctional composites. The resultant composites are differentiated on the basis of their properties to meet various applications. In the framework of this review article, we have mainly focused on the preparation, structure, and properties of two families of composite materials with an emphasis on the differences between them. Moreover, the current challenges, future prospectives, and applications of carbon nanotubes- and graphite-based materials in sensors and in photovoltaic and energy storage devices (Li-ion battery) have been discussed.     

Structure and Property of PU/MMT Nanocomposites by In-Situ Polymerization

A montmorillonite modified by octadecylammonium salt (OMMT) was prepared. A polyurethane (PU)/montmorillonite nanocomposite was synthesized by in-situ polymerization using the OMMT, poly(propylene glycol), 4,4-diphenylmethylate diisocyanate, and 1,4-butanediol. The MMT platelets were dispersed in PU matrix on a 10 ～ 50 nm scale. Compared to that of pure PU, the tensile strength and tear strength of the PU/OMMT nanocomposites increased, respectively, and the MMT platelets dispersed on a nanometer scale enhanced the PU. The temperature of initial weight loss of the PU/OMMT nanocomposites was lower than that of pure PU because of the acid catalytic action of protonated MMT platelets in the first thermodegradation step. But its temperature of initial weight loss was higher than that of pure PU because of the barrier effect of the MMT platelets in the second thermodegradation step.     

尼龙1010三元纳米复合材料的结构与性能研究进展

论述了尼龙1010(PA1010)三元纳米复合材料的结构与性能的研究进展,对由两种填料共混改性r的PA1010复合材料的结构与性能,以及无机填料、弹性体等几类填充增韧增强体系及分散相形貌的研究进展进行了详细介绍。并指出PA1010复合材料的发展趋势是以三元共混为基础,获得高强度、高韧性的纳米填充材料分散性良好的PA1010复合材料。     

Effects of SiO2 nanoparticles on the performance of carboxyl‐randomized liquid butadiene–acrylonitrile rubber modified epoxy nanocomposites

The effects of SiO₂ nanoparticles on the performance of carboxyl‐randomized liquid butadiene–acrylonitrile rubber (CRBN) modified epoxy resin (EP) nanocomposites were studied. With the addition of an appropriate amount of SiO₂ (2%) to EP/CRBN (95/5), the nanocomposites could achieve the desired impact strength and modulus. The morphology of the nanocomposites was studied with scanning electron microscopy and transmission electron microscopy. The nanocomposites showed a three‐phase system; both the rubber particles and SiO₂ nanoparticles showed uniform dispersions in the EP matrix, with their phases all nanosized. A good correlation between the free‐volume hole radius and mechanical properties was found. The introduction of a small amount of nanoparticles (both rubber and SiO₂) into EP led to the formation of interactions between the EP and nanoparticles. The interactions restricted the segment motion and the mobilization of the EP chains and then reduced the free‐volume concentration in the amorphous region of EP. The fact that the average free‐volume hole radius of EP/CRBN was larger than that of pure EP was mainly attributed to the contribution of the larger size of the free‐volume holes within the rubber phase. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Polypropylene Blends with m-EPR Copolymers: Structure,Morphology and Thermal Properties

The effects of different contents of two metallocene propylene-based m-EPR elastomers on structure, morphology, thermal, and dynamic mechanical properties of the isotactic polypropylene/m-EPR blends were investigated. The both m-EPR copolymers have been built in isotactic polypropylene matrix as amorphous phase. However, the nucleation effect at lowest addition (2.5?vol%) and the solidification effect along with increased m-EPR’s additions have caused changes of the crystallinity degree and the size of spherulites in the isotactic polypropylene matrix. Higher degree of miscibility/compatibility of the isotactic polypropylene/m-EPR2, with lower viscosity has been observed. Homogeneous dispersion of m-EPR particles as well as their radial distribution has been observed.