Masterbatch-based multi-walled carbon nanotube filled polypropylene nanocomposites: Assessment of rheological and mechanical properties

Polypropylene (PP)/multi-wall carbon nanotubes (MWNTs) nanocomposites were prepared by diluting a PP/MWNT masterbatch by melt compounding with a twin screw extruder and prepared nanocomposites were characterized for their rheological, mechanical and morphological properties in terms of MWNT loading. The rheological results showed that the materials experience a fluid–solid transition at the composition of 2 wt.%, beyond which a continuous MWNT network forms throughout the matrix and in turn promotes the reinforcement. The tensile modulus and yield stress of the nanocomposites are substantially increased relative to the neat polypropylene. Nanotube reinforcement thus enhanced the yield stress, while reducing the ductility. The same behavior is observed in flexural tests. Charpy impact resistance of the notched samples increases slightly by the addition of MWNT, while impact resistance for the un-notched samples decreases with the addition of MWNTs. Finally, optimum in mechanical properties was observed at 2 wt.% MWNTs, which is near the rheological percolation threshold. From transmission electron microscopic (TEM) and scanning electron microscopy (SEM) images, it was observed that nanotubes are distributed reasonably uniformly indicating a good dispersion of nanotubes in the PP matrix. These results reveal that, preparation of nanocomposites from masterbatch dilution is an excellent method to obtain well-dispersed CNTs, while limiting the handling difficulties in plastics processing industrial workshops.     

Morphology,thermal and mechanical properties of PVC/MMT nanocomposites prepared by solution blending and solution blending + melt compounding

Two types of montmorillonite (MMT), natural sodium montmorillonite (Na-MMT) and organically modified montmorillonite (OMMT), in different amounts of 1, 2, 5, 10 and 25 phr (parts per hundred resin), were dispersed in rigid poly (vinyl chloride) by two different methods: solution blending and solution blending + melt compounding. The effects on morphology, thermal and mechanical properties of the PVC/MMT nanocomposites were studied by varying the amount of Na-MMT and OMMT in both methods. SEM and XRD analysis revealed that possible intercalated and exfoliated structures were obtained in all of the PVC/MMT nanocomposites. Thermogravimetric analysis revealed that PVC/Na-MMT nanocomposites have better thermal stability than PVC/OMMT nanocomposites and PVC. In general, PVC/MMT nanocomposites prepared by solution blending + melt compounding revealed improved thermal properties compared to PVC/MMT nanocomposites prepared by solution blending. Vicat tests revealed a significant decrease in Vicat softening temperature of PVC/MMT nanocomposites prepared by solution blending + melt compounding compared to unfilled PVC.     

Study on mechanical and ablative properties of EPDM/OMMT thermal insulating nanocomposites

In order to enhance the elongation at break, the ablation resistant properties as well as the tensile strength of the thermal insulating materials, organo-montmorillonite (OMMT) was introduced into the short aramid fibers reinforced Ethylene-Propylene-Diene Monomer (EPDM) based nanocomposites. The effects of OMMT content on the mechanical and ablative properties of the nanocomposites were investigated systematically. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirm that EPDM-matrix has been intercalated into OMMT interlayers after a mixing process on a two-roll mill. The brittle fracture of nanocomposites also indicates that OMMT can lubricate aramid fiber to weaken the interfacial adhesive strength between the fibers and the matrix. As a result, the tensile strength and elongation at break are both improved sharply with OMMT content increasing from 1 phr to 7 phr. However, thanks to the inevitable agglomeration of OMMT with high loading inside the nanocomposites, the tensile strength and elongation at break reduce gently once OMMT is over 7 phr. Furthermore, the ablation resistant properties are improved greatly by increasing OMMT from 1 phr to 11 phr. Therefore, the optimal content of OMMT is 7-11 phr for the thermal insulating nanocomposites with big elongation and excellent ablation resistant properties.     

挤出法乙丙橡胶/蒙脱土纳米复合材料制备和表征

采用一种新型的有机土蒙脱土(OMM T),通过熔融挤出法制备出了具有优异性能的乙丙橡胶/OMM T复合材料,并与炭黑补强体系进行了对比。透射电子显微镜考察表明,所制备的乙丙橡胶/OMM T纳米复合材料为剥离型结构;力学性能测试结果表明,当有机土含量仅为3份时,复合材料硫化胶的扯断强度是纯胶体系的5.2倍,比同量的高耐磨炭黑增强体系的硫化胶也提高了284%,与加入15份高耐磨炭黑的硫化胶相当;有机土体系撕裂强度也明显高于炭黑体系。还利用门尼黏度测试表征了材料的加工性能。     

聚丙烯/有机蒙脱土纳米复合材料的制备及性能

以马来酸酐接枝低分子量的聚丙烯(M APP)为相容剂,采用熔融插层法,制备了聚丙烯(PP)/有机蒙脱土(OMM T)纳米复合材料;采用微机控制电子万能试验机、悬臂梁冲击试验机研究了复合材料的力学性能;采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和偏光显微镜(POM)等对复合材料的微观结构进行了研究。结果表明,熔融插层法能够获得较好的插层效果,适量蒙脱土的加入使聚丙烯的球晶数量增多,球晶尺寸变小;复合材料的拉伸强度和冲击强度都是先增加后降低,总体上来说,拉伸强度高于纯聚丙烯,冲击强度与纯聚丙烯相近。     

聚合物包覆型纳米片层粒子对氢化丁腈橡胶复合材料性能的影响

制备了一系列不同量的剥离型有机蒙脱土(OMMT)与氢化丁腈橡胶(HNBR)复合的纳米材料,探究了OMMT的含量对HNBR复合材料力学、热力学性能的影响。采用广角X射线衍射(XRD)、差示扫描量热分析(DSC)、热重分析、傅里叶变换红外光谱、透射电镜对OMMT的结构与性能进行了表征。并对HNBR/OMMT复合材料的结构与性能进行了分析。XRD结果表明OMMT是完全剥离且由聚氨酯大分子链包覆的纳米片层粒子;DSC结果证明OMMT中的活性双键能发生反应。加入单片层OMMT后,HNBR纳米复合材料的力学性能、热力学性能以及动态性能都有所提高。且3phr的OMMT能使复合材料的耐磨性提高了24.7%,硬度、拉伸强度、撕裂强度等达到最大值。     

熔融插层制备聚苯乙烯/蛭石纳米复合材料的结构与性能研究

通过熔融插层法制备了聚苯乙烯(PS)/蛭石纳米复合材料,测试了复合材料的力学性能、燃烧性能和熔体流动速率,并对不同蛭石含量的PS/蛭石纳米复合材料进行了对比。结果表明,当蛭石含量为3%时,与纯PS相比,熔体流动速率只降低了4%,即仍具有良好的加工性能,同时拉伸强度、断裂伸长率和缺口冲击强度分别提高了3.4%、77%和41%。氧指数测试结果表明,蛭石的加入有利于提高材料的阻燃性能。     

Biodegradable poly(propylene carbonate)/montmorillonite nanocomposites prepared by direct melt intercalation

Intercalation-exfoliated nanocomposites derived from poly(propylene carbonate) (PPC) and organo-modified montmorillonite (OMMT) were prepared by direct melt blending in an internal mixer. The nano-scale dispersion of the OMMT layers within the PPC matrix was verified using wide angle X-ray scattering and transmission electron microscopy technologies. Static mechanical properties were determined by using a tensile tester. The PPC/OMMT nanocomposites with lower OMMT content showed an increase in thermal decomposition temperature when compared with both pure PPC and the composites prepared from un-modified MMT. Dynamic mechanical analysis indicated that nano-scale OMMT dispersed well within PPC matrix and therefore enhanced the storage modulus of the composites.     

Preparation and characterization of poly(methyl methacrylate)-clay nanocomposites via melt intercalation: Effect of organoclay on thermal, mechanical and flammability properties

The PMMA nanocomposites were prepared by melt processing method. The influence of organoclay loading on extent of intercalation, thermal, mechanical and flammability properties of poly(methyl methacrylate) (PMMA)-clay nanocomposites were studied. Three different organoclay modifiers with varying hydrophobicity (single tallow vs. ditallow) were investigated. The nanocomposites were characterized by using wide angle X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. The intercalation of polymer chain within the silicate galleries was confirmed by WAXD and TEM. Mechanical properties such as tensile modulus (E), tensile strength, percentage elongation at break and impact strength were determined for nanocomposites at various clay loadings. Overall thermal stability of nanocomposites increased by 16-17 °C. The enhancement in T_g of nanocomposite is merely by 2-4 °C. The incorporation of maleic anhydride as compatibilizer further enhanced all the properties indicating improved interface between PMMA and clay. The flammability characteristics were studied by determining the rate of burning and LOI.     

Experimental and theoretical analyses of mechanical properties of PP/PLA/clay nanocomposites

Compatibilized and non-compatibilized blends of polypropylene (PP) and poly(lactic acid) (PLA) with various compositions containing nanoclay particles were prepared by one step melt compounding in a twin screw extruder. Two nanocomposite systems with different matrices i.e. PP-rich (75/25 composition) containing Cloisite 15A and PLA-rich (25/75 composition) containing Cloisite 30B were selected for investigation of effect of nanoclays and n-butyl acrylate glycidyl methacrylate ethylene terpolymers (PTW) as compatibilizer on mechanical properties of PP/PLA/clay nanocomposites. Tensile and impact properties of the nanocomposite systems were investigated and correlated with their microstructures. Tensile modulus and strength of the blends were increased while elongation at break decreased by increasing PLA content. There was an irregular relationship between impact strength of the blends and PLA content. Several proposed models for blends and nanocomposites were used for prediction of tensile modulus of the samples. Most of the proposed models for blends could predict the tensile modulus of the blends successfully at low content of PLA. Another notable point was that most of the micromechanical models for nanocomposites fitted well to experimental values at low content of the clays and showed deviations at high clay loadings.     

Effect of organoclay platelets on morphology and properties of LLDPE/EMA blends

Blends of linear low density polyethylene (LLDPE) and ethylene-co-methyl acrylate (EMA) and their nanocomposites with two types of modified montmorillonite (organoclay) were explored in order to achieve an improved balance between stiffness and toughness. The nanocomposites were prepared in a HAAKE RHEOMIX at three different mixing sequences. The compression molded nanocomposites were utilized to evaluate the morphology and the properties like mechanical, dynamic mechanical and thermal. The results reveal that the morphology and the properties of the nanocomposites are dependent on the blending sequence as well as the type of nanoclay used. The addition of organoclay slightly increases the tensile modulus for all the nanocomposites. On the other hand, a drastic improvement of the impact strength was observed when the organoclay located at the dispersed EMA phase. The effects of clay concentration on the properties of the nanocomposites were also studied. The optimum dispersion as well as property was found for the nanocomposite at 5 wt% of the nano clay.     

Isothermal crystallization behavior and mechanical properties of polylactide/carbon nanotube nanocomposites

Carbon nanotube (CNT)–reinforced polylactide (PLA) nanocomposites were prepared using a melt compounding process employing a twin-screw extruder. The isothermal crystallization kinetics of PLA/CNT nanocomposites according to Avrami’s theory were analyzed using differential scanning calorimetry in the temperature range 90–120 °C. There was a significant dependence of CNT on the crystallization behavior of the PLA matrix. The incorporation of CNT improved effectively the crystallization rate of PLA/CNT nanocomposites through heterogeneous nucleation. The nucleating effect of CNTs which increased the number of nucleation sites and decreased the average spherulite size was confirmed using polarized optical microscopy. The rheological properties of the PLA/CNT nanocomposites were also investigated. Changes in the microstructure of the PLA/CNT nanocomposites occurred by incorporating CNT. Furthermore, the tensile strength/modulus and thermal stability of PLA/CNT nanocomposites were enhanced when a very small quantity of CNT was added. This research accounts for the effect of CNTs, which significantly influenced the isothermal behavior, thermal stability, mechanical, and rheological properties of the PLA/CNT nanocomposites, providing a design guide for PLA/CNT nanocomposites in industrial fields.     

Morphological and structural characterization of PHBV/organoclay nanocomposites by small angle X-ray scattering

In this work, the morphological and structural behaviors of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposites were investigated using small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The nanocomposites with 1, 3 and 5 wt.% of organically modified montmorillonite Cloisite® 30B (OMMT) were prepared by melt processing in a twin screw extruder using two different processing conditions (low and high shear intensity). The lamellar long period of the polymer was lower for the nanocomposites, with high polydispersity values. However, the crystalline thickness increased with the clay content and was independent of the processing conditions. This behavior resulted in a high linear crystallinity of the nanocomposites with 3 and 5 wt.% OMMT. The disruption factor (β) was in agreement with the WAXD and TEM findings, indicating a good dispersion of the nanoparticles in the PHBV matrix with 3 wt.% of OMMT during the high shear intensity of melt processing.     

固相剪切碾磨对Al/低密度聚乙烯导热复合材料结构与性能的影响

采用固相剪切碾磨预处理结合熔融再加工技术制备了高性能铝粉(Al)/线性低密度聚乙烯(LLDPE)导热复合材料,并与常规熔融共混法对比,系统研究了固相剪切碾磨对复合材料微观形态、结晶性能、热稳定性、流变特性、热导率和力学性能等的影响。结果表明:通过固相剪切碾磨实现了球形Al颗粒应力诱导变形为具有较大径厚比的片状,在基体中均匀分散且与其界面结合得以增强,同时这种大片状的铝粉在Al/LLDPE复合材料成型时更易有效接触形成导热网链并形成一定取向分布,特别是在高填充量下。因此Al/LLDPE复合材料拥有更好的结晶性能和热稳定性、更低的流变逾渗阈值、更高的热导率和力学性能。固相剪切碾磨预处理制备的Al/LLDPE复合材料在铝粉含量超过15%就出现流变逾渗现象,且当Al填充质量分数80%时,复合材料的热导率高达8.86 W/(m·K),拉伸强度和弯曲强度分别为33.0 MPa和31.2 MPa,都明显优于常规熔融共混复合体系,同时其初始分解温度也提高了近13℃。     

The mechanical and viscoelastic properties of SSBR vulcanizates filled with organically modified montmorillonite and silica

The mechanical and the dynamic rheological behavior of solution-polymerized styrene butadiene rubber (SSBR) filled with compounding fillers organic montmorillonite (OMMT)/silica (SiO₂) were studied. The mechanical properties of the vulcanizates could be improved by incorporation of low OMMT contents, and the best reinforcement effect appeared when 7 phr (parts per hundred rubber) OMMT was added. Moreover, due to the formation of the exfoliated silicate platelet in the matrix, a strong cooperative reinforcement effect to the vulcanizate could be gained for the vulcanizate containing 7 phr OMMT and 20 phr SiO₂. Incorporation of SiO₂ up to 50 phr to the vulcanizates with or without OMMT resulted in marked reinforcement effect, and the best mechanical properties were obtained for 7 phr OMMT filled composites. On the other hand, compounding fillers OMMT/SiO₂ significantly influences the dynamic mechanical behavior of the vulcanizates. It was found that the compounding filler with a certain composition facilitated preparing SSBR vulcanizates with optimized wet traction, rolling resistance, and strength properties.     

Effect of fiber loading on mechanical and morphological properties of cocoa pod husk fibers reinforced thermoplastic polyurethane composites

In this study, cocoa (Theobroma cacao) pod husk (CPH) fiber reinforced thermoplastic polyurethane (TPU) was prepared by melt compounding method using Haake Polydrive R600 internal mixer. The composites were prepared with different fiber loading: 20%, 30% and 40% (by weight), with the optimum processing parameters: 190 °C, 11 min, and 40 rpm for temperature, time and speed, respectively. Five samples were cut from the composite sheet. Mean value was taken for each composite according to ASTM standards. Effect of fiber loading on mechanical (i.e. tensile, flexural properties and impact strength) and morphological properties was studied. TPU/CPH composites showed increase in tensile strength and modulus with increase in fiber loading, while tensile strain was decreasing with increase in fiber loading. The composite also showed increase in flexural strength and modulus with increase in fiber content. Impact strength was deteriorated with increase in fiber loading. Morphology observations using Scanning Electron Microscope (SEM) showed fiber/matrix good adhesion.     

Characterization and mechanical properties of polyacrylonitrile/silica composite fibers prepared via dry-jet wet spinning process

Polyacrylonitrile (PAN)/silica composite fibers were fabricated by dry-jet wet spinning process. PAN/silica composite fibers were characterized with SEM and FTIR. The former revealed that beads were formed and aggregated when silica content was more than 1 wt.%, while the latter confirmed the presence and increment of silica content. The tensile test was performed to obtain the mechanical properties of PAN/silica composite fibers, which showed an optimum Young's modulus at 5.94 GPa and tensile strength at 1.07 MPa at 1 wt.% silica. Therefore, the addition of silica particle at 1 wt.% has enhanced the mechanical properties of PAN/silica composite fibers.     

Mechanical and Antibacterial Properties of Injection Molded Polypropylene/TiO2 Nano-Composites:Effects of Surface Modification

Polypropylene (PP)/titanium dioxide (TiO2) nano-composites were prepared by melt compounding with a twin screw extruder. Nanoparticles were modified prior to melt mixing with maleic anhydride grafted styrene-ethylene-butylene-styrene (SEBS-g-MA) and silane. The composites were injection molded and mechanical tests were applied to obtain tensile strength, elastic modulus and impact strength. Antibacterial efficiency test was applied on the injection molded composite plaques by viable cell counting technique. The results showed that the composites including SEBS-g-MA and silane coated TiO2 gave better mechanical properties than the composites without SEBS-g-MA. Antibacterial efficiency of the composites varied according to the dispersion and the concentration of the particles and it was observed that composites at low content of TiO2 showed higher antibacterial property due to the better photocatalytic activity of the particles during UV exposure.     

Compatibilized Polypropylene/Ethylene–Propylene–Diene-Monomer/Polyamide6 ternary blends: Effect of twin screw extruder processing parameters

Polypropylene (PP)/Polyamide6 (PA6)/Ethylene–Propylene–Diene-Monomer (EPDM) (70/15/15) ternary polymer blends compatibilized with Maleic-anhydride grafted EPDM (EPDM-g-MA) were prepared by melt blending using a twin screw extruder (TSE). Effect of TSE processing parameters including barrel temperature, screw speed and blending sequence on the mechanical properties of ternary polymer blends was investigated by application of Taguchi experimental design methodology. Three different levels of barrel temperature (220 °C, 230 °C, 240 °C), screw speed (90 rpm, 120 rpm, 150 rpm) and blending sequence (nominated as: S1, S2 and S3) were selected. The response variables were tensile properties and impact strength of the prepared samples which are directly affected by the blend microstructure. Investigation of the statistical–mathematical analysis results performed by the software depicted that the optimum processing conditions for the ternary blends investigated here, to achieve balanced tensile and impact properties, are 220 °C, 150 rpm and S2 blending sequence.     

Preparation and characterisation of polyamide 11/montmorillonite (MMT) nanocomposites for use in angioplasty balloon applications

With increased demands on catheter balloon functionality, there is an emphasis to blend new materials which can improve mechanical performance. Polymer nanocomposites were prepared by melt blending polyamide 11 (PA 11) with organically modified montmorillonite nanoclay. The effects of incorporating the nanoclay on the short-term mechanical properties of PA 11 were assessed using a design of experiments (DoEs) approach. X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis techniques (DMA) were used to characterise the morphology of the nanocomposites. Design of experiments studies revealed that the optimum nanocomposites properties can be achieved by carefully controlling the melt compounding parameters. XRD and TEM data proved that exfoliated clay morphologies existed within the matrix at low clay loading (2%). Whereas the interaction between the polymer matrix and nanoclay was quantified in the DMA spectra, showed a significant increase in storage modulus (up to 80%). The reinforcing effect of nanoclay within the PA 11 was further investigated using mechanical testing, where significant increases in the ultimate tensile strength and strain at break of reinforced tri-layer balloon tubing were observed.