Preparation and properties of melt‐blended polylactic acid/polyethylene glycol‐modified silica nanocomposites

One commercial type of fumed silica modified with methoxy polyethylene glycol (mPEG) plasticizer was incorporated into polylactic acid (PLA) biobased polymer to improve its performance. The modification on silica was confirmed through Fourier transform infrared spectra, nuclear magnetic resonance, and TGA assessments. The grafting percentage of mPEG onto silica was about 19.8 wt %. Transmission electron microscope revealed a similar degree of dispersion for control silica and modified silica‐filled PLA nanocomposites. Not much difference in the glass transition temperatures at various silica contents was found for PLA/control silica systems from the differential scanning calorimetry measurement, but the glass transition temperature of PLA/modified silica nanocomposite at 10 phr of modified silica showed up to 11°C decrement. It was suggested that the mPEG plasticizer efficiently plasticized the PLA matrix through the enhanced segmental mobility of PLA chains. Young's modulus of PLA was about 2133 ± 53 MPa, and the value for the nanocomposite increased to 2547 ± 54 MPa at 10 of phr control silica mainly due to the reinforcing effect from nanoparticles. For modified silica, Young's modulus decreased at various silica contents. The elongation at break for modified silica‐filled cases was higher than that of control silica‐filled cases. These results were attributed to the plasticizing effect of surface modifier. Optical transmittance for pristine PLA was generally in a similar order as PLA/control silica and modified silica cases at various silica contents. The results agreed with the morphology observation as well. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of extruded melt‐mixed polypropylene/montmorillonite nanocomposites with inline monitoring

This article advances the use of an inline optical detector to monitor the disaggregation of the montmorillonite (MMT) clay tactoids during the preparation of polypropylene (PP)/MMT nanocomposites via polymer melt compounding. During the exfoliation of the tactoids their size are reduced below the minimum particle size to produce light extinction and so, the signal of the inline detector reduces as the nanosize composite is formed. The measurement is done at the transient state with the MMT clay added as a pulse with constant weight into the PP extrusion melt flow and followed by the optical detector. The data comes out as the common residence time distribution curves having its maximum intensity related to the tactoids average particle size, keeping all other variables constants. The light extinction was measured for composites with different clays (Cloisite® 15A, 30B, Na⁺, and Sintered 20A) using the same PP grafted with maleic anhydride compatibilizer. The dissaglomeration/exfoliation efficiency increases as: ‘‘Sintered 20A’’ < ‘‘Na+ clay’’ < ‘‘organo‐modified clay’’ < ‘‘organo‐modified clay + compatibilizer’’. The best result is obtained using Cloisite® 15A and Cloisite® 20A following the expected reduction of the particle size obtained during a nanocomposite melt processing. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Linear and nonlinear melt‐state viscoelastic properties of polypropylene/organoclay nanocomposites

Rheological behavior of polypropylene (PP)/organoclay nanocomposites varying in compatibilizer (PP‐g‐MA) and organoclay concentration was investigated. The samples were prepared by melt intercalation method in an internal mixer. The wide angle X‐ray diffraction patterns and results of rheological measurements showed that the compatibilizer had strong influence in increasing the interlayer spacing. The observed low frequency liquid‐like to solid‐like transition and apparent yield stress in simple shear flows, along with convergence of transient shear stress to nonzero values in stress relaxation after the cessation of flow experiments, were found to be consistent with formation of a physical network in quiescent conditions which could be easily ruptured with applying low shear rates. The values of stress overshoot strain in flow reversal experiments were independent of shear rate, organoclay, and compatibilizer content. From the results of frequency sweep experiments in different nonlinear strain amplitudes it was shown that extended Cox‐Merz analogy was valid in nonlinear dynamic deformations while the shear viscosity showed positive deviation from this analogy with higher deviations at lower shear rates. Results of storage modulus recovery and flow reversal experiments at different shear rates suggested that network structure is reformed with a much slower rate compared to the rotational relaxation of organoclay platelets. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Preparation and properties of chlorosulfonated polyethylene/organomontmorillonite nanocomposites

Chlorosulfonated polyethylene (CSPE)/organomontmorillonite (OMMT) nanocomposites were prepared by a melt intercalation method. The microstructure of the nanocomposites was characterized by transmission electron microscopy and X‐ray diffraction. The effects of the OMMT content on the mechanical properties and swelling behavior of the nanocomposites were investigated. The improvement in the thermal stability of the nanocomposites was determined by thermogravimetric analysis. Transmission electron microscopy and X‐ray diffraction showed that CSPE was intercalated into OMMT. When the OMMT content was lower than 12 wt %, the nanocomposites showed excellent tensile properties, which was attributed to nanometer‐scale dispersion. The introduction of a small amount of OMMT also improved the thermal stability and swelling behavior, which was attributed to the gas barrier action of the OMMT layers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of polyimide/silica hybrid nanocomposites

In this study, a commercially available nano‐sized silica (SiO₂) was surface‐modified via esterification with oleic acid (OA), a relatively inexpensive and hydrophobic modifier. The surface‐modified silica (SiO₂‐OA) nanoparticles were used to disperse in the poly(amic acid) solutions of a commercial polyimide (PI), used for two‐layer film, and thermally imidized to form a series of PI/silica nanocomposites. The effects of the addition of SiO₂‐OA nanoparticles on the properties of the as‐prepared PI/silica nanocomposites were studied. The results indicated that the as‐prepared PI/silica nanocomposites exhibited improvements in the dynamic mechanical property, thermal stability, water resistance, and thermal expansion. POLYM. COMPOS. 28:575–581, 2007. © 2007 Society of Plastics Engineers     

PA11/白炭黑纳米复合材料的制备及性能研究

以11-氨基十一酸和湿态白炭黑为原料,通过原位聚合的方法制备了尼龙11/白炭黑纳米复合材料,并用红外光谱仪和扫描电子显微镜等研究了纳米复合材料的形态结构、力学性能和阻隔性能。结果显示,当白炭黑含量增加时,拉伸强度和弯曲强度先显增大趋势;当白炭黑质量分数达到8%时,拉伸、弯曲强度达到最大值;之后,拉伸、弯曲强度开始减小。断裂伸长率则一直减小,无明显变化。尼龙11及其纳米复合材料的常温冲击强度也随着白炭黑含量的增加逐渐降低。此外,白炭黑的加入极大地提高了复合材料的阻隔性能。     

Preparation and properties of polylactide–silica nanocomposites

Poly(lactic acid) (PLA)/SiO₂ nanocomposites were prepared via melt mixing with a Haake mixing method. To improve the dispersion of nanoparticles and endow compatibility between the polymer matrix and nanosilica, SiO₂ was surface‐modified with oleic acid (OA). The interfacial adhesion of the PLA nanocomposites was characterized by field‐emission scanning electron microscopy. The storage modulus and glass‐transition temperature values of the prepared nanocomposites were measured by dynamic mechanical thermal analysis. The linear and nonlinear dynamic rheological properties of the PLA nanocomposites were measured with a parallel‐plate rheometer. The effects of the filling content on the dispersability of the OA–SiO₂ nanoparticles in the PLA matrix, the interface adhesion, the thermomechanical properties, the rheological properties, and the mechanical properties were investigated. Moreover, the proper representation of the oscillatory viscometry results provided an alternative sensitive method to detect whether aggregation formed in the polymeric nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of calcium carbonate/low‐density‐polyethylene nanocomposites

Calcium carbonate/low‐density‐polyethylene (LDPE) nanocomposites have been prepared by melting blend with twin‐screw extruder. The mechanical properties of composites and the dispersion of the nanoparticles were studied. The reinforcement mechanism was discussed. The results show that not only the tensile property but also the flexural modulus of the system have been evidently increased by the addition of calcium carbonate. The calcium carbonate particles have been dispersed in the matrix in the nanometer scale. The reinforcement mechanism of the calcium carbonate lies on that the calcium carbonate particles, acting as hetero‐nuclei, can induce higher crystallinity at the matrix‐particle interface compared to regions away from the interface. Consequently, in the process of the tensile test, the nanocomposites have better tensile yield strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Electrical and mechanical properties of acrylonitrile‐butadiene‐styrene/multiwall carbon nanotube nanocomposites prepared by melt‐blending

The electrical properties in polymer/carbon nanotube (CNT) nanocomposites are governed not only by the degree of dispersion but also to a greater extent on the aspect ratio of the CNTs in the final composites. Melt‐mixing of polymer and CNTs at high shear rate usually breaks the CNTS that lowers the aspect ratio of the nanotubes. Thus, homogeneous dispersion of CNTs while retaining the aspect ratio is a major challenge in melt‐mixing. Here, we demonstrate a novel method that involves melt‐blending of acrylonitrile‐butadiene‐styrene (ABS) and in situ polymerized polystyrene (PS)/multiwalled CNT (MWCNT) nanocomposites, to prepare electrically conducting ABS/MWCNT nanocomposites with very low CNT loading than reported. The rationale behind choosing PS/MWCNT as blending component was that ABS is reported to form miscible blend with the PS. Thus, (80/20 w/w) ABS/(PS/MWCNT) nanocomposites obtained by melt‐blending showed electrical conductivity value ≈1.27 × 10^?6 S cm^?1 at MWCNT loading close to 0.64 wt %, which is quite lower than previously reported value for ABS/MWCNT system prepared via solution blending. Scanning electron microscopy and differential scanning calorimetry analysis indicated the formation of homogenous and miscible blend of ABS and PS. The high temperature (100°C) storage modulus of ABS (1298 MPa) in the nanocomposites was increased to 1696 MPa in presence of 0.64 wt % of the MWCNT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Pyrolysis studies of polyethylene terephthalate/silica nanocomposites

The decomposition of pure polyethylene terephthalate (PET) and PET/silica nanocomposites was investigated by thermal gravimetry (TG) and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). The influence of the nanosized silica on the pyrolysis properties of the composites was found from the results that the activation energies of decomposition and the residual carbon content increase with silica nanoparticles. It is deduced that the increase of the activation energies and the residual carbon content result from the adsorption of the decomposed products on the surface of silica. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of silica/polyurethane nanocomposites by UV‐induced polymerization from surfaces of silica

UV‐curable nanocomposites were prepared by the in situ photopolymerizaton with nanosilica obtained from sol–gel process. The photoinitiator 2‐hydroxy‐2‐methyl‐1‐phenylpropane‐1‐one (1173) was anchored onto the surface of the nanosilica with or without methacryloxypropyltrimethoxysilane (MAPS) modification. The photopolymerization kinetics was studied by real‐time Fourier transform IR (RTIR), and the microstructure and properties of the nanocomposite were investigated using transmission electron microscopy and UV–visible (UV–vis) transmistance spectra. RTIR analysis indicated that the nanocomposites without MAPS had higher curing rates and final conversion than those with MAPS. The nanocomposites with an uniformal dispersion of nanosilica had high UV–vis transmittance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

PMMA‐grafted‐silica/PVC nanocomposites: Mechanical performance and barrier properties

Poly(vinyl chloride) (PVC)/SiO₂ nanocomposites were prepared via melt mixture using a twin‐screw mixing method. To improve the dispersion degree of the nanoparticles and endow the compatibility between polymeric matrix and nanosilica, SiO₂ surface was grafted with polymethyl methacrylate (PMMA). The interfacial adhesion was enhanced with filling the resulting PMMA‐grafted‐SiO₂ hybrid nanoparticles characterized by scanning electron microscopy. Both storage modulus and glass transition temperature of prepared nanocomposites measured by dynamic mechanical thermal analysis were increased compared with untreated nanosilica‐treated PVC composite. A much more efficient transfer of stresses was permitted from the polymer matrix to the hybrid silica nanoparticles. The filling of the hybrid nanoparticles caused the improved mechanical properties (tensile strength, notched impact strength, and rigidity) when the filler content was not more than 3 wt %. Permeability rates of O₂ and H₂O through films of PMMA‐grafted‐SiO₂/PVC were also measured. Lower rates were observed when compared with that of neat PVC. This was attributed to the more tortuous path which must be covered by the gas molecules, since SiO₂ nanoparticles are considered impenetrable by gas molecules. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of melt‐blended graphene nanosheets–poly(vinylidene fluoride) nanocomposites with enhanced properties

Nanocomposites of poly(vinylidene fluoride) (PVDF) with chemically reduced graphene nanosheets (GNs) were prepared by melt mixing method and their structure and morphology characterized by SEM analysis. The addition of GNs in the PVDF matrix resulted in changes of the crystallization and melting behaviors. Furthermore, increasing GNs content led to improved thermal stability of the PVDF nanocomposites in air and nitrogen, as well as significant increase in tensile and flexural properties. The nanocomposites' rheological behavior is also affected by the GNs' content. Using oscillatory rheology to monitor the GNs' dispersion, it was found that as the GNs loading increase, the Newtonian behavior disappears at low frequency. This suggests a viscoelastic behavior transition from liquid‐like to solid‐like, with greater GNs content and more homogeneous dispersion resulting in a stronger solid‐like and nonterminal behavior. By using the melt mixing method to disperse GNs, the properties of PVDF are enhanced due to the better dispersion and distribution of GNs throughout the matrix. This improvement could broaden the applications for PVDF nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of polypropylene nanocomposites by melt‐mixing: Comparison between three organoclays

Polypropylene (PP)‐based nanocomposites reinforced with three different organoclays (Dellite^© 67 G, Cloisite^© 20, and Cloisite^© 30B) were prepared via melt‐mixing in an internal mixer. The three organoclays differ essentially via their organic modifier and interlamellar distance. The nanocomposites microstructure was characterized at different scales through scanning electron microscopy (SEM) observations, X‐ray diffractometry, and rheological measurements. The influence of processing parameters such as rotor speed and mixing time was quantified. The results show that Dellite^© 67 G and Cloisite^© 20 present a good dispersion state, with an intercalation of the tactoids by the polymer chains and a good level of exfoliation. In contrast, whatever the processing conditions, Cloisite^© 30B was not dispersed correctly in the matrix, showing neither intercalation nor exfoliation, even in the presence of compatibilizer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45053.     

Microstructure,crystallization and dynamic mechanical properties of polyamide/clay nanocomposites after melt‐state annealing

Polyamide 6/clay (PA/clay) nanocomposites produced by melt‐compounding were treated under various melt‐state annealing processes. The effect of melt‐state annealing on the microstructure, crystallization, and dynamic mechanical properties was characterized by transmission electron microscope (TEM), modulated differential scanning calorimetry (MDSC), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and dynamic mechanical analysis (DMA). Clay layers were exfoliated in PA matrix. The crystalline transformation between α and γ‐crystalline phase was virtually dependent on the annealing process and clay loading. After melt‐state annealing between 230 and 250°C, clay induced the appearance of a new endothermic peak in PA/clay. PA/clay after melt‐state annealing exhibited a higher elastic modulus above T_g and a lower β relaxation below T_g as compared with the non‐annealed sample. FTIR analysis demonstrated that the melt‐state annealing caused strong hydrogen bonding interaction of amide groups with clay layers. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Crystalline forms in melt‐crystallized syndiotactic polystyrene/clay nanocomposites

X‐ray diffraction methods and polarized optical microscopy have been used to investigate the structural change of syndiotactic polystyrene/clay nanocomposites. The nanocomposite has prepared by mixing an sPS polymer solution with organically modified montmorillonite. Both X‐ray diffraction and transmission electron microscopy results indicate that most of the swellable silicate layers are exfoliated and randomly dispersed into the sPS matrix. The X‐ray diffraction data also show the presence of polymorphism in sPS/clay nanocomposites, which is strongly dependent on the thermal history of the nanocomposites from the melt and on the content of clay. In this study, the effect of premelting temperatures and crystallization temperatures of sPS and sPS/clay nanocomposites on their crystalline phases is discussed.     

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     

Preparation and properties of polyethylene/montmorillonite nanocomposites formed via ethylene copolymerization

BACKGROUND: In situ formation of polyethylene/clay nanocomposites is one of the prevalent preparation methods that include also solution blending and melt blending with regard to process simplification, economy in cost, environment protection and marked improvement in the mechanical properties of the polymeric matrix. In the work reported here, the preparation of linear low‐density polyethylene (LLDPE) and fabrication of polymer/clay nanocomposites were combined into a facile route by immobilizing pre‐catalysts for ethylene oligomerization on montmorillonite (MMT). RESULTS: [(2‐ArN?C(Me))₂C₅H₃N]FeCl₂ (Ar = 2,4‐Me₂(C₆H₃)) was supported on MMT treated using three different methods. The MMT‐supported iron complex together with metallocene compound rac‐Et(Ind)₂ZrCl₂ catalyzed ethylene to LLDPE/MMT nanocomposites upon activation with methylaluminoxane. The oligomer that was formed between layers of MMT promoted further exfoliation of MMT layers. The LLDPE/MMT nanocomposites were highly stable upon heating. Detailed scanning electron microscopy analysis revealed that the marked improvement in impact strength of the LLDPE/MMT nanocomposites originated from the dispersed MMT layers which underwent cavitation upon impact and caused plastic deformation to absorb most of the impact energy. In general, the mechanical properties of the LLDPE/MMT nanocomposites were improved as a result of the uniform dispersion of MMT layers in the LLDPE matrix. CONCLUSION: The use of the MMT‐supported iron‐based diimine complex together with metallocene led to ethylene copolymerization between layers of MMT to form LLDPE/MMT nanocomposites. The introduction of exfoliated MMT layers greatly improved the thermal stability and mechanical properties of LLDPE. Copyright © 2009 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。     

Effect of polyethylene glycol on the properties of styrene‐butadiene rubber/organoclay nanocomposites filled with silica and carbon black

Polyethyene glycol (PEG) is widely used as a dispersing agent and can also be used to prevent the adsorption of ingredients on the surface of silica. From the XRD results, PEG that was used as the dispersing agent on the SBR/organoclay compound filled with silica and carbon black (CB) was intercalated between the organoclay layer. Additionally, the interactions with the PEG differed depending on whether 3‐aminopropyltriethoxysilane (APTES) or N,N‐dimethyldodecylamine (DDA) were used as clay modifiers. When PEG was added, the T_g of the SBR/silica/APTES‐MMT compound increased through the formation of hydrogen bonds between the ether linkages of PEG and the hydroxyl groups of APTES. For the SBR/silica/DDA‐MMT compound with PEG, slippage occurred between the silicate, and DDA because of the alkyl chain of DDA. The SBR/silica/APTES‐MMT/CB compound with PEG exhibited the highest T_g value and the highest bound rubber content, with high modulus values at 100 and 300%. The SBR/silica/DDA‐MMT/CB compound had the best properties in terms of the wet skid resistance and the rolling resistance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011