Morphological aspects of injected polypropylene/clay nanocomposite materials

Polypropylene (PP) clay nanocomposites were injection‐molded using two different coupling agents based on maleic anhydride‐grafted PP (MA‐g‐PP) and two clay loadings. The morphological aspects of these materials were studied by depth profiling. Molecular chain and clay orientations were characterized using attenuated total reflectance‐infrared analysis and transmission electron microscopy (TEM). Both clay platelets and PP molecular chain orientations were found to decrease from the surface toward the core of the injection–molded specimens. Clay intercalation, characterized by both complementary X‐ray diffraction and TEM, was found to be significantly influenced by both the characteristics of the coupling agent used and the type of residual stresses generated at each layer across the thickness of the injection‐molded parts. The use of low‐molecular weight (M_w) MA‐g‐PP led to a uniform intercalation but with no further exfoliation. The use of higher molecular weight MA‐g‐PP led to a heterogeneous intercalation with some signs of exfoliation. The crystallization behavior of PP clay nanocomposites studied by differential scanning calorimetry showed an increase in the level of crystallinity from the surface to the core of the specimens; these results were also confirmed by scanning electron microscopy. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

The effect of clay type and of clay–masterbatch product in the preparation of polypropylene/clay nanocomposites

Clay containing polypropylene (PP) nanocomposites were prepared by direct melt mixing in a twin screw extruder using different types of organo‐modified montmorillonite (Cloisite 15 and Cloisite 20) and two masterbatch products, one based on pre‐exfoliated clays (Nanofil SE 3000) and another one based on clay–polyolefin resin (Nanomax‐PP). Maleic anhydride‐grafted polypropylene (PP‐g‐MA) was used as a coupling agent to improve the dispersability of organo‐modified clays. The effect of clay type and clay–masterbatch product on the clay exfoliation and nanocomposite properties was investigated. The effect of PP‐g‐MA concentration was also considered. Composite morphologies were characterized by X‐ray diffraction (XRD), field emission gun scanning electron microscopy (FEG‐SEM), and transmission electron microscopy (TEM). The degree of dispersion of organo‐modified clay increased with the PP‐g‐MA content. The thermal and mechanical properties were not affected by organo‐modified clay type, although the masterbatch products did have a significant influence on thermal and mechanical properties of nanocomposites. Intercalation/exfoliation was not achieved in the Nanofil SE 3000 composite. This masterbatch product has intercalants, whose initial decomposition temperature is lower than the processing temperature (T ～ 180°C), indicating that their stability decreased during the process. The Nanomax‐PP composite showed higher thermal and flexural properties than pure PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Reinforcing effect of organoclay in rubbery and glassy epoxy resins,part 1: Dispersion and properties

The reinforcing effect of organoclay in two epoxy matrices, one rubbery and one glassy, was studied. The rubbery and glassy epoxy matrices were chosen to have a very similar chemistry to minimize its impact on the comparison of properties. The epoxy resin was EPON? 828, and the two hardeners were amine‐terminated polyoxypropylene diols, having different average molecular weights (MW) of 2000 and 230 g/mol, namely Jeffamine® D‐2000 and Jeffamine® D‐230, respectively. The nanocomposites were prepared with the organoclay Cloisite® 30B from Southern Clay Products. The quality of dispersion and intercalation/exfoliation was analyzed by means of X‐ray diffraction (XRD), field emission gun scanning electron microscopy (FEGSEM), and transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the curing reactivity and the thermal stability of the epoxy resin systems, respectively. Tensile properties and hardness of epoxy resin and epoxy nanocomposites were measured according to ASTM standards D638‐02 and D2240‐00, respectively. Fracture surfaces were also analyzed by FEGSEM. These two epoxy systems as well as their nanocomposites display totally different physical and mechanical behavior. It is found that the quality of clay dispersion and intercalation/exfoliation, and the mechanical behavior of the glassy and rubbery epoxy nanocomposites are distinct. The results also indicate that the presence of the clay does not significantly affect the T_g of either the rubbery or the glassy epoxy; however, the fracture surface and mechanical properties were found to be influenced by the presence of nanoclay. Finally, several different reinforcing mechanisms are proposed and discussed for the rubbery and glassy epoxy nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

PP/黏土纳米复合材料的结构与性能

采用熔体插层法制备聚丙烯（PP）/有机黏土（OMMT）纳米复合材料。XRD和TEM的测试结果表明,采用熔体插层法制备的PP/OMMT复合材料是剥离型纳米复合材料。力学性能实验结果表明,相容剂的加入提高了PP与OMMT之间的相互作用,使其各项力学性能都得到了提高;PP/OMMT纳米复合材料的各项力学性能在有机黏土含量较小的情况下,就可以有较大幅度的提高;与纯PP相比,相容剂含量为10 phr、有机黏土用量为1 phr的聚丙烯基纳米复合材料具有最好的各项力学性能。     

A spectroscopic approach for structural characterization of polypropylene/clay nanocomposite

This study focuses on the degree of dispersion and structural development of organomodified MMT clay (OMMT) during processing of polypropylene clay nanocomposites using both conventional and nonconventional characterization techniques. PP‐g‐MA and Cloisite 15A were melt blended with three different grades of PP separately in a micro‐twin screw compounder at selected screw speed and temperature. The clay was modified with fluorescent dyes and the adsorbed dye content in the clay gallery was estimated by using UV‐spectrophotometric method. The effects of residence time and molecular weight of the PP matrix on the clay dispersion were studied. The extent of dispersion and exfoliation of the clay in polymer matrix determined from the torque versus time data obtained from microcompounder. It was further supported by XRD, SEM, TEM, and DSC analysis. Offline dielectric and fluorescence spectrophotometric studies were also carried out. Changes in dielectric constant and dielectric loss with both frequency and temperature yielded quantitative information about the extent of clay exfoliation and intercalation in the polymer matrix. It was observed that with an increase in MFI (decrease in molecular weight) and mixing time, the extent of clay dispersion and exfoliation were also improved due to easy diffusion of polymer chains inside clay gallery. POLYM. COMPOS., 31:2007–2016, 2010. © 2010 Society of Plastics Engineers     

Quantification of the layer dispersion degree in polymer layered silicate nanocomposites by transmission electron microscopy

As the performance of polymer layered silicate nanocomposites strongly depends on their interior layer dispersion, quantification of the layer dispersion degree is needed. In this work, a new methodology was developed to determine the dispersion parameter D_0.1, based on the measurement of the free-path spacing distance between the single clay sheets from the transmission electron microscopy (TEM) images. Several examples of exfoliated, intercalated, and immiscible composites were studied. It was found that the exfoliated composites had D_0.1 over 8%, while that of intercalated composites were between 4 and 8%. In the case of intercalation, a high frequency peak appeared at a short spacing distance in the histogram, which was a characteristic of the intercalation, distinct from the exfoliation. The main utility of this TEM methodology is for the quantification of exfoliated or intercalated samples with small number of layers with stacks. The dispersion parameter D_0.1 below 4% was suggested to classify as immiscible. A unique advantage of the TEM measurement is that the dispersion degree of different fillers can be counted individually.     

A novel strategy for nanoclay exfoliation in thermoset polyimide nanocomposite systems

A novel method of nanoclay exfoliation in the synthesis of nanocomposites of PMR type thermoset resins was investigated. The method involves nanoclay intercalation by lower molecular weight PMR monomer prior to dispersion in primary, higher molecular weight PMR resin and resin curing to obtain the final composites. The resultant mechanical and thermal properties were evaluated as functions of clay type, degree of clay exfoliation, and clay intercalation strategies. It was found that sonication of clay at the time of intercalation by lower molecular weight PMR resin helps to achieve higher degree of exfoliation. In addition, clays obtained from ion exchange with a 50:50 mixture of N-[4(4-aminobenzyl)phenyl]-5-norborene-2,3-dicarboximide (APND), and dodecylamine (C12) showed better exfoliation than Cloisite^® 30B clay. The resultant nanocomposites show higher thermal stability and higher tensile modulus.     

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     

Morphology and properties of polypropylene nanocomposites based on a silanized organoclay

A silanized organoclay (s-M₂(HT)₂) was prepared by reaction of trimethoxyphenyl silane with an organoclay with a M₂(HT)₂ surfactant structure. Nanocomposites were formed from polypropylene (PP) and a blend of PP and maleic anhydride-grafted polypropylene (PP-g-MA) and the M₂(HT)₂ and s-M₂(HT)₂ organoclays by melt processing to explore the extent of exfoliation and the mechanical properties. Wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) coupled with detailed particle analysis were used to determine the effect of the organoclay used and the PP-g-MA compatibilizer on exfoliation and mechanical, rheological, and thermal expansion properties. The PP/s-M₂(HT)₂ nanocomposites have higher particle densities than the PP/M₂(HT)₂ nanocomposites though the aspect ratio remains the same. Platelet dispersion is significantly improved by using PP-g-MA compatibilizer for both organoclays. The rheological properties and the relative modulus improve for the PP/s-M₂(HT)₂ nanocomposites but not to the same degree as either organoclay in a PP-g-MA compatibilized matrix. The thermal expansion properties, however, are not improved by using the s-M₂(HT)₂ organoclay. The s-M₂(HT)₂ organoclay is less prone to agglomeration during extrusion than the M₂(HT)₂ organoclay.     

Preparation and characterization of polyethylene (PE)/clay nanocomposites by <Emphasis Type="Italic">in situ</Emphasis> polymerization with vanadium-based intercalation catalyst

Summary  Complete exfoliation of clay during vanadium-based Zigler-Natta polymerization of ethylene has been successfully carried out by using clay and MgCl₂ hybrid supports. MgCl₂ offers catalyst loading sites, and the vanadium catalyst is avoided directly anchoring in the surface of the clay, so intercalation catalyst clay/MgCl₂/VOCl₃displays high activity for ethylene polymerization. Exfoliated PE/clay nanocomposites are confirmed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). Strong interaction between the dispersed clay particles and the polymer matrices provides good thermal and mechanical properties. Compared with pure PE, all these nanocomposites show enhancement of the melting temperature (T_m) and the thermal decomposition temperatures. Additionally, the incorporation of clay into the PE matrix significantly improves the mechanical properties of these nanocomposites. The increased tensile strength has been observed in the range of 3.4 to 7.9 MPa. The tensile moduli of the PE/clay nanocomposite are 23.4%-45.3% higher than that of the pure PE.     

Nanostructure and dynamic mechanical properties of silane-functionalized montmorillonite/epoxy nanocomposites

In this work sodium montmorillonite (Na-MMT) was functionalized with N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane and the corresponding silylated clay was used to modify epoxy matrix cured with triethylenetetramine. The grafting/intercalation of the aminosilane inside the clay galleries were followed by infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and ²⁹Si cross-polarization magic-angle-spinning nuclear magnetic-resonance (CP/MAS NMR) spectroscopy. Epoxy-based nanocomposites were prepared with different amounts of silylated clay or commercial organoclay, Cloisite 30B, whose intercalating agent consists of a methyl, tallow, bis-2-hydroxyethyl quaternary ammonium salt. The degree of intercalation/exfoliation was estimated by X-ray diffraction experiments and confirmed by small angle X-ray scattering. Nanocomposites prepared with silylated clay displayed no peak in both XRD and SAXS curves whereas those prepared with Cloisite 30B exhibited a clear interference peak corresponding to an interlayer spacing d₀₀₁ of 4.1 nm. The former also presented a better dispersion, with a high proportion of tactoids smaller than 2 nm, as estimated by SAXS. From the results of dynamic mechanical analysis it was observed that most of the nanocomposites display higher storage modulus mainly at temperatures above the glass transition temperature. The glass transition temperature is similar or higher than the neat epoxy network for nanocomposites containing 1 wt.% of silylated clay or higher.     

Morphology,biodegradability, mechanical,and thermal properties of nanocomposite films based on PLA and plasticized PLA

In this study, melt intercalation method is applied to prepare poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG)‐plasticized PLA nanocomposite films including 0, 3, and 5% organoclay (Cloisite 30B) using a laboratory scale compounder, which is connected to a microcast film device. To evaluate the nanomorphology and the dispersion state of the clays, X‐ray diffraction (XRD) and transmission electron microscopy (TEM) are conducted. Tensile tests are performed to characterize the mechanical behavior of the films. Biodegradation rate is determined by degradation tests in composting medium. Differential scanning calorimeter (DSC) is applied to observe the thermal behavior of the films. XRD and TEM show that the exfoliation predominantly occurrs in plasticized PLA nanocomposites, whereas unexfoliated agglomerates together with exfoliated clays are observed in the nonplasticized PLA. Tensile tests indicate that the addition of 3% clay to the neat‐PLA does not affect the strength; however, it enhances the modulus of the nanocomposites in comparison to neat‐PLA. Incorporation of 3% clay to the plasticized PLA improves the modulus with respect to PLA/PEG; on the other hand, the strain at break value is lowered ～ 40%. The increase in the rate of biodegradation in composting medium is found as in the order of PLA > PLA/PEG > 3% Clay/PLA/PEG > 5% Clay/PLA/PEG > 3% Clay/PLA. DSC analysis shows that the addition of 3% clay to the neat PLA results in an increase in T_g. The addition of 20% PEG as a plasticizer to the neat‐PLA decreases T_g about 30°C, however incorporation of clays increases T_g by 4°C for the plasticized PLA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and mechanical properties of PP/PP-g-MA/Org-MMT nanocomposites with different MA content

Summary Polypropylene-clay nanocomposites were prepared by melt intercalation in a twin screw extruder using two mixing methods: two-step mixing and one-step mixing. The effect of using two different kinds of PP-g-MA (polypropylene-grafted maleic anhydride), with graft efficiencies of 0.1 and 1.0 wt% of MA and with different molecular weight, on clay dispersion and mechanical properties of nanocomposites was investigated. Three different clays, natural montmorillonite (Cloisite Na+) and chemically modified clays Cloisite 20A and Cloisite 30B were used. The relative influence of each factor was observed from structural analysis by WAXD, TEM, and mechanical properties. X-ray diffractometry (XRD) was used to investigate the intercalation effect in the nanocomposites. The results indicted that the intercalation effect and mechanical properties, specially modulus, tensile strength and impact strength, were enhanced by increasing the content of MA, using maleated PP with higher graft efficiency, and using the two step mixing conditions. Better dispersion and exfoliation were obtained when using clay 20A than 30B and natural Na+ montmorillonite. The results showed that clay dispersion and interfacial adhesion are greatly affected by the kind of maleated PP. The increase in content of polar groups gives as a result better interfacial adhesion and subsequent mechanical performance.     

Batch and continuous processing of polymer layered organoclay nanocomposites

The generation of nanocomposites upon intercalation and exfoliation of clay tactoids using melt compounding is a difficult process. In this study various polymeric binders were melt compounded with organophilic clay particles using myriad methods, including sonication, batch mixing, and twin screw extrusion. The characterization of the compounded samples employing X‐ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that there is little intercalation and exfoliation when nonpolar poly(dimethyl siloxane) (PDMS) and poly(propylene) (PP) binders were used, resulting in no significant changes in the dynamic properties of the suspensions upon small‐amplitude oscillatory shearing. On the other hand, when polar polymeric binders, i.e., silanol terminated poly(dimethyl siloxane) and maleic anhydride modified PP were used for compounding with organoclays, TEM and XRD revealed intercalation with some partial exfoliation, resulting in increases in the dynamic properties, along with sensitivity to the thermomechanical history during processing. These results reinforce earlier findings, which suggest that the interfacial properties between the organoclays and the polymeric binders need to be tailored properly to enable the generation of nanocomposites of organoclays using melt compounding technologies. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1391–1398, 2007     

Mechanical,Thermal and Viscoelastic Behavior of Nylon 6/Clay Nanocomposites with Cotreated Montmorillonites

Nylon 6 nanocomposites were prepared using melt intercalation technique. Sodium montmorillonite (Na-MMT) was modified with octadecyl ammonium salt to evaluate the effect of clay modification on the performance of the nanocomposites. A comparative account with the nanocomposites prepared, using commercial clay cloisite 30B has been presented. X-ray diffraction (XRD) studies indicated an increase in the basal spacing of organically modified clays. Further, X-ray diffractograms of the nanocomposites displayed the absence of basal reflections suggesting the formation of an exfoliated structure. Transmission electron microscopy (TEM) investigations also confirmed exfoliation of clay galleries in the nanocomposites. Differential scanning calorimetry (DSC) measurements revealed both γ and α transitions in the matrix polymer as well as the nanocomposites. The crystallization temperature (T_c) exhibited a marginal increase in the C30B/Nylon 6 nanocomposites. Thermal stability of virgin Nylon 6 and the nanocomposites has been investigated using thermogravimetric analysis. Mechanical test revealed an increase in the tensile and flexural properties of Nylon 6 with the incorporation of nanoclays. Storage and loss modulus of virgin matrix increased with the incorporation of nanoclays. C30B/Nylon 6 nanocomposites exhibited optimum performance at 5% clay loading. Further, water absorption studies also confirmed comparatively lesser tendency of water uptake in these nanocomposites.     

Effect of clay content and clay/surfactant on the mechanical, thermal and barrier properties of polystyrene/organoclay nanocomposites

In the present paper, three ammonium salts namely, tetraethylammonium bromide (TEAB), tetrabutylammonium bromide (TBAB), and cetyltrimethylammonium bromide (CTAB) were employed to prepare organoclay by cation exchange process. Polystyrene (PS) /clay nanocomposites were prepared by melt blending using commercial nanoclay and organoclays prepared using above mentioned salts. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis indicated that the modified clays were intercalated and/or exfoliated into the polystyrene matrix to a higher extent than the commercial nanoclay. Further, amongst the modified organoclays, TBAB modified clay showed maximum intercalation of clay layers and also exfoliation to some extent into the polystyrene matrix. TEM micrograph exhibited that TBAB modified clay had the best nanoscale dispersion with clay platelet thickness of ∼6–7 nm only. The mechanical properties of the nanocomposites such as tensile, flexural and izod impact strength were measured and analyzed in relation to their morphology. We observed a significant improvement in the mechanical properties of polystyrene/clay nanocomposites prepared with modified clays as compared to commercial organoclay, which followed the order as; PS/TBAB system > PS/CTAB system > PS/TEAB system. Thermogravimetric analysis (TGA) demonstrated that T₁₀, T₅₀ and Tmax were more in case of polystyrene nanocomposites prepared using modified organoclays than nanoclay [nanolin DK4] and maximum being in the case of PS/CTAB system. The results of Differential Scanning Calorimetry (DSC) confirmed that the glass transition temperature of all the nanocomposites was higher as compared to neat polystyrene. The nanocomposites having 2% of TBAB modified clay showed better oxygen barrier performance as compared to polystyrene.     

Continuous process for melt intercalation of PP–clay nanocomposites with aid of power ultrasound

A continuous ultrasound‐assisted process using a single screw extruder with an ultrasonic attachment was developed to prepare PP/clay nanocomposites of varying clay concentrations. The feed rate that controlled the residence time of the polymer in the ultrasonic treatment zone was varied. Die pressure and power consumption were measured. Rheological properties, morphology, and mechanical properties of the untreated and ultrasonically treated nanocomposites were studied. An intercalation of polymer molecules into clay galleries and a partial exfoliation, which occur at short residence times (of the order of seconds), were observed as evident from measurements by X‐ray diffraction and transmission electron microscopy. The obtained results indicate a possibility of the rapid intercalation and partial exfoliation of PP/clay nanocomposites without the matrix being chemically modified. J. VINYL. ADDIT. TECHNOL. 12:78–82, 2006. © 2006 Society of Plastics Engineers.     

Investigation on polypropylene and polyamide-6 alloys/montmorillonite nanocomposites

Propropylene (PP) and polyamide-6 (PA6) alloys nanocomposites were prepared using melt intercalation technique by blending PP and PA6 while used organophilic montmorillonite (OMT). The melt intercalation of PP and PA6 alloys was carried out in the presence of a compatibilizer such as maleic anhydride-g-polypropylene (MAPP). Their structures were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and High Resolution Electronic Microscope (HREM). It was found different blend sequences have influence on the dispersibility of OMT and self-assembled structures of OMT appeared in PP and PA6 alloys. The crystallization behavior and crystal structure of PP and PA6 alloys/montmorillonite nanocomposites were investigated by X-ray diffraction. It showed that the blend sequences have influence on crystal structure and a higher cooling rate results in increasing of γ-crystalline phase. Flammability properties are characterized by Cone Calorimeter, which show an unusual phenomenon.     

Assessing organo‐clay dispersion in polymer nanocomposites

Organo‐clay polymer nanocomposites offer improved material properties at very low filler loadings making them of immediate interest for application in body panels, claddings, and instrument panels. This improvement in properties requires that the organo‐clay be well dispersed if not completely exfoliated. Conventionally, the dispersion and exfoliation of the organo‐clay is evaluated using transmission electron microscopy (TEM) and X‐ray diffraction (XRD). Although both TEM and XRD data were found to correlate with flexural modulus of thermoplastic olefin nanocomposite materials, only TEM proved successful in quantifying the dispersion of the organo‐clay in all nanocomposite materials (exfoliated, tactoid, or agglomerated tactoid). XRD was found to be capable of detecting exfoliation and intercalation but is limited because of clay dilution, preferred orientation, mixed‐layering, and other peak broadening factors. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1110–1117, 2004     

Preparation and characterization of PET/clay nanocomposites by melt compounding

Poly(ethylene terephthalate) (PET) nanocomposites were prepared via melt compounding using a twin‐screw extruder at 265°C. Three different types of organomodified clay were melt compounded with PET: a commercial ammonium‐modified silicate clay (Cloisite 30B) and specially prepared thermally stable phosphonium‐ and imidazolium‐modified montmorillonites. X‐ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), and thermogravimetric analysis were used to characterize and evaluate the quality of the nanocomposites. To obtain quantitative evaluation of the dispersion level in nanocomposites, statistical analysis of TEM micrographs was performed using a dispersion parameter, D_0.1, based on free‐path spacing measurements. The results showed that the ammonium surfactant yielded the best intercalation results in nanocomposites. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers