Polypropylene Clay Nanocomposites Research Articles

Evaluation of quality attributes of grated carrot packaged within polypropylene-clay nanocomposites

The current study aimed to investigate the protection role of nanocomposite polypropylene films containing clay nanoparticles (NPs) on grated carrot. The effects of clay NPs (1 and 3%) were studied during storage (1, 3, 6, 9 and 12 days) in a completely randomized design. All samples were stored at 4 ± 1 °C. The chemical characteristics, color (L*, b* and a* values), sugars content (glucose, fructose and sucrose), total phenolic content and sensory qualities of packaged carrot were measured. Moreover, microbial counts namely E. coli, molds, yeasts, psychotropic bacteria as well as total count were determined. According to the results, application of clay NPs significantly (P < 0.01) reduced the pH, color indices as well as acidity. Nanocomposites with 3% NPs showed the highest total phenolic content (P < 0.01). Clay NPs also could significantly (P < 0.01) prevent the reduction of glucose in all samples. According to the microbial results, yeasts, molds and psychotropic bacteria were reduced during the 12 day storage. Therefore, it could be concluded that a decontamination step followed by packaging in nanocomposites can remarkably preserve the physicochemical and microbial characteristics as well as sensory quality of grated carrots during storage.

Fabrication and Mechanical Characterization of Polypropylene Clay Nanocomposites

Investigating the influence of process parameters is vital to improve the mechanical properties of nanoparticle reinforced polymer nanocomposites. In this effort, nanocomposites of polypropylene/nanoclay are prepared by the extrusion method. In order to characterize the mechanical behavior of nanocomposites over different compounding ratios, samples are prepared with 5 and 10 wt%. Effect of re-extrusion and PP-g-MA compatibilizer on the tensile performance of nanocomposites is evaluated at different strain rates. XRD evaluation of compounds indicated that re-extrusion is an important factor in increasing the exfoliation degree.

Blown films with balanced in-plane properties from polypropylene-clay nanocomposites though silane coupling

Layered silicates present interaction sites at both faces and edges of the nanolayers and silane coupling agents that locate at both sites lead to polymer nanocomposites with superior melt strength and properties. This work’s objective was (a) to investigate the effectiveness of solvent-free, vapor phase, silane treatment of the nanolayers for formulating masterbatches and (b) to compare the mechanical properties of 1 mil thick blown films from polypropylene copolymer nanocomposites with such coupling, to films from the neat polypropylene. The nanocomposite blown film tensile modulus and tensile strength improved along both the draw direction and the transverse direction. In addition, their elongation to failure was close to 500% along both directions, in contrast to values of 500% along MD and 170% along TD for the neat PP copolymer. These trends may be understood in terms of the crystalline lamellar orientation distribution in the films. FESEM images revealed that cross-hatched lamellae were absent from the unfilled PP blown film and were pervasive in the nanocomposite blown film. The nanolayers were oriented in the film plane with the longer dimension largely along the MD. The lower extent of lamellar orientation around nanolayers may be attributed to the strong reduction in the polymer chain mobility attached to the nanolayers.

The effect of montmorillonite modification and the use of coupling agent on mechanical properties of polypropylene–clay nanocomposites

In this work, polypropylene (PP)–clay nanocomposites obtained by melt blending were investigated. Different commercial montmorillonites (MMTs), such as unmodified MMT, octadecyl ammonium-modified MMT, and dimethyl dialkyl ammonium-modified MMT, have been used. Maleic anhydride–polypropylene (MAPP) copolymer has been used as a coupling agent, and the effect of clay modification as well as MMT: MAPP ratio on final nanocomposites performance was studied. The transmission electron microscopy was used to evaluate the incorporation of clays into the PP matrix. The isothermal crystallization behavior of neat PP and different nanocomposites was studied by differential scanning calorimetry and polarized optical microscopy. Only nanocomposites based on organically modified MMT showed mechanical performance improvements. Nanocomposite reinforced with 5 wt% of organically modified MMT without MAPP showed modulus and strength values of 871 and 29.3 MPa, respectively, these values being higher, around 23% and 4.6%, respectively, than modulus and strength values of neat PP. The incorporation of MMT into the PP matrix produced an increment on the crystallinity rate with respect to neat PP. The half crystallization time of nanocomposites without MAPP was, at least, two times faster than for a neat PP system.

Synthesis and Characterization of Organo- Montmorillonite Clay and its Metal complexes for Polypropylene Clay Nano composites Applications

1-acetylpyridinium Chloride-salicyolhydrazone (H2ACSH) was prepared from Salicylaldehyde and 1-acetylpyridinium chloride hydrazide for using in modification of sodium montmorillonite clay in order to prepare organo - montmorillonite clay (OMC) and its Zinc (OMC-Zn) and Zirconium (OMC-Zr) complexes in two different weight percentage (3 and 7 wt %). Polypropylene /clay nanocomposites were prepared by melt intercalation technique using the prepared organo - montmorillonite clay and its metal complexes The obtained nanocomposites were characterized by infrared absorption spectroscopy (FTIR) and atomic force microscopy (AFM) to determine the morphology of obtained materials. The thermal behavior was evaluated from thermo gravimetric analysis (TGA). The combustion behavior of these intercalated ratios was studied using cone calorimeter measurement to assess the PP/clay nanocomposites behavior during combustion. The obtained results indicate decreased flammability properties of PP/clay nanocomposites due to better char enhancement. The new clay provides opportunities for melt blending of polymers with clay to obtain composites materials with important properties.

Ziegler-Natta Catalyst Based on MgCl₂/Clay/ID/TiCl₄ for the Synthesis of Spherical Particles of Polypropylene Nanocomposites.

In the present work, we have designed MgCl2/clay/internal donor (ID)/TiCl4 based bisupported Ziegler-Natta catalysts containing varying amounts of organoclay (montmorillonite) in order to synthesize spherical particles of polypropylene/clay nanocomposites (PCN). The organoclay was introduced into the catalyst support formulation and PCN was obtained using the in situ polymerization technique. Decreasing the reaction time, it was possible to obtain nanocomposites with high concentrations of clay (masterbatches). Micrographs of SEM confirmed the spherical morphology of the catalysts. In addition, XRD patterns show that the active sites for polymerization were inserted in the clay galleries. The catalytic performance was evaluated in slurry propylene polymerization using triethylaluminium as cocatalyst and silane as external electron donor at 70 °C, 4 bar, and different reaction times. The PCNs obtained containing different clay amounts were characterized by X-ray diffraction, thermal analyses, transmission electronic microscopy, and extractables in heptane. The results revealed that the synthesized PP/clay particles were also spherical showing that the morphological control is possible even using catalysts containing high amounts of clay. The PCN presented high degradation temperature (459 °C). The XRD peak related to the clay interlamellar distance has shifted to lower angles, and TEM images confirmed the formation of exfoliated/intercalated clay on the PP matrix and absence of microparticles of clay.

Study of temperature effects on the electrical behavior of polypropylene-clay nanocomposites submitted to electron beam irradiation in a SEM

Charge transport and electron emission properties in polypropylene and its nanocomposites filled with nanoclay particles submitted to an electron irradiation, in a Scanning Electron Microscope (SEM), are investigated using induced displacement and leakage currents. The measurements have been performed at various temperatures ranging from 20°C to 75°C at a primary beam energy of 20keV and a primary beam current of 1nA with the aim to highlight the effect of temperature and nanoclay content on these properties. The results show, at a given temperature, that the incorporation of clay in polypropylene (PP) matrix paradoxically leads to a concomitant increase in the electrical conductivity and the charge accumulated. In contrast, if the clay content is fixed, there is an increase in conductivity and a reduction of the charge accumulated when the temperature increases. The mobility of charge carriers and the corresponding activation energy are deduced from the measured leakage current during discharging step. The mobility was found to be an order of magnitude higher for the nanocomposites. The study of the influence of the temperature and nanoclay concentration on electron emission yield is also addressed.

Modeling of the effect of particles size, particles distribution and particles number on mechanical properties of polymer-clay nano-composites: Numerical homogenization versus experimental results

The main goal of this paper is to predict the elastic modulus of partially intercalated and exfoliated polymer-clay nano-composites using numerical homogenization techniques based on the finite element method. The representative volume element was employed here to capture nano-composites microstructure, where both intercalated exfoliated and clay platelets coexisted together. The effective macroscopic properties of the studied microstructure are obtained with two boundary conditions: periodic boundary conditions and kinematic uniform boundary conditions. The effect of particle volume fractions, aspect ratio, number and distribution of particles and the type of boundary conditions are numerically studied for different configurations. This paper investigate also the performance of several classical analytical models as Mori and Tanaka model, Halpin and Tsai model, generalized self consistent model through their ability to estimate the mechanical properties of nano-composites. A comparison between simulation results of polypropylene clay nano-composites, analytical methods and experimental data has confirmed the validity of the set results.

Near Infrared Investigation of Polypropylene-Clay Nanocomposites for Further Quality Control Purposes-Opportunities and Limitations.

Polymer nanocomposites are usually characterized using various methods, such as small angle X-ray diffraction (XRD) or transmission electron microscopy, to gain insights into the morphology of the material. The disadvantages of these common characterization methods are that they are expensive and time consuming in terms of sample preparation and testing. In this work, near infrared spectroscopy (NIR) spectroscopy is used to characterize nanocomposites produced using a unique twin-screw mini-mixer, which is able to replicate, at ~25 g scale, the same mixing quality as in larger scale twin screw extruders. We correlated the results of X-ray diffraction, transmission electron microscopy, G′ and G″ from rotational rheology, Young’s modulus, and tensile strength with those of NIR spectroscopy. Our work has demonstrated that NIR-technology is suitable for quantitative characterization of such properties. Furthermore, the results are very promising regarding the fact that the NIR probe can be installed in a nanocomposite-processing twin screw extruder to measure inline and in real time, and could be used to help optimize the compounding process for increased quality, consistency, and enhanced product properties.

An Investigation of Mechanical and Thermal Properties of Polypropylene Clay Nanocomposites Containing Different Nanoclays

AbstractIn the present investigation, polypropylene clay nanocomposites (PP‐CNs) are prepared by melt compounding using the Polymer NanoComposite Injection Molding Compounder (PNC‐IMC) with different nanoclays and at varying compatibilizer/nanoclay ratios. A specially devised hyperbolical nozzle is used to induce elongational flow for better mechanical properties. Statistical analysis of the mechanical properties reveal that PP‐CNs based on mica‐phlogopite is superior to other PP‐CNs. Beside intercalated and exfoliated structures the SAXS results confirms that the PP‐CNs show well aligned and also randomly disordered structures. TGA shows among the investigated nanoclays organic modified montmorillonite (OMMT) shows substantial improvement in thermal stability of PP‐CNs.

Effect of MWNTs on Mechanical Properties of PP/MMT Nanocomposites

This article addresses the effect of Multiwalled carbon nanotubes (MWNTs) on the mechanical properties of polypropylene (PP)/ Montmorillonite (MMT) nanocomposites. PP/MWNT/MMT hybrid nanocomposites have been prepared by melt mixing using maleic anhydride grafted polypropylene (MAH-g-PP) as compatibilizing agents. Melt mixing was achieved using twin screw extruder. The MAH-g-PP used as compatibilizer helped the dispersion of the MWNTs in PP/MMT matrix. The effect of MWCNTs on the PP/MMT nanocomposites was investigated in terms of mechanical properties and morphological using Transmission electron microscope (TEM), X-ray diffraction (XRD), tensile test, flexural test and notched Izod impact test. These were compared with the conventional polypropylene-clay nanocomposite. The resulting composite shows about 33% increase in tensile modulus and 20% in the impact strength when compared with binary combination of PP/MMT nanocomposite.

Infrared heating assisted thermoforming of polypropylene clay nanocomposites

The objective of this work is to study the influence of nanoclay addition in PP sheet during infrared (IR) heating assisted thermoforming process. The effect of nanoclay on viscoelastic, friction and dimensional characteristics during sheet forming was examined. The result indicated that the nanoclay addition improves the sagging (sagging depth and sagging disintegration) and plugging (plug depth and friction) properties during sheet forming. The plugging properties of nanoclay filled PP sheet resulted in the improved physical characteristics (minimal change in thickness (Δt) and % dimensional elongation) when compared with unfilled PP sheet. The nanoclay filled formed PP sheet resulted in improved tensile and dynamic mechanical properties when compared with unfilled formed PP sheet.

Micromechanics-based constitutive modeling of plastic yielding and damage mechanisms in polymer–clay nanocomposites: Application to polyamide-6 and polypropylene-based nanocomposites

Abstract The present work focuses on the continuum-based micromechanical modeling of the elastic–plastic stress–strain response including damage mechanisms of polymer–clay nanocomposites. The micromechanical elastic–plastic-damage model includes both the actual microstructure of the said composites using a multi-scale approach and the microstructural evolution related to damage accumulation under applied macroscopic deformation. The interfacial debonding between clay nanoparticles and polymer matrix, and the polymer matrix voiding are the two prevalent damage events considered. The tensile stress–strain response and micromechanical deformation processes of polyamide-6 and polypropylene-based systems reinforced with modified montmorillonite clay at various concentrations are experimentally investigated by a video-controlled technique. The usual shear yielding deformation mode of neat polyamide-6 is altered by the presence of clay platelets which induce a dilatational process due to interfacial debonding. In addition to matrix shear yielding, a dual-dilatational deformation mechanism by crazing and interfacial debonding is revealed in polypropylene–clay nanocomposites. Using the intrinsic deformation micromechanisms and elastic–plastic properties of the polymer matrix, and the nanocomposite structural characteristics, the micromechanical model is found to successfully describe the experimental results of the two nanocomposite materials in terms of tensile stress–strain response and inelastic volumetric strain.

Influence of processing and clay type on nanostructure and stability of polypropylene–clay nanocomposites

Melt processing is a critical step in the manufacture of polymer articles and is even more critical when dealing with inhomogeneous polymer-clay nanocomposites systems. The chemical composition, and in particular the clay type and its organic modification, also plays a major contribution in determining the final properties and in particular the thermal and long-term oxidative stability of the resulting polymer nanocomposites. Proper selection and tuning of the process variable should, in principle, lead to improved characteristics of the fabricated product. With multiphase systems containing inorganic nanoclays, however, this is not straightforward and it is often the case that the process conditions are chosen initially to improve one or more desired properties at the expense of others. This study assesses the influence of organo-modified clays and the processing parameters (extrusion temperature and screw speed) on the rheological and morphological characteristics of polymer nanocomposites as well as on their melt and thermo-oxidative stability. Nanocomposites (PPNCs) based on PP, maleated PP and organically modified clays were prepared in different co-rotating twin-screw extruders ranging from laboratory scale to semi-industrial scale. Results show that the amount of surfactant present in similar organo-modified clays affects differently the thermo-oxidative stability of the extruded PPNCs and that changes in processing conditions affect the clay morphology too. By choosing an appropriate set of tuned process variables for the extrusion process it would be feasible to selectively fabricate polymer-clay nanocomposites, with the desired mechanical and thermo-oxidative characteristics.

Thermal stability of polypropylene-clay nanocomposites subjected to laser pulse heating

Abstract Polypropylene based nanocomposites filled with montmorillonite nanoclay prepared by twin screw extrusion have been studied for thermal stability at high heating rates. In contrast to traditional thermal stability and flammability studies of polymer nanocomposites using heating rates on the order of tens of degrees per minute, this study achieves heating rates that are six orders of magnitude higher. This was accomplished using laser pulse heating. The results show that the nanoclay increases thermal stability of the polymer, as measured by a decrease in the mass loss for a laser pulse at a given energy and intensity. Electron microscopy and various spectroscopic techniques show that a silicate-rich char layer may provide the mechanism for protection of the polymer and decreased degradation rates. The results of the study are compared to the typical results found in traditional thermal stability testing.

Influence of thermal conditions on the tensile properties of basalt fiber reinforced polypropylene–clay nanocomposites

In this paper, a comparative study on the tensile properties of clay reinforced polypropylene (PP) nanocomposites (PPCN) and chopped basalt fiber reinforced PP–clay nanocomposites (PPCN-B) is presented. PP matrix are filled with 1, 3 and 5wt.% of nanoclays. The ultimate tensile strength, yield strength, Young’s modulus and toughness are measured at various temperature conditions. The thermal conditions are included the room temperature (RT), low temperature (LT) and high temperature (HT). The basal spacing of clay in the composites is measured by X-ray diffraction (XRD). Nanoscale morphology of the samples is observed by transmission electron microscopy (TEM). Addition of nanoclay improves the yield strength and Young’s modulus of PPCN and PPCN-B; however, it reduces the ultimate tensile strength. Furthermore, the addition of chopped basalt fibers to PPCN improves the Young’s modulus of the composites. The Young’s modulus and the yield strength of both PPCN and PPCN-B are significantly high at LT (−196°C), descend at RT (25°C) and then low at HT (120°C).

Elucidation of Volatile Changes in Soybean Oil Stored in Polypropylene-Clay Nanocomposite

The permeation of oxygen and the effects of nanoclay on volatile retention through a PP (polypropylene)-clay nanocomposite were investigated. A nanocomposite film of 1.465 mm thickness was prepared by heat-pressing PP granules containing 500 mg/kg nanoclay at 280oC. Inductively coupled plasma-optical emission spectrometry showed that the nanoclay was mainly composed of Ca (40.7%). Also, transmission electron microscopy revealed that the nanoparticles were well dispersed in the nanocomposite container whereas fourier transform infrared spectrometry demonstrated that the PP intermolecular bonds were not significantly affected by the addition of nanoclay. Diaphragm diffusion analysis explained that the addition of nanoclay reduced the oxygen permeability of the PP container by 20% at 20 and 40oC. Based on the results of SMPE/GC-MS, the relative amounts of volatiles from lipid oxidation, including pentanal, hexanal, and (E)-2-heptenal, were higher in neat PP than those in PP/clay nanocomposite containers. After 5 weeks, the POV, CDA values, and p-AV of the sample in the nanocomposite container were lower than those of the neat PP container at 20oC. The POV, CDA values, and p-AV of the samples continuously increased over 3 weeks for the neat PP container and 5 weeks for the nanocomposite container at 40oC.

Degradation Behavior of Polypropylene–Organically Modified Clay Nanocomposites

The degradation mechanism of polypropylene (PP)–clay nanocomposites is investigated in the present study. The PP–clay nanocomposites are prepared through a solution process with 4 and 8 wt % incorporation of nanoclay in a polymer matrix. Nanoclay with two types of organic modifications (25–30 wt % methyl dihydroxyethyl hydrogenated tallow ammonium (TA) and 25–30 wt % octadecylamine (OA)) is used with isotactic PP, atactic PP, and ethylene propylene copolymer with ∼20 wt % rubber. Characterization of nanocomposites is done through X-ray diffraction (XRD) analysis while melting and crystallization behavior is studied through differential scanning calorimetry (DSC). XRD and DSC analysis shows formation of intercalated type nanocomposites with improved barrier properties. Degradation behavior of nanocomposites is studied through thermogravimetric analysis (TGA). Weight loss curves are further analyzed through the Friedman technique to find the rate of degradation. Nanoclay incorporation increases the lifetime...

Mechanics of nanoscale surface deformation in polypropylene-clay nanocomposite

The study described here is in sequel to our studies on the mechanics of microscale deformation in thermoplastic materials where a perspective of deformation processes occurring over different strain–strain rate regimes was obtained. The specific aim here is to enhance our fundamental understanding from microscale to nanoscale deformation in polymeric material systems containing dispersion of nanoparticles, considering the growing use of polymeric materials as functional materials. A Berkovich nanoindenter was used to induce surface damage using a load of 0.5–1 mN and scratch velocity of 1 μm/s. The secondary objective is to investigate the commonality in surface deformation behavior between nano- and microscale deformation to reinforce the underlying fundamental principles governing surface deformation. Combining electron microscopy with nanoscale surface deformation experiments enabled us to extend the understanding of microscale deformation to nanoscale deformation. In the intercalated polypropylene-nanoclay system, the susceptibility to surface deformation was significantly reduced because of the shift of von Mises stress from the surface to the sub-surface region, with consequent reduction in the maximum tensile stress induced by the nanoindenter. This conclusion was consistent with electron microscopy observations and theoretical analysis.

Development and applications of polyolefin– and rubber–clay nanocomposites

A nylon 6-clay hybrid (nanocomposite, NCH) was developed by Toyota CRDL group. In the NCH, the silicate layers of clay mineral are dispersed on a nanometer level and are strongly interacted with the matrix, and then significant improvements in the mechanical properties of the material or the discovery of unexpected new properties were realized. Polypropylene (PP) is the most widely used polymer, and then an appearance of a PP–clay nanocomposite has been desired for a long time. As a PP does not include any polar groups in its backbone, it was thought that the homogeneous dispersion of the silicate layers would not be realized. But we have developed successfully PP–clay nanocomposite using organoclay and modified PP. That is, organophilic clay, PP oligomer carrying polar groups and PP were melt-blended. This is a direct polymer intercalation process for preparing polymer nanocomposites by melt compounding, a useful process from an industrial standpoint. We have also developed successfully other polyolefin polymers (polyethylene), polyolefin rubbers (ethylene–propylene elastomer, ethylene–propylene diene monomer) and nanocomposites by this direct polymer intercalation process or by techniques based on direct polymer intercalation process. These prepared polyolefin nanocomposites exhibit superior mechanical, thermal and gas barrier properties. Polyolefins (polypropylene (PP), polyethylene and so on) and polyolefin rubbers (ethylene propylene diene monomer, ethylene propylene elastomer and so on) are the most widely used polymers. Therefore, a development of a polyolefin and polyolefin rubber–clay nanocomposite has been desired for a long time. As these polyolefin polymers do not include any polar groups in its backbone, it was thought that the homogeneous dispersion of the silicate layers would not be realized. But we have successfully developed these polymer–clay nanocomposites by using various methods.