Polypropylene Clay Research Articles

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.

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.

Polypropylene–clay micro/nanocomposites as fused deposition modeling filament: effect of polypropylene-g-maleic anhydride and organo-nanoclay as chemical and physical compatibilizers

Amongst various polymers used as fused deposition modeling filaments, polypropylene is one which undergoes rigorous shrinkage during printing. This is a drawback for 3D-printer process and related applications, and to overcome this hurdle, mostly, mineral fillers are utilized; however, this additive reduces mechanical properties. To enhance mechanical and shrinkage properties, unmodified clay sheets extracted from bentonite mineral were used as a reinforcing agent, polypropylene grafted maleic anhydride (PP-g-MA) and nanoclay were used as compatibilizers. The compounding was carried out by a twin-screw extruder rather than a single-screw extruder to procure filaments. Afterwards, with fused deposition modeling, dumb-bells and disks were produced for testing. Scanning electron microscopy was employed to examine the morphological feature and dispersion of nanoclay and montmorillonite in the composites. X-ray diffraction was also used to study the dispersion of the nanoclays. The composite disks and dumb-bells were fabricated with a 3D printer to evaluate their rheological properties. Our results showed that the complex viscosity decreased drastically due to aligning the polymer chains along the clay sheets. Mechanical property measurements revealed that the tensile modulus was improved by 60% compared to that of the PP.

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.

Nanoscale reinforcement of polypropylene composites with carbon nanotubes and clay: Dispersion state, electromagnetic and nanomechanical properties

In the present study, the bifiller system incorporating various amount of multiwalled carbon nanotubes (MWCNTs) and 3 wt% clay in polypropylene is investigated to obtain composites with multifunctional performance. The dispersion state of two nanofillers in the polypropylene matrix was characterized by applying TEM and Raman spectroscopy. Both composites demonstrate similar rheological behavior with a rheological percolation threshold of ϕp1 = 1.5 wt% for the monofiller (MWCNTs) and ϕp2 = 2 wt% for the bifiller systems (MWCNTs and 3% clay). The effect of two nanofillers on electromagnetic and nanomechanical properties was evaluated. Above rheological percolation both type composites show considerable electromagnetic shielding efficiency at small layer thickness due mostly to the addition of MWCNTs. The nanomechanical properties improvement is strongly dependent on the structure formed by MWCNTs in the polymer. The hardness and Young's modulus, measured by nanoindentation, is higher for the bifiller systems in comparison with the monofiller one above the rheological percolation threshold. This was attributed to the continuous network structure formed by interacted MWCNTs and infiltrated fine clay stacks. POLYM. ENG. SCI., 56:269–277, 2016. © 2015 Society of Plastics Engineers

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.

Compatibilizing action and localization of clay in a polypropylene/natural rubber (PP/NR) blend

The compatibilizing action of clay in polypropylene (PP)/natural rubber (NR) blends and its effect on mechanical properties have been investigated.

Release of nanoclay and surfactant from polymer-clay nanocomposites into a food simulant.

Release assessment of organo-modified montmorillonite (O-MMT) nanoclay and the organo-modifiers (surfactants) was performed on two types of polymer–clay nanocomposites: polypropylene (PP) and polyamide 6 (PA6) with O-MMT. In accordance with ASTM D4754-11, nanocomposite films were exposed to ethanol as a fatty-food simulant at 70 °C. The release of O-MMT, with Si and Al used as the nanoclay markers, was evaluated by graphite furnace atomic absorption spectrometry. The nanoclay particles released in ethanol were visualized by transmission electron microscopy (TEM). More nanoclay particles were released from PP–clay films (0.15 mg L(–1)) than from PA6–clay films (0.10 mg L(–1)), possibly due to the lack of interaction between the nanoclay and PP as indicated by the structure and morphology in the TEM images. The surfactant release was quantified by a liquid chromatography tandem mass spectrometry (LC-MS/MS) method. A substantial amount of surfactant was released into ethanol (3.5 mg L(–1) from PP–clay films and 16.2 mg L(–1) from PA6–clay films), indicating changes in the nanoclay structure within the nanocomposite while it was exposed to ethanol. This research has provided information for the determination of exposure doses of nanoclay and surfactant in biosystems and the environment, which enabled the risk assessment.

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.

Study of the Rheological Properties of PP/Clay Systems under Steady and Oscillatory Shear Flows

In this work, polypropylene (PP) and organophilic clay composites without and with PPgMA compatibilizer were obtained. The organoclay was incorporated into the PP matrix at concentrations of 0.5, 1.0, 3.0, 5.0 and 10 phr in order to obtain composites without compatibilizer. In the systems with compatibilizer, concentrations of 0.5 and 1phr of the organoclay were used. The systems were characterized by rheological measurements under steady and oscillatory shear flows. In the rheological characterization, it was observed that the viscosity and storage modulus at low frequencies increased with the increase in the clay content and with the compatibilizer. These results are relevant in the evaluation of the influence of the compatibilizer in the processability and in the degree of clay dispersion.

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.

Investigations on clay dispersion in polypropylene/clay nanocomposites using rheological and microscopic analysis

ABSTRACTMorphology assessment plays an important role as the ultimate properties of the processed nanocomposites mainly depend upon the morphology. This study focuses on the evaluation of polypropylene/clay nanocomposite structure using rheological and transmission electron microscopic investigation. Melt processing of nanocomposite was carried out on a co‐rotating twin screw extruder. Maleic anhydride grafted polypropylene (PP‐g‐MA) was used as a compatibilizer to facilitate better mixing of clay in polypropylene. The effect of compatibilizer to clay ratio on dispersion was analyzed through rheological data. An increase in complex viscosity and storage modulus with increase in compatibilizer content is observed at lower frequency region. Shifting of crossover frequencies to a lower value also indicate better exfoliation. Improved exfoliated morphology was also corroborated by Cole–Cole and inverse loss tangent plots. Transmission electron microscopy (TEM) micrograph based unique statistical image analysis was carried out using ImageJ software. A compatibilizer to clay content of 2 : 1 was found to be the optimum composition which was further supported by dielectric and mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4464–4473, 2013

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).

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...

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.

Extrusion of linear polypropylene–clay nanocomposite foams

AbstractThis work presents new results on using organoclay with an appropriate polymeric compatibilizer as rheology‐modifying additives for extrusion foaming of a linear polypropylene (PP), which by itself does not display strain hardening in extensional flow of the melt. The uniaxial melt‐extensional viscosity behavior of several nanocomposites prepared with varying ratio of bound maleic anhydride to clay as well as varying compatibilizer molecular weight was investigated. A chemical‐blowing agent was used at a fixed concentration for foaming these nanocomposites in a single‐screw extruder. Among nanocomposites with similar levels of clay dispersion or intercalation, the ones that displayed significant strain hardening in the melt state along with slower crystallization led to extruded PP nanocomposite foams with smaller cell sizes and greater cell density by reducing cell coalescence. This was achieved with as little as 3 wt% organoclay and a high‐molecular weight PP‐g‐MA compatibilizer in linear PP. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Co-intercalation in PP Clay Nanocomposites: Effect of Short Chain Additives on Rheological Properties

Abstract Layered structures in inorganic minerals are not easily intercalated when combined with conventional non-polar polymers such as polypropylene (PP). A new co-intercalation method is reported whereby the combined influence of low molecular weight polar additives and polyolefin-based compatibilizers on PP-clay nanocomposites (PPCN) has been investigated. Our research has shown that the interlayer spacing of montmorillonite clay increases dramatically, and increased particle dispersion is achieved, when short chain, organic additives (typically amide-type, AM) are included. In this work, the migration of these additives into the clay galleries has been confirmed by surface energy data (from contact angle experiments) and by various capillary flow measurement techniques. Shear flow data have been used to interpret the mechanism of intercalation, following compound preparation using melt-state mixing processes. At relatively low concentrations, the erucamide molecules assist the intercalation process in nanocomposites; however if an excess of AM is apparent within the bulk polymer melt, unusual flow behavior is observed which can be attributed to wall slip. Modified melt elasticity is also obtained with the PPCN's leading to reduced die swell characteristics in extrusion processes. Significant differences in melt flow behavior can therefore be attributed to the presence of AM; a mechanism for co-intercalation has been proposed in terms of hydrogen bonding between the additives and the silicate layers.