Localization Of Nanoclay Research Articles

Correlation of morphology, rheology, thermal, and mechanical properties in PP/EOC blends in presence of nanoclay and compatibilizer

ABSTRACT To expand the range of applications and overcome mechanical limitations of Polypropylene (PP), a commonly used industrial polymer, toughness modification is required. In this study, PP was toughened with ethylene octene copolymer (EOC) and nanoclay platelets and the blends and nanocomposites of PP/EOC were prepared by means of a melt mixing process, and the effect of different grades of EOC, the addition of nanoclay platelets, and the effect of compatibilizer on properties of the final system were investigated. Scanning and transition electron microscopy, X-ray diffraction, rheology, differential scanning calorimetry, and dynamic-mechanical analysis were conducted to correlate the structure to the resulting properties. The results indicate that different grades of EOC with different molecular weights and viscosity can have a tremendous impact on droplet size and final properties of the blend sample. From a morphological point of view, the addition of EOC grade with higher viscosity (ƞi) in PP/EOC blends results in droplet matrix structure with larger EOC droplets. To decrease the droplet size, and hence improvement in final properties, nanoclay and compatibilizer were introduced to the blend. According to the results, selective localization of nanoclay and proper dispersion degree of nanoclay in the PP/EOC blend with higher viscosity grade of EOC containing nanoclay up to 3 wt.% lead to amelioration of the final properties of the system including complex viscosity, storage modulus, damping, and crystallinity. Moreover, the addition of the compatibilizer to the nanocomposite samples with 5 wt.% nanoclay can compensate for the deteriorated properties which occurred as a result of nanoclay aggregation in this system. This indicates that the addition of the nanoclay and compatibilizer plays an important role in toughening, morphology, and determining the final properties of the system as well.

Toward understanding the crystallization behavior of polypropylene‐based nanocomposites: Effect of ethylene–octene copolymer and nanoclay localization

AbstractThe crystallization properties of polypropylene (PP), a widely used polymer in industry, can be modified to overcome its mechanical limitations. In the current work, we investigated the effect of ethylene octene copolymer (EOC), blend morphology, nanoclay loading, nano‐localization, and component ratios on PP/EOC crystallization behavior in various aspects, including crystallization rate, degree of crystallinity, nucleation state, and crystalline phases. The results revealed that adding EOC with varying ratios can decrease PP crystallinity both in degree and rate due to the partial miscibility of components through grafting. Furthermore, it was found that the effect of the nanoclay on the crystallization behavior of PP is dependent on the nanoclay loading and its localization in the blend. The nanoclay, therefore, served as a nucleation agent at low nanoparticle contents, accelerating the crystallization rate regardless of the blend's microstructure. However, the crystallization rate of the blend samples at high nanoclay contents (above the rheological percolation threshold) was strongly influenced by the type of morphology. Accordingly, high nanoclay concentrations in blends with matrix‐dispersed morphologies reduced crystallization rates (increasing half‐time from 164 to 216 and 186 s), primarily because PP chains slowed down due to their interactions with nanoparticles and nanoclay hindrance. In contrast, in a blend with a co‐continues‐type morphology, the crystallization rates increased (decreasing half‐time from 624 to 270 and 236 s) due to nano‐localization at the interface and morphology transformation to the matrix‐dispersed one. The blends and nanocomposites based on PP/EOC were also investigated to determine the relationship between the crystallization behavior and mechanical properties.

Dual role of nanoclay in the improvement of the in-situ nanofibrillar morphology in polypropylene/polybutylene terephthalate nanocomposites

The present study has addressed the effects of nanoclay on the properties of polypropylene (PP)/polybutylene terephthalate (PBT) blend fibers such as their dyeability and, rheological and resiliency behaviors which are produced by melt spinning. The results of the differential scanning calorimetry (DSC) analysis indicated that the presence of both nanoclay and PBT significantly influenced the crystallinity of PP which also confirmed their nucleating effects on the nanocomposite fibers. Compared to neat PP fibers, the incorporation of 0.5–1wt.% of nanoclay and 10 wt.% of PBT nanocomposite fibers caused approximately 23% and 52% enhancements in the resiliency and dye uptake respectively without using toxic carriers. The rheological analysis was carried out for investigating the viscoelastic behavior, and microstructural and dispersion of nanoclay in the nanocomposite fibers. The rheological behavior in the small amplitude oscillatory shear (SAOS) test demonstrated the percolation threshold network of the structure of PBT fibrils in the PP matrix. When the PBT domains are fibrillated, the storage modulus (G′) and complex viscosity increase compared to neat PP. Also, the nonterminal behavior at low frequencies indicates the uniform dispersion of nanoclay in fiber nanocomposites. These all cause the improvement of the melt strength of the PP matrix. Transmission electron microscopy (TEM) was used to study the dispersion and localization of nanoclay. Nanoclay has also played a compatibilizing role in the immisible PP/PBT blend and was localized mainly in the PBT disperse and interface, and therefore prevented coalescence. The role of the compatibility of nanoparticles is to decrease the mean diameter of the nano-fibrils to 75 nm, for the hot-drawn nanocomposite fibers, as measured by scanning electron microscopy (SEM). All of the above lead to increasing the melt strength and elasticity of the nanocomposites in the fiber spinning process.

Effect of nanoclay on relaxation and breakup of polyamide 6 threads in polystyrene matrix

AbstractIn this work, we investigate the compatibilizing mechanism of nanoclay in binary polymer blends by measuring the interfacial tension of polystyrene/polyamide 6, PS/PA6, as a typical system, in the presence of nanoclay. The interfacial tension of PA6 nanocomposites and PS are determined with the breaking thread method by employing the Tomotika theory. The interfacial tension is reduced when organoclay is incorporated in the PA6 phase. To investigate the effect of the localization of nanoclay, nanoclay is intentionally located at the interface of PA6 and PS. Microscopic observations show that PA6 fiber remain unchanged and does not go through break‐up process; therefore, one can deduce that the apparent interfacial tension of the system reduces significantly when nanoclay particles saturate the interface.

Gas Barrier, Rheological and Mechanical Properties of Immiscible Natural Rubber/Acrylonitrile Butadiene Rubber/Organoclay (NR/NBR/Organoclay) Blend Nanocomposites.

In this paper, gas permeability studies were performed on materials based on natural rubber/acrylonitrile butadiene rubber blends and nanoclay incorporated blend systems. The properties of natural rubber (NR)/nitrile rubber (NBR)/nanoclay nanocomposites, with a particular focus on gas permeability, are presented. The measurements of the barrier properties were assessed using two different gases—O2 and CO2—by taking in account the blend composition, the filler loading and the nature of the gas molecules. The obtained data showed that the permeability of gas transport was strongly affected by: (i) the blend composition—it was observed that the increase in acrylonitrile butadiene rubber component considerably decreased the permeability; (ii) the nature of the gas—the permeation of CO2 was higher than O2; (iii) the nanoclay loading—it was found that the permeability decreased with the incorporation of nanoclay. The localization of nanoclay in the blend system also played a major role in determining the gas permeability. The permeability of the systems was correlated with blend morphology and dispersion of the nanoclay platelets in the polymer blend.

Nanoparticle Interactions and Molecular Relaxation in PLA/PBAT/Nanoclay Blends

AbstractOrgano-modified clay nanoparticles were mixed at 1 and 5 wt% concentrations with a molten blend of 75 wt% of polylactide (PLA) and 25 wt% poly[(butylene adipate)-co-terephthalate] (PBAT). Three mixing strategies were used to control the localization of nanoclay. Small amplitude oscillatory shear (SAOS) and stress growth tests were conducted to clarify the nanoclay interactions with the blend components and its effect on the molecular relaxation behavior. SAOS and weighted relaxation spectra properties were determined before and after pre-shearing at a rate of 0.01 s−1. Molecular relaxation and its characteristics were influenced by PLA degradation, PBAT droplet coalescence, and nanoclay localization.

Structure–property relationship in PP/LDPE blend composites: The role of nanoclay localization

ABSTRACTThis article reports, for the first time, on how the kinetics and thermodynamics of the melt‐processing control the nano/micro‐structure development and properties of nanoclay‐filled polypropylene (PP)/low‐density polyethylene (LDPE) blend ternary composites. Morphological characterization suggests that the nano/micro‐structure of the PP/LDPE (80/20) blend can be controlled by incorporating nanoclay alone or by adding a mixture of organoclay and maleated compatibilizers. Simultaneous mixing of PP, LDPE, maleated compatibilizers, and organoclay results in homogeneous distribution of intercalated silicate layers in all the phases of the blend, a feature which profoundly affects the thermal stability and tensile and rheological properties of the blend composites. For example, the elongation‐at‐break for PP increases from 28.1 to 155.6% for composite containing both organoclay and maleated compatibilizers, whereas the thermal stability for PP increases from 269.8 to 303.3 °C for the same composite. However, the impact strength of the PP/LDPE blend decreases with incorporation of organoclay, regardless of the phase in which the nanoclay particles are localized. In summary, the obtained results show that regardless of the phase in which the nanoclay is localized, the morphology, and hence the properties, of the ternary composites are superior to those of the neat blend. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46193.

The effect of well-dispersed nanoclay on isothermal and non-isothermal crystallization kinetics of PHB/LDPE blends

The crystallization kinetics of PHB/LDPE blends and their nanocomposites containing different LDPE and organoclay loadings was investigated using DSC. Nanoclay localization in the PHB phase was determined by XRD and confirmed by rheological measurements and TEM. The rate and other kinetic parameters for crystallization were investigated using theoretical models, such as Avrami, Liu–Mo and Friedman. The effect of nanoclay on the first stage of crystallization was explored, based on Dubreva’s nucleation activity analysis. The Friedman model results showed that incorporation of either nanoclay or LDPE would increase the PHB activation energy of crystallization through two different mechanisms, namely increasing the viscosity and nuclei migration, respectively. Interestingly, the activation energy of PHB/LDPE nanocomposites was not as high as that of PHB/LDPE binary blends. This finding was also observed in isothermal and non-isothermal kinetics studies and could be explained by nuclei transfer from the PHB phase to the melt phase. According to Avrami exponent values, neither Cloisite 10A nor LDPE changed the nucleation mechanism of PHB. Incoroporation of LDPE successfully reduces rigid amorphous amount.

Manipulation of the properties of PLA nanocomposites by controlling the distribution of nanoclay via varying the acrylonitrile content in NBR rubber

Nanocomposites based on blends of polylactide (PLA), acrylonitrile butadiene rubber (NBR) and 4 wt% organically modified nanoclay (Cloisite 10A) were prepared via melt compounding. To investigate the influence of NBR acrylonitrile (ACN) content on the dispersion state and localization of nanoclay and micromorphology of the blends, three different NBRs with low (19%), medium (33%) and high (51%) ACN content were employed. Nanocomposites with low ACN NBR exhibited higher dispersion of clay nanolayers within the PLA matrix, whereas increase in ACN content gave rise to the localization of silicate platelets within the interface of two phases which was consistent well with the enhanced interfacial interaction between PLA and NBR phases that was evidenced by surface tension and melt rheology analysis. The size of dispersed NBR droplets decreased by the incorporation of organoclay into the composition of all PLA/NBR blends irrespective of the ACN content. However, the reduction in NBR droplet size by the nanoclay layers showed to be more pronounced for the nanocomposites based on high ACN rubber phase as a result of higher localization of nanoclay platelets within the interface of the PLA and NBR. All nanocomposites exhibited significant increase in elongation at break than simple blend counterparts, implying intensification of PLA and NBR interface by nanoclay incorporation.

Effect of nanoclay localization on the peel performance of PE based blend nanocomposite sealants

Polyethylene (PE) based clay polymer nanocomposites (CPN) are of great importance to generate peelable seals in packaging industry. This study shows the significant effect of organoclay (OC) localization in PE-based blend sealants on their peel properties, for the first time. Two different immiscible blends composed of PE/ethylene-methyl acrylate copolymer (EMA) and PE/ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA-GMA) were examined for their potential to generate peelable seals upon addition of organo-modified montmorillonite (OMt). WAXD results and TEM observations reveal that OC is localized at the interface of PE/EMA phases while it is localized within the dispersed EMA-GMA phase in the PE/EMA-GMA blend, which is in agreement with the thermodynamic predictions. The incorporation of 4 phr OC converts the lock seal behavior of the PE/EMA blend seal to a peelable behavior over a wide peelable heat seal temperature range (over 35°C). In contrast, the OC/PE/EMA-GMA nanocomposite sealant, in which OC is mostly located within the EMA-GMA phase, shows lock seal performance similar to the PE/EMA-GMA neat blend.

Dynamics of migration and phase selective localization of nanoclay in HNBR/ENR blends

ABSTRACTThe phase specific selective localization and dynamics of migration of nanoclay in hydrogenated acrylonitrile butadiene rubber (HNBR)/epoxidized natural rubber (ENR) blend systems is investigated. The phase specific dispersion of clay particles is monitored through measuring the online measured electrical conductance (OMEC) during mixing by means of a sensor system installed inside the chamber of an internal mixer. The results of different characterization techniques, such as atomic force microscopy, transmission electron microscopy, and small angle X‐ray scattering have been used to understand and interpret the OMEC behaviors of nanoclay‐filled rubber compounds individually (HNBR and ENR) and their blend systems. The observed online conductance is ionic in nature that arises due to the release of surfactant molecules from the clay galleries. It is observed that the OMEC behavior depends mainly on two factors: the localization of nanoclay in specific phase of the blend system and on the gradual development of blend morphology. The OMEC behavior and the supported data from the microscopic methods, clearly reveal the migration of organoclay from the ENR to HNBR phase during the mixing process, particularly localizing near the interface of the blend. Further, the localization of organoclay is also evaluated by applying the surface tension measurements based model, which also predicts the favorable localization of organoclay in HNBR phase of the blend. The work clearly suggests the OMEC method to be a powerful online tool to monitor and control the nanoclay dispersion and localization in rubber based nanocomposites during the melt mixing process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44074.

The Effect of Blending Sequence on Nanoclay Partitioning and Microfibrillar Morphology in Blend Nanocomposite Fibers

ABSTRACTThe aim of this article was to provide an insight into the effect of nanoclay partitioning on the droplet deformation and fibril formation in melt-compounded polypropylene/poly (butylene terephthalate)/organoclay blend nanocomposite fibers prepared by different blending sequences. An attempt was also made to investigate the effect of compatibilizer on the partitioning of nanoclay in these blend systems. Melt viscoelastic behavior, wide angle X-ray diffraction and transmission electron microscopy, along with scanning electron microscopy, revealed that the localization of nanoclay in the poly (butylene terephthalate) dispersed phase reduced the droplet deformation and fibril formation. It was demonstrated that the best microstructure of the blend nanocomposites for the fibrillation process was to have the maximum percentage of exfoliated nanoclay in both polymeric phases. Incorporation of compatibilizer can develop the microfibrillar morphology due to its assisting role in transferring a higher fraction of nanoclay platelets from droplets into the matrix and also increasing the extent of melt intercalation in the matrix.

Application of linear rheology in determination of nanoclay localization in PLA/EVA/Clay nanocomposites: Correlation with microstructure and thermal properties

A series of single step melt processed PLA/EVA immiscible blends and their organoclay filled nanocomposites in presence and absence of PTW as a compatibilizer were analyzed in terms of morphological, rheological and thermal properties. Alterations in these properties as a result of change in concentration of each component were correlated with each other. SEM results indicated that morphological response is more sensitive to incorporation of organoclay than compatibilizer presence. TEM and WAXS analyses indicated that simultaneous use of compatibilizer and organoclay in blends changes localization of organoclay and leads to its migration from thermodynamically favored phase towards interface. The selective localization of organoclay and compatibilizer effect on this phenomenon were also investigated by rheological and thermal properties analyses. The rheological properties of the multicomponent systems were investigated using linear viscoelastic measurements with a parallel plate rheometer at small strain amplitudes. By comparing trends of storage modulus of neat blend and its associated compatibilized and uncompatibilized nanocomposites at high and low frequencies and also cross over point between G′ and G″ curves, localization of organoclay and effect of compatibilizer on its microstructure could be well explained and correlated with the morphological findings. Moreover it was shown that the linear rheology method is superior over the other implemented experimental methods in precisely tracing microstructural changes in the nanoclay filled multicomponent systems. Finally, using differential scanning calorimetry in non-isothermal mode it was indicated that crystallization of PLA phase may be altered positively or negatively depending on the morphological characteristics, concentration and location of organoclay in the multicomponent system.

Structural, rheological, and mechanical properties of PA6/SAN/SEBS ternary blend/organoclay nanocomposites

ABSTRACTThe aim of this study was to investigate the effect of nanoclay addition on the morphological and mechanical properties of PA6/SAN/SEBS ternary blend. Two different nanoclays with different modifiers and two different mixing sequences were used to investigate the role of thermodynamic and kinetic, respectively, in the nanoclays localization. XRD, SEM, TEM, melt rheology, tensile and Izod impact tests were used to characterize the nanocomposites. Results of characterization of nanocomposites showed that clay localization is a very influential parameter to determine the type of morphology and, consequently, mechanical properties of ternary/clay nanocomposites. It was demonstrated that presence of nanoclay in the matrix results in the increase of stiffness, while localization of nanoclay at the interface improves the toughness and tensile strength. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41969.

Tuning the processability, morphology and biodegradability of clay incorporated PLA/LLDPE blends via selective localization of nanoclay induced by melt mixing sequence

Polylactic acid (PLA)/linear low density polyethylene (LLDPE) blend nanocomposites based on two different commercial-grade nanoclays, Cloisite ® 30B and Cloisite ® 15A, were produced via different melt mixing procedures in a counter-rotating twin screw extruder. The effects of mixing sequence and clay type on morphological and rheological behaviors as well as degradation properties of the blends were investigated. The X-ray diffraction (XRD) results showed that generally the level of exfoliation in 30B based nanocomposites was better than 15A based nanocomposites. In addition, due to difference in hydrophilicity and kind of modifiers in these two clays, the effect of 30B on refinement of dispersed phase and enhancement of biodegradability of PLA/LLDPE blend was much more remarkable than that of 15A nanoclay. Unlike the one step mixing process, preparation of nanocomposites via a two steps mixing process improved the morphol- ogy. Based on the XRD and TEM (transmission electron microscopic) results, it is found that the mixing sequence has a remarkable influence on dispersion and localization of the major part of 30B nanoclay in the PLA matrix. Owing to the induced selective localization of nanoclays in PLA phase, the nanocomposites prepared through a two steps mixing sequence exhibited extraordinary biodegradability, refiner morphology and better melt elasticity.

On nanoclay localization in polypropylene/poly(ethylene terephthalate) blends: Correlation with thermal and mechanical properties

A series of melt processed clay filled-PP/PET immiscible blends were analyzed in terms of thermal and mechanical properties combined with a theoretical analysis using a mechanical model for probing nanoclay localization in the blends influenced by blend composition, nanoclay content and type of matrix (PET-rich and PP-rich). According to the results obtained from DSC technique, it was shown that localization of nanoclay in the blend systems can be detected by analyzing changes in crystallization temperature and crystallinity of polymer components of the blend systems. From the tensile test results, it was revealed that tensile strength of the blend systems was affected by localization of nanoclay in the matrix phase, only. There was observed no compatibilization effect of nanoclay localized at interface of the blends, on mechanical properties improvement. Also, it was revealed that localization of nanoclay particles in matrix phase resulted in their more efficiency to increase tensile modulus than that localized in disperse phase. However, this efficiency was still dramatically low as compared to that predicted by Hui–Shia model.

Dynamic and Transient Shear Start‐Up Flow Experiments for Analyzing Nanoclay Localization in PP/PET Blends: Correlation with Microstructure

AbstractDynamic and transient shear start‐up flow experiments along with TEM, WAXS, and SEM analyses are performed on PP/PET blends and nanocomposites. The TEM results along with a theoretical analysis based on a thermodynamic model reveal that the clay particles are mainly localized in the PET phase. The localization of nanoclay in PET as the matrix phase leads to a refinement of morphology. The localization of clay is also studied by analyzing changes in complex viscosity and storage modulus in oscillation mode as well as the changes in power law index obtained from steady‐state and transient shear start‐up flow experiments. The changes in the rheological behavior of the blends are attributed to formation of clay network‐like structures.magnified image

Influence of nanoclay on the rheological properties of polyamide 6/acrylonitrile butadiene styrene nanocomposites

AbstractThe objective of this paper is to study the influence of nanoclay on rheological behavior and phase morphology of immiscible polyamide 6/acrylonitrile butadiene styrene (PA6/ABS) blends. For this purpose, the rheological behavior of PA6/ABS/Nanoclay blends such as storage modulus, relaxation time mechanism, zero‐shear viscosity, interfacial relaxation time, relaxation modulus, interface modulus, and the relationship between rheology and morphology was investigated. It was observed that the relaxation time (λ) and zero‐shear viscosity (η0) increases by increasing of the nanoclay (2–6 wt %) and ABS (15–35 wt %) content. As, the increase in relaxation time of PA6/ABS/Nanoclay blends with increasing of the nanoclay explained through deformation of droplets and the physical interactions across the interface that causes to enhancement of elasticity behavior at low frequencies. In other words, this occurrence causes the relaxation time slightly shifted toward higher values by increasing of nanoclay loading. The relaxation time spectrum caused by the interfacial tension of the droplets can be calculated by subtracting the contribution of the components from the nanocomposite spectrum reported by Gramespacher and Meissner. The results of the study show that the nanoclay localization in blend can be suggested from H(λ)λinterface as a function of relaxation time diagram which nanoclay plates located in matrix, disperse phase, or interphase. In addition, the slopes of relaxation modulus curves decrease by increasing nanoclay and ABS weight fraction, indicating that the relaxation time increases with the addition of nanoclay. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Morphology development and compatibilization effect in nanoclay filled rubber blends

The present work introduces a new method for the characterization of morphology development and kinetics of nanoclay distribution in hydrogenated acrylonitrile butadiene rubber (HNBR)/natural rubber (NR) blends based on the measurement of electrical conductance during the mixing process. It was found that the online measurable electrical conductance of rubber–clay mixtures, which is originated from the release of the ionic surfactant from the nanoclay galleries during the mixing process depends on two factors: the phase specific localization of nanoclay and the change of the blend morphology. The former is due to the favorable interaction of nanoclay with one of the blend phases whereas the latter is caused by the compatibilization effect of nanoclay. It became obvious that the presence of clay influences the morphology of the blends drastically; a significant change from the co-continuous phase morphology into an island–matrix morphology was observed in HNBR/NR/clay nanocomposites. Thus, the method of the online conductance promises to be a powerful tool to study the nanoclay dispersion processes and to monitor the quality of rubber–nanoclay composites.