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

The 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.     

Comparative Study of the Effect of Addition of Silica and Silicate Nanofillers on the Properties of Epoxy Coatings

The effect of adding different amounts (0.5–3 wt%) of nanosilica (NS) and organomodified montmorillonite (MMT) to diglycidyl ether bisphenol A (DGEBA) cured with isophorone diamine at different temperature on the viscoelastic, topographical and gelation properties of epoxy resin was studied. Gel time measurements revealed that both NS and MMT accelerated the curing reaction of DGEBA with IPDA. Both nanofillers were adequately dispersed in DGEBA. The particle size distribution depended on the amount of nanofiller. A broader distribution for NS than for MMT filled epoxy was obtained. On the other hand, an increase in the curing temperature was required to obtain the intercalation of the epoxy into the MMT tactoids. At room temperature, the addition of NS increased both the stiffness (high storage modulus) and the toughness (an increase in the area and height of the tan δ curve) of epoxy, but no significant differences were found by curing at higher temperature. Epoxy/MMT composites showed higher storage modulus in the rubbery region. The improved properties imparted by NS can be ascribed to the interactions between the silanol moieties on the nanosilica surface and the polar groups in the epoxy, whereas the improvement imparted by MMT organoclay was related to tactoid intercalation within the epoxy matrix.     

The Effect of Structure of the Clay Modifier on the Morphology and Properties of Polystyrene/Clay Nanocomposites Prepared via In Situ Suspension Polymerization

Polystyrene (PS)/organoclay nanocomposites were prepared via free radical suspension polymerization. Two kinds of organoclay were used, labeled KT and KD, modified by trimethyloctadecyl ammonium (TM) and dimethyldioctadecyl ammonium (DM) ions, respectively. Nanocomposites containing various amounts of both of the organoclay nanoparticles (1, 3, and 5 wt%) were prepared. The wide angle X-ray diffraction (WAXD) results revealed intercalation in both of the nanocomposites. The greatest improvement in thermal stability of the nanocomposites was achieved with 5 wt% of organo-MMT for both of the clays. The nanocomposite containing 3 wt% of KT organo-MMT showed the greatest improvement of storage modulus. When the organoclay content exceeded 3 wt%, the storage moduli decreased compared to the nanocomposite filled with 3 wt% of the organoclay. D-spacing calculations using Bragg's law and WAXD data showed that the KT and KD nanoparticles were intercalated within the PS matrix, but with different extents of intercalation. The styrene conversions of the as-polymerized nanocomposite samples were obtained by a gravimetric method. The results showed that conversion decreased with incorporation of organoclay in the reaction recipe. Particle size was also increased by increasing nanoclay content.     

The Impact of Organoclay on the Physical and Mechanical Properties of Epoxy-Clay Nanocomposite Coatings

Nanocomposite coatings have recently been of interest because of their superior technical, environmental and economical advantages. Some new solvent free nanocomposite coatings were formulated using epoxy resin and montmorillonie (MMt) nanoclay. The organomodified MMt was well dispersed and partially exfoliated in the epoxy resin. The dispersion process comprised high-shear mixing and ultrasonication. The structure of the resultant coatings was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses. The effect of the clay content on the physical and mechanical properties of the resultant coatings, such as abrasion and impact resistance, hardness, and flexibility were measured and compared with unmodified coatings. The introduction of organoclay up to 4 wt% in coating systems resulted in improvement in the physical and mechanical properties such as hardness (micro and König) and abrasion resistance. Also an increment of up to 3 wt% of organoclay leads to an increase in the impact resistance and flexibility of resultant coating films. On the other hand, flexibility and impact resistance of the coatings containing more than 3 wt% of clay was decreased. The main reason for these observations was agglomeration of the clay particles for high clay-loading compositions.     

Effect of Organoclay Platelets on Crystallization of Polytrimethylene Terephthalate/Polyethylene-octene-g-maleic Anhydride Blends: Isothermal Crystallization

The blends of poly(trimethylene terephthalate) (PTT) with maleic anhydride-grafted poly(ethylene-octene) (POE-g-MA) and organoclay (OMMT) were prepared by melt-blending. The effects of organoclay platelets on the isothermal crystallization behaviors of PTT/POE-g-MA blend were examined using differential scanning calorimetry. The crystallization kinetics of the primary stage under isothermal conditions could be described by the Avrami equation, with values of the Avrami exponent between 2.01 and 2.81 for all samples. The crystallization rate parameter, K, decreased with increase of melt-crystallization temperature for all samples. The activation energies for isothermal crystallization were determined by the Arrhenius equation.     

Preparation and Characterization of Nano-Calcium Carbonate/Silane Coupling Agent Master Batch and Its Effect on Epoxy Resin

A nano-calcium carbonate (CaCO₃)/silane coupling agent (NCC/SCA) master batch was prepared by the reaction of SCA (γ-aminopropyl triethoxy silane, trade name KH550) with the hydroxyl groups of nano-CaCO₃. Both Fourier transform infrared spectroscopy and thermal gravimetric analysis indicated that the nanoparticles were grafted by SCA. An epoxy resin was modified by adding the NCC/SCA master batch. A simple dipping test suggested that a better dispersion of the treated NCC in epoxy could be obtained than that of the untreated NCC. Then samples of epoxy nano-composites were prepared by a hot press process. The compressive property of epoxy nano-composites was investigated; the results of these mechanical property tests revealed that the compressive strength, elastic modulus, and the total fracture work of the epoxy matrix filled with the treated NCC were significantly improved relative to that filled with the untreated NCC.     

Effectiveness of Maleic Anhydride Grafted EPDM Rubber (EPDM-g-MAH) as Compatibilizer in NR/Organoclay Nanocomposites Prepared by Melt Compounding

The effectiveness of maleic anhydride grafted ethylene propylene diene monomer rubber (EPDM-g-MAH) as an interfacial compatibilizer in enhancing the extent of interaction between natural rubber (NR) matrix and organoclay (OC) nanolayers, and also the eventually developed microstructure during a melt mixing process, has been evaluated as an alternative material to be used in place of commonly used epoxidized NR with 50 mol % epoxidation (ENR50). The latter usually weakens the processability of the final compound. The curing behavior, rheological, and dynamic mechanical properties of the prepared nanocomposites have been evaluated. Microstructural characterizations revealed better interfacial compatibilization by EPDM-g-MAH than ENR50, which is attributed to the lower polarity of the EPDM-g-MAH and hence more affinity for the NR matrix to be diffused onto the galleries of OC. This was confirmed with transmission electron microscopy (TEM) examination and higher elasticity exhibited by the unvulcanized NR/OC/EPDM-g-MAH nanocomposites in melt rheological measurements. Also, lower damping behavior was observed for the vulcanized NR/OC/EPDM-g-MAH samples. These imply intensified polymer–filler interfacial interaction and hence restricted viscous motions by the NR segments. Vulcanized NR/OC nanocomposites compatibilized with EPDM-g-MAH showed greater enhancements in tensile properties than the sample compatibilized with ENR50.     

Preparation and Properties of Epoxy‐Clay Nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of adding different contents of nanoclays on the physical, mechanical, and thermal properties of the epoxy resin system used in composite pipes manufacturing. Diglycidyl ether of bisphenol‐A (epoxy) with a cycloaliphatic amine heat curing hardner was reinforced by 1–7 wt.% of an organically modified type of montmorillonite. SEM results showed the change in failure of epoxy from brittle to tough mode by addition of nanoclays. X‐ray results indicated some degree of exfoliation by 1 wt.% clay and a decrease in d‐spacing in higher clay loadings after that. The heat‐distortion temperature of epoxy-clay nanocomposites increased from 125.5 to 138.7°C with 3 wt.% organoclay loading. Tensile and flexural modulus increased with increasing clay loading in this type of nanocomposite, but addition of organically modified clay decreased the tensile and flexural strengths and tensile elongation at break. Addition of 7 wt.% nanoclay improved the impact strength by 25.6%.     

Influence of Compatibilizer-Type and Processing Approach on the Dispersion of OMMT in High-Density Polyethylene Matrix

High-density polyethylene/organoclay nanocomposites were prepared via melt intercalation in an internal mixer using both a direct mixing and master batching method. Two types of maleic anhydride grafted polyethylene, high-density polyethylene grafted maleic anhydride, and linear low-density polyethylene grafted maleic anhydride, (HDPE-g-MA, LLDPE-g-MA) were used as compatibilizers to enhance the dispersibility of nanoclay in HDPE. Dispersion of organoclay in the nanocomposites was characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and rheological mechanical spectroscopy (RMS). Effects of clay content and degree of clay dispersion on the rheological and tensile properties were also investigated. Furthermore, the effect of order of mixing on the dispersion and distribution of the clay layers was studied. The obtained results showed that organoclay in the nanocomposites were dispersed homogeneously and exfoliated better when HDPE-g-MA and the direct mixing route were used. Although in the master batching method clay intercalated better, clay layers chiefly remain in compatibilizer rich areas. On the other hand, direct mixing was observed to lead to clay particles being dispersed in the HDPE matrix or at the interface of the matrix and compatibilizer and, consequently, better improvement in the tensile modulus was achieved. It was determined that the compatibilizer with the higher miscibility with the matrix was the key factor for achieving better exfoliation of clay sheets.     

Curing behavior and physical properties of an epoxy nanocomposite with amine-functionalized graphene nanoplatelets

Amine-functionalized graphene nanoplatelets (AGNPs) were prepared via an easy simple one-step process, treating graphite powder with 4-aminobenzoic acid in polyphosphoric acid, and then the effects of the AGNPs on the curing and physical properties of an epoxy resin were studied. The formation of the AGNPs was confirmed by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy, and thermogravimetric analyzer. Curing behavior of the epoxy/AGNPs nanocomposite was investigated by differential scanning calorimeter. The AGNPs made the epoxide curing reaction with amine groups slightly faster. The physical properties of the epoxy/AGNPs nanocomposite were investigated by dynamic mechanical analyzer, thermomechanical analyzer, and impact test. The AGNPs improved T_g by 21.4 °C, and storage modulus and impact strength of the epoxy resin 23 and 73%, respectively, much more effective than the graphite powder at the same filler loading of 1 phr. SEM images for the fracture surfaces of the epoxy/AGNPs nanocomposite showed improved interfacial bonding between the epoxy matrix and the nanofillers due to the amine functional groups of the AGNPs.     

Morphological and Rheological Properties of Poly(Trimethylene Terephthalate)/Maleic Anhydride Grafted Poly (Ethylene-Octene)/Organoclay Ternary Nanocomposite

Poly(trimethylene terephthalate) (PTT)/poly(ethylene-octene) POE-g-MA/organoclay ternary nanocomposites were prepared using melt blending in order to simultaneously improve the toughness and stiffness of PTT. The phase morphology and dispersion of organoclay were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), and transmission electron microscopy (TEM). The melt rheological behavior of the ternary nanocomposites was determined by plate/plate rheological measurements. XRD and TEM analysis indicated that the ternary nanocomposites contained exfoliated nanoparticle when a small amount of organoclay (1 part per hundred) was added. The high aspect ratio of the organoclay platelets induced the average size of the dispersed domain to become smaller. Melt rheological studies revealed that the ternary nanocomposites exhibited strong shear thinning behavior and showed good processability.     

3D multiscale modeling to predict the elastic modulus of polymer/nanoclay composites considering realistic interphase property

The elastic modulus of a nanocomposite reinforced with nanoclay was studied using the 3D finite-element method. It is widely accepted that interphase between nanoparticle and matrix plays an important role in the performance of the nanocomposite. Thus, a representative volume element (RVE) consisted of three phases (i.e. matrix, interphase and nanoclay) was simulated. In addition, to have a realistic estimation of elastic modulus of the interphase region, the modulus was computed using the available analytical formula. Since the nanoclays have been known as platelets and to investigate the effect of the third dimension, the nanoclay was simulated as a thin cuboid. The effect of various geometrical parameters, such as the change of the nanoclay contact area at a constant volume fraction of nanoclay, the variation of the nanoclay angle in the planes perpendicular and parallel to the loading direction, and the RVE dimensions, on the elastic modulus of a nanocomposite was considered. The results revealed that the increase in contact area of the nanoclay at a constant volume of nanoclay led to an increase in the elastic modulus of the nanocomposite. Furthermore, the change in the angle of nanoclay with respect to the plane parallel to loading direction has considerable effects on the elastic modulus of the nanocomposite, whereas this effect is negligible for the alignment angle perpendicular to the plane of the loading direction. Finally, unlike the previous studies, the results of the finite-element modeling were compared with three-phase theory of Mori–Tanaka.     

Effect of interfacial bonding on impact properties of chopped glass fiber polymer nanocomposites

This paper aims to presents the investigations made on the effect of impact response of chopped glass fiber–epoxy nanocomposite laminates subjected to low velocity impact using instrumented falling weight impact tests. The laminates were prepared using six layers of chopped strand mat with density of 610 gsm with epoxy resin and nanoclay content varied from 1, 3, and 5 wt%, by hand lay-up method. The nanoclay was dispersed into the epoxy by high shear mixing process in order to obtained uniform distribution of individual nanoclay. Laminates were impacted at constant mass with different impact energies. During these low velocity impact tests, the maximum load, absorbed energy, and deflection at peak load were recorded. It was observed that by dispersion of nanoclay as reinforcement, there was significant improvement in load carrying capacity and energy absorption. When a small amount of nanoclay (1 wt%) was added into the epoxy, the maximum load was enhanced by 20%. The presence of stiffer nanoclay significantly reduced the surface cracks propagation and controlled delamination area. Scanning electron microscopy was performed to characterize the damage progression.     

Interfacial bonding characteristic of nanoclay/polymer composites

Using a small amount of nanoclay (montmorillonite (MMT)) can significantly enhance the thermal and mechanical properties of polymer-based composites. Therefore, an in depth understanding of the bonding characteristic between the nanoclay and its surrounding matrix is essential. In this study, Fourier Transform Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were conducted to analyze the chemical composition between epoxy matrix and nanocomposite. These experiments revealed that a chemical bonding at an interface between the matrix and nanoclay of the composites did exist. Thus, such bonding can enhance the mechanical and thermal properties of resultant polymer composites as reported in many literatures.     

Study on Steady Shear,Morphology and Mechanical Behavior of Nanocomposites based on Polyamide 6

Nanocomposites of two different grades of polyamide 6 (PA6) with organically modified nanoclay were prepared via melt compounding in a twin‐screw extruder. The rheological behavior, morphology and mechanical properties of the nanocomposites were studied using a capillary rheometer, x‐ray diffraction (XRD), tapping‐mode atomic force microscopy (AFM), and tensile and flexural tests. XRD patterns indicate that the organically modified layered silicate was well dispersed in the PA6 matrix. From the AFM images the surface roughness of PA6 slightly increases with addition of organoclay. The rheological studies showed that the prepared nanocomposites have shear thinning behavior, obeying the power law equation. Addition of organoclay increases the shear stress and shear viscosity. At high rate of shear deformation the viscosity of nanocomposites are comparable to those of the pure polyamides. The activation energy of flow decreases with increasing nanoclay content. For most of the prepared nanocomposites the activation energy values increase with increasing shear rate. The tensile strength and flexural modulus and strength of the nanocomposites increase with increase of nanoclay content, but the extension at yield decreases with increasing clay loading.     

Toughening of Poly (Butylene Terephthalate) with Epoxy-Filled Poly (Ethylene–Octene) Copolymer

Toughened poly (butylene terephthalate) (PBT) with triglycidyl isocyanurate (TGIC)-filled poly (ethylene–octene) (POE) was prepared by melt reaction extrusion. For retarding the reaction extent between PBT and the epoxy component, the TGIC was first blended with POE to enwrap its reactive epoxy groups. Then, the TGIC-filled POE was used to melt blend with PBT. The Fourier transform infrared (FTIR) spectra showed that no other peaks appeared in the POE/TGIC specimens except for those originally existing in pure POE and TGIC. The rheological results further confirmed that no reaction occurred between the epoxy and the POE matrix. When the POE/TGIC was blended with PBT, a distinct increase of the viscosity suggested that the migration of the TGIC from POE to PBT during the melt processing induced chain extension reactions of PBT. The results obtained from DSC and DMA revealed that the chain extension of PBT induced by the reaction with TGIC restricted the mobility of PBT chains leading to a limitation of the recrystallization-remelting process and an increase of the glass transition temperature of PBT. The mechanical tests showed that the presence of TGIC in the POE phase distinctly improved the toughness of PBT. Compared to the case of a PBT/POE (80/20, wt%/wt%) blend, the elongation at break and impact strength of the system filled with 5 phr TGIC were increased more than three and six times, respectively.     

Influence of Surfactant Functional Groups on Morphology and Rheology of Polypropylene/Organoclay Nanocomposites

Three surfactants, with the same long alkyl tail but varying in functional groups, were selected to modify two pristine clays with different cation exchange capacities (CEC). Each of the modified clays was melt-mixed with polypropylene (PP) to prepare nanocomposites. The microstructure of the resultant nanocomposites was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and rheological techniques. The results showed that the surfactant structure had remarkable effects on the morphology and shear rheology of the nanocomposites based on the high-CEC organoclay: use of benzyl functional groups led to the highest extent of intercalation and highest enhancement of shear properties, while use of 2-hydroxyethyl groups had the opposite effect. Nanocomposites based on low-CEC organoclay all exhibited poor dispersion and their shear behavior was changed only slightly in comparison to the polymer matrix. In the case of extensional rheology, strain hardening was observed only in the two nanocomposites containing surfactants with 2-hydroxyethyl groups, regardless of the dispersion state of the nanoparticles.     

Styrene Butadiene Rubber/Epoxidized Natural Rubber (SBR/ENR50) Nanocomposites Containing Nanoclay and Carbon Black as Fillers for Application in Tire-Tread Compounds

Nanocomposite vulcunizates based on a SBR/ENR50 (50/50%wt) rubber blend containing nanoclay (5 or 10 phr) with and without carbon black (CB 20 phr) were prepared by melt blending in an internal mixer. The compound containing 35 phr carbon black (only) was prepared as a reference sample. Microstructure of nanocomposite samples was investigated by using X-ray diffraction (XRD), melt rheo-mechanical spectroscopy (RMS), and scanning electron microscopy (SEM). The XRD patterns revealed that the distance between the clay layers were increased by adding CB to the nanocomposite samples; they caused better diffusion of chains between the layers and resulted in an intercalated structure. The RMS results also indicated the formation of the filler-filler networks. SEM images of fracture surfaces showed the presence of much roughness in the samples containing both nanoclay and CB compared to the other samples. The results obtained from application of the Flory–Rhener equation showed a high crosslink density for the sample with 10 phr nanoclay and 20 phr CB. Dynamic mechanical behavior, mechanical properties, and abrasion resistance of the nanocomposites were evaluated. The results indicated that the sample containing 10 phr nanoclay and 20 phr CB had an increased dynamic elastic modulus, reduced maximum loss factor (tanδ)_max,, and an improved tensile strength and abrasion resistance compared to the reference sample. Also, this sample showed the lowest maximum loss factor, at 50–60°C, so it can be a candidate for tire-tread application.     

Processing and properties of carbon nanofibers reinforced epoxy powder composites

Commercially available CNFs (diameter 30–300 nm) have been used to develop both bulk and coating epoxy nanocomposites by using a solvent-free epoxy matrix powder. Processing of both types of materials has been carried out by a double-step process consisting in an initial physical premix of all components followed by three consecutive extrusions. The extruded pellets were grinded into powder and sieved. Carbon nanofibers powder coatings were obtained by electrostatic painting of the extruded powder followed by a curing process based in a thermal treatment at 200 °C for 25 min. On the other hand, for obtaining bulk carbon nanofibers epoxy composites, a thermal curing process involving several steps was needed. Gloss and mechanical properties of both nanocomposite coatings and bulk nanocomposites were improved as a result of the processing process. FE-SEM fracture surface microphotographs corroborate these results. It has been assessed the key role played by the dispersion of CNFs in the matrix, and the highly important step that is the processing and curing of the nanocomposites. A processing stage consisted in three consecutive extrusions has reached to nanocomposites free of entanglements neither agglomerates. This process leads to nanocomposite coatings of enhanced properties, as it has been evidenced through gloss and mechanical properties. A dispersion limit of 1% has been determined for the studied system in which a given dispersion has been achieved, as the bending mechanical properties have been increased around 25% compared with the pristine epoxy resin. It has been also demonstrated the importance of the thickness in the nanocomposite, as it involves the curing stage. The complex curing treatment carried out in the case of bulk nanocomposites has reached to reagglomeration of CNFs.     

Investigation of Cell Structure and Expansion Ratio of Microcellular Polypropylene Nanohomocomposites Prepared by a Solid-State Process

Microcellular poly(propylene-ethylene) random copolymer (r-PP-PE)/nanoclay (nanocomposite) and r-PP-PE/nanoclay/polypropylene fibers (nanohomocomposite) were autoclave-foamed via a solid-state microcellular foaming process using supercritical N₂ as a foaming agent. Polypropylene grafted with maleic anhydride (PP-g-MA) was used as a compatibilizer. Amount of PP-g-MA to nanoclay was 3:1. This study investigated the effects of clay content and the presence of polypropylene fiber on the expansion ratio and cell morphology of the samples. The results indicated that nanoclay increased the expansion ratio of the samples, but the expansion ratio for nanohomocomposites was slightly lower than the nanocomposites. In addition, scanning electron microscopy (SEM) observation showed that the nanoclay decreased the cell size and increased the cell density, except for the nanocomposite with the highest nanoclay content, 3 wt%, which had larger cell size compared to the samples with 1.5 wt% nanoclay and less. On the other hand, the simultaneous presence of nanoclay and polypropylene fibers synergistically increased the cell nucleation effect; thus there was a dramatic increase in cell density. The Differential scanning calorimetry (DSC) analysis showed that the microcellular foaming process decreased the crystallinity of both types of samples.