Cloisite 20A Research Articles

Evaluation of the genotoxic potential of modified clays destined to food packaging through the micronucleus assay

Maleated poly(propylene carbonate) (PPC-MA)/organo-montmorillonite (OMMT) nanocomposites were first prepared via melt end-capping poly(propylene carbonate) (PPC) with maleic anhydride (MA) and melt-mixing the PPC-MA with commercial OMMT without and with hydroxyl groups in surfactants: Cloisite 20A (C20A) and Cloisite 30B (C30B), respectively. Intercalated and partially delaminated morphologies were corroborated via X-ray diffraction (XRD) and transmission electron microscopy (TEM). Dynamic mechanical analysis (DMA) revealed that PPC-MA was evidently reinforced by the partially delaminated C30B platelets. From XRD patterns of statically annealed PPC-MA/C20A and PPC-MA/C30B mixtures and Fourier transform infrared (FTIR) results of equivalent nanocomposites, partial delamination of C30B in PPC-MA was confirmed to be relevant to diffusion of PPC-MA molecular chains in C30B galleries, grafting of PPC-MA to C30B platelet surfaces and further separation of C30B platelets.

Microstructure and Properties of Polypropylene/Clay Nanocomposites

ABSTRACTNanocomposites of polypropylene (PP) containing various contents of Cloisite 15A nanoclay particles were prepared by one-step melt compounding in a twin screw extruder. Tensile and impact properties of the nanocomposite systems were investigated and correlated with their microstructures. The tensile modulus increased with an increase in Cloisite 15A content but the tensile strength, elongation at break, and impact strength were decreased. WAXS and TEM studies showed almost exfoliated structures. There was a decrease in permeability values with an increase in nanoclay content up to 5 wt. %. Exceeding this content of nanoclay had no significant effect on permeation due to the aggregation phenomenon at high concentrations of the nanoparticles. Most of the examined micromechanical models for prediction of the tensile modulus of the nanocomposite were successful despite being based on fiber-shaped fillers. An exfoliated structure of clay within the nanocomposite was assumed for the modeling using a molecular dynamics simulations approach, employing Dreiding, Forcite, and COMPASS force fields, in order to investigate the best one for a successful estimation of elastic modulus. Relative to the experimental modulus values of the nanocomposites, which were around 1100–1200 MPa, the COMPASS force field had the best correlation with the values with a slight departure of about 10%.

Dispersion study of clay nanoparticles in vinylester resin

Resistance to sea‐water penetration in fiber‐reinforced polymer composites is highly desirable for marine applications. This can be achieved by incorporating nanoparticles into polymer matrix, due to high aspect ratio of the platelets where small percentage of nanoclay particles properly dispersed in matrix can generate very large surface area for polymer/filler interactions. However, effective dispersion aiming for exfoliation and intercalation of nanoclays in resin is one of the major challenges faced for manufacturing of nanocomposites. In the present work, a suitable protocol is established for effective dispersion of Cloisite 15A nanoparticles in vinylester resin matrix. Dispersion study is conducted for different loading levels of nanoparticles and parameters are optimized. The extent of dispersion is characterized by performing X‐ray diffraction and high resolution transmission electronic microscopic image analysis. It is found that overnight swelling of nanoclays in resin followed by 45 min of ultrasonication at 220 V, 50–60 Hz frequency and 0.5 cycle per sec results in good amount of interaction with certain degree of exfoliation for loading level up to 6%. The nano particle dispersed resin is characterized to study the effect of nanoparticles on key manufacturing properties of resin matrix like rheology and cure kinetics. J. VINYL ADDIT. TECHNOL., 23:E51–E57, 2017. © 2016 Society of Plastics Engineers

Influence of blend composition and organic cloisite 15A content in the structure of isobutylene–isoprene rubber/ethylene propylene diene monomer composites for investigation of morphology and mechanical properties

A melt mixing method was used for preparation of immiscible isobutylene–isoprene rubber/ethylene propylene diene monomer blends and their polymer nanocomposites containing cloisite 15A nanoparticles. The morphology of nanocomposites was characterized by Fourier transform infrared spectroscopy and scanning electron microscope techniques. The dispersion of nanoclay in isobutylene–isoprene rubber/ethylene propylene diene monomer blends was studied by transmission electron microscopy and XRD analyses. Curing data of the prepared nanocomposites showed a decrease in scorch time (t5) and optimum cure time (t90) with increasing nanoclay content. Intercalation of rubber chains into the organoclay silicate layers was specified by d-spacing amount estimated according to the XRD results. Based on XRD results, a leftward shift towards lower diffraction angles in the organoclay characteristic peak was observed, indicating an increase in the d-spacing values in comparison with the pure organoclay. It confirms the intercalation of elastomer chains into the nanoclay galleries. The mechanical properties of the polymer nanocomposite specimens including hardness, fatigue strength, elongation at break, modulus and tensile strength were found to be better with increasing the nanoclay content. Also, resilience of the polymer nanocomposites decreased.

Flame Retardant Polyamide Fibres: The Challenge of Minimising Flame Retardant Additive Contents with Added Nanoclays.

This work shows that halogen-free, flame retarded polyamide 6 (PA6), fabrics may be produced in which component fibres still have acceptable tensile properties and low levels (preferably ≤10 wt %) of additives by incorporating a nanoclay along with two types of flame retardant formulations. The latter include (i) aluminium diethyl phosphinate (AlPi) at 10 wt %, known to work principally in the vapour phase and (ii) ammonium sulphamate (AS)/dipentaerythritol (DP) system present at 2.5 and 1 wt % respectively, believed to be condense phase active. The nanoclay chosen is an organically modified montmorillonite clay, Cloisite 25A. The effect of each additive system is analysed in terms of its ability to maximise both filament tensile properties relative to 100% PA6 and flame retardant behaviour of knitted fabrics in a vertical orientation. None of the AlPi-containing formulations achieved self-extinguishability, although the presence of nanoclay promoted lower burning and melt dripping rates. The AS/DP-containing formulations with total flame retardant levels of 5.5 wt % or less showed far superior properties and with nanoclay, showed fabric extinction times ≤ 39 s and reduced melt dripping. The tensile and flammability results, supported by thermogravimetric analysis, have been interpreted in terms of the mechanism of action of each flame retardant/nanoclay type.

Characterization of Bionanocomposites PHB, PEG and Organophilic Clay

In this study, it was investigated the structural and morphological characteristics of bionanocomposites of poly (3-hydroxybutyrate) (PHB), containing 5% polyethylene glycol (PEG), 1% and 3% two types of organoclays (Cloisite 20A and vermiculite). The systems in the form of films were prepared by the method of intercalation solution. The films were characterized by X-ray diffraction (XRD) spectroscopy and Fourier transform infrared (FTIR). It was observed that, according to the type of clay used, the systems showed intercalated structures or partially exfoliated ones. Regarding the FTIR results, they indicated that the addition of different clays to the PHB/PEG blend did not promote significant changes in the chemistry of the polymer matrix.

Morphological Analysis of Membranes of PES/Commercial Clay

The separation membrane processes are still fresh, but have had a lot of attention because they present attractive, such as low energy consumption, greater operating flexibility and better quality in the final product. Obtaining membranes incorporating clay is attracting interest because it improves the membrane filtration properties. In this study, pure polymer membranes were produced from poly (ether sulfone) and clays Cloisite Na and 20A, the levels of 1, 3 and 5% from the phase inversion technique using the dimethylformamide solvent. XRD results indicated the presence of a peak at both at about 15.8° compositions indicating that the systems are possibly intercalated and/or microcomposites structures. SEM results showed that the membranes with clay showed different behavior in relation to pure PES membranes. They apparently exhibited a surface without pores with exception of membrane with 5 wt.% Na Cloisite, which showed pores on its surface.

Development of cooler running PCR tire tread using SBR–ENR–nano clay composite

In this investigation, the emphasis is given to the partial replacement of carbon black by an optimized level of Cloisite 15A, an organoclay in a typical styrene-butadiene rubber (SBR) based passenger car tire tread compound. The effect of epoxidized natural rubber with 50 % epoxidation (ENR 50) on the properties of organoclay-SBR composite was also studied. Curing studies shows that both ENR 50 and nanoclay decreases the scorch time and cure time due to the activation of an adjacent double bond by the presence of epoxide group in the ENR and the amine groups present in the organic modifier in the nanoclay structure. The incorporation of ENR showed better dispersion and exfoliation of nanoclay in the rubber matrix. Synergistic reinforcement effect of high abrasion furnace carbon black (HAF/N330) on the mechanical properties, dynamic mechanical properties, heat build up and abrasion resistance in the SBR–ENR–clay nanocomposites having the optimized clay level was investigated. SBR–ENR–carbon black hybrids with 25 phr N330 and 6 phr nanoclay have shown better reinforcement, significantly lower heat generation, comparable/similar rolling resistance (indicated by tan δ at 60 °C) and wet skid resistance with that of conventional SBR–carbon black (40 phr N330) loaded composites.

An experimental study on low-velocity impact response of nanocomposite beams reinforced with nanoclay

The low-velocity impact (LVI) response of the unidirectional glass/epoxy laminated composites, which were reinforced with various contents of nanoclay (i.e., 0, 3, 5 and 7 wt %) was performed using a drop-weight impact machine. The nanocomposite beams were fabricated using two different methods, including hand lay-up (HLU) and vacuum assisted resin transfer molding (VARTM) methods, to evaluate the effect of the manufacturing method on the impact response. In addition, the influence of the nanoclay type on the impact response was assessed by using Cloisite 30B and Cloisite 15A. The quasi-static and LVI responses of the nanocomposite beams were compared, and the effect of nanoclay on the delaminated area after impact was also discussed. The comparative results of the experiments indicate that the samples fabricated via VARTM method, have a smaller damage area and more energy absorption than the HLU types. However, the beams with 5 wt % nanoclay have the highest energy absorption in both manufacturing methods. Moreover, the mechanism of smaller delaminated area with increasing nanoclay contents is explained according to the impermeable nature of nanoclays.

Influence of nanoclay on mechanical and thermal properties of glass fiber reinforced polymer nanocomposites

A novel approach was carried out to evaluate the effects of nanoclay in nanocomposite laminates based on mechanical properties, thermal analysis, and surface structure analysis. The composite panel was fabricated by reinforcing glass fiber with epoxy resin. Likewise, nanocomposite panels were fabricated by reinforcing glass fiber with nanoclay loaded epoxy. The loading of Cloisite 25A nanoclay in epoxy resin is varied as 2%, 4%, 6%, 8%, and 10% on weight basis. Upon completion of curing, the composite panel and nanocomposite panels were fabricated by using compression molding. The tensile test exhibited that the addition of nanoclay in epoxy resin has improved the tensile strength and Young's modulus by 33.39% and 15.88%, respectively for 2 wt% clay loading laminates than unfilled laminate. Likewise, the greater flexural strength of 438.04 MPa and flexural modulus of 22.12 GPa were attained for 2 wt% nanoclay/epoxy nanocomposite. The thermal results disclosed that greater thermal stability was attained between temperatures ranges from 0°C to 180°C for low clay content. The surface morphology too proved that the prepared laminates of 2 wt% loading exhibited appreciable surface property. POLYM. COMPOS., 39:1861–1868, 2018. © 2016 Society of Plastics Engineers

Toughening of polylactide nanocomposites with an ethylene alkyl acrylate copolymer: Effects of the addition of nanoparticles on phase morphology and fracture mechanisms

Melt compounding of polylactide with ductile polymers is widely proposed as an efficient alternative to overcome its inherent brittleness. An ethylene alkyl acrylate is used as toughening modifier of polylactide. A two‐phase morphology is detected by melt blending of Polylactide and Biomax Strong. Furthermore, the effect of the addition of organically modified nanoparticles, Cloisite 15A, on phase morphology is investigated. A transesterification reaction occurs between the matrix and the toughening modifier, leading to the formation of a terpolymer at the interface in the polymer blends, influencing the interfacial properties. This transesterification reaction is effectively catalyzed by the incorporation of the nanoparticles. The in situ formed terpolymer reveals a distinct glass transition, as the polylactide blocks along the terpolymer chain architecture restricted the segmental mobility of the ethylene alkyl acrylate blocks. The development of the terpolymer suppressed the decrease of the complex viscosity within the timeframe of the dynamic measurements. Multiple crazing is the major energy dissipation mechanism in the deformation of hybrids. The formation of an interconnected morphology in the hybrids triggers a remarkable toughening of polylactide, through the enhanced contribution of matrix plastic deformation. POLYM. ENG. SCI., 56:1415–1424, 2016. © 2016 Society of Plastics Engineers

Preferentially fixing nanoclays in the phases of incompatible carboxylated nitrile rubber (XNBR)-natural rubber (NR) blend using thermodynamic approach and its effect on physico mechanical properties

This work reports a unique thermodynamic approach for preferentially fixing nanoclays in the phases of incompatible carboxylated nitrile rubber (XNBR)/natural rubber (NR) blends prepared by solvent casting method. Projected for the first time in the area of polymer blend research, this study investigates different parameters, like (i) solubility parameter values of constituent blend components, nanoclays and solvents, (ii) interaction parameter (χ) values between the individual blend components/solvents and nanoclays/solvents, and (iii) difference in interaction parameter (χ) value between the constituent blend component/solvent and nanoclay/solvent and identifies their role in preferentially fixing nanoclays in the respective blend phases. For example, 83% of Cloisite 15A nanoclay (at 8 phr) is found in NR phase (when toluene is used as the solvent for dissolving the rubbers and for dispersing nanoclay) since the difference in interaction parameter value (0.04) between χNR/toluene−χCloisite 15A/toluene is lower when compared to the difference in interaction parameter value (0.17) between χXNBR/toluene−χCloisite 15A/toluene. Similarly, by judiciously choosing different solvents for dissolving the rubbers and for dispersing nanoclays it was possible to preferentially move nanoclay particles to different phases of XNBR/NR blend. The preferential fixing of nanoclays in a particular phase using the thermodynamic approach was quantified by dynamic mechanical analysis (DMA), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Selectively fixing the right nanoclay in the dispersed phase mutilated and suppressed the coalescence rate of the dispersed phase, which in turn lead to significant improvement in the overall properties.

Thermal stability and flammability of ethylene vinyl acetate copolymers in presence of nanoclay and a halogen‐free flame retardant

In this study, thermal stability behavior and flammability of ethylene‐vinyl‐acetate (EVA) copolymers containing organo‐modified nanoclay particles (Cloisite 15A) and ammonium polyphosphate (APP) along with pentaerythritol (PER), as halogen‐free flame retardants, were investigated. Transmission electron microscopy (TEM) and small‐angle X‐ray scattering (SAXS) were employed for evaluation of the level of dispersion of nanosheets within the EVA matrix. Moreover, thermal stability behavior and flammability of the samples were studied using thermogravimetric analysis (TGA), cone calorimetry thermometer (CCT) and limiting oxygen index (LOI). The obtained results from TEM and SAXS showed that nanosheets exhibited a rather proper level of dispersion within the EVA matrix. According to TGA and CCT results, despite improving the thermal stability and flame retardancy of EVA due to incorporation of the individual additives, a considerable synergistic effect was observed upon simultaneous use of clay nanosheets and the flame retardants. Such synergistic effect was explained by the physical mechanism of the solid phase due to the increased residual ash resulted from combustion of the samples containing flame retardants and clay nanosheets. While clay nanosheets had no significant effect on the LOI of EVA, the halogen‐free flame retardants substantially increased the LOI of EVA. J. VINYL ADDIT. TECHNOL., 23:E92–E98, 2017. © 2016 Society of Plastics Engineers

Polystyrene-based composites and nanocomposites with reduced brominated-flame retardant

Polystyrene was melt blended with a halogen-based flame retardant (FR), hexabromocyclododecane, and a non-halogenated FR, triphenyl phosphate (TPP), in a twin-screw extruder. An organically modified montmorillonite (Cloisite 15A) was used to prepare FR polystyrene nanocomposites. The flammability properties and thermal stability of FR polystyrene composites and nanocomposites were investigated. X-ray diffraction analysis showed that the exfoliation structure of organically modified montmorillonite in polystyrene nanocomposites may be achieved by melt-compounding in a twin-screw extruder. Furthermore, a good dispersion of FRs and nanoparticles of organically modified montmorillonite was observed by energy dispersive X-ray analysis. Thermogravimetric analysis demonstrated that the thermal stability of FR nanocomposites enhanced in the presence of clay nanoparticles and antioxidant. The aim of this study was to reduce the FR level, especially in the brominated FRs. The good results obtained by the limiting oxygen index test showed high-performance flammability properties in the composites containing hexabromocyclododecane and TPP, resulted from the synergy effects between these two FRs. However, in spite of producing high thermal performance polystyrene nanocomposites and dispersing clay nanoparticles efficiently into the polystyrene matrix, the flame retardancy properties were deteriorated in the presence of clay nanoparticles. Therefore, the organically modified clay (Cloisite 15A) was not a good synergic compound to improve the flame retardancy of polystyrene nanocomposites.

Effect of nanoclay on fatigue life of hot mix asphalt

ABSTRACTThe aim of this research is to investigate effect of two types of nanoclay additives, namely Cloisite 15-A and Cloisite 30-B, on fatigue life of asphalt mixes. Indirect tensile-resilient modulus and four-pointed beam fatigue tests were employed for this purpose. Results of both tests indicated that nanoclay additives improve fatigue life at 25°C but they have negative impact on it at 5°C. Moreover, Cloisite 15-A was found more effective at both temperatures regarding fatigue life.

Application of Organoclay Nanoparticle in Low-Density Polyethylene Films for Packaging of UF Cheese

Polymer/clay nanocomposites are a group of hybrid materials made from layered silicates of clay dispersed in the polymer matrix with a layer thickness in nanometre. The ability of organoclay nanoparticle including cloisite 15A, cloisite 20A and cloisite 30B incorporated into a low-density polyethylene (LDPE) polymeric matrix was investigated in order to inhibit the growth of coliform bacteria in ultra-filtrated cheese. The number of surviving cells of coliforms was decreased by 2.21 log cfu/g after 4 weeks storage at 4 ± 0.5°C, while pure LDPE showed a reduction of only 0.759 log cfu/g. LDPE film composed of 3% cloisite 15A, 3% cloisite 20A, with no cloisite 30B nano-filler was found as optimum point by combined design approach in design-expert analysis. The resulting film showed coliform load decreased by 2.05 log cfu/g in the optimum point, which was in line with Japanese industrial standard (JIS Z 2801: 2000) about antibacterial effect on coliform bacteria. A suitable microbial model for bacteria growth reduction was also suggested. Copyright © 2016 John Wiley & Sons, Ltd.

The Effects of Bagasse Fiber Loading on the Mechanical Properties of Skim NR–Clay Nanocomposites

Skim natural rubber (NR)–clay nanocomposites were prepared by a coagulation method using the organoclays Cloisite 15A, Cloisite 20A and Cloisite 30B. This work investigated the use of bagasse fiber developed from locally sourced and renewable material as an alternative and/or secondary filler in skim NR–clay nanocomposites. Bagasse fiber loading in the nanocomposites was 0, 5, 10 and 20 phr; the effects of fiber content on cure characteristics and mechanical properties were then determined. The results suggest that the Mooney viscosity tended to increase with increasing fiber content, whereas the cure time at 90% and fatigue testing score decreased as fiber loading increased.

Effect of electric field on polymer/clay nanocomposites depending on the affinities between the polymer and clay

ABSTRACTApplying an electric field is an efficient way to fabricate polymer/clay nanocomposites. It helps to achieve a good dispersion of nanoclays which improves the performance of the polymeric system. In this study, the effect of an alternating current (A.C.) electric field was investigated on clay exfoliation with various combinations of polymer/clay nanocomposites. Three different types of organoclays (Cloisite 10A, 20A, 30B) were introduced in polypropylene (PP) and poly(lactic acid) (PLA) matrices. Their rheological properties showed that the A.C. electric field was effective in enhancing the dispersion of organoclays in both the PP/clay and PLA/clay composites. The efficiency of the A.C. field varied depending on the combination of polymer and clay nanoparticles. In the case of PP, the best combination was PP/C20A followed by PP/C10A and PP/C30B. In contrast, PLA/clay showed an opposite trend. This difference arises from the different affinities between the polymers and the functional groups of the clays. The Hansen solubility parameter was introduced to quantify the affinities between the polymer and clay. The electric field was more effective for polymer/clay combinations that had less difference in the Hansen solubility parameter. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43582.

The effects of material formulation and manufacturing process on mechanical and thermal properties of epoxy/clay nanocomposites

A holistic study was conducted to investigate the combined effect of three different pre-mixing processes, namely mechanical mixing, ultrasonication and centrifugation, on mechanical and thermal properties of epoxy/clay nanocomposites reinforced with different platelet-like montmorillonite (MMT) clays (Cloisite Na+, Cloisite 10A, Cloisite 15 or Cloisite 93A) at clay contents of 3–10 wt%. Furthermore, the effect of combined pre-mixing processes and material formulation on clay dispersion and corresponding material properties of resulting composites was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), flexural and Charpy impact tests, Rockwell hardness tests and differential scanning calorimetry (DSC). A high level of clay agglomeration and partially intercalated/exfoliated clay structures were observed regardless of clay type and content. Epoxy/clay nanocomposites demonstrate an overall noticeable improvement of up to 10 % in the glass transition temperature (T g) compared to that of neat epoxy, which is interpreted by the inclusion of MMT clays acting as rigid fillers to restrict the chain mobility of epoxy matrices. The impact strength of epoxy/clay nanocomposites was also found to increase by up to 24 % with the addition of 3 wt% Cloisite Na+ clays. However, their flexural strength and hardness diminished when compared to those of neat epoxy, arising from several effects including clay agglomeration, widely distributed microvoids and microcracks as well as weak interfacial bonding between clay particles and epoxy matrices, as confirmed from TEM and SEM results. Overall, it is suggested that an improved technique should be used for the combination of pre-mixing processes in order to achieve the optimal manufacturing condition of uniform clay dispersion and minimal void contents.

The fabrication and properties of natural rubber-clay nanocomposites

Natural rubber-clay (NR-clay) nanocomposites were prepared by blending on a two roll mill. Organomodified Cloisite clay was used in this study. The effect of concentration of clay, type of clay and vulcanizing systems on the mechanical properties of nanocomposites were studied in detail. NR-clay nanocomposites were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis. X-ray results suggest that the intergallery distance is increased in all samples studied. There is good improvement in properties like tensile strength, elongation at break and modulus on incorporation of nanoclay in NR. TEM photographs show that exfoliation of the clay occurred at a concentration of 5 phr of cloisite 20A.