Effect of halloysite nanoclay on mechanical properties,thermal behavior and microstructure of cement mortars

Many studies have targeted the application of clay in cement composites and declared some enhancement on the properties of concrete. However there is little knowledge on nanoclays and their effect on the mechanical properties and durability of cement composites. Halloysite nanoclay is one of the subcategories of nanoclay that has been undeservedly ignored in the production of cement composites. Chemically, the outer surface of the halloysite nanotubes has properties similar to SiO₂ while the inner cylinder core is related to Al₂O₃ which together may improve the cement matrix. In this study the mechanical properties, flowability, thermal behavior and durability of mortars containing 1, 2, 3% halloysite nanoclay were studied. Compressive strength and gas permeability of samples with 3% and 2% nanoclay were improved up to 24% and 56%, respectively. SEM, XRD, DSC tests were carried out to investigate the microstructure and chemical composition change in samples with halloysite nanoclay.     

Effect of processing procedures and conditions on structural,morphological, and rheological properties of polyethylene/polyamide/nanoclay blends

The article deals with the effect of processing procedures and conditions on structural, morphological, and rheological properties of ternary blends composed of polyethylene (PE), polyamide (PA)‐12, and organically modified montmorillonite nanoclay with selective affinity. Samples were prepared from PE/PA and PA/PE blends, either by simultaneous mixing or from a polymer/clay masterbatch, using two processing conditions. The results have shown the existence of a weight fraction threshold, above which no significant processing effect was observed. Below this weight fraction threshold, the results tend to underline the significant role of two parameters that depend on processing procedures and/or conditions: the contact time between PE and PA phases and the contact time between clay and PA. Clay structure, blend morphology, and rheological properties were all shown to depend on these two parameters, and also on the nature of the matrix (PE or PA), because of the selective affinity of clay toward polymer phases. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effects of nanoclay and coupling agent on the physico‐mechanical,morphological, and thermal properties of wood flour/polypropylene composites

This article presents the effects of coupling agent and nanoclay (NC) on some properties of wood flour/polypropylene composites. The composites with different NC and maleic anhydride grafted polypropylene (MAPP) contents were fabricated by melt compounding in a twin‐screw extruder and then by injection molding. The mass ratio of the wood flour to polymer was 40/60 (w/w). Results showed that applying MAPP on the surface of the wood flour can promote filler polymer interaction, which, in turn, would improve mechanical properties of the composite as well as its water uptake and thermal stability. Composite voids and the lumens of the fibers were filled with NC, which prevented the penetration of water by the capillary action into the deeper parts of composite. Therefore, the water absorption in composites fabricated using NC was significantly reduced. Scanning electron microscopy has shown that the treatment of composites with 5 wt% MAPP, promotes better fiber–matrix interaction, resulting in a few numbers of pull‐out traces. In all cases, the degradation temperatures shifted to higher values after using MAPP. The largest improvement on the thermal stability of composites was achieved when NC was added. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Effect of different compatibilisers on nanoclay dispersion,thermal stability,and burning behavior of polypropylene–nanoclay blends

The dispersion of nanoclays in nonpolar polypropylene (PP) is difficult without the use of a small fraction (1–3%) of modified grafted PP as a compatibiliser. This work reports the effect of different graft‐modified polypropylenes on the dispersion of nanoclays in PP, and thermal stability and flammability of the blends. PP has been compounded in a Brabender compounder with a selection of modified PP polymers as compatibilisers. The grafts include maleic anhydride, N‐ethylmaleimide, diethylmaleate, diethyl‐p‐vinylbenzyl phosphonate, and acrylic acid‐2‐[(diethoxyphosphoryl)methylamino] ethyl ester. Films were cast from the blends by compression molding and the nanocomposite structures assessed using X‐ray diffraction. Thermal characterization was performed using DSC and TGA, the burning behavior was observed using limiting oxygen index measurements, and cone calorimetry where samples were exposed to 35 kW/m² external heat flux. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Physical and mechanical properties of nanocomposite barrier film containing encapsulated nanoclay

Waterborne poly(styrene‐co‐butyl acrylate) was prepared via miniemulsion polymerization in which nanoclay (Cloisite® 30B, modified natural MMT) in different concentrations was encapsulated. Scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy confirmed the encapsulation and intercalated‐exfoliated structure of Cloisite® 30B within poly(styrene‐co‐butyl acrylate). The effect of nanoclay content on water vapor permeability, water uptake, oxygen permeability, thermal, and mechanical properties of thin films containing 1.5, 2.56, 3.5, and 5.3 wt % encapsulated Cloisite® 30B in poly(styrene‐co‐butyl acrylate) was investigated. The presence of encapsulated Cloisite® 30B within the polymer matrix improved tensile strength, Young's modulus, and toughness of the nanocomposites depending on the nanoclay content. Water vapor transmission rate, oxygen barrier properties, and thermal stability were also improved. The results indicated that the incorporation of Cloisite® 30B in the form of encapsulated platelets improved physicomechanical properties of the nanoclay‐polymer composite barrier films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of nanocrystalline cellulose on morphological,thermal, and mechanical properties of Nylon 6 composites

In this study, nanocomposites based on Nylon 6 and nanocrystalline cellulose (NCC) were prepared by melt compounding. Then, morphological, thermal, and mechanical properties were analyzed for NCC content between 0 and 7 wt%. Morphological analyses showed different roughness in fractured surface of neat Nylon and its nanocomposites caused by the presence of NCC. Mechanical results showed that the optimum properties were obtained at 3% NCC which could be related to relatively good NCC dispersion at low concentrations with good Nylon‐NCC bonding. Overall, flexural (41%) and tensile (23%) moduli, as well as tensile strength (11%) were increased up to 3% of NCC. However, elongation at break and impact strength decreased with NCC addition. Finally, density and hardness showed only a small increase of 5 and 3%, respectively. POLYM. COMPOS., 37:1473–1479, 2016. © 2014 Society of Plastics Engineers     

Effect of starch on thermal,mechanical, and barrier properties of low density polyethylene film

Low‐density polyethylene (LDPE) with different quantities of starch was compounded using a twin screw extruder and blown into films by a Konar K, blow‐film machine. Mechanical properties, namely percent elongation, tensile, bursting, and tear strength, as well as barrier properties, such as water vapor and oxygen transmission rate, of the filled LDPE film were studied. Thermal properties of the films were studied using DSC and DMA. Master curves at reference temperature of 30°C were obtained using software linked to DMA. Incorporation of 1% starch in LDPE has marginally affected the thermal, barrier, and mechanical properties; however, that of 5% starch filled LDPE has affected the properties to a great extent. The mechanical properties, such as percent elongation, tensile, tear, bursting, and seal strength, decreased by 19.2, 33.6, 3.60, 10.8, and 22.12%, respectively. Similarly, water vapor and oxygen transmission rate increased to 32.5 and 18.3%, respectively. Other physical properties, namely migration and thermal properties, were also affected in 5% starch filled LDPE; however, the film can still be used as packaging material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3355–3364, 2006     

Effect of nBaCO3 on mechanical,thermal and morphological properties of isotactic PP-EPDM blend

Isotactic polypropylene (iPP): ethylene propylene diene monomer (EPDM) blend is one of the most suited compatible and miscible blends. The blends of iPP and EPDM (80:20) filled with BaCO₃ nanoparticles (0.5, 1.5, 2.5 and 3 wt%) were prepared on Brabender Plasticorder, which was then subjected to injection molding to get dumbbell-shaped specimens. Meanwhile, BaCO₃ nanoparticles (nBaCO₃) were prepared using ultrasonic cavitation technique. The size and shape of nBaCO₃ particle was confirmed using transmission electron microscope and found to be capsule shape of diameter ~40–60 nm with aspect ratio (l/d) of 2.2–2.5. The reduction in particle size of nBaCO₃ leads to formation of uniform suspension. The solution was kept as such for long time so as to nullify the charges developed over the surface of nanoparticles. The mechanical properties of nBaCO₃-reinforced iPP-EPDM blends were studied using universal testing machine and impact tester. Moreover, thermal properties were studied using flammability tester, vicat softening temperature, thermo gravimetric analyzer and differential scanning calorimeter (DSC). Dispersion of nBaCO₃ in iPP-EPDM matrix was studied using scanning electron microscope and X-ray diffractometer. The mechanical and thermal properties of iPP-EPDM/nBaCO₃ blends were found to be improved significantly with increasing amount of nBaCO₃ up to 2.5 wt%, which is due to good compatibility in between iPP and EPDM with uniform dispersion of nBaCO₃. Moreover, due to agglomeration at 3 wt% loading of nBaCO₃ few of the properties found to be decreased marginally.     

Polypropylene nanocomposite film: A critical evaluation on the effect of nanoclay on the mechanical,thermal, and morphological behavior

Polypropylene (PP)/clay nanocomposites prepared by melt blending technique using different percentages of clay with and without maleic anhydride grafted PP (MA‐PP) were studied. The intercalated and exfoliated structure of nanocomposites was characterized by X‐Ray Diffraction (XRD) and transmission electron microscopy (TEM). Because of the typical intercalated and exfoliated structure, the tensile modulus of the nanocomposites were improved significantly as compared to virgin PP. The viscoelastic behavior of the nanocomposites was studied by dynamical mechanical analysis (DMA) and the results showed that with the addition of treated clay to PP there was substantial improvement in storage modulus increases. The thermal stability and crystallization of the PP nanocomposites as studied by differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA) were also improved significantly compared to PP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of acrylation on the properties of waterborne epoxy: evaluation of physicochemical,thermal, mechanical and morphological properties

The present work addresses the critical requirements for the coating industry such as developing the sustainability of biobased materials and simultaneously achieving a balanced combination of coating properties. In this study, acrylated epoxidized soybean oil (AESO) has been successfully synthesized from epoxidized soybean oil and acrylic acid. Subsequently, AESO was modified using a biobased long chain diacid (Pripol-1009) with the assistance of a water/ethanol blend to form waterborne epoxy acrylate (WBEA). The properties of the cured WBEA with 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane as initiator were studied through spectral analysis, coating properties evaluation, corrosion resistance, and morphological and thermal analysis. The results revealed that WBEA exhibited relatively better mechanical, thermal and corrosion resistance characteristics over cured waterborne epoxy.     

Effect of processing routes on the mechanical, thermal and morphological properties of PLA-based hybrid biocomposite

Due to environmental awareness and depletion of petroleum oil, bioplastics and their composites are one of the most researchable topics throughout the world. Polymers that are produced from renewable sources are expected to be the best alternative to replace conventional polymers. The bottles neck of these bioplastics is its cost which limits its application in certain purposes. Bioplastics filled or reinforced with natural fibers can reduce cost and improve properties, like stiffness, strength and toughness of biocomposites. Impact strength and fracture toughness are the main demerits of short fiber-filled biocomposite. On the other hand, when nanoclay, having a very high aspect ratio, is mixed with bioplastics it may significantly affect the thermal and mechanical properties of the final composites. A composite may also suffer dispersion inefficiency, which is considered the key factor to improve the properties. The aim of this paper was to hybridize nanoclay and short kenaf fiber in polylactic acid (PLA) by double extrusion method and followed by mechanical, thermal and morphological characterizations. Mechanical properties showed improvement with nanoclay, specifically the impact strength increased more than 50 % compared with unreinforced PLA. A double extruded composite showed 3–10 % better tensile and flexural properties than the single extruded composite. Similarly, addition of nanoclay increased decomposition and melting temperatures (T _m) from 198 to 225 °C and 152 to 155 °C, respectively. Crystallization temperature (T _c), however, dropped with nanoclay from 116 to 106 °C and storage modulus (E’) increased by about 1 GPa. These findings were also supported by scanning electron micrograph (SEM) and transmission electron micrograph (TEM) where in double extruded composite a better dispersion of nanoclay was observed. By employing X-ray diffraction (XRD) it was found that higher percentage of crystallinity was obtained while Fourier transform infrared (FTIR) displayed new bond formation. The presence of nanoclay enhanced thermal and mechanical properties of the hybrid composite.     

Effect of material properties on residual stress distribution in thermal barrier coatings

Residual stress has a significant influence on the crack nucleation and propagation in thermal barrier coatings (TBC) system. In this work, the residual stress in the air plasma spraying (APS) TBC system during cooling process was numerically studied, and the influence of the material properties of each layer on the residual stress was investigated. The morphologies of the interface were described by a piecewise cosine function, and the amplitude for each segment gradually increases. The elasticity, plasticity and creep of top coat (TC), thermally grown oxide (TGO) layer and bond coat (BC) were considered and the elasticity and creep of the substrate layer were taken into account. The material properties of all layers vary with temperature. The results show that the material properties have complex influence on the residual stress during cooling. The effect of the material properties of TC and BC on the residual stress at the interface is relatively large, and that of TGO and substrate is relatively small. These results provide important insight into the failure mechanism of air plasma spraying thermal barrier coatings, and important guidance for the optimization of thermal barrier coating interfaces.     

Effect of chlorine dioxide gas on physical,thermal, mechanical,and barrier properties of polymeric packaging materials

The effects of gaseous chlorine dioxide (ClO₂) on properties and performance of 10 selected polymeric packaging materials, including polyethylene (PE), biaxially oriented poly(propylene), polystyrene, poly(vinyl chloride), poly(ethylene terephthalate) (PET), poly(lactic acid), nylon, and a multilayer structure of ethylene vinyl acetate (EVA)/ethylene vinyl alcohol (EVOH), were evaluated. Physical, mechanical, barrier, and color properties as well as infrared (IR) spectra were assessed before and after polymer samples were exposed to 3600 ppmV ClO₂ gas at 23°C for 24, 168, and 336 h. The IR spectra of the ClO₂‐treated samples revealed many changes in their chemical characteristics, such as the formation of polar groups in the polyolefin, changes in functional groups, main chain scission degradation, and possible chlorination of several materials. The ClO₂‐treated PE samples showed a decrease in tensile properties compared with the untreated (control) films. Decreases in moisture, oxygen, and/or carbon dioxide barrier properties were observed in the treated PE, PET, and multilayer EVA/EVOH/EVA samples. A significant increase (P < 0.05) in the barrier to O₂ was observed in the ClO₂‐treated nylon, possibly the result of molecular reordering, which was found through an increase in the crystallinity of the material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of process parameters and composition on mechanical,thermal, and morphological properties of polypropylene/sawdust composites

Polypropylene/sawdust composites have been prepared according to a statistical experimental design, with varying sawdust and compatibilizer (maleic anhydride grafted PP) concentrations. To investigate process conditions, composites were first extruded in a twin screw extruder coupled to a Haake torque rheometer, without degassing, and then reextruded in a Werner Pfleiderer twin screw extruder, with two degassing zones. Process conditions were analyzed according to statistical techniques. Effect of the variables on mechanical properties was assessed through flexural modulus, tensile strength, and percent elongation at break and morphology was assessed by scanning electron microscopy. Comparison between the extruded and reextruded compounds indicated the need to reduce moisture, prior to and during processing, as well as the need of effective mixing of the compounds. Sawdust concentration showed to be the variable which affected most all properties assessed. Increase in sawdust concentration resulted in increased composite stiffness. The presence of the compatibilizer caused a slight increase in tensile strength and reduction in percent elongation at break, indicating improved adhesion at the PP/sawdust interface. The reprocessed compounds were also analyzed by differential scanning calorimetry. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies on the mechanical,thermal, morphological and barrier properties of nanocomposites based on poly(vinyl alcohol) and nanocellulose from sugarcane bagasse

Nanocomposites from poly(vinyl alcohol) [PVA] in linear and crosslinked state were synthesized using varying proportions of bagasse extracted nanocellulose. These were characterized by tensile, thermal, X-ray diffraction (XRD), moisture vapor transmission rate (MVTR), and morphological studies. Crosslinked PVA and linear PVA nanocomposite exhibited highest tensile strength at 5 wt.% and 7.5 wt.% of nanocellulose respectively. Thermogravimetric analysis (TGA) studies showed higher thermal stability of nanocomposite made of crosslinked PVA and nanocellulose with respect to linear PVA and nanocellulose. TEM and AFM studies confirm the formation of nanocomposites while the SEM images show the dispersion of nanocellulose particles in them.     

Effect of chemically modified clinoptilolite on the thermal,morphological, and gas separation properties of mixed matrix membranes

Mixed matrix membranes (MMM) based on polysulfone and chemically modified clinoptilolite were prepared. Clinoptilolite enriched with Ca²⁺, K⁺, and Na⁺ by ion exchange at two test temperatures was prepared. Chemical composition was monitored by energy dispersive X‐ray spectroscopy. X‐ray diffraction, thermogravimetric analysis, and N₂ adsorption–desorption isotherms were also performed. Thermal and morphological properties of MMM were evaluated. CH₄/CO₂ gas mixture permeability tests at different upstream pressure were carried out. Type of exchanged cation in modified clinoptilolite affected the CO₂ permeability. An improvement on the CO₂/CH₄ selectivity values in the MMM compared to the polymeric membrane was appreciated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45659.     

Mechanical,thermal, and barrier properties of NBR/organosilicate nanocomposites

Nanocomposites of intercalated and exfoliated organosilicates in acrylonitrile butadiene rubber (NBR) were prepared by a solution‐blending method. The dispersion and intergallery spacings of organosilicates in these nanocomposites were examined by transmission electron microscopy and X‐ray diffraction. Dramatic enhancements in the mechanical and thermal properties of NBR are found by incorporating less than ten parts of organosilicate. In particular, the addition of ten parts of organosilicate provided a more than sixfold increase in tensile strength, a twofold increase in M500, and 168% and 39% enhancements in tear strength and elongation at break compared with pure NBR. The degradation temperature for NBR with ten‐parts' loading of organosilicate was 25°C higher than that of pure NBR. In addition, the relative vapor permeability of the NBR nanocomposites for water and methanol were 85% and 42% lower, respectively, than that of pure NBR. Polym. Eng. Sci. 44:2117–2124, 2004. © 2004 Society of Plastics Engineers.     

Effect of clay amount and reprocessing cycles on thermal,morphological, and mechanical properties of polypropylene/organovermiculite nanocomposites

Nanocomposites of polypropylene (PP) and PP‐grafted‐maleic anhydride (PP‐g‐MA) with and without organophilic vermiculite (OVMT) (5–8%w/w) were evaluated. The nanocomposites and neat PP were submitted to extrusion reprocessing cycles. It was found that the presence of OVMT in PP/PP‐g‐MA was critical for maintaining thermal stability during reprocessing. The exfoliation/intercalation was confirmed, mainly, in the nanocomposite submitted to reprocessing cycles, by X‐ray diffraction. The melt flow index (MFI) values for the 3× and 5× reprocessed PP increased by 40% and 70%, respectively, as compared to the neat PP. The MFI for the 3× and 5× reprocessed PP/PP‐g‐MA/OVMT decreased 26% and 17%, respectively, as compared to the decrease occurred in the 3× and 5× reprocessed PP, indicating that the presence of 5% (w/w) OVMT was sufficient to allow an increase in viscosity. The reprocessed nanocomposites exhibited values for tensile and flexural strengths and Izod impact, in general, greater than or near to those of PP with the same number of reprocessing cycles. The increase or maintenance of mechanical properties seems to depend on a balance between the extent of intercalation/exfoliation and dispersion of OVMT in the PP matrix, and the degree of degradation of the PP matrix. POLYM. ENG. SCI., 59:2110–2120, 2019. © 2019 Society of Plastics Engineers     

Compatibilised LDPE/LLDPE/nanoclay nanocomposites: I. Structural,mechanical, and thermal properties

Nanocomposites of LDPE/LLDPE/nanoclay have been prepared using a lab‐scale co‐rotating twin screw extruder. Using XRD, tensile testing, AFM, TGA, effects of some material properties and one processing parameter on mechanical and thermal properties of the prepared nanocomposites were evaluated. Tensile properties indicated that all the prepared nanocomposites exhibited a significant improvement in elastic modulus and toughness compared to pristine LDPE/LLDPE blends of the same composition. Thermal stability of nanocomposites in the air and nitrogen atmosphere was improved. XRD patterns and AFM micrographs showed semi‐exfoliated and intercalated microstructures for the prepared nanocomposites with different orders of mixing.     

Montmorillonite nanoclay filler effects on electrical conductivity,thermal and mechanical properties of epoxy‐based nanocomposites

Epoxy‐based nanocomposites with 2, 5, and 7 wt% of montmorillonite (MMT) nanoclay were prepared using high shear melt mixing technique. The microstructural features of the nanocomposites were investigated by transmission electron microscopy (TEM). The thermal and mechanical properties were measured using differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). Further, the effect of voltage, temperature, seawater aging on the electrical conductivity (σ_DC) of the nanocomposites was also measured. To understand the free volume behavior upon filler loading, and to observe the connectivity between microstructure and other properties, positron annihilation lifetime spectroscopy was used. The TEM results revealed that MMT nanoparticles were uniformly dispersed in the epoxy matrix. Experimental results showed that the inclusion of 2 wt% MMT nanofiller increased the T_g, electrical conductivity, thermal stability, modulus, free volume of the epoxy nanocomposite significantly. This is well explained from the results of T_g (DSC and DMA), thermal stability, TGA residue, free volume analysis, and electrical conductivity. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers