Mechanical, thermal, and moisture absorption properties of nano-clay reinforced nano-cellulose biocomposites

In this research, fully environment-friendly, sustainable and biodegradable ‘green’ composites were fabricated. A novel material comprised of microfibrillated cellulose and laponite clay with different inorganic/organic ratios (m/m) was prepared. The composites were characterized by tensile, bending and water absorption tests as well as dynamic mechanical analysis. The morphologies of these nanocomposites were evaluated through scanning electron microscopy. Results showed considerable improvement of mechanical properties; specifically in elastic modulus, tensile strength and flexural modulus with the addition of nanoclay up to 7.5 wt% nano-clay. The modulus of elasticity increased significantly by about 26 % at 5 wt% nanocaly. The flexural modulus increased by about 90 % at 7.5 wt% nanoclay. However, with an increased load of clay in the nanocomposite, the mechanical properties decreased due to the agglomeration of excessive nanoclay. The storage modulus was significantly increased at high temperature with increasing the load of nanoclay.     

Does nanoclay addition always lead to amelioration? Dual effects of the nanoclay on the PA‐6/EVOH/SEBS ternary blends

This work presents the investigation of properties of polyamide‐6 (PA‐6)/ethylene vinyl alcohol (EVOH)/styrene‐ethylene‐butylene‐styrene (SEBS) ternary blends and related nanocomposites with nanoclays. In this way, the effect of the mixing protocol and nanoclay type on the morphology, mechanical, and rheological properties of the blends was comprehensively studied. Scanning electron microscopy (SEM) observation revealed that, for the neat ternary blends, core‐shell droplets were formed in which SEBS droplets were encapsulated by EVOH phase in the PA‐6 matrix. In this regard, experimental observations were compared and discussed with the predictions of phenomenological models. According to the X‐ray diffraction analysis, the distribution and degree of dispersion of the nanoclays were significantly influenced by mixing protocol. It was demonstrated that competition between the intrinsic effect of the nanoclay on the physical properties and its inhibiting effect on the interactions between PA‐6 and EVOH phases led to some interesting observations for the rheological and mechanical properties of the ternary blends. The results revealed that optimum properties could be obtained by selecting appropriate nanoclay and mixing protocol.     

Morphology and properties of polypropylene/ethylene–octene copolymer/clay nanocomposites with double compatibilizers

The influence of nanoclay on the morphology and properties of the polypropylene (PP)/ethylene–octene block copolymer (EOC) blend with double compatibilizers of maleated PP (PP‐g‐MA) and maleated EOC (EOC‐g‐MA) was investigated and compared with the nanocomposites containing either PP‐g‐MA or EOC‐g‐MA as a compatibilizer. X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy were utilized for morphological characterization in conjunction with dynamic mechanical thermal analysis, mechanical testing, and rheological evaluation of these nanocomposites. The results suggested that in the nanocomposite including both compatibilizers of PP‐g‐MA and EOC‐g‐MA, clay was dispersed as a mixed structure of intercalation and exfoliation in both phases of the polymer blend. Comparing the mechanical properties of the studied nanocomposite with nanocomposites of PP/EOC/PP‐g‐MA/clay and PP/EOC/EOC‐g‐MA/clay also indicated that the nanocomposite containing mixed compatibilizers displayed higher tensile modulus, tensile strength, and complex viscosity because of the better dispersion of clay in both phases. The results also confirmed the increased structural stability and reduced dispersed phase size of PP/EOC/PP‐g‐MA/EOC‐g‐MA blend in the presence of clay that proposed the compatibilization role of clay in this nanocomposite. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluation of Mechanical Properties of Epoxy/Nanoclay/Multi-Walled Carbon Nanotube Nanocomposites using Taguchi Method

This paper reports the improvement of the mechanical properties of epoxy/nanoclay/multi-walled carbon nanotube (MWNT) nanocomposites prepared by the solution casting method for a range of pre-cure temperatures (room temperature, 50, and 70 °C), cure temperature (120, 130, and 140 °C), nanoclay content (0.5, 1.0, 1.5 wt%) and content of MWNT (0.2, 0.6, 1.0 wt%) for three levels. The influence of these parameters on the mechanical properties of epoxy/nanoclay/MWNT has been investigated using Taguchi's experimental design. The output measured responses are the tensile properties (tensile modulus, tensile strength and strain at break), impact strength and fracture toughness. From the Analysis of Mean (ANOM) and Analysis of Variance (ANOVA), MWNT content, pre-cure temperature and cure temperature had the most significant effects for the impact strength with contribution percentages of 38%, 28% and 23% respectively. However, for the fracture toughness and strain at break, the enhancements of properties come from the nanoclay content (59%), MWNT content (18%) and pre-cure temperature (23%). While the improvement in tensile strength was influenced by nanoclay and MWNT content, the cure temperature has a stronger effect on the tensile modulus. In this respect, Taguchi method points to the Taguchi method, in this way, points to the dominant parameters and gives the optimum parameter settings for each mechanical property. Confirmation experiments were performed with the optimum parameter settings and the mechanical properties were measured compared with the predicted results.     

Influence of Nanoclay on the Mechanical Performance of Wild Cane Grass Fiber-Reinforced Polyester Nanocomposites

Natural fiber-reinforced nanocomposites were prepared by incorporating wild cane grass fiber and organically modified montmorillonite (MMT) nanoclay into polyester resin. The composites were formulated up to a maximum volume of fiber of approximately 40% and their mechanical properties were investigated. The mean tensile strength and tensile modulus of nanoclay-filled wild cane grass fiber composites are 6.3% and 18.3% greater than those of wild cane grass fiber composites, respectively, without addition of nanoclay at maximum percentage volume of fiber. The mean flexural strength of nanocomposites at maximum percentage volume of fiber was increased to a maximum of 221 Mpa and flexural modulus to 4.2 Gpa. The mean impact strength of nanoclay-filled wild cane grass fiber composites was increased to 376.7 J/m at maximum percentage volume of fiber. The weight loss of nanoclay-filled wild cane grass fiber/polyester composites was 30% and 22% less than that of composites without nanoclay at maximum percentage volume of fiber. The results indicated that the use of nanoclay showed significant improvement in all the mechanical properties of wild cane grass fiber-reinforced composites.     

Preparation,characterization, thermo‐mechanical,and barrier properties of exfoliated thermoplastic toughened epoxy clay ternary nanocomposites

Ternary nanocomposites are prepared by blending hydroxyl‐terminated poly ether ether ketone having pendant methyl groups (PEEKMOH) with epoxy resin along with Nanolin DK1, followed by curing with 4,4′‐diamino diphenyl sulphone. Differential scanning calorimetry shows a two‐stage cure behavior indicating the catalytic effect of the primary amine and proton, which are generated by the dissociation of organic modifier. Tensile and flexural moduli are increased while tensile strength and glass transition temperature are decreased with increase in clay concentration. Fracture toughness and strain at break are increased by 59 and 62%, respectively, with 1 phr clay loading. Transition electron microscopy and X‐ray diffraction (XRD) analysis reveal exfoliated morphology for the nanocomposites. Scanning electron micrographs show a decrease in both, domain size as well as inter domain distance of the thermoplastic phase with the addition of clay, indicating the occurrence of gelation before phase separation. Analysis of the fracture surface reveals crack path deflection and ductile fracture behavior, confirming that toughness has been improved with the addition of clay and PEEKMOH. Coefficient of thermal expansion (CTE) of the nanocomposites is decreased up to 3 phr clay loading. Oxygen gas permeability is compared with Bharadwaj's and Neilson's models. A marginal improvement in thermal stability is observed with the addition of clay. Copyright © 2009 John Wiley & Sons, Ltd.     

Direct 3D Visualization of the Phase‐Separated Morphology in Chlorinated Polyethylene/Nylon Terpolyamide Based Thermoplastic Elastomers

Blends of chlorinated polyethylene and nylon‐6/‐6,6/‐12 terpolyamide were prepared. The ratio of the two components was systematically varied within the blends. The mechanical behavior of the samples was analyzed with tensile tests and dynamical mechanical analysis showing that, for several ratios, materials with improved mechanical properties typical of thermoplastic elastomers were obtained. In such a mechanical regime, a co‐continuous phase‐separated morphology was clearly evidenced at the microscopic scale by 3D laser scanning confocal fluorescent microscopy (LSCFM). At blend compositions where plastic tensile behavior is observed, LSCFM reveals dispersed spheres of one component in the other.     

Poly(lactic acid)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer/sepiolite nanocomposites: Investigation of thermo‐mechanical and morphological properties

In this study, sepiolite nanoclay is used as reinforcing agent for poly(lactic acid) (PLA)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer (SEBS‐g‐MA) 90/10 (w/w) blend. Effects of sepiolite on thermal behavior, morphology, and thermomechanical properties of PLA/SEBS‐g‐MA blend were investigated. Differential scanning calorimetry results showed 7% improvement in crystallinity at 0.5 wt% of sepiolite. The nanocomposite exhibited approximately 36% increase in the tensile modulus and 17% increase in toughness as compared with the blend matrix at 0.5 and 2.5 wt% of sepiolite respectively. Field emission scanning electron microscopy and transmission electron microscopy images exhibited sepiolite‐induced morphological changes and dispersion of sepiolite in both PLA and SEBS‐g‐MA phases. Dynamic mechanical analysis and wide angle X‐ray diffraction present evidences in support of the reinforcing nature of sepiolite and phase interaction between the filler and the matrix. This study confirms that sepiolite can improve tensile modulus and toughness of PLA/SEBS‐g‐MA blend.     

Nanoclay modified silica phenolic composites: mechanical properties and thermal response under simulated atmospheric re‐entry conditions

Ablative nanocomposites based on nanoclay‐dispersed addition curable propargylated phenolic novolac (ACPR) resin, reinforced with chopped silica fiber, were investigated for their thermal response behavior under simulated heat flux conditions corresponding to typical atmospheric re‐entry conditions. Organically modified nanoclay (Cloisite 30B) was incorporated to different extents (1–10%) in the ACPR resin matrix containing silica fiber to form the composite. The composites displayed optimum mechanical properties at around 3 wt% of nanoclay loading. The resultant composites were evaluated for their ablative characteristics as well as mechanical, thermal and thermo‐physical properties. The reinforcing effect of nanoclay was established and correlated to the composition. The mechanical properties of the composites and its pyrolysed product improved at moderate nanoclay incorporation. Plasma arc jet studies revealed that front wall temperature is lowered by 20°C and that at backwall by 10–13°C for the 3 wt% nanoclay‐incorporated composites due to impedance by nanoclay for the heat conduction. Nanoclay diminished the coefficient of thermal expansion by almost 50% and also reduced the flammability of the composites. The trend in mechanical properties was correlated to the microstructural morphology of the composites. The nanomodification conferred better strength to the pyrolysed composites. Copyright © 2014 John Wiley & Sons, Ltd.     

Glass Fiber Reinforced Polymer-Clay Nanocomposites: Processing,Structure and Hygrothermal Effects on Mechanical Properties

Polymer composites have been the mainstay of high-performance structural materials, but these materials are inherently sensitive to environmental factors such as temperature, exposure to liquids, gases, electrical fields and radiation, which significantly affects their useful life. Addition of layered silicate nanofillers in the polymer matrix has led to improvements in the elastic moduli, strength, heat resistance, decreased gas permeability and flammability. In the present work epoxy modified with Cloisite 30 B̈ nanoclay (at 1, 3 and 5 wt% of resin) and E-glass unidirectional fibers are used to prepare fiber reinforced nanocomposites using hand lay-up method. The nanocomposites have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results show that the interlayer spacing between the clay platelets increased significantly indicating that the polymer is able to intercalate between the clay layers. The mechanical properties are measured by carrying out tensile, hardness and flexural tests and values are compared with those found for fiber reinforced neat epoxy composites. The tests show that an addition of nano-clay up to 3 wt% increases tensile strength and micro-hardness and there is a decrease in values with further clay addition up to 5 wt%. The flexural strength increased significantly with clay loading and the highest value is observed for specimens with 5 wt% of clay. Further, durability studies on nanocomposites have been performed in water and NaOH baths under accelerated hygrothermal conditions. During the exposure it is observed that the degradation in NaOH environment is more severe than in water.     

SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF ORGANOCLAY-MODIFIED POLYSULFONE/EPOXY INTERPENETRATING POLYMER NETWORK NANOCOMPOSITES

Organoclay-modified hydroxylterminated polysulfone (PSF)/epoxy interpenetrating network nanocomposites (oM-PSF/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polysulfone and epoxy resin (PSF/EP) using diaminodiphenylmethane (DDM) as curing agent.The mechanical properties like tensile strength,tensile modulus,flexural strength,flexural modulus and impact properties of the nanocomposites were studied as per ASTM standards.Differ...     

Imidazolium‐modified clay‐based ABS nanocomposites: a comparison between melt‐blending and solution‐sonication processes

Acrylonitrile–butadiene–styrene (ABS) nanocomposites containing imidazolium‐modified montmorillonite have been prepared by melt‐blending (MB) and solution‐sonication in order to study the effects of processing on the morphology and properties of the polymer/clay composites. The structure‐property relationships of the prepared composites have been studied by means of X‐ray diffraction (XRD), transmission electron microscopy (TEM), mechanical testing, dynamic‐mechanical analyses (DMA), thermal gravimetrical analyses (TGA), fluorescence probe confocal microscopy, and fluorescence spectroscopy (FS). X‐Ray and TEM show that both nanocomposites have a mixed intercalated/exfoliated structure. Fluorescence probe confocal microscopy reveals that the sonicated sample has a more homogeneous dispersion: this result is confirmed by the values of elongation at break and flexural elastic modulus measured for the composites. Fluorescence spectroscopy has also been used to investigate the distribution of clay in the composites and results indicate that clay layers in ABS are preferentially located in the styrene‐acrylonitrile (SAN) phase, independent of the dispersion process used. Published in 2008 by John Wiley & Sons, Ltd.     

The addition of clay on the mechanical properties of surface‐treated CF‐filled PA66 composites

Polyamide 66 (PA66) composites filled with clay and carbon fiber (CF) were prepared by twin‐screw extruder in order to study the influence of nanoparticle reinforcing effect on the mechanical behavior of the PA66 composites (CF/PA66). The mechanical property tests of the composites with and without clay were performed, and the fracture surface morphology was analyzed. The results show that the fracture surface area of the clay‐filled CF/PA66 composite was far smoother than that of the CF/PA66 composite, and there formed a tense interface on the CF surface after the addition of clay. The tensile and flexural strength of CF/PA66 composites with clay was improved. The impact strength decreased because of the high interfacial adhesion. In conclusion, the addition of clay favored the improvement of the higher interface strength and so had good effect on improving the tensile and flexural properties of the composites. Copyright © 2017 John Wiley & Sons, Ltd.     

Enhanced mechanical properties of unidirectional basalt fiber/epoxy composites using silane-modified Na+-montmorillonite nanoclay

This study explores the effects of 3-glycidoxypropyltrimethoxysilane (3-GPTS) modified Na-montmorillonite (Na-Mt) nanoclay addition on mechanical response of unidirectional basalt fiber (UD-BF)/epoxy composite laminates under tensile, flexural and compressive loadings. Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and simultaneous thermal analysis (STA) data confirmed the reaction mechanism between the silane compound and Mt. It was demonstrated that addition of 5 wt % 3-GPTS/Mt resulted in 28%, 11% and 35% increase in flexural, tensile and compressive strengths. Scanning electron microscopy (SEM) clarified the improvement in the adhesion between the basalt fibers and matrix in the case of Mt-enhanced epoxy specimens. Also, a theoretical route based on a Euler-Bernoulli beam-based approach was employed to estimate the compressive properties of the composites. The results demonstrated good agreement between theoretical and experimental approaches. Totally, the results of the study show that matrix modification is an effective strategy to improve the mechanical behavior of fibrous composites.     

HMSPP nanocomposite and Brazilian bentonite properties after gamma radiation exposure

This work concerns the study of the mechanical and thermal behavior of the nanocomposite high melt strength polypropylene (HMSPP) (obtained at a dose of 12.5 kGy) and a bentonite clay Brazilian Paraiba (PB), which is known as “chocolate” and is used in concentrations of 5% and 10% by weight, in comparison to the American Cloisite 20A clay nanocomposites. An agent compatibilizer polypropylene-graft (PP-g-AM) was added at a 3% concentration, and the clay was dispersed using the melt intercalation technique using a twin-screw extruder. The specimens were prepared by the injection process. The mechanical behavior was evaluated by strength, flexural strength and impact tests. The thermal behavior was evaluated by the techniques of differential scanning calorimetry (DSC) and thermogravimetry (TGA). The morphology of the nanocomposites was studied with scanning electron microscopy (SEM), while the organophilic bentonite and nanocomposites were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).     

PET/R‐PP/PC blends by two‐stage reactive extrusion: effect of polypropylene reactively functionalized with an oxazoline group on morphology and mechanical properties

A series of PET/R‐PP/PC blends was studied in a chemical modification involving reactive extrusion with a ricinyl‐2‐oxazoline maleinate. The interfacial reaction between blend components were studied by the differential scanning calorimetry (DSC) and the scanning electron microscopy (SEM). The static tensile and flexural properties, and impact resistance response of the blends were tested. The phase morphology of the blends was of interpenetrating network (IPN) type according to SEM results. The blends offer excellent mechanical properties and improved impact strength as an effect of chemical reactions on reactive extrusion, even if PET waste and low PC contents (below 20%) have been used.     

Synthesis and characterization of polyethylene/clay–silica nanocomposites: A montmorillonite/silica‐hybrid‐supported catalyst and in situ polymerization

A novel approach to the preparation of polyethylene (PE) nanocomposites, with montmorillonite/silica hybrid (MT‐Si) supported catalyst, was developed. MT‐Si was prepared by depositing silica nanoparticles between galleries of the MT. A common zirconocene catalyst [bis(cyclopentadienyl)zirconium dichloride/methylaluminoxane] was fixed on the MT‐Si surface by a simple method. After ethylene polymerization, two classes of nanofillers (clay layers and silica nanoparticles) were dispersed concurrently in the PE matrix and PE/clay–silica nanocomposites were obtained. Exfoliation of the clay layers and dispersion of the silica nanoparticles were examined with transmission electron microscopy. Physical properties of the nanocomposites were characterized by tensile tests, dynamic mechanical analysis, and DSC. The nanocomposites with a low nanofiller loading (<10 wt %) exhibited good mechanical properties. The nanocomposite powder produced with the supported catalyst had a granular morphology and a high bulk density, typical of a heterogeneous catalyst system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 941–949, 2004     

Improvements in the oxygen barrier property of polypropylene nanocomposites

A nanocomposite consisting of polypropylene (PP)/nanoclay (montmorillonite) was prepared by means of a melt‐compounding process with the use of a twin‐screw extruder. Because of the complex dispersion of polar and hydrophilic clays that have many cations in the nonpolar and hydrophobic PP, amino‐silane was introduced to modify the surface of the clays. Also, to improve the compatibility of the modified nanoclay with PP, a PP‐graft‐maleic anhydride was used as a compatibilizer. From Fourier transform infrared spectroscopy analysis and the mechanical property test results, it was confirmed that the surface of the nanoclay was properly modified, and it was successfully dispersed in the PP matrix. The composite was investigated by electron microscopy to analyze its morphology and the degree of dispersion of the nanoclay. An analysis of oxygen permeability according to nanoclay content was performed, and it was found that the higher nanoclay content makes the decrease in oxygen permeability. In addition, a shelf‐life test was carried out to determine the relationship between decreased oxygen permeability and food preservation performance. The preservation performance of the food package prepared with the resin made in this study was improved because of the improvement in mechanical properties and oxygen barrier property.     

Bio‐based hyperbranched polyurethane/clay nanocomposites: adhesive,mechanical, and thermal properties

The unison of vegetable oil‐based hyperbranched polymers with nanotechnology can unhook myriad of avant‐garde applications of such materials. Thus Mesua ferrea L. seed oil‐based hyperbranched polyurethane (HBPU)/clay nanocomposites and their performance, with special reference to adhesive strength, are reported for the first time. The nanocomposites of the hyperbranched polyurethane with organically modified nanoclay were obtained by ex situ solution technique and cured by bisphenol‐A‐based epoxy with poly(amido amine) hardener system. The partially exfoliated and well‐distributed structure of nanoclay was confirmed by XRD, SEM, and TEM studies. FTIR spectra indicate the presence of H‐bonding between nanoclay and the polymer matrix. Two times improvement in the adhesive strength and scratch hardness, 10 MPa increments in the tensile strength and 112°C more thermo‐stability have been observed without much affecting the impact resistance, bending, and elongation at break of the nanocomposites compared to the pristine epoxy modified HBPU system. Thus, the resulted nanocomposites are promising materials for different advanced applications including adhesive. Copyright © 2009 John Wiley & Sons, Ltd.     

A study of PP/PET composites: Factorial design,mechanical and thermal properties

Due to the economic importance of polypropylene (PP) and polyethylene terephthalate (PET), and the large amount of composites made with PP matrix and recycled PET as reinforcing material; an investigation was performed regarding the mechanical and thermal behavior of PP composites containing recycled polyethylene terephthalate fibers (rPET). Interfacial adhesion between the two materials was achieved by adding a compatibilizer, maleic anhydride grafted polypropylene, PP-g-MA. Mechanical behavior was assessed by tensile, flexural, impact and fatigue tests, and thermal behavior by HDT (Heat Deflection Temperature). Fractured surfaces and fiber were investigated by scanning electron microscopy. Multiple regression statistical analysis was performed to interpret interaction effects of the variables. Tensile strength, tensile modulus, flexural strength, flexural modulus and HDT increased after rPET fiber incorporation while strain at break, impact strength and fatigue life decreased. Addition of compatibilizer increased tensile strength, flexural strength and flexural modulus, fatigue life and HDT while tensile modulus, strain at break and impact strength decreased. However, at low fiber content, the impact strength increased, probably due to nucleation effects on PP.