Zero‐order kinetics of the thermal degradation of polypropylene/clay nanocomposites

The thermal degradation kinetics of polypropylene/clay microcomposites and nanocomposites were studied by thermogravimetric analysis. In comparison with pure polypropylene, the reaction order of the degradation of the composites became zero‐order, and the activation energy increased dramatically. The zero‐order kinetics were associated with the acidic sites (H⁺) created on the clay layers, whereas the increase in the activation energy was coupled with the shielding effect of clay. The kinetic analysis could provide additional mechanistic clues concerning the thermal stability and flammability of polymer/clay nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3713–3719, 2005     

PA66/PA12/clay based nanocomposites: structure and thermal properties

In a previous paper the structure and the physical properties of melt mixed polyamide 66 (PA66)/polyamide 12 (PA12) blends characterized by different compositions have been investigated by means of morphological and physical analyses. A low amount of organically‐modified layered silicate (OMLS, 4 wt%) was introduced in order to evaluate its effect on blends structure and components miscibility. This paper completes the characterization of these materials investigating their thermal properties by means of standard and modulated differential scanning calorimetry (DSC, MDSC), dynamic‐mechanical analysis (DMA), and thermogravimetric analysis (TGA). The partial miscibility of PA66 and PA12, with phase separation depending on blend composition, has been confirmed by analyzing the glass transition temperature (T_g) dependence on composition as well as the existence of strong segmental interactions between polymer components. A compatibilizing action of OMLS has been observed because of a lowering of interfacial tension avoiding coalescence phenomena between particles during melt mixing process. Copyright © 2010 John Wiley & Sons, Ltd.     

Effects of thinner on RTV silicone rubber nanocomposites reinforced with GR and CNTs

The effects of thinner on rubber specimens with carbon nanotubes (CNTs) and graphitic nanofillers (GR) was studied for robotics applications. Rubber specimens were prepared by dispersing GR, CNTs and thinner in room temperature vulcanized (RTV) silicone rubber through solution mixing. Microscopic studies have confirmed occurrence of swelling in polymer chains due to migration of thinner. It results an increase in topological depth from 40 nm (no thinner) to 120 nm (40 phr of thinner). An elastic modulus of ~4.4 MPa (without thinner) was higher than 2.8 MPa (10 phr of thinner). At 100% strain, the lower dissipation losses of 110% (without thinner) and 70% (40 phr of thinner) were obtained. The resistance increases from 4.6 kΩ (without thinner) to 5.7 kΩ (10 phr of thinner). At 0.4‐mm‐thick elastomer slab, an actuation displacement of 0.81 mm (without thinner) was obtained which increased to 1.1 mm (60 phr of thinner). Thus, the thinner can be useful for easier processing, controlled stiffness, minimizing dissipation losses, increasing the actuation displacement and decreasing the cost of the device. Copyright © 2017 John Wiley & Sons, Ltd.     

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.     

Compatibilization level effects on the structure and mechanical properties of rubber‐modified polyamide‐6/clay nanocomposites

Exfoliated polyamide‐6 (PA6)/organically modified montmorillonite clay (OMMT) nanocomposites (PNs) were modified with partially maleinized styrene–ethylene/butadiene–styrene triblock copolymers (SEBS) at three maleinization levels in an attempt to link in these materials high toughness with appropriate small‐strain and fracture tensile properties. OMMT stayed only in the PA6 matrix, and no preferential location in the matrix/rubber interphase was observed. The increased dispersed phase size upon the addition of OMMT was attributed to interactions between maleic anhydride (MA) functionalized SEBS and the surfactant of OMMT. The rubber particle size generally decreased when the MA content of SEBS increased, and this indicated compatibilization. The subsequent good adhesion led to tough nanocomposites across a wide range of both strain rates and fracture modes. As the critical interparticle distance (τ_c) decreased with the MA content, and the other parameters that could influence the surface‐to‐surface mean interparticle distance did not change, it is proposed that in these PNs higher adhesion leads to a smaller τ_c value. Finally, the presence in the matrix of a nanostructured clay makes the rubber content necessary for the toughness jump to increase and τ_c to decrease. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3611–3620, 2005     

Effects of heat and pressure on intercalation structures of isobutylene‐isoprene rubber/clay nanocomposites. I. Prepared by melt blending

In this work, the effects of heat and pressure on intercalated structures of isobutylene‐isoprene rubber/clay nanocomposites (IIRCNs) prepared by melt blending were investigated. Not only the local intercalated structures were monitored by wide‐angle X‐ray diffraction, but also the spatial distributions of intercalated structures were observed by transmission electron microscope. The experimental result reveals that the intercalated structures and their spatial distributions in the matrix are extensively altered by the thermal treatment at atmospheric or higher pressure. The possible microstructural models for untreated and treated IIRCNs were put forward. The observed phenomena were interpreted from the viewpoints of thermodynamics and kinetics theories as well as the feature of rubber. Finally, guidelines were proposed for designing curing system to achieve desired intercalated/exfoliated morphology. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2653–2664, 2005     

RAFT-mediated polystyrene-clay nanocomposites prepared by making use of initiator-bound MMT clay

The initiator 2,2′-azobis(2-(1-(2-hydroxyethyl)-2-imidazolin-2-yl)propane)dihydrochloride monohydrate (VA060) was used to surface-modify sodium montmorillonite clay (Na-MMT). The obtained organically modified clay was then used as a macro-initiator in the preparation of polystyrene-clay nanocomposites by in situ free radical polymerization of styrene in bulk. The polymerization was carried out in the presence of various reversible addition-fragmentation chain transfer (RAFT) agents: 1,4-phenylenebis(methylene)dibenzenecarbodithioate (PCDBDCP), didodecyl-1,4-phenylenebis(methylene)bistrithiocarbonate (DCTBTCD) and 11-(((benzylthio)-carbonothioyl)thio)undecanoic acid (BCTUA). All of the nanocomposites prepared were found to have intercalated morphologies. In the absence of RAFT agents, typical uncontrolled free radical polymerization occurred, giving polystyrenes with high molar masses and high polydispersity indices. In contrast, when the polymerization was conducted in the presence of any of the RAFT agents, the polymerization was found to occur in a controlled manner, as the polystyrene-clay nanocomposites obtained contained polymer chains of narrow polydispersities. The influences of clay loading and molar mass on thermal stability of the polystyrene-clay nanocomposites were investigated. Increases in the clay loading or the molar masses resulted in improvement of the thermal stability of the nanocomposites.     

Characterization and thermal degradation studies on polyaniline‐intercalated montmorillonite nanocomposites prepared by a solvent‐free mechanochemical route

Polyaniline (PANI)‐montmorillonite (MMT) nanocomposites were prepared by direct intercalation of aniline molecules into MMT galleries, followed by in situ polymerization within the nano‐interlamellar spaces under solvent‐free conditions. The basal spacing of aniline‐intercalated MMT increased gradually up to 1.5 nm with increasing amounts of aniline loaded. This result suggests that aniline molecules were adsorbed by MMT clay and that intercalated aniline likely located perpendicular to the silicate sheets. After polymerization, X‐ray diffraction and Fourier transform infrared analyses confirmed the successful synthesis of PANI chains between the MMT nano‐interlayers. The scanning electron microscopy images indicated that the surface morphologies of PANI–MMTs were strongly different depending on the PANI content. The electrical conductivities of PANI nanocomposite particles in pressed pellets ranged in the order of between 10^?3 and 10^?2 S/cm. UV–vis spectroscopy and doping level measurement were further used to discuss the conductivities of nanocomposites. The thermal stabilities of PANI–MMT nanocomposites were examined by using thermogravimetric‐differential thermal analysis and derivative thermogravimetric analysis, and both analyses consequently demonstrated the improved thermal stabilities of the PANI chains in the nanocomposites as compared to pure PANI. The thermal stabilities of resulting nanocomposites were strongly related to the PANI content, which increased as the PANI content decreased in the nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2705–2714, 2005     

Effects of organoclays on the thermal processing of pe/clay nanocomposites

Nanocomposites containing both polyethylene and montmorillonite clay organically modified with four different types of quaternary ammonium salts were obtained via direct melt intercalation. Thus, the main purpose of this work was to evaluate the effect of the organoclay on the thermal stability of polyethylene. The organoclays were characterized by XRD, FTIR, DSC and TG. The polyethylene/organoclay nanocomposites were studied by XRD, TEM, TG, besides an evaluation of their mechanical properties. The results showed that the salts were incorporated by intercalation between the layers of the organoclay and, apparently that the nanocomposites were more thermally stable than pure polyethylene.     

Influence concentration of modifying agent on properties of natural rubber/organoclay nanocomposites

Sodium-montmorillonite (Na-MMT) nanoclay was modified with different concentrations of octadecylamine organic modifying agent at 0.5, 1.0 and 1.5 times the CEC of Na-MMT. Influence of concentration of modifying agent on properties of the organoclays and natural rubber/organoclay nanocomposites was investigated. It was found that the optimum concentration of modifying agent was 1.5 times the CEC of Na-MMT. That is, at this concentration, larger d-spacing of organoclay particles and higher degree of clay dispersion in natural rubber matrix were observed. Larger interlayer d-spacing also caused enhancement of the mechanical properties of the NR/organoclay nanocomposites. Additionally, the NR/organoclay nanocomposites with higher concentration of modifying agent exhibited faster curing reaction with higher crosslink density. Furthermore, the organoclays with larger d-spacing and higher degree of dispersion in the natural rubber matrix exhibited enhancement of the mechanical and dynamic properties and thermal stability of natural rubber/organoclay nanocomposites.     

Structure,thermal stability,and photocrosslinking characterization of HDPE/LDH nanocomposites synthesized by melt‐intercalation

Structure, thermal properties, and influence of layered double hydroxide (LDH) fillers on photocrosslinking behavior of high‐density polyethylene (HDPE)/LDH nanocomposites have been studied in the present article. The X‐ray diffraction and transmission electron microscopy analysis demonstrate that the completely exfoliated HDPE/LDH nanocomposites can be obtained by controlling the organomodified LDH loading via melt‐intercalation. The data from the thermogravimetric analysis show that the HDPE/LDH nanocomposites have much higher thermal stability than HDPE sample. When the 50% weight loss was selected as a comparison point, the decomposition temperature of HDPE/LDH sample with 5 wt % LDH loading is ～40 °C higher than that of HDPE sample. The effects of UV‐irradiation on the HDPE/LDH nanocomposites show that the photoinitiated crosslinking can destroy the completely exfoliated structure to form the partially exfoliated structure, which decreased the thermal stability of the nanocomposites. However, the thermal stability of photocrosslinked samples can increase with increasing the UV‐irradiation time. The effect of LDH loading on the gel content of UV‐irradiated nanocomposites shows that the LDH materials can greatly absorb the UV irradiation and thus decrease the crosslinking efficiency. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3165–3172, 2006     

Preparation and properties of nanocomposites based on acrylonitrile–butadiene rubber,styrene–butadiene rubber,and polybutadiene rubber

Nanocomposites were prepared with different grades of nitrile rubber with acrylonitrile contents of 19, 34, and 50%, with styrene–butadiene rubber (23% styrene content), and with polybutadiene rubber with Na‐montmorillonite clay. The clay was modified with stearyl amine and was characterized by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies showed an increase in the gallery gap upon the modification of the filler by stearyl amine. The intercalation of the amine chains into the clay gallery gap was confirmed by the presence of some extra peaks (2928, 2846, and 1553 cm^?1) in the FTIR spectra. The clay–rubber nanocomposites were characterized by TEM and XRD. The mechanical properties were studied for all the compositions. An improvement in the mechanical properties with the degree of filler loading up to a certain level was observed. The changes in the mechanical properties, with changes in the nature and polarity of the rubbers, were explained with the help of XRD and TEM results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1573–1585, 2004     

Functional copolymer/organo‐MMT nanoarchitectures. III. Dynamic mechanical behavior of poly(IA‐co‐BMA)‐organo‐MMT clay nanocomposites

Functional copolymer/organo‐silicate [N,N′‐dimethyldodecyl ammonium cation surface modified montmorillonite (MMT)] layered nanocomposites have been synthesized by interlamellar complex‐radical copolymerization of pre‐intercalated itaconic acid (IA)/organo‐MMT complex as a “nanoreactor” with n‐butyl methacrylate (BMA) as an internal plasticization comonomer in the presence of radical initiator. Comparative analysis of physical structure, dynamic mechanical analysis parameters, and surface morphology of the obtained copolymers and their nanocomposites indicated that the interlayer H‐bonding and flexible n‐butyl ester linkages take place an important role in interlamellar copolymerization and intercalation/exfoliation of copolymer chains. It was found that nanocomposites' dynamic mechanical properties strongly depended on the force of interfacial H‐bonding and amount of BMA units. An increase in both of these parameters leads to enhanced intercalation and exfoliation in situ processes of copolymer chains and the formation of hybrid nanocomposites. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis of structure–properties relationship in nitrile‐butadiene rubber/phenolic resin/organoclay ternary nanocomposites using simple model system

The present study deals with the structure–property relationship of organoclay (OC) filled nanocomposites based on rubber blend comprising of nitrile‐butadiene rubber (NBR) and phenolic resin (PH). To obtain a better insight into the characteristics of the NBR/PH/OC hybrid system, a simple model system consisting of NBR/OC nanocomposites is also taken into consideration. A series of NBR/OC and NBR/PH/OC nanocomposites containing a wide range of OC concentrations (2.5–30 phr) are prepared by using traditional open two‐roll mill. Structural analysis performed by X‐ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) exhibits mixed exfoliated and intercalated morphology at low OC content, below 7.5 phr, and a well‐ordered intercalated morphology at higher OC loading. It is shown that the dispersion of OC is also influenced by mixing time and order of mixing of components. Analysis of the cure characteristics, mechanical, and thermal properties of both the NBR/OC and NBR/PH/OC nanocomposites reveals that the OC is dispersed mainly in the NBR continuous phase, even though some is likely localized in the rubber–resin interface. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of gamma irradiation on high density polyethylene/ethylene‐vinyl acetate/clay nanocomposites

The study of high density polyethylene (HDPE)/ethylene‐vinyl acetate (EVA)/and organically‐modified montmorillonite (OMT) nanocomposites prepared by melt intercalation followed by exposure to gamma‐rays have been carried out. The morphology and properties of the nanocomposites were studied using X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and cone calorimetry. The purpose of the study focuses on the influence of gamma irradiation on the morphology, thermal stability and flammability properties of the nanocomposites. XRD studies and TEM images verified that the ordered intercalated nanomorphology of the nanocomposites was not disturbed by gamma irradiation. TGA data showed that the nano‐dispersion of clay throughout the polymer inhibited the irradiation degradation of HDPE/EVA blend, which led to the nanocomposites exhibiting superior irradiation‐resistant properties than that of the pure blend. Cone calorimetry results indicated that the improvement in heat release rate (HRR) for irradiated HDPE/EVA blend was suppressed efficiently when clay was present. Increasing clay loading from 2 to 10% was beneficial by improving the flammability properties of the nanocomposites, but promoted a rapid increase in the sub‐peak HRR at high irradiation dose level. Copyright © 2004 John Wiley & Sons, Ltd.     

Polymer blend nanocomposites: effect of mercapto silane modified kaolin clay on the thermal properties of Polypropylene/Polystyrene blend

Nanocomposites based on polypropylene/polystyrene blends were prepared by melt mixing in a Thermo Haake Rheochord mixer. The effect of mercapto silane modified kaolin clay on the properties of nanocomposites has been studied. The characterization of polypropylene/polystyrene/clay nanocomposites was made by dynamic mechanical analysis, scanning electron microscope, and transmission electron microscopic, and the thermal stability was determined by using Thermogravimetric analysis. The activation energy of degradation was determined using three mathematical models, namely Horowitz–Metzger, Coats–Redfern and Broido's methods, and the results were compared. TGA results show an improved thermal stability for nanocomposite than the pure blend. The improvement in thermal stability of nanocomposites was confirmed by increasing the activation energy. Transmission electron microscopic observations showed that nanoclay layers were intercalated on the polymer matrix and were located at the interface between the two polymers Copyright © 2014 John Wiley & Sons, Ltd.     

The influence of multiple modified MMT on the thermal and fire behavior of poly (lactic acid) nanocomposites

This work reported the preparation and physical properties of biodegradable nanocomposites fabricated using polylactic acid (PLA) and multiple organic modified montmorillonite (MMT). In order to improve the chemical compatibility between PLA and Na‐MMT, the surface of Na‐MMT was first organically modified by cetyl trimethyl ammonium bromide (CTAB) and resorcinol bis(diphenyl phosphate) (RDP) using ion‐exchange and adsorption technique. Both Fourier transform infrared and X‐ray diffraction (XRD) results indicated that CTAB and RDP molecules were intercalated into the galleries of MMT sheets to enlarge the interlayer spacing. Then, the PLA/MMT nanocomposites were prepared by a simple melt‐blending method. The XRD and TEM results of the nanocomposites indicated that the PLA polymer chains inserted into the galleries of co‐modified MMT (C‐MMT) and contained disorderedly intercalated layered silicate layers within a PLA matrix. The C‐MMT nanolayers were homogenously dispersed in PLA matrix, resulting in various property enhancement. The fabricated PLA/C‐MMT nanocomposites with 5.0 wt% addition showed significant enhancements (176%) in the storage modulus compared to that of neat PLA. The thermal stability and fire resistance were also remarkably improved. These improvements are probably because of both the physical barrier effect of the MMT nanosheets and charring effect of the C‐MMT. Copyright © 2015 John Wiley & Sons, Ltd.     

Solidlike transition of melt‐intercalated biodegradable polymer/clay nanocomposites

Synthetic biodegradable aliphatic polyester (BAP) intercalated into organoclay was prepared by melt compounding, and its solidlike characteristics were investigated via several rheological test modes: steady shear rotation, oscillation, and creep testing. Structural investigations with X‐ray diffraction and transmission electron spectroscopy were also performed for a better understanding of the characteristic rheological behaviors. The creep, recovery, and stress modulus exhibited a solidlike transition of BAP/clay nanocomposites that depended on the clay content. An increase in the zero shear rate viscosity and a shifting of the crossover point (storage modulus vs loss modulus) to a lower frequency were also observed with increasing clay contents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2052–2061, 2003     

Synthetic preparations,thermal properties and crystallization characterization of PLLA‐PPG block copolymers/clay nanocomposites

In this study, intercalation of the polymer or pre‐polymer from solution was used to blend different proportions of polylactic acid‐propylene glycol (LPG) copolymers (polypropylene glycols (PPG) of : 700, 1000, 2000) and lipophilic montmorillonite (clay) in order to investigate the melting and the crystalline nature of LPG copolymers/clay nanocomposites via a differential scanning calorimeter (DSC). In addition, changes in the intermolecular force and crystal morphology of the nanocomposites under different crystallization conditions were also studied. For the results, it was observed from a thermogravimetric analyzer that increasing the clay content elevated the weight loss temperature. In non‐isothermal experiments using a DSC, it was discovered that the melting temperature and crystallization temperature of the LPG copolymers also increased with increasing amounts of added clay. The crystallinity of LPG2000 + 1.5 wt% clay was enhanced by 17.00%; in addition, it was found in the crystallinity study that adding clay slowed down the crystallization rate of the LPG copolymers. Moreover, it was found via X‐ray diffractometer (XRD) that the intensity of the diffraction peaks of the 1.5 wt% specimen was stronger than that of the 0.5 wt% specimens. The results imply that copolymers with a longer chain length provide greater space for the crystals to grow, thus making it easier for larger crystals to grow. Conversely, the added clay generates an inhibitory effect in copolymers, reducing the d‐spacing (d) in the XRD. Therefore, adding clay would change the crystallization behavior and the morphology of the LPG copolymers. Copyright © 2015 John Wiley & Sons, Ltd.     

Amine‐cured epoxy/clay nanocomposites. II. The effect of the nanoclay aspect ratio

The thermophysical and mechanical properties of a nanocomposite material composed of amine‐cured diglycidyl ether of bisphenol A (DGEBA) reinforced with organomontmorillonite clay are reported. The storage modulus at 100 °C, which was above the glass‐transition temperature (T_g), increased approximately 350% with the addition of 10 wt % (6.0 vol %) of clay. Below the T_g, the storage modulus at 30 °C increased 50% relative to the value of unfilled epoxy. It was determined that the T_g linearly increased as a function of clay volume percent. The tensile modulus of epoxy at room temperature increased approximately 50% with the addition of 10 wt % of clay. The reinforcing effect of the organoclay nanoplatelets is discussed with respect to the Tandon–Weng and Halpin–Tsai models. A pseudoinclusion model is proposed to describe the behavior of randomly oriented, uniformly dispersed platelets in nanocomposite materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4391–4400, 2004