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     

Effect of organic modifiers and silicate type on filler dispersion,thermal, and mechanical properties of ABS‐clay nanocomposites

Acrylonitrile–butadiene–styrene (ABS)–clay composite and intercalated nanocomposites were prepared by melt processing, using Na‐montmorillonite (MMT), several chemically different organically modified MMT (OMMT) and Na‐laponite clays. The polymer–clay hybrids were characterized by WAXD, TEM, DSC, TGA, tensile, and impact tests. Intercalated nanocomposites are formed with organoclays, a composite is obtained with unmodified MMT, and the nanocomposite based on synthetic laponite is almost exfoliated. An unintercalated nanocomposite is formed by one of the organically modified clays, with similar overall stack dispersion as compared to the intercalated nanocomposites. T_g of ABS is unaffected by incorporation of the silicate filler in its matrix upto 4 wt % loading for different aspect ratios and organic modifications. A significant improvement in the onset of thermal decomposition (40–44°C at 4 wt % organoclay) is seen. The Young's modulus shows improvement, the elongation‐at‐break shows reduction, and the tensile strength shows improvement. Notched and unnotched impact strength of the intercalated MMT nanocomposites is lower as compared to that of ABS matrix. However, laponite and overexchanged organomontmorillonite clay lead to improvement in ductility. For the MMT clays, the Young's modulus (E) correlates with the intercalation change in organoclay interlayer separation (Δd₀₀₁) as influenced by the chemistry of the modifier. Although ABS‐laponite composites are exfoliated, the intercalated OMMT‐based nanocomposites show greater improvement in modulus. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal and mechanical properties of plasticized poly(L‐lactide) nanocomposites with organo‐modified montmorillonites

Nanocomposites of poly(lactide) (PLA) and the PLA plasticized with diglycerine tetraacetate (PL‐710) and ethylene glycol oligomer containing organo‐modified montmorillonites (ODA‐M and PGS‐M) by the protonated ammonium cations of octadecylamine and poly(ethylene glycol) stearylamine were prepared by melt intercalation method. In the X‐ray diffraction analysis, the PLA/ODA‐M and plasticized PLA/ODA‐M composites showed a clear enlargement of the difference of interlayer spacing between the composite and clay itself, indicating the formation of intercalated nanocomposite. However, a little enlargement of the interlayer spacing was observed for the PLA/PGS‐M and plasticized PLA/PGS‐M composites. From morphological studies using transmission electron microscopy, a finer dispersion of clay was observed for PLA/ODA‐M composite than PLA/PGS‐M composite and all the composites using the plasticized PLA. The PLA and PLA/PL‐710 composites containing ODA‐M showed a higher tensile strength and modulus than the corresponding composites with PGS‐M. The PLA/PL‐710 (10 wt %) composite containing ODA‐M showed considerably higher elongation at break than the pristine plasticized PLA, and had a comparable tensile modulus to pure PLA. The glass transition temperature (T_g) of the composites decreased with increasing plasticizer. The addition of the clays did not cause a significant increase of T_g. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Physical properties of poly(trimethylene terephthalate)/organoclay nanocomposites obtained via melt compounding and in situ polymerization

Two series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (MMT) clay (1,2‐aminododecanoic acid (ADA)–intercalated MMT) were prepared via melt compounding and in situ polymerization methods using dimethyl terephthalate (DMT) and 1,3‐propanediol (PDO). The effect of different methods of preparation and varying organoclay contents (1−5 wt%) on the structural, morphological, thermal, and mechanical properties were investigated. The results of wide‐angle X‐ray diffraction (WAXD) and transmission electron microscope (TEM) suggested the possible existence of intercalation morphology between ADA‐MMT and the PTT matrix obtained from melt compounding, and mostly exfoliation state from in situ polymerization depending on the amount of organoclay. From DSC studies, in melt compounding case, the addition of ADA‐MMT in PTT increases melt‐crystallization (T_cm) peak temperature by 14−15°C irrespective of the clay content. However, the melting temperature (T_m) of pristine PTT remains unchanged with increasing clay content. In the case of in situ polymerization, the T_cm and T_m peaks are shifted towards lower temperature with increasing clay content. Dynamic mechanical thermal analysis (DMTA) studies on melt compounded samples revealed a marginal lowering of glass transition temperature (T_g) irrespective of clay content, and a noticeable decrease in T_g with increasing clay content for in situ polymerized samples. The PTT/ADA‐MMT nanocomposites via melt compounding showed higher initial modulus and yield stress, and lower strain at break compared with in situ polymerization with increasing clay content. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Preparation and properties of montmorillonite‐based polyimide nanocomposites

Montmorillonite (MMT)‐based polyimide (PI) nanocomposites were prepared via two‐stage polymerization of PI using polyamic acid (PAA). The clay was organically modified using various alkylammonium ions to examine the effect of changes in alkyl length on the intercalation spacing of both the treated clays and their hybrids with PAA and PI. The intercalation behavior of clay in the PI matrix and its thermal and mechanical properties were investigated as a function of clay concentration. The d‐spacing of organically modified MMT (O‐MMT) increased with increasing length of the alkylammonium chain. PI/O‐MMT hybrids form exfoliated nanocomposites at clay concentrations below 2 wt%, while they form intercalated nanocomposites together with some exfoliated ones at clay contents exceeding 4 wt%. Young's modulus increased rapidly to a clay loading of 2 wt%, and leveled off with further increases in clay loading. The tensile strength at break increased rapidly up to a clay loading of 1 wt%, and then decreased sharply, while the strain at break showed a monotonic decrease with increasing clay loading from 0 to 8 wt%. The storage modulus, E′, in the temperature range below the glass transition temperature T_g, generally increased with increasing clay content, except at the highest clay content of 8 wt%. Copyright © 2004 Society of Chemical Industry     

High‐temperature‐resistant polyimide/montmorillonite nanocomposite foams by solid blending

A series of high‐temperature‐resistant polyimide/montmorillonite (PI/MMT) nanocomposite foams were prepared by solid blending method. The dispersion of MMT and effects of MMT content on the properties of the PI/MMT nanocomposite foams were investigated. Results indicated that MMT could be exfoliated effectively and dispersed uniformly in the PI matrix by the solid blending method. The introduction of MMT could considerably increase the reduced compressive strength, thermal resistance, and decrease the dielectric constant of the PI/MMT nanocomposite foams. The reduced compressive strength of nanocomposite foams showed a maximum value at the MMT content of 5 wt%, which was 197% higher than that of pure PI foams. It was worth noting that a significant increase in glass‐transition temperature (T _g) could be achieved with the increase of MMT content, and the maximum T _g was as high as 436°C at the MMT content of 7 wt%. This study may provide a useful method to prepare PI/MMT nanocomposite foams with improved properties for targeted high‐temperature applications. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers     

Preparation and characterization of antibacterial chitosan/Ag–montmorillonite with improved dynamic mechanic properties

Chitosan/Ag–montmorillonite (CS/Ag–MMT) nanocomposite was obtained via solution intercalation. The X‐ray diffraction and transmission electron microscopy results indicated the successful formation of intercalated‐and‐exfoliated nanostructures at low Ag–MMT contents and intercalated‐and‐flocculated nanostructures at high Ag–MMT contents. The CS/Ag–MMT nanocomposite with 7 wt% Ag–MMT presented a very high inhibition ratio against Staphylococcus aureus (>70%), and its bacterial inhibition zone diameter was 3.2 mm larger than that of CS, which showed remarkable antibacterial activity. When the Ag–MMT content was 5 wt%, the E′ of CS/Ag–MMT was increased to 3,261 MPa, which was 195% higher than CS and exhibited excellent mechanic property. The DMA test results showed the T_g of CS/Ag–MMT shifted to a higher temperature, suggesting the Ag–MMT interlayer not only interacted quite strongly with the reactive groups of CS but also restricted the motion of CS macromolecules, which was also verified by Fourier transform infrared spectrum measurements. POLYM. COMPOS., 35:1980–1988, 2014. © 2014 Society of Plastics Engineers     

Reinforcing effect and isothermal crystallization kinetics of poly(3‐hydroxybutyrate) nanocomposites blended with organically modified montmorillonite

Organically modified montmorillonite (OMMT) has been incorporated up to 7 wt% in poly(3‐hydroxybutyrate) (PHB) by melt compounding in a twin screw extruder. PHB nanocomposites reinforced with C93A showed significant increase in tensile and flexural modulus and impact strength comparatively. Wide angle X‐ray diffraction showed an increase in overall d‐spacing indicating intercalated structure. The intercalation morphology was further supported by transmission electron microscope images indicating formation of intercalated structure in case of PHB/OMMT and a mixture of Intercalated/exfoliated structure in case of PHB/TMI‐MMT nanocomposites. Thermogravimetric analyses indicate that the thermal stability of PHB/TMI‐MMT nanocomposites is higher among all other nanocomposites under investigation and virgin PHB. Differential scanning calorimetry (DSC) analysis of PHB nanocomposites shows marginal increase in glass transition temperature and decrease in crystallization temperature compared to virgin PHB. The isothermal crystallization kinetics of PHB/C93A nanocomposites was investigated by DSC in the temperature range of 100–120°C and the development of relative crystallinity with the crystallization time was analyzed by Avrami equation. POLYM. COMPOS., 35:999–1012, 2014. © 2013 Society of Plastics Engineers     

Synthesis and characterization of poly(methyl methacrylate)/montmorillonite nanocomposites by in situ bulk polymerization

Poly(methyl methacrylate)/montmorillonite (MMT) nanocomposites were prepared by in situ bulk polymerization. The results showed that the silicone coupling agent affected the structure and properties of hybrid materials. XRD analysis showed that the dispersion of clay in nanocomposites with silicone‐modified organophilic MMT was more ordered than that in nanocomposites with unmodified organophilic MMT. The glass transition temperature (T_g) of the nanocomposites was 6–15°C higher and the thermal decomposition temperature (T_d) was 100–120°C higher than those of pure PMMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2256–2260, 2003     

Preparation and properties of bio‐based epoxy montomorillonite nanocomposites derived from polyglycerol polyglycidyl ether and ε‐polylysine

Glycerol polyglycidyl ether (GPE) and polyglycerol polyglycidyl ether (PGPE) were cured with ε‐poly(L ‐lysine) (PL) using epoxy/amine ratios of 1 : 1 and 2 : 1 to create bio‐based epoxy cross‐linked resins. When PGPE was used as an epoxy resin and the epoxy/amine ratio was 1 : 1, the cured neat resin showed the greatest glass transition temperature (T_g), as measured by differential scanning calorimetry. Next, the mixture of PGPE, PL, and montomorillonite (MMT) at an epoxy/amine ratio of 1 : 1 in water was dried and cured finally at 110°C to create PGPE‐PL/MMT composites. The X‐ray diffraction and transmission electron microscopy measurements revealed that the composites with MMT content 7–15 wt % were exfoliated nanocomposites and the composite with MMT content 20 wt % was an intercalated nanocomposite. The T_g and storage modulus at 50–100°C for the PGPE‐PL/MMT composites measured by DMA increased with increasing MMT content until 15 wt % and decreased at 20 wt %. The tensile strength and modulus of the PGPE‐PL/MMT composites (MMT content 15 wt %: 42 and 5300 MPa) were much greater than those of the cured PGPE‐PL resin (4 and 6 MPa). Aerobic biodegradability of the PGPE‐PL in an aqueous medium was ～ 4% after 90 days, and the PGPE‐PL/MMT nanocomposites with MMT content 7–15 wt % showed lower biodegradability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of polyimide/multi‐walled carbon nanotube nanocomposites

Polyimide/multi‐walled carbon nanotube (PI‐MWNT) nanocomposites were fabricated by an in situ polymerization process. Chemical compatibility between the PI matrix and MWNTs is achieved by pretreatment of the carbon nanotubes in a mixture of sulfuric acid and nitric acid. The dispersion of MWNTs in the PI matrix was found to be enhanced significantly after acid modification. The glass transition (T_g) and decomposition (T_d) temperature of PI‐MWNT nanocomposites were improved as the MWNT content increased from 0.5 to 15 wt%. The storage modulus of the PI/MWNT nanocomposites is nine times higher than that of pristine PI at room temperature. The tensile strength of PI doubles when 7 wt% MWNTs is added. The dielectric constant of the PI‐MWNT nanocomposites increased from 3.5 to 80 (1 kHz) as the MWNT content increased to 15 wt%. The present study demonstrates that enhanced mechanical properties can be obtained through a simple in‐situ polymerization process. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Super-crosslinked ionic liquid-intercalated montmorillonite/epoxy nanocomposites: Cure kinetics,viscoelastic behavior and thermal degradation mechanism

Super-crosslinked epoxy nanocomposites containing N-octadecyl-N′-octadecyl imidazolium iodide (IM)-functionalized montmorillonite (MMT-IM) nanoplatelets were developed and examined for cure kinetics, viscoelastic behavior and thermal degradation kinetics. The structure and morphology of MMT-IM were characterized by FTIR, XRD, TEM, and TGA. Synthesized MMT-IM revealed synergistic effects on the network formation, the glass transition temperature (T_g) and thermal stability of epoxy. Cure and viscoelastic behaviors of epoxy nanocomposites containing 0.1 wt% MMT and MMT-IM were compared based on DSC and DMA, respectively. Activation energy profile as a function of the extent of cure was obtained. DMA results indicated a strong interface between imidazole groups of MMT-IM and epoxy, which caused a significant improvement in storage modulus and the T_g of epoxy. Network degradation kinetics of epoxy containing 0.5, 2.0, and 5.0 wt% MMT and MMT-IM were compared by using Friedman, Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and the modified Coats-Redfern methods. Although addition of MMT to epoxy was detrimental to the T_g value, as featured by a fall from 94.1°C to 89.7°C detected by DMA method, and from 103.3°C to 97.9°C by DSC method, respectively. By contrast, meaningful increase in such values were observed in the same order from 94.1°C to 94.7°C and from 103.3°C to 104.7°C for super-crosslinked epoxy/MMT-IM systems.     

Preparation and dynamic mechanical properties of poly(styrene‐b‐butadiene)‐modified clay nanocomposites

Polybutyl acrylate (PBA) was intercalated into clay by the method of multistep exchange reactions and diffusion polymerization. The clay interlayer surface is modified, and obtaining the modified clay. The structures of the clay‐PBA, clay‐GA (glutamic acid), and the clay‐DMSO (dimethyl sulfoxide) were characterized using X‐ray diffraction (XRD). The new hybrid nanocomposite thermoplastic elastomers were prepared by the clay‐PBA with poly(styrene‐b‐butadiene) block copolymer (SBS) through direct melt intercalation. The dynamic mechanical analysis (DMA) curves of the SBS/modified clay nanocomposites show that partial polystyrene segments of the SBS have intercalated into the modified clay interlayer and exhibited a new glass transition at about 157°C (T_g3). The glass transition temperature of polybutadiene segments (T_g1) and polystyrene segments out of the modified clay interlayer (T_g2) are about ?76 and 94°C, respectively, comparied with about ?79 and 100°C of the neat SBS, and they are basically unchanged. The T_g2 intensity of the SBS‐modified clay decreases with increasing the amounts of the modified clay, and the T_g3 intensity of the SBS‐modified clay decreases with increasing the amounts of the modified clay up to about 8.0 wt %. When the contents of the modified clay are less than about 8.0 wt %, the SBS‐modified clay nanocomposites are homogeneous and transparent. The T_gb and T_gs of the SBS‐clay (mass ratio = 98.0/2.0) are ?78.39 and 98.29°C, respectively. This result shows that the unmodified clay does not essentially affect the T_gb and T_gs of the SBS, and no interactions occur between the SBS and the unmodified clay. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1499–1503, 2002; DOI 10.1002/app.10353     

Effect of polymer matrix/montmorillonite compatibility on morphology and melt rheology of polypropylene nanocomposites

In this study, Ca²⁺‐montmorillonite (Ca²⁺‐MMT) and organo‐montmorillonite (OMMT) were modified by three compatibilizers with different degrees of polarity [poly(ethylene glycol) (PEG), alkyl‐PEG, and polypropylene (PP)‐g‐PEG]. PP/MMT nanocomposites were prepared by melt blending and characterized using X‐ray diffraction and transmission electron microscopy. The results showed the degree of dispersion of OMMT in the PP/PP‐g‐PEG/OMMT (PMOM) nanocomposite was considerably higher than those in the PP/PEG/OMMT and PP/alkyl‐PEG/OMMT nanocomposites, which indicated that the dispersion was relative to the compatibility between modified OMMT and PP matrix. Linear viscoelasticity of PP/MMT nanocomposites in melt states was investigated by small amplitude dynamic rheology measurements. With the addition of the modified MMT, the shear viscosities and storage modulus of all the PP/MMT nanocomposites decreased. It can be attributed to the plasticization effect of PEG segments in the three modifiers. This rheological behavior was different from most surfactant modified MMT nanocomposites which typically showed an increase in dynamic modulus and viscosity relative to the polymer matrix. The unusual rheological observations were explained in terms of the compatibility between the polymer matrix and MMT. In addition, the mechanical properties of PP/MMT nanocomposites were improved. A simultaneous increase in the tensile strength and toughness was observed in PP/PMOM nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphology and thermal/mechanical properties of alkyl‐imidazolium‐treated rectorite/epoxy nanocomposites

A novel organic rectorite (OREC) was prepared by treating the natural sodium‐rectorite (Na‐REC) with ionic liquid 1‐hexadecyl‐3‐methylimidazolium bromide ([C₁₆mim]Br). X‐ray diffraction (XRD) analysis showed that the interlayer spacing of the OREC was expanded from 2.23nm to 3.14nm. Furthermore, two types of OREC/epoxy nanocomposites were prepared by using epoxy resin (EP) as matrix, 2‐ethyl‐4‐methylimidazole (2‐E‐4‐MI) and tung oil anhydride (TOA) as curing agents, respectively. XRD and transmission electron microscope (TEM) analysis showed that the intercalated nanocomposite was obtained with addition of the curing agent 2‐E‐4‐MI, and the exfoliated nanocomposite was obtained with addition of the curing agent TOA when the OREC content was less than 2 wt %. For the exfoliated nanocomposite, the mechanical and thermal property tests indicated that it had the highest improvement when OREC content was 2 wt% in EP. Compared to pure EP, 60.3% improvement in tensile strength, 26.7% improvement in bending strength, 34% improvement in bending modulus, 14°C improvement in thermal decomposition temperature (T_d) and 5.7°C improvement in glass transition temperature (T_g) were achieved. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of clay and predispersion method on the structure and properties of polystyrene (PS)‐clay nanocomposites

To prepare the polystyrene (PS)‐clay nanocomposites via an in situ emulsion polymerization, a clay predispersion method, i.e. dispersing the organic clay in the emulsifier solution by the assistance of ultrasonic, was proposed in this study. The conventional method, predispersing the organic clay into the monomer, was also presented for the comparison. The morphology analysis based on the X‐ray Deflection (XRD) and Transmission Electronic Microscopy (TEM) results suggested that the more uniform clay dispersion in the final nanocomposites could be achieved through the new method. The inorganic clay (Na‐MMT) and two organic clays (C₁₈‐MMT and VC₁₈‐MMT) synthesized by exchanging inorganic cations with the trimethyloctadecyl ammonium chloride (OTAC) and the vinylbenzyldimethyloctadecyl ammoniun chloride (VOAC) were chosen to investigate the influence of the clay surface modification on the properties of nanocomposites. The Dynamic Mechanical Analysis (DMA) results showed the storage modulus G′s of the nanocomposites had different enhancements over that of the pure PS, especially when the temperature approached the glass transition temperature (T_g). The T_gs of the nanocomposites, however, varied with the microstructure and the interactions between the polymer and the clay layers. The Na‐MMT and VC₁₈‐MMT increased the T_g, while the T_gs of PS/C₁₈‐MMT nanocomposites were slightly lower than that of the pure PS. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Tapioca starch‐poly(lactic acid)‐Cloisite 30B nanocomposite foams

Tapioca starch (TS), poly(lactic acid) (PLA), and Cloisite 30B nanocomposite foams, with four clay contents of 1, 3, 5, 7 wt%, were prepared by a melt‐intercalation method. Selected structural, thermal, physical, and mechanical properties were characterized using X‐ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine, respectively. XRD results indicated that intercalation of TS/PLA into the nanoclay layers occurred in all four nanocomposite foams. At the same time, tactoid structures were observed in all nanocomposite foams but to a lesser extend with 1 and 3 wt% clay contents. Effect of clay content on melting temperature (T_m), onset degradation temperature, radial expansion ratio, unit density, bulk compressibility and bulk spring index of the nanocomposites were investigated. Among the four nanocomposites, 3 wt% clay content produced significantly different (p < 0.05) properties. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Improved mechanical properties of poly(ethylene terephthalate) nanocomposite fibers

Improvements in Young's modulus and strength (tenacity) of poly(ethylene terephthalate) (PET) fibers were obtained by drawing unoriented nanocomposite filaments containing low concentrations (<3 wt%) of various organically modified montmorillonites (MMTs) in a second step at temperatures above the glass transition. Prior to melt spinning, solid‐state polymerization was used to rebuild lost molecular weight, due to MMT‐induced degradation, to a level suitable for producing high strength fibers. Greater improvements in mechanical properties occurred when the MMT stacks were intercalated with PET. A nominal 1 wt% loading of dimethyl‐dehydrogenated tallow quaternary ammonium surface modified MMT in drawn PET fiber showed a 28% and 63% increase in Young's modulus and strength, respectively. Relative to an unfilled PET fiber, these results surpassed the upper bound of the rule of mixtures estimate and suggested that both the type of surface modification and concentration of MMT affect the degree of PET orientation and crystallinity. Furthermore, drawability above T_g and elongation at break increased upon the addition of organically modified MMT to unoriented PET fibers, which was a key distinction of this work from others examining similar systems. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

A study of the effect of surfactants on the properties of polystyrene‐montmorillonite nanocomposites

Polystyrene‐Organo Montmorillonite (PS‐MMT) nanocomposites were prepared by suspension free radical polymerization of styrene in the dispersed organophilic montmorillonite. The results of X‐ray diffraction (XRD) and Transmission Electron Microscopy (TEM) indicated that exfoliated nanocomposites were achieved. The effect of organic modifiers (surfactants) on the properties of the synthesized nanocomposites was studied. It is found that polystyrene‐MMT nanocomposite with 5.0 wt% of organo‐MMT gave the greatest improvement in thermal stability, and polystyrene‐MMT nanocomposites with 7.5 wt% of organo‐MMT showed the greatest improvement in mechanical properties, compared with that of pure polystyrene (PS) in our experimental conditions. The alkyl chain length of surfactant used in fabricating organo‐MMT affects the synthesized PS nanocomposites: the longer the alkyl chain length that the surfactant possesses, the higher the glass transition temperature of the PS nanocomposite, However, the organoclay in the nanocomposites seems to play a dual role: (a) as nanofiller leading to the increase of storage modulus and (b) as plasticizer leading to the decrease of storage modulus. This results in a lower storage modulus of PS‐TMOMMT and PS‐TMTMMT nanocomposites than that of PS‐TMDMMT and PS‐TMCMMT nanocomposites. Further study is needed to confirm the above hypothesis.     

Barium titanate‐based nanodielectrics of two chemically recyclable thermosets

In this work was investigated the effect of the addition of barium titanate (BaTiO₃) on electrical properties of two chemically recyclable thermosets, polyhemiaminal (PHA) and polyhexahydro‐s‐triazine (PHT), both fabricated from 4,4′‐oxydianiline (ODA), an ether derivative of aniline and paraformaldehyde. Thermal and mechanical properties as well as chemical recyclability of the two polymers and their nanocomposites/nanodielectrics were also investigated. In addition, a quantitative analysis was conducted of the nanoparticle dispersion in the PHA‐/PHT‐based BaTiO₃‐containing nanocomposites using transmission electron microscopy imaging and the nearest‐neighbor distance index and this index was used to analyze the investigated properties in connection with the proper mechanisms. Regarding the electrical properties for both neat polymers, conductivity values of the order of 10^?8 S m^?1 at 100 Hz were observed and dielectric constant values close to 2.80 for both polymers at 1 kHz. The addition of 0.5 wt% of BaTiO₃ ferroelectric nanoparticles increased by about 44% the dielectric constant (1 kHz) and conductivity (10² Hz) of the PHA‐based nanocomposite. PHA and PHT exhibited glass transition temperature (T_g) values in the range 125–180 °C. An increase of 7 °C in T_g was observed after the incorporation of 0.5 wt% of BaTiO₃ into PHA. Concerning the mechanical properties, values in the range 4.00–4.45 GPa for reduced modulus and 0.30–0.43 GPa for nanohardness for PHA and PHT polymers were observed. Independently of filler content or polymer matrix, both mechanical properties were enhanced after the addition of BaTiO₃. The chemical recycling of PHA/PHT and all nanocomposites in the initial ODA reagent after sulfuric acid treatment was successfully characterized using the NMR and Fourier transform infrared spectroscopic techniques. © 2018 Society of Chemical Industry