Structure,thermal conductivity,and thermal stability of bromobutyl rubber nanocomposites with ionic liquid modified graphene oxide

In this report, we demonstrate that both the thermal stability and the thermal conductivity of bromobutyl rubber (BIIR) nanocomposites could be improved by incorporating the ionic liquids (ILs) modified graphene oxide (GO-ILs) using a solution compounding method. The structure, thermal stability and thermal conductivity of this newly modified BIIR nanocomposites were systematically analyzed and studied. The X-ray diffraction (XRD) analysis of GO-ILs showed that ILs had been effectively intercalated into the interlayer of GO, which was found to be able to raise the exfoliation degree of GO. The increased exfoliation degree facilitated a good dispersion of GO-ILs in the BIIR matrix, as revealed by the scanning electron microscope (SEM) images. The glass transition temperatures (T_g) of the GO-ILs/BIIR nanocomposites were also raised by the addition of GO-ILs, which indicates the strong interfacial adhesion between GO-ILs and the rubber. Most importantly, the incorporation of GO-ILs in the BIIR matrix could effectively improve the thermal stability of the rubber nanocomposites according to our thermogravimetric analysis (TGA). The activation energy (E_a) of thermal decomposition of GO-ILs/BIIR nanocomposites increases with the addition of GO-ILs. Besides, the thermal conductivity of GO-ILs/BIIR nanocomposite with 4 wt% of GO-ILs had 1.3-fold improvement compared to that of unfilled BIIR.     

Preparation of Al(OH)3/PMMA nanocomposites by emulsion polymerization

Al(OH)₃/PMMA nanocomposites were prepared by the emulsion polymerization of methyl methacrylate (MMA) in the presence of surface‐functionalized Al(OH)₃ particles. Nanosized Al(OH)₃ particles were previously functionalized with a silane coupling agent, 3‐(trimethoxysilyl) propyl methacrylate (γ‐MPS), which was confirmed by FT‐IR and XRF analysis. The average size of seed particles was around 70 nm, and the density of the coupling agent on the particles was calculated to be 8.9 µmol m^?2. The emulsion polymerization was attempted at relatively high solid content of 40–46 wt%. The ratio of the seed particles to MMA had a strong influence on the stability of latex as well as the morphology of composites. Nanocomposites where several PMMA nodules were attached on the surface of Al(OH)₃ core were produced with stable latex emulsion when the weight percents of Al(OH)₃ to MMA were below 20. In the case of higher ratio of 30%, however, the latexes became unstable with an aggregation, and the product morphology was in the shape of large composite. Thermogravimetric analysis showed an improved thermal stability of PMMA composites with the incorporation of Al(OH)₃ nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd.     

Investigation of structural,rheological and thermal properties of PMMA/ONi-Al LDH nanocomposites synthesized <Emphasis Type="Italic">via</Emphasis> solvent blending method: Effect of LDH loading

This article addresses the synthesis of organically tailored Ni-Al layered double hydroxide (ONi-Al LDH) and its use in the fabrication of exfoliated poly(methyl methacrylate) (PMMA) nanocomposites. The pristine Ni-Al LDH was initially synthesized by co-precipitation method and subsequently modified using sodium dodecyl sulfate to obtain ONi-Al LDH. Nanocomposites of PMMA containing various amounts of modified Ni-Al LDH (3 wt%-7 wt%) were synthesized via solvent blending method to investigate the influence of LDH content on the properties of PMMA matrix. Several characterization methods such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), rheological analysis, differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA), were employed to examine the structural, viscoelastic and thermal properties of PMMA/OLDH nanocomposites. The results of XRD and TEM examination confirm the formation of partially exfoliated PMMA/OLDH nanocomposites. The FTIR results elucidate that the characteristic bands for both pure PMMA and modified LDH are present in the spectra of PMMA/OLDH nanocomposites. Rheological analyses were carried out to examine the adhesion between polymer matrix and fillers present in the nanocomposite sample. The TGA data indicate that the PMMA nanocomposites exhibit higher thermal stability when compared to pure PMMA. The thermal decomposition temperature of PMMA/OLDH nanocomposites increases by 28 K compared to that of pure PMMA at 15% weight loss as a point of reference. In comparison with pure PMMA, the PMMA nanocomposite containing 7 wt% LDH demonstrates improved glass transition temperature (T _g) of around 3 K. The activation energy (E _a), reaction orders (n) and reaction mechanism of thermal degradation of PMMA/OLDH nanocomposites were evaluated using different kinetic models. Water uptake capacity of the PMMA/OLDH nanocomposites is less than that of the pure PMMA.     

Structure and thermal stability of PMMA/MMT nanocomposites as denture base material

Poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were prepared by in situ suspension polymerization. MMT was previously organically modified by three different intercalating agents: methacrylatoethyl trimethyl ammonium chloride (DMC), dodecylamine (12CNH), and hexadecyl allyl ammonium chloride (HADC). The structures of the nanocomposites were investigated by X-ray diffraction and transmission electron microscopy, while the interaction between PMMA and MMT was characterized by Fourier transform infrared spectroscopy. The molecular mass of the extracted PMMA was measured by gel permeation chromatography. The thermal stability of PMMA/MMT nanocomposites was evaluated by thermogravimetric and differential scanning calorimetry. The results indicated that PMMA/MMT nanocomposites were successfully prepared and the interaction between PMMA and MMT of PMMA/MMT–HADC nanocomposites was the strongest. The thermal stability of the nanocomposites was improved and found to be optimal for PMMA/MMT–HADC with T ₁₀ increasing to 304 °C, 52 °C higher than that of neat PMMA.     

Synthesis,characterization, and thermal stability of poly (lactic acid)/zinc oxide pillared organic saponite nanocomposites via ring‐opening polymerization of d,l‐lactide

Poly (lactic acid) (PLA) was synthesized using d , l ‐lactide monomer and zinc oxide (ZnO) pillared organic saponite as the green catalyst, through ring‐opening polymerization. The effects of stoichiometry of catalyst and polymerization conditions on molecular weight of PLA were evaluated by orthogonal experiment. The optimum polymerization parameters were: 0.5 wt% ZnO pillared organic saponite and reaction conditions of 170°C for 20 hr. Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy confirmed the PLA structure. Gel permeation chromatography showed that the average molecular weight of PLA was 48,442 g/mol, and its polydispersity index was 1.875. Differential scanning calorimetry, X‐ray diffraction, and polarized optical microscopy showed that ZnO pillared organic saponite improved the crystallinity of PLA. Thermal gravimetric analysis showed improved thermal stability of PLA because of ZnO pillared organic saponite. Thermal decomposition kinetics of PLA/ZnO pillared organic saponite nanocomposites was also studied. The activation energies (E_a) for thermal degradation of PLA and PLA/ZnO pillared organic saponite nanocomposites were evaluated by the Kissinger and Ozawa methods, which demonstrated that ZnO pillared organic saponite enhanced E_a of thermal degradation of PLA and significantly improved its thermal stability. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermal properties of single walled carbon nanotubes composites of polyamide 6/poly(methyl methacrylate) blend system

The nanocomposites of polyamide 6 (PA6)/poly(methyl methacrylate) (PMMA)/non-functionalized and functionalized [carboxylic acid (COOH) and hydroxyl (OH)] single wall carbon nanotubes (SWCNTs) were prepared in mass ratios of 79.5/19.5/1, 49.5/49.5/1, and 19.5/79.5/1 by melt–mixing method at 230 °C. The PA6/PMMA blends with mass ratios of 80/20, 50/50, and 20/80 served as references. The Fourier transform infrared analyses of nanocomposites showed the formation of hydrogen bond interactions among PA6, PMMA, and OH and COOH functional groups of SWCNTs. The nanocomposites and blends had higher thermal stability with respect to the PMMA. The differential scanning calorimeter (DSC) curves showed that the nanocomposites and blends exhibited two T _g values at around 51 and 126 °C for PA6 and PMMA, respectively. About 20 °C early crystallization was observed in nanocomposites compared to the blends. The dynamic mechanical analysis (DMA) results suggested that among all the compositions of blends and nanocomposites, storage modulus (E′) was higher for PMMA-rich blends and nanocomposites. At 25 °C, the E′ values were higher for blends and nanocomposites compared to the neat PA6. The tan δ curves indicated that the more heterogeneity of the hybrid nature resulted in PA6/PMMA/SWCNTs-OH or SWCNTs-COOH with 79.5/19.5/1 mass ratio nanocomposites compared to the PA6/PMMA with 80/20 mass ratio blend. The higher T _g values of PA6 and PMMA were observed in DMA studies compared to the DSC studies for PA6 and PMMA as neat and in blends and nanocomposites. The significant improvements in crystallization of nanocomposites were considered resulting from achieving better compatibility among the polymer components and carbon nanotubes.     

In situ Synthesis of Poly(methyl methacrylate)/Graphene Oxide Nanocomposites Using Thermal-initiated and Graphene Oxide-initiated Polymerization

A facile and cost-effective method to prepare poly(methyl methacrylate) (PMMA)/graphene oxide (GO) nanocomposites was developed by in situ polymerization. By using thermal-initiated and GO-initiated polymerization of methyl methacrylate (MMA), no extra radical initiator was added during the reaction. Without any pre-functionalization of GO, PMMA chains were covalently bonded to its surface, which was confirmed by Fourier-transform infrared, atomic force microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy investigations. TGA analysis showed that the mass ratio of grafted PMMA and GO was as high as 1.7. Transmission electron microscopy and X-ray powder diffraction investigations demonstrated that the grafting of PMMA chains to GO surfaces resulted in homogeneous dispersion of GO sheets in PMMA matrix, which led to a commendable performance on its mechanical and thermal properties. Dynamic mechanical analysis showed that, at a loading level of just 0.5 wt% for the nanocomposites, the storage modulus of the nanocomposites was improved 14%, and the glass transition temperature was increased 12°C in comparison with that of neat PMMA. Thermogravimetric analysis showed that the onset degradation temperature of the nanocomposites was increased 13°C with a GO content of 0.25 wt%.     

Preparation of nano poly(phenylsilsesquioxane) spheres and the influence of nano-PPSQ on the thermal stability of poly(methyl methacrylate)

The nano poly(phenylsilsesquioxane) spheres (nano-PPSQ) were prepared by the sol?Cgel method and incorporated into poly(methyl methacrylate) (PMMA) by in situ bulk polymerization of methyl methacrylate. The structure of nano-PPSQ was confirmed by transmission electron microscope and thermogravimetry analysis (TG). The interaction between nano-PPSQ and PMMA was investigated by Fourier transform infrared spectra (FT-IR). The influence of nano-PPSQ on the thermal stability of PMMA was investigated by TG and differential scanning calorimetry (DSC) measurements. The results indicated that nano-PPSQ enhanced the thermal stability and the temperatures of glass transition (T _g) of nanocomposites. The effect of the heating rate in dynamic measurements (5?C30?°C?min^?1) on kinetic parameters such as activation energy by TG both in nitrogen and air was investigated. The Kissinger method was used to determine the apparent activation energy for the degradation of pure PMMA and nanocomposites. The kinetic results showed that the apparent activation energy for degradation of nanocomposites was higher than that of pure PMMA under air.     

Preparation and characterization of poly(methyl methacrylate)/titanium oxide composite particles

Before polymerization, the introduction of double bonds onto the surface of the TiO₂ particles was achieved by the treatment of the TiO₂ particles with the silane-coupling agent. Via in-situ emulsion polymerization, the poly(methyl methacrylate) (PMMA)/titanium oxide (TiO₂) composite particles were prepared by graft polymerization of MMA from the surface of the modified TiO₂ particles. The structure of the obtained PMMA/TiO₂ composite particles was characterized using fourier transform infrared spectra (FT-IR), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC) and size excluding chromatography (SEC). The morphology of the obtained PMMA/TiO₂ composite particles was observed by transmission electron microscope (TEM). The results of FT-IR and TGA measurements show that PMMA is successfully grafted from the surface of the TiO₂ particles and that the percentage of grafting and the grafting efficiency can reach 208.3% and 96.6%, respectively. At the same time, the TGA and DSC measurements indicate an enhancement of thermal stability. TEM images demonstrate a better dispersion of the TiO₂ particles in the composite latex. In addition, UV-visible absorption measurements show that the PMMA/TiO₂ composite particles can absorb over 95% UV light at 210–400 nm wavelength.     

A kinetic study of the thermal and thermal oxidative degradations of new bridged POSS/PS nanocomposites

The thermal degradation of a series of three novel bridged polyhedral oligomeric silsesquioxanes (POSS)/polystyrene (PS) nanocomposites, at different POSS content (3%, 5% and 10%), was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres, in order to investigate the effects of this new dumbbell-shaped structure on the filler–polymer interaction and then on the thermal stability of the obtained materials. Nanocomposites were synthesized by in situ polymerization of styrene in the presence of POSS which has not polymerizable groups, aiming to obtain well dispersed POSS/PS systems. The actual filler concentration in the obtained nanocomposites was checked by ¹H NMR spectroscopy. Scanning electron microscopy (SEM) and FTIR spectroscopy evidenced the presence of filler–polymer interactions. Degradations were carried out into a thermobalance, in the scanning mode, at various heating rates, and the characteristic parameters of thermal stability, namely temperature at 5% mass loss (T₅%) and the activation energy (E_a) of degradation, of the various nanocomposites were determined. The results were discussed and interpreted.     

Study on CaCO3/PMMA nanocomposite microspheres by soapless emulsion polymerization

A soapless emulsion polymerization method was applied to synthesize CaCO₃/PMMA spherical composite with different loading of CaCO₃. CaCO₃ nanoparticles were pretreated with oleic acid after the carbonation process of Ca(OH)₂ slurry by CO₂, in order to improve the compatibility between the CaCO₃ particles and MMA monomer in emulsion system. The results of photon correlation spectroscopy (PCS) showed the particles size of composites were bigger than the pure PMMA. And the size increased with the increase of the content of CaCO₃ nanoparticles. TEM images showed that the morphology of the composite microspheres was uniform and CaCO₃ nanoparticles can be well encapsulated in the polymeric microsphere, and were located at the edge of the spheres. The results of DTG and TG indicated that the CaCO₃ nanoparticles could improve the thermal stability of PMMA. Moreover, capsulation of CaCO₃ by PMMA can increase the acid-resistant of CaCO₃ nanofillers.     

Synthesis and kinetic studies of PMMA nanoparticles by non-conventionally initiated emulsion polymerization

The aqueous emulsifier-free emulsion polymerization of methyl methacrylate (MMA) was studied under the catalytic effect of in situ developed bivalent transition metal-EDTA complex with ammonium persulfate (APS, (NH₄)₂S₂O₈) as initiator. Out of these, Cu(II)-EDTA system was selected for detailed kinetic and spectrometric study of polymerization. The apparent activation energy E_a, 34.5 kJ/mol, activation energy of initiator decomposition E_d, 26.9 kJ/mol, energy of propagation E_p, 29 kJ/mol and energy of termination E_t, 16 kJ/mol were reported. The emulsion polymer (PMMA) latex was characterized through the determination of the size and morphology by scanning electron microscopy, the average molecular weight by GPC and viscosity methods and the sound velocity by ultrasonic interferometer. From the kinetic results, the rate of polymerization, R_p at 50 °C was expressed by

     

Influence of surface modified TiO2 nanoparticles by gallates on the properties of PMMA/TiO2 nanocomposites

Nanocomposites based on poly(methyl methacrylate) (PMMA) and TiO₂ nanoparticles were synthesized by in situ radical polymerization of MMA in solution. The surface of TiO₂ nanoparticles was modified with four gallic acid esters (octyl, decyl, lauryl and cetyl gallate). The content of gallates present on the surface of TiO₂ was calculated from the TGA results. The influence of length of hydrophobic tail of amphiphilic alkyl gallates on dispersability of surface modified TiO₂ nanoparticles in PMMA matrix, the molecular weight and glass transition temperature of PMMA, as well as the thermal stability of the prepared PMMA/TiO₂ nanocomposites in nitrogen and air was investigated. The influence of content of TiO₂ nanoparticles on the properties of these nanocomposites was also examined. The formation of a charge transfer complex between the surface Ti atoms and the gallates was confirmed by FTIR and UV spectroscopy. TEM micrographs of the PMMA/TiO₂ nanocomposites revealed that degree of TiO₂ aggregation can be significantly lowered by increasing the length of aliphatic part of the used gallates. The molecular weight of PMMA slightly decreases with the increase of TiO₂ content, indicating that used TiO₂ nanoparticles act as radical scavengers during the polymerization of MMA. The presence of surface modified TiO₂ nanoparticles do not have an influence on the mobility of PMMA chain segments leading to the same values of glass transition temperature for all investigated samples. Thermal and thermo-oxidative stability of the PMMA matrix are improved by introducing TiO₂ nanoparticles modified with gallates.     

Preparation and characterization of film-forming raspberry-like polymer/silica nanocomposites via soap-free emulsion polymerization and the sol–gel process

Herein, we report on the synthesis of film-forming poly(styrene-co-butyl acrylate-co-acrylic acid)/SiO₂ [P(St-BA-AA)/SiO₂] nanocomposites by in situ formation of SiO₂ nanoparticles from TEOS via sol–gel process in the presence of poly(acrylic acid) (PAA)-functionalized poly(styrene-co-butyl acrylate) [P(St-BA)] particles fabricated by soap-free emulsion polymerization. The formed silica particles could be absorbed by polyacrylate chains on the surface of PAA-functionalized P(St-BA) particles; thus, raspberry-like polymer/silica nanocomposites would be obtained. Transmission electron microscopy, Fourier transform infrared spectroscopy, attenuated total reflectance infrared spectrum, ultraviolet–visible transmittance spectra, and thermogravimetric analysis were used to characterize the resulting composites. The results showed that the hybrid polymer/silica had a raspberry-like structure with silica nanoparticles anchored on the surface of polymer microspheres. The thermal, fire retardant, and mechanical properties and water resistance of the film were improved by incorporating silica nanoparticles, while the optical transmittance was seldom affected due to nanosized silica particles uniformly dispersed in the film.

Effect of nanoparticles on the thermal stability of PMMA nanocomposites prepared by in situ bulk polymerization

Al₂O₃ and ZnO filled poly(methyl methacrylate) nanocomposites were synthesized by free radical (bulk) polymerization. Efficient dispersion was achieved by predispersing the nanoparticles in propylene glycol methyl ether acetate (PGMEA) followed by ultrasonication of nanoparticles into the PMMA syrup. Thermal analysis confirms chemisorption between PGMEA and metal oxide particles. The addition of nanoparticle affects degradation mechanism and consequently improves thermal stability of PMMA. The reduction of polymer chain mobility and the tendency of nanoparticles to eliminate free radicals are the principal effects responsible for these enhancements.     

Morphology and thermal properties of polyhedral oligomeric silsesquioxane/polybutadiene nanocomposites prepared by anionic polymerization

The morphology and thermal properties of Allylisobutyl Polyhedral Oligomeric Silsesquioxane (POSS)/Polybutadiene (PB) nanocomposites prepared through anionic polymerization technique were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results of XRD, SEM and TEM showed that the aggregation of POSS in PB matrix occurred obviously, forming crystalline domains and the size of POSS particles increased with increasing POSS content. The DSC and TGA results indicated that the glass transition temperature (T _g) of the nanocomposites was significantly increased and the maximum degradation temperature (T _dmax) of nanocomposites was slightly increased compared with pure PB, implying an increase in thermal stability.     

Effect of Organic Nano Carboncapsule Incorporated Modified Clay on Fire‐Retardancy of PMMA Nanocomposites

Here we investigate a new type of highly flame retardant poly(methyl methacrylate) (PMMA) nanocomposite by bulk polymerization of methyl methacrylate (MMA) in the presence of organic nano carboncapsule (OCNC/NCNC)‐incorporated modified montmorillonites (CL120, CL42). The morphology of the modified clay was confirmed by X‐ray diffraction (XRD), and Fourier transform infrared (FT‐IR) spectroscopy was used to identify the functional groups in the clay. The nano morphological characterization of the clay in the PMMA matrix was confirmed by XRD and transmission electron microscopy (TEM). The thermal and mechanical properties of the PMMA nanocomposites were investigated by thermogravimetry and dynamic mechanical analysis, respectively. PMMA containing organo nano carboncapsule‐doped CL42 modified cocoamphodipropionate (K2) (P‐O‐CL42) could achieve very high thermal stability compared to pristine PMMA. The 5% thermal decomposition temperature (T _5d) increased by 63.2°C. Storage modulus of PMMA nanocomposites measured by DMA analysis. An enhancement of storage modulus and significant reduction in the peak heat release (PHR) rate were observed in the almost all PMMA nanocomposites as compared to pristine PMMA. Moreover, these results suggest that PMMA nanocomposites can have potential applications in the building industry and the medical field.     

Preparation of Polyethylene/Graphene Nanocomposites with Octadecylamine‐Modified Graphene Oxide‐MgCl‐Supported Ziegler–Natta Catalyst

In this work, an octadecylamine‐modified graphene oxide (ODA‐GO)‐MgCl‐supported Ziegler–Natta catalyst was synthesized by reacting ODA‐GO with a Grignard reagent, followed by anchoring TiCl₄ to the structure. The effect of the ODA‐GO on the catalyst morphology and ethylene polymerization behavior was examined. The resultant polyethylene (PE)/ODA‐GO nanocomposites directly mirrored the catalyst morphology by forming a layered morphology, and the ODA‐GO fillers were well dispersed in the PE matrix and showed strong interfacial adhesion with it. The resultant PE/ODA‐GO nanocomposites exhibited better thermal stability and mechanical properties than neat PE, even with a small amount of ODA‐GO added. Thus, this work provides a facile approach to the production of high‐performance PE. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 855–860     

The disorderly exfoliated LDHs/PMMA nanocomposites synthesized by in situ bulk polymerization: The effects of LDH-U on thermal and mechanical properties

The disorderly exfoliated layered double hydroxides/poly(methyl methacrylate) (LDHs/PMMA) nanocomposites were obtained in a two-stage process by the in situ bulk polymerization of methyl methacrylate (MMA) in the presence of 10-undecenoate intercalated LDH (LDH-U). The dispersed behavior of the LDH-U in the PMMA matrix was identified by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV/visible transmission spectroscopy. All these nanocomposites showed significantly enhancement of glass transition temperature (T_g) and the decomposition temperatures compared to pristine PMMA, as identified in differential scanning calorimetry (DSC) and thermogravimetric (TGA) analysis. The tensile modulus of these nanocomposites was also enhanced by incorporating the LDH-U into the PMMA matrix and increased as the amount of LDH-U increased. According to the analytical method of Ozawa-Flynn, the degradation activation energies of these nanocomposites are higher than that of pristine PMMA.     

Kinetic study of the thermal degradation of PS/MMT nanocomposites preparedwith imidazolium surfactants

Styrene and montmorillonite organically modified with imidazolium surfactants (MMT) at various alkyl chain lengths (C₁₂, C₁₆ and C₁₈) were used to prepare the corresponding PS/MMT/C₁₂, PS/MMT/C₁₆ and PS/MMT/C₁₈ nanocomposites by in situ polymerization. XRD and TEM analyses evidenced the formation of both intercalated and exfoliated structures. The glass transition temperatures (T _g) of nanocomposites, as well as that of neat PS, were obtained by DSC measurements. The thermal degradations were carried out in the scanning mode, in both inert and oxidative environments, and the initial temperatures of decomposition (T _i) and the apparent activation energies of degradation (E _a) were determined. Due to an oxidative degradation mechanism, the T _i and E _a values in air atmosphere were lower than those under nitrogen. The results indicated that nanocomposites are more thermally stable than polystyrene, and suggested an increasing degree of exfoliation as a function of alkyl chain length of surfactant, associated with enhancing thermal stability.