Poly(methyl methacrylate)/montmorillonite nanocomposites prepared with a novel reactive phosphorus–nitrogen‐containing monomer of N‐(2‐(5,5‐dimethyl‐1,3,2‐dioxaphosphinyl‐2‐ylamino)ethyl)‐ acrylamide and its thermal and flame retardant properties

A novel reactive phosphorus–nitrogen‐containing monomer, N‐(2‐(5,5‐dimethyl‐1,3,2‐dioxaphosphinyl‐2‐ylamino)ethyl)‐acrylamide (DPEAA), was synthesize and characterized. Flame retardant poly(methyl methacrylate)/organic‐modified montmorillonite (PMMA‐DPEAA/OMMT) nanocomposites were prepared by in situ polymerization by incorporating methyl methacrylate, DPEAA, and OMMT. The results from X‐ray diffraction and transmission electron microscopy (TEM) showed that exfoliated PMMA‐DPEAA/OMMT nanocomposites were formed. Thermal stability and flammability properties were investigated by thermogravimetric analysis, cone calorimeter, and limiting oxygen index (LOI) tests. The synergistic effect of DPEAA and montmorillonite improved thermal stability and reduced significantly the flammability [including peak heat release rates (PHRR), total heat release, average mass loss rate, etc.]. The PHRR of PMMA‐DPEAA/OMMT was reduced by about 40% compared with pure PMMA. The LOI value of PMMA‐DPEAA/OMMT reached 27.3%. The morphology and composition of residues generated after cone calorimeter tests were investigated by scanning electronic microscopy (SEM), TEM, and energy dispersive X‐ray (EDX). The SEM and TEM images showed that a compact, dense, and uniform intumescent char was formed for PMMA‐DPEAA/OMMT nanocomposites after combustion. The results of EDX confirmed that the carbon content of the char for PMMA‐DPEAA/OMMT nanocomposites increased obviously by the synergistic effect of DPEAA and montmorillonite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Smoke and toxicity suppression by zinc salts in flame‐retardant polyurethane‐polyisocyanurate foams filled with phosphonate and chlorinated phosphate

Three types of zinc salts, ZnAl₂O₄, ZnFe₂O_4, and Zn₂SiO_4, were prepared by coprecipitation. Potential smoke and toxicity suppression by zinc salts in flame‐retardant polyurethane‐polyisocyanurate foams (FPUR‐PIR) with dimethylmethylphosphonate (DMMP) and tris (2‐chloropropyl) phosphate (TCPP) were investigated. The crystal structure and dispersity of zinc salts in FPUR‐PIR were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Smoke density, flame retardancy, and thermal degradation were studied using smoke density rating (SDR), limiting oxygen index (LOI), the cone calorimeter test, and thermogravimetry coupled with FTIR spectrophotometry (TGA‐FTIR). The results indicated that pure zinc salts were obtained and evenly dispersed on the cell wall of FPUR‐PIR. SDR and the specific extinction area (SEA) were significantly decreased, the time to second heat release rate peak (pk‐HRR) of FRUP‐PIR was delayed after incorporation of the zinc salts; zinc salts partially inhibited phosphorus oxide release into the gas phase, enhanced the condensed phase effect of phosphorus, reduced, and prolonged the release of isocyanate compound and hydrogen cyanide from FRUP‐PIR; due to an increase in the amount of char residues, which indicated the suppression of smoke and toxicity volatiles. ZnFe₂O₄ resulted in better char formation at the initial degradation stage of FPUR‐PIR, and ZnAl₂O₄ retained more phosphorus in the solid phase at higher temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41846.     

Thermal behavior and properties of polystyrene/poly(methyl methacrylate) blends

The thermal behavior and properties of immiscible blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with and without PS‐b‐PMMA diblock copolymer at different melt blending times were investigated by use of a differential scanning calorimeter. The weight fraction of PS in the blends ranged from 0.1 to 0.9. From the measured glass transition temperature (T_g) and specific heat increment (ΔC_p) at the T_g, the PMMA appeared to dissolve more in the PS phase than did the PS in the PMMA phase. The addition of a PS‐b‐PMMA diblock copolymer in the PS/PMMA blends slightly promoted the solubility of the PMMA in the PS and increased the interfacial adhesion between PS and PMMA phases during processing. The thermogravimetric analysis (TGA) showed that the presence of the PS‐b‐PMMA diblock copolymer in the PS/PMMA blends afforded protection against thermal degradation and improved their thermal stability. Also, it was found that the PS was more stable against thermal degradation than that of the PMMA over the entire heating range. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 609–620, 2004     

Influence of nanozirconia on the thermal stability of poly(methyl methacrylate) prepared by in situ bulk polymerization

Nanozirconia (nano‐ZrO₂) was prepared by the sol–gel method and incorporated into poly(methyl methacrylate) (PMMA) by the in situ bulk polymerization of methyl methacrylate. The structure of the nano‐ZrO₂ was confirmed by X‐ray diffraction (XRD), transmission electron microscopy, and Fourier transform infrared (FTIR) spectroscopy. The structure of the nano‐ZrO₂ nanocomposites were studied by differential scanning calorimetry, FTIR spectroscopy, XRD, and scanning electron microscopy, and the results show that there were interactions between the nanoparticles and the polymer. The influence of the nano‐ZrO₂ on the thermal stability of PMMA was investigated by thermogravimetric analysis (TGA). The results indicate that nano‐ZrO₂ enhanced the thermal stability of the PMMA/nano‐ZrO₂ nanocomposites. The effects of the heating rate in dynamic measurements (5–30°C/min) on kinetic parameters such as apparent activation energy (E_a) in TGA both in nitrogen and air were investigated. The Kissinger method was used to determine E_a for the degradation of pure PMMA and the PMMA/nano‐ZrO₂ nanocomposites. The kinetic results show that the values of E_a for the degradation of the nanocomposites were higher than that of pure PMMA in air. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Novel flame‐retardant epoxy based on zinc methylethyl phosphinate

A novel flame retardant zinc methylethylphosphinate (Zn(MEP)) was used to fill epoxy resins (EPs). The structure of Zn(MEP) was conformed with Fourier transform infrared, hydrogen nuclear magnetic resonance and phosphorus nuclear magnetic resonance, and X‐ray fluorescent and X‐ray diffraction. The flammability, decomposition behavior, and glass transition temperature (T_g) of cured EP/Zn(MEP) were investigated. Zn(MEP) is stable below 406°C. EP containing 20 phr of Zn(MEP) achieves 27.5% of limiting oxygen index and UL‐94 V0 rating. Scanning electron microscopy‐energy‐dispersive X‐ray and Fourier transform infrared spectroscopy investigations show that a condensed char layer with carbon‐rich and phosphorus‐rich components was formed during heating Zn(MEP)/EP, the atomic ratio of P to Zn on the surface of the char is reduced compared with the initial sample. The P‐rich components and lower atomic ratio of P/Zn on the char surface implies that the Zn(MEP) acts in both condensed phase and gas phase. TGA investigation shows that there are interactions between Zn(MEP) and EP when they are copyrolyzed. The interactions lead to a modification in degradation process and promote the char forming. Compared with aluminum diethylphosphinate Zn(MEP) filled EP shows lower limiting oxygen index but higher T_g. In addition, the interactions between polymer and additive are different when aluminum diethylphosphinate instead of Zn(MEP) is added into EP. Copyright © 2013 John Wiley & Sons, Ltd.     

Ecofriendly modification of acetosolv lignin from oil palm biomass for improvement of PMMA thermo‐oxidative properties

The environmentally friendly esterification of acetosolv lignin (AL), obtained from pressed oil palm mesocarp fibers, is described, for the improvement of thermo‐oxidative properties of poly(methyl methacrylate) (PMMA) films. Acetylation of AL was performed in ecofriendly conditions using acetic anhydride in the absence of catalysts. Acetylated acetosolv lignin (AAL) was successfully obtained in only 12 min with a solvent‐free and catalyst‐free microwave‐assisted procedure. Lignins were characterized by Fourier transform infrared spectroscopy, size exclusion chromatography, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), confirming the efficacy of the methodology employed. AL and AAL as fillers in different concentrations (1% and 5%) were added to PMMA films. The thermal and mechanical properties of the lignin‐incorporated films were analyzed by TGA, DSC, and dynamic mechanical analysis (DMA). The films incorporated with lignin and acetylated lignin presented initial degradation temperature (T_onset) and onset oxidative temperature (OOT) values higher than pure PMMA films, contributing thus to an enhancement of thermo‐oxidative stability of PMMA. The DMA analyses showed that incorporation of AL or AAL increased the storage modulus (E′) of PMMA films, but did not affect their glass‐transition temperatures (T_g). The results indicate the potential use of oil palm mesocarp lignin to enhance the thermo‐oxidative properties of PMMA without compromising its mechanical response. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45498.     

Thermal degradation and flammability of nanocomposites composed of silica cross-linked to poly(methyl methacrylate)

The effect of polymer cross-linkages on thermal degradation of silica/poly (methyl methacrylate) (PMMA) nanocomposites is investigated using a single novel nanoparticle. Nanosilica surface treated with KH570, an organic surface treatment capable of free-radical polymerisation, was used to cross-link PMMA via an in situ method. Scanning electron microscopy was used to characterise nanosilica before use, while X-ray diffraction confirmed silica was well dispersed in PMMA. Thermogravimetric analysis (TGA) results showed that thermal degradation of silica cross-linked nanocomposites was significantly stabilised compared to PMMA, with a 30% reduction in the peak mass loss rate. Kinetic studies revealed the degradation of nanocomposites in this work abide by first-order kinetics, with an increase in the degradation activation energy of approximately 100?kJ?mol^?1. This is nearly double the improvement compared to conventional PMMA-silica nanocomposites in literature, showing dramatic enhancements to thermal stability. Analysis of high-temperature residuals from TGA tests suggest that cross-linked silica have increased char yields when compared with both PMMA and traditional silica nanocomposites. Cone Calorimetry results showed the materials in this work have reduced heat release rates compared to PMMA and traditional silica-PMMA nanocomposites.     

Degradation of poly(methyl methacrylate) (PMMA) with aluminum nitride and alumina

This paper deals with the thermal and thermal-oxidative degradation of pure poly(methyl methacrylate) (PMMA), PMMA/A1N and PMMA/Al₂O₃ composites. Kinetic parameters were determined from the weight loss data using non-isothermal Thermogravimetric Analysis (TGA). The amount and morphology of the carbon residue in the burnt samples under N₂ and air atmospheres were also investigated using a Leco combustion analyzer. This study also showed that the normally accepted three-stage polymer thermal degradation, and hence three regions of Arrhenius linearity, can be treated with one value of activation energy. This is a basic departure from the normally accepted three different regions and applying the same diffusion equation (such as Jander diffusion) separately to each region. In nitrogen atmosphere, the activation energy of pure PMMA was 129.4 kJ/mol; however, the activation energies of 14% PMMA/AlN and PMMA/Al₂O₃ were found to be 119.5 and 118.2 kJ/mol, respectively.     

Kinetic analysis and modelling of thermal degradation of perspex (PMMA) and perspex blend plastic waste

The thermal decomposition of pure perspex and a mixture of 50% perspex and 50% poly(ethylene terephthalate; PET) was carried out between 295 and 325°C using a thermogravimetric analyser (TGA) in air and nitrogen (N₂) atmosphere. The weight losses of decomposition products were measured during these experiments. The thermal degradation process is slower in inert atmosphere than air, where oxidation reaction expedites the decomposition process. Kinetic rate constants (k), pre‐exponential factor (A) and activation energy (E) for both pure prespex and a blend of perspex/PET were calculated for both air and N₂ conditions. The thermal degradation process followed a third‐order reaction in air and second‐order in N₂. A second‐order (n = 2) model for the pyrolytic process based on simultaneous reactions was developed using experimental data for pure and blend. The pyrolytic products are gases, liquids, waxes, aromatics and char, which can be ultimately used as raw material and fuel in various applications. It is important to note that the addition of PET to perspex was found to suppress/inhibit the decomposition of perspex compared with pure perspex. Pre‐exponential factor (A) and activation energy (E) values support such an observation. © 2012 Canadian Society for Chemical Engineering     

Synthesis and thermal behavior of poly(methyl methacrylate)/Maghnia bentonite nanocomposite prepared at room temperature via in situ polymerization initiated by a new Ni(II)α‐benzoinoxime complex

Poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate)/clay nanocomposite (PMMA/OBT) were successfully prepared in dioxan at room temperature via in situ radical polymerization initiated by a new Ni(II)α‐ Benzoinoxime complex as a single component in presence of 3% by weight of an organically modified bentonite (OBT) (originated from Maghnia, Algeria) and characterized by FTIR, ¹H‐NMR and viscometry. Mainly intercalated and partially exfoliated PMMA/OBT nanocomposite was elaborated and evidenced by X‐Ray diffraction (XRD) and transmission electron microscopy (TEM). The intrinsic viscosity of PMMA/OBT nanocomposite is much higher than the one of pure PMMA prepared under the same conditions. Differential scanning calorimetry (DSC) displayed an increase of 10°C in the glass transition temperature of the elaborated PMMA/OBT nanocomposite relative to the one of pure PMMA. Moreover, the TGA analysis confirms a significant improvement of the thermal stability of PMMA/OBT nanocomposite compared to virgin PMMA: the onset degradation temperature of the nanocomposite, carried out under nitrogen atmosphere, increased by more than 45°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

DOPO‐VTS‐based coatings in the realm of fire retardants for cotton textile

The work elucidates the feasibility of incorporation of phosphorus‐silicon containing fire retardant (10‐(2‐trimethoxysilyl‐ethyl)‐9‐hydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide [DOPO‐VTS]) into nanosol coating solutions by cohydrolysis cocondensation reaction of DOPO‐VTS with tetraethoxysilane precursor (TEOS). Impregnation of cotton with the organophosphorus silane in a form of nanosol dispersion afforded better fire retardancy of such samples compared to pure DOPO or TEOS‐treated cotton indicating synergism between phosphorus and silicon containing species in a condensed phase. The detailed analysis by TGA‐MS and SEM pointed to the fact that DOPO‐VTS acts as a promoter of cotton degradation which, in turn, results in acceleration of the charring process and formation of compact char in contrast to TEOS‐treated samples. Further analysis of the char by XPS confirmed high content of carbonaceous residue in the case of DOPO‐VTS‐treated samples while mainly siliceous component was left in the char in case of cotton treated with TEOS. Standard flammability test (EN ISO 15025:2008) additionally confirmed the absence of smoldering and better overall fire performance of the DOPO‐VTS samples in contrast to TEOS‐treated samples. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41955.     

The effects of polymer‐nanofiller interactions on the dynamical mechanical properties of PMMA/CaCO3 composites prepared by microemulsion template

We prepared novel poly(methyl methacrylate) (PMMA)/CaCO₃ nanocomposites by using reverse micelle as a template. The nanoparticles of CaCO₃ were prepared by the reverse microemulsion with functional monomer, methyl methacrylate (MMA) as oily phase, and the PMMA/CaCO₃ nanocomposite was obtained via polymerization of MMA monomer. The SEM image showed that the nanoparticles of CaCO₃ were dispersed in the polymer matrix. Dynamic mechanical analysis (DMTA) was performed to investigate the interaction between the nanoparticles and the polymer chains. In the low‐temperature ripening process, two tan δ peaks were observed in the nanocomposite, corresponding to the glass transitions of the matrix and the interface layer. In the high‐temperature ripening process, only one tan δ peak was observed, suggesting that the interface layer forms a continuous phase. The nanoparticles behave as a physical crosslinker in the interface layer. Modification of the surface of nanoparticles with polyacrylamide and poly(N,N′‐methylenedisacrylamide) in the nanocomposite did not show an appreciable effect on the interaction of nanoparticles with the matrix. Upon removal of the aqueous phase around the nanoparticles, we obtained surface‐capped nanoparticles by using an improved reverse microemulsion technique. Another PMMA/CaCO₃ nanocomposite was also obtained with these modified nanoparticles. DMTA analysis of this nanocomposite demonstrated that the aqueous phase layer around the nanoparticles does not significantly affect the interaction between the nanoparticles and the polymer chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2739–2749, 2004     

Synthesis and performance of a novel nitrogen‐containing cyclic phosphate for intumescent flame retardant and its application in epoxy resin

A novel nitrogen‐containing cyclic phosphate (NDP) was synthesized and well characterized by ¹H, ¹³C, ³¹P NMR, mass spectra and elemental analysis. NDP was used as an additive intumescent flame retardant (AIFR) to impart flame retardancy and dripping resistance for diglycidyl ether of bisphenol‐A epoxy resin (DGEBA) curied by 4,4′‐diaminodiphenylsulfone (DDS) with different phosphorus content. The flammability, thermal stability, and mechanical properties of NDP modified DGEBA/DDS thermosets were investigated by UL‐94 vertical burning test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Izod impact strength and flexural property tests. The results showed that NDP modified DGEBA/DDS thermosets exhibited excellent flame retardancy, moderate changes in glass transition temperature and thermal stability. When the phosphorus content reached only 1.5 wt %, the NDP modified DGEBA/DDS thermoset could result in satisfied flame retardancy (UL‐94, V‐0). The TGA curves under nitrogen and air atmosphere suggested that NDP had good ability of char formation, and there existed a distinct synergistic effect between phosphorus and nitrogen. The flame retardant mechanism was further realized by studying the structure and morphology of char residues using FT‐IR and scanning electron microscopy (SEM). It indicated that NDP as phosphorus‐nitrogen containing flame retardant worked by both of the condensed phase action and the vapor phase action. Additionally, the addition of NDP decreased slightly the flexural strength of the flame retarded DGEBA epoxy resins, and increased the Izod impact strength of these thermosets. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41859.     

Fabrication of polymethyl methacrylate/polysulfone/nanoceramic composites for orthopedic applications

We report the fabrication of polymethyl methacrylate/polysulfone/nanohydroxyapatite (PMMA/PSu/nHA) and PMMA/PSu/nanotitania (PMMA/PSu/nTiO₂) composites using N′N′‐methylene‐bis‐acrylamide (MBA) to crosslink PMMA and act as a blending agent. The composite was made porous by incorporating polyethylene glycol as the pore‐forming agent. The blend between PMMA and PSu was confirmed using Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). The surface morphology of the composites analyzed using scanning electronic microscopy (SEM) revealed the porous structure and the wide distribution of the fillers that were found to aggregate at higher concentrations. The maximum tensile strength observed for composites was with 5% nHA (23 MPa) and 7.5% TiO₂ (30 MPa). The TGA of the composites showed better thermal stability with increase in the filler concentrations. The X‐ray diffraction analysis showed that appearance of new peaks in the blend polymers indicating a strong interaction between PMMA and PSu. The surface of the composites was coated with amoxicillin and its efficiency was examined by the Zone of Inhibition test using Streptococcus mutans. The bioactivity of the composites was evaluated by immersing them in simulated body fluid and examining their surface for the formation of calcium‐phosphate layer using SEM and EDAX. Bioactivity was found to increase with increase in filler content. The in vitro biocompatibility of the composites, evaluated using monkey kidney epithelial cells by MTT assay showed that the composites containing nHA showed better cell viability than the composites with nTiO₂. The study showed that the composites with nTiO₂ exhibited better strength when compared with nHA composites while the later exhibited better biocompatibility. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of methyl methacrylate and N‐aryl itaconimide block copolymers via atom‐transfer radical polymerization

The paper describes the synthesis of block copolymers of methyl methacrylate (MMA) and N‐aryl itaconimides using atom‐transfer radical polymerization (ATRP) via a poly(methyl methacrylate)–Cl/CuBr/bipyridine initiating system or a reverse ATRP AIBN/FeCl₃·6H₂O/PPh₃ initiating system. Poly(methyl methacrylate) (PMMA) macroinitiator, ie with a chlorine chain‐end (PMMA‐Cl), having a predetermined molecular weight (M_n = 1.27 × 10⁴ g mol^?1) and narrow polydispersity index (PDI = 1.29) was prepared using AIBN/FeCl₃·6H₂O/PPh₃, which was then used to polymerize N‐aryl itaconimides. Increase in molecular weight with little effect on polydispersity was observed on polymerization of N‐aryl itaconimides using the PMMA‐Cl/CuBr/Bpy initiating system. Only oligomeric blocks of N‐aryl itaconimides could be incorporated in the PMMA backbone. High molecular weight copolymer with a narrow PDI (1.43) could be prepared using tosyl chloride (TsCl) as an initiator and CuBr/bipyridine as catalyst when a mixture of MMA and N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 was used. Thermal characterization was performed using differential scanning calorimetry (DSC) and dynamic thermogravimetry. DSC traces of the block copolymers showed two shifts in base‐line in some of the block copolymers; the first transition corresponds to the glass transition temperature of PMMA and second transition corresponds to the glass transition temperature of poly(N‐aryl itaconimides). A copolymer obtained by taking a mixture of monomers ie MMA:N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 showed a single glass transition temperature. Copyright © 2005 Society of Chemical Industry     

Flame retardant modification of acrylic fiber with hydrazine hydrate and sodium ions

The sodium ions were introduced into the acrylic fibers by post‐treating the fibers with hydrazine hydrate and aqueous sodium hydroxide to improve the flame resistance of the fibers. The molecular structure of the modified acrylic fibers was characterized by FTIR spectra. The flame resistance of the acrylic fibers was significantly increased after post‐treatment and was relied mostly on the content of sodium ions. The flame‐retardant mechanism of the modified fiber was studied in details. The micro calorimeter tests showed that the total heat release and the peak heat release rate were largely reduced after post‐treatment. Photographs of the char residues and the results of TGA and TG‐IR technique revealed that the flame retardance of the modified acrylic fiber was provided through the combination effect of the gas phase and condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41996.     

Synthesis of poly(butyl acrylate)—laponite nanocomposite nanoparticles for improving the impact strength of poly(lactic acid)

This work aims at preparing and characterizing poly(butyl acrylate) (PBA)—laponite (LRD) nanocomposite nanoparticles and nanocomposite core (PBA‐LRD)‐shell poly(methyl methacrylate) (PMMA) nanoparticles, on the one hand, and the morphology and properties of poly(lactic acid) (PLA)‐based blends containing PBA‐LRD nanocomposite nanoparticles or (PBA‐LRD)/PMMA core–shell nanoparticles as the dispersed phase, on the other hand. The PBA and (PBA‐LRD)/PMMA nanoparticles were synthesized by miniemulsion or emulsion polymerization using LRD platelets modified by 3‐methacryloxypropyltrimethoxysilane (MPTMS). The grafting of MPTMS onto the LRD surfaces was characterized qualitatively using FTIR and quantitatively using thermogravimetric analysis (TGA). The amounts of LRD in the PBA‐LRD nanocomposites were characterized by TGA. The PBA/PMMA core–shell particles were analyzed by ¹H‐NMR. Their morphology was confirmed by SEM and TEM. Mechanical properties of (PBA‐LRD)/PLA blends and (PBA‐LRD)/PMMA/PLA ones were tested and compared with those of the pure PLA, showing that core–shell particles allowed increasing impact strength of the PLA while minimizing loss in Young modulus and tensile strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal and mechanical properties of melt processed intercalated poly(methyl methacrylate)–organoclay nanocomposites over a wide range of filler loading

BACKGROUND: Poly(methyl methacrylate) (PMMA)–organoclay nanocomposites with octadecylammonium ion‐modified montmorillonite, prepared via melt processing, over a wide range of filler loading (2–16 wt%) were investigated in detail. These hybrids were characterized for their dispersion structure, and thermal and mechanical properties, such as tensile modulus (E), break stress (σ_brk), percent break strain (ε_brk) and ductility (J), using wide‐angle X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile and impact tests. RESULTS: Intercalated nanocomposites were formed even in the presence of 16 wt% clay (high loading) in PMMA matrix. PMMA intercalated into the galleries of the organically modified clay, with a change in d‐spacing in the range 11–16 Å. TGA results showed improved thermal stability of the nanocomposites. The glass transition temperature (T_g) of the nanocomposites, from DSC measurements, was 2–3 °C higher than that of PMMA. The ultimate tensile strength and impact strength decreased with increasing clay fraction. Tensile modulus for the nanocomposites increased by a significant amount (113%) at the highest level of clay fraction (16 wt%) studied. CONCLUSION: We show for the first time the formation of intercalated PMMA nanocomposites with alkylammonium‐modified clays at high clay loadings (>15 wt%). Tensile modulus increases linearly with clay fraction, and the enhancement in modulus is significant. A linear correlation between tensile strength and strain‐at‐break is shown. Thermal properties are not affected appreciably. Organoclay can be dispersed well even at high clay fractions to form nanocomposites with superior bulk properties of practical interest. Copyright © 2007 Society of Chemical Industry     

Fe‐mediated SET‐LRP of MMA and St in the presence of air

In this work, well‐defined homopolymers of methyl methacrylate (PMMA) and styrene (PSt) were prepared via single‐electron‐transfer living radical polymerization using CCl₄ as initiator and Fe(0)/N, N, N′,N′‐tetramethyl‐1,2‐ethanediamine as catalyst. The polymerization was conducted at 25 °C in N,N‐dimethylformamide in the presence of air. It proceeded in a ‘living’ manner, as indicated by the first‐order kinetics behavior, and the linear increase of the number‐average molecular weight (M_{n, GPC}) with conversion was close to the theoretical M_{n, theory}. Solvent and additives have a profound effect on the polymerization. In addition, the PMMA and PSt obtained remained of low dispersity. The chain‐end functionality of the obtained homopolymer of PMMA was characterized by proton nuclear magnetic resonance. A block copolymer of P(MMA‐block‐St) was achieved by using the obtained PMMA as macroinitiator. The living characteristics were further demonstrated by chain extension experiments. Copyright © 2012 Society of Chemical Industry     

Effect of in situ polymerization conditions of methyl methacrylate on the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene) PMMA/AES Blends

In this study, the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene‐g‐styrene) (PMMA‐AES) blends were investigated with emphasis on the influence of the in situ polymerization conditions of methyl methacrylate. PMMA‐AES blends were obtained by in situ polymerization, varying the solvent (chloroform or toluene) and polymerization conditions: method A—no stirring and air atmosphere; method B—stirring and N₂ atmosphere. The blends were characterized by infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). The results showed that the PMMA‐AES blends are immiscible and present complex morphologies. This morphology shows an elastomeric dispersed phase in a glassy matrix, with inclusion of the matrix in the elastomer domains, suggesting core shell or salami morphology. The occlusion of the glassy phase within the elastomeric domains can be due to the formation of graft copolymer and/or phase inversion during polymerization. However, this morphology is affected by the polymerization conditions (stirring and air or N₂ atmosphere) and by the solvent used. The selective extraction of the blends' components and infrared spectroscopy showed that crosslinked and/or grafting reactions occur on the elastomer chains during MMA polymerization. The glass transition of the elastomer phase is influenced by morphology, crosslinking, and grafting degree and, therefore, T_g depends on the polymerization conditions. On the other hand, the behavior of T_g of the glassy phase with blend composition suggests miscibility or partial miscibility for the SAN phase of AES and PMMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012