Synthesis of poly(methyl methacrylate) nanocomposites via emulsion polymerization using a zwitterionic surfactant

The synthesis of nanocomposites via emulsion polymerization was investigated using methyl methacrylate (MMA) monomer, 10 wt % montmorillonite (MMT) clay, and a zwitterionic surfactant octadecyl dimethyl betaine (C18DMB). The particle size of the diluted polymer emulsion was about 550 nm, as determined by light scattering, while the sample without clay had a diameter of about 350 nm. The increase in the droplet size suggests that clay was present in the emulsion droplets. X-ray diffraction indicated no peak in the nanocomposites. Transmission electron microscopy showed that emulsion polymerization of MMA in the presence of C18DMB and MMT formed partially exfoliated nanocomposites. Differential scanning calorimetry showed an increase of 18 degrees C in the glass transition temperature (Tg) of the nanocomposites. A dynamic mechanical thermal analyzer also verified a similar Tg increase, 16 degrees C, for the partially exfoliated nanocomposites over poly(methyl methacrylate) (PMMA). Thermogravimetric analysis indicated a 37 degrees C increase in the decomposition temperature for a 20 wt % loss. A PMMA nanocomposite with 10 wt % C18DMB-MMT was also synthesized via in situ polymerization. This nanocomposite was intercalated and had a Tg 10 degrees lower than the emulsion nanocomposite. The storage modulus of the partially exfoliated emulsion nanocomposite was superior to the intercalated structure at higher temperatures and to the pure polymer. The rubbery plateau modulus was over 30 times higher for the emulsion product versus pure PMMA. The emulsion technique produced nanocomposites of the highest molecular weight with a bimodal distribution. This reinstates that exfoliated structures have enhanced thermal and mechanical properties over intercalated hybrids.     

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.     

Transparent and flame retardant PMMA/clay nanocomposites prepared with dual modified organoclay

In this study, the dual modified organoclay (DMC), was successfully prepared by the successive cationic exchange reactions of the sodium montomorillonite clay (MMT) with two intercalating reagents, hexadecyl‐triphenyl‐phosphonium bromide and 2‐methacryloxy‐ethyl‐hexadecyl‐dimethyl‐ammonium bromide. A series of the PMMA/DMC nanocomposite membranes (PDCM) were then prepared with the PMMA matrix and various amounts of DMC via the solution cast method. The results of XRD, TEM, SEM, and UV–VIS measurements of the PDCMs prepared showed that the DMC particles were well dispersed in the PMMA matrix with a highly exfoliated structure. The TGA thermograms indicated that the thermal stabilities of the PDCM membranes are higher than that of the PMMA. Furthermore, the tensile mechanical property and glass transition temperature of the nanocomposites were dramatically increased with increasing the DMC content. The limiting oxygen index of PDCM membranes also indicated that the flame retardancy was significantly enhanced due to the presence of DMC. Moreover, more than 90% of the PMMA's transparency was remained in the nanocomposites. Copyright © 2011 John Wiley & Sons, Ltd.     

The effects of several sulfonates on thermal and fire retardant properties of poly(methyl methacrylate) and polystyrene

Three different sulfonates (sodium diphenylamine‐4‐sulfonate [SDPAS], 3‐(1‐pyridino)‐1‐propane sulfonate [PPS], and ammonium sulfamate) have been melt blended with polystyrene (PS) or poly(methyl methacrylate) (PMMA) and with clay to make composites. All have been examined by X‐ray diffraction to determine the morphology, by thermogravimetry to determine thermal stabilities, and by cone calorimetry to evaluate fire retardancy. All three sulfonates enhance the thermal stability of the PMMA composites, and SDPAS achieves the greatest improvement. SDPAS also seems to aid in the dispersion of the clay in the polymer. Combination of sulfonates (5 or 10 wt% SDPAS, or 5 wt% PPS) with an organically modified clay exhibit enhanced fire retardancy. The three sulfonates did not enhance the thermal stability of the PS composites; however, there is a reduction in the peak heat release rate. The presence of ammonium sulfamate in PS brings about a 52% reduction in the peak heat release rate. The combination of sulfonates (5 or 10 wt% PPS, or 10 wt% SDPAS) with an organically modified clay provides some fire retardancy to the PS composites. Copyright © 2013 John Wiley & Sons, Ltd.     

PMMA/MMT nanocomposites prepared by one-step in situ intercalative solution polymerization

Poly(methylmetacrylate)/montmorillonite (PMMA)/(MMT) nanocomposites were prepared by one-step in situ intercalative solution polymerization involving simultaneous modification of MMT with quaternary ammonium salts (QAS), polymerization and polymer intercalation. Polymerization proceeded at 70 °C in a mixture of ethanol and water, whereas the nanocomposite was precipitated with only water. Four QAS’s with different alkyl chain lengths, as well as a QAS with an additional acrylic group, were used to study the influence of the type of quaternary ammonium salt on intercalation. The largest extent of intercalation was achieved in nanocomposites with the QAS having one long alkyl (C16) chain. The obtained PMMA/MMT intercalated nanocomposites exhibited a higher glass transition temperature, better thermal stability, and improved solvent resistance than the pure PMMA.     

Flame retardancy of polyamide 66 nanocomposites with thermally stable organoclay

A thermally stable imidazolium organoclay was synthesized to improve the flame retardancy performance of polyamide 66 (PA 66). To enhance flame retardancy of the PA 66/organoclay nanocomposite, the thermally stable organoclay was coated with monomethylol melamine (MMM) before melt‐compounding with PA 66. Transmission electron microscopy and X‐ray diffraction results confirmed the partial exfoliation of the organoclay in the PA 66 matrix. The use of the thermally stable organoclay did not affect the thermal stability of PA 66. The cone calorimeter results showed that the PA 66/orgnaoclay nanocomposite exhibited a greatly reduced heat release rate and a longer ignition time. However, the PA 66/organoclay binary nanocomposite had no rating in the UL‐94 vertical burning test because it did not extinguish until the entire polymer component was burnt. The PA 66 nanocomposite with 15 wt% of MMM‐coated organoclay performed better in the ignition resistance test than the PA 66/organoclay nanocomposite containing 15 wt% of melamine. Copyright © 2011 John Wiley & Sons, Ltd.     

Cone calorimeter analysis of flame retardant poly (methyl methacrylate)-silica nanocomposites

Nanocomposite is a promising method to reduce fire hazards of polymers. Specifically due to increased interfacial area between polymer and nanofillers, polymer nanocomposites have an advantage in reducing fire hazards efficiently even when the flame retardant additives are at a concentration of 5 mass% or less. In theory, crosslinking between the polymer chains can create a carbon-dense structure to enhance char formation, which can further promote the flame retardancy. However, little research has been done to explore the flammability of crosslinking polymer nanocomposites with a low concentration of nanosilica particles. In this study, crosslinked and non-crosslinked poly (methyl methacrylate) (PMMA) nanocomposites of a low concentration of nanosilica particles have been prepared via an in situ method. Their fire properties were tested by using the cone calorimeter at the heat flux of 50 kW m^?2. Although silica-containing flame retardants tend to negatively affect the ignitability and soot production especially at a high concentration, through the condensed phase mechanism, the samples of high loading rate of nanosilica particles show better fire retardancy performance in the aspect of flammability, including decreased heat release rate, mass loss rate, and total heat release. Additionally, crosslinking indeed attributes to the less intensive combustion of crosslinked PMMA samples, especially at a low concentration of nanosilica. The combination of nanosilica particles with the modification of the internal structure of the polymer nanocomposites might be a good strategy to improve fire retardancy.     

Preparation of porous PMMA/Na–montmorillonite cation-exchange membranes for cationic dye adsorption

Porous PMMA/Na⁺–montmorillonite (MMT) cation-exchange membranes were successfully prepared by entrapment method in this study. One approach (simple mixing) was to mix commercial PMMA polymer with Na⁺–MMT clays in solvent for membrane preparation (Membrane A). The other approach (emulsion polymerization) was to synthesize the PMMA/Na⁺–MMT polymer composite via emulsion polymerization first, followed by membrane casting (Membrane B for Kunipia F clays and Membrane C for PK-802 clays). Membrane morphology and properties were characterized. The thermogravimetric analysis (TGA) verified the near complete incorporation of feed Na⁺–MMT clays in the PMMA/Na⁺–MMT composite membranes, while X-ray diffractograms (WXRD) exhibited the slightly enlarged interlayer spacing of Na⁺–MMT. The range of cation-exchange capacity (CEC) was 9–32 μequiv./47 mm disc. For batch cationic dye adsorption, the best performance was achieved by Membrane B with feed Na⁺–MMT/MMA (M/P) ratio (w/w) = 0.5 and Membrane C with feed M/P = 0.6, where about 95% Methyl violet adsorption was attained in 2 h. The optimal desorption solution was 1 M KSCN in 80% methanol and its related dye desorption efficiency was 92%. In the flow process using one piece of 47 mm disc of Membrane B (M/P = 0.5), dye solution was recirculated for 6 h and ≥85% dye could be removed. Higher than 94% of dye was desorbed at 1 or 4 mL/min, and the membrane regenerability was proved by successfully performing three consecutive cycles.     

A comparison of the fire retardancy of poly(methyl methacrylate) using montmorillonite, layered double hydroxide and kaolinite

Montmorillonite, layered double hydroxide and kaolinite, have been used to make (nano)composites with poly(methyl methacrylate). X-ray diffraction and transmission electron microscopy were used to characterize the morphology and the thermal stability and fire properties have been studied by thermogravimetric analysis and cone calorimetry. The results show that LDH and MMT are better dispersed in PMMA than is kaolinite; the MMT layers have a higher aspect ratio than does the LDH. PMMA + MMT and PMMA + LDH composites have higher thermal stability than PMMA + kaolinite composite. The peak of heat release rate reduction is 55% for the PMMA + MMT composite at 10%, 45% for PMMA + LDH and 23% for PMMA-kaolinite.     

Flammability of carbon nanofiber–clay nanopaper based polymer composites

In this study, a hybrid nanopaper consisting of carbon nanofiber (CNF), and pristine montmorillonite clay (MMT, Cloisite Na⁺) was fabricated through a paper‐making process. The hybrid nanopaper was coated onto the surface of glass fiber (GF) reinforced polymer matrix composites through resin transfer molding process. The characterization results using scanning electron microscopy (SEM) and energy dispersion analysis of X‐ray (EDAX) show that the nanopaper had a porous structure and the polymer resin completely penetrated the hybrid nanopaper. The thermogravimetric analysis (TGA) test results revealed that the addition of MMT clay nanoparticles significantly enhanced the thermal stability of the nanopaper. The flammability of composite samples was evaluated by cone calorimeter test under a radiant heat flux of 50 kW/m². The peak heat release rate (PHRR) was dramatically reduced for the composites coated with the CNF–MMT nanopaper. For comparison, the composites coated with the CNF–organic MMT clay (OMT, Cloisite 20A) nanopaper were also evaluated with cone calorimeter test. The test results showed that the MMT clay was more effective than the OMT in the reduction of the PHRR. The combustion behavior of these samples was also examined by microscale combustion calorimetry (MCC) test. The PHRR obtained from the MCC test decreased with the MMT content in the nanopaper, which was in good agreement with cone calorimeter test results. Copyright © 2010 John Wiley & Sons, Ltd.     

辐照法制备PVAc/蒙脱土纳米复合材料及其表征

蒙脱土有机化后 ,片层结构间距离增大 ,对有机物的亲和性有所增强 .采用VAc单体渗入有机化蒙脱土层间 .经γ 射线辐照引发原位插层聚合 ,使蒙脱土片层结构发生剥离 ,形成无机 有机纳米复合材料 .并用X衍射、红外光谱、扫描电镜以及透射电镜等现代测试手段对复合材料进行了表征     

纳米二氧化硅表面接枝9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物以及对聚甲基丙烯酸甲酯复合材料阻燃性能和透明性的影响

聚甲基丙烯酸甲酯(PMMA)是一种重要的透明高分子材料,但是PMMA的易燃性限制了其应用。 本工作在纳米二氧化硅表面接枝含磷阻燃剂9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO),并用于聚甲基丙烯酸甲酯(PMMA)的改性。 极限氧指数(LOI)、垂直燃烧(UL-94)和锥形量热(CCT)测试结果表明,制备的PMMA复合材料的阻燃性能大幅度提高,这主要归因于纳米粒子和含磷阻燃剂的协同阻燃作用,形成致密的炭保护层结构。 同时,二氧化硅接枝DOPO的加入可以保持PMMA良好的透明性,这有利于材料在光学透明性要求较高的领域的应用。     

Investigation of Structural,Rheological and Thermal Properties of PMMA/ONi-Al LDH Nanocomposites Synthesized via 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(Tg) of around 3 K. The activation energy(Ea), 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.     

Preparation and Characterization of PMMA/MMT Organic-Inorganic Hybrid Materials via RAFT Polymerization

In this article, the poly(methyl methacrylate)/montmorillonite (PMMA/MMT) organic-inorganic hybrid materials were prepared by conventional free radical polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization, respectively. The kinetics comparison of these two polymerizations was studied. The PMMA/MMT hybrid materials were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). According to these results, we knew that the polymerization behavior of MMA showed controlled/living radical polymerization (CLRP) characteristics under the control of RAFT agent. The incorporation of RAFT agent and MMT nanoparticles improved the thermal properties of polymers, and the thermal stability of polymers increased with increasing content of MMT nanoparticles. The structures and morphologies of PMMA/MMT hybrid materials were characterized by FT-IR, XRD and TEM. These results showed that the MMA monomer can be initiated and propagated in the clay layers of MMT via the control of RAFT agent, and then the exfoliated structure was obtained for the hybrid materials.     

Methyl methacrylate oligomerically-modified clay and its poly(methyl methacrylate) nanocomposites

A methyl methacrylate oligomerically-modified clay was used to prepare poly(methyl methacrylate) clay nanocomposites by melt blending and the effect of the clay loading level on the modified clay and corresponding nanocomposite was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed intercalated/delaminated morphology with good nanodispersion. The compatibility between the methylacrylate-subsituted clay and poly(methyl methacrylate) (PMMA) are greatly improved compared to other oligomerically-modified clays.     

不同链长的聚醚铵阳离子协同插层对蒙脱土性能的影响

为了制备高性能的聚合物/蒙脱土纳米复合材料, 必须对蒙脱土(MMT)进行有机改性来改善蒙脱土表面的疏水性、提高蒙脱土与聚合物之间的相容性, 同时也需要尽可能地增大蒙脱土的层间距. 为此, 提出了一种采用不同链长的聚醚铵阳离子协同插层MMT 的新方法, 即采用D2000(或T5000)聚醚铵盐与D400 聚醚铵盐协同插层MMT, 并采用X射线衍射分析(XRD)和热重分析(TGA)研究了协同插层对改性MMT 的层间距、有机含量以及耐热性的影响. 另外, 也研究了插层过程中的搅拌方式和D400 聚醚铵盐多次插层对改性MMT 的层间距、有机含量等的影响. 研究结果表明,采用长链聚醚铵阳离子协同插层更有利于提高D400 聚醚铵盐改性MMT 的层间距和有机含量; T5000 协同插层MMT中总的有机含量(64.06%)进一步增加, 这可能是因为T5000 的支链在MMT 层间形成的笼型结构既提供了更大的空隙,又起到了屏蔽作用, 同时也得到了较大的层间距(6.86 nm).     

A novel efficient halogen-free flame retardant system for polycarbonate

A novel silicon- and phosphorus-containing flame retardant, poly (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide siloxane), P(DOPO-VTES) was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) and vinyltriethoxy silane(VTES). Its chemical structure was confirmed by FTIR. The thermal gravimetrical analysis (TGA) showed that P(DOPO-VTES) had good thermal stability and a high of char yield (86.31%) at 700 °C in nitrogen atmosphere. Its XRD patterns showed that this compound had a certain ordered structure. P(DOPO-VTES) was blended with polycarbonate (PC) together with montmorillonite(MMT) to prepare a series of organic-inorganic hybrids of flame retardant (PC)/P(DOPO-VTES)/MMT via melt blending. The thermal degradation behavior and flame retardancy of those hybrids were investigated with TGA, limiting oxygen index (LOI), vertical burning test (UL-94), and cone calorimeter. The LOI value of the flame-retardant PC systems could reach a maximal value of 32.8 when the content of P(DOPO-VTES) was 5 wt%. When 2 wt% MMT was added into the PC/5%P(DOPO-VTES) system, the UL-94 rating reached V-0. The possible flame retardant mode of MMT was studied via the dynamic rheological properties of the systems and the morphology of the chars remaining after the LOI test and the cone calorimeter test.     

Thermal properties of epoxy resin nanocomposites based on hydrotalcites

Epoxy resin nanocomposites containing home-made hydrotalcites (HTlc) have been prepared and their properties have been studied and compared with those of montmorillonite (MMT)-type layered silicates-based nanocomposites. Nanofiller dispersion in the polymer matrix has been evaluated by transmission (TEM) electron microscopy and wide angle X-ray diffraction (WAXD), while nanocomposite thermal properties have been studied in detail by thermogravimetric analysis (TGA/DTG) and cone calorimeter tests.The morphological studies have shown that the compatibilisation of the above two type of nanofillers allowed us to obtain nanostructured materials. As far as thermal properties are concerned, nanocomposites based on HTlc are found to decompose, both in air and nitrogen, following a trend similar to that of the neat polymer matrix, while in the case of the nanocomposite based on the organophilic MMT a slight improvement was found in air. Conversely, cone calorimetric tests have demonstrated that only the organophilic hydrotalcite was capable of decreasing the peak of the heat release rate in a relevant way.     

Flame retardancy and charring behavior of polystyrene‐organic montmorillonite nanocomposites

The fire performance of polystyrene‐organic montmorillonite (OMMT) nanocomposite was investigated by limiting oxygen index (LOI) and cone calorimetry. Scanning electron microscopy, electron dispersive spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy were employed to study the charring process of the nanocomposite. The residue collected upon thermal degradation was analyzed by various means to determine its composition and to understand the flame‐retardant mechanism of the nanocomposite. It has been shown that the introduction of OMMT does not have much influence on LOI of the nanocomposite, but can greatly decrease the heat release rate (HRR) and mass loss rate (MLR) and enhance the flame retardancy of the material. The flame‐retardant mechanism is due to charring in the condensed phase. The intercalated nanostructure is destroyed, and the silicate nanolayers in the nanocomposite rearrange and accumulate on the material surface during pyrolysis. The charred residue has a honeycomb‐like porous structure, which covers on the material surface and serves as a protection barrier against heat transfer and mass exchange, leading to enhanced flame retardancy. The charred residue is composed of pyrolyzed silicate layers and graphitic char. The char is highly stable in nitrogen even at 800 °C, but thermo‐oxidative decomposition is allowed, and it can be removed completely in the presence of air. Due to the porous structure of the charred residue, the protection from it is mainly to reduce the HRR and MLR and retard burning of the material. It is not enough to make the nanocomposite self‐extinguish. Copyright © 2012 John Wiley & Sons, Ltd.     

Fire reaction properties of polystyrene-based nanocomposites using nanosilica and nanoclay as additives in cone calorimeter test

Using nanofiller additives in the polymer matrix to form nanocomposites is a potential way of reducing the flame spread and enhancing flame retardancy of polymeric materials during fire. To understand the fire reaction properties and the relative performance of flame-retardant additives in polymer during well-developed fire, neat polystyrene, polystyrene–silica and polystyrene–nanoclay (MMT) have been tested in a cone calorimeter. The neat polystyrene and the polystyrene nanocomposites have been prepared via an in situ polymerization method. An external heat flux of 50 kW m^?2 was applied in the test, and parameters such as heat release rate, peak heat release rate, time to ignition, smoke toxicity, CO and CO₂ yield have been investigated. Both neat polystyrene and polystyrene nanocomposites have shown the trend of a thermally thick charring polymer in the heat release rate over time data. The nanocomposites had an overall better flame retardancy than the neat polystyrene in terms of lower peak heat release rate, lower average mass loss rate and enhanced char formation. The nanocomposites had also reduced smoke emission with lower CO and CO₂ yield compared to the neat polystyrene. The overall flame retardancy was enhanced as the nanofiller loading was increased for both the nanosilica and MMT nanocomposites.