Thermal Stability Of PMMA Research Articles

Synthesis and properties of transparent PMMA/cellulose nanocomposites prepared by in situ polymerization in green solvent

AbstractIn order to contribute to the demanded sustainability transparent poly(methyl methacrylate) (PMMA) composites with cellulose nanocrystals (CNC) up to high shares of 50 wt% were prepared by in situ radical polymerization in green solvent Cyrene. The weight average molecular weights of PMMA were in the range from 144,000 to 160,000 g mol−1 and the dispersity was in the range of 1.49 to 1.89 with high conversion of monomer to polymer. The DSC thermal analysis showed that the glass transition temperature of pure PMMA was at 99°C while in composites increased from 103°C up to 129°C with the increase of CNC from 1 wt% to 50 wt%. TGA shows that the addition of CNC does not have a significant effect on the thermal stability of PMMA. In composites Young's modulus increases with the increasing CNC ratio and composites with 50 wt% of CNC showed more than twice the modulus of the PMMA matrix. The SEM images indicate uniform distribution of CNC in polymer matrix. The transparent and semitransparent PMMA/cellulose composites of improved sustainability with higher modulus of elasticity and glass transition temperature can be used as lightweight materials for a wide range of technical and everyday applications as well as optical lenses or acoustic lenses for ultrasound transducers and other devices.Highlights Cellulose nanocrystals/PMMA composites fabricated by a green in situ process. Synthesized PMMA matrices have high molecular weights. Improved elastic modulus and glass transition temperature were achieved. Prioritizing eco‐friendly chemicals for a greener production approach.

Highly transparent and flexible surface modified chitin nanofibers reinforced poly (methyl methacrylate) nanocomposites: Mechanical, thermal and optical studies

Surface modified chitin nanofibers (SMCNFs) were easily prepared by reacting chitin powder with dodecenyl succinic anhydride (DDSA) and mechanical treatment. The resulted SMCNFs were homogenously dispersed in a series of organic solvents since more hydrophobic group was introduced on the surface of chitin nanofibers. Poly (methyl methacrylate) (PMMA)/SMCNFs nanocomposite films were prepared by simple solution casting method. The homogenous dispersion of the SMCNFs in the PMMA matrix was facilitated, due to the presence of hydrogen bonding and hydrophobic interactions between the nanofillers and the PMMA matrix. Thus, PMMA/SMCNFs nanocomposite films shown high optical transparency, which were nearly the same as the transmittance of the neat PMMA film. Tensile testing results revealed that, inclusion of SMCNFs in the PMMA matrix yielding a more fracture strain and tougher films than the neat PMMA film. Thermal analysis of the neat PMMA and nanocomposite films demonstrated that, the thermal stability of PMMA was significantly enhanced upon inclusion of SMCNFs. The remarkable reinforcement effect of SMCNFs in enhancing the mechanical and thermal properties of PMMA without altering its transparency was resulted from their crystallinity, high aspect ratio, and homogenous dispersibility in the DMF solvent and PMMA polymer matrix.

Poly(methyl methacrylate) nanocomposites involving aromatic diboronic acid

In this work, poly(methyl methacrylate), PMMA, composites involving various amounts of aromatic diboronic acid, BDBA, in the absence and presence of organically modified montmorillonite, Cloisite 30B, C30B, were prepared and characterized by X-ray diffraction, transmission electron microscopy, thermogravimetry, and direct pyrolysis mass spectrometry analyses. Morphologic analyses indicated homogenous dispersion of additives in PMMA matrix. Increase in thermal stability of PMMA was observed as the amount of BDBA incorporated into polymer matrix was increased. Strong evidences for interactions between the hydroxyl groups of diboronic acid and the ester groups of PMMA were detected. The increase in thermal stability was associated with these reactions producing also a cross-linked structure.

Water-dispersible graphene designed as a Pickering stabilizer for the suspension polymerization of poly(methyl methacrylate)/graphene core–shell microsphere exhibiting ultra-low percolation threshold of electrical conductivity

The microsphere of poly(methyl methacrylate) (PMMA)/graphene composite, having a core–shell structure, is effectively prepared by Pickering suspension polymerization using a water-dispersible sulfonated graphene alone as a Pickering stabilizer. This is the first case where a graphene is designed as a Pickering stabilizer for suspension polymerization. The sulfonated graphene is prepared using a novel covalent modification method that utilizes the epoxide groups on graphene, which are the inherent defects of thermally reduced graphene, to react with potassium 2-aminoethanesulfonate, without any additional damage to the intrinsic conjugated sp2 carbon network of the graphene. The size of the microsphere is tunable by the amount of graphene from several tens to several hundreds of micrometers. The thermal stability of PMMA at the core is substantially improved by the thermally stable graphene shell enclosing it. The compression molded composite of the microspheres displays an excellent electrical conductivity of 15.7 S m−1 at a graphene content of 5.33 phr (2.78 vol.%) and an ultra-low percolation threshold of 0.04 phr (0.02 vol.%), which is the lowest value ever reported for polymer/graphene composites, because the graphene shells form a well-defined, three-dimensional conductive graphene network throughout the composite.

Study on the PMMA/GO nanocomposites with good thermal stability prepared by in situ Pickering emulsion polymerization

Graphene oxide (GO) is used as a stabilizer in the Pickering emulsion polymerization of methyl methacrylate (MMA) to prepare PMMA/GO nanocomposites. Transmission electron microscope studies of the emulsion polymerization products showed that the average diameter of nanocomposite particles was about 150 nm, the transparent GO flakes covered the surface of the particles, and were well dispersed in polymer matrix. The influence of GO on the thermal stability of PMMA was investigated by thermogravimetry analysis and differential scanning calorimetry. The results showed that the thermal stability and the glass transition temperature (T g) of PMMA/GO nanocomposites were improved obviously compared with PMMA. The apparent activation energy (E a) for the degradation process of PMMA/GO nanocomposites was evaluated by Kissinger method, which indicated that their E a s were much higher than those of PMMA both in nitrogen and air atmosphere.

Synthesis and Thermal Characterizations of Pmma Nanocomposite Functionalized by Polyhedral Oligomeric Silsesquioxane

A novel polyhedral oligomeric silsesquioxane/polymethyl methacrylate (POSS/ PMMA) hybrid nanocomposite was synthesized by using potassium persulfate and sodium dodecyl sulfate as the initiator and emulsifier, respectively. The structures of prepared nanocomposites were characterized with X-ray photoelectron spectroscopy, laser particle size analysis, and X-ray diffraction. The thermal properties of the POSS/PMMA nanocomposites were studied by differential scanning calorimetry, and thermogravimetric analysis. The results indicate that POSS could be incorporated into the PMMA matrix at molecular lever and the incorporation of POSS molecules can improve the thermal stability of PMMA. [Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the following free supplemental files: Additional figures]

Thermal Stability and Degradation Kinetics of Poly(Methyl Methacrylate)/Sepiolite Nanocomposites by Direct Melt Compounding

Poly(methyl methacrylate) (PMMA) nanocomposites based on sepiolite modified with trimethyl hydrogenated tallow amine by an adsorption process were prepared by melt compounding using a corotating twin screw extruder. The morphology and dispersion of sepiolite in the PMMA were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and the activation energies were investigated by thermogravimetric analysis/differential thermogravimetric (TGA/DTG). The XRD and TEM results show that the sepiolite was dispersed homogeneously in the PMMA matrix at a nanometer scale. The TGA analysis revealed that the addition of sepiolite improved the thermal stability of PMMA. The apparent activation energies were calculated by the method of Flynn–Wall–Ozawa in nitrogen at four different heating rates, showing that sepiolite increased the apparent activation energies by about 20 kJ/mol within the degree of conversion (α) of 0.35–0.9, as compared with the reference PMMA sample.

Kevlar oligomer functionalized graphene for polymer composites

Kevlar oligomer functionalized graphene (FGS) was prepared by simple grafting of amino-terminated Kevlar oligomer on graphene oxide (GO) followed by reducing with hydrazine hydrate. The incorporation of FGS shows pronounced effect on the host polymers. High-level reinforcement of both PMMA and PI is observed with low content of FGS (≤0.2 wt %), in this lower loading range, the tensile modulus and strength of composites increase almost linearly as a function of the adding amount of FGS. But no further improvement is obtained as the content of FGS further increased (>0.2 wt %). The mechanism under the reinforcement effect against the FGS loadings is discussed based on the morphological characterizations of the composites. The thermal properties of the composites were also investigated. The glass transition temperature and thermal stability of PMMA were dramatically increased even with the addition of only a small amount of FGS.

Chlorinated thermal stabilizer for optically clear PMMA

Optically clear poly(methyl methacrylate) (PMMA) blends with HET‐EG oligoester (synthesized by condensation of chlorendic acid with ethylene glycol) at six different compositions were prepared by bulk polymerization. The effect of HET‐EG in the PMMA matrix on the optical clarity of PMMA blend was measured using ultraviolet‐visible spectroscopic study. The thermal stability of PMMA blends was investigated using differential scanning calorimetric (DSC) and thermogravimetric (TG) analyses. The parameters to deduce the thermal stability of pure PMMA and PMMA blends were calculated from DSC and TG results. The thermal stability of PMMA was found to increase effectively by loading 5% of HET‐EG oligoester without marring optical clarity. The probable physical and chemical actions of HET‐EG oligoester on the thermal stability of PMMA are discussed. Copyright © 2011 John Wiley & Sons, Ltd.

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–gel 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 (5–30 °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.

Polyol mediated nano size zinc oxide and nanocomposites with poly(methyl methacrylate)

Organophilic nano ZnO particles have been synthesized in various diols (ethylene glycol - EG, 1,2 propane diol - PD, 1,4 butane diol - BD and tetra(ethylene glycol) - TEG) in the presence of p-toluenesulfonic acid, p-TsOH, as an end capping agent. The addition of p-TsOH reduces the ZnO particle size and increases its crystallite size. With increasing diol main chain length the ZnO particle size increases (EG (32 nm) < PD (33 nm) < BD (72 nm) < TEG (86 nm)). Using the as- synthesized and unmodified ZnO nanocomposites with poly(methyl methacrylate), PMMA, matrix have been prepared by the in-situ bulk polymerization of methyl methacrylate, MMA. The addition of surface modifiers is avoided which is an advantage for the application since they can influence other properties of the material. ZnO particles, especially those with smaller particle sizes (EG - 32 nm, PD - 33 nm) showed enhanced effect on the thermal stability of PMMA, ultraviolet, UV, absorption and transparency for visible light. Transparent materials with high UV absorption and with enhanced resist- ance to sunlight were obtained by optimizing the nanocomposite preparation procedure using ZnO particles of about 30 nm size in concentrations between 0.05 and 0.1 wt%. The reported nanocomposite preparation procedure is compatible with the industrial process of PMMA sheet production.

Studies on the Morphology and Properties of PMMA-Organoclay Nanocomposites with Reference to the Manufacturing Techniques

The morphology and properties of PMMA-clay (1.5 phr) nanocomposites prepared by three different manufacturing techniques viz., solution mixing, melt mixing, and suspension polymerization, have been investigated. XRD study revealed that for particular clay loading, the extent of clay intercalation by the PMMA chains depend on the manufacturing techniques. The glass transition temperature of PMMA increased significantly in the in-situ polymerized PMMA-clay nanocomposites. TGA results revealed nearly 14% improvement in thermal stability of PMMA for in-situ polymerized PMMA-clay nanocomposite. In both the glassy and rubbery regions, the storage moduli of all the nanocomposites were higher than that of neat PMMA.

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

AbstractNanozirconia (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 (Ea) in TGA both in nitrogen and air were investigated. The Kissinger method was used to determine Ea for the degradation of pure PMMA and the PMMA/nano‐ZrO2 nanocomposites. The kinetic results show that the values of Ea for the degradation of the nanocomposites were higher than that of pure PMMA in air. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Use of Pristine Clay Platelets as a Suspension Stabilizer for the Synthesis of Poly(methyl methacrylate)/Clay Nanocomposites

AbstractThe role of Na+‐mmt platelets as a stabilizer during the suspension polymerization of MMA is described. The addition of a small amount of Na+‐mmt into the system without suspension stabilizer results in the formation of spherical beads of PMMA/Na+‐mmt nanocomposites with uniform sizes, whereas in the presence of o‐mmt, it resulted in the formation of PMMA/o‐mmt composite clusters. FT‐IR spectroscopy reveals a strong interaction between the PMMA carbonyl groups with the clay surface in the PMMA/Na+‐mmt nanocomposite. DSC results indicate a significant increase in the glass transition temperature of PMMA in the PMMA/Na+‐mmt nanocomposite as compared to that of the PMMA/o‐mmt nanocomposite. The thermal stability of PMMA is also increased in the case of the PMMA/Na+‐mmt nanocomposite.magnified image

Transparent PMMA/ZnO nanocomposite films based on colloidal ZnO quantumdots

Colloidal zinc oxide (ZnO) quantum dots (QDs) with a uniform particle size of around 5 nmhave been synthesized, purified and blended with polymethylmethacrylate (PMMA)by solution mixing to prepare PMMA/ZnO nanocomposite films. The structureand morphology of ZnO QDs and PMMA/ZnO nanocomposite films have beencharacterized using high-resolution transmission electron microscopy. The PMMA/ZnOnanocomposite films prepared are highly transparent. The UV–vis spectra andthermogravitational analysis results show that a small amount of colloidal ZnO QDs(<1 wt%) without further surface modification can greatly improve the thermal stability ofPMMA along with UV-shielding capability.

Microstructural Characterisation and Properties Evaluation of Poly (methyl methacrylate-co-ester)s

The present work provides detailed copolymerization behavior of methyl methacrylate (MMA) with 2-methylene-1,3-dioxepane (MDP), a cyclic ketene acetal under conventional free radical polymerization conditions at 120 °C. An in-sight to the microstructure of the homo- and co-polymers is also made available using 1D and 2D NMR spectroscopic techniques. For the first time we showed the formation of crystalline degradable aliphatic polyester, homo poly (2-methylene-1,3-dioxepane) (PMDP) with reduced branches using radical-ring-opening-polymerisation. The copolymerization brought degradability and many other new properties to the poly (methyl methacrylate) (PMMA) vinyl polymer. Various degradable materials based on MMA and 2-methylene-1,3-dioxepane (poly (MMA-co-ester)s) containing varied amounts of ester linkages ranging from amorphous to crystalline and with different glass transition temperatures are generated. The presence of very low fraction of the ester linkages (about 10 mol %) could led to a significant increase in the thermal stability of PMMA. These materials are shown to have heat-shrinkable-shape-memory properties also.

Preparation and characterization of a PMMA/Ce(OH) 3, Pr 2O 3/graphite nanosheet composite

An easy process for the synthesis of poly(methyl methacrylate)/Ce(OH) 3, Pr 2O 3/graphite nanosheet (PMMA/Ce(OH) 3, Pr 2O 3/NanoG) composite was developed. Graphite nanosheets (NanoG) were prepared by treating the expanded graphite with sonication in aqueous alcohol solution. The PMMA/Ce(OH) 3, Pr 2O 3/NanoG composites were prepared via in situ polymerization of MMA monomer in the presence of graphite nanosheets and Ce(OH) 3, Pr 2O 3 through reverse micelle template, in which the methyl methacrylate was designated as the oily phase. The composites were then dispersed with chloroform and coated on glass slides to form films. Scanning and transmission electron microscopy were used to characterize the structure and dispersion of the graphite nanosheets and the composites. The results showed that the high-aspect-ratio structure of the nanosheets played an important role in forming a conducting network in the PMMA matrix. From thermogravimetric analysis, the introduction of graphite nanosheets and inorganic nanopartices exhibited a beneficial effect on the thermal stability of PMMA.

Study of poly(methyl methacrylate) film doped with inclusion complex of p‐tert‐butylcalix[8]arene

AbstractSeven kinds of poly(methyl methacrylate) (PMMA) films doped with [60]fullerene or its inclusion complex of p‐tert‐butylcalix[8]arene were prepared and characterized by FTIR, UV‐vis, TG, and DSC. It was found that the thermal stability of PMMA is much improved by doping with the inclusion complex in comparison with [60]fullerene itself, that is, the inclusion complex retards the thermal depolymerization of PMMA very effectively. The influence of incorporating active carbon powder or calix[8]arene on the thermal stability of PMMA was also investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1549–1552, 2002

Review on Chemical Reactions of Burning Poly(methyl methacrylate) PMMA

Chemical reactions of burning Poly(methyl methacrylate) (PMMA) are reviewed in this paper although kinetics of thermal decomposition are believed to be fairly simple. Basically, there are three stages in the combustion of PMMA. Firstly, PMMA decomposes to produce monomer methyl methacrylate (MMA). Secondly, monomer MMA decomposes to generate small gaseous molecules that are usually combustible. Finally, these small molecules undergo combustion. Recent studies on the thermal decomposition kinetics and thermal stability of PMMA are also introduced. Results are useful for understanding the heat released of burning PMMA per unit mass of oxygen. Finally, the effects of additives on thermal decomposition are also discussed.

Controlled Radical Polymerization of (Meth)acrylates by ATRP with NiBr2(PPh3)2 as Catalyst

NiBr2(PPh3)2 has been found to be an efficient catalyst for the ATRP of methyl methacrylate (MMA) and n-butyl acrylate (n-BuA) initiated by an alkyl halide in the absence of any activator (e.g., Lewis acid) at 85 °C. The molecular weight distribution of the poly(meth)acrylates is narrow (Mw/Mn = 1.1−1.4). However, some side reactions (more likely coupling reactions) are observed at high monomer conversions in the case of n-BuA. An excess of PPh3 has proved to increase the polymerization rate of MMA while preserving the control of the molecular parameters. When the catalyst/initiator molar ratio is too small (e.g., 0.05), the polymerization rate decreases, the polydispersity increases, and the initiation is less efficient. α-Acid and α-hydroxyl end groups have been successfully attached to the chains by using functional initiators, such as 2-bromo-2-methylpropionic acid and 2,2‘,2‘ ‘-tribromoethanol. Reactivity ratios for the MMA/n-BuA comonomer pair have been measured and found to be close to the values observed for a conventional free-radical polymerization. Diethyl meso-2,5-dibromoadipate has been used as a difunctional initiator for the n-BuA polymerization, leading to α,ω-bromo-poly(n-BuA) of narrow molecular weight distribution. Finally, the thermal stability of PMMA is consistent with the lack of termination reactions, while Tg is as high as 125 °C.