Suspension Polymerization Of Methyl Methacrylate Research Articles

Preparation and Characterization of Carrot Nanocellulose and Ethylene/Vinyl Acetate Copolymer-Based Green Composites

This study aims to investigate the effect of nanocellulose on the properties and physical foaming of ethylene/vinyl acetate (EVA) copolymer. The nanocellulose is prepared from waste carrot residue using the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation method (CT) and is further modified through suspension polymerization of methyl methacrylate (MMA) monomer (CM). The obtained nanocellulose samples (CT or CM) are added to EVA to create a series of nanocomposites. Moreover, the EVA and CM/EVA composite were further foamed using supercritical carbon dioxide physical foaming. TEM results show that the average diameters of CT and CM are 24.35 ± 3.15 nm and 30.45 ± 1.86 nm, respectively. The analysis of mechanical properties demonstrated that the tensile strength of pure EVA increased from 10.02 MPa to 13.01 MPa with the addition of only 0.2 wt% of CM. Furthermore, the addition of CM to EVA enhanced the melt strength of the polymer, leading to improvements in the physical foaming properties of the material. The results demonstrate that the pore size of the CM/EVA foam material is smaller than that of pure EVA foam. Additionally, the cell density of the CM/EVA foam material can reach 3.23 × 1011 cells/cm3.

Effect of Temperature on Reaction System Stability in Suspension Polymerization of Methyl Methacrylate

Effect of Temperature on Reaction System Stability in Suspension Polymerization of Methyl Methacrylate

Study on preparation and process of poly(MMA‐St) thermally expandablecore‐shellmicrospheres

AbstractThermally expandable microspheres were synthesized by the suspension polymerization of methyl methacrylate (MMA) and styrene (St) in the presence of paraffin blowing agents. The effect of the monomer composition, the initiator, the blowing agent, the polymerization temperature on the morphology and structure of microspheres were studied. The results showed that AIBN initiated the water phase polymerization of MMA to form secondary polymer particles adsorbed on the surface of the microspheres. MMA diffused from the oil phase to the water phase, which accelerated the phase separation and facilitated the formation of core‐shell microspheres. However, LPO could not initiate the water phase polymerization, the phase separation was slow and there was an intermediate state with a porous surface. When the boiling point of the blowing agent was lower than the polymerization temperature, the microspheres were porous and there were a large number of holes on the surface.

Effect of organoclay modifier structure on the viscoelastic and thermal properties of poly(methyl methacrylate)/organoclay nanocomposites

Poly(methyl methacrylate) (PMMA)/clay nanocomposites (NCs) were prepared by suspension polymerization of methyl methacrylate in the presence of two different organoclays (Cloisite 30B, Cloisite 15A) with clay loading ranged from 0.5 to 5 wt%. Increase in molecular weight of the PMMA matrix with addition of the clay was revealed by gel permeation chromatography (GPC) and intrinsic viscosity measurements. As confirmed by X-ray diffraction (XRD), the NCs had an intercalated structure. The organoclays-MMA/PMMA compatibility was investigated by swelling tests and solubility parameter approach. Rheological behavior of PMMA NCs in molten state was analyzed through construction of master curves of complex viscosity, storage, and loss modulus by applying the time–temperature superposition procedure. Melt rheology, scanning electron microscopy (SEM), and UV/Vis spectroscopy results confirmed higher extent of clay dispersion in the NCs with Cloisite 30B. Compared to pure PMMA, all these NCs show increase of glass transition temperature as measured by DSC and improved thermal stability determined by thermogravimetric analysis (TGA). The results obtained by dynamic mechanical analysis showed that the storage modulus of the NCs was higher by incorporation of clay into the PMMA matrix, increasing as the amount of clay increased and that their mechanical performance was significantly enhanced.

Selective solid phase extraction and pre-concentration of Cu(II) ions from aqueous solution using Cu(II)-ion imprinted polymeric beads

A new Cu(II)-ion imprinted polymeric (IIP) beads (∼ 450 μm) were prepared by suspension polymerization of methyl methacrylate (monomer) and ethylene glycol dimethacrylate (crosslinker) in the presence of Cu(II)-picolinic acid (functional ligand) binary complex wherein Cu(II) ion is used as an imprint ion. The imprinted Cu(II) ions were removed from the polymeric matrix using 1 M HCl, thereby creating the cavities for the selective adsorption of Cu(II) ions. For the comparison purpose, control polymeric (CP) beads were similarly prepared without the use of Cu(II) ions. The prepared IIP beads were characterized using different analytical techniques such as scanning electron microscopy, energy dispersive X-ray spectroscopy, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, surface area and pore size distribution. The optimum solution pH was determined to be 5.0 and equilibrium was achieved within 60 min. Nature of eluent, eluent concentration and sample volume were also studied. The synthesized IIP exhibited high selectivity coefficients for the Cu(II)/Ni(II), Cu(II)/Co(II) and Cu(II)/Zn(II) are 26.8, 34.0 and 57.7, respectively. The IIP beads can be used up to seven adsorption/desorption cycles with the recovery not less than 97 %. The detection limit corresponding to three times the standard deviation of the blank was found to be 0.3 μg mL−1.

Study of the features of suspension polymerization of methyl methacrylate in the presence of polymeric surfactants

The molecular weight characteristics of the polymer obtained by suspension polymerization of methyl methacrylate in the presence of polymeric surfactants - (co)polymers of 2-acrylamido-2-methylpropane sulfonic acid, sodium salt of methyl methacrylate copolymer with methacrylic acid and acrylamide copolymer with acrylonitrile and acrylic acid are studied. It was found that the highly dispersed fraction (0.5–2 μm) of polymethyl methacrylate has an increased molecular weight and even at a content less than 1% has a noticeable eff ect on the average molecular weight. It is shown that an eff ective way to reduce the content of polymer particles 0.5–2 μm is the use of a dispersant, in which the colloidal solubility of methyl methacrylate is minimal.

A multiscale CFD-PBM coupled model for the kinetics and liquid–liquid dispersion behavior in a suspension polymerization stirred tank

Suspension polymerization of methyl methacrylate (MMA) has been considered as a liquid–liquid reactive polydispersity system, which involves the complex multiphase flow behavior at multiple time and length scales. The polymerization kinetic characteristics (i.e., gel effect and glass effect) and liquid–liquid dispersion phenomena (i.e., breakage and coalescence of liquid droplets) appearing in this process make the study of suspension polymerization complicate. In this work, a three dimensional (3D) multiscale model including Eulerian–Eulerian two-fluid model, polymerization kinetics model, population balance model (PBM) and some other constitutive models was developed to elaborate those multiscale phenomena in polymerization course. The current model was validated using the reported data in terms of conversion, molecular weight as well as droplet Sauter diameter. The developed model was then employed to investigate the influence of key operating conditions on polymerization kinetic characteristics and liquid–liquid dispersion phenomena. Furthermore, the effects of reactor structure on droplet breakage and coalescence were studied in detail. This simulation work may contribute to the preparation of polymer products and the scaling up of stirred tank polymerization reactors with multiphase flow and multiscale characteristics.

On-Line Dynamic Data Reconciliation in Batch Suspension Polymerizations of Methyl Methacrylate

A phenomenological model was developed to describe the dynamic evolution of the batch suspension polymerization of methyl methacrylate in terms of reactor temperature, pressure, concentrations and molecular properties of the final polymer. Then, the phenomenological model was used as a process constraint in dynamic data reconciliation procedures, which allowed for the successful monitoring of reaction variables in real-time and on-line. The obtained results indicate that heat transfer coefficients change significantly during the reaction time and from batch to batch, exerting a tremendous impact on the process operation. Obtained results also indicate that it can be difficult to attain thermodynamic equilibrium conditions in this system, because of the continuous condensation of evaporated monomer and the large mass transfer resistance offered by the viscous suspended droplets.

Expansion characteristics of expandable styrene/methyl methacrylate copolymer particles: The effects of copolymer molecular weight and particle size

Spherical foamable particles were synthesized by suspension polymerization of methyl methacrylate and styrene in the presence of a blowing agent. When the surrounding temperature was high enough to vaporize the blowing agent and soften the polymer shell, the particles were expanded due to pressure difference across the shell. The effects of initiator and crosslinker concentration on the particle size, average molecular weight, and molecular weight distribution of synthesized copolymer, pentane content and expansion properties (density, residual pentane, and dimensional stability of pre-expanded beads) of expandable particles were investigated. The results showed that the expansion behavior of the particles was dependent on molecular weight of the matrix polymer and size of the synthesized particles. In a constant copolymer molecular weight, the pre-expanded bead density decreased with increasing of particle size whereas it increased with molecular weight in a constant particle size. Moreover, the crosslinker improved dimensional stability of the pre-expanded beads.

Graphene functionalized with poly(vinyl alcohol) as a Pickering stabilizer for suspension polymerization of poly(methyl methacrylate)

Two types of thermally reduced graphenes (TRGs) having different lateral sizes were non-covalently modified with poly(vinyl alcohol) to endow water-dispersibility. The modified TRGs were examined as Pickering stabilizers for the suspension polymerization of methyl methacrylate (MMA). They were effective graphene-based Pickering stabilizers for the system with almost all of the polymerized composite microparticles having a regular spherical shape. The particle size of the composite microparticles was tunable by the size or the amount of modified TRG used as stabilizer. The almost perfect core-shell structure of the composite microparticles effectively enhanced the thermal stability of the core PMMA. In addition, when the core-shell microparticles were compression molded into a monolith, the obtained composite exhibited an ultra-low percolation threshold of electrical conductivity of around 0.04vol%.

Poly(methyl methacrylate)/Graphene Microparticles Having a Core/Shell Structure Prepared with Carboxylated Graphene as a Pickering Stabilizer

Two kinds of carboxylated thermally reduced graphenes (carboxylated TRGs) with different lateral sizes are examined as a Pickering stabilizer in the suspension polymerization of methyl methacrylate. The size and the shape of the prepared composite particles are irregular due to agglomeration, more evidently when the larger carboxylated TRG is used. In addition, carboxylated TRG is distributed not only on the surface but also inside the composite particles. It indicates that the carboxylated TRG alone is not a stable Pickering agent. However, a very small dosage of acrylic acid remedies all these issues because acrylic acid interacts with carboxylated TRG and synergizes the stabilizing effect. The compression molded composite of the core/shell poly(methyl methacrylate)/carboxylated TRG particles exhibits a very low percolation threshold of electrical conductivity of 0.03 vol%. It demonstrates that the carboxylated TRG shells of the composite particles effectively form a segregated conductive network throughout the composite. image

Particle Size and Particle Size Distribution of Suspension Polymerization of Methyl Methacrylate in Baffled Tank Reactor

Particle Size and Particle Size Distribution of Suspension Polymerization of Methyl Methacrylate in Baffled Tank Reactor

Real time monitoring of the quiescent suspension polymerization of methyl methacrylate in microreactors—Part 1. A kinetic study by Raman spectroscopy and evolution of droplet size

This paper presents an experimental study on the polymerization of droplets of methyl methacrylate (MMA) in quiescent state using microreactors. The reaction kinetics was monitored by Raman spectroscopy, while the images of MMA droplets image were captured by CCD (charge-coupled device) camera within a microcapillary. Different experimental recipes were proposed with commercial initiators in order to compare the system performance with two types of initiators: monofunctional and bifunctional peroxides. It is shown in this paper that the Raman technique is able to monitor the reaction kinetics at different conditions. For the first time in the open literature it was possible to identify the evolution of the monomer droplets during polymerization to high conversions (>90%) in quiescent state. In addition, it was possible to identify three different stages during the polymerization reactions of MMA. Finally, it is shown that the dispersities (M¯w/M¯n) obtained with the bifunctional initiator were lower than 2, while the dispersities obtained with the monofunctional initiator were greater than 2.

Removal of Bisphenol A from Aqueous Solution by Molecularly Imprinted Polymers

Uniformly sized polymeric molecularly imprinted microspheres have been synthesized by membrane emulsification and suspension polymerization of methyl methacrylate and ethyl glycol dimethacrylate in the presence of bisphenol A as a template. At the beginning the best monomer compositions were selected by bulk polymerization of eight different mixtures of monomer and crosslinking agent. For the selected compositions that had the highest affinity to bisphenol A, a two-step process composed of membrane emulsification and suspension polymerization was used. Materials prepared by the two-step process showed the higher efficiency to the bisphenol A removal than their analogues prepared by bulk polymerization. The best material was synthesized from a mixture of methyl methacrylate and ethylene glycol dimethacrylate as 4:6 in the presence of n-octane as a solvent, and with 3 wt.% of bisphenol A. The logKBPA value for this sample was 4.9. The experimental sorption isotherms were fitted by Scatchard plots and heterogeneity of the binding sites was determined. The selectivity of the sorbents to other phenols was demonstrated.

Suspension polymerization of methyl methacrylate stabilized solely by palygorskite nano fibers

A kind of fibrous clay, palygorskite (PAL), was used as the sole stabilizer in suspension polymerization without the using of any other stabilizer usually used, especially polymeric stabilizers. In order to improve the compatibility with the organic monomer, PAL nano fibers were organically modified with silane coupling agent methacryloxypropyltrimethoxysilane (MPS). Transmission electron microscopy (TEM) and Fourier-transform infrared (FTIR) spectroscopy results show that the hydrolyzed MPS was attached onto PAL surface through Si-O-Si bonds formation without morphology change of PAL. At a loading amount of PAL to monomer as low as 0.36 wt%, effective stabilization could be achieved. After suspension polymerization, spherical poly(methyl methacrylate) (PMMA) particles were obtained. Scanning electron microscopy (SEM) analysis on both the outer surface and the inner cracked surface of the spherical PMMA particles indicates that the PAL particles reside on the surface of the PMMA spheres. The densely stacked PAL together with attached silane coupling agent stabilized the droplets throughout the suspension polymerization.

Facile Iron‐Mediated Dispersant‐Free Suspension Polymerization of Methyl Methacrylate via Reverse ATRP in Water

An iron-mediated reverse ATRP of methyl methacrylate (MMA) is successfully carried out in water in the absence of any dispersants, using a water-soluble 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V-50) as the initiator and the stabilizer, and using an oil-soluble N,N-butyldithiocarbamate ferrum (Fe(S2 CN(C4 H9 )2 )3 ) as the catalyst without adding any additional ligands. Micron-sized PMMA particles with UV light-sensitive -S2 CN(C4 H9 )2 end group are obtained, and monomer droplet nucleation and suspension polymerization mechanism are proposed. Polymerization results demonstrated typical "living"/controlled characteristics of ATRP: first-order polymerization kinetics, linear increase of molecular weights with monomer conversion and narrow molecular weight distributions for the resultant PMMA particles. NMR spectroscopy and chain-extension experiments under UV light irradiation confirm the attachment and livingness of UV light-sensitive -S2 CN(C4 H9 )2 group in the chain end.

A comparative study of polymethylmethacrylate/cellulose nanocomposites prepared by in situ polymerization and ex situ dispersion techniques

Polymethylmethacrylate/cellulose nanocomposites were prepared by in situ polymerization and ex situ dispersion techniques with 10 wt% loading of cellulose nanoparticles. Cellulose nanoparticles were prepared from jute fibers by acid hydrolysis. The suspension polymerization of methylmethacrylate was carried out in presence of cellulose nanoparticles, which were dispersed in water medium and in situ polymethylmethacrylate/cellulose nanocomposite granules were formed. These granules were dissolved in chloroform, sonicated and films were prepared by solution casting method (IPC). Polymethylmethacrylate granules were prepared by similar suspension polymerization process and made into films by solution casting method. Another set of polymethylmethacrylate/cellulose nanocomposite films were prepared by dispersing nanocellulose powder (10 wt%) in polymethylmethacrylate solution and casting into films (EPC). The unreinforced polymethylmethacrylate and polymethylmethacrylate extracted from IPC films were subjected to size exclusion chromatography and nuclear magnetic resonance study. The average molecular weights of neat polymethylmethacrylate and polymethylmethacrylate from IPC were quite close, but the ‘dispersity’ was slightly higher in IPC than that in neat polymethylmethacrylate. Fourier transform infrared spectroscopy revealed some shifts in EPC. X-ray diffraction study showed a similar nature of X-ray diffraction curves in all the samples. Transmission electron microscopy of IPC and EPC showed a better dispersion of fillers and formation of a network structure in IPC, whereas in EPC, the fillers were agglomerated. Surface morphology of the films was examined by field emission scanning electron microscopy and atomic force microscopy. IPC exhibited a much smoother surface compared to that of EPC indicating a more homogeneous dispersion of fillers. IPC showed a higher modulus of elasticity compared to PMMA and EPC. Differential scanning calorimetry showed a shift of glass transition temperature to a higher one (125°C) in IPC compared to that of polymethylmethacrylate (118°C). Thermogravimetric analysis was done to study the thermal degradation behavior of the composites.

Development of a comprehensive mathematical model for free radical suspension polymerization of methyl methacrylate

In this work a detailed mathematical model for free radical suspension polymerization of methyl methacrylate (MMA) in water is developed. This model is based on sound principles such as the free volume theory to account for the diffusion limited reactions in suspension polymerization. Additionally, the complex polymerization kinetics process of the aqueous suspension polymerization of MMA is studied as a one-dimensional numerical experiment. For this purpose, the polymerization process is modeled as a moving boundary mass transfer problem coupled with polymerization reactions. The Galerkin finite element method is used to simultaneously solve the nonlinear governing equations. The model predictions for conversion and average molecular weights vs. time were found to be in close agreement with laboratory data. It is believed that this work, as it provides fundamental understanding of the process, it might contribute to a more rational design of polymerization reactors. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Droplets Size Distribution Analysis in Suspension Polymerization of Methyl Methacrylate.

Droplets Size Distribution Analysis in Suspension Polymerization of Methyl Methacrylate.

Synthesis of calcium carbonate vaterite crystals and their effect on stabilization of suspension polymerization of MMA

Spherical calcium carbonate vaterite crystals were synthesized and the effect of them on stabilization of suspension polymerization of methyl methacrylate was investigated. Suspension polymerization of methyl methacrylate could be stabilized with calcium carbonate vaterite crystals and sodium dodecylbenzene sulfonate of the concentrations from 25 to 100 ppm. Poly(methyl methacrylate) beads coated with spherical calcium carbonate vaterite crystals were prepared. With an increase in the concentration of sodium dodecylbenzene sulfonate from 25 to 100 ppm, the amount of calcium carbonate vaterite crystals adhered on the surface of poly methyl methacrylate bead increased and the mean diameters of the polymer beads decreased.