Suspension Polymerization Process Research Articles

Modeling and optimization of a seeded suspension polymerization process

A mathematical model is developed and validated for a seeded suspension polymerization process that manufactures polystyrene beads starting from pretreated polyolefin seeds. For the manufacture of this specialty product, we focus on prediction of the dynamics of particle growth, polymerization rate and particle average molecular weight. Particular emphasis is placed on acquisition of reliable parameters which must be estimated from available analytical measurements of the product. A hybrid approach is proposed for parameter subset selection and estimation. Excellent agreement is obtained with experimental results for different product grades. The monomer feeding rate, which is a key controlling factor of bead properties, is determined based on the proposed model and an optimum semi-batch feeding policy is determined. This improved policy is also implemented and validated by pilot plant experiments.

Improvement of the thermal behaviour of gypsum blocks by the incorporation of microcapsules containing PCMS obtained by suspension polymerization with an optimal core/coating mass ratio

Abstract The feasibility of incorporating microcapsules containing Phase Change Materials (PCMs), previously obtained by a suspension polymerization process, in gypsum wallboards to increase the wall energy storage capacity was studied. Firstly, the energy storage capacity of the resulting microcapsules and the microencapsulation efficiency was maximized by studying the influence of the synthesis variable core/coating mass ratio on the suspension polymerization process. Results indicate that the higher paraffin wax to styrene monomer mass ratio, the lower microencapsulation efficiency. A mass ratio of Rubitherm® RT27 to styrene monomer equal 1.5 allowed to obtain microcapsules with the highest energy storage capacity and a good microencapsulation efficiency. It was also observed that the energy storage capacity is dependent on the particle size; the maximum capacity was obtained for a particle size of 500 μm. Finally, the thermal behaviour of three gypsum wallboards one without PCMs and the others doped with 4.7% and 7.5% by weight of microcapsules containing Rubitherm® RT27 at the optimal core/coating mass ratio was studied. Results showed that the higher the amount of microcapsules containing PCMs incorporated to the gypsum wallboard, the lower or higher the external wall temperature for heating or cooling process, respectively. Besides, the incorporation of the microcapsules to the wall increased the time required to achieve the final steady state, verifying that the material insulation capacity was enhanced by increasing PCMs content in the wall.

Compatibility studies with blends based on poly(n-butyl methacrylate) and polyacrylonitrile

In this study, poly(n-butyl methacrylate) (PBMA) was prepared by a suspension polymerization process, and blending with polyacrylonitrile (PAN) in N,N-dimethyl acetamide to prepare PAN/PBMA blends in various proportions. Hansen's three dimensional solubility parameters of PAN and PBMA were calculated approximately through the contributions of the structural groups. The compatibility in these blend systems was studied with theoretical calculations as well as experimental measurements. Viscometric methods, Fourier transform infrared spectroscopy, dynamic mechanical analysis, scanning electron microscopy, and thermogravimetric analysis were used for this investigation. All the results showed that a partial compatibility existed in PAN/PBMA blend system, which may be due to the intermolecular interactions between the two polymers. And, the adsorption experiment results showed that the addition of PBMA contributed to the enhancing adsorptive properties of blend fibers, which lays the foundation for further studying PAN/PBMA blend fibers with adsorptive function. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Expanded Core/Shell Poly(vinyl acetate)/Poly(vinyl alcohol) Particles for Embolization

AbstractAn improvement to a previously published suspension polymerization process for the production of spherical core/shell PVAc/PVA particles is described. To increase the settling time of the beads in the suspension, an expansion stage was introduced. The core/shell structure was obtained through the partial hydrolysis of the PVAc. The particle density was manipulated through addition of a solvent during the suspension polymerization stage and posterior expansion of the polymer beads obtained at the end of the process. This technique allows for effective reduction of the density of the final polymer beads. The expansion stage exerts also a beneficial effect on particle drying, avoiding particle aggregation during post‐polymerization processing of the polymer beads.magnified image

Platinum-Doped TiO2/Magnetic Poly(methyl methacrylate) Microspheres as a Novel Photocatalyst

The study focuses on the characterization of platinum-doped titanium dioxide-coated magnetic poly(methyl methacrylate) (Pt-TiO2/mPMMA) microspheres as a novel photocatalyst. The Pt-TiO2/mPMMA microspheres were prepared by a modified suspension polymerization process, followed by titania-coating and Pt-doping. The Pt-TiO2/mPMMA microspheres were synthesized with various Pt-doping levels in the range of 0.6−1.5 wt % TiO2 for comparison. The morphology, composition, Pt-doping content, and magnetic properties of the Pt-TiO2/mPMMA microspheres were characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and superconducting quantum interference device. As a result, the superparamagnetic Pt-TiO2/mPMMA microspheres were successfully synthesized with particle sizes of 5−11 μm. The magnetite and TiO2 contents of the Pt-TiO2/mPMMA microspheres were estimated as 7.69 and 16.7 wt %, respectively, while the ...

Initiator efficiency modeling for vinyl chloride suspension polymerization

A unified methodology is developed to calculate the fraction of initiator derived radicals that initiates the polymerization, i.e. the initiator efficiency, as a function of polymerization time and polymerization conditions. In the presented approach the most important reactions that initiator derived radicals undergo are taken into account. All involved parameters have a clear physical and fundamental meaning and no adjustment to experimental data is required. The presented methodology is applied to diacyl peroxide initiators that are commonly used in industrial vinyl chloride suspension polymerization processes: dodecanoyl peroxide and benzoyl peroxide. Validation is performed by comparing calculated and experimental data for the monomer conversion and averages of the molar mass distribution within a polymerization temperature range of 323–333 K and an initiator concentration range of 0.26–4.2 wt% based on the monomer.

Boc- l-tryptophan imprinted polymeric microparticles for bioanalytical applications

Molecularly imprinted polymer (MIP) microparticles with good chromatographic characteristics were synthesized via the suspension polymerization process in a single preparative step. Initially, the effects of process parameters (i.e., porogen concentration, polymerization temperature, types and concentrations of functional monomer and cross-linker) on the particle size distribution and particle morphology were experimentally investigated. Subsequently, various MIP microparticles were synthesized in the presence of an amino acid derivative (i.e., boc- l-tryptophan), acting as template molecule. Batch-wise guest binding experiments were then performed to determine the rebinding capacity of the synthesized MIP microparticles towards the template molecule. Competitive binding experiments were also carried out with boc- d-tryptophan (i.e., the enantiomer of boc- l-tryptophan) to assess the selectivity of the imprinted polymer microparticles towards the two enantiomers. Finally, a quantitative description of the experimentally measured rebinding isotherms was obtained using the well-known Freundlich–Langmuir models. The present results clearly demonstrate the potential application of the synthesized MIP microparticles for bioanalytical separation of peptides and proteins since the amino acid templates employed in this study are the building units of larger biomolecules.

Preparation of phase change materials microcapsules by using PMMA network‐silica hybrid shell via sol‐gel process

AbstractEncapsulation of phase change materials (PCM) using a poly(methyl methacrylate) network‐silica hybrid as the shell material has been developed. n‐Octadecane melted at 28°C was used as PCM. Based on the suspension polymerization process, the microcapsules were prepared successfully by mixing and by the reaction of ethylene glycol dimethacrylate with precopolymer solution with tetraethoxysilane (TEOS), whose resultant microcapsules had higher latent heat (ΔH = 151 J/g) than those without TEOS (ΔH = 88.3 J/g). The average size of the PCM microcapsules was about 10 μm. The silica content, n‐octadecane content, and latent heat of microcapsules were changed with varying ageing conditions, ageing time, and temperature. The highest amount of latent heat (ΔH = 178.9 J/g) and n‐octadecane content (73.3%) of the microcapsule were obtained when the inorganic/organic ratio of the microcapsule was 5%. It was difficult to increase n‐octadecane content (74% to 55.7–67.9%) and latent heat (180.5 J/g to 135.9–165.7 J/g) of the microcapsules by introducing different functional groups of coupling agents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Influence of processing factors on flexural strength of C(f)/PMMA–PMA composites

Polyacrylonitrile based carbon fibre reinforced polymethyl methacrylate–polymethyl acrylate (PMMA–PMA) composites [C(f)/PMMA–PMA] were prepared by a suspension polymerisation process. The effects of the ratio of water/oil, reaction temperatures and fiber mass fraction on the flexural strength of the composites were particularly investigated. The microstructures of the prepared composites were characterised by SEM analyses. The flexural strength was tested by the universal testing machine. Results show that the flexural strength of the composites reaches the optimum value when the water/oil ratio=3:1. With increasing reaction temperature, the flexural strength of C(f)/PMMA–PMA composites increases to maximum and then decreases. With increasing carbon fibre mass fraction, the microstructure of the fractured surfaces changes from smooth to crepe-like, which infers that the toughness of the composites is improved.

Preparation of ZrO2(f)/PMMA-PMA Composites by a Suspension Polymerization Process

Yttria stabled zirconia fiber reinforced polymethyl methacrylate-polymethyl acrylate (PMMAPMA) composites (ZrO2(f)/PMMA-PMA) were prepared by a suspension polymerization method. The effects of MMA/MA volume ratio, initiator and fiber mass ratio on the mechanical properties of the composites were investigated. Results showed that the flexural strength of the composites reaches the optimum value when the volume ratio of methyl methacrylate /methyl acrylate (MMA/MA) = 9/1. With the increase of benzoyl peroxide (BPO) mass ratio, the flexural strength of ZrO2(f)/PMMA-PMA composites increases to maximum and then decreases. With the increase of ZrO2 fiber mass ratio, the microstructure of the fractured surfaces changes from smooth to crapy, implying that the toughness of the composites is improved.

Reaction Inhibition as a Method for Preventing Thermal Runaway in Industrial Processes

AbstractSummary: In this work inhibitors were used to prevent runaway reactions during methylmethacrylate suspension polymerization processes. The main problem that may more frequently occur in chemical reactors, carrying out free radical polymerization reactions, is the loss of temperature control. The addition of an inhibitor during polymerization processes can be considered as a good method to stop or at the least slow down the reaction. In this work two inhibitors were used: hydroquinone and 1,4‐benzoquinone in a series of polymerization experiments. In order to identify situations that can lead to a runaway reaction, an early warning detection system based on the divergence criterion was used. When this system signalled an alarm, small amounts of inhibitor were added to the reaction mixture. The results showed that hydroquinone and 1,4‐benzoquinone behave slightly differently and the reactor temperature can be kept within safe limits.

Use of Polymer Nanoparticles as Functional Nano-Absorbents for Low-Molecular Weight Hydrophobic Pollutants

To use amphiphilic polymer nanoparticles as a new nano-absorbent for improving environmental process, urethane acrylate nonionomer (UAN) chain having hydrophobic polypropylene oxide-based segment and hydrophilic polyethylene oxide-based segment at the same backbone was synthesized and dispersed as nanoparticles at water phase without using a surfactant or dispersion agent. These UAN nanoparticles were converted to crosslinked amphiphilic polymer (CAP) nanoparticles through soap-free emulsion polymerization and suspension agent-free suspension polymerization process. Emulsion polymerization process exhibited higher conversion of polymerization compared to suspension polymerization process. CAP nanoparticles showed interfacial activity and solubilize hydrophobic pollutants (phenanthrene and toluene) like surfactant micelles. This result indicates possible application of CAP nanoparticles as nano-absorbent for improving efficiency of soil washing and micellar-enhanced ultrafiltration (MEUF) process.

Uma revisão sobre os processos de polimerização em suspensão

Inúmeros processos podem ser utilizados para produção de materiais poliméricos. Cada processo apresenta características peculiares, que permitem produzir resinas com as mais variadas propriedades, visando a diferentes aplicações do material polimérico final. Os processos de polimerização em suspensão são bastante empregados para produção de resinas poliméricas por apresentarem muitas vantagens, como a facilidade de separação, fácil remoção de calor e controle de temperatura e, principalmente, pelos baixos níveis de impureza e de aditivação no produto final. Por isso, processos de polimerização em suspensão são apropriados para obtenção de produtos para aplicações biotecnológicas e médicas, dentre outras. O objetivo principal deste trabalho é apresentar uma discussão dos aspectos fundamentais inerentes aos processos de polimerização em suspensão, visando a uma compreensão do efeito das principais variáveis de processo sobre o desempenho de polimerizações em suspensão. Mostra-se também que a espectroscopia do infravermelho próximo (NIRS) pode ser muito útil para permitir o monitoramento e o controle em tempo real de processos de polimerização em suspensão, para a obtenção de materiais poliméricos com características especiais.

Supracolloidal Structures through Liquid‐Liquid Interface Driven Assembly and Polymerization

AbstractSolid particles can adhere to liquid‐liquid interfaces. When emulsion droplets are stabilized in such a way one speaks of a Pickering emulsion. The supracolloidal structures formed by this interface driven assembly process can be referred to as colloidosomes. Herein we explain the concept of colloidosome formation, their deformation behavior upon evaporation of their inner phase. Moreover, we describe Pickering miniemulsion and suspension polymerization processes, both yielding armored raspberry‐type core‐shell composite polymer particles.

Synthesis and characterization of ABS resin using in situ transferring from emulsion to suspension polymerization

AbstractA novel approach based on an emulsion in situ suspension polymerization process for synthesizing poly(acrylonitrile–butadiene–styrene) (ABS) resin is reported. Experimental results show that the reaction system can be transformed from an emulsion state to a suspension polymerization state steadily with the content of polybutadiene (PB) in the range 0–15 wt% in ABS resin. When PB is replaced by poly(styrene‐co‐butadiene) with the content of rubber particles being kept below 20 wt%, the emulsion system can be easily transferred to the suspension polymerization state through a process of latex coagulation in the forward direction, which means that the emulsion solution was dripped slowly into the suspension reaction system in the presence of coagulating agent. The dispersion status of the rubber particles in the ABS resin was studied using transmission electron microscopy, which indicated that the rubber particles were in a dispersed state in a continuous matrix of poly(styrene‐co‐acrylonitrile) when the content of rubber particles was below 20 wt%. The mechanical properties of the ABS resins obtained are as follows: elongation at break, 9.4–45.7%; yield tensile strength, 35.1–42.2 MPa; impact strength, 98.2–116.3 J m−1. Copyright © 2006 Society of Chemical Industry

Recent advances in highly electrostrictive P(VDF-TrFE-CFE) terpolymers

Ferroelectric materials are intrinsically multifunctional and have found a broad range of applications. A new class of semicrystalline terpolymers comprising vinylidene fluoride (VDF), trifluoroethylene (TrFE), and 1,1-chlorofluoroethylene (CFE), were prepared at Institut de Saint-Louis (ISL) via a suspension polymerization process. Relevant studies and results show that this class of electroactive polymers offers unique properties in comparison with other ferroelectric polymers. The terpolymer exhibits high electrostrictive strain (>7%) with relatively high modulus (>0.3GPa). It has been also observed that the large electrostrictive strain is nearly constant in the temperature range from 20 to 80 degC. The high room temperature relative dielectric constant (~50), which is the highest among all the known polymers), high induced polarization (~0.05 C/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), and high electric breakdown field (>400 MV/m) lead to very high volume efficiency for the electric energy storage operated under high voltage (~10 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> )

Recent advances in highly electrostrictive P(VDF-TrFE-CFE) terpolymers

Ferroelectric materials are intrinsically multifunctional and have found a broad range of applications. A new class of semicrystalline terpolymers comprising vinylidene fluoride (VDF), trifluoroethylene (TrFE), and 1,1-chlorofluoroethylene (CFE), were prepared at Institut de Saint-Louis (ISL) via a suspension polymerization process. Relevant studies and results show that this class of electroactive polymers offers unique properties in comparison with other ferroelectric polymers. The terpolymer exhibits high electrostrictive strain (>7%) with relatively high modulus (>0.3GPa). It has been also observed that the large electrostrictive strain is nearly constant in the temperature range from 20 to 80 degC. The high room temperature relative dielectric constant (~50), which is the highest among all the known polymers), high induced polarization (~0.05 C/m2), and high electric breakdown field (>400 MV/m) lead to very high volume efficiency for the electric energy storage operated under high voltage (~10 J/cm3)

Polymerization of vinyl chloride in the presence of nanofillers - effects on the shape and morphology of PVC grains

Suspension polymerization of vinyl chloride has been carried out in the presence of various types of nanofillers chosen from clays, silica (pure or functionalized), silicone polymer or hybrid core/shell ones. Nanofillers used in VC polymerization significantly influence the structure and shape of PVC grain: from typical one in case of control sample and in the presence of silica to cake-like in case of functionalized silica, sea-shells with silicone polymer use or and dented balls - not typical for suspension PVC - in the presence of hybrid core/shell particles. The last ones look just as emulsion PVC although were prepared in suspension polymerization process. It has been found, using SEM and TEM methods, that distribution of nanofiller in polymer was rather uniform. MMT is semiintercalated/semiexfoliated in PVC grain. Some regions showing mesoporosity were also found (especially in the presence of silica) suggesting the formation of more ordered structures in the grain. We can foresee that not only the presence and distribution of nanofillers in PVC grain but also the change of PVC grain shape caused by them can both influence the final properties of PVC and its processability.

The influence of local flow conditions on the particle size distribution in an agitated vessel in the case of suspension polymerisation of styrene

The strongly varying local flow conditions in agitated vessels influence the mean diameter and the particle size distribution during the suspension polymerisation process. For the suspension polymerisation of styrene with a dispersed phase content of 50%, the analysis of the particle size distribution gives bi- or trimodal curves with only three characteristic shapes. This is valid for different recipes, mixing conditions, and reactor sizes. An explanation for this phenomenon is given by an analysis of the local flow conditions in connection with the motion of the particles. Using these results yields models for the mean particle size and the possible particle size distribution. These models include well-known laws for the dispersion process and estimate the range of validity. Therefore, it is possible to give an explanation for the variety of partly contradictory empirical equations in the literature.

Preparation of magnetic polystyrene microspheres with a narrow size distribution

AbstractA spraying suspension polymerization process for preparation of magnetic polystyrene microspheres with a narrow size distribution was proposed. The magnetite (Fe3O4) nanoparticles with hydrophobic shell were first prepared by a modified chemical coprecipitation method. Then the oil solution, composed of monomer styrene, crosslinker divinylbenzene, Fe3O4 nanoparticles, and initiator benzoyl peroxide, was sprayed into the poly(vinyl alcohol) aqueous solution by a pressure of nitrogen gas to form droplets. Finally, the droplets would be polymerized rapidly to magnetic polystyrene microspheres at the polymerization temperature. The morphology and magnetic properties of microspheres were examined using a scanning electron microscope and a vibrating sample magnetometer. The results showed that the magnetic microspheres had a narrow size distribution with mean diameter of around 10 μm and smooth surface, and the magnetic microspheres with saturation magnetization of 15.6 emu/g exhibited distinct superparamagnetic characteristics. Powder X‐ray diffraction was used to investigate the structure of the magnetite nanoparticles dispersed in the polystyrene matrix. © 2005 American Institute of Chemical Engineers AIChE J, 2005