Suspension Polymerization Reactions Research Articles

Preparation of a novel anion exchange group modified hyper-crosslinked resin for the effective adsorption of both tetracycline and humic acid

A novel hyper-crosslinked resin (MENQ) modified with an anion exchange group was prepared using divinylbenzene (DVB) and methyl acrylate (MA) as comonomers via four steps: suspension polymerization, post-crosslinking, ammonolysis and alkylation reactions. The obtained resin had both a high specific surface area (793.34 m2·g−1) and a large exchange capacity (strong base anion exchange capacity, SEC: 0.74 mmol·g−1, weak base anion exchange capacity, WEC: 0.45 mmol·g−1). XAD-4 was selected as an adsorbent for comparison to investigate the adsorption behavior of tetracycline (TC) and humic acid (HA) onto the adsorbents. The results revealed that MENQ could effectively remove both TC and HA. The adsorption capacity of XAD-4 for TC was similar to that of MENQ, but XAD-4 exhibited poor performance for the adsorption of HA. The adsorption isotherms of TC and HA were well-fitted with the Freundlich model, which indicated the existence of heterogeneous adsorption through cation-π bonding and π-π interactions. The optimal solution condition for the adsorption of TC was at a pH of 5–6, whereas the adsorption of HA was enhanced with increasing pH of the solution.

Influence of Semi-Batch Operations on Morphological Properties of Polystyrene Made in Suspension Polymerization

Abstract Suspension polymerization reactions in industrial processes are usually carried out with batch operations. However, discontinuous systems do not offer process flexibility like semi-continuous ones. Studies and practical applications of semi-batch operations in heterogeneous systems are commonly found for emulsion polymerization systems in order to control copolymer composition, molecular weight, final particle size, particle morphology and reaction rate. On the other hand, semi-batch operations are rarely used to carry out suspension polymerizations. In these systems, this sort of operation strategy can be applied for the production of core-shell particles. The present study intends to show that semi-batch operation can also be used in suspension polymerization systems to manipulate and improve some morphological properties of the produced particles. The styrene suspension polymerization was used as case study. The reactions were carried out considering different monomer feeding rates and reaction times at which the monomer feed stream begins to be added to the system. Results showed that, depending on the semi-batch strategy adopted ( i.e. reaction time for the beginning of the organic phase feed and feeding rate), it is possible to successfully control some morphological properties of the particles, leading to the production of more uniform particles sizes than those ones obtained in classical suspension systems.

Design of prolonged release tablets using new solid acrylic excipients for direct compression

The design of new excipients that extend the release of drugs from tablets over prolonged periods is essential in reaching enhanced therapeutic performances. In this sense, the objective of this study was to develop new excipients, based on acrylic monomers (ethyl acrylate, methyl methacrylate, and butyl methacrylate) for use in direct compression (DC). The polymeric excipients were prepared by suspension and emulsion polymerization reactions and were characterized by FTIR to confirm the polymerization reaction. For the success of direct compression, excipients must present good flow and compactability properties. Therefore, excipients were submitted to analysis of morphology (SEM), particle size and size distribution by laser diffraction, and powder density (bulk density and tapped density). The Carr index, Hausner ratio, flow ratio, and cotangent of the angle α were determined. Thereafter, the polymeric excipients were used to prepare inert matrices by DC using propranolol hydrochloride (PHCl) as a model drug. The tablets were evaluated for average weight, breaking force, and friability tests. The release profiles were determined, and the dissolution kinetics was studied. The results indicated that matrices prepared from excipients obtained by suspension polymerization (NWCB and PECB) presented a release of PHCl for a period exceeding 12 h, most likely due to the higher micromeritic properties. The results suggested that the increase in the percentage of polymers, as well as in the compression time, resulted in a higher hardness of the matrix with a reduced rate release of the PHCl. Finally, in vitro preliminary tests showed that the polymeric excipients produced were non-toxic for the gingival fibroblasts.

Comparison of techniques for the determination of conversion during suspension polymerization reactions

The determination of conversion during suspension polymerization reactions is not an easy task due to the heterogeneity of the reaction medium and the tendency of particles to agglomerate rapidly when stirring is stopped. Usually, bulk polymerization in ampoules is employed to study the kinetics of suspension polymerization reactions. In this work, a comparison of different techniques for the determination of conversion during suspension polymerization reactions is presented. Results showed a good agreement between the conversion obtained by gravimetry during styrene suspension polymerization and on-line conversion monitoring data using fiber-optic based Raman Spectroscopy. Nevertheless, the polymerization rate of styrene bulk polymerization carried out in ampoules was higher than the real reaction rate of styrene suspension polymerization due to slightly higher reaction temperatures. Simulation results using the experimental temperature data in a mathematical model confirmed these results.

Water‐Soluble Ionic Liquids as Novel Stabilizers in Suspension Polymerization Reactions: Engineering Polymer Beads

Aqueous solutions of ionic liquids have been used as novel and environmentally friendly reaction media to synthesize and "control" the size of different cross-linked polymer beads by suspension polymerization reactions. It was found that the investigated ionic liquids can act as novel stabilizing agents of the suspensions as a result of their surface-active properties. The results have demonstrated that the average size of polymer beads can be varied from the macro- to the nanoscale and their surface area can also be "adjusted" by this synthetic approach. Furthermore, the use of a combination of ionic liquids and water for the synthesis of polymers, the simple isolation of the products formed in this polymerization procedure, as well as the recycling of the continuous medium for further reactions open up possibilities for the development of "new and green" polymerization processes.

Monitoring stability of reaction and dispersion states in a suspension polymerization reactor using electrical resistance tomography measurements

A system was constructed for visualizing the dispersion states of liquid monomer and polymer droplets in a suspension polymerization reaction in a non-intrusive and continuous manner using electrical resistance tomography measurements. Using this system, a method was established for keeping reaction states stable and the quality of the particles produced good by varying the mixing conditions, such as the rotational speed of the impeller and the injection amount of dispersion reagents, under the principles that the lower the rotational speed of the impeller, the better; and the smaller the injection amount of dispersing agents, the better. It was found that the amount of additional injection significantly affected both the sharpness and the average value of the particle diameter distribution, based on the data of the tomograms.

Online Monitoring of Suspension Polymerization Reactions Using Raman Spectroscopy

The main objective of this paper is verifying the feasibility of using Raman spectroscopy for online monitoring of suspension polymerization reactions. Whether the Raman spectra are affected by the particle size distribution (PSD) is also investigated. It is shown that it is possible to estimate the evolution of conversion during suspension polymerization from Raman spectra collected with the probe connected to the reactor window with a short acquisition time. Results also indicate that monitoring by Raman spectroscopy may allow identification of abnormal behavior during suspension polymerization reactions with the formation of unexpected PSD. Furthermore, results suggest that Raman spectroscopy probably has the potential to infer the PSD of suspension polymerizations because the Raman spectrum is affected by the PSD.

Industrial Process Monitoring of Polymerization and Spray Drying Processes

Radical polymerizations in emulsion, suspension and solution are very important industrial production processes. To be able to control these processes to achieve good product quality makes the development of methods to observe these reactions in situ a very important topic not just in academia, but also in industry. In this paper, the advantages and disadvantages of different methods to follow emulsion and suspension polymerization reactions as well as spray drying processes are discussed from an industrial point of view. Calorimetry, near infrared spectroscopy and Raman spectroscopy are the methods with the highest potential for on‐line applications. Droplet formation in spray drying can be observed by laser light scattering methods. Spectroscopic methods have used data analysis methods (principal component analysis, partial least squares) for a number of years. These methods can also be used as “soft sensors” with standard process data. Examples how these soft sensors can be applied to emulsion polymeri...

Influence of the morphology of poly(EGDMA-co-HEMA) on the chemical modifications and retention of O-phosphothreonine

The influence of the morphology of ethylene glycol dimethacrylate-hydroxyethyl methacrylate copolymer [poly(EGDMA-co-HEMA)] base support to obtain different Fe 3+-containing sorbents and their properties in retention of O-phosphothreonine [Thre(P)] is examined in this paper. Three base supports poly(EGDMA-co-HEMA) (I–III) were obtained using different quantities of initiator in suspension polymerization reactions. These products were submitted to chemical modifications using 1,4-butanediol diglycidyl ether (BDGE) in activation reactions and different chelating agents (iminodiacetic acid, IDA; disodium ethylenediamine tetraacetate, EDTA; and hexamethylenediamine tetrapropanoic acid, HMDTP) in coupling reactions to attain Fe 3+-containing sorbents. Properties such as specific surface area ( S s), specific pore volume ( V p), scanning electron microscopy (SEM), IR spectroscopy, quantity of functional groups (oxirane and carboxyl), amount of chelated metal ion, ligand occupation ( L), swelling studies as well as quantity of O-phosphoamino acid retained were used as comparative parameters for matrices. In general, the derivatization reactions proved to be more efficient when higher S s of macropores (50–400,000 nm) were available in the matrix. In our case, it was observed when highest percentage of initiator was used. On the other hand, the effect of accessibility of surface area on the yield of coupling reactions was noticed when comparing the different chelating agents since the number of carboxyl groups present in products was higher when the molecular size of the chelating agent was lower. Although all Fe 3+-containing sorbents resulted efficient to retain Thre(P), the values of retention of the amino acid were slightly higher when IDA-containing matrices were used irrespective of the quantity of metal chelated. This could be probably due to the fact that the IDA ligand could be bounded to the matrix in sites that though accessible for the center of adsorption were hard for Thre(P) to access.

Emergency stopper for VCM suspension polymerization

AbstractBecause of the exothermicity of reaction and the necessity of using active initiators for the vinyl chloride monomer (VCM) suspension polymerization reaction, a study was undertaken in order to choose the best polymerization inhibitor for emergency situations such as temperature runaway, power failures, and agitation system problems. The effect of triethylene glycol‐bis3(3 terc‐butyl‐4‐hydroxy‐5‐methyl phenyl) propionate (1) and N‐nitrosophenylhydroxylamine ammonium salt (2) cited in the literature as free radical polymerization inhibitors on VCM suspension polymerization reactions is shown.

An analytical method to determine time–conversion relationship for a multicomponent monomer mixture in a suspension polymerization system

A precise method has been developed for the quantitative measurement of individual monomers during suspension polymerization. Since no simplifications or assumptions are made regarding the components of the polymerization system, this method can be used to study the conversion kinetics of monomers in the actual suspension polymerization reaction.