Suspension polymerization advantages

Since cross-linked polymers caruiot be re-formed or re-shaped it is necessary to synthesize them in the final physical form appropriate for each particular application. Particles in the size range 50-1000 pm are suitable for laboratory scale chemistry, while larger particles have advantages in large scale continuous processes. Irregularly shaped particles are susceptible to mechanical attrition and breakdown to fines , whereas the process of suspension polymerization [13] yields uniform spherical cross-linked polymer particles often referred to as beads, pearls or resins. These are much more mechanically robust and are widely exploited on both a small and large scale e. g. as the basis of ion exchange resins [14]. 

Suspension polymerizations are among the most convenient laboratory procedures as well as plant procedures for the preparation of polymers. The advantages of this method include wide applicability (it may be used with most water-insoluble or partially water-soluble monomers), rapid reaction, ease of temperature control, ease of preparing copolymers, ease of handling the final product, and control of particle size. 

Today, superabsorbent polymers are made using one of two primary methods suspension polymerization or solution polymerizations. Both processes have their advantages over the other and both yield a consistent quality of product. 

It would be useful to have liquid present in the polymerization reactor that provided the advantages of a solvent but without any of the disadvantages. Sound unlikely How about water One technique, called suspension polymerization, involves adding monomer to water in a reactor, agitating the mixture rapidly so that the monomer breaks apart into very small droplets, adding an initiator that is soluble in the monomer, and heating. Each droplet acts as a microbulk polymerization, the water very effectively removes the heat of polymerization, and the resulting polymer spheres are easily separated and filtered. This process, also known as bead polymeriza-... 

Suspension polymerization, 94-95 Sustainable development, 199 Sustained-release drugs, 187 Syndiotactic polymers, 104, 261 Synthesis of polymers, 5, 34, 83-115. See also Polymerization biopolymers, 27-28, 43 deliberate, to promote degradation, 183 dendrimers, 110-113, 112-113 solid-phase, 32 Synthetic polymers, 5-7, 8 abiotic degradation of, 182 advantages of, 7-8 categories of, 6-7, 7 cost of, 8 density of, 7-8 first, 56-57... 

Monomer droplets are suspended in the water through the use of agitation and stabilizers, such as methyl cellulose, gelatin, polyvinyl alcohol, and sodium polyacrylate.32 Typical droplet sizes are 0.01-0.5 cm. A monomer soluble initiator is added to begin the polymerization. The kinetics of suspension polymerization are the same as for bulk polymerization, but suspension polymerization offers the advantage of good heat transfer. Polymers such as polystyrene, PVC, and polymethyl methacrylate are prepared by suspension polymerization. 

The suspension polymerization process has a number of distinct advantages over competitive processes. It allows excellent control over the polymerization temperature and a lower viscosity reaction medium. Furthermore,... 

As a reaction medium for transition rnetal-catalyzed polymerizations, water will, most likely, not be the first choice. The extreme water sensitivity of Ziegler or Phillips catalysts is well known. However, carrying out polymerization reactions in aqueous systems offers unique advantages. Thus, traditional free-radical emulsion and suspension polymerization are carried out on a large scale industrially. A brief review of these established reactions demonstrates some specific properties of polymerizations in aqueous systems. 

Suspension polymerization is designed to combine the advantages of both the bulk and solution polymerization techniques. It is one of the extensively employed techniques in the mass production of vinyl and related polymers. Suspension polymerization (also referred to as bead or pearl polymerization) is carried out by suspending the monomer as droplets by efficient agitation in a large mass (continuous phase) of nonsolvent, commonly referred to as the dispersion or. suspension medium. Water is invariably used as the suspension medium for all water insoluble monomers because of the many advantages that go with it. Styrene, methyl methacrylate, vinyl chloride, and vinyl acetate are polymerized by the suspension... 

Heat and viscosity control in suspension polymerization is relatively easy compared to bulk polymerization. Another important advantage of the method is that the polymer product can be obtained directly in spherical bead form (which may subsequently be functionalized to make ion-exchange resins). 

By comparison with the intensively investigated syntheses of low molecular weight compounds by biphasic catalysis, catalytic polymerization in aqueous systems has received less attention. This is somewhat surprising, as polymerization in aqueous systems offers unique advantages, as illustrated by the large-scale applications of free-radical emulsion and suspension polymerization. 

Polymerization of vinyl monomers by free-radical mechanisms is perhaps the most widely encountered and best understood mode of vinyl polymerization. The popularity of free-radical polymerization is due in substantial part to the many advantages that this route to polymers offers to industry. The polymerization process is noteworthy for its ease, convenience, and relative insensitivity to impurities, such as water and oxygen, that plague ionic polymerizations. Indeed, it is common to carry out free-radical polymerizations in water as a suspending medium, as in emulsion and suspension polymerization. Another advantage of free-radical polymerization is that it offers a convenient approach toward the design and synthesis of myriad specialty polymers for use in almost every area. 

PVC is insoluble in VCM. The precipitated polymer tends to coagulate in the conversion range of 1-8%. As the conversion continues, the precipitated polymer absorbs more and more monomer, and at a 15-20% conversion, the reactor contains solid polymer swollen with monomer in a monomer atmosphere. The horizontal autoclave prevents the formation of large polymer blocks by breaking them up. Advantages claimed for this process are the higher bulk density, improved particle size distribution, and more rapid plasticizer absorption. Talamini and coworkers (J ) have demonstrated that the bulk polymerization process is kinetically equivalent to suspension polymerization. 

Suspension Polymerization - Refers to a heterogeneous polymerization regime in which the product of the reaction is a solid forming a suspension in the liquid medium of reaction. Little or no surfactant is added to the reaction medium. Characteristics of the process include high agitation rate and poor particle size control. An advantage of this reaction is high purity of the polymer product as compared to that of the dispersion method. 

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