Free‐Radical Polymerization: Homogeneous

Abstract

Free-radical polymerization (FRP) is one of the most important commercial processes for preparing high molecular weight polymers. It can be applied to almost all vinyl monomers under mild reaction conditions over a wide temperature range and, although requiring the absence of oxygen, is tolerant of water. Multiple monomers can be easily copolymerized via FRP, leading to the preparation of an endless range of copolymers with properties dependent on the proportion of the incorporated comonomers. This chapter will provide an overview of the kinetics and mechanisms, and the techniques used to construct mathematical representations of bulk and solution FRP. The description will also serve as a good base for the suspension and emulsion FRP chapters that follow. FRP Properties and ApplicationsPolymers produced via free-radical chemistry include the following major families:Low-density polyethylene (LDPE) and copolymers, used primarily in films and packaging applications. LDPE has density of <0.94 g cm À3 , and is produced via high-pressure free-radical polymerization; polyethylenes of higher density (and polypropylene) are produced via transition metal catalysis, as described elsewhere (see Chapter 8). Poly(vinyl chloride) and copolymers, used primarily to produce pipe and fittings, flooring material, and films and sheet. Polystyrene and its co-and terpolymers with acrylonitrile and butadiene. Homopolymer is used for packaging and containers, while the acrylonitrile-containing polymers are used for various molded products in the appliance, electronics, and

Modelling and Optimization of Nonlinear Polymerization Processes

“…Another approach is to look at the sum of moments of live and dead polymer chains . For this sum the moment differential equations are zero in the case of branching.…”

The method of moments used in polymerization reaction engineering for 70 years: An overview, tutorial, and minilibrary

“…That begins with an intramolecular H‐atom abstraction of P n , also called back‐biting reaction, generating mid‐chain radicals (MCR, Q n ) and subsequent addition of monomer in the MCR to form SCB. [ 36 ] Additionally, at high temperatures, the MCRs suffer scission events, such as in the polymerizations of butyl acrylate at 140°C [ 37 ] and styrene at 260–340°C. [ 38 ] The next set of reactions represents the butyl acrylate polymerization involving back‐biting, MCR propagation, and scission events, as shown in Scheme 2.…”

Measurement and Modeling of Semi-Batch Solution Radical Copolymerization of N-tert-Butyl Acrylamide with Methyl Acrylate in Ethanol/Water

“…Due to its increased stability, a significant fraction of the total radicals can be MCRs, even at lower temperatures when the total number of short-chain branches (SCBs) formed by the reaction is low (<1% of total polymer units). Both the MCR fraction (which influences rate) and the extent of branching are functions of the monomer concentration and temperature [ 11 , 12 ].…”