Commercial Methods of Thermoplastic Polymerization

When we design commercial polymerization plants we must consider the characteristics of both the monomer and the final product. This allows us to define the optimum configuration to produce a specific polymer. Polymerization reactions can take place in homogeneous solutions or heterogeneous suspensions. For homogeneous processes, the diluted or pure monomer(s) are added directly to one another and the reaction occurs in the media created when mixing the reactants. When the reactants are added directly to one another, the process is referred to as a bulk process. With heterogeneous processes, a phase boundary exists which acts as an interface where the reaction occurs. 

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Aromatic polysulfones are a commercially important class of thermoplastic polymers [127]. They have highly desirable qualities such as chemical inertness, thermal stability, and flame retardency [128,129]. Although a number of methods are available for the synthesis of polysulfones [130,131,132], step polymerization methods are the most widely used industrially [127]. Polysulfones have been synthesized with the involvement of sulfonylium cations as propagating species. 

Details about the basic chemistry and polymerization methods are inclnded in Chapter 2 fnndamental properties of the resulting prodncts are discnssed in Chapter 3, and processing and applications of thermoplastics in Chapter 4. Becanse flno-roelastomers and aqueous systems have specific and different technologies from other commercial fluoropolymers, they are discussed in Chapters 5 and 6, respectively. 

An alternative method of initiation is through the use of the radical anion produced from the reaction of sodium (or lithium) with naphthalene. Such radical anions react with styrene by electron transfer to form styrene radical anions these dimerize to produce a dianion, which initiates polymerization as outlined in Scheme 14. One particular feature of this method is that polymerization proceeds outwards from the centre. Subsequent reaction of the living chains ends with another suitable monomer system produces a triblock copolymer. This is the principle by which styrene-butadiene-styrene triblock copolymers (formed when butadiene is polymerized in the same way. and styrene is added as second monomer) are produced commercially. This material behaves as a thermoplastic elastomer, since the rigid styrene blocks form cross-links at room temperature on heating these rigid styrene portions soften, allowins the material to be remoulded. ... 

Foams can be made with both thermoplastic and thermosetting plastics. The well known commercial thermoplastic foams are polystyrene, PVC, polyethylene, polypropylene, ABS copolymer, cellulose acetate. The thermosetting plastics which may be mentioned, among others, are phenol-formaldehyde, urea-formaldehyde, polyurethane, epoxy, and silicone. The methods of manufacture of some of these polymeric foams are given below. 

Johnson et al. (15) reported the first attempt to synthesize PEEK by polycondensation of bisphenolate with activated dihalides using DMSO as a solvent and NaOH as a base. High molecular weight polymers were difficult to obtain due to the crystallinity and the resulting insolubility of polymers in DMSO. To circumvent the solubility problem, Attwood and Rose (16) used diphenyl sulfone as a solvent, and the polymerization was carried out close to the melting point. Victrex PEEK was commercialized by the British company ICI in 1982 using this method. Since its commercialization, this thermoplastic polymer has been used in a wide range of applications, from medicine to the electronic, telecommunications and transport industries (automobile, aeronautic and aerospace) (17,18). 

MOLDING/METALLIZATION. Molded thermoplastic circuit board substrates may be rendered selectively conductive by several additive process techniques including conductive polymeric thick film inks (PTF), and semi and fully additive electroless/electrolytic platings. Of the various chemical process methods developed to produce circuitry on a molded plastic substrate, one method practiced by Pathtek, A Kodak Company, combines both "catalytic" and "non-catalytic" resins in a highly automated commercialized two-shot molding/selective metallization process. 

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