Terpolymerization parameters

The parameters a = l/rij5 the number of which equals m(m — IX are reciprocal reactivity ratios (2.8) of binary copolymers. Markov chain theory allows one, without any trouble, to calculate at any m, all the necessary statistical characteristics of the copolymers, which are formed at given composition x of the monomer feed mixture. For instance, the instantaneous composition of the multicomponent copolymer is still determined by means of formulae (3.7) and (3.8), the sums which now contain m items. In the general case the problems of the calculation of the instantaneous values of sequence distribution and composition distribution of the Markov multicomponent copolymers were also solved [53, 6]. The availability of the simple algebraic expressions puts in question the expediency of the application of the Monte-Carlo method, which was used in the case of terpolymerization [85,99-103], for the calculations of the above statistical characteristics. Actually, the probability of any sequence MjMjWk. .. Mrl 4s of consecutive monomer units, selected randomly from a polymer chain is calculated by means of the elementary formula ... 

When the reactivity ratios ry can be expressed in terms of the parameters of the well-known Q-e scheme of Alfrey-Price [20,157], the condition (4.20) always holds [147, 150] and in the case of terpolymerization the general Eqs. (3.8) and (4.10) transform into the simplified equation [158]. It is rather curious that similar equations have been derived at the end of the 1940s [159] within the framework of the Alfrey-Price scheme, being investigated even for the general case of copolymerization of arbitrary number m of monomer types. 

Ethylene has been co-polymerized with virtually any conceivable a-olefin, from propylene to vinyl-terminated PE and PP macromonomers. Ethylene/propylene (E/P) copolymerization to produce saturated rubbers and ethylene/propylene/diene (EPD) terpolymerization to produce unsaturated, vulcanizable rubbers will be discussed in Section 4.09.4.1.3. 1-Butene, 1-hexene, and 1-octene are the most commonly used co-monomers for the production of LLDPE. Ethylene/octene co-polymers, developed by Dow and marketed under the Engage tradename, have been shown to have improved thermal properties compared to ethylene/butene and ethylene/hexene co-polymers.503 In ethylene/a-olefin (E/O) co-polymeriza-tions, the critical parameters are co-monomer reactivity and co-monomer distribution . The former is most conveniently described by the relative reactivity parameter, R, defined as the ratio between polymer composition and reactor medium composition. 

Figure 22-1. Change in mole fraction of acrylonitrile (AN), butyl acrylate (BA), and butadiene (BU) in monomer mixture (atm ") and in copolymer (x ) as a function of yield for the free radical terpolymerization of an [AN]o [BA]o [BU]o - 0.5 0.25 0.25 mixture at 60 C. The copolymerization parameters are rANBU = 0.1, 2- buba 9.9, tbuan 3.5,...

The six copolymerization parameters of terpolymerization can only be determined after great effort. Consequently, they are mostly obtained from the corresponding bipolymerizations. But all required copolymerization parameters are not always known, and in such cases, the missing parameters can be estimated in the following way ... 

Table 22 5. The Product of the Binary Copolymerization Parameters for the Free Radical Terpolymerization of the Conjugated Monomers Methyl Acrylate, Methyl Methacrylate, Acrylonitrile, and Styrene, as well as for the Nonconjugated Monomers Vinyl Acetate, Vinyl Chloride, and Vinylidene Chloride...

We have seen how the compositions in a copolymerizing system can be described in terms of two parameters, o and r2- What does it take to describe the terpolymerization of monomers Mi, M2, and M5 If you are feeling particularly masochistic, you might try to work out the terpolymerization equivalents of Equation 11.11. 

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