Copolymerization of ethylene and vinyl acetate at low pressure: Determination of the kinetics by sequential sampling

Abstract

In behalf of a detailed study on the course of copolymerization reactions, this paper describes an improved and generally applicable experimental method and an efficient computational procedure to match. The experimental method is based on quantitative gas chromatography, and permits frequent measurement of the monomer feed composition throughout (co)polymerization processes at pressures up to 40 kgf/cm2 ( = 38.7 atm). The given method is applied to the study of the radical copolymerization of ethylene with vinyl acetate in a series of kinetic experiments, at 62°C and 35 kgf/cm2 ( = 33.9 atm) in tert‐butyl alcohol, in which 20–40% conversion is reached. Monomer feed composition and degree of conversion are entered into a computational procedure based on nonlinear least‐squares methods applied to the integrated version of the copolymer equation. The experimental data, covering a region of ethylene molar feed fractions between 0.24 and 0.74 and copolymer concentrations up to 8 wt‐%, are precisely consistent with the usual model. The respective reactivity ratios are r̂e = 0.743 ± 0.005 and r̂v = 1.515 ± 0.007.

On anomalous addition in ethylene-vinyl acetate copolymerization

“…Earlier investigations [7] on the kinetics of ethylene-vinyl acetate copolymerization at low pressure (35 atm) indicate that the experimental data are precisely consistent with the usual Mayo--AIfrey Table I. Rocking deformation vibrations of methylene sequences in ethylene-vinyl acetate copolymers…”

“…The relevant samples were collected before 15°o conversion was reached. Details are given elsewhere [7]. DISCUSSION As in Eqn.…”

“…Lyubetzky's factor 2. representing the fraction of--(CH,)2--sequences formed by "'head-to-head" addition has been calculated according to the relation 2 = .~/ff + 1). The number average sequence length of ethylene sequences (x-) has been calculated from the kinetic data [7]. This estimation of 2 holds under the following conditions: (1) any anomalous vinyl acetate to ethylene addition will be followed either directly, or after a sequence of anomalous vinyl acetate to vinyl acetate additions, by a normal vinyl acetate addition: and (2) the number average sequence length of vinyl acetate sequences > 2.…”

Anomalous copolymerization behavior of styrene and ethyl methacrylate at high conversion

“…Both monomer feed ratio (q) and conversion were calculated from data obtained by quantitatively monitoring monomer concentrations by means of GLC during the entire course of the reaction. This method, introduced by German and Heikens (11,12), is particularly useful in studies on high conversion copolymerization since the course of the process can be detected in detail and very easily. In addition, copolymer compositional analysis becomes redundant, thus avoiding all pertaining errors (e.g.…”

“…Both monomer feed ratio (q) and conversion were calculated from data obtained by quantitatively monitoring monomer concentrations by means of GLC during the entire course of the reaction. This method, introduced by German and Heikens (11,12), is particularly useful in studies on high …”