Non-uniqueness in determination of terminal and penultimate model reactivity ratios in the styrene-methyl methacrylate free-radical copolymerization system

✍ Scribed by Andrzej Kaim; Paweł Oracz

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 593 KB
• Volume: 6
• Category: Article
• ISSN: 1022-1344
• DOI: 10.1002/mats.1997.040060216

✦ Synopsis

Abstract

The terminal and penultimate model reactivity ratios in the free‐radical copolymerization of styrene and methyl methacrylate in bulk at 40°C were calculated by means of the simplex and scanning methods. Calculations showed that for the terminal model r~1~ and r~2~ vary in comparatively narrow ranges of 0.548–0.552 and 0.480–0.483, respectively. For the penultimate model, the most accurate reactivity ratios calculated by the simplex method, which were r~11~ = 0.727, r~22~ = 0.490, r~21~ = 2.890, r~12~ = 4.583, are surrounded with sets of reactivity ratio values of equal accuracy. The ranges of variation were found to be 0.711–0.746, 0.487–0.492, 2.810–2.970 and 4.213–5.049, respectively. Numerical values of the penultimate r‐parameters calculated with the simplex method depend, due to the structure of the multidimensional space (r~11~, r~22~, r~21~, r~12~, σ), on the initial guess for the r‐parameters. Use of the covariance matrix for the estimation of the indetermination ranges is discussed.