High composition drift comonomers

This is an extremely difficult monomer pair to use for acrylic fibers, which typically requires only 5-10% of a comonomer. To offset the tendency to alternate, a very low level of styrene would be required in the reaction medium and there would be a strong tendency for compositional drift in high-conversion processes. 

Indeed, it can be shown that if concentration changes are not considered, the remaining temperature dependent portion of Eqs. 2 and 3 are numerically equivalent. Under isothermal conditions th conversion histories match provided that one of the comonomers is not exhausted prior to the completion of the reaction. Under non-Isothermal conditions, composition drift influences the agreement between the two forms. When drift is towards the more reactive comonomer, the approximate form underestimates the thermal trajectory (See Fig. A). Conversely, when drift is towards the less reactive of the pair, the approximate form overestimates the trajectory. Similar behavior is noted in the RA boundaries of Fig. 1. Points for the SAN system lie above the homopolymer boundary, and drift is towards high AN content compositions. Points for the ANMMA boundary lie below the homopolymer boundary, and drift is towards the less reactive of the pair, MMA. As conditions become either more adiabatic or more isotherm, spread between the forms narrows. The poorest agreement of the forms occurs at the para-metr i ca lly sensitive point of the RA transition. 

Thus, when 3 < < 1, (y)jnst drifts downward and when 3 < > 1 it drifts upward. We therefore conclude that to achieve a target cc high in comonomer 1, say, instantaneous response considerations (Table IX) suggest that,given (x]), a low value for 3 < is required, whereas equation 37 indicates that 3 < < 1 would cause the composition to drift downward, opposite to the target direction. Obviously, when 3 < = 1, no drift occurs. 

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