Compositional Heterogeneity of Butadiene–acrylonitrile Copolymers Prepared in Emulsion at 5°c

Abstract

The copolymerization of b~rtadiene and acrylonitrile is very similar to the copolymerization of butadiene and styrene. Polymers predominantly butadiene may be studied by conventional solution techniques but the study of polymers rich in acrylonitrile requires improved solvents for these materials. Polymerization rates are greatest for monomer ratios approximating equal proportions. The mercaptan modilier disappears much more slowly than in the b~~tadiene-styrene system, the regulating index approximating unity. The n~unber average molecular weights calculated from the mercaptan disappearance curves indicate uniform polymer molecular weights to relatively high conversions after which there is a decrease. T h e viscosity data indicate a rise in viscosity \vith conversion, which elfect is overcome for charges rich in acrylonitrile by the lessening of branching, the more rapid disappearance of mcrcaptan a t high conversion, and the tendency of polymers containing over 50% acrylonitrile to show very low dilute s o l~~t i o n viscosities in the solvents tested. Viscosity molecular weights have been calculated and estimates of the molecular weight tlistributjon made. These distributions appear to be quite narrow and the ~~s u a l broaden~ng a t higher conversions is prevented by tlre increased nrodiher consun~ption and increased vinyl content of the poly~ner prepared with 50 parts acrylonitrile in the charge. The bountl acrylonitrile has been determined a t various conversions and the reactivity ratios have been found to be r, = 0 . 2 s and r2 = 0.02 for emulsions and rl = 0. 18 and r? = 0.03 for oil phase portion only. Q is 0.74 and e is 1.17 as calculated by the Alfrey-Price equations.

Mathematical Modeling of Emulsion Copolymerization of Acrylonitrile/Butadiene

“…The study of nitrile rubber (NBR) or acrylonitrile/ butadiene copolymerization has been limited to issues concerning the characteristics of the copolymer composition (Wall et al, 1948;Embree et al, 1951;Vialle et al, 1971;Guyot et al, 1984). The copolymerization of each monomer with styrene has received far greater attention.…”

Stent migration during transcatheter management of coarctation of aorta

“…The properties of interest that characterize polymer product quality in this study comprise average molecular weights (both weight‐ and number‐average), bound AN in the copolymer (cumulative copolymer composition or $\bar F_{{\rm AN}}$ ), degree of chain branching, number or average size of polymer particles and, of course, conversion. Embree et al [1], Wall et al [2], Vega et al [3], and Gugliotta et al [4] have reported typical trends and profiles of some of these polymer properties obtained experimentally in the batch emulsion polymerization of NBR. Vega et al [3] and Gugliotta et al [4] have in addition discussed semibatch strategies used to produce NBR emulsions of desired quality.…”