No abstract

SynopsisApplication of the Arrhenius relationship for temperature and ratio of isomeric units in polybutadiene made in the presence of butyllithium initiator is consistent with the existence of three simultaneous competing reactions. Evidence in the literature is cited to support the possibility that the growing chain end exists in a composite equilibrium producing localized structures which on reacting with monomer result in fixed isomeric units. The compliance of the data with the thermodynamic relationship permits the extrapolation of a narrow set of data to a broad temperature range.

synopsisTelechelic elastomers, polymers with reactive terminal groups, can be prepared in emulsion and solution systems. Examples of characterization of the polymers and preparation of a mercapto telechelic copolymer in an emulsion system and of mercapto-, hydroxy-, and aziridinyl-telechelic elastomers in solution systems are given. The elastomers were cured in peroxide or sulfur-accelerator formulations. The telechelic polymers exhibited enhanced stress-strain and dynamic properties in comparison to those of the controls. In tread formulations, outstanding properties were obtained for the mercapptoand axiridinyl-telechelic butadiene-styrene copolymers.

A model equation derived for the viscosity-average degree of polymerization (P.) for the incremental addition of modifiers, P, = K ( (exp{arzl] indicates a minimum should occur in a curve of P. versus conversion at which the increments are added, zl. Incremental addition of commercial tertdodecyl mercaptan in the laboratory to SBR recipes a t 5°C. showed effects contrary to those predicted by the model equation, but incremental addition experiments with tert-nonyl mercaptans resulted in a minimum in viscosity versua 21 curves, changed the molecular weight distribution, and required 34 wt.-% less mercaptan than did the tert dodecyl mercaptan control (all the tertdodecyl mercaptan added initially). Incremental additioh of tertnonylmercaptan in pilot plant 20-gal. autoclave reactors gave essentially the same results found in the laboratory bottle experiments. The stress4rain and mixing properties of the incrementally modified polymer and the tertdodecyl mercaptanmodified control were essentially the same within experimental error. Conditions required for successful application of the incremental modifier technique are given.

Philprene A and B are chemical rubbers copolymerized from butadiene and styrene at 41°and 14°F. Their outstanding characteristic is high performance when fabricated into tires.