Characterization of networks from the peroxide cure of polybutadiene

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Abstract
Polybutadienes with molecular weights varying between 12,500 and 92,000 and containing from 23.4% to 93% 1,2‐structure were cured with 1 to 8 parts per hundred of dicumyl peroxide at temperatures ranging from 130° to 175°C. The cured samples were swollen in toluene and the crosslink densities were determined by application of the Flory‐Rehner equation. The unsaturation remaining after cure was measured by infrared and was found to be in good agreement with the unsaturation level calculated from the swelling data. From these measurements it was found that a molecular weight between crosslinks of less than 100 g/mole could be obtained. The number of double bonds consumed per radical formed was found to vary from 6 to 185. The highest values were obtained with polymers highest in 1,2‐content cured with the lowest initiator levels and at the lowest temperatures.