Natural rubber secondary accelerators

This compoimd is used as primary or secondary accelerator or sulfur donor for both natural rubber and synthetic. 

TMTM is used as both a primary and secondary accelerator for various cure packages for natural and synthetic rubber, especially polychloroprene. Sometimes TMTM imparts better scorch resistance at processing temperatures than TMTD. 

ZnDBC is used mainly as a secondary accelerator to increase the cure rate of a rubber compound. ZnDBC is used with natural and synthetic rubber-based compounds, especially EPDM. 

From the practical standpoint, two minor alterations in cure system should be considered if the cure characteristics of a synthetic polyisoprene need to be altered to match exactly that of a natural rubber compound. A secondary accelerator (e.g. 0T-0-2phr of TMTD) may be added to a sulphur/sulphenamide system to reduce time to optimum cure. An increase of between 5 and 15 %, pro rata, in both sulphur and accelerator will improve the degree of cure, as indicated by maximum torque value on a Monsanto rheometer. 

A new binary accelerator system uses l-phenyl-2-4-dithiobiuret (DTB) as a secondary accelerator for 2-(4-morpholinothio)-benzothiazole (MBS) for the sulphur vulcanisation of natural rubber. Particular reference is made to the processing characteristics, mechanical properties and swelling behaviour. It was found that that irrespective of the concentration of DTB, all the cure reactions followed first order kinetics. Mechanical properties of the system were analysed for different DTB loading, and the strain crystallising nature of NR was found to be not affected by DTB. Based on processing characteristics, mechanical properties and swelling behaviour, the optimum dosage of DTB was found out. 24 refs. 

ZDEC is used in the following applications as a fast primary or secondary vulcanization accelerator in NR, SBR, IIR, EPDM and for natural and synthetic latex a stabilizer in butyl, butadiene, and urethane rubbers an antioxidant in rubber-based adhesive systems a stabilizer in cement a heat stabilizer for polyethylene. 

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