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5635623 
Journal Article 
The use of thiol-amine chemical probes in network characterisation of NBR vulcanizates 
Kiroski, D; Sims, J; Packham, DE; Gregory, AL 
1997 
1 
Kautschuk Gummi Kunststoffe
ISSN: 0022-9520 
50 
10 
716-720 
English 
WOS:A1997YC53800005 
Disulphide and polysulphide crosslinks in sulphur-cured gum vulcanizates of nitrile butadiene rubber (NBR) could be cleaved by treating with hexane-1-thiol (1M) in piperidine for 72 h under nitrogen at 23°C while polysulphide crosslinks could be cleaved by treating with propane-2-thiol (0.4M) and piperidine (0.4M) in toluene for 2 h. Crosslink cleavage can result in freeing significant amounts of the NBR itself from the network: unless this is accounted for, a misleading value of crosslink density will result. Within practical sulphur and accelerator loading an increase in sulphur:accelerator ratio results in an increase in total crosslink density and the proportion of di- and polysulphide crosslinks. An increase in vulcanization temperature gives rise to networks of lower total crosslink density with a higher proportion of monosulphide crosslinks. 
nitrile rubber; crosslink structure; chemical probes; thiol probes; cleavage