Standard Test Method for Colorimetric/Spectrophotometric Procedure to Quantify Extractable Chemical Dialkyldithiocarbamate, Thiuram, and Mercaptobenzothiazole Accelerators in Natural Rubber Latex and Nitrile Gloves

Importancia y uso:

5.1  Dialkyldithiocarbamates (DTCs), benzothiazoles, and thiurams are often used as vulcanization accelerators in NRL products. Zinc DTC accelerators are added either directly or are formed in situ during the vulcanization process via reaction between a thiuram(s) and zinc oxide. DTCs, benzothiazoles, and thiurams have been detected in leachates from medical devices made of rubber such as gloves. Studies have shown these chemicals can cause allergic contact dermatitis. A simple selective method to monitor rubber accelerator levels in rubber extracts would be useful for quality control, product screening and research.

5.2 This colorimetric assay measures dialkyldithiocarbamates, including zinc dialkyldithiocarbamates (ZDTC), mercaptobenzothiazole (MBT) and thiurams as a total thiol vulcanization accelerator level in rubber products. A UV spectrophotometer with detection at 320 nm is used to measure the ZDTC, mercaptobenzothiazole and thiurams. Sample extracts diluted at 1:20 prior to measurement on the spectrophotometer is usually sufficient to quantify the residual accelerator level from most commercially available rubber gloves; however, sample dilution can be adjusted (from neat extract to > 1:20 dilution) based on analytical needs. Thiurams and ZDTCs complex with cobalt turning the extract to a concentration-dependent shade of green. ZDTCs reacts quickly while thiurams react very slowly (requiring a heat catalyst). Mercaptobenzothiazole does not complex to Co(III), however, it absorbs strongly at 320 nm. It can be distinguished from both ZDTCs and thiurams by its strong absorbance at 320 nm without the cobalt dependent visible green color. Cobalt complexed thiurams and ZDTCs, but not MBT, also have and absorbance at 370 nm (2).

Subcomité:

D11.40

Referida por:

D7103-19R23

Volúmen:

09.02

Número ICS:

83.040.20 (Rubber compounding ingredients)

Palabras clave:

colorimetric; mercaptobenzothiazole; spectrophotometric; thiol accelerator; thiuram; zinc dialkyldithiocarbamate;