The Limiting Value of Dithiocarbamate Formation during the Vulcanization of Natural Rubber with Thiuram Disulfides

Scheele, Walter; Lorenz, Otto

doi:10.5254/1.3542603

Cited by 4 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A maximum crosslink density of 8.30 × 10 −5 mol/mL was reported at 190°C 4. Studies by Moore and Watson3 confirmed the findings by Scheele and Lorenz14 that the rate of ZDMC formation paralleled the rate of crosslinking in IR/TMTD/ZnO and NR/TMTD/ZnO vulcanization. This implies that ZDMC is formed as a direct result of crosslink formation rather than as a precursor for crosslinks.…”

Section: Resultssupporting

confidence: 59%

See 1 more Smart Citation

A comparison of tetraethylthiuram and tetramethylthiuram disulfide vulcanization. II. Reactions in rubber

Gradwell

Grooff

2001

J of Applied Polymer Sci

View full text Add to dashboard Cite

ABSTRACT:The reactions of tetraethylthiuram disulfide (TETD) with polyisoprene were investigated under vulcanization conditions. Samples of polyisoprene compounded with various combinations of TETD, sulfur, and ZnO were heated in a differential scanning calorimeter to various degrees of vulcanization. The crosslink density of the compounds was determined by swelling, and the extractable residual curatives and reaction products were analyzed with high-performance liquid chromatography. TETD caused crosslinking to occur in the absence of added sulfur, as did tetramethylthiuram disulfide (TMTD), both sulfur donors. In the presence of sulfur, the formation of TETD polysulfides occurred immediately before the crosslinking reaction started. The TETD polysulfides were the initial crosslinking agents. The ready reaction between TETD and zinc oxide to form zinc diethyldithiocarbamic acid resulted in considerably higher crosslink densities. This greater reactivity between TETD and zinc oxide, compared with that between TMTD and zinc oxide, did not lead to any noticeable differences in the vulcanizate.

show abstract

Section: Resultssupporting

confidence: 59%

“…Scheele and Lorenz14 concluded from studies of TMTD, TETD, and tetrapropylthiuram disulfide (TPTD) that all three thiuram accelerators reacted with rubber in a similar way but that the rates differed because of steric effects.…”

Section: Introductionmentioning

confidence: 99%

A comparison of tetraethylthiuram and tetramethylthiuram disulfide vulcanization. II. Reactions in rubber

Gradwell

Grooff

2001

J of Applied Polymer Sci

View full text Add to dashboard Cite

show abstract

“…As early as 1956, Scheele and Lorenz closely investigated ZDMC formation in ZnO/TMTD vulcanizates and found limiting yields of 66% with respect to TMTD. 6 Unfortunately, this failed to account for other experimental observations, 1 and up until now the ZnO/TMTD reaction is far from completely understood.…”

Section: Introductionmentioning

confidence: 98%

The limiting value of ZDMC formation: new insight into the reaction of ZNO and TMTD

Nieuwenhuizen

Duin

Haasnoot

et al. 1999

J. Appl. Polym. Sci.

View full text Add to dashboard Cite

The reaction of ZnO and tetramethylthiuram disulfide (TMTD) was reinvestigated in detail. Under conditions where evaporation of volatiles is possible, TMTD and an excess of ZnO are found to produce bis(dimethyldithiocarbamato)zinc(II) (ZDMC) in limiting amounts close to 60 mol %, irrespective of the ratio between ZnO and TMTD. This result points to the operation of more than one route toward ZDMC. When ZnO and TMTD are reacted in closed vessels in inert atmosphere, a nucleophilic reaction of ZnO with TMTD was confirmed by GC-mass spectroscopy (MS) detection of COS and NMR observation of tetramethylthiourea (TMTU). This route is found to account for about 70 mol % of the total amount of ZDMC formed. A previously unrecognized redox reaction between ZnO, sulfur, and TMTD, furnishing ZnSO 4 and ZDMC, is responsible for approximately 15 mol % of the amount of ZDMC. Other products that were detected are CO 2 , CS 2 , and tetramethylurea, whereas ZnSO 3 , ZnS, and dioxygen were absent. Based on the latter observation, the operation of a mechanism constituting radical reduction of water by TMTD, yielding dioxygen, was excluded.

show abstract

“…Zinc perthiomercaptides are well known as ultra accelerators4, 17, 18 and can be extracted from vulcanizates cured with alkylthiuram disulfide/sulfur/ZnO formulations. However, their formation in compounds prior to the onset of crosslinking is disputed,4 and the role of an active sulfurating agent in vulcanizates with TMTD/sulfur/ZnO has been attributed to both the zinc perthiomercaptides4, 19–22 and to TMTP 1, 23.…”

Section: Introductionmentioning

confidence: 99%

Diverse Veranstaltungen

2013

Nachr Chem

View full text Add to dashboard Cite

N,N′‐pentamethylenethiuram disulfide (CPTD), CPTD/sulfur, and N,N′‐pentamethylenethiuram hexasulfide (CPTP6) were heated in a DSC at a programmed heating rate and isothermally at 140°C. Residual reactants and reaction products were analyzed by HPLC at various temperatures or reaction times. CPTD rapidly formed N,N′‐pentamethylenethiuram monosulfide (CPTM) and N,N′‐pentamethylenethiuram polysulfides (CPTP) of different sulfur rank, CPTP of higher sulfur rank forming sequentially, as reported earlier for tetramethylthiuram disulfide (TMTD). As with TMTD, the high concentration of the accelerator monosulfide that develops is attributed to an exchange between CPTD and sulfenyl radicals, produced on homolysis of CPTD. However, a different mechanism for CPTP formation to that suggested for TMTD is proposed. It is suggested that disulfenyl radicals, resulting from CPTM formation, exchange with CPTD and/or CPTP already formed, to give CPTP of higher sulfur rank. CPTD/sulfur and CPTP6 very rapidly form a similar product spectrum with CPTP of sulfur rank 1–14 being detectable. Unlike with TMTD/sulfur, polysulfides of high sulfur rank did not form sequentially when sulfur was present, CPTP of all sulfur rank being detected after 30 s. It is proposed that sulfur adds directly to thiuram sulfenyl radicals. Recombination with sulfenyl radicals, which would be the most plentiful in the system, would result in highly sulfurated unstable CPTP. CPTP of higher sulfur rank are less stable than are disulfides as persulfenyl radicals are stabilized by cyclization, and the rapid random dissociation of the highly sulfurated CPTP, followed by the rapid random recombination of the radicals, would result in the observed product spectrum. CPTP is thermally less stable than is TMTD and at 140°C decomposed rapidly to N,N′‐pentamethylenethiourea (CPTU), sulfur, and CS2. At 120°C, little degradation was observed. The zinc complex, zinc bis(pentamethylenedithiocarbamate), did not form at vulcanization temperatures, although limited formation was observed above 170°C. ZnO inhibits degradation of CPTD to CPTU. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2718–2731, 2000

show abstract

The Limiting Value of Dithiocarbamate Formation during the Vulcanization of Natural Rubber with Thiuram Disulfides

Cited by 4 publications

References 0 publications

A comparison of tetraethylthiuram and tetramethylthiuram disulfide vulcanization. II. Reactions in rubber

A comparison of tetraethylthiuram and tetramethylthiuram disulfide vulcanization. II. Reactions in rubber

The limiting value of ZDMC formation: new insight into the reaction of ZNO and TMTD

Diverse Veranstaltungen

Contact Info

Product

Resources

About