Tetramethylthiuram Research Articles

The Effect of Various Combinations of Accelerators on the Physical Properties of Rubber Vulcanizates

Systems of combined accelerators comprising 2-mercaptobenzothiazol (MBT), dibenzothiazyl disulfide (MBTS), tetramethyl thiuram monosulfide (TMTM) and diphenyl guanidine (DPG) were used to study the physical properties of rubber vulcanizates. The study was conducted by divisioning the work into 3 sets; namely set 1, set 2 and set 3 whereby the combinations of the accelerators were carried out in such a way that only the ratios were subject to changes. We found that there was a synergistic effect on the vulcanizates properties leading to, higher or lower property values from the normally expected ones demonstrating the role of crosslink on tensile modulus, hardness and resilience.

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

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 ZnSO4 and ZDMC, is responsible for approximately 15 mol % of the amount of ZDMC. Other products that were detected are CO2, CS2, and tetramethylurea, whereas ZnSO3, 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. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1247–1257, 1999

Effect of stearic acid concentration on the reversion behavior of epoxidized natural rubber

The effect of stearic acid concentration on the reversion behavior of epoxidized natural rubber (ENR 25 and ENR 50) was carried out in the temperature range of 150–180°C and 0.5–14.5 phr of stearic acid loading. Three common accelerators; namely, zinc dimethyldithiocarbamate (ZDMC), tetramethylthiuram disulfide (TMTD), and N-morpholinylbenzothiazole-2-sulfenamide (MBS) and conventional sulfur vulcanization system was used throughout the study. A Monsanto oscillating-disk rheometer was used to determine the reversion behavior of the rubber. Results indicate that for all the accelerators used, reversion decreases with increasing stearic acid concentration. The rate of decrease is more gradual up to about 6.5 phr of stearic acid, after which a rapid drop of reversion is observed for both ENR 25 and ENR 50. This observation is attributed to the increasing amount of mono- and disulfidic crosslinks as a result of desulfuration of polysulfidic crosslinks. The higher the stearic acid loading, the greater is the retardation effect on vulcanization; that is, more time is available for desulfuration. Increasing temperature would increase the reversion of the rubber vulcanizate because of the increase in thermal energy to decompose more crosslinks, including mono- and ether crosslinks for temperature higher than 160°C. ZDMC (an ultrafast accelerator) gives a higher reversion than MBS (a delay-action accelerator), because desulfuration occurs more slowly in the former system. The observed decrease in reversion as stearic acid concentration increases is technologically importance, because the aging property of the rubber vulcanizate is significantly improved. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1165–1169, 1999

Effect of carboxylic acids on 2-bisbenzothiazole-2,2?-disulfide- and tetramethylthiuram disulfide-accelerated sulfur vulcanization. III. Reaction between accelerators and zinc salts of the acids

Stearic and benzoic acids were heated with 2-bisbenzothiazole-2,2'-disul-fide (MBTS)/sulfur/ZnO and tetramethylthiuram disulfide (TMTD)/sulfur/ZnO isothermally at 150°C and in a DSC at 2.5°C/min, in the absence of rubber. The acids readily reacted with ZnO, and at vulcanization temperatures, little or no free acid remains. The zinc salts are less reactive toward the accelerators and accelerator polysulfides than are the acids, although with benzoic acid/ZnO, MBTS formulations produced small amounts of the accelerator-acid complex 2-benzoylthiobenzothiazole and 2-mercaptobenzothiazole, while with TMTD formulations, limited 2-benzoyldimethyldithiocarbamate formation was detected. These small amounts of the reaction can be attributed to the incomplete consumption of benzoic acid, zinc benzoate restricting the access of benzoic acid to ZnO particles. Although conversion of MBTS and TMTD to accelerator-acid complexes is limited, the zinc salts do promote the slow decomposition of MBTS and TMTD above 150°C. It can be concluded that in the presence of ZnO carboxylic acids should not detrimentally effect the vulcanization reaction.

Effect of carboxylic acids on 2-bisbenzothiazole-2,2?- disulfide- and tetramethylthiuram disulfide-accelerated sulfur vulcanization. I. Reaction between the acids and accelerators

Benzoic and stearic acids are shown to react with 2- bisbenzothiazole-2,2′-disulfide (MBTS) and its polysulfides (MBTP) at vulcanization temperatures to form acid-accelerator complexes 2-benzoylthiobenzothiazole (BzM) and stearicthiobenzothiazole (StM), respectively. At higher temperatures MBTS, MBTP, BzM, and StM are decomposed by the acids. Analogous reactions are observed with tetramethylthiuram disulfide (TMTD) and its polysulfides (TMTP). Lesser amounts of acid-accelerator complexes 2-benzoyldimethyldithiocambamate and stearicdimethyldithiocarbamate are formed, but TMTP are more susceptable to decomposition at higher temperatures. The destruction of MBTP and TMTP by carboxylic acids will reduce the concentration of accelerator polysulfides available in compounds, and should impact negatively on vulcanization. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 999–1006, 1999

Orchard Groundcover Management Systems Affect Meadow Vole Populations and Damage to Apple Trees

Meadow vole (Microtus pennsylvanicus Ord) populations, feeding activity and damage to young apple (Malus ×domestica Borkh.) trees were monitored for several years in a New York orchard by direct observation, trap counts, and a feeding activity index in various groundcover management systems (GMSs). Meadow vole population density differed among GMSs, with consistently higher densities and more trees damaged in crown vetch (Coronilla varia L.), hay-straw mulch, and red fescue (Festuca rubra L.) turfgrass tree-row strips. Vole densities were high in autumn and low in spring each year. Anticoagulant rodenticides and natural predation did not adequately control voles in GMSs providing favorable habitat. Groundcover biomass per m2 was weakly correlated with vole densities in 2 of 3 years, while the percentage of soil surface covered by vegetation was not significantly correlated with vole populations. Applications of thiram fungicide in white latex paint were better than no protection, but less effective than 40-cm-high plastic-mesh guards for preventing vole damage to tree trunks. A combination of late-autumn trapping, close and consistent mowing of the orchard floor, trunk protection with mesh guards, contiguous habitat for vole predators, and herbicide applications within the tree rows provided effective control of meadow-vole damage to trees at this orchard during 3 years without applications of rodenticide baits. Chemical names used: Tetramethylthiuram disulfide (thiram)

Comparison of Rhizoctonia zeae Isolates from Florida and Ohio Turfgrasses

The growth responses of 10 Rhizoctonia zeae isolates, obtained from turfgrasses in Florida and Ohio, to four temperatures (20, 25, 30, and 35 °C) and seven fungicides at four concentrations (0, 1, 10 and 100 μg·mL-1 a.i.) were compared. Greenhouse pathogenicity tests were conducted using hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy]. Optimal temperature for growth for all isolates was 30 °C. Growth of R. zeae isolates from both geographic locations was severely limited (>75%) at 20 °C. All R. zeae isolates were insensitive to the benzimidazole fungicides, benomyl and thiophanate methyl. Their sensitivities to iprodione, mancozeb, and quinotzene fungicides were similar. The Florida isolates were more sensitive to chlorothalonil, and the Ohio isolates to thiram. All isolates were pathogenic to hybrid bermudagrass. Chemical names used: methyl 1-(butylcarbamoly)-2-benzimidazolecarbamate (benomyl); dimethyl 4,4′-O-phenylene bis(3-thioallophanate) (thiophanate methyl); pentachloronitrobenzene (quintozene); 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidinecarboxamide (iprodione); tetrachloroisophtalonitrile (chlorothalonil); tetramethylthiuram disulfide (thiram); manganese ethylenebisdithiocarbamate (mancozeb).

Effect of carboxylic acids on 2-bisbenzothiazole-2,2?-disulfide- and tetramethylthiuram disulfide-accelerated sulfur vulcanization. IV. Vulcanization of polyisoprene compounds with ZnO

The effect of benzoic and stearic acids on 2-bisbenzothiazole-2,2′-disulfide (MBTS)- and tetramethylthiuram disulfide (TMTD)-accelerated sulfur vulcanization of polyisoprene compounds, containing ZnO, was studied at 150°C. In the presence of ZnO, the acids are rapidly converted to their zinc salts that, unlike the acids, do not attack accelerator polysulfides and, instead, promote vulcanization. The addition of accelerator polysulfides to the chain is not affected by zinc salts, but the rate of crosslinking of pendent groups is facilitated. In MBTS vulcanization, the promotion of crosslinking reactions reduces the number of pendent groups involved in cyclization reactions and higher crosslink densities are attained. In TMTD compounds, crosslink densities are increased on addition of ZnO and of ZnO/carboxylic acids. A mechanism is suggested to account for the promotion of crosslinking by the zinc salts. Bis(2-mercaptobenzothiazolo)zinc(II) and bis(dimethyldithiocarbamato)zinc(II) can act similarly to zinc benzoate or stearate to promote the crosslinking of pendent groups, but are less efficient. With benzoic acid, a limited attack by zinc benzoate on TMTP leads to a slightly lower increase in crosslink density than is achieved with the addition of ZnO alone. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1021–1030, 1999

Effects of tetramethylthiuram disulphide (thiram) on adenine nucleotide (ATP, ADP, AMP) levels in the ciliate Tetrahymena pyriformis

Axenic cultures of Tetrahymena pyriformis GL populations were exposed to 0.40 μg/mL of tetra methylthiuram disulphide (TMTD). Doubling times and ATP, ADP and AMP levels were followed on control and treated populations at various cell densities during the exponential growth phase. For the control populations, the average generation time was 171.9 min and ATP levels were 2–8×10−14 mol/cell. For the treated populations, growth was reduced and the populations with the highest densities were more sensitive than populations treated with TMTD at the early stage of the exponential growth phase. For treated populations, ATP and ADP concentrations showed significant differences compared to the control populations. Mechanisms compensating the action of the TMTD have been observed with treated populations at 25,000 cells/mL density. Unfortunately AMP levels were unstable within control populations showing no differences with those from treated populations. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 409–413, 1999

Effects of tetramethylthiuram disulphide (thiram) on adenine nucleotide (ATP, ADP, AMP) levels in the ciliateTetrahymena pyriformis

Axenic cultures of Tetrahymena pyriformis GL populations were exposed to 0.40 μg/mL of tetra methylthiuram disulphide (TMTD). Doubling times and ATP, ADP and AMP levels were followed on control and treated populations at various cell densities during the exponential growth phase. For the control populations, the average generation time was 171.9 min and ATP levels were 2–8×10−14 mol/cell. For the treated populations, growth was reduced and the populations with the highest densities were more sensitive than populations treated with TMTD at the early stage of the exponential growth phase. For treated populations, ATP and ADP concentrations showed significant differences compared to the control populations. Mechanisms compensating the action of the TMTD have been observed with treated populations at 25,000 cells/mL density. Unfortunately AMP levels were unstable within control populations showing no differences with those from treated populations. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 409–413, 1999

Synthesis of core-shell type microsphere with reactive seed microspheres

Monodispersed poly(methyl methacrylate) (PMMA) particles (seed microspheres) were synthesized with the living radical initiators, tetramethylthiuram disulfide, or p-xylene dimethyldithiocarbamate by suspension polymerization in water media with and without divinyl benzene as a crosslinker. Monodispersed spherical microspheres with PMMA core–polyacrylamide shells were synthesized by UV irradiation to the seed microsphere–acrylamide aqueous solution. The content and the molecular weight of the polyacrylamide shell chain were controlled by changing the acrylamide feed and irradiation time of the UV light. The microspheres became dispersible to water after the UV irradiation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 211–216, 1998

Analysis of micronuclei and DNA single-strand breaks in mouse splenocytes and peripheral lymphocytes after oral administration of tetramethylthiuram disulfide (Thiram)

The fungicide thiram (tetramethylthiuram disulfide, TMTD) was administered by repeated oral intubations to groups of male B6C3F 1 mice at 100, 300 and 900 mg/kg body weight for 4 consecutive days, or at 300 mg/kg for 8 and 12 days. 24 hr after the last treatment animals were killed, and splenocyte cultures were set up for the analysis of micronuclei by the cytokinesis-block method. DNA single strand breaks ( ssb) and alkali labile sites were also analysed by the single cell gel electrophoresis (Comet) assay in splenocytes and lymphocytes of animals receiving the 8- and 12-day treatments. Parallel experiments with human peripheral lymphocytes were carried out to assess the ability of thiram to induce micronuclei and DNA ssb and alkaline labile sites under in vitro conditions. No significant increase of micronucleated splenocytes was observed in treated animals, despite some evidence of treatment-related cellular toxicity. A borderline excess of DNA damage was suggested by the Comet assay on circulating lymphocytes, whereas negative results were obtained with splenocytes. In vitro, positive results with both genetic end points were obtained in assays with human lymphocytes in the dose ranges 0.5–24 μg/ml and 0.1–8 μg/ml for micronucleus and Comet assays, respectively. These results suggest that thiram, despite its established genotoxicity in vitro, is devoid of appreciable clastogenic and/or aneugenic activity in vivo after oral administration to mice at the maximum tolerated dose.

Effects of advancement on nucleic acids in sugarbeet (Beta vulgaris) seeds

AbstractSugarbeet (Beta vulgaris) seeds which had undergone an advancement treatment germinated more quickly and showed greater germination in a standard test at 9°C than seeds which had been steeped in water. Both treatments included the fungicide, thiram (tetramethyl thiuram disulphide). Advanced seeds also emerged more quickly and showed higher establishment in the field. The levels of extractable high molecular weight (HMW) RNA and DNA from advanced, thiram-steeped and untreated seeds were compared. Advanced seeds contained significantly (P > 0.05) more HMW RNA and DNA than thiram-steeped or untreated seeds. Extractable DNA levels were higher from thiram-steeped seeds than untreated seeds but not significantly so. Cell-cycle studies on advanced seeds demonstrated an increase from 2% to 24% of root-tip nuclei with DNA contents of 4C and above. This indicates that DNA replication occurred during the advancement treatment. There was no evidence of cell division occurring, indicating that: (1) advanced seeds were arrested post-S-phase and (2) the period following DNA synthesis in sugarbeet seeds is desiccation tolerant.

Influence of tetramethylthiuram disulfide on polymerizations of styrene and methyl methacrylate—I. Influence on kinetics of polymerization

Relations for the total polymerization rates for the polymerization of styrene and methyl methacrylate in the presence of tetramethylthiuram disulfide were derived. The participation of tetramethylthiuram disulfide radicals in mutual and cross-termination reactions was characterized by complex constants B and C, respectively. The differences in the activation energies for the tetramethylthiuram disulfide decomposition and the first addition of tetramethylthiuram disulfide radicals to monomer molecules, in styrene and methyl methacrylate polymerizations, showed the possibility of partly different mechanisms for the removal of tetramethylthiuram disulfide radicals in these systems.

Sulfur Vulcanization of Simple Model Olefins, Part V: Double Bond Isomerization during Accelerated Sulfur Vulcanization as Studied by Model Olefins

Abstract The sulfur vulcanization of unsaturated rubber has been studied with the use of various olefins as simple, low-molecular models. By treatment of these olefins with a mixture of zinc oxide, sulfur, and tetramethylthiuram disulfide (TMTD) at 140 °C, a mixture of dialkenyl sulfides is obtained mimicking crosslinked rubber. Isomerization of the double bond may take place during this reaction, depending on the olefin used. The position of the double bond is on the one hand determined by crosslink formation mechanisms, and on the other hand by isomerization, which takes place at higher temperatures. The position of the equilibrium between isomeric alkenyl sulfides is determined by the increased stability of the sulfide which in itself results from an increased degree of alkyl substitution at the unsaturation. Due to the isomerization reaction, at higher temperatures no mechanism for crosslink formation can be discerned. At room temperature, however, a radical mechanism appears to be predominant during the vulcanization process.

Silver Extraction for Pollution Control of Photographic Fixing Solution with Tetramethylthiuram Disulfide

Abstract Silver recovery from photographic fixing solutions can be performed by solvent extraction with thiuram disulfides. Tetramethylthiuram disulfide (TMTDS) was selected for further studies because it had the highest distribution ratio among the three extractants. Its selectivity for silver extraction from a thiosulfate medium and from an analytical photographic fixing solution were evaluated. A 1 : 1 silver(I)–TMTDS complex is formed. For a one-stage and one-hour silver(I) extraction process, a 96% recovery was obtained from an analytical fixing solution containing 1 g dm−3 silver(I), starting with a 0.02 M (1 M = mol dm−3) TMTDS solution. The possible extraction mechanism involves the reduction of TMTDS in the presence of thiosulfate ions, followed by chelation of the silver(I) with the reduced TMTDS. Effective stripping can be performed by using 3 M hydrochloric acid. By dilution of the fixing solution with water (1 : 1), and the use of 0.1 M TMTDS, recycling of the organic phase between the extraction and stripping stages for silver extraction can be achieved in a few times. The results for the analytical solutions were further shown to be applicable to a black and white photographic industrial solution.

Determination of tetramethylthiuram disulfide (Thiram) in river water by high-performance liquid chromatography: Micellar versus conventional reversed phase chromatography

After a comparative study of conventional reversed phase and micellar liquid chromatography a method is described for the determination of the fungicide thiram in river water based on the use of micelles of CTAB. The method involves the extraction/concentration of thiram with a C18 cartridge followed by separation on a C18 reversed-phase column with a mobile phase of 20% (v/v) acetonitrile/0.01 M CTAB in phosphate buffer (pH-6.3), and detection at 254 nm. The method allows the determination of thiram in the presence of other water-soluble dithiocarbamate fungicides (nabam, ziram and ferbam) with a limit of detection of 36 pg mL−1 for a typical 20-fold preconcentration.

Tetramethylthiuram disulfide and 2-mercaptobenzothiazole as binary accelerators in sulfur vulcanization. III. Vulcanization of polyisoprene in the absence of ZnO

Polyisoprene was vulcanized with binary accelerator systems comprising mixtures of the zinc salts of tetramethylthiuram disulfide (TMTD) and 2-mercaptobenzothiazole (MBT). Samples were heated in a DSC at a programmed rate, the reaction was stopped at points along the thermal curve, and the system was analyzed. Extractable curatives and reaction intermediates were analyzed by HPLC and the crosslink density of samples measured by swelling. DSC curves for the different systems displayed similar characteristics and their similarity to the curve obtained with the zinc salt of TMTD rather than to the curve obtained with the zinc salt of MBT suggested that the reaction was dominated by the former accelerator. This conclusion was supported by HPLC analyses of extractable curatives. A reaction mechanism for the binary system is discussed. © 1996 John Wiley & Sons, Inc.

Tetramethylthiuram disulfide and 2‐mercaptobenzothiazole as binary accelerators in sulfur vulcanization. III. Vulcanization of polyisoprene in the absence of ZnO

Tetramethylthiuram disulfide and 2‐mercaptobenzothiazole as binary accelerators in sulfur vulcanization. III. Vulcanization of polyisoprene in the absence of ZnO

Tetramethylthiuram disulfide and 2-mercaptobenzothiazole as binary accelerators in sulfur vulcanization. IV. Vulcanization of polyisoprene in the presence of ZnO

Polyisoprene was vulcanized with binary accelerator systems comprising mixtures of the zinc salts of tetramethylthiuram disulfide (TMTD) and 2-mercaptobenzothiazole (MBT). Samples were heated in a DSC at a programmed rate, the reaction was stopped at points along the thermal curve, and the system was analyzed. Extractable curatives and reaction intermediates were analyzed by HPLC and the crosslink density of samples measured by swelling. DSC curves for the different systems displayed similar characteristics and their similarity to the curve obtained with the zinc salt of TMTD rather than to the curve obtained with the zinc salt of MBT suggested that the reaction was dominated by the former accelerator. This conclusion was supported by HPLC analyses of extractable curatives. A reaction mechanism for the binary system is discussed. © 1996 John Wiley & Sons, Inc.