N,N?-Pentamethylenethiuram disulfide- andN,N?-pentamethylenethiuram hexasulfide-accelerated sulfur vulcanization. II. Relative stability ofN,N?-pentamethylenethiuram disulfide and tetramethylthiuram disulfide with respect to amine formation

Reyneke-Barnard, C. P.; Gradwell, M. H. S.; McGill, W. J.

doi:10.1002/1097-4628(20000919)77:12<2732::aid-app210>3.0.co;2-t

Cited by 14 publications

(15 citation statements)

References 21 publications

(33 reference statements)

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“…Accordingly, ODA is ‘extracted’ from the interlayer regions for this complexion and, as a consequence, the layers collapse, and re‐aggregate. Many suggestions for the formation of such a Zn–sulfur–amine complex can be found in the literature 27–29. Nevertheless, if this hypothesis is correct, the compound produced in the internal mixer in the presence of ZnO and stearic acid should generate a more pronounced migration of the amine modifier in the rubber matrix.…”

Section: Resultsmentioning

confidence: 99%

Characteristics of ethylene propylene diene monomer rubber/organoclay nanocomposites resulting from different processing conditions and formulations

Gatos

Thomann

Karger‐Kocsis

2004

Polymer International

106

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Several parameters which affect the nanocomposite formation in a sulfur‐cured ethylene propylene diene rubber (EPDM) containing 10 phr organoclay (montmorillonite modified with octadecylamine; MMT–ODA), were investigated. The parameters varied were linked to processing (mixer type, temperature) and rubber recipe (compatibilizer, accelerator). Increasing temperature and high shear mixing (internal mixer instead of open mill) improved the mechanical performance of the rubber nanocomposites. A more pronounced effect was achieved by using polar EPDM rubbers (maleic anhydride and glycidyl methacrylate grafted version) as compatibilizer. Among the accelerators, zinc diethyldithiocarbamate proved to be most suitable. The microstructure of the rubber/organoclay systems was studied by X‐ray diffraction, transmission electron microscopy and scanning electron microscopy. Organoclay intercalation/exfoliation was accompanied by its more or less severe confinement (reaggregation, deintercalation). This was traced to a partial or full removal of the ODA intercalant from the clay galleries via the formation of a zinc complex in which amine groups of the ODA and sulfur participated. Copyright © 2004 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 99%

Characteristics of ethylene propylene diene monomer rubber/organoclay nanocomposites resulting from different processing conditions and formulations

Gatos

Thomann

Karger‐Kocsis

2004

Polymer International

106

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“…CPTU forms after an induction period and at a fairly constant although slightly slower rate than in the absence of rubber. 16,19 Its formation is clearly independent of the vulcanization process, and is catalyzed by amines formed in the system, as discussed in an earlier articles. 16 The slower formation of CPTU can be attributed to competition between amine attack on CPTP and the reaction of CPTP with the polymer chain to form thiuram-terminated pendent groups.…”

Section: Cptu Formationmentioning

confidence: 71%

“…No CPTU was detected during vulcanization of IR/CPTP6 under vacuum. Because the presence of Hpmtc was found to promote the formation of CPTU, 16 the absence of CPTU in IR/CPTP6 vulcanized under vacuum confirms the absence of Hpmtc in the rubber film. The net effect of the removal of Hpmtc, by vulcanizing in a vacuum, was to lower the crosslink density (5.36 ϫ 10 Ϫ5 vs. 0.69 ϫ 10 Ϫ5 mol/mL), and thereby confirming the important role Hpmtc and other alkyldithiocarbamic acids play in the vulcanization process.…”

Section: Thiuram-terminated Pendent Group Formationmentioning

confidence: 94%

“…Although the decomposition of TMTD to TMTU at vulcanization temperatures has been reported, 1,14,15 other authors 16 -18 claim that it is stable at vulcanization temperatures, and TMTU is only formed in vulcanizates, i.e., it results from reactions associated with crosslinking. However, N,NЈ-dipentamethylenethiuram disulfide (CPTD) degrades to N,NЈ-pentamethylenethiourea (CPTU) at vulcanization temperatures 16,19 and, should it also form as a result of the crosslinking process, accelerated CPTU formation can be expected when CPTD and CPTD/sulfur are added to rubber.…”

Section: Introductionmentioning

confidence: 99%

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N,N′‐Pentamethylenethiuram disulfide and N,N′‐pentamethylenethiuram hexasulfide accelerated sulfur vulcanization. III. Vulcanization of polyisoprene and 2,3‐dimethyl‐2‐butene in the absence of ZnO

Reyneke-Barnard

Gradwell

McGill

2000

J. Appl. Polym. Sci.

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Polyisoprene and model compound, 2,3-dimethyl-2-butene, were vulcanized with N,NЈ-dipentamethylenethiuram disulfide (CPTD), CPTD/sulfur and N,NЈ-dipentamethylenethiuram hexasulfide (CPTP6) in the absence of ZnO and residual extractable curatives and reaction intermediates analyzed by HPLC at various stages of the reaction. Accelerator polysulfides, required for the formation of accelerator-terminated polysulfidic pendent groups, form rapidly, or are present from the outset in the case of CPTP6. Model compounds confirm the formation of thiuram-terminated polysulfidic pendent groups as intermediates in the vulcanization process. Removal of pentamethylenedithiocarbamic acid (Hpmtc) from the system during heating delays the onset of vulcanization and leads to very low crosslink densities. Rubbers heated under vacuum can subsequently be crosslinked by the addition of zinc stearate, pointing to the presence in the compound of thiuram-terminated pendent groups. However, such pendent groups do not readily crosslink on their own, and hydrogen-terminated polysulfidic pendent groups, formed by the reaction of sulfurated Hpmtc with the polymer, are suggested to be involved in the crosslink formation. N,NЈ-Pentamethylenethiurea forms in the vulcanizate, but is not as product of crosslinking reactions, rather of CPTD degradation. The data are discussed with respect to mechanisms proposed in the literature for crosslinking, and it is concluded that the data support recently formulated mechanisms in which crosslinking involves reaction between thiuram and thiol-terminated pendent groups, with Hmptc playing and essential role in the overall process.

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“…Using the method of melt intercalation to prepare rubber/clay nanocomposites, dispersion of clay layers is always a hotspot, and there are a few investigations focusing on the vulcanization additives, like accelerant zinc dimethyldithio carbamate (PZ) 15 and zinc oxide (ZnO). [16][17][18] However, only a few literatures discuss the effect of the characteristics of rubbers, 19,20 and no literature investigates the combined effect of additives and characteristics of rubber matrix.…”

Section: Introductionmentioning

confidence: 99%

The role of rubber characteristics in preparing rubber/clay nanocomposites by melt compounding

Zhang

et al. 2008

J of Applied Polymer Sci

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Rubber/organic clay (OC) nanocomposites were produced by melt blending. Polar or unsaturated matrices (e.g., NBR and SBR) could easily enter into OC layers, whereas using nonpolar unsaturated rubber (EPDM), without other additives' help, intercalation structure could not be directly obtained. For the EPDM system, an intercalated structure was observed in presence of stearic acid (SA) for composites composed of SA and OC. Transmission electron microscopy observation showed that the dispersion of clay in nonpolar saturated rubber matrix was much poorer than that in polar or unsaturated matrix. The same effect of polar matrix was confirmed by comparison between IIR/OC and BIIR/OC systems. Moreover, using OC pretreated by SA (S-OC), the dispersion of clay was obviously improved in the investigated nanocomposites, due to the intercalation of SA into OC interlayers. Especially in the nonpolar saturated EPDM system, the intercalation structure could be easily observed. Relative to the corresponding nanocomposites using OC, tensile strengths and the stresses at low strain of NBR and SBR based nanocomposites with S-OC were significantly improved; while with EPDM nanocomposite, using S-OC, only tensile strengths were improved but the stresses at low strain were almost the same, which should be related to the different interfacial force between OC and different rubber matrices.

show abstract

N,N?-Pentamethylenethiuram disulfide- andN,N?-pentamethylenethiuram hexasulfide-accelerated sulfur vulcanization. II. Relative stability ofN,N?-pentamethylenethiuram disulfide and tetramethylthiuram disulfide with respect to amine formation

Cited by 14 publications

References 21 publications

Characteristics of ethylene propylene diene monomer rubber/organoclay nanocomposites resulting from different processing conditions and formulations

Characteristics of ethylene propylene diene monomer rubber/organoclay nanocomposites resulting from different processing conditions and formulations

N,N′‐Pentamethylenethiuram disulfide and N,N′‐pentamethylenethiuram hexasulfide accelerated sulfur vulcanization. III. Vulcanization of polyisoprene and 2,3‐dimethyl‐2‐butene in the absence of ZnO

The role of rubber characteristics in preparing rubber/clay nanocomposites by melt compounding

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