Search

This article illustrates the reclaiming of guayule natural rubber (GNR) vulcanizate by bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT), and as-grown reclaim rubber facilitates the silica dispersion in GNR product application without adding any coupling agent. This article deals with the performance evaluation of silica-filled revulcanizates with promising application in green tire. The extent of reclaiming was monitored through the measurement of sol content, cross-link density, Mooney viscosity, and degree of reclaiming. The differential scanning calorimetry study was carried out to evaluate the fraction of immobilized polymer chains and its dependence on cross-link density of the vulcanizates. The Fourier transform infrared study and also sulfur analysis independently indicate the attachment of the fragmented TESPT with the polymer chain and cross-link bonds. The study of mechanical properties clearly shows that in revulcanized GNR, the optimum property is achieved when reclaiming time is set for 40 min. The effect of reclaiming time on dynamic mechanical behavior such as storage modulus and loss tangent was studied. The scanning electron microscopy studies show the coherency and homogeneity of silica-filled revulcanize rubber with reclaiming time. [ABSTRACT FROM AUTHOR]

Ethoxy functionalized devulcanize natural rubber (DeVulcNR) is used as compatibilizer for silica/graphene oxide (SiO2@GO) hybrid fillers in the styrene butadiene rubber (SBR) to fabricate SBR composites. The dispersion behavior of SiO2@GO hybrid filler was investigated through scanning electron microscopy (SEM) analysis of the tensile fracture surface along with the broken rubber surface developed by plunging into liquid nitrogen. The rubber–filler interfacial interactions were evaluated through the measurement of equilibrium swelling experiment, fraction of immobilized polymer chain by DSC study, FTIR analysis, and molecular dynamics simulation. The results reveal that in the presence of DeVulcNR, the rubber–filler interaction is enhanced compared with that of the control formulations containing only SBR. SiO2@GO hybrid‐filler shows synergistic effect on the mechanical properties of the composites in the presence of DeVulcNR. The improved mechanical properties of the SiO2@GO hybrid filler rubber composites may be due to chemical interaction among the functional groups of SiO2 and GO with the DeVulcNR. Further, XRD study indicates that there is no significant layer‐by‐layer restack of GO in the SBR/DeVulcNR composites. The higher storage modulus and lower tan δ of the SiO2@GO hybrid filler rubber composites show superior interfacial interaction between rubber and filler compared with that of the control formulations. POLYM. COMPOS., 40:E1559–E1572, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Mechanochemically devulcanized styrene‐butadiene rubber, prepared by bis[3‐(triethoxysilyl)propyl]‐tetrasulfide, was blended with fresh styrene‐butadiene rubber. The ultimate properties of the blend vulcanizate depend on a three‐dimensional network structure formed during vulcanization which relies mainly on the accelerator and the vulcanizing system used during compounding. The effect of monosulfide, disulfide, and poly sulfide cross‐links, which primarily gets controlled by different accelerators such as N‐cyclohexyl‐benzothiazyl‐sulfenamide (CBS), tetramethylthiuram disulfide, 2‐mercaptobenzothiazol, and N‐tert‐butyl‐2‐benzothiazyl‐sulfonamide on mechanical, thermal, and dielectric behavior of the blend vulcanizates, was studied. The results indicate that the semi‐efficient CBS vulcanizate has superior mechanical and thermal properties. Therefore, the effect of accelerator to sulfur ratio, that is, (accelerator/sulfur) on the properties of the blend vulcanizates was determined. It is to highlight that a distinctive correlation is observed between the cross‐link types and the fraction of immobilized polymer chains of the blend vulcanizates. Further, the effect of cross‐link types on segmental dynamics of the blend vulcanizates was studied through broadband dielectric spectroscopy. The SEM micrographs indicate the homogeneity of the blend vulcanizates. [ABSTRACT FROM AUTHOR]

These days sustainable ecosystem warrants cleaner, safer and easier mobility of resources in a production cycle. In a response of such call, in this present work, sulphur crosslinked natural rubber (NR) is successfully devulcanized using bis(3-triethoxysilyl propyl) tetrasulfide (TESPT) - a dual function disulfide chemical. It is observed that the mono-, di- and poly sulfide crosslinks, those determine the final performance of the composites, can be controlled by using various chemicals like N-cyclohexyl-benzothiazyl-sulphenamide (CBS), tetramethylthiuram disulfide (TMTD), 2-mercaptobenzothiazol (MBT) and N-tert-butyl-2-benzothiazyl-sulphonamide (TBBS). Subsequently different vulcanizing systems like conventional, efficient and semi efficient vulcanization systems were also studied. Furthermore, in the optimization of vulcanizing system, semi-EV showed the highest mechanical properties compared to that of the CV and EV system. The study shows a unique correlation between the crosslink density, (mono-, di- and polysulfide) and the mole % uptake of the solvent with time. It also shows the dependence of the fraction of immobilized polymer chain and the segmental dynamics of the composites on the crosslink density. [ABSTRACT FROM AUTHOR]

Devulcanized natural rubber (DeVulcNR) was produced from NR vulcanizate in an open roll mixing mill by using bis(3-triethoxysilyl propyl) tetrasulfide (TESPT), a novel devulcanizing agent. The versatility of the proposed devulcanizing agent TESPT is that it acts as a devulcanizing agent during devulcanization and as a coupling agent during dispersion of silica filler in devulcanize rubber compound. The extent of devulcanization was monitored through the measurements of sol content, gel content, crosslink density, molecular weight between crosslinks, Mooney viscosity of devulcanized rubber and degree of devulcanization as a function of devulcanization time and the concentration of TESPT. The study of extent of devulcanization by monitoring the above mentioned parameters clearly indicate that the optimum concentration of TESPT is 6 mL. Therefore, for further study DeVulcNR is prepared using 6 mL TESPT and designated as DeVulcNR-6 to optimize the devulcanization time. Determination of the fraction of immobilized polymer chains of DeVulcNR-6 by differential scanning calorimetry (DSC) study indicates that with sol content the fraction of immobilized polymer chains decreases due to increasing molecular weight between crosslinks. To get an idea about the application of DeVulcNR in product formulation revulcanization characteristics in the presence of silica filler were studied. The optimum cure time decreases whereas cure rate increases with devulcanization time. The mechanical properties e.g., modulus at 50% and 100% elongation, tensile strength and elongation at break increases with devulcanization time upto 40 min. To see the reinforcement of silica filler, the mechanical properties of ReVulcNR-6 with silica is compared to that of the ReVulcNR-6 without silica. The mechanical property and thermal behavior data clearly indicates that the optimum time for devulcanization is 40 min. Scanning electron microscopy (SEM) studies further show the coherency and homogeneity of DeVulcNR-6 in the revulcanizate when devulcanization is carried out by optimum TESPT concentration 6 mL and devulcanization time 40 min. [ABSTRACT FROM AUTHOR]