Study of the crosslink density, dynamo-mechanical behaviour and microstructure of hot and cold SBR vulcanizates

It is generally believed that only intermolecular, elastically-effective crosslinks influence elastomer properties. The role of the intramolecular modifications of the polymer chains is marginalized. The aim of our study was the characterization of the structural parameters of cured elastomers, and determination of their influence on the behavior of the polymer network. For this purpose, styrene-butadiene rubbers (SBR), cured with various curatives, such as DCP, TMTD, TBzTD, Vulcuren®, DPG/S8, CBS/S8, MBTS/S8 and ZDT/S8, were investigated. In every series of samples a broad range of crosslink density was obtained, in addition to diverse crosslink structures, as determined by equilibrium swelling and thiol-amine analysis. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to study the glass transition process, and positron annihilation lifetime spectroscopy (PALS) to investigate the size of the free volumes. For all samples, the values of the glass transition temperature (Tg) increased with a rise in crosslink density. At the same time, the free volume size proportionally decreased. The changes in Tg and free volume size show significant differences between the series crosslinked with various curatives. These variations are explained on the basis of the curatives’ structure effect. Furthermore, basic structure-property relationships are provided. They enable the prediction of the effect of curatives on the structural parameters of the network, and some of the resulting properties. It is proved that the applied techniques—DSC, DMA, and PALS—can serve to provide information about the modifications to the polymer chains. Moreover, on the basis of the obtained results and considering the diversified curatives available nowadays, the usability of “part per hundred rubber” (phr) unit is questioned.

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“…This analysis was originally developed for natural rubber. Nowadays it is also often used for other types of elastomers [ 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

Influence of Network Structure on Glass Transition Temperature of Elastomers

et al. 2016

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“…Second, this species reacts preferentially with allylic hydrogen atoms of rubber to form initial crosslinks. As the cure proceeds, these crosslinks are broken down to form mono and disulfidic crosslinks 7. The organophilic silicate behaves as an accelerant agent for SBR vulcanization.…”

Section: Resultsmentioning

confidence: 99%

Exfoliated/intercalated silicate/hot styrene butadiene rubber nanocomposites: Structure–properties relationship

Diez

Barral

Bellas

et al. 2012

J of Applied Polymer Sci

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Rubber nanocomposites based on hot styrene-butadiene rubber (SBR) and organophilic layered silicate were prepared via mechanical mixing followed by compression molding. Varying amount of organically modified nanosilicate, 2.5, 5, 10, and 15 parts per hundred of rubber (phr), was added to the SBR matrix to examine the influence of nanosilicate on morphology and structure-property relationships. The morphology of nanocomposites was studied by X-ray diffraction and transmission electron microscopy which reveal that the nanocomposite contained a good dispersion of intercalated/exfoliated layers through the matrix. The interaction between SBR matrix and nanofiller was studied by infrared spectroscopy. No clear evidence for the formation of new components in the rubber was found but infrared spectroscopy denoted evidence for exfoliation. The reinforcing effect of the nanosilicate was determined by mechanical testing and dynamomechanical analysis. The results indicate that the tensile properties and the storage modulus increased with increasing nanofiller loading. This suggests a strong rubber-nanosilicate interaction which is attributed to the exfoliated/intercalated structure. Thermogravimetric analysis revealed that incorporation of organoclay enhances the thermal stability of the nanocomposites. The best thermal stability was observed for nanocomposites containing 5 phr nanosilicate. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: E705-E713, 2012

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“…The C1 and PC1 copolymers displayed similar dynamic behavior and their curves resembled those of loosely cross-linked rubbers and elastomers thanks to the presence of crystalline domains functioning as physical crosslinkers. 60,61 Compared to PC3 copolymer they exhibited higher value of E 0 and their terminal ow region shied towards slightly higher temperatures. Comparable results were reported by Ryynänen et al for multiblock poly(3-caprolactone-co-D,L-lactide-b-3-caprolactone) (P(CL/DLLA-b-CL)) copolymers 62 Similarly to the evaluation of tensile properties, based on the negligible difference of PC1 and PC3 copolymers' molar masses, the difference in dynamic mechanical behavior was directly linked to the inuence of crystalline phase content arising from their copolymer microstructure.…”

Section: Structure Mechanical Properties Relationshipmentioning

confidence: 96%