Rupture, orientation and strain-induced crystallization of polymer chain and network in vulcanized polyisoprene during uniaxial deformation by in-situ Electron Spin Resonance (ESR) and synchrotron X-ray analysis

Toki, Shigeyuki; Takagi, Ryuichi; Ito, Masayoshi; Hsiao, Benjamin S.

doi:10.1016/j.polymer.2011.03.037

Cited by 18 publications

(10 citation statements)

References 20 publications

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“…When the strain‐induced crystallization of NR is suppressed at elevated temperatures, the tensile strength drops dramatically 16, 17. Recently, it has been possible to measure the extent of crystallization of NR during tensile deformation using real time synchrotron X‐ray diffraction and NMR 18–21. Using synchrotron diffraction, Toki et al showed that the majority of the chains (∼75% by mass) remain amorphous and unoriented even at large deformations because of the inhomogeneities in the crosslinked network 20.…”

Section: Introductionmentioning

confidence: 99%

Strain‐induced crystallization and mechanical properties of functionalized graphene sheet‐filled natural rubber

Ozbas

Toki

Hsiao

et al. 2012

J Polym Sci B Polym Phys

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100

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The effects of functionalized graphene sheets (FGSs) on the mechanical properties and strain-induced crystallization of natural rubber (NR) are investigated. FGSs are predominantly single sheets of graphene with a lateral size of several hundreds of nanometers and a thickness of 1.5 nm. The effect of FGS and that of carbon black (CB) on the strain-induced crystallization of NR is compared by coupled tensile tests and X-ray diffraction experiments. Synchrotron X-ray scattering enables simultaneous measurements of stress and crystallization of NR in real time during sample stretching. The onset of crystallization occurs at significantly lower strains for FGS-filled NR samples compared with CB-filled NR, even at low loadings. Neat-NR exhibits straininduced crystallization around a strain of 2.25, while incorporation of 1 and 4 wt % FGS shifts the crystallization to strains of 1.25 and 0.75, respectively. In contrast, loadings of 16 wt % CB do not significantly shift the critical strain for crystallization. Two-dimensional (2D) wide angle X-ray scattering patterns show minor polymer chain alignment during stretching, in accord with previous results for NR. Small angle X-ray scattering shows that FGS is aligned in the stretching direction, whereas CB does not show alignment or anisotropy. The mechanical properties of filled NR samples are investigated using cyclic tensile and dynamic mechanical measurements above and below the glass transition of NR. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: [718][719][720][721][722][723] 2012

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Section: Introductionmentioning

confidence: 99%

Strain‐induced crystallization and mechanical properties of functionalized graphene sheet‐filled natural rubber

Ozbas

Toki

Hsiao

et al. 2012

J Polym Sci B Polym Phys

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100

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“…In first term, and taking into account the previous statements, the higher concentration of free radicals during the vulcanization with EV system should be mainly ascribed to the highest amount of accelerant (CBS) in the recipe. According to previous studies, the molecule of CBS produces radicals at 150°C [14,21]. The cross-link density is around 30% higher for samples vulcanized with the EV system.…”

Section: Comparison Of Radical Amounts Produced By Different Vulcanizmentioning

confidence: 74%

“…Two accumulations were enough to get an ESR absorption curve with high signal to noise ratio. A double integration of the first derivative curve of ESR signal at room temperature from benzene solution of 4-hidroxy-2,2,6,6,-tetramethyl piperidinooxyl radical (TEMPOL) with a known radical concentration was used as a standard to calculate the radical concentration of rubber samples [14,[18][19][20]. The radical concentration is defined per gram of rubber.…”

Section: Electron Spin Resonance (Esr)mentioning

confidence: 99%

“…Recently, ESR has been applied to study the polybutadiene vulcanization mechanism [13]. In addition to the study of vulcanization process, the second part of this work will be focused on the study of radicals generated during uniaxial deformation of NR [14], fact that could be related with variations in the network structure and consequently in the final properties of NR after cycles of deformation.…”

Section: Introductionmentioning

confidence: 99%

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ESR investigation of NR and IR rubber vulcanized with different cross-link agents

Posadas¹,

Malmierca²,

Jiménez³

et al. 2016

Express Polym. Lett.

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Abstract. This study evaluates the formation of radical species in natural rubber (NR) and poly-isoprene rubber (IR) during the vulcanization process and the uniaxial deformation of the formed networks by means of Electron Spin Resonance (ESR). Vulcanization of NR and IR always shows a radical pathway, where the different vulcanization systems dictate the concentration of radical species in the course of this complex process. The greatest concentration of radicals were detected during the vulcanization with sulfur/accelerator based on efficient systems (EV), followed by conventional (CV) and sulfur donor systems, whereas azide and organic peroxide agents showed smaller concentration of radicals. Independently of the vulcanization system, certain amount of radicals was detected on the vulcanized samples after the end of the vulcanization process. Comparison between different matrices demonstrates that NR always shows higher concentration of radicals than IR in the vulcanization process as well as during uniaxial deformation, fact that could be associated to the presence of nonrubber components in NR.

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“…When releasing the stretching force the crystals vanish and the rubber restores its original shape. Over the last 80 years, nucleation and growth of the strain‐induced crystals was explored in countless theoretical as well as experimental works using transmission electron microscopy (TEM), small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) while being stretched . All the more surprising is that such a long known and extensively studied material is able to fascinate nowadays with completely new and unexpected properties.…”

Section: Introductionmentioning

confidence: 99%

Shape memory natural rubber

Katzenberg

Tiller

2016

J Polym Sci B Polym Phys

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Charles Goodyear discovered the vulcanization of natural rubber (NR) 170 years ago and transferred the gooey natural compound into the first representative of an entirely new class of materials; the elastomers. Thenceforth, NR was intensively explored and was used for countless products to date. All the more surprising, it was found recently that NR exhibits superior and unexpected properties whenever it is cross-linked to a degree smaller than 0.4% which is fairly below the commonly used 1%-2%. This article gives a brief overview on the exceptional properties of lightly cross-linked NR, named shape memory natural rubber (SMNR), including the cold programmable shape memory effect, storing of extremely large strain, energy and cold, and its capability to sense and memorize environmental parameters.

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Rupture, orientation and strain-induced crystallization of polymer chain and network in vulcanized polyisoprene during uniaxial deformation by in-situ Electron Spin Resonance (ESR) and synchrotron X-ray analysis

Cited by 18 publications

References 20 publications

Strain‐induced crystallization and mechanical properties of functionalized graphene sheet‐filled natural rubber

Strain‐induced crystallization and mechanical properties of functionalized graphene sheet‐filled natural rubber

ESR investigation of NR and IR rubber vulcanized with different cross-link agents

Shape memory natural rubber

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