Observation of crosslink density dispersion in sulfur donor-vulcanized polybutadiene using NMR imaging

SUMMARY:This paper discusses the effect of heterogeneities in crosslink density on static properties, such as the mechanical stress-strain relation (free energy) and scattering effects as occur in small-angle neutron experiments. The second part of the paper is devoted to the segmental dynamics and the long-time relaxation of polymer networks. It is shown that the heterogeneities slow down the relaxation at long times.

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“…This predicts the interpolation formula (4. 14) which recovers all limits known so far. For d = 0 (no heterogeneities), Eq.…”

Section: (Cg(qw))supporting

confidence: 84%

Statics and dynamics of heterogeneous polymer networks

Vilgis

Heinrich

1994

Macro Theory & Simulations

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“…NMR spectroscopy has been used in the past to study of the crosslinked elastomers. It was shown by Smith et al28 that the method provides a variety of structural detail, that is, structural voids, compression‐, and reaction‐induced gradients of chain segment mobility of elastomers of different crosslinking densities. And during the work of C. Fülber et al,29 the vulcanization as a function of time was presented.…”

Section: Resultsmentioning

confidence: 99%

An effect of OMMT on the anti‐reversion in NR/CR blend system

Zhang

Huang

Liu

2008

J of Applied Polymer Sci

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The influence of dispersed organomodified montmorillonite (OMMT) on curing behaviors of natural rubber (NR)/chloroprene rubber (CR) blend was investigated. The preparing procedure includes premixed rubber individually with its additives and then the two components were blended according to gum weight ratio for NR to CR is 75/25. Sulfur was chosen as the vulcanizing agent, and the research on vulcanization was carried through the rotor-Rheometer at 143 C. Transmission electron microscopy showed the dispersion of OMMT in the rubber blends and detected little OMMT migrated into the NR phase. The scorch time (t 10 ), optimum vulcanizing time (t 90 ), and reversion phenomenon were both measured by the curing curve; meanwhile, the crosslinking densities and mechanical properties were determined through equilibrium swelling-method, magnetic resonance crosslink density spectrometer, and tensile tests. By comparing the test results, an interesting phenomenon was discovered and furthermore was verified that the addition of OMMT can obviously modify the reversion resistance of the binary blend.

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“…However, sometimes the mobility of the macromolecules becomes so high due to swelling that MRI imaging of the polymer is possible without using solid-state NMR techniques. 30,31 It should be noted that MRI allows one to obtain separate images of the solvent and the polymer, as well as the images of individual solvents if their mixtures are used in the experiments (see Section III.1 in Ref. 1).…”

Section: Swelling Of Polymers and Coal During Sorption Of Solvents 1 ...mentioning

confidence: 99%