Molecular orientation and stress relaxation during strain-induced crystallization of vulcanized natural rubber

Abstract

Birefringence and tensile stress of vulcanized natural rubber samples were measured simultaneously during fast deformation and subsequent holding at a prefixed extension ratio. The deviation from the stress-optical law due to finite chain extensibility could be clearly detected, which became pronounced with an increase in true stress. The increase in birefringence during the holding process was related to the different degrees of molecular-chain orientation to be incorporated into strain-induced crystals according to the network-chain density and the strain ratio of holding. During the holding process, normalized stress decreased linearly with the logarithm of elapsed time in a manner that is almost independent of network-chain density. These experimental results could be successfully explained by assuming a certain fraction of network chains that behave in a manner similar to that of a fluid.

Strain-Induced Crystallization of Natural Rubber: A Review of X-Ray Diffraction Investigations

“…84 This result is in good agreement with the one of Tosaka et al 15 in the same range of crosslink density. Chenal and coworkers showed that SIC diminution is associated with an important reduction of the crystallites volume: from 290 nm 3 for ν = 1.61 × 10 4 mol/cm 3 to 130 nm 3 for ν = 1.95 × 10 4 mol/cm 3 .…”

“…The first publications on this subject emerged in the early 2000s. 61,[68][69][70][71] A few research groups in the world are active in this field mainly in Japan and USA (with experiments performed on SPring8 synchrotron in Hyogo, Japan and on National Synchrotron Light Source at Brookhaven National Laboratory in New York, USA) 15 Figure 9 presents an example of a stress-strain curve with the corresponding WAXD pattern obtained on a vulcanized NR at room temperature. 73 Toki and coworkers consider that stretched rubber can be decomposed into three phases: (i) an unoriented amorphous phase, (ii) an oriented amorphous phase, and (iii) a crystalline phase.…”

“…Many experimental techniques were used over the years to investigate the crystallization of NR under strain: volume change, [7][8][9][10] stress relaxation, 9 transmission electron microscopy, 11,12 differential scanning calorimetry, 13 birefringence, 14,15 nuclear magnetic resonance, 5,16 or Raman spectroscopy. 17 Nevertheless, the present review will be limited to wide-angle x-ray diffraction (WAXD) studies of SIC, from the pioneering works to the most recent studies.…”

Phase field modelling of strain induced crystal growth in an elastic matrix

“…79 In order to understand the role played by anisotropy of surface tension in the growth process, we have chosen a simple form of f w that ensures a surface tension larger in the y direction than in the x direction following Eq. (12). The mode number and the modulation amplitude of anisotropy are fixed, respectively, to FIG.…”

“…3,5,6 Since the discovery of SIC in NR by Katz in 1925, 7,8 many experimental 1,2,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and theoretical [27][28][29][30][31][32] studies have been made in order to understand it. Experimentally, several techniques have been used with NR, synthetic rubber, and NR carbon-filled, such as birefringence, 12,13 infrared absorption, 14,15 differential scanning calorimetry (DSC), 16 and X-ray diffraction. 2,9,10,[17][18][19][20] Nowadays, the possibilities offered by modern X-ray facilities allow an investigation of the growth at the very nanometric scale of the crystallites.…”