Strain‐induced crystallization behavior of natural rubber and trans‐1,4‐polyisoprene crosslinked blends

Abstract

The strain-induced crystallization (SIC) behaviors of crosslinked blends based on natural rubber (NR) and trans-1,4-polyisoprene (TPI) with different content of TPI were probed explored by using synchrotron two-dimensional wide angle X-ray diffraction and dynamic mechanical analysis. The results showed that when TPI content is less than 70% no reflection peak of TPI but NR crystallite diffractions can be observed and the diffractions of TPI bform appear when TPI content is 70 wt % in the cocured blend. SIC of cocured blends started at smaller strain ratio than the pure NR. By calculating DS def , it is found that the drop in entropy upon strain decreased when TPI is incorporated into NR due to the reduction of molecular mobility of NR. The degree of SIC and crystallization rate index in crosslinked blends monotonously decreased with the increase of TPI content. The apparent crystallite size exhibited some surprising variations. L 200 and L 120 decreased with the increase of TPI content in the cocured blends. These observations were usually caused by two factors: (i) Less number of polymer chains could involve in crystal growth due to the lower mobility of polymer chains in the cocured blends which is proved by dynamic mechanical analysis results; (ii) The mean distance between nuclei decreases, which was caused by the fluctuation of crosslink density in NR phase derived from the heterogeneous distribution of curatives in two phases supported by the varying tendency of curing degree and crosslink density.

Effect of strain‐induced crystallization on the tear strength of natural rubber/styrene butadiene rubber blend

“…The sudden increase in the master curve of G around 273 K disappeared by an adjustment of the cross-link density of NR to 2.76 × 10 −4 mol/cm 3 , allowing superimposition into the single master curve. [6] Thus, the melting point of the crystals in NR_2D was expected to be 333 K. On the other hand, the low stress at break, 1 MPa, of NR_6D at all temperatures may be attributed to inhibition of strain-induced crystallization by increasing cross-link density. This may be attributed to the inhibition of strain-induced crystallization by increasing cross-link density.…”

“…[1][2][3][4][5][6] However, it is quite difficult to quantitatively investigate the relationship between the strain-induced crystallization and crack growth of an elastomer due to the difficulty of simultaneous observation of the strain-induced crystallization with breaking of the elastomer. [1][2][3][4][5][6] However, it is quite difficult to quantitatively investigate the relationship between the strain-induced crystallization and crack growth of an elastomer due to the difficulty of simultaneous observation of the strain-induced crystallization with breaking of the elastomer.…”

“…Strain‐induced crystallization of natural rubber (NR) in NR blends plays an important role in the mechanical properties of the blend because the crystals as a physical cross‐linking point and filler may prevent crack growth of the blend under large deformation . However, it is quite difficult to quantitatively investigate the relationship between the strain‐induced crystallization and crack growth of an elastomer due to the difficulty of simultaneous observation of the strain‐induced crystallization with breaking of the elastomer.…”

Effect of acetone extract from natural rubber on the structure and interface interaction in NR/CB composites

“…8(b)), which is in agreement with previous reports. 42,43,49 It can be observed that L 120 appears to slightly uctuate in composites without AE with increasing strain, which indicates that the increase in crystallinity is because of the increased number of crystallites. 41 However, L 120 is increased with the increase of AE at l ¼ 3 and it decreases signicantly on increasing the strain.…”

“…The crystallinity index CI and the average crystallite size L 120 (taking 120 plane as an example) were calculated according to the data in Fig. 7 using eqn (5) and (6); [42][43][44][45] then the results are found in Fig. 8.…”