With the guidance of Prof. Li and Dr. Chen, the work: Strain-induced crystal growth and molecular orientation of poly(isobutylene-isoprene) rubber at low temperatures is studied by doctor Pinzhang Chen et al. The related work has been published in Soft Matter.
Strain-induced crystallization (SIC) of poly(isobutylene-isoprene) rubber (IIR) at descending temperatures as low as -60 °C was systematically investigated by in-situ synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) measurement. The detailed structural evolution of IIR during SIC is summarized in the strain-temperature space, where three distinct temperature zones are defined. The absence of SIC in zone I (T > 0 °C) results in the poorest drawability of IIR among all measured temperatures. And with respect to the lowest temperature zone III (-60 °C < T < -50 °C), SIC still occurs with low ultimate crystallinity (ca. 0.9 %). More complicated structural evolution induced by strain occurs in the intermediate-temperature zone II (-50 °C ≤ T ≤ 0 °C). The orientation ratio of the amorphous part Oa increases monotonically with the increment of strain, but reaches a platform with Hencky strain ε > ca. 1.8. Meanwhile, the strain-induced crystal growth of IIR is evidenced by the dramatic increment of the lateral crystallite size of (110) and (113) planes. Moreover, the retraction experiment further reveals the network evolutions of IIR: suffering from low ultimate crystallinity (< ca. 9 %), the network chain of IIR remains in serial upon fracture. Current study clarifies the contribution of SIC and molecular orientation to the self-enhanced mechanical properties of IIR at low temperatures.
This work is supported by the National Natural Science Foundation of China (51790503 and 51633009) and the experimental fund of Shanghai Synchrotron Radiation Facility (SSRF).
Related links:https://pubs.rsc.org/en/content/articlelanding/2019/sm/c9sm00632j#!divAbstract
