Evolution of crosslinking structure in vulcanized natural rubber during thermal aging in the presence of a constant compressive stress
Evolution of crosslinking structure in vulcanized natural rubber during thermal aging in the presence of a constant compressive stress
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DOI：
10.1016/j.polymdegradstab.2023.110513
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发表时间：
2023-08
影响因子：
5.9
通讯作者：
Yiran Kong;X. Chen;Zhouxian Li;Guang-xian Li;Yajiang Huang
中科院分区：
文献类型：
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作者：
Yiran Kong;X. Chen;Zhouxian Li;Guang-xian Li;Yajiang Huang
利用自制的恒应力装置研究了硫化天然橡胶（NR）在压缩应力和温度共同作用下交联结构的演变过程。采用红外光谱、化学探针法、差示扫描量热法和力学分析等方法对老化后的天然橡胶样品进行了表征。结果表明，压缩应力促进了NR链间硫键（主要是低能硫键）的断裂，导致交联密度下降，网眼尺寸增大。根据Arrhenius方程，1.78 MPa的压缩应力使多硫键断裂的表观活化能从56.3 kJ/mol降低到48.2 kJ/mol，导致降低14.4%。多硫键断裂后形成的含硫侧基不仅参与了应力释放后的后交联反应，而且增加了NR在大变形下的滞后损失。
The evolution process of the crosslinking structure in sulfur-cured natural rubber (NR) under the combined effect of compressive stress and temperature was investigated using a homemade constant-stress device. The aged NR samples were characterized by infrared spectroscopy, chemical probe method, differential scanning calorimetry, and mechanical analysis. The results revealed that compressive stress promoted the breakage of sulfur bonds (mainly low-energy ones) between NR chains, leading to a decline in crosslink density and an increase in mesh size. According to the Arrhenius equation, a compressive stress of 1.78 MPa reduced the apparent activation energy for the breakage of polysulfide bonds from 56.3 kJ/mol to 48.2 kJ/mol, resulting in a 14.4% decrease. The sulfur-containing side groups formed after the breakage of polysulfide bonds not only participated in post-crosslinking reactions after stress release but also increased the hysteresis loss of NR under large deformation.