Despite the widespread application of prevulcanized natural rubber latex film (VNRL), its microstructure of VNRL has not been fully elucidated, and the impact of the microstructure on strain-induced crystallization (SIC) and mechanical properties remains largely unexplored. Herein, the hierarchical microstructure of VNRL was unraveled, and the results were compared with those of a vulcanized natural rubber sheet (VNR) prepared by mechanical mixing and compression molding. With identical total cross-linking density, VNRL exhibits a more homogeneous network with higher entanglement content than VNR. Upon deformation, these entanglements can disentangle or slide along the chain backbones, reducing the constraining effect of cross-links on the molecular chains under moderate strains. Therefore, VNRL exhibits slightly delayed SIC and lower crystallization index (CI) in the strain range from 3.4 to 6 compared to VNR. However, at strains ≥4.5, the crystallization rate of VNRL surpasses that of VNR due to the formation of larger crystals, leading to a higher crystallization index of VNRL at strains ≥6. Meanwhile, the homogeneous structure enables the extension of the VNRL network to larger strains, ultimately resulting in superior fracture strain and strength compared to VNR. In addition, the nonrubber components of VNRL form a microscopic skeleton within the matrix, which can distribute stress and prevent crack growth, thereby enhancing the tear resistance and toughness of VNRL. This work provides new insights into the structure–property relationship of VNRL.

中文翻译：

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揭示预硫化天然橡胶乳胶薄膜的分层微观结构及其对机械性能的影响


尽管预硫化天然橡胶乳胶膜 （VNRL） 得到了广泛的应用，但其 VNRL 的微观结构尚未完全阐明，微观结构对应变诱导结晶 （SIC） 和机械性能的影响在很大程度上仍未得到探索。在此，解开了 VNRL 的分层微观结构，并将结果与通过机械混合和压缩成型制备的硫化天然橡胶板 （VNR） 的结果进行了比较。在相同的总交联密度下，VNRL 表现出比 VNR 更均匀的网络和更高的纠缠含量。在变形时，这些缠结可以沿着链骨架解开或滑动，从而减少了中度应变下交联对分子链的约束作用。因此，与 VNR 相比，VNRL 在 3.4 到 6 的应变范围内表现出略微延迟的 SIC 和较低的结晶指数 （CI）。然而，在菌株 ≥4.5 时，由于形成更大的晶体，VNRL 的结晶速率超过了 VNR，导致 VNRL 在菌株 ≥6 时的结晶指数更高。同时，均匀结构使 VNRL 网络能够扩展到更大的应变，最终导致与 VNR 相比具有更好的断裂应变和强度。此外，VNRL 的非橡胶成分在基体内形成微观骨架，可以分散应力并防止裂纹扩展，从而增强 VNRL 的抗撕裂性和韧性。这项工作为 VNRL 的结构-性质关系提供了新的见解。