Devulcanization of Natural Rubber in Composites with Distinct Crosslink Densities by Twin-Screw Extruder

In this study, the effects of the devulcanization process realized by an intermeshing co-rotating twin-screw extruder (ICTSE) on three vulcanized Natural Rubber (NR) composites with different crosslink densities (CD) have been investigated. The extrusion parameters were fixed, as well as the initial material granulometry and auxiliary thermoplastic added to the process. After composites vulcanization, they were characterized accordingly their soluble fraction (SF), crosslink density (CD), mechanical properties and thermogravimetry (TGA). The extrusion was performed on the vulcanized elastomers pursuing selectively crosslink rupture and the same characterization previously cited was conducted on the devulcanized material, except the mechanical properties analysis. The extrusion demonstrate effective devulcanization, evidenced in the increasing of soluble fractions, reduction in crosslink density and thermal stability gain. These results are directly affected by preliminary differences on materials structure and presence of ethylene vinyl-acetate (EVA) on extrusion.本研究针对三款具有不同交联密度（crosslink density, CD）的硫化天然橡胶（Natural Rubber, NR）复合材料，探究了采用啮合型同向旋转双螺杆挤出机（intermeshing co-rotating twin-screw extruder, ICTSE）实施的脱硫化工艺对其产生的影响。实验中固定了挤出工艺参数、初始物料粒度以及过程中添加的辅助热塑性材料。在复合材料完成硫化后，分别对其可溶组分（soluble fraction, SF）、交联密度、力学性能与热重分析（thermogravimetry, TGA）开展了表征工作。本实验对硫化弹性体进行挤出处理以实现选择性交联键断裂，随后对脱硫化后的材料开展前述相同的表征工作，仅未包含力学性能分析。结果表明，该挤出工艺可实现有效的脱硫化效果，具体体现为可溶组分占比提升、交联密度降低以及热稳定性增强。上述实验结果直接受到物料初始结构差异以及挤出过程中乙烯-醋酸乙烯酯共聚物（ethylene vinyl-acetate, EVA）添加情况的影响。