Scholarlink

Context <p>This study investigates the thermal degradation behavior of cis-1,4-polyisoprene and its nanocomposites using a combined approach of reactive molecular dynamics simulations and experimental techniques. Pyrolysis was experimentally conducted up to 500 °C using a custom-built lab-scale-tubular reactor (20 mm diameter, 300 mm length). Samples were prepared by melt mixing, followed by compression molding into 1 mm thick sheets. Simulations were performed up to 2500 K using the ReaxFF reactive force field, selected for its ability to dynamically model bond breaking and formation in reactive systems. We constructed a simulation system containing ten polymer chains and up to two nano-silica units (576 atoms each) within a 150 Å periodic box, using the NVT ensemble with a Nosé–Hoover thermostat and a time step of 0.25 fs over a total duration of 42 ps. Experimental analyses via TGA, FTIR, and GC–MS confirmed the formation of key pyrolysis products such as isoprene (C₅H₈), ethylene (C₂H₄), and methane (CH₄). The addition of 60 wt% nano-silica extended the degradation time by approximately 100% and increased the activation energy from 121.9 to 133.8 kJ/mol—a 9.77% rise—suggesting a stabilizing role in the thermal degradation process. Mechanistic insights revealed that degradation proceeds via radical-driven scission near double bonds, with nano-silica modulating both the rate and pathway of decomposition. Overall, the results demonstrate a concentration-dependent dual role of nano-silica in thermal degradation and provide a predictive framework for designing heat-resistant rubber nanocomposites and advancing sustainable pyrolysis-based recycling technologies.</p> Methods <p>Cis-1,4-polyisoprene, a naturally derived elastomer with high flexibility and unsaturation, was used as the base polymer (Mw ≈ 38,000 g/mol, Sigma-Aldrich). Nanocomposites containing 30 wt% and 60 wt% nano-silica were prepared via magnetic stirring and compression molding. Pyrolysis experiments were conducted in a lab-scale tubular reactor under nitrogen flow, and thermal behavior was analyzed using thermogravimetric analysis (STA 504, Bahr, Germany). Volatile products and functional groups were identified via FTIR and GC–MS. Reactive molecular dynamics simulations were performed using LAMMPS with a ReaxFF force field parameterized for C/H/O/Si systems. Simulations employed the NVT ensemble with a Nosé–Hoover thermostat to model bond dissociation and reaction pathways at elevated temperatures (1500–2500 K), enabling direct comparison with experimental results.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Reactive molecular dynamics simulation and experimental validation of pyrolysis in Cis-1,4-polyisoprene nanocomposite

  • 期刊论文

  • 发表日期：

    2025年11月18日

查看全文
  • Meysam Raeisian,
  • Davood Ajloo,
  • Hadi Baseri

摘要

Context

This study investigates the thermal degradation behavior of cis-1,4-polyisoprene and its nanocomposites using a combined approach of reactive molecular dynamics simulations and experimental techniques. Pyrolysis was experimentally conducted up to 500 °C using a custom-built lab-scale-tubular reactor (20 mm diameter, 300 mm length). Samples were prepared by melt mixing, followed by compression molding into 1 mm thick sheets. Simulations were performed up to 2500 K using the ReaxFF reactive force field, selected for its ability to dynamically model bond breaking and formation in reactive systems. We constructed a simulation system containing ten polymer chains and up to two nano-silica units (576 atoms each) within a 150 Å periodic box, using the NVT ensemble with a Nosé–Hoover thermostat and a time step of 0.25 fs over a total duration of 42 ps. Experimental analyses via TGA, FTIR, and GC–MS confirmed the formation of key pyrolysis products such as isoprene (C₅H₈), ethylene (C₂H₄), and methane (CH₄). The addition of 60 wt% nano-silica extended the degradation time by approximately 100% and increased the activation energy from 121.9 to 133.8 kJ/mol—a 9.77% rise—suggesting a stabilizing role in the thermal degradation process. Mechanistic insights revealed that degradation proceeds via radical-driven scission near double bonds, with nano-silica modulating both the rate and pathway of decomposition. Overall, the results demonstrate a concentration-dependent dual role of nano-silica in thermal degradation and provide a predictive framework for designing heat-resistant rubber nanocomposites and advancing sustainable pyrolysis-based recycling technologies.

Methods

Cis-1,4-polyisoprene, a naturally derived elastomer with high flexibility and unsaturation, was used as the base polymer (Mw ≈ 38,000 g/mol, Sigma-Aldrich). Nanocomposites containing 30 wt% and 60 wt% nano-silica were prepared via magnetic stirring and compression molding. Pyrolysis experiments were conducted in a lab-scale tubular reactor under nitrogen flow, and thermal behavior was analyzed using thermogravimetric analysis (STA 504, Bahr, Germany). Volatile products and functional groups were identified via FTIR and GC–MS. Reactive molecular dynamics simulations were performed using LAMMPS with a ReaxFF force field parameterized for C/H/O/Si systems. Simulations employed the NVT ensemble with a Nosé–Hoover thermostat to model bond dissociation and reaction pathways at elevated temperatures (1500–2500 K), enabling direct comparison with experimental results.