Accurately predicted key thermophysical and structural properties such as glass transition temperature (Tg), density, free volume, and diffusion coefficient for rubber mixture systems
Explored the miscibility of transpolyoctenamer rubber (TOR) with different crosslinkers and base polymers
Developed an understanding of the impact of macrocyclic polymer chains on the structural and thermophysical properties
Accelerated rational design of highperformance rubber formulations and provided insights into the key factors for processability of recycled rubbers
Trans-polyoctenamer rubber (TOR), commercially known as VESTENAMER®, has been widely used as a tire additive to improve the processability and recyclability of tire rubbers. In order to efficiently co-vulcanize different rubbers to obtain improved properties, it is vital to understand the interaction of TOR with different components of rubber formulations, including crosslinkers and base polymers. However, experimental characterization of these formulations is time-consuming and resource-intensive.
Molecular modeling provides an economical alternative to long experiments and lengthy development cycles for new tire formulations. Scientists from Evonik and Schrödinger worked together to digitally evaluate the miscibility of TOR with various crosslinkers and polymers, and to look into the impact of macrocyclic polymer chains on TOR properties. With GPU-accelerated molecular dynamics (MD) engine, scientists were able to run the simulations at high-speed, e.g. 50ns of diffusion calculations, in only a few hours. All models and simulations were performed using the Schrödinger Materials Science Suite and Desmond for MD according to the following procedure:
The computational approach revealed new insights into the compatibility of various polymers/crosslinkers and provided an accurate evaluation of the structural and thermophysical properties of TOR systems as summarized to the right. The work serves as an example of how digital molecular simulations can provide unique insights that are not readily available or economical to study in an experimental setting.
The simulation methods and workflows presented in this work can be easily extended to study other polymer/crosslinker systems.
The miscibility order for the crosslinkers in SBR, NR, and TOR is TBzTD > SA > CBS > S8, suggesting S8 likely has a limited miscibility in all three polymers, which is also demonstrated by computing the energy of mixing
Crosslinkers diffuse more in TOR when compared to SBR and NR allowing for better crosslinking
SBR, NR, and TOR are likely not miscible with each other. A mixture of these three polymers would most likely result in a three-phase system, which is in line with experimental studies
Interaction energy and density analysis indicated ideal mixing at low crosslinker concentration for all the mixtures
TOR macrocycles can potentially affect the viscosity as well as other mechanical properties, and may contribute to lower glass transition temperature of TOR
Using molecular simulation to assess the impact of additives and macrocyclic structures on trans-polyoctenamer rubber (TOR) Mohammad Atif Faiz Afzal, Benjamin J Coscia, Andrea R Browning, Thomas S. Asche, Alexander Paasche, Mathew D. Halls International Elastomers Conference, Oct 4-7, 2021, Pittsburgh
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