A plasticizer is an additive, often a high-boiling organic liquid, that is mixed into polymers or other materials to increase flexibility, workability, and softness, reducing brittleness and enhancing processability. Plasticizers are essential for imparting the properties that materials require to perform their function effectively across industries, from construction to medical devices.  

As technology evolves, so does the demand for new plasticizer materials. Nowadays, research on plasticizers focuses on identifying new materials with improved mechanical and thermal properties, with an emphasis on sustainability through biodegradable and renewable sources.

Chemical simulations have emerged as a time- and cost-effective alternative to traditional trial-and-error approaches in developing a wide range of new chemicals and materials, including plasticizers. This use case demonstrates how molecular dynamics simulations in QuantistryLab can provide valuable insights into the viscosity of a commercial plasticizer, a property that is of major importance when it comes to determining a plasticizer’s efficiency.

System of interest: ATBC

Plasticizers are chemicals added to a material to increase softness and flexibility, which increases the plasticity while decreasing the viscosity of the final material. These altered properties are essential to achieving the desired properties of the end product, and to facilitating the handling of the material during manufacturing.  

Acetyl tributyl citrate (ATBC) is a plasticizer commonly used in polyvinyl chloride (PVC), a thermoplastic material with extensive applications, including roofing and flooring, plumbing, insulation, vinyl records, 3D printing, and medical devices. Without plasticizers, PVC would be hard and brittle and not suitable for all these uses.

Viscosity is a key property of plasticizers like ATBC, since one of their primary effects is to lower the viscosity and density of materials, making them softer. Generally, plasticizers with lower viscosity offer higher plasticizing efficiency.  

Optimizing viscosity is essential in the R&D process for developing new plasticizers. With simulation technology, the viscosity of any plasticizer candidate can be calculated without the need for costly and time-consuming experimental measurements, thus accelerating the R&D pipeline.  

Use case: Viscosity simulations of ATBC

With just a few clicks, QuantistryLab allows the user to run molecular dynamics simulations of chemical systems such as plasticizers, lubricants, polymers, and electrolytes, enabling the modeling and prediction of many of their macroscopic properties, including viscosity.

To predict the viscosity of a chemical system, QuantistryLab deploys molecular dynamics simulations to measure fluctuations in the stress tensor over time. Using the Green-Kubo approach, a statistical mechanics method that employs autocorrelation functions of the stress tensor, an estimation of the viscosity at equilibrium is obtained.  

The first step in running these simulations is to generate a model of the plasticizer of interest, which can be easily achieved by creating a liquid preparation and selecting the desired chemicals from the compound library.  

For this use case, the preparation consisted of 100% ATBC. This pre-processed model serves as the starting point for the subsequent steps.

Once the model is created, its viscosity can be calculated by starting a workflow with QuantistryLab’s viscosity feature. The user simply needs to set the desired temperature and pressure for the simulation, in this case 293 °K (~20 °C) and 100 kPa. The results of the simulation yield a 3D atomistic model that represents the dynamical behavior of the atoms that make up the plasticizer as a function of time.

The viscosity of ATBC, as calculated by QuantistryLab, is in the range of 22-32 mPa·s. To validate the accuracy of this prediction, the model's viscosity value was compared to experimental results disclosed by a commercial provider of ATBC. The experimental viscosity reported at similar conditions of temperature and pressure was in the range of 32-38 mPa·s.  

The predicted value falls within the range of the experimental measurements reported in the literature, confirming the predictive power of QuantistryLab’s computational setup.

Plasticizer technology has significantly advanced since they were first introduced in commercial applications back in the 1870s. Today, they are often used in combination with other plasticizers to achieve great levels of precision and control over the properties of the end material. These combinations can be easily modeled and investigated with QuantistryLab, as the platform enables the user to easily create mixtures of multiple chemicals and calculate the resulting viscosity using the workflow described in this use case.

This same approach can be extended to any number of applications across multiple areas of interest, including energy storage, metals and alloys, lubricants, semiconductors and specialty chemicals. For all these applications and more, QuantistryLab offers a full range of computational solutions to study the properties of a wide range of chemical and material systems.

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