TPV Foaming by CO₂ Extrusion: Processing and Modelling

Area of Science:

• Materials Science
• Polymer Processing
• Computational Modeling

Background:

• Extrusion foaming is a key process for producing lightweight polymer materials.
• Controlling foam morphology is crucial for achieving desired material properties.
• Carbon dioxide (CO2) is an environmentally friendly blowing agent for polymer foaming.

Purpose of the Study:

• To investigate the influence of extrusion foaming process parameters on the morphology of commercial thermoplastic vulcanizates (TPVs) using CO2.
• To develop a numerical model for simulating cell growth during extrusion foaming.
• To establish a predictive model for foam density and cell structure.

Main Methods:

• Extrusion foaming of TPVs with CO2 as the blowing agent.
• Systematic variation of process parameters: saturation pressure, die geometry, temperature, and nucleation.
• Development and application of numerical models for cell growth and polymer flow dynamics.
• Analysis of foam morphology, including cell size and distribution.

Main Results:

• Homogeneous TPV foams with densities below 500 kg/m³ were achieved through precise control of saturation pressure, die geometry, temperature, and nucleation.
• An optimal CO2 content is necessary to mitigate coalescence, which is exacerbated by longer residence times and early nucleation.
• The proposed model accurately predicts the plasticizing effect of CO2 on polymer flow and simulates the foaming process inside and outside the die.
• The model successfully predicts final cell foam radius and density for optimized nucleation parameters.

Conclusions:

• Precise control over extrusion foaming parameters is essential for producing high-quality, low-density TPV foams.
• Understanding and controlling CO2 content is critical to prevent cell coalescence and ensure foam homogeneity.
• The developed numerical models provide valuable tools for predicting and optimizing the TPV extrusion foaming process.