Material Characterization of Polypropylene and Polystyrene Regarding Molecular Degradation Behavior

Area of Science:

• Polymer Science
• Materials Engineering
• Chemical Engineering

Background:

• Thermoplastic processing induces stress, causing polymer chain scission and reduced molar mass.
• This degradation lowers melt viscosity, negatively impacting the mechanical properties of final plastic products.
• Material degradation presents significant challenges in plastic recycling and process technology.

Purpose of the Study:

• To develop a predictive model for material degradation under defined processing stresses.
• To enable material-gentle process design for thermoplastics.
• To improve the understanding and control of polymer breakdown during manufacturing and recycling.

Main Methods:

• Designed a specialized test stand to induce and measure material degradation under controlled temperature, shear rate, and residence time.
• Measured melt viscosity as a key indicator of polymer degradation, correlating it with molar mass changes.
• Utilized a test plan and mathematical modeling to describe the relationship between stress variables and viscosity reduction.

Main Results:

• Successfully correlated viscosity decrease with polymer degradation under specific processing conditions.
• Developed a mathematical model to predict material damage based on temperature, shear rate, and residence time.
• Demonstrated the feasibility of simulating material degradation, including viscosity reduction, within plastics processing environments.

Conclusions:

• The developed predictive model allows for better control over material degradation during thermoplastic processing.
• Integration into simulation environments facilitates optimized process design, particularly for recycling applications.
• This approach enhances the ability to maintain or predict the quality of recycled plastics.