Increasing the Dissolution Rate of Polystyrene Waste in Solvent-Based Recycling.

Area of Science:

• Polymer Science
• Chemical Engineering
• Materials Recycling

Background:

• Solvent-based recycling offers polymer chain cleaning without degradation.
• Current lab-scale dissolution processes for polymers can be time-consuming, taking hours.
• Optimizing dissolution kinetics is crucial for efficient plastic waste recycling.

Purpose of the Study:

• To identify key factors influencing polystyrene dissolution rates in solvents.
• To explore reactor design and operational parameters for faster dissolution.
• To validate optimized dissolution conditions with real plastic waste samples.

Main Methods:

• Broad solvent screening to compare dissolution times.
• Multiple regression modeling to correlate solvent properties with dissolution time.
• Kinetic studies in lab-scale and baffled reactors, varying temperature, particle size, and agitation.
• Analysis of dissolution kinetics using a first-order kinetic model.

Main Results:

• Solvent viscosity was the primary factor affecting dissolution time, followed by solubility parameters (hydrogen, polar, dispersion bonding).
• Cyclohexene, 2-pentanone, ethylbenzene, and methyl ethyl ketone demonstrated fast dissolution properties.
• Increased turbulence in a baffled reactor reduced dissolution time from 40 to 7 minutes.
• Dissolution in a baffled reactor was confirmed to be at least 5-fold faster than in a lab-scale reactor.

Conclusions:

• Solvent properties, particularly viscosity, and reactor design, specifically turbulence, are critical for rapid polystyrene dissolution.
• Optimized conditions, including baffled reactor use, can drastically reduce recycling process times.
• Full dissolution of real plastic waste was achieved in 5 minutes under optimized conditions, demonstrating practical applicability.