Optimization of Composite Formulation Using Recycled Polyethylene for Rotational Molding

Area of Science:

• Materials Science
• Polymer Engineering
• Manufacturing Processes

Background:

• Rotational molding is a versatile manufacturing process for polymer composites.
• Optimizing material composition and processing parameters is key to achieving desired product properties.
• Recycled polyethylene (rPE) and pigments (Cp) are common additives, but their effects require careful study.

Purpose of the Study:

• To optimize key factors in rotational molding composites: recycled polyethylene (rPE) content, pigment (Cp) content, and peak internal air temperature (PIAT).
• To investigate the influence of these factors on mechanical properties, surface characteristics, thermal stability, and environmental stress cracking resistance (ESCR).
• To establish correlations between ultrasonic signals and internal stress for performance prediction.

Main Methods:

• Systematic variation of rPE content (0-50%), Cp content (0-2%), and PIAT (170-230°C).
• Characterization of composite properties including elastic modulus (E), impact strength (MFEsp), contact angle (θ), IR spectroscopy, DTA-TG analysis, and ESCR.
• Ultrasonic testing to measure the amplitude of the third harmonic (β) as an indicator of internal stress.

Main Results:

• Increased rPE and Cp slightly enhanced surface hydrophilicity.
• PIAT significantly impacted all studied composite characteristics.
• A strong correlation was observed between β, ESCR, MFEsp, and E, validating β as a quantitative indicator of internal stress.
• Optimal conditions identified as 30% rPE, 0.5% Cp, and 195°C PIAT for minimal internal stress and superior performance.

Conclusions:

• The study successfully optimized rotational molding parameters for rPE/pigment composites.
• Developed nomograms enable prediction and selection of rPE and Cp content based on PIAT and desired mechanical properties (MFEsp, β).
• The findings provide a pathway to enhance the performance and service life of rotomolded products through controlled composition and processing.