Thermoplastic Polyureas with Excellent Mechanical Properties Synthesized From CO₂-Based Oligourea

Area of Science:

• Polymer Chemistry
• Materials Science

Background:

• Polyureas (PUas) are widely used polymers, but traditional thermoset forms lack recyclability.
• The influence of the isocyanate index (R index) on polyurea properties is not well understood.
• Developing recyclable and high-performance polyureas is crucial for broader industrial application.

Purpose of the Study:

• To investigate the effect of varying R indices on the synthesis and properties of thermoplastic polyureas (PUas).
• To identify an optimal R index for enhanced mechanical, thermal, and reprocessing characteristics.
• To advance the development of sustainable and versatile polyurea materials.

Main Methods:

• Synthesized thermoplastic polyureas (PUas) using a CO2-based oligourea (OUa) and 4,4'-diphenylmethane diisocyanate (MDI).
• Varied the R index (molar ratio of isocyanate to amine/hydroxyl groups) across different synthesis batches (R=1, 1.05, 1.11).
• Characterized the resulting PUas for mechanical properties (tensile strength, Young's modulus, toughness), thermal stability, and reprocessability.

Main Results:

• The R index significantly influences PUa molecular weight, structure, mechanical properties, and thermal stability.
• PUa synthesized with an R index of 1.05 (PUa-1.05) demonstrated optimal performance.
• PUa-1.05 achieved high tensile strength (≈75 MPa), Young's modulus (≈1100 MPa), and toughness (≈104 MJ·m-3), alongside excellent reprocessing capabilities.
• All synthesized PUas exhibited high thermal stability, with decomposition temperatures above 312°C.

Conclusions:

• The R index is a critical parameter for tailoring thermoplastic polyurea properties.
• An R index of 1.05 provides an optimal balance of mechanical strength, toughness, thermal stability, and reprocessability in PUas.
• This research offers a pathway to develop advanced, recyclable polyureas for diverse industrial applications.