Polyethylene-Like Blends Amenable to Abiotic Hydrolytic Degradation

Area of Science:

• Polymer Science
• Materials Science
• Environmental Science

Background:

• Long-chain aliphatic polyester-18,18 (PE-18,18) possesses properties similar to high density polyethylene (HDPE) and can be recycled via depolymerization.
• However, PE-18,18's inherent stability limits its environmental degradability, contributing to plastic accumulation.
• Hydrolytic degradability is a crucial property for mitigating environmental plastic pollution.

Purpose of the Study:

• To develop a hydrolytically degradable version of PE-18,18.
• To investigate the material properties and degradation behavior of PE-18,18 blended with long-chain aliphatic poly(H-phosphonate)s (PP).

Main Methods:

• Melt blending of PE-18,18 with varying wt % of PP (0.5-20%).
• Processing of blends using injection molding and 3D printing.
• Characterization of mechanical properties (tensile testing), solid-state structure (X-ray diffraction), and crystallinity (DSC).
• Assessment of hydrolytic degradation in aqueous phosphate-buffered media at 25 °C using NMR and GPC.

Main Results:

• The PE-18,18/PP blends maintained HDPE-like tensile properties (stiffness, ductility) and crystallinity (≈70%).
• The PP component hydrolyzed completely within four months, while the PE-18,18 component showed partial hydrolysis.
• Significant reduction in molar mass (from 50-70 kg mol⁻¹ to 7-11 kg mol⁻¹) led to specimen embrittlement and fragmentation.

Conclusions:

• Melt blending PE-18,18 with PP effectively renders the polyester hydrolytically degradable.
• The resulting blends offer a promising route to HDPE-like materials with built-in environmental degradation mechanisms.
• The fragmentation of hydrolyzed blends is expected to accelerate mineralization, reducing plastic persistence in the environment.