The evolution of the structure and mechanical properties of fully bioresorbable polymer-glass composites during degradation

TL;DR

This study explores how bioresorbable polymer-glass composites change structurally and mechanically during degradation, aiming to improve cardiac stent materials with controlled property loss and enhanced performance.

Contribution

It provides new insights into the degradation behavior and mechanical evolution of polylactide-based polymer composites reinforced with phosphate glass, relevant for biomedical applications.

Findings

Modulus increased by up to 80% with phosphate glass reinforcement.

15wt.% glass composites maintained ductility similar to pure polymers.

Degradation involved water absorption and glass dissolution, with mechanisms suppressed by glass addition.

Abstract

Fully bioresorbable polymer matrix composites have long been considered as potential orthopaedic implant materials, however their combination of mechanical strength, stiffness, ductility and bioresorbability is also attractive for cardiac stent applications. This work investigated reinforcement of polylactide-based polymers with phosphate glasses, addressing key drawbacks of current polymer stents, and examined the often-neglected evolution of structure and mechanical properties during degradation. Incorporation of 15 - 30wt.% phosphate glass led to modulus increases of up to 80% under simulated body conditions, and 15wt.% glass composites retained comparable ductility to pure polymers, crucial for stent applications where ductility and stiffness are required. Two-stage degradation was observed, dominated by interfacial water absorption and glass dissolution. Polymer embrittlement mechanisms (crystallisation, enthalpy relaxation) were suppressed by glass addition, allowing composites to achieve a more controlled loss of mechanical properties during degradation, which could allow gradual transfer of loading to newly healed tissue. These results provide a valuable new system for understanding the structural and mechanical changes occurring during degradation of fully bioresorbable polymer matrix composites, providing important new data to underpin the design of effective cardiac stent materials.