Microstructural characteristics of calcium hydroxyapatite/poly-L-lactide based composites

Area of Science:

• Biomaterials Science
• Materials Engineering
• Composite Materials

Background:

• Hydroxyapatite (HAp) possesses excellent osteoinductive properties but suffers from low mechanical strength.
• Improving the mechanical integrity of HAp-based materials is crucial for biomedical applications.
• Polymer addition is a promising strategy to enhance HAp composite performance.

Purpose of the Study:

• To investigate the microstructural characteristics of hydroxyapatite/poly-L-lactide (HAp/PLLA) composites.
• To evaluate the effects of cold and hot processing methods on composite properties.
• To understand how processing parameters influence porosity and polymer wetting.

Main Methods:

• HAp/PLLA composites were prepared by mixing HAp granules with a PLLA chloroform solution.
• Chloroform was removed via vacuum evaporation.
• Dense compacts were formed using cold or hot pressing (98.10–294.3 MPa) at temperatures between 293–457 K for 15–60 min.
• Microstructural analysis was conducted using scanning electron microscopy (SEM).

Main Results:

• Processing conditions and PLLA content determine composite porosity, ranging from highly porous to nearly fully dense.
• Higher temperatures (457 K) and longer pressing times resulted in fully dense HAp/PLLA composites.
• SEM revealed that PLLA forms a continuous network, enhancing HAp hardening, though some HAp layers may remain polymer-free due to deep PLLA penetration.

Conclusions:

• Cold and hot pressing techniques offer control over HAp/PLLA composite microstructure and density.
• Optimized processing parameters can yield dense composites with improved mechanical properties.
• The study highlights the interplay between processing, polymer infiltration, and the resulting composite architecture.