SCHEDULED MAINTENANCE
Shape memory behaviour of HA-g-PDLLA nanocomposites prepared via in situ polymerization
Abstract
The shape memory properties of hydroxyapatite-graft-poly(D,L-lactide) (HA-g-PDLLA) nanocomposites were investigated in the present study. Hybrid nanocomposites with various HA proportions (5, 10, 15 and 25 wt%) were prepared via in situ grafting polymerization. It is found that the nanocomposites exhibit various shape memory (SM) performances with different HA loadings. Excellent shape memory properties were found for HA-g-PDLLA nanocomposites with 15 wt% inorganic HA proportions, observed through a well-established four-step SM programming cycle method. However, at low HA loading (including pure PDLLA), the samples experienced a severe relaxation process, which caused a plastic, irreversible deformation of the sample and resulted in a poor SM recovery ratio. In addition, the shape memory behaviours of HA25-g-PDLLA nanocomposites and HA25/PDLLA blends were compared. Due to the serious relaxation process caused by the weak interaction forces of hydrogen bonding between HA and PDLLA, the HA25/PDLLA blends had much worse shape recovery ability than the HA25-g-PDLLA nanocomposites.
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