In vitro flexural properties of hydroxyapatite and self‐reinforced poly(L‐lactic acid)

Abstract

Poly(L-lactic acid) (PLLA) has been used for fracture fixation devices, but its use is limited because of its poor biocompatibility and mechanical properties. The effects of extrusion, incorporation of hydroxyapatite (HA) and self-reinforced composites (SRCs) on the resultant mechanical properties of PLLA were examined. Samples were conditioned for up to 52 weeks in PBS at 37 degrees C. Extrusion did not adversely affect the mechanical properties of PLLA. After in vitro conditioning, a slight but significant reduction in the strain to failure and modulus was seen. HA (10-40%) by weight was evenly distributed into PLLA using an intermeshing twin-screw extruder. As ceramic content increased, the initial modulus increased but flexural strength decreased. After immersion, the modulus of all HA-PLLA blends was lower than PLLA. HA particles did not form a strong bond with the PLLA, which promoted easier degradation of the HA-PLLA matrix. SRCs showed a higher modulus and strength when compared to all materials except the modulus of 30 and 40% HA-PLLA composites before immersion. Water preferentially attacked the matrix of the composite, leading to more fiber pullout, but the fiber orientation maintained the advantages in strength and modulus up to 24 weeks in vitro.

The effect of cellulose nanowhiskers on the flexural properties of self-reinforced polylactic acid composites

“…In addition, the fibre processing conditions and further improvement of their initial strength could improve the flexural properties of SRCs. For SR PLA--CNW composites the flexural strength and modulus increased to 122 MPa (~48% increase) and 5.5 GPa (~39% increase) respectively, which was comparable with other studies on SR--PLLA composites [36]. This increase in mechanical properties was attributed to the mechanical interlocking made possible by the nanofillers (CNWs) deposits on the PLA fibres within the SR PLA--CNW composite, which improved the interfacial properties between the fibre and matrix [51].…”

“…The control SR PLA composite had a flexural strength and modulus of 82 MPa and 3.9 GPa, respectively, which was lower than values found by Wright--Charlesworth et al [36] for SR--PLLA composites (139 MPa flexural strength and 5.4 GPa modulus). However, in this study PLA (Natureworks-3251D) resin was investigated which contained a lower amount of L--lactide compared to the PLLA resin used in the cited work [36].…”

“…The temperature and pressure used in this study played an important role in preserving the fibre structure. We therefore used the processing parameters (95 o C and 90 bar pressure) showed by Wright--Charlesworth et al [36] to provide the best combination of flexural strength, modulus and ductility in SR PLLA composites.…”

“…However, in this study PLA (Natureworks-3251D) resin was investigated which contained a lower amount of L--lactide compared to the PLLA resin used in the cited work [36]. In addition, the fibre processing conditions and further improvement of their initial strength could improve the flexural properties of SRCs.…”

Evaluation of PLAGA/n-HA Composite Scaffold Bioactivity in vitro

“…It has been widely used as an addictive to form composite materials with both synthetic and natural polymers [15,16]. Recently, nano hydroxyapatite (n-HA) attracted significant attention as the exceptionally large surface area of these particles provides extraordinary performance as the second phase added into the scaffolds [17,18].…”