Solidification behavior of PLLA/nHA nanocomposites

Delabarde, Claire; Plummer, C. J. G.; Bourban, P.-E.; Månson, J.‐A. E.

doi:10.1016/j.compscitech.2010.04.024

Cited by 20 publications

(17 citation statements)

References 37 publications

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“…In the case of foam A, the small exotherm in the temperature range immediately below the main melting peak in the absence of nHA (Fig. 8a), characteristic of a transformation from the less stable a 0 crystalline phase of PLLA to the a phase during the scans, was again consistent with a crystallization temperature B110°C [39]. Indeed, very similar thermal Fig.…”

Section: Crystallization Behaviorsupporting

confidence: 58%

“…A screw rotation rate of 110 rpm, a temperature of 200°C and a residence time of 4 min were used to prepare PLLA compounds containing 0, 2 and 4.17 vol% of nHA in granulate form, which were subsequently stored at -18°C (at higher nHA contents, it became difficult to introduce the dry mix into the extruder). These conditions led to uniform dispersions of the nHA particles in the PLLA matrix as demonstrated elsewhere [39] (90 vol% of the particles had a diameter less than 980 nm and 50 vol% had a diameter less than 360 nm). Approximately 5 g of the compounded PLLA/nHA granulate was then loaded into an open cylindrical mold (25 mm in diameter and 35 mm in height) and foamed using a high-pressure, high-temperature autoclave (SITEC-Sieber Engineering, Switzerland).…”

Section: Methodsmentioning

confidence: 88%

“…It may also influence the tensile modulus and fracture toughness [37,38], and the morphology of semicrystalline polymers such as PLLA. Increases in the spherulite nucleation density have already been reported in PLLA in the presence of layered silicates [35] and nHA [39], coupled with decreased spherulite growth rates, which may be accounted for by strong increases in melt viscosity. However, to the authors' knowledge, the effect of well dispersed nHA on PLLA foams obtained by supercritical fluid foaming has yet to be described in detail in the open literature.…”

Section: Introductionmentioning

confidence: 96%

“…Crystallization generally occurred somewhat more rapidly in the presence of nHA, owing to a small but significant increase in the density of spherulite nucleation at a given temperature or cooling rate [39]. The CCT curves were assumed to provide some indication of the crystallization rates during the foaming process, although one should bear in mind: (i) the possible plasticizing effect of residual dissolved CO 2 after depressurization [41,55,56]; (ii) that the temperatures measured inside the autoclave did not necessarily give a precise indication of the local temperatures within the PLA; (iii) the influence of deformation on the crystallization rates [55,57].…”

Section: Crystallization Behaviormentioning

confidence: 99%

See 3 more Smart Citations

Biodegradable polylactide/hydroxyapatite nanocomposite foam scaffolds for bone tissue engineering applications

Delabarde

Plummer

Bourban

2012

J Mater Sci: Mater Med

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Supercritical carbon dioxide processing of poly-L-lactide (PLLA)/hydroxyapatite (nHA) nanocomposites was investigated as a means to prepare foams suitable as scaffolds in bone tissue engineering applications. For given foaming parameters, addition of nHA to the PLLA gave reduced cell sizes and improved homogeneity in the size distribution, but did not significantly affect the degree of crystallinity, which remained of the order of 50 wt% in all the foams. The compressive modulus and strength were primarily influenced by the porosity and there was no significant reinforcement of the matrix by the nHA. The mechanical properties of the foams were nevertheless comparable with those of trabecular bone, and by adjusting the saturation pressure and depressurization rate it was possible to generate porosities of about 85 %, an interconnected morphology and cell diameters in the range 200-400 lm from PLLA containing 4.17 vol% nHA, satisfying established geometrical requirements for bone replacement scaffolds.

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Section: Crystallization Behaviorsupporting

confidence: 58%

Section: Methodsmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 96%

Section: Crystallization Behaviormentioning

confidence: 99%

See 2 more Smart Citations

Biodegradable polylactide/hydroxyapatite nanocomposite foam scaffolds for bone tissue engineering applications

Delabarde

Plummer

Bourban

2012

J Mater Sci: Mater Med

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“…Previous gel permeation chromatography (GPC) studies of PLLA with comparable intrinsic viscosity have indicated a polydispersity of 1.5 and a weight average molar mass, M w , of about 150,000 g/mol, which decreases by approximately 10% after compounding. [12] Hydroxyapatite nanopowder (nHA, nominal mean diameter < 200 nm from BET analysis, Sigma-Aldrich) was used without further purification or thermal treatment.…”

Section: Experimental Partmentioning

confidence: 99%

Microdeformation in Poly‐L‐lactide and Poly‐L‐lactide + Hydroxyapatite Nanocomposite Thin Films

Plummer

Choo

Delabarde

2012

Macromolecular Symposia

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Summary: In order to gain new insight into failure mechanisms in poly-L-lactide (PLLA) and PLLA þ hydroxyapatite nanocomposites, transmission electron microscopy has been used to investigate room temperature microdeformation in electron transparent thin films of these materials subjected to various heat treatments and deformed in tension using the ''copper grid'' technique. In amorphous PLLA the dominant microdeformation mechanism was crazing. Localized fibrillar deformation zones (DZs) were also observed in semicrystalline films, tending to propagate in regions where the lamellar trajectories were at high angles to the tensile axis. Thus, in spherulitic films, in which the lamellae formed well-defined stacks with approximately straight trajectories at the scale of the spherulite radii, individual DZs were observed to propagate over relatively large distances, as in the amorphous films. On the other hand, films cold crystallized by heating from the glassy state showed more homogeneous lamellar textures. These were associated with a relatively high density of low aspect ratio DZs. Addition of well dispersed nanosized hydroxyapatite (nHA) to the amorphous PLLA films was also found to result in an increase in the craze density, attributed to stress concentrations associated with void formation at the PLLAparticle interfaces during deformation. However, interpretation was less straightforward in cold crystallized PLLA þ nHA thin films, owing to a correlation between the lamellar texture and the nHA particles. In this case, both void formation and favorable lamellar orientations may have contributed to initiation of the DZs in the vicinity of the particles. The results are argued to be broadly consistent with previous observations of the behavior of bulk PLLA and PLLA þ nHA films with a range of microstructures, in which there was evidence for an improvement in ductility in the presence of the nHA, again attributed to voiding at the PLLA-particle interfaces.

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Degradable and Bioactive Synthetic Composite Scaffolds for Bone Tissue Engineering

Boccaccını

Chatzistavrou

Blaker

et al. 2012

Degradation of Implant Materials

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Solidification behavior of PLLA/nHA nanocomposites

Cited by 20 publications

References 37 publications

Biodegradable polylactide/hydroxyapatite nanocomposite foam scaffolds for bone tissue engineering applications

Biodegradable polylactide/hydroxyapatite nanocomposite foam scaffolds for bone tissue engineering applications

Microdeformation in Poly‐L‐lactide and Poly‐L‐lactide + Hydroxyapatite Nanocomposite Thin Films

Degradable and Bioactive Synthetic Composite Scaffolds for Bone Tissue Engineering

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