Search

Poly(lactide-co-glycolide)/bone meals composites using poly(lactide-co-glycolide) (PLGA) and bone meals (BM) as the starting materials were successfully prepared via solution dispersion method. Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction and BET were used to characterize the resulting PLGA and bone meals. The mechanical properties of composites were carried out by the three-point-bending test, and the micrographs of cross-section of composites were observed using SEM. The results indicate that both the bending strength and modulus of PLGA/BM composites increased with bone meals increasing up to 10 wt%, then decreased with bone meals content, indicating that the fracture feature of PLGA/BM composites changed from typical brittle to ductile fracture when the bone meals content changed from 0 to 10 wt% and from ductile to brittle facture while bone meals content ranging from 10 to 20 wt%. It was further confirmed by SEM images of composites. The biocompatibility results show that result...

HA/PLGA composites with and without APS-modification were successfully prepared via solution dispersion method. The mechanical test of composites was performed by the three-point-bending test and the micrographs of materials were observed using SEM. The results indicate that by surface modification, uniform HA particles without agglomeration were obtained. Furthermore, the bending strengths and moduli of APS-HA/PLGA composites are higher than those of unmodified composites, which both first increased and then significantly decreased with increasing the HA content. The biocompatibility results show that modified HA/PLGA composite are more favorable biomaterials for cell adhesion, differentiation and proliferation than unmodified composites.

Composite biomaterial composed of poly(L-lactide) (PLLA) and hydroxyapatite (HA) was obtained by using the combination of solvent evaporation technique and hot pressing. HA particles in the PLLA matrix were homogeneously dispersed. A typical morphology of brittle failure with a smooth fracture surface was observed. The addition of HA particles changed significantly the appearance of the impact fracture surface to a pattern of multiple cracks. With the increasing of the amount of the HA, the bending strength of composite decreases while the bending modulus increases. The PLLA/HA composite exhibits improved cell compatibility due to the good biocompatibility of the HA particles.

Bioactive and bioresorbable composite was fabricated based on poly-L-lactide (PLLA) and bioactive glass (average particle size: 4.24 µm) by the combination of solvent evaporation technique and hot pressing. Bioactive glass granules are distributed homogeneously in the composite. With the increasing of the amount of bioactive glass, the bending strength and shearing strength of composite decrease while the bending modulus increases. PLLA/bioactive glass composites present a typical morphology of brittle failure with a smooth fracture surface. The biocompatibility test shows that the bioactive glass existing in the composite facilitates both adhesion and proliferation of rat fibroblast on the PLLA/bioactive glass composite film.

The viscoelastic properties of the suspension of monodisperse spherical silica produced by hydrolysis of tetraethoxysilane in alcohol solvent with ammonia as a catalyst in polyethylene glycol (PEG) were studied. The results show that the SiO2/PEG suspension possesses the reversible shear thinning and shear thickening behaviors. In the shear thinning region, the loss modulus (G″) almost remains unchanged, whereas the storage modulus (G′) decreases. In the shear thickening region, G″ and G′ increase for the formation of the “clusters”. The larger G″ over G′ in all the stress studied shows that the system mainly possesses the viscous property, and that the energy dissipated(E d) is larger than that stored. E d of this suspension is proportional to the maximum strain (γ max) rising with the exponent of 1.92 under low shear stress; however, in the shear thickening region, E d is proportional to γ max rising with the exponent of 5.00.

The influence of non-isothermal melt crystallization on thermal behavior and isothermal melt crystallization kinetics of poly-L-lactide (PLLA) were investigated by differential scanning calorimetry (DSC), polarizing micrograph (POM) and x-ray diffraction (XRD). Crystallization performed at lower cooling rates (2°C·min−1) is accompanied by a variation of the kinetics around 118°C. The glass transition temperature of PLLA decreases with increase of cooling rate, and the crystallinity at the end of crystallization increases with decreasing cooling rate. The size of PLLA spherulites increases with a decrease in the cooling rate, and PLLA becomes almost amorphous cooled at rapid rate (>10°C·min−1). PLLA exhibits an Avrami crystallization exponent n = 3.01±0.13 in isothermal crystallization in the range from 90°C to 140°C. According to Hoffman-Lauritzen theory, two crystallization regime are identified with a transition temperature occurring at 118°C, and the value of Kg(II)/Kg(III) is 2.17 [Kg(II) = 6.025 × 10...

The rheological behavior of fumed silica suspensions in polyethylene glycol(PEG) was studied at steady and oscillatory shear stress using AR 2000 stress controlled rheometer. The systems show reversible shear thickening behavior and the shear-thickening behavior can be explained by the clustering mechanism. The viscosity and the degree of shear-thickening of the systems strongly depend on the mass fraction of the silica, the molecular weigh of PEG and the frequency used in the rheological measurement. The silica volume fraction of the systems is 1.16%–3.62%, corresponding to the mass fraction of 4%–9%. The shear-thickening taking place in the low volume fraction may contribute to the fractal nature of the silica. At oscillatory shear stress, when the shear stress is less than the critical stress, the storage modulus decreases significantly, meanwhile the loss modulus and the complex viscosity almost remain unchanged; when the shear stress is larger than the critical stress, the storage modulus, the loss modulus and the complex viscosity increase with the increase of shear stress. The loss modulus is larger than the storage modulus in the range of stress studied and both moduli depend on frequency.