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Author: search.filters.author.Siriphannon, PunnamaSubject: search.filters.subject.Bioactive materials

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    Preparation and characterization of hydroxyapatite/poly(ethylene adipate) hybrid composites
    (2008-06-01)
    Siriphannon, Punnama
    ;
    Monvisade, Pathavuth
    Hydroxyapatite/poly(ethylene adipate) (HAp/PEA) composites were prepared by in situ ring-opening polymerization of cyclic oligo(ethylene adipate) (C-OEA) within the porous HAp templates. HAp was firstly prepared by a co-precipitation method using calcium hydroxide and phosphoric acid and then shaped as a rectangular porous template. PEA precursor was synthesized by bulk polymerization of dimethyl adipate and ethylene glycol in the presence of tetraisopropyl orthotitanate. C-OEA was obtained by cyclo-depolymerization of the PEA precursor under high dilution condition using dibutyl tinoxide as a catalyst. The HAp/PEA composites were prepared by immersing the porous HAp templates in the mixture solution of C-OEA and dibutyl tinoxide catalyst overnight and ring-opening polymerizing at 180, 200 and 220°C for 24 h. The ring-opening polymerized PEA formed as a thin film coating on the surface of porous HAp template. The HAp/PEA composites contained PEA in the range of 20-26 wt%. The weight-average molecular weights of ring-opening polymerized PEA were in the range of 3800-4450 g/mol. Compressive strength of the HAp/PEA composite was significantly increased from 25 MPa in the porous HAp template to 140 MPa in the composite. © 2008 VSP.
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    Comparative study of the formation of hydroxyapatite in simulated body fluid under static and flowing systems
    (2002-01-01)
    Siriphannon, Punnama
    ;
    Kameshima, Yoshikazu
    ;
    Yasumori, Atsuo
    ;
    Okada, Kiyoshi
    ;
    Hayashi, Shigeo
    α-CaSiO<inf>3</inf> ceramics of nominal composition CaO 46.0, SiO<inf>2</inf> 54.0, and Na<inf>2</inf>O 0.4 mass% were soaked in simulated body fluid (SBF). The soaking systems were maintained under both static and flowing conditions to study their effect on the formation of hydroxyapatite (HAp). Two different flowing systems were designed for soaking, namely, a closed system using a fast flow rate of about 2.8 mL/s (circulating system) and an open system using a slow flow rate of about 40 mL/day (slow flowing system). The HAp layer in all samples initially formed as a rough layer of ball-like particles. Under a fast flow of SBF solution, silica gel particles peeled from silica-rich interlayer during the first soaking period. The silica gel particles then reattached to the product HAp layer and induced the formation of new HAp particles of smaller size. In the slow flowing system, the rough HAp layer initially formed on the ceramic surfaces became gradually smoother after prolonged soaking. The formation rate and thickness of the HAp layer decreased with increasing flow rate of the SBF solution. These results indicate that flowing SBF solution gives rise to differences in the formation rates, formation behavior, and microstructure of the HAp layer. © 2002 John Wiley & Sons, Inc.
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    Hydroxyapatite formation on CaSiO3 ceramics in protein containing system
    (2001-01-01)
    Okada, Kiyoshi
    ;
    Siriphannon, Punnama
    ;
    Kameshima, Yoshikazu
    ;
    Yasumori, Atsuo
    ;
    Hayashi, Shigeo
    α-CaSiO<inf>3</inf> ceramics with a nominal composition of CaO 46.0, SiO<inf>2</inf> 54.0, and Na<inf>2</inf>O 0.4 wt% were soaked in two different solutions, simulated body fluid (SBF) and α-minimum essential medium (α-MEM), to study the effect of protein on the formation of hydroxyapatite (HA). The SBF solution contained the same inorganic salts as in the human blood plasma, while the α-MEM solution contained both inorganic salts and various proteins. Both soaking systems were maintained at 36.5°C and a flow rate of about 40 ml/day for various periods of times. A complete coating of HA formed on the surface of the α-CaSiO<inf>3</inf> ceramics in both solutions, but with different formation behavior and microstructure. The HA formed in the α-MEM system had ball-like particle morphology with a smaller particle size than the material formed in the SBF system. Cristobalite and/or unknown silicate phase coprecipitate with the HA in the α-MEM system but not in SBF. The HA layer formed on the ceramic surface achieved a thickness of about 80 and 93 μm after 20 days soaking in SBF and α-MEM solutions, respectively. The presence of protein in the α-MEM solution was considered to effect the microstructure of HA and possibly enhanced HA precipitation on the α-CaSiO<inf>3</inf> ceramic. © 2002 Trans Tech Publications, Switzerland.