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    Calcium silicate/poly(ethylene terephthalate) biomaterials via ring-opening polymerization
    (2012-10-01)
    Suebwongnat, Suebpong
    ;
    Jianprasert, Apichaya
    ;
    Siriphannon, Punnama
    ;
    Monvisade, Pathavuth
    Calcium silicate/poly(ethylene terephthalate) (CS/PET) composites were synthesized via ring-opening polymerization (ROP). CS raw material was synthesized by coprecipitation of calcium nitrate tetrahydrate and tetraethyl orthosilicate. Commercial grade PET was cyclodepolymerized under high dilution technique to cyclic oligo(ethylene terephthalate) (C-OET) raw material. The CS/PET precomposites were prepared by mixing 60:40 (C6P4) and 50:50 (C5P5) wt% of CS powder and C-OET with the presence of 3 mol% of dibutyl tinoxide catalyst (with respect to the cyclic) then shaped the pre-composites into cylindrical pellets. The presented C-OET in the pre-composites was ring-opening polymerized to obtain PET film covering on the CS grains with the different reaction temperatures as 180, 200 and 250 °C under vacuum for 24 h. Thermogravimetric analysis indicated that the ROP-PET content in the C5P5 and C6P4 composites were about 46-48 and 35-38 wt%, respectively. The melting points (T<inf>m</inf>) of ROP-PET of all composites were in a range of 233-246 °C. Compressive strength of the CS/ PET composites was significantly increased from 4.8 MPa of the neat CS to 31.0 MPa for the C5P5 composites at the ROP temperature of 250 °C. The CS/PET composites faster induced the continuous-phase formation of hydroxyapatite (HAp) nanocrystals on their surfaces than the HAp/polymer composites. The induction occurred within 7-day soaked in the simulated body fluid (SBF) solution, indicating the bioactivity of the CS/PET composites. © 2012 Springer Science+Business Media Dordrecht.
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    Poly(ethylene terephthalate)/hydroxyapatite biomaterials: Preparation, characterization, and in vitro bioactivity
    (2009-02-01)
    Siriphannon, Punnama
    ;
    Monvisade, Pathavuth
    Poly(ethylene terephthalate)/hydroxyapatite (PET/HAp) composites were prepared by mixing HAp powder with a mixture solution of cyclic oligo(ethylene terephthalate) (C-OET) and dibutyl tinoxide catalyst in dichrolomethane, and then shaping the precomposites in cylindrical pellets. The C-OET in the precomposites was ring-opening polymerized (ROP) to PET under vacuum at 250°C for 24 h. The PET/HAp composites were formulated with HAp to PET ratios of 60:40 (H6P4) and 50:50 (H5P5). The ROP-PET in the composites was present as a thin-layer coating on the HAp grains and evenly distributed throughout the samples. Compressive strength of the PET/HAp composites was significantly increased from 8 MPa of the H10P0 to 17 and 29 MPa for H6P4 and H5P5, respectively. In vitro bioactivity of the PET/HAp composites was studied by soaking in simulated body fluid (SBF) at 36.5°C for 7-28 days. After prolonged soaking, the HAp nanocrystals precipitated from the SBF solution and formed as a layer of globular aggregates, coated on the composite surfaces. The H6P4 composite showed faster formation rate of nano-HAp than the H5P5 composite, indicating that the bioactivity of PET/HAp composites depended on the amount of HAp. © 2008 Wiley Periodicals, Inc.
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