Calcium silicate/poly(ethylene terephthalate) biomaterials via ring-opening polymerization

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 pre-composites 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 (Tm) 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.