Effect of heat treatment on setting behavior and compressive strength of tetracalcium phosphate cement: Fid-Bau Portal

Effect of heat treatment on setting behavior and compressive strength of tetracalcium phosphate cement

Lin, Kuan-Liang / Ju, Chien-Ping / Lin, Jiin-Huey Chern

The tetracalcium phosphate (TTCP) powder used for the study was fabricated from the reaction of dicalcium pyrophosphate (Ca2P2O7) and calcium carbonate (CaCO3). Since a 'whisker treatment' has been very effective in enhancing the properties of TTCP cement, the same heat treatment was used to treat the TTCP powder for the present study. To form a calcium phosphate cement (CPC) paste, the TTCP powder was mixed with a diammonium hydrogenphosphate ((NH4)2HPO4) hardening solution. The working time of the CPC was determined as the duration for which the paste was no longer moldable, while setting time was measured according to ISO 1566 standard method. One major result of this study was that the working/setting time of the present monolithic TTCP-derived CPC could be significantly changed by applying a simple heat treatment to TTCP powder. All the investigated heat treatment conditions caused the working/setting time to be-come longer than those without the heat treatment. From a practical point of view, among all heat treatment conditions investigated in this study, the heat treatment at about 200 deg C to 300 deg C for about 30 min to 120 min appears to be a suitable range for prolonging the working/setting time, while maintaining (in some cases even increasing) the compressive strength of the TTCP ce-ment. The XRD pattern of non-heat-treated TTCP powder showed a typical TTCP crystal structure. When the TTCP powder was heated to 300 deg C for 120 min or to 400 deg C for 30 min, apatite peaks were observed, indicating a phase transition from TTCP to apatite. When the powder was treated to 400 deg C for 120 min, apatite emerged as the dominant phase. The comparison between the XRD results and compressive strength data indicates that the compressive strength of CPC is closely related to the relative amount of apatite formed in the CPC. CPC derived from the highest temperature (400 deg C-treated powder had the smallest amount of apatite and the lowest compressive strength).