Papers by Keyword: Calcium Polyphosphate

Abstract: This Magnesium-doped calcium polyphosphate (MCPP) porous bioceramics of different magnesium content were prepared by the method of solid reaction sintering. The effect of magnesium on the structure and density of magnesium-doped calcium polyphosphate bioceramics was studied. Phases, cross section morphologies and porosity of MCPP bioceramics were analyzed with X-ray diffraction(XRD) and scanning electron microscopy (SEM). The results show that MCPP ceramics were successfully prepared by the solid reaction sintering, and the bending strength of ceramics began to increase and then to decrease with increasing amounts of magnesium content apart with the improvement of the stability improved.

Abstract: Calcium polyphosphate (CPP) bioceramics with different Ca/P ratios were fabricated. It was shown that the contents of CPP in the sintered ceramics decrease with the increasing Ca/P ratios (0.5-1.0) of the precursors. The higher the Ca/P ratios of precursors were, the more complex the phases of polymerization were. The compressive strengths of ceramics sintered at the same temperature showed a linear decreasing tendency with the increasing Ca/P ratio.

Abstract: This paper describes a comparative investigation into the in vitro solubility of the calcium polyphosphates, γ-Ca(PO3)2 and β-Ca(PO3)2. The differing arrangement of their polyphosphates chains appears to result in significant dissolution of γ-Ca(PO3)2 polymorph over the β-Ca(PO3)2 polymorph, which exhibits limited dissolution. These properties are discussed with respect to structure and thermodynamic stability.

Abstract: Porous calcium polyphosphate(CPP) have been shown to promise for tissue engineered implant application. The process from Ca(H2PO4)2 to CPP, as a polycondensation reaction, has been researched to evaluate the number average degree of polymerization. CPP with different degree of polymerization were prepared by controlling the calcining time. Amorphous and different crystalline CPP were prepared by the quenching from the melt and crystallization of amorphous CPP. Two specimens were soaked into citric acid and tris-buffer solution for 1 to 30 days. The weight loss of CPP with different degree of polymerizations and crystal types are different. With the increasing of degree of polymerization, the weight loss during the degradation is decreasing, contrarily the strength of CPP is increasing. The degradation velocity of amorphous CPP, α-CPP,β-CPP and γ-CPP with the same degree of polymerization decreased in turn at the same period. The full weight loss period of CPP can be changed between 17 days and more than 1 year. The degradation and deposition was faster in the citric acid than the tris-buffer solution.

Abstract: Particle filled composite and interpetrating phase composite (IPC) structures are investigated for the production of a biodegradable composite for use as a fixation device in various osteosynthesis applications. The composites consist of calcium polyphosphate, present as either a dispersion of 106 – 150 µm particles or as a sintered scaffold-like structure having open porosity in the range of 18 – 35 volume percent, and a polyvinyl acid-carbonate copolymer that is cured in situ via free radical polymerization. The performance of each composite structure is evaluated in terms of its three-point bend strength and elastic constant. Plane strain fracture toughness values are also presented for IPC samples based on CPP sintered to have 30 volume percent porosity.

Abstract: This study describes the use of flux methods as a novel synthetic route to some known and new calcium polyphosphates, with a view to developing new biomaterials. Calcium acid pyrophosphate, CaH2P2O7, which is a known precursor in the preparation of many other calcium polyphosphates, has been synthesized as a pure crystalline phase in a single step synthesis at temperatures between 190-250 °C. Reaction temperatures between 250 and 400 °C led to the synthesis of γ-Ca(PO3)2, a previously uncharacterised polymorph of calcium metaphosphate. Lattice parameters of a = 10.3682(1) Å, b = 9.5001(1) Å, c = 9.5552(1) Å, with β angle of 93.45(4)° were obtained from powder X-ray diffraction data. A subsequent increase in reaction temperature to 550 °C was found to produce a calcium polyphosphate glass. A detailed study of thermal stability of CaH2P2O7 was also performed to determine phase stability and decomposition pathways.