Influence of Additives on Rheological Properties of Calcium Phosphate Cement Ⅰ. Polyvinylpyrrolidone

The influence of polyvinylpyrrolidone (PVP) on the rheological characteristics of calcium phosphate cement (CPC) was investigated with an advanced rheometric expansion system rheometer. By the addition of PVP of different K values into the setting liquid, the rheological properties of CPC slurry could be improved. The viscosity curves were obtained by steady transient test to evaluate the characters of flowage and the thixotropic properties were measured by the thixotropic loop test. The results show that the CPC slurry is a typical shear-thinning fluid and the addition of PVP does not change this property of CPC slurry. But due to the existence of PVP, the viscosity of CPC slurry and the area of thixotropic loop both increase and the restorability is also improved. So the stability of CPC slurry is improved. With the increasing of PVP concentration (w_(K30)=0.01~0.20,w_(K90)=0.002~0.04), the viscosity and thixotropy of CPC slurry both increase and the restorability decreases. In conclusion, when w_(K90)=0.04 or w_(K30)=(0.20,) the PEG solution are more suitable for the CPC as an injectable material. The rheological properties of CPC slurry are all improved.