Cement-forming acids citric acid

An interesting application concerns the chitosan- calcium phosphate cement. Chitosan or chitosan glycerophosphate mixed with calcium phosphate and citric acid forms an attractive injectable self-hardening system for bone repair or filling indications [134, 213, 214],... 

The setting time of the binder will depend on the amount of calcitmi chloroaluminate present, on the form of SO3 that is present, and on the SO3/AI2O3 ratio. Usually the cement sets faster than Portland cement. If required, a hydroxyc oxylic acid, such as citric acid, may be added to retard the setting process (Takuma et al, 1997). 

Figure7.11 Typical isothermal DSC measurements of the setting behaviour of brushite-forming calcium phosphate cements based on cement ( 3-tricalcium phosphate/monocalcium monophosphate) at 37°C, showing (a) the normalised heat flow of the exothermic setting reaction with time for fixed PLR 2.0 g/mL and (b) three different citric acid retardant concentrations and fixed retardant concentration of 800 mM citric acid and three different PLRs. While the citric acid concentration had an effect on the setting times, in terms of the time at which the maximum heat of reaction took place, the PLR did not. (From [24], Copyright 2006. Copyright John Wiley Sons Limited. Reproduced with permission.)...

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