Effect of glycerol concentrations on the mechanical properties of additive manufactured porous calcium polyphosphate structures for bone substitute applications

摘要

Introduction: In this study, the focus is on the development of a new liquid binder to be used with calcium polyphosphate (CPP) [University of Toronto, Toronto, ON, Canada] powders in additive manufacturing (AM) of biocompatible and bioresorbable bone substitutes. From the different number of the solutions which have been proposed for this system in literature, ZbTM 58 [3D Systems, Rock Hill, USA] liquid binder has been previously employed in studies on CPP substitutes, with some limitations. The purpose of the new liquid binder is to be used as an alternative to the commercially available counterpart in manufacturing bioceramic bone substitutes. Materials and Methods: Nine different water-based solutions were prepared to achieve this goal by alternating the percent of glycerol (GLY) [EMD Chemicals, NJ, USA] (10, 12.5 and 15wt%) as the binding agent, and ethylene glycol diacetate (EGD) [Sigma-Aldrich, MO, USA] (0,0.75 and 1,5wt%) acting as a flow enhancer. To narrow done the number of solutions to the best candidates, an image processing algorithm was performed, which indicated the better print quality for solutions with 1.5wt% of EGD. Therefore three solutions with 1.5wt% of EGD and 10,12.5 and 15wt% of GLY have been selected for manufacturing the CPP samples. ZPrinter310-Plus system [3D Systems, Rock Hill, USA] was used for additive manufacturing of samples. In order to complete this process, a combination of CPP (90wt%) with polyvinyl alcohol (PVA) [Alfa Aesar, Ward Hill, MA] (10wt%) was loaded on the system with the proper solution in each trial. Results and Discussion: The properties of samples in both the green and sintered phase were studied by different analyses such as porosity measurement, compressive strength, shrinkage analysis, and structural characterization using SEM. Among these specimens, the one manufactured by binder solution consisting of 12.5wt% of GLY and 1.5wt% EGD dissolved in distilled water, suggests the highest value for mechanical strength after sintering (34.6 ± 5.8 MPa) which is similar with previous study results obtained by employing the commercially available binder solutions (33.9 ± 6.3 MPa) Furthermore, this category of samples also had good sinter neck formation and an appropriate bulk porosity of 32.1 ±2.6%. Conclusion: A new water-based solution has been developed to be used for binder jetting additive manufacturing of the CPP bioceramic bone substitutes. This newly developed binder opens up the possibility of use for AM of components using other types of powder materials.