Inhibition of phase transformation from β- to α-tricalcium phosphate with addition of poly (L-lactic acid) in selective laser sintering
Abstract
Purpose
The paper aims to fabricate an α-tricalcium phosphate (TCP) scaffold with an interconnected porous structure via selective laser sintering (SLS). To inhibit the phase transformation from β- to α-TCP in fabrication process of porous scaffolds, a small amount (1 weight per cent) of poly (L-lactic acid) (PLLA) is added into β-TCP powder to introduce the transient liquid phase.
Design/methodology/approach
The paper opted for the transient liquid phase of melting PLLA to decrease the sintering temperature in SLS. Meanwhile, the densification of β-TCP is enhanced with a combined effect of the capillary force caused by melting PLLA and the surface energy of β-TCP particles. Moreover, the PLLA will gradually decompose and completely disappear with laser irradiation.
Findings
The testing results show the addition of PLLA enables the scaffolds to achieve a higher β-TCP content of 77 ± 1.49 weight per cent compared with the scaffold sintered from β-TCP powder (60 ± 1.65 weight per cent), when the laser energy density is 0.4 J/mm2. The paper provides the mechanism of PLLA inhibition on the phase transformation from β- to α-TCP. And the optimum sintering parameters are obtained based on experimental results, which are used to prepare a TCP scaffold with an interconnected porous structure via SLS.
Research limitations/implications
This paper shows that the laser energy density is an important sintering parameter that can provide the means to control the micro-porous structure of the scaffold. If the laser energy density is too low, the densification is not enough. On the other hand, if the laser energy density is too high, the microcracks are observed which are attributed to the volume expansion during the phase transformation from β- to α-TCP. Therefore, the laser energy density must be optimized.
Originality/value
The paper provides a feasible method for fabricating TCP artificial bone scaffold with good biological and mechanical properties.
Keywords
Acknowledgements
This work was supported by the following funds: The Natural Science Foundation of China (51222506, 81000972); The foundation for the author of national excellent doctoral dissertation of China(2010 32); Program for New Century Excellent Talents in University (NCET-10-0792, NCET-12-0544); The Fundamental Research Funds for the Central Universities(2011 JQ005); Project supported by the Fok Ying-Tong Education Foundation, China (131050); and The Open-End Fund for the Valuable and Precision Instruments of Central South University.
Citation
Shuai, C., Zhuang, J., Peng, S. and Wen, X. (2014), "Inhibition of phase transformation from β- to α-tricalcium phosphate with addition of poly (L-lactic acid) in selective laser sintering", Rapid Prototyping Journal, Vol. 20 No. 5, pp. 369-376. https://doi.org/10.1108/RPJ-03-2013-0037
Publisher
:Emerald Group Publishing Limited
Copyright © 2014, Emerald Group Publishing Limited