Choice of dispersants for the nano-apatite filler of polylactide-matrix composite biomaterial

The aim of this study is to compare de-aggregative ability of common organic dispersants for the acicular nano-apatite crystallite with main composition of calcium hydroxyapatite (HA) as a filler of composite containing polylactide (PLA) matrix. Firstly, the acicular nano-apatite powders with an average length of 70–120 nm were synthesized based on traditional chemical co-precipitation and freeze-drying techniques. Common organic dispersants including tetrahydrofuran, acetone, chloroform, N,N-dimethyl formamide (DMF) and ethanol were then employed to disperse synthetic freeze-dried ultra-fine nano-powders. The observations and weight of sediments showed that nano-apatite suspension dispersed by DMF and ethanol presented homogeneous and stable colloid after vigorly stirred for 24 h and then kept still for same time, respectively. Results of particle measurements and viscosity measurement illuminated that a large number of the nano-apatite particles with an average dimension of 297.86 nm and viscosity of 0.8872 cP in DMF suspension could be dispersed up to 91.28 nm by the DMF dispersant and the DMF dispersant could minimize agglomeration between the apatite ultra-fine nano-powders. DMF is a more effective and appropriate dispersant to disperse the apatite nano-fillers than chloroform, tetrahydrofuran, acetone and ethanol, when the nano-apatite/PLA composite biomaterials were prepared.     

Synthesis and properties of a copolymer of poly(l,4-phenylene sulfide)-poly(2,4-phenylene sulfide acid) and its nano-apatite reinforced composite

A new kind of copolymer of poly(1,4-phenylene sulfide)-poly(2,4-phenylene sulfide acid) (PPS-PPSA) and its nano-apatite (NA) composite have been obtained by polycondensation in l-methly-2-pyrrolidone (NMP). The NA content in the composite can reach 60 wt.%. The structures and properties of copolymer and its NA composite were studied though infrared spectroscopy. X-ray photoelectron spectroscopy, transmission electron microscopy, atomic force microscopy. The copolymer has high molecular weight and excellent thermal properties. There is a stable interface formed between NA and PPS-PPSA copolymer in the composite. NA keeps the original morphological structure and crystal behavior in the composite. The composites have good homogeneity and outstanding thermal stability. NA particles are uniformly distributed in the composite. The diameter of apatite in the composite is about 40-60 nm. The PPSA in the copolymer can increase the affinity to apatite and does not decrease the melting point and thermal stability of copolymer.     

Tissue engineering scaffold material of nano-apatite crystals and polyamide composite

A new kind of tissue engineering scaffold materials of needle-like nano-hydroxyapatite (n-HA) and polyamide (PA) biocomposite is prepared by co-solution, co-precipitation method and water treatment under normal atmospheric pressure. The n-HA crystals uniformly distribute in the composite with a crystal size of 10-20 nm in diameter by 70-90 nm in length. The n-HA/PA composite has good homogeneity, high n-HA content (65 wt%), and high bioactivity. Strong molecule interactions and chemical bondings are present between the n-HA and PA in the composite, which are verified by IR, XPS and XRD. The composite has excellent mechanical properties close to the natural bone. The porous 3-D scaffold is made by injection foaming method, which has not only macropores, but also micropores on the walls of macropores. The porosity is 80% and the average macropore diameter is about 300 μm of the composite.The n-HA/PA composite can be used for tissue engineering and bone repair or substitute.