Influence of the material properties of a poly(D,L-lactide)/β-tricalcium phosphate composite on the processability by selective laser sintering

Abstract

Complex 3D scaffolds with interconnected pores are a promising tool for bone regeneration. Such 3D scaffolds can be manufactured by selective laser sintering (SLS) from biodegradable composite powders. However, the mechanical strength of these scaffolds is often too low for medical application. We propose that the mechanical strength of laser-sintered scaffolds can be improved through composite powders with tailored properties (e.g., suitable powder particle size and melt viscosity for SLS). To prove this, two batches of a poly(D,L-lactide) (PDLLA)/β-tricalcium phosphate (β-TCP) composite powder with 50 wt% PDLLA and 50 wt% β-TCP were synthesized. The two batches differed in polymer particle size, filler particle size, and polymer molecular weight. Both batches were processed with identical SLS process parameters to study the extent to which the material properties influence how well a PDLLA/β-TCP (50/50) composite can be processed with SLS. In the SLS process, batch 2 showed improved melting behavior due to its smaller polymer particle size (approx. 35 µm vs. 50 µm) and its lower zero-shear melt viscosity (5800 Pa∙s vs. 17,900 Pa∙s). The better melting behavior of batch 2 led to SLS test specimens with lower porosity compared to batch 1. In consequence, the batch 2 specimens exhibited a larger biaxial bending strength (62 MPa) than the batch 1 specimens did (23 MPa). We conclude that a tailored composite powder with optimized polymer particle size, filler particle size, and polymer molecular weight can increase the achievable mechanical strength of laser-sintered scaffolds.

Challenges on optimization of 3D-printed bone scaffolds

“…In addition to materials and structural optimization, the process parameters should be adjusted and optimized to manufacture scaffolds with desired attributes. Numerous studies investigated the effect of process parameters on different responses such as mechanical properties (strength, elongation, Young's modulus), surface roughness, resolution and dimensional accuracy, and printing quality in different techniques including SLA [221][222][223][224], SLS [225][226][227][228][229][230][231][232][233][234], EBM [235][236][237][238][239][240][241], LENS [242,243], SLM [39,[244][245][246][247][248][249][250], 2PP [251][252][253], FDM [254][255][256], MJ [257,258], AJP [259][260][261][262], and IJP [263]…”

Recent Advances in 3D Printing for Parenteral Applications

“…Similarly, powder composition and properties such as particle size and polymer molecular weight (MW) impact printability and drug release behavior of SLS printed constructs [ 52 ]. Finer powder results in structures exhibiting enhanced green strength, smoother surface, quicker drug release, and reduced porosity, as well as an overall improvement in mechanical properties [ 53 – 55 ]. Laser properties ( e.g.…”

Recent Progress on 3D‐Printed Polylactic Acid and Its Applications in Bone Repair

“…[107] To solve the disadvantages of mechanical grinding, e.g., PLA is difficult to grind due to inelastic deformation at a small particle size [122] and particles obtained by grinding are generally irregularly shaped, [123] various grinding methods are further improved. Centrifugal grinding, [124,125] rotary grinding or using mortar, [126,127] ball milling, [15] etc., has been used extensively to prepare PLA powder.…”

“…His research interests are in the field of 3D-printing technology and 3D-printed PLA. Technology FDM [13,14] SLS/SLM [15][16][17] SLA [14] 3DP [18][19][20] EBM [21][22][23] Starting material status Moreover, companies such as Biomet (USA), [53] Takiron (Japan), [54] Zimmer (USA), and Sysorb (Switzerland) had successfully made commercial PLA-based medical devices. The traditional method of manufacturing PLA-based orthopedic equipments/scaffolds is extrusion, injection molding, stretch blow molding, film casting, thermoforming, foaming, fiber spinning, and electrospinning.…”