Improvement of Interlayer Adhesion and Heat Resistance of Biodegradable Ternary Blend Composite 3D Printing

Abstract

Poly(lactic acid) (PLA) filaments have been the most used in fused deposition modeling (FDM) 3D printing. The filaments, based on PLA, are continuing to be developed to overcome brittleness, low heat resistance, and obtain superior mechanical performance in 3D printing. From our previous study, the binary blend composites from PLA and poly(butylene adipate-co-terephthalate) (PBAT) with nano talc (PLA/PBAT/nano talc) at 70/30/10 showed an improvement in toughness and printability in FDM 3D printing. Nevertheless, interlayer adhesion, anisotropic characteristics, and heat resistance have been promoted for further application in FDM 3D printing. In this study, binary and ternary blend composites from PLA/PBAT and poly(butylene succinate) (PBS) with nano talc were prepared at a ratio of PLA 70 wt. % and blending with PBAT or PBS at 30 wt. % and nano talc at 10 wt. %. The materials were compounded via a twin-screw extruder and applied to the filament using a capillary rheometer. PLA/PBAT/PBS/nano talc blend composites were printed using FDM 3D printing. Thermal analysis, viscosity, interlayer adhesion, mechanical properties, and dimensional accuracy of binary and ternary blend composite 3D prints were investigated. The incorporation of of PBS-enhanced crystallinity of the blend composite 3D prints resulted in an improvement to mechanical properties, heat resistance, and anisotropic characteristics. Flexibility of the blend composites was obtained by presentation of PBAT. It should be noted that the core-shell morphology of the ternary blend influenced the reduction of volume shrinkage, which obtained good surface roughness and dimensional accuracy in the ternary blend composite 3D printing.

Keywords: FDM 3D printing; anisotropic; biodegradable polymers; composites; heat resistance; interlayer adhesion.

Figure 1

3D printing specimens: (a) horizontal dumbbell; (b) horizontal bar; (c) vertical dumbbell; (d) vertical bar.

Figure 2

DSC thermograms of PLA/PBAT/PBS nano talc composite 3D prints: (a) First heating cycle; (b) Cooling cycle; (c) Second heating cycle.

Figure 3

Dynamic mechanical properties of PLA/PBAT/PBS/nano talc composite 3D prints: (a) Storage modulus; (b) Tan δ.

Figure 4

Anisotropic ratio in tensile and flexural strength of PLA/PBAT/PBS/nano talc composite 3D prints.

Figure 5

Complex viscosity (η^∗) of neat polymers and PLA/PBAT/PBS/nano talc composites measured at 210 °C: (a) Full image; (b) Enlarged image of (a).

Figure 6

SEM images of the cross-sectional surface of PLA/PBAT/PBS/nano talc composite 3D prints: (a–c), SEM images from a horizontal dumbbell; (d–f), SEM images from a vertical dumbbell; (examples of void areas were identified by yellow arrows).

Figure 7

SEM images from cryogenic fractured surface of PLA/PBAT/PBS/nano talc: (a) 70/30/0/10; (b) 70/0/30/10; (c) 70/10/20/10.

Figure 8

SEM images from the fractured surface of compression-molding binary and ternary blends PLA/PBAT/PBS without nano talc: (a) PLA70/PBAT30; (b) PLA70/PBS30; (c) PLA70/PBAT10/PBS20 (the SEM images in the top row and the bottom row are the fractured surface before and after etching PBAT, respectively).

Figure 9

(a) Sample observation direction of surface roughness and examples of 3D surface roughness profiles: (b) 3D surface roughness profile from width side; (c) 3D surface roughness profile from thickness side.

Figure 10

(a) Schematic of the vertical 3D printing line; (b) SEM image from the thickness side of 70/0/30/10 3D printing.

Figure 11

Dimensional deviation of PLA/PBAT/PBS/nano talc composites 3D prints: (a) Width deviation; (b) Length deviation; (c) Thickness deviation.

Figure 12

The distortion of 3D printing bars: (a) Horizontal direction; (b) Vertical direction; and (c) 3D printing models of PLA/PBAT/PBS/nano talc composites.