Structure-Property-Performance Relationships in Thermoplastic Polyurethane: Influence of Infill Density and Surface...

Area of Science:

• Materials Science
• Polymer Engineering
• Additive Manufacturing

Background:

• Thermoplastic polyurethanes (TPUs) are versatile polymers used in additive manufacturing.
• Fused Filament Fabrication (FFF) allows for complex geometries and tailored material properties.
• Understanding structure-property-performance (SPP) relationships is crucial for optimizing TPU applications.

Purpose of the Study:

• To investigate the SPP relationships of two distinct TPUs (FILAFLEX FOAMY 70A and SMARTFIL® FLEX 98A) manufactured via FFF.
• To analyze the tribological and surface characteristics of TPUs with varying gyroid infill densities and Archimedean surface textures.
• To determine how infill density and surface features influence the performance and wear behavior of these TPUs.

Main Methods:

• Fabrication of TPU disc specimens using FFF with controlled gyroid infill densities (10-100%) and Archimedean surface textures.
• Tribological analysis using Ball-on-Disc tests to determine the coefficient of friction (μ).
• Surface characterization via profilometry and optical microscopy to assess roughness and morphology.

Main Results:

• SMARTFIL® FLEX 98A showed a significant decrease in μ from 1.174 (10% infill) to 0.371 (100% infill) due to enhanced structural stability.
• FILAFLEX FOAMY 70A maintained a stable but higher μ (0.585-0.729) across densities, attributed to its foamed structure and bulk yielding.
• SMARTFIL® FLEX 98A exhibited higher surface roughness, while FILAFLEX FOAMY 70A had consistent roughness; both TPUs demonstrated resistance to abrasive wear on steel counterparts.

Conclusions:

• Distinct SPP relationships were identified for the two TPUs, suggesting tailored applications based on their tribological and surface properties.
• SMARTFIL® FLEX 98A is suitable for energy-absorbing, deformable components, whereas FILAFLEX FOAMY 70A is ideal for applications needing stable surface finish and low adhesive wear.
• The study advances the design of functionally graded TPU materials by demonstrating the impact of controlled infill and surface feature tuning.