Page 27 - eBook_Proceedings of the International Conference on Digital Manufacturing V1

Degradation Analysis of 3D Printed PLA in Simulated Body

Overall, the results suggest that while PLA degradation in SBF
causes only mild acidification, the geometry of the sample may
affect the extent and progression of such pH changes.

Nonetheless, the non-linear progression highlighted the
complex and time-dependent nature of PLA hydrolysis, where
early-stage degradation may not always produce a directly
proportional impact on the surrounding environment.

Correlation Between Geometry and Degradation Behaviour

While individual results from weight loss and pH measurements
provide insight into the degradation trends of PLA samples, a
comparative analysis reveals deeper correlations influenced by
geometric design. The interplay between mass loss and local pH
variation across different geometries suggests that degradation in
PLA is not governed by a single factor, but by a dynamic balance
between hydrolytic exposure, byproduct accumulation and spatial
confinement (Mndlovu, Kumar, du Toit & Choonara, 2024).

In general, faster degradation is expected to produce more
acidic byproducts such as lactic acid, leading to a more significant
change in the surrounding pH environment, as similarly observed
in our previous study on the degradation behaviour of PCL
materials (Ng et al., 2024). However, this theoretical relationship
was not fully reflected in the experimental results. For instance,
although the Dogbone sample consistently showed the greatest
weight loss, it did not correspond to the highest pH variation. In
contrast, the Cube sample exhibited the most significant shift in
pH despite a relatively moderate mass loss. This apparent
disconnect suggests that the degradation rate alone does not
dictate the pH response; instead, the sample geometry plays a
critical role in regulating the diffusion and accumulation of
degradation products (Mndlovu, Kumar, du Toit & Choonara,
2024).

Such behaviour may be explained by diffusion-limited
degradation, a phenomenon often observed in semi-crystalline
biodegradable polymers (Linde, Giron & Celina, 2022). In

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