As a promising additive manufacturing technology for the next generation, Fused Deposition Modeling (FDM) is applied in all areas of manufacturing from customized devices to electrodes for energy storage, and biomedical scaffolds. FDM process is highly non-equilibrated and the thermal retention which causes the insufficient filament/filament interfacial fusion is difficult to predict. In particular, this factor is more pronounced in partially crystalline polymers, such as PLA, where interdiffusion becomes difficult when the temperature falls below the melting point, even if they are still above the glass transition. Improper filament fusion is the primary cause of internal defects leading to poor mechanical properties, and thermal or conduction properties. Post printing treatments have not been optimal due to increased cost or structural deformation, while the lower Mw components may not be readily available nor provide sufficient entanglement thickness. Here we show that fusion can be achieved by the addition of one percent or less, of a second polymer, having low Tg, low surface tension, and high molecular weight. Even if this polymer is not miscible with the host, the low surface tension will allow surface segregation, while the low Tg enables high mobility, and the high Mw enables entanglements. Using micro-CT, in conjunction with contact angle goniometry, and Dynamic Secondary Ion Mass Spectrometry (DSIMS), we show that this method applies to PLA. The addition of 1% either HDPE or iPP, increases crystallinity, improves toughness, and tensile strength while reducing void formation (fig. 1).

Self healing filament/filament interfaces via polymer blending during fused deposition modeling

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.