Novel 3D printing filament composite using diatomaceous earth and polylactic acid for materials properties and cost improvement

Additive manufacturing, commonly known as 3D printing, has grown in popularity due to its precision and efficiency in producing complex geometries. It is a novel industrial growth area and finds applications in numerous sectors, including medical research, aerospace and defense. 3D printing technology is mostly used in manufacturing final and specific parts where precision, assembly specifications, mass customization and waste minimization are important. In 3D printing, the printing filaments play a role similar to that of ink jet printing. This means that the cost of thermoplastic filaments is a key revenues source for 3D printing industry.

Although traditional filament materials have been predominantly thermoplastics, photopolymers and metal powders, the future direction will include ceramics, biomaterials, and metal binders, among others. Depending on applications, there are materials used in the manufacturing of 3D printing filaments. Among the materials used to manufacture 3D printing filaments, biodegradable PLA has attracted research attention despite its high prices. PLA usage is characterized by moisture resistance and VOC emissions during 3D printing processes. Thus, recent research has focused on addressing the cost issue and introducing a new value-added feature by developing composite filament alternatives.

Diatomaceous earth has been identified as a suitable material for manufacturing 3D printing filament composites. It is a naturally occurring fossilized diatoms that have been traditionally used in paper-based materials and as a stabilization material for dynamite. Despite the potential application of diatomaceous earth, there is relatively limited research on its application to produce PLA-based 3D printing composite materials.

Herein, Dr. Salonika Aggarwal, Dr. Shelly Johnson, Dr. Daniel Saloni and led by Professor Marko Hakovirta from North Carolina State University investigated the application of diatomaceous earth as a potential component for polylactic acid-based 3D printing composite materials. The diatomaceous earth was used as an additive to the filament material to develop a composite with the benefits of minimizing the usage of PLA and the associated costs. Additionally, its mechanical properties, alongside other potential benefits, were examined and discussed. The research work is currently published in the research journal, Composites Part B.

The research team showed that through minor degradation of the mechanical properties of the printed materials, about 10 wt% of the total PLA consumption could be reduced and be replaced by diatomaceous earth. The resulting PLA-DE composite materials exhibited no significant degradation in the material property after 3D printing. Instead, it had the benefits of reducing the cost of producing the filaments by 5 – 10%, high water absorption ability and enhanced moisture resistance that played a key role in slowing down the decomposition process of the filament material. The authors also noted that diatomaceous earth acted as nucleation agents in the PLA matrix, thus improving crystallization.

In summary, the researchers are the first to successfully demonstrate the potential application of diatomaceous earth as a filler for PLA to produce high-performance composite materials for 3D printing filaments. Compared to using pure PLA filaments, this approach offers cost reduction opportunities during the 3D printing of the filaments. Moreover, it exhibits potential applications in numerous fields, such as biomedical applications, because the approach eliminates the detrimental sterilization effects on the performance of PLA materials. In a statement to Advances in Engineering, Professor Marko Hakovirta said their study will advance the application of diatomaceous earth in producing PLA-based 3D printing filaments composites and their associated applications.