Researchers at the Slovak Academy of Sciences and the Slovak University of Technology have developed a new set of low-cost hybrid materials for FFF 3D printing. By using expanded graphite, carbon fiber, and a combination of both to enhance the virgin PETG and recycled PETG filaments, the team improved the mechanical and thermal properties of the pure PETG matrix material.
Use expanded graphite, carbon fiber, or a hybrid PETG reinforced by both for 3D printing
Fillers are often added to thermoplastic filaments to improve strength, thermal properties, electrical conductivity and even appearance. A large part of materials science research is simply testing additives, testing composite materials, and repeating this process until the desired performance is achieved. Especially PETG, which is famous for impact resistance, flexibility and excellent chemical resistance.
In order to develop a lower-cost PETG hybrid material without compromising any original properties, the researchers first obtained samples of virgin PETG, recycled PETG, expanded graphite, and carbon fiber. They produced a total of 23 samples of composite materials, 19 of which were made of virgin PETG, and the other 4 were made of recycled PETG. Two samples in each group did not contain fillers and served as a reference.
The filler-reinforced samples use various combinations of graphite and carbon fibers, with a total weight ratio of up to 10% (usually at least 90% of PETG is retained). Use material samples, test the parts with a Quadron 1001 FFF machine 3D printing, and then use a universal testing machine to determine the Young's modulus, tensile stress at yield, tensile stress at break and elongation at break of each sample , And other thermodynamic properties.
The team found that with the exception of one sample, each composite combination they used was suitable for the 3D printing process. Tests have shown that their newly developed filaments are "very strong" and the layers are firmly bonded. The addition of expanded graphite increases the material density and brings some enhancement of mechanical properties. They also found that the addition of carbon fiber reduced the density of the parts while significantly reducing the coefficient of thermal expansion of the material. By choosing cheaper recycled PETG instead of virgin PETG, these researchers were able to achieve their goal of creating a lower-cost, high-strength composite material,
Native PETG with expanded graphite
Although the recovered filaments are economical, they often cause people to worry about the mechanical properties of the produced parts. To quantify this problem, researchers at the Mediterranean University of Greece studied the changes in the mechanical properties of ABS filaments with the number of cycles. They found that until the fifth stage of recycling, the mechanical properties of ABS improved by about 30%, and then degraded. In addition, the US Army has developed a new polymer filament for low-cost FFF 3D printers. The combination of the core material of star polycarbonate and the outer layer of ABS gives the test filament high strength properties.