Leapfrog 3D Printers together with Verbatim have succeeded printing polypropylene.

3D Printing Polypropylene
The plastic Polypropylene (PP) is one of the most used plastics in the world with a wide range of industrial and consumer applications. Printing this material in 3D has always been near impossible, until the Leapfrog Bolt.

Vision of Leapfrog 3D Printers is to take more advantage of Fused Filament Fabrication. The freedom it offers within printing materials opens more possibilities for the 3D printing industry. PP has advantages over standard filaments like PLA so 3D printing PP can be the next big thing.

PP Properties

• Polypropylene is certainly the most requested type of plastics in the industry. It has impressive mechanical properties, combined with high chemical resistances.
• PP has a larger tendency to bend compared to PLA and it can resist deformation better under a load. 
• It is lighter and gives a better strength-to-weight ratio. 
• One of the main properties appreciated about polypropylene is the resistance presented towards chemicals such as acids, alkalis and organic solvents.

Common Uses of Polypropylene

• The chemical resistances of PP allow a wide use of this material. For instance, the medical industry uses polypropylene containers, since it is able to store substances without contaminating them.
• Additionally, the automotive industry uses polypropylene for creating car bumpers that result in a cost efficient and resistant part, able to withstand bumps and bruises without breaking. This makes it also extremely applicable for toys.
• Being FDM approved makes plastic polypropylene ideal for the packaging industry. The use of PP as a bottle for milk results in a cheap and durable package. However, the mechanical resistance of Polypropylene is well exemplified by the plastic lids for different candy recipients (i.e., Tic Tac). Its flexural modus prevents the material to break while opening and closing it through repeatedly bending.
• Without realizing, PP is one of the big influencers of our daily household. This creates a waste stream which can be recycled to Polypropylene filament and re-put to use.

Why 3D Printing PP is Difficult
In addition to the benefits and features of PP above mentioned, the material has its benefits over PLA. So, why has it not yet landed in 3D printing?

• One of the reasons is mainly because Polypropylene filament proved to be very difficult to print. 
• Most 3D printers find it hard to control the results of PP prints because of the heavy warping that takes place during the printing process. 
• Thus, it is believed that the structure of the material plays an important role on why the conventional tricks to prevent warping had not worked before. 
• PLA and ABS are amorphous polymers, where Polypropylene is semi-crystalline. This means that the material cools and solidifies differently, resulting in much more stress within the material, thus, warping.

3D Printing with PP FilamentNevertheless, Leapfrog 3D Printers together with Verbatim have succeeded printing polypropylene on the Bolt. Verbatim filament provided the right attributes to demonstrate how the Bolt can print PP, providing a perfect result with this demanding type of plastic.

How to Print PP Filament
Printing polypropylene was one of the greater challenges to the Leapfrog Bolt printer. Also, after completing this task with full success, it is confirmed that the Bolt is suitable for any type of material, since trials have been made with Flex, Nylon and Polycarbonate, all resulting in successful prints.

For this test, Leapfrog has printed two Benchy boats: one using regular blue PLA and the other in Verbatim transparent PP filament developed by the Mitsubishi Chemical Holdings Group. Verbatim has advised to print PP on 220°C, but it was found, after testing, that printing at 170°C provided better results on the Bolt. Because of the closed chamber and heated bed, the Bolt can easily keep track on the temperature of the print, overcoming the challenges with the structure of the material and preventing warping of the print. Combined with the Direct Drive, the Bolt provides optimum control for printing PP filament. Leapfrog has tested 3 times, and the third test gave best results.

Resisting Chemicals with Polypropylene
To put both prints and materials to the test, we came up with the following setup. Both Benchy boats were put into a liquid until one sinks. In order to make it more interesting, we have used Dioxolane instead of water. Dioxolane is a chemical solvent often used in coatings, foils/films, paint coatings, paint removers, film coating removers and general cleaning solvents.

After 2 hours, the first signs of decay of the PLA boat began to appear, while the PP boat was still going strong. It took a bit longer to get the PLA boat to dissolve completely, but the blue color in the Dioxolane clearly showed where the blue PLA Benchy did go.

The Potential of PP filament
Is PP going to be the next big thing in 3D printing? At the moment PLA still holds the throne. We think that it is never good to let one material stay on top for so long.

The combination of Verbatim PP filament and the Leapfrog Bolt proved to be a successful partnership. This pair shows that the bar of FFF 3D printing is still being set higher every day. PLA has its pros and cons, and the development of this filament makes PLA grow as a material as well. However, Polypropylene enables new possibilities, which is the heart of the 3D printing. Better hinging capabilities, better chemical resistances and a good surface finish; these are the things that will appeal to a lot for unique users and specialized industries. And right now, its unique experience with the Leapfrog Bolt 3D printer feels right at home at these niches.

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