Polypropylene (PP) is one of the most frequently used plastics in the world with a wide range of industrial and consumer applications. It is also one of the most challenging materials to 3D print with. However, once mastered, it yields a lot of benefits: PP has advantages over standard filaments like PLA, including its chemical resistance and relative flexibility. It makes this filament
COMMON USES OF POLYPROPYLENE
The chemical resistance of PP contributes to a wide range of applications for this material. For instance, the medical industry uses polypropylene containers, since they are able to store substances without contaminating them.
The automotive industry benefits from polypropylene in creating car bumpers. Usage of PP results in cost-efficient and resistant parts, able to withstand bumps and bruises without breaking. Additionally, this makes it extremely applicable to manufacture toys.
It is also FDA approved, thus suitable for the packaging industry. Packages such as bottles of milk made with PP are cheap and durable. 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 from breakage while opening and closing it through repeatedly bending.
Switching to Polypropylene is also beneficial for the environment. It produces almost no waste and the parts from PP can be recycled multiple times.
Polypropylene is one of the most appealing types of plastic in the industry. It has impressive properties, including but not limited to:
- Chemical resistance
Polypropylene is well-known for its ability to survive in such chemical conditions which other plastics cannot stand. It can resist acetone, chloride, boric acid, nickel carbonate, nickel sulfamate, Hydrochloric acid, and other chemicals like acids, alkalis, and organic solvents. It makes the material suitable for applications that require interaction with chemicals.
- More prone to bending & better resist deformation under load than PLA
PP has a larger tendency to bend compared to PLA and it can better resist deformation under load. This allows Polypropylene to be used in conditions that assume additional bending (e.g., plastic lid for Tic Tak).
Polypropylene has the lowest density out of all commonly used in manufacturing plastics, which makes it very light. Thus, more parts could be produced out from the same amount of PP compared to, for example, PLA.
- Better strength to weight ratio
Although Polypropylene has lower weight, it is prone to bending and can withstand higher loads. This combination results in the material having a better strength to weight ratio compared to its counterparts.
- Low melting point
Despite the abovementioned pros of the polypropylene, it still has some pitfalls. The biggest of them refers to its heat resistance. Polypropylene has a low melting point (160 °C) and does not work well in an environment that requires high heat resistance.
WHY IS IT DIFFICULT TO 3D PRINT POLYPROPYLENE?
Why Polypropylene has 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. It seems that the structure of the material plays an important role in why the conventional tricks to prevent warping had not worked before.
PLA and ABS are amorphous polymers, whereas Polypropylene is semi-crystalline. This means that the material cools and solidifies differently, resulting in much more stress within the material, which results in warping. Nevertheless, with some knowledge and experience it is possible to master 3D printing with Polypropylene.
HOW TO 3D PRINT PP FILAMENT
There are several important points to consider while printing with polypropylene:
- Stable printing temperature
Polypropylene has a tendency to warp, thus it requires a stable temperature of the printing chamber (highly recommended to have an enclosed chamber) combined with a heated bed and high extruding temperature. For most plastics (we recommend to use Verbatim), the hot ends could have a temperature of 220°C and the bed temperature of 85°
- Consider additional adhesion
As a general rule, polypropylene sticks well to polypropylene. A generic sheet made of polypropylene on top of the printing plate allows a polypropylene print to stick well and prevents warping. A double-sided tape (normally also of polypropylene) could also work as a solution.
- Use printing settings from the manufacturer
Normally, every manufacturer of 3D printer tests all materials their machines can print with and provides their users with the printing settings. If you do not have too much experience with 3D printing, it would be easier to choose the settings provided by the manufacturer. For example, using this link you can download our setting for Polypropylene that we recommend with the Bolt Pro.
A hint: when it comes to 3D printing with Polypropylene, it is important to consider the high quality of your FDM 3D printer and filament you are using. Here at Leapfrog we are working with Verbatim Polypropylene, which combined with our settings gives us great
RESISTING CHEMICALS WITH POLYPROPYLENE
We decided to run a test on Verbatim polypropylene that we use at Leapfrog 3D printers. For this test, we have printed with the Bolt Pro two Benchy boats: one using regular blue PLA and the other one using Verbatim transparent PP filament developed by the Mitsubishi Chemical Holdings Group. Because of the closed chamber and heated bed, the Bolt Pro can easily keep track of 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 the PP filament. We have tested 3 times, and the third test gave the best results.
After printing, both Benchy boats were put into a liquid until one sink. 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. However, we think that it is never good to let one material stay on top for so long.
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 3D printing. Better hinging capabilities, better chemical resistance, and a good surface finish; these are the things that will appeal to a lot for unique users and specialized industries. And right now, our unique experience with the Leapfrog Bolt Pro 3D printer feels right at home in these niches.
Want to see PP prints of the Bolt Pro for yourself? Request a sample on our sample page.