Reinforcing Plastic Polymers With Cellulose And Other Natural Fibers

September 9, 2024 by Maya Posch 10 Comments

While plastics are very useful on their own, they can be much stronger when reinforced and mixed with a range of fibers. Not surprisingly, this includes the thermoplastic polymers which are commonly used with FDM 3D printing, such as polylactic acid (PLA) and polyamide (PA, also known as nylon). Although the most well-known fibers used for this purpose are probably glass fiber (GF) and carbon fiber (CF), these come with a range of issues, including their high abrasiveness when printing and potential carcinogenic properties in the case of carbon fiber.

So what other reinforcing fiber options are there? As it turns out, cellulose is one of these, along with basalt. The former has received a lot of attention currently, as the addition of cellulose and similar elements to thermopolymers such as PLA can create so-called biocomposites that create plastics without the brittleness of PLA, while also being made fully out of plant-based materials.

Regardless of the chosen composite, the goal is to enhance the properties of the base polymer matrix with the reinforcement material. Is cellulose the best material here?

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3D Printing In Custom PLA With A TPU Core

May 4, 2024 by Donald Papp 11 Comments

[Stefan] from CNC Kitchen explored an unusual approach to a multi-material print by making custom PLA filament with a TPU core to make it super-tough. TPU is a flexible filament whereas PLA is hard almost to the point of being brittle. The combo results in a filament with some unusual properties, inviting some thoughts about what else is possible.

Cross-section of 3D print using white PLA with a red TPU core.

[Stefan]’s video covers a few different filament experiments, but if you’d like to see the TPU-PLA composite you can skip ahead to 18:15. He first creates the composite filament by printing an oversized version on a 3D printer, then re-forming it by running it through a Recreator to resize it down to 1.75 mm.

We have seen this technique of printing custom filaments before, which is useful to create DIY multi-color filaments in small quantities right on a 3D printer’s print bed with no special equipment required. This is an effective method but results in filament with a hexagonal profile, which works but isn’t really ideal. By printing his custom composite at 4 mm diameter then resizing the filament down to 1.75 mm, [Stefan] was able to improve overall printability.

That being said, TPU and PLA have very different characteristics and don’t like to adhere to one another so the process was pretty fiddly. TPU-cored PLA might be troublesome and uncooperative to make, but it can be done with some patience and fairly simple equipment.

Despite the difficulties, test prints were pretty interesting. PLA toughness was roughly doubled and under magnification one can see a lattice of TPU strands throughout the prints which are unlike anything else. Check it out in the video, embedded below.

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