PLA

PLA

Polylactic acid (PLA) is a bio-degradable polymer that can be produced from lactic acid, which can be fermented from crops such as maize. This makes it an ideal candidate for use in certain energy rich, cash poor areas of the world.

It is harder then PTFE and melts at a lower temperature (around 170°C to 210°C), so is potentially a very useful material. It does exhibit higher friction than PTFE however.

For more details, see the Wikipedia entry on Polylactic acid

Availability

New Zealand

We were fortunate to be supplied a 10kg bag of PLA 4042D by Convex Plastics Ltd. in New Zealand for research purposes.

USA

Several resellers have popped up and are supplying two different varieties of PLA

Ultimachine - http://ultimachine.com/ Green, Black, Natural 4042D in 5lb coils

Makerbot - http://store.makerbot.com/ Natural 4032D in 5 coils.

Makergear - http://makergear.com/ Green, Black, Natural 4032D and 4042D in 5 lb coils and lb packs

Synthesis

A crude form of PLA can be produced by simply heating powdered lactic acid with powdered stannous chloride - commonly used in pottery glazes - in a test tube. Extracting it from the test tube afterwards is left as an excercise for the diligent student.

See papers in footnote for further details.

Use So Far

Vik has been using the PLA filament in New Zealand made from the granules supplied by Convex. This was drawn into a 2.6mm diameter filament for us by Imagine Plastics Ltd. on their equipment used to make plastic welding rod and knitting needles.

Rod diameter is 2.6mm+-0.1mm . The plastic tends to absorb atmospheric water which can cause small bubbles on extrusion. It is slightly flexible and transparent. It will not degrade outside of a commercial composting pit. It has a density of 1.04

The standard yellow gear motor will not reliably feed the filament through a Mk 2 Extruder. A more powerful motor needs to be fitted to the gearbox.

Papers etc

• [[File:PLA-kim-23-2-6-98033.pdf: Synthesis, Characterization and in Vitro Degradation of Poly(DL-Lactide)/Poly(DL-Lactide-co-Glycolide) Films.|thumb]]

• [[File:PLA-v30 327 334.pdf: Synthesis and Characterization of Poly(L-lactide-co-ε-caprolactone) Copolymers: Effects of Stannous Octoate Initiator and Diethylene Glycol Coinitiator Concentrations|thumb]]

• [[File:PLA-DiscreteYttriumComplexesasLactidePolymerizationCatalysts.pdf: Discrete Yttrium(III) Complexes as Lactide Polymerization Catalysts|thumb]]

• Stereoselective Ring-Opening Polymerization of meso-Lactide: Synthesis of Syndiotactic Poly(lactic acid) [[, Page 2, Addendum|thumb]]

• Plastics from Renewable Materials A Royal Society of Chemistry educational document giving details of how to synthesise many polymers, including PLA.