PLA (Polylactic acid) is a printing material retrieved from such natural materials like potatoes and corn. It is easy to, therefore, assume it is safe considering its origins from things we consume. This assumption formed the basis of a study by scientists from James Madison University. PLA was tested under various temperatures and durations using standard ingredients found in food.
The results are detailed in the 1995 publication of the Food and Chemical Toxicology Journal. The findings revealed that PLA is generally regarded as safe when used with food. PLA can, however, get contaminated by a printer’s hot ends. PLA is quite popular in the 3D printing field, mostly because it is acquired from consumable goods. The material is not spared from the unfavorable facts concerning food-safe 3D printing.
What is Food Safe?
Food grade describes a material that is allowed to come into contact with food or is fit for human consumption. Food safe on the other hand describes a food grade substance that has fulfilled all the requirements as guided by the intended function and it will not be harmful to humans.
Food safety and food grading relate to a specific method to consume parts called migration. Tiny particles ranging from a few hundred nanometers to several nanometers may be transferred every time various materials interact. In 3D printing, this migration begins between the parts of the printer and the printed object and then to the food. Migration levels are low on occasional interactions, so food safety commonly concerns things that are in continuous contact with food, including plates, straws, containers, and food molds.
Testing institutions are guided by government-imposed risk accommodations and approved substances. For the EU, for example, these adherents are laid out in 10/2011. In the US, the guidelines are detailed by the FDA CFR 21. You can look for these denotations in different labels. A material can, however, be “compliant with” and not be explicitly recognized by the institutions.
An EU or FDA-approved material does not only relate to the raw polymer but any additives as well. These may have such elements as flame retardants, carbon alloys, anti-static, plasticizers, thickeners, dyes, and UV-stabilizers.
Is PLA Food-Safe?
What makes a material food-safe? How to determine if a material is good for holding food and will not contaminate it? Let’s see what are the main characteristics of food-safe materials and see if PLA is actually food-safe:
– Toxic Substances from Printing
Most 3D printing models are fitted with hot ends containing dangerous chemicals. The chemicals are likely to seep into your PLA. Pruza Nozzle ranks as the safest option since it is made with stainless steel.
A 2015 study by the Illinois Institute of Technology involved desktop FDM models using PLA and ABS plastic. The printers were found to emit high amounts of ultrafine particles. The particles commonly lie on the printer’s surface, and excessive consumption of them can trigger severe health effects. ABS may be the worst offender of the two, but there are risks associated with PLA as well.
– Chemicals in the Filaments
Some manufacturers include additional additives in PLA for strength or color, which may make the material unsafe to consume. You may want to consider “virgin” or “natural” PLA for safety. You can check the manufacturer’s material safety data sheet to identify the chemical properties and whether it is designated as food-safe.
– Bacteria Build Up
All 3D printed items have tiny cracks and spaces that offer a breeding ground for bacteria and germs. PLA-printed parts are not exempted from this structure. Debris gathers in the pores, and because PLA is not dishwasher safe, the dirt cannot be cleaned out entirely. If you intend to print a utensil for disposable use, you can safely use PLA materials. It may not be safe to create items that will be used multiple times.
– Brass Nozzles may Have Lead
3D printers are not fitted with the same type of nozzles as they are made from brass, steel, or aluminum. One that is made from brass can contain lead, and lead contamination has been linked to serious health outcomes. You can check the extruder on your printer to determine its safety.
How to Ensure Food Safety?
PLA materials are generally safe on their own but can get contaminated during 3D printing. Food-grade printing can be done by:
– Purchase a Food-Safe Filament
Food safe PLA filaments are a recent development in the market, and they offer safer options for 3D printing. The earliest of these forms was unveiled by KeyTech, which provided similar resistance to impact and heat like ABS. The filament is incredibly flexible and resists damage. Other filaments regarded as food safe include HDglass from FormFutura and PP Plastic from German RepRap.
If you want to know if the filament you have purchased is food safe, consult the Material Safety Data Sheet (MSDS) accompanying the purchase. It will outline the chemical properties of the product and specify if it is food safe or FDA approved. The packaging will additionally reveal if the firm has gone through the procedure of being food-grade certified.
– Washing with Warm Water and Soap
Your 3D printed items can be washed. However, in place of using a dishwasher, use a mild anti-germ detergent and lukewarm water immediately after use. This action will minimize the risk of a melted risk as well as remove any surface bacteria.
– Get an Extruder that is Food Safe
Contamination can originate from the extruder, and you can opt to get one made of stainless steel to minimize this risk. This precaution will favor those who intend to print a lot of items for the kitchen since it may seem extreme for making only a handful of utensils. A food safe extruder will also make you less worried about contamination.
– Minimize Food Contact Time
Another consideration is the intended use for the objects being printed. Things like cookie cutters and knives are not in contact with food for very long, so it is safe to use non-food grade PLA. If you are printing cups or plates, however, you may need a food safe filament because food stays in the container for a longer time.
– Purchase a Food-Safe Sealant
Sealing a printed item with a sealant that is food safe will cover the pores that can collect bacteria and dirt. For PLA, it is best to buy Polyurethane found in a home improvement store. You can also avoid contact between your printed item and raw eggs and meat because they are more vulnerable to harmful bacterial growth.
Food Safe 3D Printing Technology
So, what 3D printing technologies can you use to print food-safe objects? Here are the technologies available:
– Stereolithography SLA
Printers that use SLA technology leverage on the photopolymerization process, where liquid resin is hardened into plastic via a laser. The resulting parts have defined details, smooth surfaces, and incredible accuracy. Resin is, however, not food safe. Materials may move from SLA components making the printed item un-safe by default. The smooth surface of the SLA objects makes it easier to use sealants to cover any cracks. Coatings are not foolproof since they may interact with the printer’s resin or degrade to expose the more vulnerable section of the material. You can use an SLA printer to produce custom molds as you will get detailed parts without the SLA prints coming into contact with food. The printers are ideal for creating mold negatives, that can be vacuumed to result in food-grade plastic.
– Fused Deposition Modeling (FDM)
FDM (Fused Deposition Modeling) is another 3D printing technology that prints objects by melting and releasing thermoplastic filament, which a nozzle deposits in layers on the build platform. The material is extruded in a circular cross-section manner which leaves narrow spaces in between layers where the depth is proportionate to layer height. This height should be the lowest possible for food-grade items. The primary concern with FDM technology is preventing the buildup of bacteria. For long term food-safety, the print needs to be produced with a smooth surface. Chemical smoothing using solvents like acetone or d-Limonene smoothens the surface, but an additional coating is required.
– Selective Laser Sintering (SLS)
SLS is a process that makes use of a very powerful laser to fuse tiny particles of polymer powder. Nylon ranks as the most common sintering material because of its excellent mechanical attributes. Some SLS powders are recognized as food safe, although the particles on the surface of print objects might not fuse entirely, resulting in objects that are porous and do not handle mold growth and moisture. It is also recommended to seal SLS components with food safe coatings. SLS parts are commonly dyed, and the dye may seep into the object, making it unsafe.
When it comes to 3D printing, everything is printable. You can manufacture impressive and custom-made kitchen utensils in your house using similar technology used to print technical parts for airplanes. If you intend for the products to handle food, it should be safe and devoid of the risk of food poisoning.
Growth of bacteria is among the concerns of 3D printing, which can be avoided by smooth materials. The aim is to prevent food chunks from getting stuck in the layers of your object or in crevices. 3D printing involves a combination of chemical processes, both in the hot end and in the PLA filament.
Source for a food-safe PLA filament and an extruder to limit exposure to dangerous chemicals. These precautions are especially necessary for items that will be in constant contact with food like coffee cups. Food-safe sealants will further make the printed object smooth and discourage the growth of bacteria.