The answer is: it depends on the type of plastic and the conditions of exposure. Some 3D printed plastics are more flammable than others, and some can even self-extinguish after a brief flame contact.
3D printing is a popular and versatile technology that can create various objects from plastic materials. However, one of the concerns that many users have is the flammability of 3D printed plastics. How safe are they in case of fire? What are the factors that affect their fire behavior? And what are the best practices to prevent or reduce the risk of fire hazards?
Flammability of 3D Printed Plastics
Flammability is the ability of a material to ignite and sustain combustion when exposed to a heat source. Flammability is influenced by several factors, such as the chemical composition, the physical structure, the oxygen availability, the ignition temperature, and the flame spread rate of the material.
Different types of 3D printed plastics have different flammability characteristics, depending on their chemical composition and the printing method. For example, PLA (polylactic acid) is a biodegradable and eco-friendly plastic that is widely used for 3D printing. However, PLA is also one of the most flammable 3D printed plastics, as it can ignite at temperatures above 270°C (518°F) and burn rapidly with a high flame spread rate.
On the other hand, some 3D printed plastics have flame-retardant properties, meaning that they can resist or delay combustion when exposed to a heat source. These plastics usually contain additives or fillers that reduce the flammability of the base material, such as halogens, phosphorus, nitrogen, or metal hydroxides. For example, ULTEM (polyetherimide) is a high-performance plastic that is used for 3D printing aerospace and automotive parts. ULTEM has excellent flame-retardant properties, as it can pass the UL-94 V-0 and FAR 25.853 flammability tests, which are the highest standards for self-extinguishing materials.
Flammability Tests for 3D Printed Plastics
Flammability tests are standardized methods to measure and compare the fire behavior of different materials. Flammability tests usually involve exposing a sample of the material to a controlled flame source and observing the ignition time, the burning time, the flame spread rate, the smoke generation, and the flaming drips of the material.
There are various flammability tests for 3D printed plastics, depending on the industry and the application. Some of the most common flammability tests are:
- UL-94: This is a test method developed by Underwriters Laboratories (UL) to evaluate the flammability of plastic materials. UL-94 has different classifications based on the orientation and the performance of the material sample when exposed to a vertical or a horizontal flame. UL-94 V-0 is the best rating, where the material self-extinguishes within 10 seconds without any flaming drips. UL-94 HB is the lowest rating, where the material burns slowly or self-extinguishes.
- FAR 25.853: This is a test method enforced by the Federal Aviation Administration (FAA) to evaluate the flammability of cabin and cargo materials for aircraft. FAR 25.853 involves exposing the material sample to a 60-second flame and measuring the burn length, the afterflame time, and the flaming drips of the material. The material passes the test if it self-extinguishes within 15 seconds after the flame, if the burn length is less than six inches, and if the flaming drips burn for less than three seconds.
- FMVSS 302: This is a test method enforced by the Federal Motor Vehicle Safety Standards (FMVSS) to evaluate the flammability of interior materials for vehicles. FMVSS 302 involves exposing the material sample to a horizontal flame and measuring the burn rate of the material. The material passes the test if the burn rate is less than four inches per minute.
Best Practices to Prevent or Reduce Fire Hazards
While some 3D printed plastics are more flammable than others, there are some best practices that can help prevent or reduce the risk of fire hazards when using 3D printing. Some of these best practices are:
- Choose the right plastic for your application. If you need a 3D printed plastic that is flame-retardant, opt for materials that have passed the relevant flammability tests, such as ULTEM, nylon, or ABS. Avoid using materials that are highly flammable, such as PLA, unless you add flame-retardant additives or coatings to them.
- Use a quality 3D printer and follow the manufacturer’s instructions. Make sure that your 3D printer is in good condition and that you use the recommended settings and parameters for your chosen plastic. Avoid overheating or overloading your 3D printer, as this can cause electrical or mechanical failures that can spark a fire.
- Keep your 3D printer away from flammable materials and sources of ignition. Place your 3D printer in a well-ventilated and fire-resistant area, away from curtains, paper, wood, or other combustible materials. Also, keep your 3D printer away from open flames, sparks, or hot surfaces that can ignite your 3D printed plastic.
- Monitor your 3D printing process and have a fire extinguisher nearby. Do not leave your 3D printer unattended while it is printing, as you may not notice any signs of fire or malfunction. Have a fire extinguisher that is suitable for plastic fires (such as a Class B or Class C extinguisher) nearby, in case of emergency.
Conclusion
3D printed plastics are not all the same when it comes to flammability. Some 3D printed plastics are more flammable than others, and some can even self-extinguish after a brief flame contact. The flammability of 3D printed plastics depends on the type of plastic and the conditions of exposure. Flammability tests are standardized methods to measure and compare the fire behavior of different 3D printed plastics. By choosing the right plastic for your application, using a quality 3D printer, and following some best practices, you can prevent or reduce the risk of fire hazards when using 3D printing.