By Olivia Cahoon
Part 1 of 4
A variety of materials are used in the three-dimensional (3D) printing process including plastics, metals, and wood. The most popular forms of 3D printing materials include polymers, materials with long, repeating chains of molecules. Polymers may be flexible or rigid and are often used to describe plastics but also include natural polymers like rubber and wood.
Joanna Marguier, 3D printing R&D senior manager, Clariant, says today’s 3D printing materials are primarily made with polymers due to their properties. She offers, “for example, flame retardants can be added to polyamides to achieve the required properties for use in electrical and electronics, transportation, and other markets.”
Plastic is a popular choice for 3D printing because it offers translucency, reflectiveness, and a variety of colors. Numerous plastic 3D materials exist that range in cost, extrusion temperature, and use.
Acrylonitrile butadiene styrene (ABS) is a low-cost material for producing durable parts that withstand high temperatures. It’s one of the most popular 3D printing materials and is used in a variety of applications for its strength and range of colors. It features high impact and heat resistance and is often used with in-home printers.
Slightly flexible and easily extruded, the print temperatures range from 210 to 250 degrees Celsius. It’s used in 3D printed applications like automotive hardware, cases, electronic housing, fidget spinners, helmets, kitchen appliances, Legos, movable parts, musical instruments, pipes, and toys.
ABS is best stored in dry environments and produces a slight odor during printing. It requires a heated bed or heated chamber and is susceptible to shrinking during cooling.
Polyethylene terephthalate (PET) is a colorless and clear plastic material. When exposed to heat or cold, the material changes its transparency. If cooled down slowly after printing, it maintains a crystalline structure.
PET materials are ideal for packaging applications because of their vapor barrier and strength. Applications that require flexibility or impact resistance like mechanical parts, phone cases, and snap-fit components benefit from PET.
Print temperatures range from 220 to 25 degrees Celsius. It’s important to note that the material also absorbs water from the air and requires proper storage. It may also produce thin hairs on the 3D printed object’s surface from stringing.
PET includes different versions like PETG—a glycol modified version of PET. PETG is a clear thermoplastic with the capability to thermoform and mold after the 3D object is printed or polished with flames. It’s often used to manufacture water bottles for its smooth surface finish and odorless printing.
Polylactic acid (PLA) is a biodegradable thermoplastic used in desktop 3D printing. It is comprised of renewable resources like cornstarch and sugar cane. An environmentally friendly option with low-toxicity features, no toxins are produced during printing. The plastic also doesn’t contract during cooling or require a heated bed.
Because it can degrade into lactic acid, PLA is used in medical procedures for surgical implants including implanted pins, rods, or mesh, which break down in the body within six months to two years. It’s also used for cosplay props, decorative parts, disposable tableware, food packaging, hygiene products, and test items.
PLA features a low heat resistance and may also ooze during printing.
Polyvinyl alcohol (PVA) is a soft, water soluble plastic with non-toxic and biodegradable features. It’s often used as a support structure material for complex shapes, partially enclosed cavities, or models with overhangs. PVA support structures are easily removed and dissolved with warm water.
It is also used for independent 3D printed applications including packaging films, paper adhesives, prototypes, and a thickener for hygiene products.
However, PVA can be costly compared to other 3D printing materials. It’s also challenging to source and use. Because it dissolves in water, PVA shouldn’t be exposed to weather or moisture environments.
It should also be kept away from high temperatures and heated elements due to its low melting point of 190 degrees Celsius. If exposed to high temperatures, PVA carbonizes and clogs printer nozzles.
Polyamide (nylon) is a synthetic material used in industrial applications for its strength, durability, flexibility, and light weight. A cost-effective plastic, it is found in mechanical parts and functional parts including bearings, cable ties, containers, consumer products, gears, screws, and tools.
Nylon can be re-melted and reused without losing its bonding properties. However, it does have a high melting temperature of at least 240 degrees Celsius and contains materials like PEEK and PTFE. When heated, nylon breaks down and emits toxic fumes.
It’s also sensitive to moisture and absorbs over ten percent of its weight in 24 hours. Printing nylon with absorbed moisture may lead to print quality issues. It should be stored in a dry, sealed container with moisture remover or silica gel packets.
High impact polystyrene (HIPS) is a lightweight, biodegradable 3D printing material. It combines the hardness of polystyrene with the elasticity of rubber to produce a high-impact thermoplastic. Like PVA, HIPS acts as a support structure that dissolves in d-Limonene. It’s often used with ABS 3D printed applications and includes similar printing properties but with a higher impact strength.
Besides acting as a support structure, HIPS is also used for food packaging, prototypes, scale models, and wearable objects. The material can be glued, painted, primed, or sanded and is available in a variety of colors.
3D printing materials should be selected based on the product’s end use for toxicity, flexibility, and strength. While these aren’t all of the available plastic 3D materials, they are some of the most common.
Part two of this series takes a look at newer materials for 3D printing like metal, wood, and sandstone.
May2018, Industrial Print Magazine