3D Printing Materials Guide: Plastics
A plastic is a material made of synthetic or semi-synthetic compounds that has the property of being malleable (capable of changing its shape). Most plastics on the market are completely synthetic (most commonly derived from petrochemicals). However, given the growing environmental concern, plastics derived from renewable materials such as Polylactic Acid (PLA) are also popular on the market. Due to their low cost, ease of manufacture, versatility and water resistance, plastics are used in a multitude of products and sectors. In the AM sector, 3D printing plastics are also very popular.
In the following guide, we will take a look at the most common 3D printing plastics. As you may know, the most popular and affordable 3D printing process, FDM, produces parts through the extrusion of plastic filaments. However, the precision on FDM machines is not the same as other AM processes such as SLS or SLA. Plastics are often used with this technology to create prototypes. Therefore, for industrial and end-use parts, manufacturers might decide to opt for SLS (using plastic powders) or SLA (using plastic resins) technologies that offer more accuracy and part quality. Two other technologies that can print with plastics are Material Jetting and Multi Jet Fusion.
What plastics can be used in additive manufacturing? In filament or powder form, the plastic should melt to form the object you are printing layer by layer. In resin form, it should solidify to form the object. Each plastic will require different 3D printing parameters during the building process, and will give parts varying properties.
3D Printing Plastics: A comprehensive guide
ABS filament is the most commonly used 3D printing plastics. It is used in the bodywork of cars, appliances, and mobile phone cases. It is a thermoplastic which contains a base of elastomers based on polybutadiene, making it more flexible, and resistant to shocks. ABS can also be found in powder form for powder bed processes such as SLS, and liquid form for SLA and PolyJet technologies.
ABS is used in 3D printing when heated between 230ºC and 260ºC. It is a tough material, able to easily withstand temperatures of -20ºC to 80ºC. In addition to its high strength, it is a reusable material and can be welded with chemical processes. However, ABS is not biodegradable and shrinks in contact with air, so the printing platform must be heated to prevent warping. Moreover, it is recommended to use a closed chamber 3D printer to limit particle emissions when printing with ABS.
Known as polylactic acid, or PLA, this material has the benefit of being biodegradable, unlike ABS. PLA is manufactured using renewable raw materials such as corn starch. PLA is one of the easiest materials to print, though it does have a tendency to shrink slightly after 3D printing. You don’t require a heated platform when printing in PLA, unlike with ABS. PLA also prints at a lower temperature than ABS, between 190ºC to 230ºC.
PLA is a more difficult material to manipulate due to its high cooling and solidification speed. It is also important to mention that models can deteriorate when in contact with water. However, the material is consistent, simple to use, and comes in a wide variety of colors, making it suitable for FDM 3D printing
PLA 3D printing filament spools
ASA is a material that has similar properties to ABS, but has a greater resistance to UV rays. As with ABS, it is advised to print the material with a heated bed platform to prevent warping. When printing with ASA, similar print settings are used to ABS, but extra care must be taken to print with a closed chamber due to styrene emissions.
Polyethylene terephthalate, or PET, is commonly seen in disposable plastic bottles. PET is the ideal filament for any pieces intended for contact with food. Moreover, the material is fairly rigid and has good chemical resistance. To obtain the best results when printing with PET, print between 75 – 90ºC. PET is commonly marketed as a translucent filament, with variants such as PETG, PETE, and PETT also sold. Advantages of PET include that the material doesn’t release any odours when printing, and is 100% recyclable.
PETG, or glycolized polyester, is a thermoplastic widely used in the additive manufacturing market, combining both the simplicity of PLA 3D printing and the strength of ABS. It is an amorphous plastic, which can be 100% recycled. It has the same chemical composition as polyethylene terephthalate, better known by its acronym PET. Glycol has been added to reduce its brittleness and therefore its fragility.
Polycarbonate (PC) is a high strength material designed for engineering applications. The material has good temperature resistance, able to resist any physical deformation up to around 150ºC. However, PC is prone to absorbing moisture from the air, which can affect performance and printing resistance. Therefore, PC has to be stored in airtight containers. PC is highly valued by the AM industry for its strength and transparency. It has a much lower density than glass, making it particularly interesting for designing optical parts, protective screens or decorative objects.
High Performance Polymers (PEEK, PEKK, ULTEM)
The evolution of 3D printing technologies has led to extensive research work on printing materials, enabling the development of a whole range of high-performance filaments with mechanical characteristics similar to those of metals. There are several types of high-performance 3D printing plastics such as PEEK, PEKK or ULTEM – they are distinguished by family such as polyaryletherketones (PAEK) or polyetherimides (PEI). These filaments have a very high mechanical and thermal resistance, are very strong and at the same time much lighter than some metals. These properties make them very attractive in the aerospace, automotive and medical sectors.
Due to their characteristics, high performance polymers cannot be printed on all FDM machines on the market. Indeed, the 3D printer must have a heating plate capable of reaching at least 230°C, an extrusion at 350°C and a closed chamber. Today, about 65% of these materials are printed with FDM technology, but they are also found in powder form, compatible with SLS technology. Learn more in our dedicated guides on PEEK and PEKK.
Image via VisionMiner
Polypropylene is another thermoplastic widely used in the automotive sector, professional textiles sector, and in the manufacturing of hundreds of everyday objects. PP is known for its resistance to abrasion and its ability to absorb shocks, as well as relative rigidity and flexibility. However, drawbacks of the material include its low temperature resistance, and sensitivity to UV rays which can cause it to expand. Due to this, several manufacturers have developed alternative types of PP, simili-propilenos, that are stronger both physically and mechanically.
Objects made from polyamides (nylon) are usually created from a fine, white, granular powder with SLS technology. There are however some variants of the material such as nylon that are also available in filaments used in fused deposition modeling (FDM). Due to its biocompatibility, polyamides can be used to create parts that come into contact with food (except foods that contain alcohol).
Constituted of semi crystalline structures, polyamides have a good balance of chemical and mechanical characteristics that offer good stability, rigidity, flexibility, and shock resistance. These advantages mean that the material has many applications across sectors and offers a high level of detail. Due to its high quality, polyamides are used in the manufacture of gears, parts for the aerospace market, automotive market, robotics, medical prostheses, and injection molds.
Composites are extremely beneficial when making lightweight yet strong parts. The fibers add strength to a part without adding weight, which is why we also refer to composites as fiber reinforced materials. There are two types of reinforcements, short fiber or continuous fiber. In the first case, chopped fibers, which consist of segments less than a millimeter in length, are mixed into traditional 3D printing plastics to increase the stiffness and to a lesser extent the strength of components. Chopped fibers can be mixed with thermoplastics such as nylon, ABS or PLA.
Alternatively, the fibers can be added to the thermoplastics continuously to arrive at a stronger part. The main fiber used in the 3D printing sector is carbon fiber, but there are also other fibers such as glass fiber or Kevlar.
Carbon fiber reinforced filament spool
There are a variety of hybrid materials that mix base plastics with powders to give them a new color, finish or additional material properties. Often based on PLA, these materials are usually made of 70% PLA and 30% hybrid material. For example, wood-based filaments ranging from bamboo, cork, wood dust, and more are available. These wood-based materials mixed with PLA give the hybrid filament a more organic texture. Additionally, some hybrid materials incorporate metal powders to work with FDM-based technologies, to give parts a metal finish. They can be based on copper, bronze, silver, and more.
3D filaments based on wood.
Alumide plastic objects are manufactured from a combination of polyamides and aluminium powder using the SLS process. The material has a large, slightly porous surface and a gritty, grainy appearance offering great strength and good temperature resistance (up to 172°C). However, some post-processing treatments are necessary, such as grinding, sanding, coating, or milling.
Alumide is used for complex models, design pieces, or for small series production of functional models that need high rigidity and an appearance similar to aluminium. This technique involves few geometric limits.
Soluble materials are materials printed with the intention of being dissolved in a future stage of the manufacturing process. The two most common soluble filament materials are HIPS (High Impact Polystyrene) and PVA (Polyvinyl Acetate). HIPS is associated with ABS, and can be dissolved with limonene, whereas PVA is associated with PLA and can be dissolved using just water.
There are also BVOH filaments which are becoming increasingly popular, especially in dual extruder printers. This is because the material is soluble in water, and according to experts has a higher solubility than PVA.
A newer type of filament, and one of the most successful, are flexible filaments. They are similar to PLA, but usually made out of TPE or TPU. The advantage of using these filaments for 3D printing is they allow for the creation of deformable objects, widely used in the fashion industry. Generally, these flexible filaments have the same printing characteristics as PLA, though they come in a variety of ranges based on their stiffness. It is worth finding out which type of extruder is best suited to the material to avoid jams when 3D printing.
Flexible materials are widely used in fashion and design
Resins (for photopolymerization-based 3D printing)
3D printing technologies based on photopolymerization use UV-sensitive resins to create objects layer by layer. In other words, they use a light source such as a laser or LCD screen to solidify a liquid photopolymer. Technologies include SLA, DLP, and even Material Jetting (PolyJet). Creating parts using resins results in high detail and smooth surface objects, nevertheless, the color range is still quite limited using this process. What differentiates resins from FDM filaments is that it is impossible to mix resins to obtain different results quite easily.
Standard resin has properties similar to ABS: the surface finish of the part will be good given the photopolymerization process, however mechanical properties will be moderate. More advanced resins do exist for technical applications such as in dentistry (also need to be biocompatible), or engineering. Additionally, flexible resins that offer greater flexibility and deformation can be used to make jewelry. Over the years, manufacturers have expanded their range of liquid photopolymers to answer manufacturing needs from various sectors. Therefore, you should be able to find resins that have high-temperature resistance, can withstand large impacts, or that have high elongation properties.
The 3D printing resin is poured in a tank
Published on June 8, 2020 by Alexandrea P.