Plastic is a material made from synthetic or semi-synthetic compounds that has the ability to change its shape. Most plastics on the market are entirely synthetic. However, with the growing global concern for the environment, there is also the presence of plastics made from renewable materials, such as polylactic acid (PLA) used in 3D printing.
Thanks to its low cost, easy production process, flexibility, and water resistance, plastic is a material used in numerous fields.
What are the most common plastics for 3D printing?
The most popular and accessible process for 3D printing is Fused Deposition Modeling (FDM) - modeling by depositing melted material. In FDM, parts are produced by extruding plastic filaments.
"However, the accuracy of FDM machines is not the same as other AM processes (Additive Manufacturing), such as SLS (Selective Laser Sintering) or SLA (Stereolithography)."
Plastics are often used with this technology for prototyping. This means that manufacturers can choose SLS or SLA technologies, which work with plastic powder particles or plastic resin and offer greater precision and quality.
The technologies Material Jetting and Multi Jet Fusion can also be used for 3D printing with plastic.
What plastics can be used in AM production?
Whether in the form of filament or powder, to form the object you are printing layer by layer, the plastic must be melted. However, if it is in the form of resin, the material must harden.
During 3D printing, each plastic requires different parameters and imparts different properties to the individual parts.
ABS
ABS (Acrylonitrile Butadiene Styrene) is a flexible and durable thermoplastic polymer that is commonly found in the industry. It is used in the body of cars, appliances, and mobile phone cases. It can also be found in powder form for processes like SLS, and in liquid form for SLA and PolyJet technologies.
ABS is used in 3D printing at temperatures between 230ºC and 260ºC. Thanks to its durability, it can withstand temperatures from -20ºC to 80ºC.
However, ABS is not biodegradable and shrinks upon contact with air. To prevent warping, the print bed must be preheated.
"When working with ABS, it is best to use a 3D printer with an enclosed chamber to limit particle emissions."
PLA
PLA (Polylactic Acid) is a biodegradable material produced from renewable resources. It is one of the easiest materials to print with, although slight shrinkage after printing is sometimes observed.
Unlike ABS, a heated bed is not required for PLA. The temperature at which this plastic can be processed for 3D printing ranges between 190ºC and 230ºC.
The peculiarity of PLA, compared to ABS, is that this material is more difficult to process due to its tendency to cool and harden quickly. There is also a risk that the models may be damaged upon contact with water.
The advantage of PLA is that it is an easy-to-use plastic that is available on the market in a wide variety of colors, making it suitable for FDM 3D printing.
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ASA (Acrylonitrile Styrene Acrylate) has the same properties as ABS, but is more resistant to UV rays. It is also advisable to work with a heated platform when using ASA to prevent warping. Additionally, extra care should be taken when printing with an enclosed chamber due to styrene emissions.
PET
PET (Polyethylene Terephthalate) is suitable for making plastic containers, bottles, and utensils intended for food contact. This material has good chemical resistance, does not emit any odors during printing, and is 100% recyclable.
'For optimal results, the printing temperature should range between 75ºC and 90ºC. You can find PET on the market as a translucent filament. Other variants of this material are PETG, PETE, and PETT.'
PETG
PETG (Glycolized Polyester) is a thermoplastic widely used in the AM market. It combines the ease of PLA 3D printing with the strength of ABS.
PETG is an amorphous plastic that, like PET, can be 100% recycled, as it has the same chemical composition. The added glycol reduces the brittleness of the material and therefore its fragility.
PC
PC (Polycarbonate) is a material with high strength, primarily intended for engineering applications. It can withstand various physical deformations requiring high temperatures - up to about 150ºC.
However, please note that polycarbonate is prone to absorbing moisture from the air, which can affect the quality and durability of the print. To avoid this, it is recommended to store the material in airtight containers.
The durability and transparency of PC make it a highly valued material in the AM industry. Since it has a lower density than glass, it is suitable for designing optical parts, protective screens, or decorative items.
High-performance polymers (PEEK, PEKK, ULTEM)
As the popularity of various 3D printing technologies grows, the use of materials that allow for the development of a whole range of high-performance fibers with mechanical properties similar to those of metals is also increasing. There are several types of high-performance 3D printing plastics such as PEEK, PEKK, or ULTEM, which are distinguished by their type as polyaryletherketones (PAEK) or polyetherimides (PEI).
"Besides the fact that these fibers have very high mechanical and thermal resistance and strength, they are much lighter than some metals. This is precisely why they are often used in the aerospace, automotive, and medical sectors."
Due to their specific characteristics, high-performance polymers cannot be printed on all FDM machines available on the market. For this purpose, the 3D printer you are working with must have a heated bed capable of reaching at least 230°C, extrusion at 350°C, and a closed chamber.
"Nowadays, approximately 65% of these materials are printed using FDM technology. Also, they can be found in powder form, compatible with SLS technology."
PP
PP (Polypropylene) is a type of thermoplastic with wide applications in the automotive sector, the professional textile sector, and in the production of numerous everyday items. It is characterized by its high wear resistance, exceptional flexibility, and ability to absorb impacts.
Some of the disadvantages of polypropylene are its low temperature resistance and sensitivity to UV rays, which leads to material expansion. Since these issues are common, some manufacturers have developed alternative types of PP that are stronger both physically and mechanically.
Nylon
Most often, items made from nylon (polyamides) are produced from fine, white granular powder using SLS technology. However, some variants of this material are also available in the form of filaments, which are used in FDM 3D printing.
Nylon is a stable, hard, flexible, and impact-resistant material, with an excellent balance between chemical and mechanical properties. Due to its biocompatibility, it can be used to create items that come into contact with food (except for foods that contain alcohol).
Thanks to the aforementioned qualities of nylon, it has numerous applications in various sectors, including the aerospace market, the automotive market, and robotics.
Composites
Composites are suitable when you are making lightweight yet strong parts, as they increase the strength of a given element without adding weight. Reinforcing materials exist in two forms - as short or as continuous fibers.
In the first case, the cut fibers, which consist of segments shorter than a millimeter, are mixed into traditional plastics for 3D printing to increase the stiffness and, to a lesser extent, the strength of the components. They can be mixed with thermoplastic materials such as nylon, ABS, or PLA.
"As an alternative, fibers can be continuously added to thermoplastics to create a stronger part. In 3D printing, carbon fibers are primarily used, but other fibers such as glass fibers or Kevlar can also be used."
Hybrid materials
There are various hybrid materials that combine base plastics with powders to give them new color, coating, or additional properties. Most often, 70% of their composition is PLA. The remaining 30% can be wood-based fibers, ranging from bamboo, cork, wood powder, and others. In combination with PLA, these materials give the hybrid filament a more organic texture.
Other hybrid materials include metal powders designed for use with FDM-based technologies, which give the parts a metallic finish. They are based on copper, bronze, silver, and others.
Alumide
Alumid plastic items are a combination of polyamides and aluminum powder. They are produced using SLS technology.
The material has a large, slightly porous surface and a sandy, grainy appearance, offering great strength and good temperature resistance - up to 172°C. However, due to this type of surface, some finishing processes such as smoothing, grinding, and milling are necessary.
Alumid is used in the construction of complex models, designer items, or for small functional objects that require high hardness and an appearance resembling aluminum.
Soluble materials
Soluble materials are created with the intention of being dissolved at a later stage of the production process. The two most commonly used soluble filament materials are HIPS (High Impact Polystyrene) and PVA (Polyvinyl Acetate).
HIPS is associated with ABS and can be dissolved with limonene, while PVA is associated with PLA and can only be dissolved with water. There are also BVOH filaments, which are becoming increasingly popular, especially in 3D printers with dual extruders. This is because the material is water-soluble and, according to experts, has a higher solubility than PVA.
Flexible materials
Flexible filaments are an innovative and extremely successful type of filament. They resemble PLA, but are usually made from TPE or TPU - thermoplastic elastomers or rubber-like materials.
The advantage of using these filaments for 3D printing is that they allow the creation of deformable objects, widely used in the fashion industry. They have the same properties as PLA, but are available in different ranges based on their hardness.
When working with such flexible materials, it is important to choose the right extruder to avoid clogs during printing.
Resin (for 3D printing based on photopolymerization)
3D printing methods based on photopolymerization use UV-sensitive resin to create objects layer by layer. That is, they use a light source such as a laser or LCD screen to cure liquid photopolymer. These technologies include SLA, DLP, and PolyJet.
The construction of parts using resin leads to the creation of models with high detail and significantly smooth surfaces. However, a drawback can be noted in the limited color range when working with such material.
The standard resin for 3D printing has properties similar to ABS. There are also more modern resins for technical applications in dentistry, engineering, and other sectors.
There are also other types of resin that offer greater flexibility and can be used for making jewelry.
Over the years, manufacturers have expanded their range of liquid photopolymers to meet the production needs of various sectors. As a result, on the market, you can find resins that have high temperature resistance, can withstand large impacts, or have high elongation properties.
