Chemicals Behind 3D Printed Filaments And Resins

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3D printing technology is more and more widely used in various industries. Nowadays, 3D printer is not only an indispensable tool in companies, but also a common phenomenon in many companies. Among the local engineers, they like DIY, fixed items and rapid prototyping products very much.

In this paper, we investigate the chemical properties of commonly used 3D printing filaments and resins, and try to reveal the dark side of the home additive manufacturing process. If you are not printing in a garage or other large ventilated space, it is recommended to open the window before printing. Wise selection of filaments and resins is encouraged as certain materials may pose serious health risks.

Introduction to FDM 3D printing:

The most popular type of 3D printing on the hobbyist market is based on the melting of so-called filaments (polymer filaments), which solidify as they cool. This process is called melt deposition modeling (FDM). In this type of printing, the molten material is pressed out through a fixed small diameter nozzle to print in layers.

FDM printing can be done with almost all materials provided that the following basic conditions are met: low melting point (about 180-250 ° C for most printers), low thermal expansion (to prevent clogging), low abrasiveness (delicate protection) nozzles, and specific heat capacity, suitable for rapid heating and cooling.

Naturally, special filaments can change these rules to allow melting points up to 400 ° C or higher, or have higher expansion rates (light bubble filaments), but in this article, we will focus on more popular solutions that may be found in desktop 3D. printer. Most of the filaments used in FDM printing are made of synthetic polymers, which release toxic volatile substances when melted. Among the various filaments on the market, only a few are classified as safe or food grade by FDA.

In general, the safest one may be PET-G (polyethylene glycol modified) filament [2]. However, even if PET-G is used, if the same printer is used to print with other materials with higher toxicity, there is a risk of releasing toxic compounds (due to residues).

Why printing filaments is dangerous?

The general process of releasing toxic chemicals in FDM 3D printing process is based on the degradation of the filament under high temperature treatment, which leads to the release of volatile chemical compounds (VOCs), which have a negative impact on health. Some of them irritate the eyes and can be absorbed by inhalation and condensation to tissues (e.g. skin) [3,4].

In the process of filament melting, the compounds which have the greatest impact on eyes and respiratory system are methyl methacrylate [5], acetic acid [6], caprolactam [7], toluene [8], formaldehyde [9] and their derivatives. Prolonged exposure to these volatiles can cause serious health problems. These compounds affect mucous membranes and are associated with asthma, tissue inflammation and many allergies. They can also cause neurological problems, such as headaches. Toluene exposure may affect the heart and nervous system [10,11].

Some VOCs released from filaments have even greater effects on living organisms. Examples include benzene [12], benzore and its derivatives [13], ethylbenzene [14] and tetrachloroethylene [15]. These are classified as carcinogens, so long-term exposure to smoke can cause serious health problems.

Filament example:

No matter which filament is used, ventilation measures should be taken to prevent exposure to VOC emitted during printing. Here we list some of the materials and their possible health effects:

Because of its flexibility and low price, the most common one is ABS (acrylonitrile butadiene styrene). However, the melting of ABS will lead to its thermal degradation, which will lead to the evolution of toxic VOCs, such as xylene, benzene, toluene and ethylbenzene [1,3,16]. ABS is proud of its resistance, toughness and flexibility. The ABS printed object is durable, however, this material should not be used at home unless a special smoke chamber is used.

Synthetic polymers such as polyethylene (PP), polyamide (nylon), thermoplastic polyurethane (TPU) and other plastics that are easy to form. The release of toxic VOCs from these filaments is not only caused by the degradation of the filaments themselves during melting, but also from the chemicals used in the production of the filaments. They may even contain bisphenol A, an endocrine disruptor that can easily cross biofilms and affect the endocrine system [17].

PLA (polylactic acid) is a natural material with soft texture, easy printing and post-treatment (including painting) after printing. PLA also releases some VOCs, but the amount is small and the harm to health is small. When printing, PLA mostly emits 1-butanediol, methyl methacrylate and a small amount of other chemicals [1,3]. Even if this material is natural, it will release some dangerous chemicals when it melts. Therefore, as long as proper ventilation precautions are taken, PLA is safe for Home 3D printing.

Conclusion on the health effects of FDM 3D printing.

FDM 3D printing requires high temperature to melt the solid filament. Then, a lot of different VOCs are released, but that's not a long list of chemicals. Filaments also contain heavy metals, which increase the risk of many health diseases and even cancer.

When they come into contact with the skin, they are absorbed, causing tissue aggregation and subsequent diseases. However, some filaments are relatively safe (PET-G, PLA), and even indoor printing should be absolutely acceptable if adequate ventilation is provided. Users must be aware of the possible negative health effects of printed materials (e.g. ABS) or pet metal particle composites (e.g. pet + copper composites).

3D printing resin for SLA / DLP printers:

In addition to FDM printing, resin printing has recently entered the internal consumer printing market, so it is very popular. In principle, the resin 3D printing is completed by exposing the photosensitive liquid resin to ultraviolet light and curing it into a solid. Any material that can be cured by exposure to ultraviolet light without expanding its volume in the process can be used as a printing resin.

In general, resins are absolutely not safe in terms of health effects. They are usually made from a mixture of different organic compounds, such as acrylates or epoxy resins, but this is only the beginning of a very long list of chemicals contained in the resin. Suppose this is the subject of another story.

Volatile compounds released during printing with resins include, but are not limited to: phthalates, methyl methacrylate, acrylic acid and more acrylate compounds. In addition, the resin contains compounds that may leak, such as bisphenol A. In addition, resins contain heavy metals, which can have adverse health effects if exposed to them directly.

These metals mainly include chromium, arsenic and copper. Therefore, unless appropriate safety measures are taken, the resin is not safe for domestic use. These measures include always using gloves when handling resin, ventilating the printing area well, and using a fume hood and a high-quality ffp3 mask to protect the respiratory tract. These measures should prevent exposure to volatiles released during printing.

If the resin is in direct contact with the skin, the skin must be rinsed with water several times immediately. If further symptoms occur, contact a doctor immediately. Compounds released during resin printing are easily absorbed by organisms. It is strongly recommended to reuse protective gloves and particle filter masks.

generalization:

In recent years, 3D printing technology has made great progress in printing quality and speed. However, there is still a need to develop new, safe materials for printing. Most of the polymers and resins currently available pose some health risks. Management can be achieved by taking appropriate precautions, such as avoiding direct contact with the resin or ventilating the printing area. Printing is safe, but only if it is done correctly.