11/8/23
Part 8 of the 9 Part Series will describe how 3D printing technology influenced the environment during its time.
You‘ve just finished a print using your 3D Printer. Some supporting material was generated to maintain the structures of the print. But with that completed and the supporting material removed, what do we do with the leftover plastic? This article will describe how unused plastics from 3D printers are recycled, the potential for composting, strategies to curtail plastic waste, and more for a sustainable future.
When plastic finds its way to a recycling center, it embarks on a journey. The first stop is thorough cleansing, followed by meticulous sorting, precise shredding, and eventually, a transformation into small pellets, which serve as the building blocks for creating new products. These vital steps can either transpire under one roof or span multiple facilities.
However, regardless of the operational scale, the sorting phase emerges as the pinnacle of the recycling process—the integrity and durability of the final product hinge on preventing cross-contamination among different types of recycled plastics. Therefore, plastic sorting plants employ diverse techniques to segregate plastic types, ranging from manual sorting by skilled hands to state-of-the-art infrared detectors. In recyclable 3D printing filaments, PLA and PETG are the most widely known, wielding significant influence.
Understanding Thermosets and Thermoplastics in 3D Printing
Plastics, those versatile materials that have revolutionized manufacturing, can be conveniently categorized into two distinct groups: thermosets and thermoplastics.
Thermosets represent materials undergoing molding and subsequent curing processes to achieve their final forms. Prominent members of this group include polyurethane and silicone. In 3D printing, thermosets primarily find their utility in vat polymerization printing. It's worth noting that thermosets are notably challenging to recycle, be it in their 3D-printed or non-printed forms.
Conversely, thermoplastics sidestep the curing phase, achieving malleability when exposed to temperatures exceeding their respective melting points. Consequently, all Fused Deposition Modeling (FDM) 3D printers rely on thermoplastic filament materials.
In principle, most varieties of thermoplastics can be subjected to melting and recycling. However, the efficiency of this process and the degree of material loss may vary between different types. Notably, the array of plastics processed at recycling facilities can exhibit considerable disparity globally and within other neighborhoods within the same city.
For instance, nearly every recycling center routinely handles PET and HDPE, the building blocks for plastic bottles and food containers. Despite its extensive European recycling practices, PVC maintains a lower profile in North America's recycling landscape.
3D Printing Filaments and Recycling Challenges
Still, when recycling some of the classic 3D filaments, things get complicated. Two prominent filament types, ABS and PLA, are excluded from most municipal recycling programs. According to the ASTM International Resin Identifier Codes, these materials fall into the enigmatic Type 7 category, known as "Other," a classification seldom handled by such programs. Regrettably, tossing your failed ABS and PLA prints into the recycling bin isn't a viable option.
Surprisingly, PETG, a filament closely related to PET, faces similar recycling hurdles. Their chemical likeness makes PETG a challenging contaminant during PET recycling processes. Combining PETG with PET in the recycling stream can lower the mixture's melting point and compromise thermal stability, leading to the unfortunate destination of the incineration pile.
Polypropylene (PP) filament, with its semi-crystalline nature and notable warping tendencies during cooling, isn't a common choice for 3D printing. Nevertheless, some municipalities do accept PP for recycling. If you are among the adventurous few who opt for PP in 3D printing, consider contacting your local recycling center to determine whether they accommodate this material.
Regrettably, the woes of 3D printing filament recycling extend beyond just ABS, PLA, PETG, and PP. Nearly all other filament varieties, including nylon and polycarbonate, share the Type 7 classification, rendering them typically unprocessable by standard plastic recycling facilities.
But this begs the question. How can I become more environmentally aware while using my 3D Prints? This is a question we will talk about in our next and final article on the topic.
Keywords: Relics, Renaissance, Repair, 3D Printing, Environment, Metal deposition, Aerospace, Military, Education, STEM, Additive Manufacturing, PLA, ABS, Carcinogenic, Eco-Consciousness, Environment, ASTM International Resin Identifier Codes, Type 7 Category, Polypropylene (PP) Filament, Thermoplastic, Thermosets, Health Hazards, 3D Printing Overview, Leftover Plastic 3D Printing Recycling.
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