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Brazil: Experimenting with Recycled ABS & PLA for Dosimetry

Brazilian researchers seek an environmentally friendly method not only for 3D printing but to put discarded plastic to use in dosimetry, a method for measuring radiation therapy. Outlining their findings in the recently published ‘Reuse of 3D printed materials for dosimetry purposes,’ the authors focus on ABS and PLA.

Material (PLA) prepared for the application of the recycling tests.

While a huge variety of materials are now available on the market, ABS and PLA still prevail due to their accessibility and affordability. 3D models can be easily created and while they are helpful in the medical field for everything from educating patients to being used for diagnosing, treating, and surgical planning, they can also be used as phantoms for ionizing radiation dosimetry.

Schematic assembled for obtain Kerma rate values.

While there is a need for characterization of 3D printed samples, the researchers considered the true feasibility of recycling plastic filament for use in dosimetry. In this study, the team attempted to re-use transparent PLA and black ABS.

Characterization of radiation quality series RQT

The researchers printed two samples with recycled PLA and ABS materials for experimentation, measuring 7cm in diameter and 9mm in thickness. The images were analyzed in a CT scanner, targeting one area of interest and measuring Hounsfield units (HU).

Overall, the team reported PLA as the winner in terms of offering ‘better performance’ due to homogeneity; even so, ABS performed fairly well despite a make up of petroleum. Heading into the experimental phase with materials, the research team had expectations that there would be problems with the ABS materials; however, the team reported ‘satisfactory’ results.

“After the readings with the ionization chamber, correction factors were applied, in order to obtain the Kerma values to evaluate the materials,” explained the team.

measured values in Hounsfield units for each sample

Ultimately, the researchers came to the conclusion that the variations found in the samples could have been a consequence of material density that resulted from the recycling process. There were numerous questions surrounding the use of typical parameters, as well as how they cause different reactions due to the differences in the material once it has been recycled.

Samples printed in transparent PLA and black ABS for comparison with recycled samples

“Different printing parameters may be applied during prototype acquisition, which influence the amount of material deposited on each printed layer and, depending on the type of printer used and the print setting, these layers may have air holes between them,” concluded the researchers the end of their study.

“Although high quality printing parameters were chosen in this paper, the results for the samples point to a difference between the densities of recycled and printed PLA/ABS samples. For more inclusive analysis, studies can be performed with samples from different printers to define the best print resolution to compare with samples of fused materials.”

What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘Reuse of 3D printed materials for dosimetry purposes’]

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Brazil: Researchers Test the Potential of Recycling PLA for Greater Sustainability in 3D Printing

Brazilian researchers are interested in furthering not only the benefits of 3D printing but also the advantages of PLA’s biodegradability for ease in recycling. Their findings are further outlined in the recently published, ‘Recovery and recycling of a biopolymer as an alternative of sustainability for 3D printing.’ With the intent to motivate users to follow through with mechanical recycling of PLA, the researchers have started a program to do so on their end at the Materials and Design Laboratory at University of State of Pará.

3D printer on the left and PLA filament coil ready to be printed.

As the problem of trash and waste disposal—and the ever-growing amount of plastic—continues to be an enormous point of concern regarding our planet and the ongoing havoc humans wreak—alternatives must be considered for many different materials. Polylactic acid (PLA) is attractive to many users because it is a non-toxic, thermoplastic material—a biopolymer—and it is biodegradable due to its plant-based origins. While PLA and its other popular cousin in 3D printing, Acrylonitrile Butadiene Styrene (ABS) are both extremely popular, the business of materials is exploding within the industry—and with more prints comes more discards.

With PLA at least there is more of a head-start regarding a positive environmental factor, and users—as well as the industry overall—should realize their options in recycling and leaving behind even less of a footprint. The researchers were able to collect PLA from a local 3D printing services bureau for recycling, and material was separated out by color, and then dried. Afterward, they added wood granules and jute to the PLA material. The material was then melted and analyzed by the team.

“The addition of lignocellulosic reinforcements to thermoplastic polymers is environmentally interesting,” stated the researchers. “The wood waste can return to the production chain and can generate new products when added to thermoplastic resins. The jute fiber mainly used in packaging can now be able to generate other products with PLA biopolymer.”

PLA wastes used in this work (left), enameled pan and silicone mold (right)

PLA waste can be easily recycled due to the low melting temperature of this polymer. The tablets can be saved to use in other researches, or mixed with cellulosic fibers to consolidate composite plates.

Plates of PLA recycled with the addition of wood granules consolidate with no pressure, showing mold contact surface and the opposite surface, where we can observe that the fast cooling after leaked promote an irregular surface texture mainly on the free surface of the sample.

It is possible to observe the aspects of the plates produced with the recycled PLA with addition of jute fiber of 1.5 to 2,00 centimeter, consolidated under pressure, showing the regularity on the surface on both sides. For these samples light color waste was selected.

“Considering the problem of the increase of materials waste generated from 3D printing, a process that tends to become popular, and few researches were found in the literature focusing on the recycling of these materials, this work contributed to the identification the residue of PLA discarded in the digital manufacturing activities as a possible raw material for new products through the recycling process.”

“The waste recycling of 3D printing is a sustainability alternative for this activity; As future research it is proposed to carry out physical and mechanical characterization of the samples made from the recycled PLA,” concluded the researchers.

While recycling is an ongoing conversation around the world, it is especially emphasized in the realm of 3D printing where a wide range of plastics are used and often discarded. Researchers and enthusiasts around the world are engaged in innovative projects to recycle powder into filament, into prosthetics, and even metal stock into components for the military. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘Recovery and recycling of a biopolymer as an alternative of sustainability for 3D printing’)

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Recycled PLA Shows Highly Variable Strength

3D printing, as well as 4D printing, have opened up an ever-expanding realm of hardware, software, and unique methods for constructing complex geometries. Along with that though also comes a vast array of materials which is continually growing—but many researchers and engineers still use the old standbys like ABS and PLA.

Efforts to recycle 3D printed items are a constant source of study too, as researchers worry about the amount of plastic that could be left sitting in landfills, even if it is eventually biodegradable, as is the case with PLA. In ‘A comparison between mechanical properties of specimens 3D printed with virgin and recycled PLA,’ Italian researchers Antonio Lanzottia, Massimo Martorelli, Saverio Maietta, Salvatore Gerbino, Francesco Penta, and Antonio Gloria further explore the realities of using recycled PLA for functional parts.

An image of the filament extrusion

PLA is popular in comparison to ABS because it is a bio based polymer. The authors point out that composting the material is probably not a very realistic solution due to the amount of time it takes parts to degrade. But, what if we could recycle PLA? How feasible is this and how does this affect the material? What happens to mechanical strength of material that has been recycled—especially if it has been recycled repeatedly:

“Specifically, it has been proved that the use of a filament recycled twenty times through an extrusion-based process minimally affected the tensile strength and modulus of PLA,” state the researchers.  “In  addition, a study on recycled polypropylene blends in injection moulding procedure was performed and  an  appropriate  blending  ratio  of  virgin  and  recycled  polymer  was  assessed,  showing  that  the  decrease  in  the mechanical properties of devices fabricated from recycled polymers may be improved optimizing the process parameters during  the  injection moulding.”

Further studies also showed that weakening in mechanical properties was minimal in recycled PLA, motivating the authors to form an intense study comparing both virgin PLA and recycled PLA, testing both interlaminar properties and short-beam strength. PLA samples were printed at 200°C using a Prusa I3, with a .4 mm nozzle. The first set was tested, then ground up and recycled with a homemade extruder into 1.75 mm material. It was then used to make new samples for mechanical property testing.

Schematic representation of the experimental setup – horizontal shear load diagram (adapted from ASTM D2344)

The researchers included three different recycling phases, with testing for short-beam strength on both virgin and recycled material. They noted that the PLA recycled once and even twice over was not ‘significantly’ affected in short-beam strength, but after that it did experience substantial degradation. In the samples that had been recycled three times, there was ‘great variability.’

In conclusion, the researchers offered more specific data:

“The  one-time and twice recycled  specimens  showed  a  short-beam  strength  (106.8  ±  9.0  MPa  and  108.5  ±  9.9  MPa,  respectively)  which  was  similar  to  that  of  the  virgin  specimens  (119.1  ±  6.6  MPa).  However,  a  third  recycling  process  negatively  affected  the  values  of  the  short-beam  strength  also  producing  a  great  variability in the results (75.0 ± 16.2 MPa).”

3D printing, in existence since the 80s, has only just begun to really hit its stride—and the study of materials science has become of substantial interest to many, whether they are interested in using PLA or recycled materials to create items like energy storage devices, prosthetics, sustainable thermoplastics, and so much more. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: A comparison between mechanical properties of specimens 3D printed with virgin and recycled PLA]

Results from mechanical tests: typical failure modes