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Testing Low-Density Polyethylene Glass Composites in FDM 3D Printing

Wear resistance in 3D printed materials is critical for many users, with few research studies so far delving into such details for ABS or PC-ABS blends. Much of the concern is centered around anisotropic mechanical properties too, all in relation to ‘friction direction,’ with their findings outlined in ‘Preliminary Characterization of Novel LDPE-Based Wear-Resistant Composite Suitable for FDM 3D Printing.’

3D printout with possible anisotropy vs. friction direction.

The particle size distribution of the obtained glass powder (left) and the powder with low-density polyethylene (LDPE) granules (right).

Low-density polyethylene (LDPE) is a polymer used in many different types of packaging, and the authors point out that it is responsible for a substantial amount of waste—which optimally, should be recycled in FDM 3D printing. And while this is certainly not a novel idea, with the exercise of recycling plastic that has been discarded and grinding it into pellet or powder form for re-use being completely feasible, it is not a habit that has become widespread with users yet.

In exploring LDPE, the authors point out that it not only has inferior strength and stiffness but is also responsible for adhesion issues and high shrinkage—all qualities pointing to the need for a composite material with the potential for adding ceramic or metal.

“As mentioned before, adding ceramic or metal powders to LDPE can improve its storage modulus, reduce shrinkage, and increase its mechanical properties. Currently, LDPE composites with a mold flow index (MFI) of 10 g/10 min were successfully printed, so it is possible to manufacture an LDPE composite filament for FDM printing made from waste materials,” stated the researchers.

LDPE as a friction material offers potential, and especially when wear resistance is a critical issue; for example, the soles of shoes also require hardness, plasticity, elasticity, and more. LDPE can also be used as a near-surface filler or in creating products like sliding pads (commonly used with furniture).

The team created a composite, recycling even further with glass waste—obtained from shredded car windshields—refining both technological and wear-resistance properties and testing their results.

Composites exhibited suitable layer adhesion, devoid of cracks or voids. The research team employed a mathematical model for feed rate and printing speed—discovering in this study that the higher modulus allowed for more rapid printing, but also offered greater potential in defects due to the speed. Higher crystallinity was also found, but only slightly and ‘close to the error limit.’ The addition of the recycled glass was a suitable ‘reinforcement’ according to the researchers, who found that it did strengthen wear resistance further.

“An evident effect of the friction direction vs. the printed path direction on the wear appeared, which was probably related to differences in the removal of friction products from the friction area for different print-path layouts against the friction direction,” concluded the researchers.

“The LDPE composite with auto-screen glass particles is a promising material and should be studied further.”

Composites have become not only an interesting area of focus for 3D printing users but also a useful one as researchers and developers strengthen materials with wire composites, reinforced carbon fiber, and PLA. 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.

Composite filament microstructure: (a) LDPE15, (b) LDPE30

Composite filament microstructure: (a) LDPE15, (b) LDPE30

[Source / Images: ‘Preliminary Characterization of Novel LDPE-Based Wear-Resistant Composite Suitable for FDM 3D Printing’]

 

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Car Windshields to Be Ground Up for 3D Printing Materials? Polish Researchers Say Possibly

Researchers from Poland’s Silesian University of Technology are getting in on the recycling action via 3D printing, and the title of their recently published paper certainly grabs the attention, whether you are a tech buff or not. ‘The Use of Shredded Car Windscreen Waste as Reinforcement of Thermoplastic Composites for 3D (FDM) Printing,’ authored by Piotr Olesik, Mateusz Koziol, Daria Konik, and Jakub Jała, outlines their recent experimentation with shredded windscreen glass in FDM 3D printing.

Recycling of glass laminate in the auto industry can be an expensive venture if it is required that polyvinyl butyral (PVB) be removed. Methods involving turning waste glass into ceramic pellets or using it in making silicon carbide have been investigated but also, but in the end, much of this automotive glass waste is just tossed into landfills. Because of that burden on the environment, the researchers stress the need to improve the process.

Considering the amount of filament going into 3D printers today as the technology has hit the mainstream with continued, accelerated momentum, finding more recycled materials to put into the hardware makes perfect sense. And while shredded car glass may not have been on the minds of many innovators yet, the authors see this automotive material as having surprising potential for creating strong filament—despite the minimal exploration of 3D printing with glass composites so far. The same goes for filaments made from low density polyethylene (LDPE), which is a cheap plastic with high chemical resistance and flexibility.

Behavior of neat LDPE print and filament during printing at rates above 1 mm/s – visibly deformed filament and unsuccessful vestigial printout

In beginning their study, the researchers were able to obtain glass powder from ground windscreen glass waste to create a composite for 3D printing filament by adding low density polyethylene (LDPE). The powder still contained the PVB (polyvinyl butyral), however, which is a necessary component to safety glass as a binding resin that adds strength but also some degree of flexibility. By keeping it in the mix they were also able to eliminate the added expense of removal.

The filament for FDM printing was created through extrusion winding, and open-air cooling—resulting in 1.45±0.05 mm material, and a reduction in filament strength as the glass content increased. The researchers set to work in assessing the potential of the materials, with printing temperature ‘selected experimentally’ during multiple trials (with the best print results set at 250°C and table temperature of 90°C).

“During printing, an unfavorable effect of filament bending was observed in the printer, below the supplying roller. This effect occurred during printing at a supply speed of more than 1 mm/s. Special additional printing tests with supply rates below 1 mm/s were carried out. This made the printing possible, and it showed the evident superiority of the composites over the neat LDPE.”

Printouts obtained at low printing rate from tested materials: a) LDPE100, b) LDPE085, c) LDPE070

The researchers were able to solve the problem by stiffening the line between the rollers, but this required customized inserts. Overall, they noted LDPE printing as having potential in FDM 3D printing, but only at low printing speeds (with the inserts).

“The addition of shredded car windscreen glass slightly (but clearly) improves the behavior of the LDPE filament during the printing process, significantly improves the quality of the obtained printouts, and especially reduces shrinkage during cooling,” concluded the researchers. “The amount of 30% by weight of glass should be rather treated as the minimum amount to obtain the desired effects.”

“Further work on the use of LDPE in FDM printing should focus on the possibility of accelerating the printing rate by making design changes in printers (larger supply nozzles), or ensuring adequate stiffness of the material itself – e.g. by creating custom blends (with polypropylene or polystyrene) and, obviously, by producing composites with hard components.”

While much of the technology realm is wonderfully unpredictable, one thing is for certain, 3D printers around the world are getting a constant workout with an infinite supply of new materials for new ideas. Researchers in China have been inspired by origami to create 4D metamaterials, the Swiss have been experimenting with Multi-Metal Electrohydrodynamic Redox 3D Printing, and others are looking into fabrication with glass-ceramics at the nanoscale. Find out more now about the uses of recycled auto glass in 3D printing here. 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:‘The Use of Shredded Car Windscreen Waste as Reinforcement of Thermoplastic Composites for 3D (FDM) Printing,’]