Bielefeld UAS: 3D printing process for stab-r...
Bielefeld UAS

3D printing process for stab-resistant protective clothing

3D printing with resin on textile: StereoTex's first trials have already been successful (Source: FH Bielefeld)
3D printing with resin on textile: StereoTex's first trials have already been successful (Source: FH Bielefeld)

Optimizing protective clothing for occupational groups potentially at risk of bodily harm, such as the police or security firms: That is the goal of the StereoTex research project at Bielefeld University of Applied Sciences (UAS), Bielefeld/Germany. In the project, researchers are currently developing a process that makes it possible to produce stab-resistant protective clothing from a combination of textiles and synthetic resins.

A transparent box just under 25 cm tall with orange-tinted panes and a small black basin with a glass bottom: What seems rather unimpressive at first glance is a complex 3D printer with state-of-the-art technology in the laboratory for Textile Technologies at Bielefeld UAS. This innovative process combines textile and synthetic resins.
The process is part of the StereoTex research project, anchored in the Faculty of Engineering and Mathematics, and uses the stereolithographic 3D printing process (SLA) as the foundation for its research. This is a process in which 3D objects are modelled from resin. The starting point is liquid resin, which is filled into a basin and cured layer by layer into the desired 3D objects. A light source, such as a laser or UV light, is used to aid the curing process. This is a well-known and frequently used technique in the 3D printing sector. What is particularly special about the project’s process? The 3D objects are printed directly onto textiles, which are fixed to the print bed using an in-house developed bracket.
The StereoTex team is working towards a very specific application scenario for their research. The aim is to develop individually adaptable resin-textile composites that have a stab and cut-resistant effect. To put it into concrete terms, this means that the resin-textile composites shall be used to produce protective clothing for potentially vulnerable occupational groups, such as the police force, security firms or bus and taxi drivers. It is particularly important that the composite materials are breathable and have a long-term durability of at least 10 years. Especially for protective gear that has to be worn very close to the body for several hours a day, it is necessary that it is light and comfortable, and still offers both good and long-lasting protection.

The 3D objects made of synthetic resin are cured with UV light (Source: FH Bielefeld)
The 3D objects made of synthetic resin are cured with UV light (Source: FH Bielefeld)
Since the synthetic resins available on the market are not optimized for the novel process, the researchers are cooperating with the Alwa GmbH, Gronau/Germany, which specializes in casting resin systems, to jointly develop an innovative, porous resin that can be printed on textiles without any problems and is permeable to air and water at the same time. So far, this resin only exists as a casting resin and will therefore be further developed as a printable resin in the forthcoming stage.
Although the project is still in its early stages, it has already achieved some initial successes. In order to find out which textiles are best suited for the application scenario, various textiles were printed with commercially available UV resin. The researchers are currently investigating which textile properties are best suited for adhesion of the resin as well as in long-term performance as a textile-resin composite. In the process, various shapes and sizes of 3D objects on the textiles were tested. These include smaller and larger cylinders, as well as elongated square structures overlapping like roof tiles, modelled on historical armor and shell from the animal realm.

StereoTex uses the stereolithographic 3D printing process as the basis for its research – a process in which 3D objects are modeled from resin (Source: P. Pollmeier/FH Bielefeld)
StereoTex uses the stereolithographic 3D printing process as the basis for its research – a process in which 3D objects are modeled from resin (Source: P. Pollmeier/FH Bielefeld)
In the next stage, a hybrid 3D printer shall be developed that, similar to the SLA process, uses liquid synthetic resin and UV light for the curing process. However, the printer will also apply the synthetic resin to the textile in a way comparable to the so-called Fused Deposition Modelling (FDM) technology, one of the most widespread 3D printing technologies worldwide. In this process, plastic that is typically melted is applied layer by layer in the desired shape to a platform using a print head, where it cools and hardens. After that, the 3D object is ready. Transferred to StereoTex, the goal is for liquid resin to be applied to the textile underneath with mm precision from above, as is the case with FDM printers. At the same time, the aim is for the liquid resin to be cured directly by a UV source. This would have the decisive advantage that the textiles would no longer have to be placed in a basin of liquid resin, meaning the time-consuming step of removing the excess, uncured resin from the fabric would no longer be necessary. Additionally, materials could be saved and the environment could be protected.
This Article was published in Technical Textiles 5/2022

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