UNSW engineers have demonstrated a way to help 3D printed plastic heal
itself at room temperature using only lights.
Professor Cyrille Boyer and his team, Dr. Nathaniel Corrigan and Mr Michael
Zhang, in the UNSW School of Chemical Engineering have shown that the
addition of "special powder" to the liquid resin used in the printing
process can later assist with making quick and easy repairs should the
material break.
This can be done very simply by shining standard LED lights on the printed
plastic for around one hour which causes a chemical reaction and fusion of
the two broken pieces.
The entire process actually makes the repaired plastic even stronger than it
was before it was damaged, and it is hoped that further development and
commercialisation of the technique will help to reduce chemical waste in the
future.
That is because broken plastic parts would not need to be discarded, or even
recycled, and could be mended simply even when remaining embedded in a
component including many other materials.
The results of the team's research have now been published in the journal
Angewandte Chemie International Edition.
Reducing plastic waste
"In many places where you use a polymer material, you can use this
technology. So, if a component fails, you can repair the material without
having to throw it away," said Dr. Corrigan.
"There is an obvious environmental benefit because you're not having to
re-synthesize a brand-new material every time it gets broken. We are
increasing the lifespan of these materials, which is going to reduce plastic
waste."
The powdered additive the UNSW team use is a trithiocarbonate, known as a
reversible addition fragmentation chain transfer (RAFT) agent which was
originally developed by CSIRO. The RAFT agent enables rearrangement of the
nanoscopic network of elements that make up the material and allows the
broken pieces to be fused.
This occurs within approximately 30 minutes when UV LED lights are shone
directly onto the broken plastic, with full healing taking place after
roughly one hour.
Experiments, including on a 3D printed violin, show that the self-repaired
plastic's strength is fully recovered compared to its original unbroken
state.
The team said commercialisation of the process is possible given the
simplification and speed of their system compared to existing ways of
repairing broken 3D printed materials.
"There are other processes that do this, but they rely on thermal chemistry
to repair the material and typically it takes around 24 hours and multiple
heating cycles to achieve the same type of result," Dr. Corrigan said.
"Another restriction to that is that you need an oven which is heated to
high temperature and you obviously cannot repair the plastic material in
situ—you would need to disassemble it from the component first which adds a
level of complexity and delay.
"With our system, you can leave the broken plastic in place and shine the
light on the entire component. Only the additives at the surface of the
material are affected, so it's easier and also speeds up the entire
process."
Professor Boyer says the new technology could potentially be used in a range
of applications where advanced 3D printed materials are currently used in
high-tech specialized components.
These include wearable electronics, sensors, and even some shoe
manufacturing.
Reference:
Zhiheng Zhang et al, A Photoinduced Dual‐Wavelength Approach for 3D Printing
and Self‐Healing of Thermosetting Materials, Angewandte Chemie International
Edition (2021).
DOI: 10.1002/anie.202114111
Tags:
Chemistry