Visualizing stress in plastics

Date:
August 4, 2021
Source:
Chemnitz University of Technology
Summary:
Researchers have developed dyes that continuously translate stress
in plastics by changing color.



FULL STORY ==========================================================================
A research team led by Prof. Dr. Michael Sommer, Professorship of Polymer Chemistry at Chemnitz University of Technology, and PD Dr. Michael
Walter, project leader at the Cluster Of Excellence Living, Adaptive,
and Energy- autonomous Materials Systems (livMatS) at the University of Freiburg, has succeeded in constructing a new dye molecule from the area
of so-called mechanophores.


========================================================================== Thanks to this molecule, stress of different magnitude in plastic
components can be visualized continuously by color changes. The concept
of such dyes is not new, but most previous mechanophores were able to
only indicate the presence or absence of stress in plastics. The current research now enables to differentiate between stresses of different
magnitude. This adds up great advantages whenever it is important to
map stress distributions in macroscopic plastic components to monitor
integrity of the material at all times. The research team is now one
step further to developing this effective form of deformation and damage analysis, bringing it closer to practical applications.

The results of the study were published in the journal Nature
Communications on July 9, 2021.

Molecular spring shows the strength of the load in terms of color As
the researchers report in their publication, by combining a molecularly designed dye with a suitable and, above all, non-brittle plastic,
macroscopic forces can now be brought down to the molecular scale. These
acting forces can be, for example, external pressure or tension.

The dye molecule thus "feels" the force acting within the plastic
components and continues to indicate changes in force by increasing
changes in color. If the external load is taken off, the dye molecule
returns into its original state. This is why this dye is termed
a "molecular spring" -- it stretches and "springs" -- depending on
external tension.

Compared to existing molecular switches that translate stress in plastics
by changing color, the advantages here clearly lie in the stepless
mapping of forces of different magnitudes as well as the spring-like
behavior of the molecule, which can thus be used again and again.

Better mechanical properties -- better understanding and applying damping
"This is a bold step towards directly visualizing external residual
stresses of plastics with simple analytical methods, which is of great
help for the further development of materials with improved mechanical properties made by, for example, 3D printing," summarizes Prof. Michael
Sommer.

But it could also allow a more fundamental understanding of damping
properties of synthetic materials and natural systems: For example,
there are large and heavy fruits that fall from trees from large heights
but remain undamaged.

Nature serves as a model here, and molecular springs could help to better understand and imitate such systems.

Future efforts will therefore focus on adapting molecular force springs
for use in various plastics. This will require joint efforts with other research groups and the use of computer-assisted methods.

========================================================================== Story Source: Materials provided by
Chemnitz_University_of_Technology. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Maximilian Raisch, Wafa Maftuhin, Michael Walter, Michael Sommer. A
mechanochromic donor-acceptor torsional spring. Nature
Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-24501-1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210804123616.htm

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