Page 50 - Plastics News June 2021

teChnoLogy

From milk protein, a plastic foam Fluorescent polymer that helps

that gets better create high contrast images

new high-performance esearchers have developed a fluorescent polymer
A plastic foam developed from Rthat binds to blood in a fingerprint without
whey proteins can withstand damaging any DNA also on the surface to create high-
extreme heat better than many contrast images. Fingerprints are critical pieces of
common thermoplastics made forensic evidence because their whorls, loops and
from petroleum. A research arches are unique to each person, and these patterns
team at KTH Royal Institute don't change as people age. When violent crimes are
of Technology reports that the
material, which may be used committed, a culprit's fingerprints inked in blood can
for example in catalysts for be hard to see, especially if they tried to clean the
cars, fuel filters or packaging scene and at times dyes are used to reveal this type
foam, actually improves its of evidence, Fluorescent compounds can enhance the
contrast between fingerprints and the surface on which
they are deposited. However, to get a good and stable
image, these molecules need to form strong bonds
with molecules in the blood., Li-Juan Fan, Rongliang
Ma and colleagues have found a simple way to bind a
fluorescent polymer to blood proteins so that they could
detect clear fingerprints on many different surfaces.
The researchers modified a yellow-green fluorescent
polymer they had previously developed by adding a
second amino group, which allowed stable bonds to
form between the polymer and blood serum albumin
mechanical performance after days of exposure to high proteins. They dissolved the polymer and absorbed
temperatures. The basic building blocks of the material it into a cotton pad, which was placed on top of
are protein nanofibrils, or PNFs, which are self-assembled prints made with
from hydrolyzed whey proteins—a product from cheese- chicken blood
processing—under specific temperature and pH conditions. o n var io us
In tests the foams improved with aging. After one month of surfaces, such as
exposure to a temperature of 150C, the material became aluminum foil,
stiffer, tougher and stronger, says the study’s co-author, multicolored
Mikael Hedenqvist, professor in the Division of Polymeric plast ic an d
Materials at KTH. “This material only gets stronger with painted wood.
time,” he says. “If we compare with petroleum-based, Af ter a f ew
commercial foam materials made of polyethylene and
polystyrene, they melt instantly and decompose under minutes, they
the same harsh conditions.” The material proved water- peeled off the
resistant after the aging process, which polymerized the pad, and then
protein, creating new covalent bonds that stabilized let it air-dry. All of the surfaces showed high contrast
the foams. The foam also resisted even more aggressive between the blood and background under blue-violet
substances—such as surfactants and reducing agents —that light and revealed details, including ridge endings,
normally decompose or dissolve proteins. The crosslinking short ridges, whorls and sweat pores. These intricate
also made the foam unaffected by diesel fuel or hot oil. patterns were distinguishable when the researchers
The material also showed better fire resistance than contaminated the prints with mold and dust, and they
commonly used polyurethane thermoset. lasted for at least 600 days in storage.

Plastics News June 2021 50