STEEL-STRENGTH PLASTIC
University of Michigan researchers have created a composite plastic
that's as
strong as steel but lighter and transparent. The composite plastic is
made of
layers of clay nanosheets and a water-soluble, glue-like polymer. UM
engineering
professor Nicholas Kotov and others have solved a problem that has
confounded
engineers and scientists for decades: individual nano-size building
blocks such
as nanotubes, nanosheets, and nanorods are ultrastrong, but larger
materials
made out of bonded nano-size building blocks were comparatively weak.
The UM researchers created the composite plastic with a robotic machine
that
builds materials one nanoscale layer after another. In this experiment,
the
machine's arm held a piece of glass about the size of a stick of gum on
which it
built the new material. The arm dipped the glass into the glue-like
polymer
solution and then into a liquid that was a dispersion of clay
nanosheets. It
took 300 layers of each of the polymer and the nanosheets to create a
piece of
this material as thick as a piece of plastic wrap.
The polymer used in the experiment, polyvinyl alcohol, was as important
as the
layer-by-layer assembly process. The structure of the "nanoglue" and
the clay
nanosheets allowed the layers to form cooperative hydrogen bonds,
causing "the
Velcro effect." If such bonds are broken, they can easily reform in a
new place.
The composite plastic could be used in microelectromechanical devices,
microfluids, biomedical sensors and valves, and unmanned aircraft.
Find out more at:
http://link.abpi.net/l.php?20071018A2=============================================================
NON-STICK GUM
About 600,000 metric tons of chewing gum are manufactured yearly.
Inevitably, a
large percentage ends up on streets and pavements and results in a
pollution
issue. London spends an estimated two million pounds - over four
million dollars -
every year to clean gum from subway trains and stations. A new gum
created by
the U.K.-based company Revolymer tackles this issue, easily coming off
roads,
shoes, and hair.
The main ingredient in most chewing gums is a gum base: a mix of
synthetic
petroleum-derived polymers, natural latex, resins, and waxes. All of
these
components are hydrophobic, meaning they stay away from water and are
attracted
to oil. This is why gum traditionally sticks to the grease and grime on
sidewalks. The Revolymer gum base has polymers with a hydrophobic part
that's
wrapped inside a hydrophilic, or water-attracting, part. So even though
the gum
sticks to a surface, a film of water can form around it so that it
easily washes
away with water.
The new gum performed well in tests. When stuck on sidewalks, rainwater
or
street cleaning washed it off within 24 hours. Tests also showed that
when
Revolymer's gum was stirred into water, it disintegrated completely in
eight
weeks, which means it could degrade once it goes into a drain. The gum
also did
well in blind taste tests, though the texture is slightly softer
because the
hydrophilic polymer interacts with saliva. Revolymer plans to launch
the gum in
three different flavors next year.
Read the full story at:
http://link.abpi.net/l.php?20071018A10
