Page 66 - Plastics News February 2017

Technology
Research team develops high tech fabric - a nano-porous
polyethylene
Scientists at Stanford University have developed a
material that would block the sun’s rays and also allow
venting of body heat. The scientists have described the
new fabric, a nano-porous form of polyethylene, and its
properties in the journal Science. For now, the fabric
has been tested by humans. The scientists carried out a
test in which they wrapped the high-tech fabric around a
device that imitated the response of human skin on a hot
day. The temperature rose by mere 0.8 degrees Celsius.
In the case of the devices covered in cotton or commercially
available polyethylene, the temperature rose by 3.5
degree and 2.9 degree. The new fabric is so cool that if a
person would wear a shirt and hat made with it then he
would feel quite good under a shady tree even during a
hot day. MIT nanoengineer Svetlana V. Boriskina said that
the fabric will pave the way for a new era of ‘personalized
cooling’. One day, the material would find its use in the
construction of tents, buildings and vehicles.
The researchers have explained that the material is able
to keep warmth at bay by scattering specific wavelengths
of light Cotton fabric provides a cool-feel, but it also traps
body heat inside the garment. Such is not the case with
nano-porous polyethylene fabric. Majority of the heat
that radiates off human body at normal skin temperature
is in the infrared portion of the light spectrum. In lab
tests, cotton permitted only 1.5% of the longer infrared
wavelengths to pass through. The actual need is of
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the fabric that is transparent to infrared radiation and
is opaque to wavelengths of visible light. The nano-
polyethylene fabric reflected 99% of visible light. In
nature, Saharan silver ants keep themselves cool this way.
Multifunctional thermoplastic
composite of buckypaper
framework and Parmax
Two researchers from the United States have created a
series of flattened-nanotube reinforced thermoplastic
composites, which have been fabricated as a function
of buckypaper loading. The researchers incorporated
a Parmax polymer resin, to increase and optimise the
mechanical strength of these composites. The research
is a product of a commercial desire to produce materials
that are multifunctional and lightweight, which can be
incorporated into a wide range of technological and
engineering applications. The researcher’s product is a
multifunctional thermoplastic composite composed of
an aligned buckypaper framework and a self-reinforcing
polyphenylene resin polymer, known commercially as
Parmax. The researchers not only created the composite,
but also optimised the internal composition to produce
a composite with the most beneficial properties. After
testing the mechanical strength, electrical and thermal
properties, alignment, volume fraction and nanotube
length, the researchers deduced the optimal buckypaper
content in the composite to be 60 ± 5 wt%. Such a
ratio was found to produce a tensile strength a Young’s
modulus of 1145 MPa and 151 GPa, respectively. The
composites produced by the researchers are lightweight,
have a high mechanical strength and outperform many
structural/reinforcement materials currently available.
The high reinforcement properties of the composite are
attributed to the strong intermolecular bonds between
the flattened nanotubes and Parmax molecules. There
is a strong network of p-p and p-CH interactions that
facilitates a good dispersion and interfacial stress
transferring- these are two mechanisms that allow for
the effective reinforcement of a composite.