Chemical Engineering March 2014 - 20

Fighting Fungi with plastic
R
esearchers at Singapore's Institute of Bioengineering and Nanotechnology (IBN; Singapore; www.
ibn.a-star.edu.sg), in collaboration with IBM Research Almaden (San Jose, Calif.; www.research.
ibm.com), have discovered that recycled polyethylene terephthalate (PET) can self-assemble into
nanofibers that have fungi-killing capabilities - potentially providing a means of overcoming drugresistant
species of fungi. According to Yi Yan Yang of IBN, PET is a perfect candidate for transformation
into nanofibers, due to its ability to depolymerize using an organic catalyst into cationic compounds possessing
both a rigid structural motif and hydrogen-bonding acceptors and donors. " This unique combination
is ideal to generate nanofibers through self-assembly. Our nanofibers can be easily functionalized
with cationic charges to target microbes, " Yang explains. Post-consumer PET from bottles and packaging
has been used in the research, with Yang stating that even colored bottles can be used, since the dyes
are filtered out. The process begins with PET flakes in the presence of triazabicyclodecene and 4-aminobenzylamine.
After a series of reactions, the eventual result is the small-molecule cationic compounds
that subsequently assemble into nanofibers when placed in an aqueous solution. These nanofibers are
able to use electrostatic interactions to selectively target fungal cells and kill them by penetrating the cells'
membranes. The selectivity of these compounds sets them apart from existing antifungal agents, some of
which cannot distinguish between fungal cells and mammalian cells and can potentially attack the wrong
cell. The fungal-elimination power of the nanofibers is seen in the side-by-side photos here, comparing
scanning-electron-microscope images of a C. albicans biofilm before (top) and after (bottom) treatment
with the nanofibers. The next step for this discovery is commercialization - IBN and IBM have been collaborating
with several companies to get this technology rolled out to the pharmaceuticals industry. ❑
One solution is found in the
Eco Circle technology (Figure 3)
from Teijin Ltd. (Tokyo, Japan;
www.teijin.co.jp), which recycles
polyester fabrics through a closedloop
proprietary chemical process
- the first of its kind in the world,
says the company. Eco Circle's process
chemically decomposes polyester
and converts it back into polyester.
Also, according to Teijin, the Eco
Circle technology requires less energy
and produces fewer emissions
than producing new polyester fibers
from petroleum.
The main source of waste polyester
for Eco Circle is worn-out
clothing, which is collected by the
over 150 members of Eco Circle's
business network - mainly retail
stores and apparel-producing companies.
What sets Eco Circle apart
is the repeatability of its technology.
Rather than " downcycling " to
lower-quality products, the Eco
Circle process allows for polyester
to be recycled multiple times into
usable textiles, such as uniforms for
factory employees.
In a partnership announced in
December 2013 with Fuji Xerox Co.,
Ltd. (Tokyo; www.fujixerox.com)
and Shanghai's Onward Trading, a
designer and manufacturer of uniforms,
Teijin has applied the Eco
Circle process to provide uniforms
made of recycled polyester to workers
at various Fuji Xerox facilities
in China. Once the uniforms reach
the end of their useful lives, they
will be sent to the new recycling
plant of Zheijiang Jiaren New Materials
Co., a joint venture between
Teijin and the Jinggong Holding
Group that was established in September
2012. When this new recycling
plant starts up later this year,
the polyester recycled there will be
eventually used to again manufacture
uniforms for Fuji Xerox, closing
the loop. The next step for Eco
Circle will be increasing its network
to integrate not just polyester from
fibers and fabrics, but from other
sources, such as plastic bottles
and films.
Post-consumer challenges
Despite the boom in innovative recycling
technologies, concerns loom
on the horizon for both manufacturers
and recyclers. As environmental
regulations continue to tighten,
new developments in bio-sourced
and degradable chemicals are coming
to the forefront and changing
the landscape of polymer processing.
The APR has published guidelines
related to end-of-life options
for bio-based and degradable plastics,
which in many cases cannot
be processed in the same manner
as conventional plastics. Plastics
Recyclers Europe (PRE; Brussels,
Belgium; www.plasticsrecyclers.eu)
also warns of the concerns related
to the recycling of such materials by
emphasizing that specific end-of-life
solutions must be implemented on a
large scale in order to truly evaluate
the sustainability of manufacturing
these alternative materials.
First, an important distinction
must be made between " bio-based, "
" biodegradable " and " degradable "
materials. Bio-based products in20
ChemiCal engineering www.Che.Com marCh 2014
volve monomers that were originally
sourced from plants or other biological
raw materials. Most bio-based
plastics are physically the same as
their conventional petroleum-based
counterparts (for instance, PE or
PET) - being bio-based doesn't
make them inherently more biodegradable.
Although some bio-based
plastics are biodegradable, recycling
solutions must be developed
for those that are not. European
Bioplastics (Berlin; www.europeanbioplastics.org)
states that bio-based
plastics can be recycled in the same
existing streams as their petroleumbased
analogs, and reiterates that
sorting technologies are sophisticated
enough to prevent entry into
recycling streams of bioplastics for
which there is no existing recycling
process. For those materials, recycling
streams are being researched
and can be implemented at a large
scale once commercial volumes of
bioplastics increase, says European
Bioplastics. The most serious
concerns arise with so-called
oxo-degradable plastics.
An oxo-degradable plastic involves
special additives that contribute
to its breakdown, usually
via a triggered chemical reaction.
When present in batches of traditional
plastics intended for recycling,
materials with these additives
can create issues in recycling
processes, if the degradation reaction
is triggered, and can also compromise
the service-life integrity of
recycled end products. According to
the European Plastic Converters
(Brussels Belgium; www.plastic

http://ibn.a-star.edu.sg http://www.research http://www.ibm.com http://www.teijin.co.jp http://www.european http://www.bioplastics.org http://www.fujixerox.com http://www.plasticsrecyclers.eu http://www.plastic http://www.Che.Com

Chemical Engineering March 2014

Table of Contents for the Digital Edition of Chemical Engineering March 2014