i+D - September/October 2018 - 42

Making Use of Every Molecule - By Emileigh Clare and Todd Sims

Greener, Bio-based Carpet
For more than 200 years, DuPont has been developing
innovative chemistry. One of its key research areas: bio-based
products used in applications ranging from carpet, to apparel,
to packaging, and more. The focus of this work remains the
same across all applications-to create new technology that
has a better sustainability profile than certain nonrenewable
alternatives, without sacrificing performance attributes.
Today, some of the soft and resilient carpets in the marketplace
come from a long-term DuPont research initiative. It started
back in the 1950s, when DuPont scientists marveled over the
unique properties of a close "cousin" of nylon, a new chemical
compound they called "poly trimethylene terephthalate"(PTT).
According to DuPont's Michael A. Saltzberg, PhD, global
business director of biomaterials at DuPont Industrial Biosciences,
the scientists knew they had found something special, just by
PTT's microscopic structure. Up close, it looked like a fishing
hook or the letter "J."
"Scientists knew it was a cool molecule," says Saltzberg.
"They could tell that it would be as resilient as nylon,
sometimes even better, based on that shape. And, also
because of the nature of PTT's chemical structure, they found
that the shape repelled dirt and had built-in stain resistance
[and could] offer more stain resistance naturally than other
materials, like nylon, polyester, and polypropylene, that are
also used to make carpet, for example. There was also an
inherent stretchiness in the compound, which could be used
to make very soft and resilient fibers."
However, one major issue resulted from scaling up PTT for
uses outside the lab. PTT had to be created from two different
chemicals, terephthalic acid (PTA) and propanediol (PDO).
At the time, PTA was widely available to make a variety of
polyesters, but PDO was more difficult to scale for commercial
uses. For that reason, PTT could not be made available on
the market at a reasonable cost.
The science was temporarily put on hold, but not forgotten.
In the mid- to late-1980s, DuPont started investing in a new
type of science called industrial biotechnology. Saltzberg
describes this as biotechology focused in the areas of
chemicals, materials, and fuels, which are key aspects of the
green chemistry movement. "Our team working in industrial
biotechnology determined that making the molecule PDO
with a fermentation process using plant-based resources-
very similar to how you make beer or wine, for example-
was exactly the process we could use," recalls Saltzberg.

Michael A. Saltzberg, PhD,
DuPont Industrial Biosciences
(Image: DuPont)

42

For about 10 years, DuPont scientists worked on modifying
microorganisms to create the new bio-based PDO that would
ultimately make the bio-based co-polymer Sorona. At times,
hundreds of people and scientists worked on this project,
according to Saltzberg. In fact, the program to develop a
bio-based route to PDO and the Sorona co-polymer was one
of the largest R&D programs for the company at the time.
In 2003, the U.S. Environmental Protection Agency (EPA)
presented DuPont Sorona with its Presidential Green
Chemistry Challenge award, which acknowledges chemical
technologies that "incorporate the principles of green chemistry
into chemical design, manufacture, and use." By 2006, Sorona,
comprised of 37 percent PDO, was creating soft, stain-resistant
carpets from renewable sources and the innovative science
behind it still is garnering acclaim. In 2017, Frost & Sullivan
named DuPont Industrial Biosciences the Bio-based Materials
Company of the Year for its continued research and innovation
in the biomaterials space.
"It's really groundbreaking science to make a product
like Sorona. At DuPont, we focus on new sustainable
approaches that maximize the use of renewable resources,"
notes Saltzberg. "It's just the way we do chemistry."
Over the past 12 years, DuPont and Mohawk Industries
scientists have teamed up in an exclusive partnership to
take the chemistry of carpets even further. As part of their
partnership, Mohawk has created new product lines using
DuPont chemistry, such as "SmartStrand," in which each
strand of carpet is packed with 700 silk-like, stain-resistant
fibers to provide incredible durability and softness. In addition,
both DuPont and Mohawk R&D teams have continuously
found ways to lower the environmental impact of Sorona
and the products made from it.

DuPont's Sorona co-polymer is used
to create soft, stain-resistant carpets.
(Image: DuPont)
i+D - September/October 2018

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