More than six in 10 American design engineers say they will
consider use of plastics made from renewable resources in the next five years.
That's a huge shift from current practice: less than 10 percent
of design engineers currently use plastics made from plants or algae.
Those data points are just a
few of the results from a Design News survey addressing the use of bioplastics, which
are increasingly competing directly with plastics made from oil and natural
gas, particularly for packaging and disposable products.
Somewhat surprisingly, the biggest attraction of these materials to design engineers is not environmental. It's the desire to reduce American dependence
on imported petroleum.
"I think that (bioplastics) is
the future," says Charlie Putland, a senior mechanical engineer for a company
that designs machine tool enclosures. "Petroleum supplies will eventually be
depleted and will continue to climb in price for as long as it is still
available. Add to that more stringent environmental
regulations (RoHS et al); bioplastics are ever-more important."
The second biggest attraction of bioplastics is an environmental
aspect - but not the one typically pitched by producers of the materials.
Four in 10 respondents to the survey said they will use
bioplastics because they reduce greenhouse gases. As plants grow, they
sequester carbon dioxide, which is later released when the plastics are
incinerated or decompose. ?As
a result, they are said to have a neutral effect from a climate change
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Oil-based plastics, on the other hand, only release carbon
dioxide. Their carbon dioxide
sequestration phase took place in primordial times.
For every 100 kg of polypropylene or polyethylene manufactured
using "biocarbon" (such as starch or polylactic acid) as opposed to fossil
fuel-based carbon, 320 kg of carbon dioxide
emissions reduction are achieved in an "intrinsic" analysis, according to
Ramani Narayan, a professor of material science and chemical engineering at
Michigan State University.
In an intrinsic analysis (spelled out in ASTM D6866), the
reduction achieved is equal to the amount of biocarbon content in the
Some design engineers, however, say that it's still not
clear what impact bioplastics have on climate change.
"Renewables work only if performance is comparable and the
‘cradle-to- grave' environmental impact is less than more conventional
materials," says David Hutchison, a manager of mechanical engineering for a
manufacturer of camping equipment. "I
see too narrow a vision used when assessing the impact of alternate materials
like the increased use of non-renewables to produce renewables."
He raises the point that the oil used to grow and harvest crops
and then transport them to processing locations may outweigh any benefit
derived from the carbon dioxide sequestration when the plant is growing. ?A similar
debate has surrounded biofuels such as ethanol.
Narayan and others worked to
develop American and global standards that measure the "cradle-to-factory-gate"
environmental footprint of bioplastics. That data can now be determined in ASTM
Some environmental advocates
even go farther to demand a "cradle-to-cradle" footprint to determine the total
impact of a material from its origins to its end-of-life or re-use. In that
view, the best materials are those that can be "upcycled" following their use
to a more demanding application. One example could be the use of PET soda
bottles in composites for car parts. Design programs that subscribe to the
"cradle-to-cradle" approach put a high value on recyclability, not
The third biggest benefit of designs that incorporate bioplastics
is not a surprise - it's a good marketing story. That's
clear from the plethora of advertisements touting green virtues in the past 12
months. Some examples:
Stonyfield Farms replaced oil-based polystyrene in its multipack yogurt cups
with polylactic acid (PLA), which is a plastic made from corn and synthetic
- Citing "its heritage as an innovator and leader in environmental
sustainability," PepsiCo announced development of the world's first PET plastic
bottle made from switch grass, pine bark and corn husks. In the future, the
company expects to broaden the renewable sources to include orange peels,
potato peels, oat hulls and other agricultural by-products from its foods
- Papermate introduced a pen last year with components that will biodegrade in
about a year when buried in soil or placed in an industrial compost facility.
The biodegradable components are molded with Mirel, a biodegradable corn-based
bioplastic called üpolyhydroxyalkanoate (PHA).
The biodegradability aspect is an area that's declining in
importance overall and is of less interest to design engineers, who are
generally looking for products with good durability.
Some marketers overplayed the biodegradability card with comments
that were sometimes misleading or even outright incorrect. For example, some
made claims that their bioplastics would degrade in landfills, but landfills
are generally oxygen- and moisture-free to prevent any biodegradation, which
could cause toxic chemicals to leak into aquifers.
Many of the newer bioplastics are not biodegradable at
DuPont, for example, is one of
the leaders in developing engineering polymers that have bioplastic
roots. At K 2010 held in Düsseldorf, Germany last year, DuPont's stand
displayed 10 products made at least in part from bioplastics.
DuPont worked with Takata-Petri of Aschaffenburg, Germany to
develop the industry's first renewably sourced thermoplastic elastomer for use
in airbag systems. The material contains a minimum of 35-percent renewable
content by weight derived from non-food biomass. The newly developed grade of
Hytrel is based on a thermoplastic ether-ester elastomer (TPC-ET) with hard
segments of polybutylene terephthalate and soft segments that contain a
polyether derived from non-food biomass.
DuPont stands alone among the major chemical companies as a
significant investor in multiple bioplastic technologies. Most renewably
sourced materials are being developed by start-ups and technology spin-offs.
"DuPont's strategy is to offer polymers that are at least 20
percent renewably sourced and have equal or better performance than the
entirely petrochemically based materials they replace," says Marsha A. Craig, DuPont's global business
manager for renewably sourced materials.
The company's portfolio keeps
expanding and now includes Sorona EP thermoplastic polymers, which exhibit
molding characteristics similar to high-performance PBT (polybutylene
terephthalate); Hytrel RS thermoplastic elastomers, which contain 35 to 65
percent renewably sourced material and provide the same established performance
characteristics of original Hytrel; and a family of Zytel RS long chain nylons.
One in three design
engineers surveyed say they plan to use bioplastics because of their superior
"(Bioplastics) will only be a good choice if they perform equally
or better than their petroleum-based cousins," says Roger Sharp, a tool
engineer. "We shouldn't be using them simply because they claim to be green."
Most bioplastics have inferior
mechanical properties compared to oil-based plastics, particularly in thermal
resistance. A few, however, have superior, or even unique, property profiles. The engineering properties of
renewably sourced plastics vary widely because of the wide range of biological
materials they are made from.
One interesting example is a
class of polyamides made from castor beans.
In 1942, BASF chemists in Germany invented castor-derived
polyamide 11 and 12, which have different properties from their better-known
polyamide cousins, polyamide 6 and 66. Polyamide 11, sold as Rilsan 11, by
Arkema, offers excellent chemical resistance, as well as impact strength, high
service temperatures and dimensional stability. It's widely used for oil
country umbilical cables, automotive fuel and fluid transfer tubing, and transfusion bags.
Since the "renewable" aspect became a selling point, four other
companies announced development of their own castor-derived polyamides: DuPont,
Rhodia, BASF and Evonik. BASF had lost rights to the material.
In another example, DuPont says its Sorona plastic has improved
surface appearance and lower warpage compared to the PBT-type polyesters it
The extent to which design engineers will make greater
use of bioplastics will depend on a variety of factors, led by cost and
property deficiencies for the most common grades.
In cases where there are clear
choices between petrochemically based plastics and those derived from renewable
resources, there generally is a premium for the latter. And sometimes the
premium is significant.
One example is a class of bioplastics called
polyhydroxoxyalkanoate (PHA). The leading developer is Telles, a joint venture
of Archer Daniels Midland and Metabolix. Its product, trade named Mirel, is
made from corn sugar via a fermentation process at an Iowa biorefinery. Its
price is about 2.5 times higher than ABS, an entry-grade thermoplastic. The
pitch is that it has a better carbon footprint than ABS and is biodegradable.
That type of argument isn't flying with many of the design
"Bioplastics are great if they're competitive on cost and
properties," says one design engineer. "Otherwise they're a waste of money."
Several respondents to the
survey also made comments on the potential impact on food supplies if bioplastics are widely used. CLICK HERE
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"Ethically, I cannot in good conscience recommend the use of
plastics made from food crops," says David E. Palmer, a metallurgist in the Powertrain Div. of Bombardier Recreational Products. "I am also skeptical about the purported environmental
benefits. It is really very dishonest to pretend that carbon dioxide emissions
created in generating the energy needed to convert these crops into plastics is
somehow offset by the carbon dioxide absorbed by the crops - wouldn't that
acreage be planted anyway? That being said, I would potentially be interested
in plastics made from biologically based materials - if they were made from
waste materials, for example."
Palmer's comments reflect a growing consensus among the
public in general. The first
major bioplastics' projects in the U.S. focused on the use of corn. Most new
projects target use of plants not used for food or waste.
For example, Ford Motor, a leader in the use of natural
materials, is studying use of Indian grass that grows wild in Michigan and
elsewhere in the Midwest.
"The big motivation in working on natural fiber is a 30-percent
weight reduction compared to glass fiber," says Dr. Deborah Mielewski, the
leader of a Ford engineering team studying sustainable materials. "Also, glass
fiber takes a lot of energy to produce, and you also get the carbon dioxide
reduction because you're sequestering carbon dioxide in the plant when you grow
Cereplast is developing polymer
compounds made from algae.
Over time, the developers of
plastics made from annually renewable resources will solve many of the
objections they currently face. They will be made from resources that don't
threaten global food supplies. Their properties will improve. They will become
more cost competitive as the price of oil rises. Governments will enact more
laws that address global warming.
Given those factors, the role of bioplastics likely will remain
For example, a study conducted
by BCC Research forecasts that bioplastics will grow at a 41 percent annual
rate through 2015 to reach 3.2 million metric tons, but they will still only
account for about 1 percent of the
global plastics market.