Issue 01/2021

Foam
Biobased open-cell
PU foam
Achieving sustainability in product design can be
challenging when not all biobased materials and
sustainable plastic product development processes are
created equal. Manufacturers should not have to sacrifice
the quality of their products to create more sustainable
offerings. When designing components with porous polymers,
manufacturers can achieve high-quality material solutions
using biobased, recycled, or biodegradable plastics, replacing
porous components made from single-use plastics. However,
it’s critical to understand the various technical considerations
for porous polymers based on technology and functionality in
order to explain how best to design with sustainability in mind.
Creating a durable, more sustainable product
with biobased polyurethanes
One of the main technology platforms used to manufacture
porous polymers is a two-step open-cell foam manufacturing
process. Open-cell foam technology is developed using
proprietary or customized blends of raw materials through a
clean polyurethane foaming process without the use of catalysts.
Different formulations offer wide-ranging densities, porosities,
and levels of softness to meet specific customer requirements.
This unique technology is made using a highly specialized
manufacturing process and can be found in many applications.
These porous materials are then assembled into the end product
– such as a cosmetic product, a medical-grade foam for wound
dressing for burns (see picture), or a patient positioning device
used in hospitals. While biobased polyurethane might not be
more recyclable than traditional polyurethane, it can be used in
open-cell foam to lessen the final product’s dependence on fossil
fuels and replace some of the ingredients in the pre-polymer with
biobased urethanes to create a largely bioplastic-based solution.
Unlike conventional polyurethane foam, open-cell polyurethane
foam is hydrophilic and can absorb (e.g.) water up to 15 to 20 times
its weight. Open-cell foam is also a hypoallergenic material that
is non-crumbling, latex-free, and customizable in color. Additive
ingredients can be included to help create product differentiation.
In biomedical applications, open-cell foam can be used as an
antimicrobial medical foam that better absorbs fluids during use,
allowing the wound dressing to last longer and be fully used before
disposal. Because of its flexible porous structure, open-cell foam
can be used for cosmetics to make applicators more durable and
effective to minimize waste in the overall product lifespan. That
said, in order to ensure that the open-cell foam component will
perform as desired with a product, it must be custom-engineered
and manufactured to the right specifications.
Not the typical manufacturing process
Polyurethane foam can be manufactured in two different ways.
The more traditional manufacturing process consists of one step
and is used for large-scale manufacturing of foam used in items
like seat cushions, bedding, or other similar goods. The one-shot
process creates a large bun of foam by simultaneously mixing all
ingredients at one time. The one-shot terminology comes from
the process of all ingredients being combined into a conveyor or a
mold, where the chemicals are simultaneously reacting with each
other and immediately creating the foam expansion. This often
By:
Avi Robbins, Vice President
Global Product Development and R&D
Porex
Fairburn, USA
includes the addition of harsh chemicals or catalysts to create the
foaming reaction.
However, when looking at smaller-scale applications that
require more control over pore size, pore structure, and overall
foam characteristics, a more unique two-step process is needed.
Instead of using chemical agents to create the reaction and
catalysts, this process uses a large amount of water to react with
the pre-polymer formulation.
By taking the proper ratio of pre-polymer and pairing it with a
water-based solution, a chemical reaction can begin that creates
carbon dioxide gas. The presence of this gas, in turn, spurs
foaming action and creates the pore structure of the foam. This
process provides the ability to control the chemical reaction and
the ingredients to manipulate pore size, pore structure and, finally,
the properties of the foam. Ultimately, this control allows resulting
open-cell foam structure to better support the end product’s
functional specifications.
Partnering with an innovative supplier
Open-cell foam is custom engineered to the end product’s
requirements. For example, a wound dressing manufacturer
can specify and develop a foam with pore structure built for high
absorption capacity, helping to withdraw the exudate from the
wound and provide a more sanitary, comfortable, and effective
treatment. In a cosmetics application, manufacturers can take the
same approach of tailoring foam pore structure to optimize flowthrough
for viscous cosmetics formulations, enabling uniform
coverage and consistent product performance. Understanding
the nuances between these types of product segments and the
pore structures their material components require is critical for
achieving a successful product design. When working toward
a more sustainable product and involving a supplier to provide
biobased polyurethane, it is key that the partner holds material
expertise to help guide the manufacturing process and ensure
design optimization.
Porex, a global leader in porous polymer solutions, can
recommend different materials to achieve the ideal open-cell foam
component. This collaborative effort enables Porex to pinpoint the
proper chemical formulation and manufacturing process to yield a
foam equipped with the right properties for the end-product.
When consumers invest in a more sustainable product, they
expect the same quality as the alternative, traditional product. As
more manufacturers venture out to create these eco-friendly goods
with biobased polyurethane, seeking the ideal expert partner is
essential. By taking a strategic, tested approach to material design
and production, manufacturers can enhance their own sustainability
credentials while
upholding existing
performance
standards –
building customer
loyalty and market
differentiation.
www.porex.com
34 bioplastics MAGAZINE [01/21] Vol. 16