Renewably Sourced Automotive Interior Materials

Renewably Sourced Automotive Interior Materials | DuPont Automotive

DuPont renewably sourced automotive interior materials can be used to help automakers differentiate their brands and support sustainability objectives. These materials are made in part with annually renewable plant based ingredients.

These materials also provide cost savings and improved performance versus the petroleum-based products they are replacing.   

The DuPont portfolio of renewably sourced automotive interior materials includes:  

DuPont™ Sorona® Polymer

Sorona® is the DuPont brand name for renewably sourced PTT (polytrimethylene terephthalate). It is made from the poly-condensation reaction between a glycol and either an acid or an ester.  
In the case of Sorona® polymer, the glycol is 1,3 propanediol, which is derived from the fermentation of plant sugar. Currently the feedstock is corn sugar.

The polymerization proceeds without a heavy metal catalyst that is typical of PET. The resulting polymer contains 37 percent, by weight, renewably sourced material and – as compared to PET– has an extra carbon in its backbone. The extra carbon changes the morphology of the polymer, resulting in distinctly different properties, such as good stretch and recovery and nylon-like aesthetics in fiber and fabric form.
Sorona® fibers meet strict performance requirements for automotive use while having rich and soft texture as well as good hand-feel.

Compared to nylon 6, which is commonly used in auto interior applications, the production of Sorona® yields environmental benefits of 63% reduction in greenhouse gas emissions and 30% reduction in energy use.

The bending modulus of Sorona® polymer is about four times lower than PET and 20 percent lower than PA66, which translates into softer, “drapey” fabrics.

The advantages to using Sorona® fiber  in automotive carpeting:  

  •   Improved stain resistance vs. PA66
  •   Lower temperature dyeing vs. PET and better wash fastness
  •   Significantly better crush resistance and durability vs. PET
  •   Superior softness to both PA66 and PET
  •   More resistant to mold and mildew

DuPont Sorona® Used in the Ecofriendly, Luxury Toyota SAI

DuPont™ Sorona® was chosen as the material for the ceiling surface skin, sun visor and pillar garnish of Toyota’s new model, SAI®, currently available in Japan.

Strength and Stiffness Comparison

The Toyota SAI® is an intensively ecological “compact luxury car” equipped with renewably sourced automotive interior materials including eco-plastics made from plant-based materials that comprise approximately 60 percent of the car’s internal surface area. Sixty percent of the interior fabrics use DuPont Sorona®.

DuPont Sorona® EP Polymer

In addition to fiber applications, Sorona® is also designed for use in injection molding applications.

Sorona® EP (polytrimethylene terephthalate)  is stronger and stiffer with slightly lower elongation than PBT. PTT has a much better surface appearance, especially with high glass loadings. It also has slightly lower shrinkage along with lower warpage, which is an important benefit for many electrical/electronic parts that have dimensional tolerance challenges.

Sorona® EP polymer can be used to replace interior parts that are painted, such as vent louvers. Since the louver blades need to be very thin so as not to impede air flow, they typically have high glass loadings – up to 45 percent – to make them stiff and strong. The high glass content negatively affects the surface finish, so louvers are painted.  

Due to the better surface finish of Sorona® EP compared to glass-reinforced materials, you can lower costs by eliminating the paint operation and avoid the VOC (volatile organic compound) emissions associated with painting.
DuPont Hytrel® RS Thermoplastic Elastomer

Hytrel® RS elastomer is a bio-based polymer derived from the Hytrel® TCP/ET product line.

The renewably sourced family is nearly identical in its physical properties and performance to its non-bio-based polymer.

Hytrel® RS thermoplastic elastomer shares many of the same physical characteristics as Hytrel® TCP/ET:

  •    Excellent elasticity
  •    Low-temperature flexibility
  •    High flex life over millions of cycles
  •    Very high chemical resistance to oils and greases

The bio-based content of Hytrel® RS thermoplastic elastomer can vary from 20 to 60 percent, depending on the grade. Since Hytrel® TCP/ET is comprised of a hard segment (for strength) and a soft segment (for flexibility) and is available in a wide range of grades, the ratio of hard and soft segments varies. In Hytrel® RS, the bio-portion is the soft segment. So the softer, more flexible grades have a higher bio-portion than the harder grades.

For example, DuPont Hytrel® RS for use in airbag systems contains a minimum of 35 percent renewable content by weight derived from non-food biomass. This makes it one of the industry’s first sustainable airbag systems, developed in a joint venture with Takata-Petri of Aschaffenburg, Germany.

These products are just the beginning. DuPont has a large R&D effort underway to bring more renewably sourced automotive interior materials to the market. With our broad materials expertise, we welcome the opportunity to collaborate with automakers and OEMs on specific material performance needs.