Polyurethane Intermediates for Electrical Vehicle (EV) Material Systems

The worldwide adoption of electric and hybrid vehicles and associated technological innovations are driving the need for specialized materials that can meet the unique challenges of EV components.  Resins used in EV construction include polyurethanes, epoxies, unsaturated polyesters, and silicones systems.  Polyurethanes have the dominant share of this resin market segment because of their key product properties such as excellent thermal profiles, high flexibility, resiliency and vibration resistance, excellent tensile properties, superior adhesive properties, chemical and abrasion resistance, and durability.  Polyurethanes also offer processing versatility in assembly of EV components.  A CAGR’s of 15-20% has been projected for polyurethane materials in this market.

The broad capabilities of polyurethanes help to reduce the overall weight of electric vehicles to enhance electric efficiency, extend vehicle range, and improve safety.  The superior bonding properties of polyurethanes allow joining of dissimilar lightweight materials such as polymer composites, fiber reinforced polymers, low surface energy plastics, aluminum alloys and other metals.
The automotive industry’s commitment to overall greenhouse gas emission reductions represents an additional challenge that can be addressed with polyurethanes.  (Note that Gantrade also offers a standard bisphenol A diglycidyl ether (BADGE) epoxy resin that has a bio-content of 27%.)

Applications of polyurethanes in EV battery systems include the following:

• Potting, encapsulation and gap fillers around battery cells
• Adhesives for battery boxes
• Thermally conductive adhesive formulations used in thermal    management
• Systems for bonding battery cells to thermally conductive plates
• Mechanical impact and vibration protection; battery pads
• Battery enclosures
  
  

Attributes of High-Performance Polyether and Polycaprolactone Polyols

With their exceptional versatility and performance characteristics, polyurethanes have gained significant adoption in EV applications. Advantages afforded by polyurethanes include:

• Superior strength-to-weight ratios
• Durability and resistance to wear, abrasion, impact and vibration
• Oil, chemical, moisture, and corrosion resistance
• Good adhesive characteristics
• Performance over extreme low and high temperature ranges
• Processing and design versatility
• Potential to reduce the Product Carbon Footprint (PCF) of EV components

The soft segment of polyurethanes has a dominant effect on the performance parameters of polyurethane systems.  The table below summarizes the relative performance of three generic classes of polyols used in polyurethane elastomers: polycaprolactones, adipate polyesters and polytetramethylene ether glycols (PTMEG).  The designation of “Best-in-Class” refers to the highest performance within these three classes.  The chart can assist the formulator in the selection of the best soft block class of polyols for EV material applications.  The polycaprolactone and the PTMEG polyols represent the highest performance profiles of the polyol classes, while also exhibiting benefits against polyurethane processing requirements for EV materials.  The low acid values, low polydispersity’s and low viscosities of the polycaprolactone and PTMEG polyols afford numerous advantages over the general purpose adipate polyester polyols.

Property Profiles of Polyurethane Elastomers vs. Polyol Type

Liquid Polyols for EV Polyurethane Systems

The table below shows representative liquid, low viscosity polyols in Gantrade’s portfolio that are recommended for high-performing EV urethane systems.  This includes select Placcel® polycaprolactone polyols, PTMEG polyols, ECOTRION® trimethylene ether glycol (PO3G) polyols and a specialty polyester polyol, CA-D620SZX.

These RT liquid polyols offer the combination of low viscosity, good handling characteristics, and filler compatibility required in EV materials. In polyurethanes, they enhance adhesive strengths, flexibility and resiliency, thermal properties, hydrolytic stability and durability.  EV technologies can benefit from the substitution of these polyols in polyurethane systems vs. lower performing alternatives such as polyurethanes based on PPG polyether polyols and general-purpose polyester polyols.  Isocyanates used include methylene diisocyanates (MDIs), hexamethylene diisocyanates (HDIs) and other aliphatic diisocyanates.

Liquid High-Performance Polyols for EV Polyurethane Materials

Placcel 204B enables high filler loadings, up to 80 weight % alumina, and shows excellent adhesion to various substrates.  A Placcel 204B system based on HDI/HDI trimer (55:45) with an NCO/OH ratio of 1.05 exhibited excellent shear adhesion values for Al/Al (4.8 MPa) and Al/PET (2.5 MPa).  HDI/HDI trimer systems based on Placcel 205 exhibit lower crystallinity and more flexible polyurethanes.

The 100% bio-based PO3G polyether polyols further address the automotive industries’ commitment to reduce the Greenhouse Gas Emissions of materials used in vehicles.  The performance characteristics of the PO3G-based polyurethanes are very similar to the characteristics of the PTMEG-based polyurethanes. 

The chart below shows the lower GHG emissions of Gantrade’s PTMEG polyols based on our low emissions petrochemical source vs. PTMEG from a conventional coal based 1,4-butanediol feedstock process used in Asia.  PTMEG produced in the Dairen propylene feedstock process exhibits 75% lower GHG emissions compared with the coal-based BDO acetylene route to PTMEG.  The GHG emissions profile for Gantrade’s PTMEG compares favorably with PTMEG based on a bio-fermentation source for the feedstock butanediol.  The GHG emissions for PO3G from a bio-fermentation feedstock,1,3-propanediol, exhibits the lowest emissions profile of the polyether polyols shown.

Greenhouse Gas Emissions for PTMEG & PO3G from Various BDO or PDO Feedstock Sources

The RT liquid green diol, CA-D620SZX, from Gantrade’s portfolio of bio-based polyester polyols is based on 1,10-decanedioic acid. This co-polyester polyol is hydrophobic in nature with excellent hydrolytic stability.  In polyurethanes CA-D620SZX displays excellent stability in a wet environment along with the general performance attributes of polyester-based polyurethane elastomers.  The bio-content of CA-D620SZX is 83%.

PTMEG vs. Polycaprolactone Polyols in Polyurethanes

The spider diagram below compares the different attributes of the PTMEG and PCL polyols in a polyurethane elastomer.  PTMEG polyols can also be blended with certain polycaprolactone polyols to afford miscible systems.  The most significant enhancements for the polyol blends include flex fatigue resistance, cold hardening resistance and tensile strength, while maintaining excellent mechanical properties over a wider temperature range.

Key Performance Indicators of PTMEG, PCL and Blends in PURs:

PO3G vs. PTMEG Polyols in Polyurethanes

To provide an indication of the performance attributes of our ECOTRION PO3G, the properties of 100% bio-based PO3G based polyurethanes are compared against PTMEG counterparts in the table below.  The MW grades of the polyols are 650 and 1000 in an MDI/BDO system.

H. Sunkara and C. Demarest, Volume 315 of PMA papers: Polyurethane Manufacturers Association, 2010.

PO3G polyols are available in three liquid molecular weight grades, H600, H1000 and H2000.  In addition to being derived from plant-based fermentation processes with low GHG emission profiles, PO3G exhibits several handling and processing advantages in polyurethanes, as follows:

• ECOTRION PO3G polyols are liquids at room temperature.  The melting points against PTMEG polyols are listed in an above table.
• Mw/Mn’s are narrow, ~1.5-1.7, resulting 45-65% lower viscosities vs. PTMEG.  The relative viscosities are listed in an above table.

PO3G polyurethane elastomers exhibit a lower strain induced crystallization response in the soft segment under elastic deformation.  The elongation at break of the PO3G PUR (Shore A Durometer 78) occurs at ~ 950%, which is about 50% higher than the value of a PTMEG 2000 PUR. The increased area under the stress – strain curve translates to higher toughness in the polyurethane elastomer.

Summary

Electric and hybrid vehicles require advanced materials to meet engineering and consumer requirements for lower weight, durability, power efficiency, and quiet operations.  Polyurethanes are helping to address the EV material requirements based on their key product properties such as excellent thermal profiles, high flexibility, resiliency and vibration resistance, excellent tensile properties, superior adhesive properties, chemical, hydrolytic and abrasion resistance, and durability.  Because of their processing versatility, polyurethanes are well suited to the myriad of assembly processes used in EVs. The low viscosities and high filler compatibility allow the incorporation of unique additives incorporated in EV materials, such as thermally conductive compounds.

Gantrade offers an extensive product line of high-performance polyols that enhance the performance of polyurethane systems to replace lower performing materials.  These low viscosity, liquid polyols include polycaprolactone polyols, PTMEG polyols, 100% bio-based PO3G polyether polyols and unique bio-based polyester polyols.

The PO3G polyether polyols and sebacic acid based polyester polyols are a part of Gantrade’s bio-based polyurethane intermediates platform that addresses sustainability initiatives and the reduction in GHG emissions. The performance characteristics of PO3G-based polyurethanes are very similar to the characteristics of PTMEG-based polyurethanes. Our sebacic acid based liquid polyols provide advances in hydrolytic stability, decreased water absorption, chemical resistance and high tensile properties of polyester polyols.  Together, our bio-based urethane intermediates platform helps to enable a sustainable, energy efficient future.

To explore which polyol is best suited for your unique needs, partner with Gantrade. We are a global leader in the distribution of high-performance polyols for a variety of performance enhancements within multiple industry applications. Our team’s wealth of technical knowledge and expertise, along with our uncompromising standards for customer service, ensure that you will receive the best polyurethane solutions for applications. Gantrade’s urethane platform of specialty polyols, chain extenders, curatives and MDIs provide a broad range of possibilities to achieve your high-performance polyurethane requirements. Our global supply chain means high-quality chemical products where you need them, when you need them. Contact Gantrade today to learn more.