Lightweight battery concept based on VESTALITE® S curing agent

High voltage battery housing for more lightweight and cost-effective e-mobility developed by Evonik and partners

Vestalite S for high-performance epoxy SMC

SMC (Sheet Moulding Compound) is a well-established composite technology for the production of semi- and non-structural components. It distinguishes itself by robust and cost-efficient production, allowing for a high complexity of design and functional integration in composite parts.

The production of SMC material begins with applying a resin onto a carrier foil and then covering it with chopped fibers. After that, a second carrier foil coated with resin is placed on top. The SMC material is then conveyed to several rollers to help to impregnate the fibers before finally being rolled up. The material is stored at ambient temperature or slightly above for several days until it is matured. In a second step, which can be up to several weeks later, the matured SMC is cut into stripes, stacked, and placed into a heated mold. The mold is then closed, and the SMC material is pressed into the intended shape and is cured within a few minutes.

The thermoset resin systems predominantly applied for these processes are unsaturated polyesters, which offer easy processing and fast curing. When improved mechanical properties and chemical resistance are demanded, vinylester systems are the preferred choice. However, the moderate mechanical properties and regulations on VOC are distinct disadvantages of choosing vinylester systems.

To address the needs of delivering high mechanical properties and low VOC values with good processability, Evonik developed a series of amine-based curing agents for epoxy SMC, and its Vestalite® S 101 is the standard hardener recommended for epoxy SMC. In combination with standard epoxy resins, Vestalite® S 101 leads to a low mixing viscosity which allows for excellent fiber impregnation and high fiber fractions for high mechanical properties. SMC material based on Vestalite® S 101 can be matured at room temperature, while remaining stable in the B-stage for several weeks. At the same time, the material can be cured within 4-5 minutes thus contributing to even high efficiency.

Vestalite® S 102 is a modified version of Vestalite® S 101, which by combining it with an additional catalyst like Curezol® 2MZ Azine, speeds up curing time to just 3-4 minutes.

The product portfolio of amine-based hardeners for epoxy SMC has recently been extended with the addition of Vestalite® S 103, which allows for the same advantages mentioned before, but can reach a much higher Tg for special applications, where high thermostability is needed.

All Vestalite® S grades are compatible with different epoxy resins and additives like release agents, standard fillers and flame retardants. Therefore, Vestalite® S grades are highly recommended for all SMC applications. More detailed information of these new curing agents can be found in the table below as well as in the respective technical data sheets.

Evonik’s portfolio of hardeners for epoxy SMC

Unit

Vestalite® S 101

Vestalite® S 102

Vestalite® S 103

Initial viscosity

mPa*s

~20

~10

<200

Use level

PHR

25.3

25.4

20

Initial mixing viscosity

mPa*s

~1000*

~600**

~800***

Tg

°C

120

120

170

*at 30°C, with bisA epoxy resin (EEW 190)
**at 30°C, with bisA epoxy resin (EEW 180)
***at 40°C, with bisA epoxy resin (EEW 180)

Benefits at a Glance

  • Based on type 21700 cylindrical cells
  • Among the industry leaders in battery performance
  • Up to 160 Wh/kg (pack level)
  • Fulfills legal requirements with sustaining 800 °C for at least 10 minutes
  • Reliable in the harshest environmental conditions
  • Immersion cooling technology greatly improves electrical performance
  • 10 % lighter than comparable SMC standard materials
  • Impact rating 3x greater than min. EU safety requirements
  • Improved strength and stiffness of indivdual parts increases overal strength
  • Scalable tooling – configurations for 65, 85 and 120 kWh
  • Integral design / less assembly
  • Cost-efficient up to > 100.000 p/a – one tooling
  • Fully developed recycling and up-cycling concept
  • Vestalite® S based Lorenz Epoxy-GF-SMC reduces the CO2-footprint
  • Module accessibility due to detachable connection concept
  • Highly customizable battery units for complex geometries
  • Novel tooling concept
  • Production flexibility means various casing sizes are possible