Towpreg Winding uses a fiber tow that is pre-impregnated with resin (prepreg). It is ideal for making cylindrical and/or hemispheric components. Towpreg material generally has a high filament count, making it a good choice for automotive parts, which require robust mechanical performance at low cost. The main automotive application is pressure vessels for CNG or hydrogen.
Wet Filament Winding is a well-established manufacturing process, but automotive component manufacturers are increasingly turning to Towpreg Winding, which offers increased productivity and greater part consistency. Because towpregs are already impregnated with an optimal and consistent quantity of resin, the additional step of transferring resin to the fibers can be eliminated. Towpregs can be manufactured on site, at speeds up to 100 meters per minute, which mitigates the need for cold transportation and storage.
Glass transition temperature (Tg):
140 - 150°C
Fracture Toughness:
0.9 - 1.1 MPa.m½
Suitable for:
High temperature resistance system designed to satisfy the requirements of hydrogen vessels manufactured via towpreg winding. Very long latency for ease of use, optimized manufacturing viscosity profile and fast curing for high productivity.
Glass transition temperature (Tg):
120 - 130°C
Fracture Toughness:
1.5 - 1.6 MPa.m½
Suitable for:
Highly toughened system designed to withstand the extreme pressure-cycling requirements of hydrogen vessels manufactured via towpreg winding. Optimized manufacturing viscosity profile and fast curing for high productivity.
Huntsman offers a selection of resin systems optimized for the Towpreg Winding process. Prototypes have demonstrated that hydrogen vessels made with an ARALDITE® towpreg system can be cured in as little as 30 minutes, while still providing the required toughness and hot/wet performance.
As a building block producer, Huntsman has access to a wide range of commercial and new building blocks, as well as strong experience in formulation and expertise in predictive simulation. Our experts work with customers to design custom-tailored impregnation formulations. Simulation capabilities help clients to significantly decrease development time, expediting resin system selection, process parameters determination, and process safety measures (avoiding risk of local exotherm).
Our leading composite expertise, broad product range and unique simulation capabilities can reduce development cycles by up to 50 %.
Huntsman Advanced Materials offers innovative solutions that support manufacturers in the design and production of composite pressure vessels for hydrogen storage and transportation.
Towpregs offer a high level of control over the resin content on the fiber, which translates to consistent mechanical properties for the finished parts. Compared to traditional wet filament winding, the towpreg process can make the workplace cleaner, as there is no liquid resin, and safer, as prepreg exhibits little to no emission of volatile off-gassing compounds (VOCs), and thus does not expose operators to hazardous volatile chemicals. Towpreg can be up to 2.5 times faster than wet filament winding. Winding speed can be over 5 meters per second, and a wide range of winding angles is possible. Cure times can be as short as 30 minutes, and out life is between one week and one month at room temperature.
Material cost is higher than that of wet winding materials, and prepregs typically require refrigerated storage. However, the greater product throughput can offset the higher material cost.
Towpreg resin systems must offer low initial viscosity at processing temperature for fast impregnation, high storage stability at ambient temperatures, and the correct level of tack to enable bobbin unwinding and mandrel winding.
ARALDITE® LY 3508 resin / ARADUR® 1571 hardener / Accelerator 1573 features long out life, high toughness and high thermal resistance.
For applications requiring faster cure time, we recommend our Accelerator 1575, which allows hydrogen vessels to be cured in as little as 30 minutes.
Our resin systems display optimal rheology for the hot-melt impregnation process, low viscosity for tow impregnation at 30-50° C, low tack for fast bobbin unwinding, and an optimal balance between latency in storage and reactivity during part production.
