The Wet Filament Winding (WFW) process is used to manufacture cylindrical or hemispherical composite structures by winding fiber from a bobbin. The fiber is impregnated with resin just prior to being wound onto the mandrel. The main automotive applications are pressure vessels for CNG or hydrogen, drive shafts and other rotationally symmetrical parts.
Huntsman designs resin systems based on anhydride or amine chemistries that meet the processing and performance requirements of WFW applications. Our systems offer a wide range of glass transition temperatures, from 80° to over 200° C, and various combinations of mechanical performance. All our systems present low viscosity, which facilitates wetting of the fibers, long latency at room temperature, which allows running the bath for a long period of time (and reduces waste of unused resin) and appropriate reactivity to manage curing time and safety aspects (low or controlled exothermic behavior).
Glass transition temperature (Tg):
132 - 138°C
Pot life:
56 - 62 h at 23°C
Suitable for:
REACH compliant anhydride based system. Very long latency combined with low reaction exotherm. Mix viscosity of 600-1000 mPas at 25°C.
Glass transition temperature (Tg):
115 - 125°C
Pot life:
> 48 h at 23°C
Suitable for:
REACH compliant anhydride based system. Very high fracture toughness (KIc = 1.5 – 1.6 MPa.m1/2) combined with very long latency and low reaction exotherm. Mix viscosity of 600 - 1000 mPas at 25°C.
Glass transition temperature (Tg):
122 - 130°C
Pot life:
80 - 90 h at 23°C
Suitable for:
REACH compliant anhydride based system. Very long latency combined with low reaction exotherm. Mix viscosity of 450-700 mPas at 25°C.
Glass transition temperature (Tg):
115 - 120°C
Pot life:
260 - 280 min at 23°C
Suitable for:
Amine based system with high mechanical performance, low-temperature curing capability and higher reactivity compared to anhydride systems. Mix viscosity of 500-650 mPas at 25°C.
Huntsman is a pioneer of the Wet Filament Winding process, and has a long track record of providing systems to produce pressure vessels for compressed natural gas (CNG), and now for hydrogen. Our simulation capabilities help customers to reduce development time by speeding 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.
Wet Filament Winding (WFW) is a well-established technology. The equipment and process have been optimized for computer-controlled automation, so labor requirements are lower compared to other open molding processes. Continuous fibers can be used over a whole component area (without joints) and, to a certain extent, fibers be applied at various angles, in order to orient them in the load direction. WFW allows highly repetitive fiber placement, and delivers a high degree of fiber loading, which provides the high tensile strength and high strength-to-weight ratio required for cylindrical products such as pressure vessels.
WFW can only produce rotationally symmetrical parts. The angle of reinforcement is controlled by the ratio of the carriage speed and the rotation speed of the mandrel. Maximum winding speed is 1-2 meters per second. WFW is an open process that can expose workers to liquid resin, so hygienic conditions must be maintained.
Optimal winding viscosity is 800-1,000 mPa for good fiber impregnation. Optimal pot life is several hours at impregnation temperature. Cure temperature should be as low as possible in order to avoid internal stresses in the final part.
Huntsman's range of ARALDITE® resin systems includes both epoxy/anhydride and epoxy/amine chemistries, with a range of glass transition temperatures. All systems are qualified for CNG and hydrogen pressure vessels. All feature long latency (long pot life) and low viscosity for fast impregnation.
