RECYCLABLE TYPE IV HYDROGEN PRESSURE VESSEL FOR FUEL CELL ELECTRIC VEHICLES

Transportation plays a vital role in people’s daily lives and the global economy, but it also contributes massively to global warming. Mobility from land, air, and sea is still heavily reliant on polluting internal combustion engines (ICEs). The automobile or transportation industry is responsible for 10% of the world’s carbon dioxide (CO₂) emissions by producing an estimated 80 million vehicles yearly. A typical passenger vehicle emits approximately 4.6 MT of CO₂ per year. In recent years two alternate fuel technologies, battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs), have emerged as alternatives to the conventional ICEs. These technologies are in early stages of adaptation and have comparable lifetime CO₂ emissions. In the case of FCEV, the hydrogen fuel used for powering is stored in Type IV composite pressure vessels. These vessels are made from epoxy thermoset resins due to their high mechanical strength and endurance. The use of epoxy, however, makes the pressure vessels non-recyclable, thereby resulting in CO₂ emissions caused by the end-of-life management. The paper illustrates the development of a novel recyclable epoxy resin system by selecting specific molecules from the proprietary Recyclamine® technology platform. Process requirements for wet winding and performance requirements for hydrogen Type IV pressure vessels are considered during the development of the product. The resin system is characterized by process properties (viscosity, reactivity, and cure kinetics), and mechanical properties (tensile, flexural, and fracture toughness at +25°C, -40°C, and +85°C), followed by the development of a Type IV hydrogen pressure vessel of 52 liters capacity and 700 bar working pressure with PA6 as the liner. The manufactured pressure vessel is performance tested for drop, cyclic, and burst strength in accordance with ISO/FDIS 19881:2018(E). Subsequently, recycling and recovery trials are conducted using a low-energy solvolysis process to demonstrate the proof of concept and circularity of recyclable pressure vessels. The recycling process enables recovery of carbon rovings and epoxy resin matrix as thermoplastic. The use of recyclable pressure vessels in FCEV-powered vehicles has the potential to lower the 10-year lifetime CO₂ emissions by 10 tons of CO₂ equivalent, thereby making it the most attractive technology for automotive and transportation.