In response to current and possible future restrictions on hydrofluorocarbon (HFC), Honeywell has introduced a propellant that performs like an HFC but exhibits favorable environmental properties. Solstice Propellant (INCI: Tetrafluoropropene) is a nonflammable, aerosol propellant that has a low global warming potential (GWP) and low photochemical reactivity.
The propellant can serve as a replacement for liquefied gas propellants currently in use, with the potential to make significant reductions in greenhouse gas emissions and ground level ozone creation. When substituted for HFC-134a in aerosol products, the propellant can substantially reduce greenhouse gas emissions. With a GWP less than 6, its widespread worldwide adoption could save more than 14 million metric tons per year of carbon dioxide equivalent emissions. Additionally, with an MIR value of 0.09 g O3/g VOC, the propellant does not contribute to ground-level ozone creation and is expected to be classified as a non-VOC in the United States.
The propellant's full chemical name is trans- 1,3,3,3-tetrafluoroprop-1-ene (HFO-1234ze). It mixes with other common propellants such as 134a, 152a, dimethyl ether, butane, isobutane and propane. It is also miscible and compatible with many commonly used solvents like the lower alcohols, ketones, halogenated solvents and hydrocarbons, providing a variety of formulation options. It is thermally and hydrolytically stable and exhibits good compatibility with plastics, elastomers and metals. In particular, it has been shown to be compatible with aluminum, tinplate aerosol cans and PET-lined aerosol cans. The propellant has also been tested with aerosol valves and found to be compatible with common gasket materials including grades of butyl rubber, buna and neoprene. The propellant is nonflammable and has a moderate vapor pressure of 49 PSIG (3.4 bars-gauge) at 70°F (21°C) and 147 PSIG (10 bars-gauge) at 130°F (54°C).
In some situations, it may be beneficial to blend HFO-1234ze with other propellants to optimize a formulation. For example, blends of HFO-1234ze with hydrocarbons or 152a might be useful in personal care formulations while blends with 134a might be used in certain technical aerosols.
Classified as a UN class 2.2 nonflammable liquefied gas, the propellant exhibits a low order of toxicity.The American Industrial Hygiene Association (AIHA) has assigned a Workplace Environmental Exposure Limit (WEEL) of 800 PPM (8-hour time-weighted average).
The propellant complies with global regulations. The product is registered in Europe under REACH (Regulation 1907/2006) for tonnages of more than 1,000 tonnes/annum. It was added to the SNAP List of Acceptable Substitutes for Aerosol Applications in June 2010 and was added to the TSCA inventory without restrictions in November 2010. It is also registered in Japan, China and Canada, with registrations underway in Australia and South Korea.