国生一 国上人生 General requirements for propellants ©Type of propellant Vapor pressure higher than atmosphere ·No toxicity ·Chlorofluorocarbon(CFC)氟氯烷经 ·Inert ·Hydrofluorocarbons(HFAs)氢氟烷烃 Non-flammable,non-explosive ·Dimethyl ether ·No color,no odor .Hydrocarbon ·Cheap ·Compressed gas 国生一 Propellants 国生一 ©Advantages of hydrofluoroalkane(HFA)氢氟烷烃 Hydrofluoroalkane (HFA) Low inhalation toxicity High chemical stability ·Tetrafluoroethane四氟乙烷HFA134a) ·High purity ·Heptafluoropropane七氟丙皖(HFA227) Not ozone depleting Disadvantages of hydrofluoroalkane (HFA) ·Poor solvents Minor greenhouse effect ·High cost HFA-134 国生 Propellants 国生 Propellants The pressure of aerosol is critical to its 圈Raoult'slaw performance.It can be controlled by the type and amount of propellants. P=N.Po na po Mixture of propellants na+np Change vapor pressure Change liquid density B=N,Po= 一Pg n。+n Change solvency P=P+P 44 Shanghai Jiao Tong University General requirements for propellants • Vapor pressure higher than atmosphere • No toxicity • Inert • Non-flammable, non-explosive • No color, no odor • Cheap Shanghai Jiao Tong University Type of propellant • Chlorofluorocarbon (CFC)氟氯烷烃 • Hydrofluorocarbons (HFAs)氢氟烷烃 • Dimethyl ether • Hydrocarbon • Compressed gas Shanghai Jiao Tong University Propellants Advantages of hydrofluoroalkane (HFA)氢氟烷烃 • Low inhalation toxicity • High chemical stability • High purity • Not ozone depleting Disadvantages of hydrofluoroalkane (HFA) • Poor solvents • Minor greenhouse effect • High cost Shanghai Jiao Tong University Hydrofluoroalkane (HFA) • Tetrafluoroethane 四氟乙烷(HFA134a) • Heptafluoropropane 七氟丙烷(HFA227) Shanghai Jiao Tong University Propellants The pressure of aerosol is critical to its performance. It can be controlled by the type and amount of propellants. Mixture of propellants • Change vapor pressure • Change liquid density • Change solvency Shanghai Jiao Tong University Propellants Raoult’s law a b b a b b b b b a a b a a a a P P P P n n n P N P P n n n P N P         0 0 0 0