Hydrocarbon propellants

Carbon dioxide Dichlorodifluoromethane Nitrogen Nitrous oxide Propane propellant, hydrocarbon Cyclopentane... 

Solutions. To dehver a spray, the formulated aerosol product should be as homogeneous as possible. That is, the active ingredients, the solvent, and the propellant should form a solution. Because the widely used halocarbon and hydrocarbon propellants do not always have the desired solubiUty characteristics for all the components in the product concentrate, special formulating techniques using solvents such as alcohols (qv), acetone (qv), and glycols (qv), are employed. 

Sprays. Aerosol spray emulsions are of the water-in-oil type. The preferred propellant is a hydrocarbon or mixed hydrocarbon—hydrofluorocarbon. About 25 to 30% propellent, miscible with the oil, remains in the external phase of the emulsion. When this system is dispensed, the propellant vaporizes, leaving behind droplets of the w/o emulsion (Fig. 2b). A vapor tap valve, which tends to produce finely dispersed particles, is employed. Because the propellant and the product concentrate tend to separate on standing, products formulated using this system, such as pesticides and room deodorants, must be shaken before use. 

Propellants. The propellant, said to be the heart of an aerosol system, maintains a suitable pressure within the container and expels the product once the valve is opened. Propellants may be either a Hquefied halocarbon, hydrocarbon, or halocarbon—hydrocarbon blend, or a compressed gas such as carbon dioxide (qv), nitrogen (qv), or nitrous oxide. 

Table 2. Physical Properties of Chlorofluorocarbon and Hydrocarbon Propellants...

Hydroca.rbons. Hydrocarbonsn such as propane, butane, and isobutane, which find use as propellants, are assigned numbers based upon their vapor pressure in psia at 21°C. For example, as shown in Table 2, aerosol-grade propane is known as A-108, / -butane as A-17. Blends of hydrocarbons, eg, A-46, and blends of hydrocarbons and hydrochlorocarbons orHCFCs are also used. The chief problem associated with hydrocarbon propellants is their flammabihty. 

Hydrocarbons have, for the most part, replaced CFCs as propellants. Most personal products such as hair sprays, deodorants, and antiperspirants, as well as household aerosols, are formulated using hydrocarbons or some form of hydro-carbon—halocarbon blend. Blends provide customized vapor pressures and, if halocarbons are utilized, a decrease in flammabiUty. Some blends form azeotropes which have a constant vapor pressure and do not fractionate as the contents of the container are used. 

In 1987 nonmotor fuel uses of butanes represented ca 16% of the total consumption. Liquid petroleum gas (LPG) is a mixture of butane and propane, typically in a ratio of 60 40 butane—propane however, the butane content can vary from 100 to 50% and less (see Liquefied petroleum gas). LPG is consumed as fuel in engines and in home, commercial, and industrial appHcations. Increasing amounts of LPG and butanes are used as feedstocks for substitute natural gas (SNG) plants (see Fuels, synthetic). / -Butane, propane, and isobutane are used alone or in mixture as hydrocarbon propellents in aerosols (qv). 

The popularity of aerosols has been declining. A widely used group of propellants, the fluorinated hydrocarbons, have been restricted in use since it was found that they can harm the environment by reducing the o2one layer of the upper atmosphere (see AiRPOLLUTlON ATMOSPHERIC MODELING Ozone). 

The regulation Hsts 137 toxic and reactive substances and a threshold quantity for each. The regulation also appHes to flammable Hquids and gases in quantities of 10,000 lb or more (>4.5 metric tons), except hydrocarbon fuels and Hquids stored in unpressuri2ed, ambient temperature tanks, as weU as to the manufacture of any quantities of explosives (see Exlosives and propellants) and pyrotechnics (qv). 

Moorite Propellant. A series of rocket proplnts submitted to PicArsn for evaluation in 1949. They consisted of an oxidizer (such as K perchlorate) 70, and a cured rubber hydrocarbon plus accelerators, 30%. Although the examined samples proved to possess desirable props for rocket proplnt use, their thermal stability was poor and their press exponent undesirably high. It was concluded that further work was required on the method of prepn to eliminate these defects... 

Temperature Cycling Capabilities of Solid Propellant and Binders Containing a Difunctional Hydrocarbon Prepolymer , Report No AFRPL TR-71-56, Contract No F04611-7042-0016, Aerojet Solid Proplsn Co, Sacramento (1971)... 

Mayo, The Chemistry of Aging of Hydrocarbon Binders in Solid Propellants , CP lA Publ 262, Johns Hopkins Univ, Silver Spring (1975)... 

Of major concern are the health and environmental impacts of the abundant chlorinated and brominated hydrocarbons (ref. 2). These materials have numerous industrial applications as pesticides, solvents, propellants, refrigerants, plastics, fire retardants and extinguishers, disinfectants for drinking water, pharmaceuticals and electronic chemicals. Many chemical manufacturers utilize chlorinated and brominated organics as intermediates. It is estimated, for instance, that almost 85 % of the pharmaceuticals produced in the world require chlorine at some stage of synthesis. 

There has been increase in the application of these componnds since the synthesis of flnorinated alkanes and related componnds in the 1930s. These include flnorinated hydrocarbons that were formerly nsed as propellants, polymerized tetraflnoroethene, and the polyflnorinated C -Cg carboxyl-ates and snlfonates. All of them are notable for their inertness under normal conditions. Aromatic flnorinated componnds are discnssed in Chapter 9, Part 3. 

Hydrocarbons have also been considered as potential propellants for pharmaceutical aerosols. To date concerns regarding flammability seem to have precluded significant developments with propane, isobutane, butane, and mixtures of these alkanes [28]. 

When mixed with hydrocarbons in approximately stoicheiometric proportions, a sensitive highly explosive mixture is produced which needs careful handling [1,2], The use of such mixtures as rocket propellants has also been investigated [3], Explosion of only 10 g of a mixture with toluene caused 10 deaths and 20 severe injuries [4], The mixture contained excess toluene in error [5], Detonation characteristics of mixtures with benzene, toluene (and nitrobenzene) were studied [6],... 

Hydrocarbon materials, 20 180 Hydrocarbon propellants, 2 775 physical properties of, 2 776t Hydrocarbon raw materials, 23 686-687 Hydrocarbon release hazard, 20 627 Hydrocarbon remediation, technologies for, 23 112... 

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