Propellants and Solvents

Strategies for the 21st Century
Something Old – Something New

• For many decades aerosol and liquid products in the 

consumer and industrial markets have experienced a 

continuous cycle of change mandated by environmental and 

health concerns. While the industry has responded with the 

introduction of “next generation” chemicals these have also 

come under attack leading to addition chemicals being 

created.

• We will discuss the existing menu of chemicals still available 

to the formulator and look at the most recent additions that 

are scheduled to be available in 2013 and 2014. 

• Finally, we will discuss formulation opportunities and how 

new products can utilize these old and new chemicals to meet 

the current and future needs of the respective markets.
Propellants

• Current Propellants:

• Hydrocarbons – Propane, Isobutane, Normal butane

• HFC’s – HFC 134, HFC 152

• Compressed Gases – CO2, Air, Nitrogen

• Oxygenated – DME

• Blends

• New Propellants:

• Hydrocarbons – Ethane

• HFO’s – 1234 ze (Solstice Propellant)
Hydrocarbon Propellants

• Hydrocarbon propellants have been the most common propellant in aerosols since 

the mid - 70s. In recent years VOC regulations have reduced the percentage of 

hydrocarbons in aerosols ,but they continue to be the first choice for products 

around the world. This is due to the following:

• Cost – low when compared to other propellants and solvents and the amount of 

hydrocarbon, as a percentage of formulation, allows for a reduced unit cost.

• Pressure – Hydrocarbons allow for pressures from 17 psig to 108 psig in the pure 

chemicals and their blends. In addition hydrocarbons are compatible with all the 

other old and new propellants.

• Stability – Hydrocarbon are used in solvent based and water based formula. They 

create stable emulsions and can be used without hydrolysis in water systems.

• Toxicity – Hydrocarbons are on the GRAS list and have high TLVs. 

• Environmental – While hydrocarbons are VOCs, they have low MIR values and 

work well in formulas based on Reactivity.

• Flammability – Hydrocarbons are flammable, but can be blended to reduce the 

effect on the package.
HFCs

134

• As a propellant 134 has come under fire in recent years due to it’s high GWP. However 

in reviewing it’s other characteristics, it is obvious that 134 has value as a formulating 

chemical:

• Cost – Moderate, propellant cost can be reduced by blending.

• Pressure – Good intermediate pressure @70F. Can be increased or reduced by blending.

• Stability – Stable in a wide range of formulas.

• Toxicity – Very low, HFC 134 is currently used in medical devices such as inhalers.

• Environmental – While it does have a high GWP, it is not a VOC or Ozone depleator. 

When used in appropriate formulations, 134 has a place in many aerosol products.

• Flammability – HFC 134 is considered non flammable and can be used to reduce the 

overall flammability in aerosols that contain flammable components.
HFCs

152

• HFC 152 – Propellant 152 has become increasing popular in formulated aerosol 

products and dusters. When we look at its characteristics, it is obvious that this 

propellant will continue to grow in aerosol products.

• Cost – Moderate

• Pressure – Very similar to 134. A good intermediate pressure that can be blended 

to achieve higher or lower pressure.

• Stability – Good stability.

• Toxicity – Good TLV, used in dusters, hairspray and other many other products.

• Environmental – Not a VOC, Ozone depleter, and has a low GWP.

• Flammability – Low flammability
Compressed Gases

CO2

• Carbon Dioxide – CO2 has been a common propellant for many years. Historically 

its popularity has cycled up and down in response to environmental trends and the 

marketing strategies of various companies. In todays aerosol market it’s 

commonly utilized in Wasp and Hornet, degreasers, specialty cleaners, and other 

products that will accept the CO2 into solution.

• Cost – As an individual chemical, CO2 is low in cost. However since it is normally 

used in concentrations of 2-4% the balance of the unit will be comprised of more 

expensive chemicals increasing the final cost of the package.

• Pressure – CO2 has a high vapor pressure. This limits it use to very low levels even 

in those solvents with good Oswald coefficients. It does prove useful in aerosols 

where the high pressure increases performance at low temperatures such as 

starting fluids and deicers.

• Stability – CO2 is used primarily in anhydrous formulas. In any water based formula 

the CO2 forms carbonic acid which attacks the metal cans. 

• Toxicity – CO2 has low toxicity.
CO2

• Environmental – While some environmentalists are concerned about the levels of 

CO2 in the atmosphere, the CO2 utilized in aerosol is obtained by fractional 

distillation of air. Therefore the CO2 in aerosols does not add to the atmospheric 

levels and is not an issue for those concerned about global warming.

• Flammability – While CO2 is not flammable, the low levels of CO2 in most aerosols 

is not sufficient to reduce the overall flammability of the product.
Compressed Gases

Others

• Air – Use of air as a propellant has been practiced in Europe since the 1990s. 

Recently introduced in the US, the verdict is still out as to the ability of these 

packages to replace other propellants.

• Nitrogen – Like air which is composed of 78% nitrogen, the use of nitrogen has 

been tried for many decades. Pure nitrogen has the advantage that the oxygen and 

CO2 are removed which eliminates the tendency for oxidation or acid formation. 

However nitrogen is more expensive and is high pressure with low solubility in 

many solvents. 
Oxygenated

DME

• DME – Dimethyl ether was initially utilized in the US in the 1970s. Since then it has 

grown in volume for use in both water and solvent based systems. Being a good 

solvent, DME is unique as a propellant which tend to have low KB values and are 

usually poor solvents outside their chemicals groups.
New Propellants

Solstice Propellant

• The environmental pressure on propellants has been continuous since the middle 

of the 20th century. We have seen the elimination of the CFCs, HCFCs, attack on the 

HFCs, and increasing restrictions on hydrocarbons and DME under VOC 

regulations.

• Responding to the need, Honeywell has introduced a next generation propellant 

known as 1234 ze. Solstice propellant falls into a new class of propellants and 

solvents based on an unsaturated fluorinated base molecule, thus HFO, HydroFluoro-Olefin name. This new propellant has impressive credentials in that it is not 

a VOC, has a low GWP, and is considered non flammable under DOT definitions. 

• With a vapor pressure of 47 psig@70F, it falls into the midrange of propellants and 

can be blended to achieve higher or lower pressures. Overall the prospects for this 

propellant are promising.
Hydrocarbons

Ethane

• Ethane is a common chemical though many people may not know of it. Ethane is a 

saturated hydrocarbon and is a component in natural gas and in the hydrocarbon 

propellants. In recent years Ethane has become available as a purified chemical 

suitable for use in aerosol products.

• Having a pressure of 543 psig @70F Ethane falls between CO2 – 869 psig@70F and 

Propane – 110 psig @70F. In addition Ethane is soluble in most solvents to the 

extent that 4 – 10% can be used in an aerosol formulation.

• From an environmental stand point, Ethane is not a VOC or Ozone depleator, has a 

low GWP, and has a good TLV.

• While Ethane is flammable, it can be incorporated into many flammable 

formulations and it’s flammability can be reduced or eliminated by proper 

blending with other propellants and solvents.

• With its greater solubility, Ethane can produce a better spray pattern than a 

comparable CO2 product and the higher volume of propellant will give greater 

protection from propellant exhaustion. 
Blends

• Blended propellants are the key to making current formulas work efficiently. Prior 

to the 1970s, the industry had available numerous propellants and solvents to 

formulate the variety of products required by consumers and industry. However in 

addressing environmental and toxicity concerns, the regulators did not effectively 

regulate chemicals, they eliminated groups of chemicals without regard to the 

impact on these products and the consumers. The aerosol industry has been able 

to create replacements, but only through the use of propellant and solvent blends.

• For many years formulators have used the flexibility of the hydrocarbon 

propellants to create blends with pressures from 17psig to 110 psig. In addition 

blends of hydrocarbons, DME, HFCs, and CO2 have allowed these products to 

thrive. 

• When formulators are designing a new product, they must address a number of 

characteristics to achieve a product that marketers can offer to the public and that 

the public will purchase. In addition that product must comply with federal and 

state regulations to meet VOC requirements and not contain some proscribed 

chemicals.
Blends

• There are various approaches in designing a new formulation. However most will 

address some consistent parameters:

• 1. cost

• 2.flammability

• 3.solvency

• 4.evaporation rate

• 5. regulatory/VOC/GWP

• 6. toxicity

• 7.pressure

• 8.stability
Cost

• Cost will vary per product, but are generally 

ranked as follows:

• HFO Solstice Propellant 

• HFC 134a

• HFC 152a

• Ethane

• DME

• Propane, Isobutane, Normal butane(A-108, A-31, A-17)

• Nitrogen/Air

• CO2
Cost Comparison

108psig Blend

• Solstice Propellant -

$8.50/lb.*

• Ethane - $2.00/lb.

• Blend - $7.72/lb.

• *lower pricing expected in 

late second quarter

31psig Blend

• Solstice Propellant -

$8.50/lb.*

• A-17 - $.58/lb.

• Blend - $4.31/lb.
Pressure

• Nitrogen – 492psig@ -232.5F 1600psig@70F(estimate)

• CO2 – 859.4 psig

• Ethane – 543 psig

• Propane – 109.3 psig

• HFC 134 – 71.0 psig

• HFC 152 – 63.9 psig

• DME – 61.3 psig

• Solstice Propellant – 47 psig

• Isobutane – 31.1 psig

• Normal butane – 16.9 psig
Pressure Blends

HFO/Hydrocarbon/+

• Solstice – 47 psig

• Ethane – 543 psig

• 108psig blend

• 88% 1234ze

• 12% Ethane

• Cost - $7.72

HFO/Hydrocarbon/-

• Solstice – 47psig

• A-17 – 17psig

• 31psig blend

• 47% 1234ze

• 53% A-17

• Cost - $4.31
Solvency

• KB Values

• DME – 60

• Normal Butane – 20

• Isobutane – 18

• Propane – 15

• Ethane - 12

• HFC 152 – 11

• HFC 134 – 9.2

• Solstice Propellant- 9 
Solvency Blend

Adhesive

• DME – 30% 60

• A-70 - 40% 16

• HFC 152 – 30% 11

• Better solvent

• Lower VOC
Flammability

HFC 134 – non flammable, can suppress other flammables 

Solstice Propellant – considered non flammable

CO2 – non flammable, practical levels of use reduce the ability to suppress 

other flammables

Nitrogen – non flammable, low concentrations in aerosols are not sufficient 

to suppress flammables

HFC 152 – flammable, flammability can be reduced by appropriate additives

Hydrocarbons -ethane, propane, isobutane, normal butane – flammable

DME – flammable, requires modification of equipment to be used in aerosols
Flammability

Blend

• 88% Solstice Propellant

• 12% Ethane

• Reduced cost - $7.72/lb.

• Non VOC

• Low flammability/no flammability

• Low GWP
Flammability 2

• 50% Solstice Propellant

• 50% HFC 152

• Non VOC

• Pressure 55psig@ 70F

• Lower flammability

• Lower cost - $5.26/lb.

• Lower GWP

• Lower unit cost
Regulatory

• Solstice Propellant – non VOC, GWP -6

• HFC 152 – non VOC, GWP – 140

• HFC 134 – non VOC EPA* - GWP – 1300

• Ethane – non VOC (MIR - .26) – GWP – 2.9

• Propane – VOC (low MIR - .46) – GWP – 3

• DME – VOC (MIR – 1.02) – GWP - 1

• Normal Butane – VOC ( MIR 1.08) – GWP – 2.3

• Isobutane – VOC ( MIR – 1.17) – GWP – 3.3

• * HFC 134 while classified by EPA as a non VOC, has been exempted in 

California for specific uses only.
Regulatory blend

• MIR - .70

• Ethane – 46%

• A-17 - 54%

• Blend – 259 PSIG@70F

• Cost - $1.23/lb.

• Unit cost potentially lower
Toxicity

• There are no issues for the toxicity of these 

chemicals. TLVs are high for all. 
Stability

• With the exception of CO2, the remaining 

propellants are used in solvent and water 

based formulas.

• CO2 is not suitable for water based formulas 

due to the formation of carbonic acid.

• It is recommended that all formulas be tested 

prior to commercial release.
Solvents

• HFC 4310 – DuPont Vertrel XF

• HFC 365 – Solvay Solkane 365

• 1,2 Trans Dichloroethylene – DCPC

• Solstice PF – Honeywell

• HFX 110 – DuPont Vertrel
Costs

• 1, 2 Trans Dichloroethylene

• HFC 365

• Solstice PF

• HFC 4310(Vertrel XF)

• HFX 110
Evaporation rates

• Solstice PF

• HFC 4310(XF), HFC 365, 1,2 Trans Dichloroethylene

• HFO 110 (HFX 110) 

• With the exception of HFX 110, all are fast 

evaporating solvents
Evaporation

Ladder*

• Propellant – HFC 134 or HFX 1234ze

• Solstice PF/Vertrel XF

• HFC 365 (Flammable)

• 1,2 Trans Dichloroethylene (Flammable)

• HFX 110

• * Aerosol will exhibit low or no flammability
Solvency

• 1,2 Trans Dichloroethylene – KB 117

• Solstice PF – KB 25

• HFC 365 – KB 14

• HFC 4310 – KB 9

• HFX 110 – less than 10
225 Replacement

• Solstice PF - 10%

• Vertrel XF(4310) – 10%

• Solkane 365 - 55%

• Trans - 25%

• KB – 40

• Cost - $5.78/lb.
141b Replacement

• Vertrel XF – 10%

• Solstice PF – 20%

• Solkane 365 – 25%

• Trans - 45%

• Cost - $5.62

• KB - 61
Flammability

• HFC 4310 – non flammable**

• HFX 110 – non flammable, forms a non flammable azeotrope with Trans at 

a ratio 96/4 of Trans/ HFX 110**

• Solstice PF – non flammable** 

• HFC 365 – flammable* 

• Trans – flammable*

• ** will not ignite

• * will ignite

• FLASH POINT – defined by a specific test
Flammability

• Solstice Propellant – 25% 

• Solstice PF - 20%

• Solkane 365 - 15%

• Trans - 35%

• Ethanol 200 proof - 2%

• HFX 110 - 3%

• Low or no flammability
Flammability 2

• Trans - 94%

• Solstice PF - 3%

• DuPont HFX 110 - 3%

• Low or no flammability

• Cost - $3.09/lb.
Flammability 3

• Trans - 95%

• DuPont HFX 110 - 5%

• Non flammable
Regulatory

• Solstice PF – non VOC, GWP < 7

• HFX 110 – non VOC, low GWP**

• HFC 365 – non VOC, GWP 910 *

• HFC 4310 – non VOC, GWP 1300 *

• Trans – VOC, MIR – 1.25

• * Classified by EPA as non VOC, not exempted in 

California

• ** anticipated to be classified as non VOC
Toxicity

• All solvents have TLVs greater than 200 ppm.