1 1 1

Propellant Basics

SATA Aerosol 101

March 20, 2013

Barbara Decaire

2

Agenda

• What’s an Aerosol?

• How an Aerosol Works

• Propellants

-Liquified Gas vs. Compressed Gas

-Comparative Physical Properties

• Flammability

• Regulatory / Environmental Considerations

3

Aerosol Basics

•An aerosol can be defined as: A self-contained

pressurized product able to be released as a fine

spray, typically by means of a propellant gas.

•The propellant is what pushes things out of the

can; it is what makes an aerosol.

• Some aerosol products contain only propellant,

like dusters and freeze sprays

• Most aerosols are formulated products, i.e., they

contain a propellant and other ingredients like

solvents and actives (antiperspirants, resins,

fragrances, etc.)

•A solvent may be an active ingredient, as in

cleaning products, or may be a carrier for active

ingredients, as in lubricants, antiperspirants, etc.

4

What Goes on Inside an Aerosol Can?

Actuator (or “Button”)

Valve

Dip Tube

Liquid Phase

Gaseous Propellant

The propellant exerts

pressure on the surface of

the liquid. When the

actuator is pressed, the

spring-activated valve

opens and propellant

pushes liquid up the dip

tube.

5

Types of Aerosol Products

Product Type Dip Tube? What is

Dispensed?

Product Examples

Duster No Vapor •Duster spray

• Air Horn

Aerosol Mist Yes Liquid droplets •Hair spray

•Spray paint

•Air freshener

Freeze Spray Yes Liquid stream •Freeze Spray for electronic

diagnostics

•Insect spray

•Freeze spray for preparing

histology samples

•Wart remover

6

How Does a Can Dispense an Aerosol Mist?

Actuator (or “Button”)

Valve

Dip Tube

Liquid Phase (Contains

Propellant + Formulation

Ingredients)

Gaseous Propellant The propellant exerts

pressure on the surface of

the liquid. When the

actuator is pressed, the

spring-activated valve

opens and propellant

pushes liquid up the dip

tube. The actuator is

designed to mechanically

break up the liquid into

small droplets which we call

an aerosol mist.

Product Examples: hair

spray, spray paint, air

freshener

7

What Goes on Inside a Duster Can?

Actuator (or “Button”)

Valve

Liquid Propellant (may

contain fragrance, bitterant,

etc.)

Gaseous Propellant

•The propellant pressurizes

the contents of the can.

When the actuator is

pressed, the spring-

activated valve opens and

vapor is expelled from the

can. The duster can does

not include a dip tube.

•Evaporating propellant will

chill the can, lowering the

pressure. Use short sprays.

•An inverted duster will

dispense liquid

Product Examples: duster

spray, air horn

8

What Goes on Inside a Can of Freeze Spray?

Actuator (or “Button”)

Valve

Dip Tube

Liquid Propellant

Gaseous Propellant The propellant exerts

pressure on the surface of

the liquid. When the

actuator is pressed, the

spring-activated valve

opens and propellant

pushes liquid up the dip

tube. A narrow stream of

liquid is expelled.

Product Examples: Insect

spray, Freeze sprays for

electronic diagnostics, wart

remover, freeze spray for

histology sample

preparation

9

Propellant Property Considerations

• Vapor Pressure

- Critical propellant property but there is no Optimal Pressure

Desired pressure is dictated by application

- Impacts Spray Characteristics and Can Selection

• Solubility/Miscibility

- Should mix with other propellants and Common Solvents

- Water solubility

DME >> hydrocarbons >> fluorocarbons

A propellant that doesn’t mix with water will impart its full vapor pressure

• Compatibility

- Aerosol Valves (Plastic and Elastomeric Components)

- Cans (Tinplate Steel or Aluminum) and Liner Materials

- Active Ingredients (e.g., Actives in Personal Care Products)

- Storage stability testing of each formulation is a MUST

10

Two Types of Propellant

Liquified Gas

• 134a, 1234ze, 152a, Propane, Butane, Isobutane, DME, blends

• Soluble in or dispersed in formulation just before use; creates a finer spray

• Constant pressure and spray pattern throughout use

• Pressure affected by storage and use temperature

• Typical can product fill 85%

Compressed Gas

• CO2, N2, N2O

• Acts as a piston to push product from can

• Pressure drops as product is used, resulting in a coarser, wetter spray

• Temperature has little effect on pressure

• Carbon dioxide forms carbonic acid in aqueous formulations

• Typical can fill 50-70%; need headspace for propellant

11

Aerosol with a Compressed Gas Propellant

With a compressed gas, the pressure in an aerosol formulation will not remain constant as the product is used. High pressure generally gives a fine, dry spray; low pressure generally gives a course, wet spray.

11

Compressed Gas Propellants: Carbon Dioxide, Nitrogen,

Nitrous Oxide

100

psig 75

psig 50

psig

12

Aerosol with a Liquefied Gas Propellant 12

With a liquefied gas, the pressure in an aerosol formulation will remain constant as the product is used.

50

psig 50

psig 50

psig

13

Liquified Gas Physical Properties

Property HFO-

1234ze

HFC-

134a

HFC-

152a DME Propane i-Butane n-butane

Molecular Weight 114 102 66 46 44 58 58

Boiling Point (°C) -19 -26 -25 -25 -42 -12 -0.5

Vapor Pressure

(bars gauge @21°C) 3.2 4.9 4.3 4.3 7.5 2.1 1.2

Vapor Pressure

(bars gauge @54°C) 9.7 13.7 12.1 12.0 17.7 6.7 4.5

LFL/UFL*

(Vol.% in Air @21°C) NONE NONE 3.9-16.9

3.4-

18.0 2.2–9.5 1.8–8.4 1.9-8.5

Liquid Density

(g/cc @21°C) 1.17 1.22 0.91 0.67 0.51 0.55 0.58

*Propellants with flame limits are flammable by US D.O.T.

14

Vapor Pressure Comparison

0

50

100

150

200

250

30 55 80 105 130 Temperature ( o F)

Va

po

r P

res

su

re (

ps

ia)

HFC-152a

DME

Isobutane

HFC-134a

HFO-1234ze

15

Propellant Blends

•The liquefied gas propellants will all mix with each other and use of blends is common

•According to Raoult’s Law, the pressure of a blend will be the weighted average pressure of

the individual propellants.

Pressureblend = (MF1 X VP1 + MF2 X VP2 + MF3 X VP3 + ….)

MF= mole fraction VP = Vapor Pressure

(Note: This is a guideline; in reality most blend deviate from this)

•Commonly used hydrocarbon blends include A-46 (VP=46 PSIG at 21C) and A-70 (VP=70

PSIG at 21C)

•These are propane/isobutane blends

•Similar pressures can be achieved with propane/n-butane blends and

propane/isobutane/n-butane blends, but these are less common

•If the propellant mixes with the liquid ingredients to form a one-phase aerosol, the pressure

will be reduced

•If the propellant does not mix with the other ingredients, as in a water-based product, the

pressure will not be reduced

16

Propellant Blend Examples

Blend Name Ingredients

Vapor Pressure

@21.1°C

A-46 Propane

Isobutane

15.2 wt%

84.8 wt%

46 psig

NIP-46 n-butane

Isobutane

propane

46.9 wt%

31.2 wt%

21.9 wt%

46 psig

A-70 Propane

Isobutane

42.8 wt%

57.2 wt%

70 psig

NP-70 n-butane

Propane

50.7 wt%

49.3 wt%

70 psig

•Propellant Distributors offer a wide variety of Blends

to suit any application

17

Flammability

• By D.O.T., a Flammable Propellant is a Gas Having a Flammable Range in Air at 20°C

- Exhibits vapor flame limits according to ASTM E-681

• Flammable Aerosol Classification is Based on:

- The concentration of flammable components

- Heat of combustion

- Ignition distance test

- Enclosed space ignition test (aka the closed drum test)

• The flammability of a pure substance like a propellant may differ from that of a formulated product

- For example, nonflammable aerosol products may be formulated using HFC-152a, a flammable propellant

18

Enclosed Space Ignition Test

Drum: 60cm X 72cm; ~ 200 Liter (0.2m3)

In this test, the entire contents of an aerosol can are sprayed into a 200 liter drum that is lying on its

side. The back of the drum is hinged to allow for pressure relief. A lighted candle is positioned inside

the drum, mid-way along the length of the drum. The spraying time to ignition, if any, is recorded. The

test is repeated three times with three separate cans.

19

Flame Extension Test

The flame extension or flame propagation test is conducted by holding an aerosol can

15 cm. (6 inches) from a candle flame and spraying the product across the flame. A

flame extension of more than 45 cm. (18 inches) or flashback of the flame to the

actuator at any degree of valve opening indicates a flammable product.

45cm 15cm

20

90cm 15cm

Ignition Distance test

This test is similar to the flame projection test except that the cans are sprayed at

varying distances from the ignition source. The ignition source is a gas burner.

Testing begins at a distance of 90 cm from the ignition source. Spraying is repeated at

15 cm increments down to a minimum distance of 15 cm from the flame.

21

Aerosol Foam Flammability

• Foaming aerosol product is sprayed onto a watch glass

• Flame passes over foam surface

• Flame height and duration determine flammability classification

- Extremely Flammable

Height ≥ 20 cm and duration ≥ 2 s

Height ≥ 4 cm and duration ≥ 7 s

- Flammable

Height ≥ 4 cm and duration ≥ 2 s

22

23

What is a Global Warming Potential?

• Global Warming Potential (GWP)

• Measure of a Gas’s Ability to Absorb/Re-Emit IR Radiation Integrated Over

a Given Period of Time (the Time Horizon) Compared to a Reference Gas

• By Convention, CO2 is the Reference Gas

•

•GWP is a function of:

• Wavelengths at Which the Molecule Absorbs

• Strength of the Absorption

• Atmospheric Lifetime of the Molecule

• IR Light Absorption: IR Spectra used to determine IR absorption cross section

•

•Atmospheric Lifetime: Determined by measuring Hydroxyl Radical (OH-)

reaction rates. This is the primary atmospheric breakdown mechanism for

halocarbons

24

Global Warming-Based Regulations

• Current and Anticipated Global Warming-Based Regulations Will Limit Emissions of Greenhouse Gases

• The Kyoto Protocol

- Developed Countries to Reduce Greenhouse Gas Emissions by a

- Collective Average of 5% Below 1990 Levels

- The EU Must Reduce Emissions by 8%

• F-Gas

- Targets Specific Sources of Fluorinated Greenhouse Gas Emissions

Elimination of HFC-134a from Automotive A/C Systems Beginning in 2011

Nearer-Term Regulation of Other Products Like One-Component Foam and Novelty Aerosols in 2008 and 2009

• California Global Warming Solutions Act

- Reduction of Greenhouse Gas Emissions to 1990 Levels by 2020

- CARB to Develop a List of “Early Actions” that can be Implemented by 2010

• Australia and Other Countries have instituted “Carbon Taxes”

25

Photochemical Reactivity

• While Stratoshpheric Ozone protects the Earth, Tropospheric Ozone is a pollutant and an irritant (a component of photochemical smog)

- Adverse health effects can occur at levels well under 100 PPB

- EPA requires control/reduction measures at levels above 75 PPB

• There are no industrial activities that directly product ozone

• The only effective way to reduce ozone levels is to control emissions of photochemically reactive species: VOCs and nitrogen oxides

• Maximum Incremental Reactivity (MIR) is a laboratory measured property which indicates the degree to which a substance participates in ozone creation

- EU uses an equivalent measure of photochemical reactivity, POCP (photochemical ozone creation potential)

• Substances with a MIR higher than that of Ethane are considered VOCs

• Substances with lower MIR may be non-VOC, subject to approval by EPA and/or CARB

Compound MIR

g O3/g VOC

Methane 0.016

HFO-1234ze 0.09

Ethane 0.27

Acetone 0.35

Propane 0.57

Methanol 0.65

n-Octane 0.69

Butane 1.18

Ethanol 1.7

Propene 11

• VOCs (Volatile Organic Compounds) are photochemically reactive substances that

participate in reactions that result in increased concentrations of ground-level

(tropospheric) ozone

26

Environmental Properties

GWP

0

200

400

600

800

1000

1200

1400

1600

-0.2 0.3 0.8 1.3 MIR

HFC-

152a

HFO-1234ze

HFC-

134a

DME Propane i-Butane

HFO-1234ze HFC-134a HFC-152a DME Propane i-Butane

GWP

(100 year ITH; GWPCO2 = 1) 6 1320 122 <15 <15 <15

Photochemical Reactivity

(MIR gO3 /g VOC) 0.09 0.0007 0.0175 0.93 0.57 1.23

Larger bubble indicates higher

GWP

27

Regulatory Influence on Selection

Propellant Flammable VOC Status

EPA CA

GWP DFE Cost

CO2 + + + + + $

N2 + + + + + $

Propane - - - + - $

Isobutane - - - + - $

Butane - - - + - $

134a + + + - - $$$

152a - + + +/- - $$

1234ze + + +/- + - $$$$

Performance and Regulatory Status must be Balanced

28

Questions?

Please Contact:

Barbara Decaire

Applications Development Manager

Honeywell Aerosols

716-827-6241

barbara.decaire@honeywell.com

Gary Knopeck

Manager, Fluorocarbons Technical Service

716-827-6242

gary.knopeck@honeywell.com