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Index
»
DDS LEC FINALS
»
Chapter 14 - DISPERSE SYSTEMS
»
level 9
level: level 9
Questions and Answers List
level questions: level 9
Question
Answer
Factors that render aerosol effective
• Amount of propellant • Valve assembly • Container • Particle size
Comprised (1) the liquid phase - liquefied propellant and product concentrate (2) the vapor phase
Two - phase System
Comprised (1) layer of water immiscible liquid propellant, (2) layer of highly aqueous product concentrate (3) vapor pressure
Three - phase Systems
- Compressed rather liquefied, gases may be used to prepare aerosols. - pressure in the headspace of the aerosol container forces the product concentrate up the dip tube and out of the valve Examples of gases: Nitrogen, carbon dioxide and nitrous oxide
Compressed Gas System
Aerosol Container and Valve Assembly 1 must not chemically interact with the container or valve components to avoid unstability of the formulation 2 must be capable of withstanding the pressure required by the product, must be corrosive resistant 3 must contribute to the form of the product to be emitted.
. 1 formulation 2 container and the valve 3 valve
Containers (AEROSOL)
1. Glass, uncoated or plastic coated 2. Metal, including tinplated steel, aluminum, and stainless steel 3. Plastics TINPLATED STEEL: COMMONLY USED
The selection of containers for an aerosol product is based on
1. Its adaptability to production methods 2. Compatibility with formulation components 3. Ability to sustain the pressure intended for the product 4. The interest in design and aesthetic appeal on the part of the manufacturer, and 5. Cost
to permit the expulsion of the contents of the can in the desired form, at the desired rate, and, in the case of metered valve, in the proper amount or dose.
VALVE ASSEMBLY
1 materials used in the manufacture of valves must be __ and approved by __ 2 materials used in making valve parts:
1) inert, BFAD 2 plastic, rubber, aluminum, and stainless steel
Factors that render aerosol effective
• Amount of propellant • Valve assembly • Container • Particle size