A substance used to produce gas, bubbles or structural holes in liquids, polymers, plastics, and metals. The purpose of blowing, or foaming, agents are to reduce a meterial's density while also increasing its thermal and acoustical insulation properties. Some blowing agents, such isocyanate, dinitroso compounds (dinitroso pentamethylene tetramine) and hydrazides (benzene sulfonyl hydrazide) generate Nitrogen upon heating and are used to make thermoplastic and elastomeric foams from Polyethylene, Silicone, Epoxy, and vinyl resins. Additionally, they are used in fire extinguishers. Other types of foaming agents, such as bicarbonates, produce Carbon dioxide. In Ethafoam, isobutene is used as a blowing agent along with glycerol monostearate as a permeation control agent (Williams 2019).
- Physical blowing agents: These include CFCs (Chlorofluorocarbon) HCFCs, hydrocarbons (pentane, isopentane, etc.) and liquid CO2. The bubble making process is endothermic and irreversible.
- Chemical blowing agents: Numerous gaseous products and byproducts formed by chemical reactions usually release exothermic heat in the process. These processes are also irreversible.
- Mechanically made foam: The introduction of bubbles through whisking or injection into pre-polymerized liquids usually results in the release of gas during solidification.
- Soluble fillers: Fillers, such as Sodium chloride crystals may be washed out after solidification leaving small inter-connected holes.
- Hollow Spheres: Glass shells/spheres (Microballoons), epoxide shells, fly ash, vermiculite can be mixed in a liquid to form a network of voids in a solid.
Synonyms and Related Terms
foaming agent; agent moussant (Fr.)
Resources and Citations
- Wikipedia: Blowing agent Accessed June 2023
- R. Scott Williams, ‘Plastic Storage Products’ In ‘Preventive Conservation: Collection Storage’ Lisa Elkin and Christopher A. Norris (eds.), Society for the Preservation of Natural History Collections, New York. 2019.
- Theodore J. Reinhart, 'Glossary of Terms', Engineered Plastics, ASM International, 1988
- Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
- Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
- Art and Architecture Thesaurus Online, https://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000