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Polyurethane synthesis, wherein the urethane groups −NH−(C=O)−O− link the molecular units A kitchen sponge made of polyurethane foam . Polyurethane (/ ˌ p ɒ l i ˈ jʊər ə ˌ θ eɪ n,-j ʊəˈr ɛ θ eɪ n /; [1] often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links.
Class 3: Flammable Liquids A flammable liquid is a liquid having a flash point of not more than 60 °C (140 °F), or any material in a liquid phase with a flash point at or above 37.8 °C (100 °F) that is intentionally heated and offered for transportation or transported at or above its flash point in a bulk packaging. The following exceptions ...
For example, in the United States flammable liquids, by definition, have a flash point below 100 °F (38 °C)—where combustible liquids have a flash point above 100 °F (38 °C). Flammable solids are solids that are readily combustible, or may cause or contribute to fire through friction.
Due to the closed-cell nature of rigid polyurethane foams, PUR insulation has minimal water absorption, which coupled with an appropriate cover, makes it a particularly suitable in applications where bacterial growth is a concern. Polyurethane insulation is suitable for insulating pipes with surface temperatures ranging from -196°C to 148°C. [7]
A flammable liquid is a liquid which can be easily ignited in air at ambient temperatures, i.e. it has a flash point at or below nominal threshold temperatures defined by a number of national and international standards organisations.
Organophosphorus flame retardants have been detected in wastewater in Spain and Sweden, and some compounds do not appear to be removed thoroughly during water treatment. [89] [90] Organophosphorus flame-retardants were also found in tap and bottled drinking water in China. [91] Likewise in the Elbe river in Germany. [92]
A water film forms beneath the foam, which cools the liquid fuel, stopping the formation of flammable vapors. This provides dramatic fire knockdown, an important factor in crash rescue firefighting. In the early 1970s, National Foam, Inc. invented alcohol-resistant AFFF technology.
The stacking of the bubblets is similar to aspirated fire fighting foam or compressed air foam systems, except that bubblets are water filled, whereas foam bubbles are only filled with air. Due to the high specific heat of water, it requires more energy to raise the temperature of water than air. Therefore, water-filled bubblets will absorb ...