Blowing agents flammable

In addition to remnants of monomers and catalysts, PU foams may also have remnants of several other components used during their preparation as well, such as cell-stabilisers, blowing agents, flammability retarding agents and accelerators. 

While this book does not cover shock-sensitive powders, such as primary explosives, UN-DOT Class 4.1 Flammable Solids are within its scope. These include thermally unstable powders that can both deflagrate in an oxidant and decompose in bulk. Examples include some nitrogen blowing agents. Should ignition occur at any point, a propagating decomposition... 

The term CFCs is a general abbreviation for ChloroFluoroCarbons. They have been extensively used since their discovery in the thirties, mainly as refrigerant, foam blowing agent, or solvent because of their unique properties (non toxic, non flammable, cheap). However, after the first warning of Rowland and Molina [1] in 1974 that CFCs could destroy the protective ozone layer, the world has moved rapidly towards a phase-out of CFCs. Because the destruction of stratospheric ozone would lead to an increase of harmful UV-B radiation reaching the earth s surface, the production and use of CFCs is prohibited (since January 1, 1995 in the European Union and since January 1, 1996 worldwide). 

The blowing agent can be a hydrocarbon (pentane, for example), which is easily flammable, and precautions against fire must be taken at all the stages of transport, handling, storage, manufacture... 

The mass diffusivity coefficient of isobutane blowing agent from LDPE foam was found using a onedimensional diffusion model of two concentric cylinders with Dirichlet boundary conditions. An average mass diffusivity coefficient was used to calculate the mass of isobutane remaining in the foam for different boundary conditions. The influence of temperature and additives on diffusion was also examined. The use of the mass diffusivity coefficient in assessing the flammability of PE foam in the post-extrusion period is discussed. 2 refs. USA... 

Virtually all plastic foams are blown with inert gases (COs. Ns. H 0). Among these blowing agents, hydrocarbons and some of the HCFs and HFCs are flammable ajtd pose a fire hazard in handing al the manufacturing plants. 

Table 10.8 Flammability and environmental considerations for blowing agents"...

DOT CLASSIFICATION 4.1 Label Flammable SoHd, EXPLOSIVE SAFETY PROFILE Poison by intravenous, intraperitoneal, and subcutaneous routes. Moderately toxic by ingestion. Questionable carcinogen. Mutation data reported. Can ignite when handled and burns very rapidly. Many N-nitroso compounds are carcinogens. A blowing agent. When heated to decomposition it emits toxic fumes of NOx. See also N-NITROSO COMPOUNDS. 

A suitable blowing agent should have low toxicity, low odor, low flammability, low corrosiveness, low molecular weight, high specific gravity, non-VOC (photochemical reactivity not greater than that of ethane), low ODP, low GWP, and low cost. 

Some of the important factors to consider in the development of alternative physical blowing agents are solubility, permeability, boiling point, vapor pressure, flammability, toxicity, VOC, ODP, GWP, availability, and cost. Similarly, the key important factors to be considered in the selection of CBAs for a given polymer are decomposition temperature, gas yield, rate of gas release, environmentally acceptable decomposition products, toxicity, and dispersability in the polymer matrix. 

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