MAPP gas

"MAPP gas" is a trademarked name, belonging to The Linde Group, and previously belonging to the Dow Chemical Company, for a fuel gas based on a stabilized mixture of methylacetylene (propyne) and propadiene. The name comes from the original chemical composition, methylacetylene-propadiene propane. "MAPP gas" is also widely used as a generic name for UN 1060 stabilised methylacetylene-propadiene (unstabilised methylacetylene-propadiene is known as MAPD). MAPP gas is widely regarded as a safer and easier-to-use substitute for acetylene. In the spring of 2008, true MAPP gas production ended in North America when production was discontinued at the only remaining plant in North America that still manufactured it. Current products labeled "MAPP" are, in fact, MAPP substitutes. These versions are stabilized liquefied petroleum gas (LPG) with high levels of propylene.

MAPP gas can be used in combination with oxygen for heating, soldering, brazing and even welding due to its high flame temperature of 2925 °C (5300 °F) in oxygen. Although acetylene has a higher flame temperature (3160 °C, 5720 °F), MAPP has the advantage that it requires neither dilution nor special container fillers during transport, allowing a greater volume of fuel gas to be transported at the same given weight, and it is much safer in use.

The MAPP/oxygen flame is not entirely appropriate for welding steel, due to the high concentration of hydrogen in the flame - higher than acetylene, but lower than any of the other petroleum fuel gases. The hydrogen infuses into the molten steel and renders the welds brittle. For small-scale welding with MAPP this is not a serious problem, as the hydrogen escapes readily, and MAPP/oxygen can in practice be used for welding small steel parts.

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