Paraffin wax  

The hydrocarbon C₃₁H₆₄ is a typical component of paraffin wax.

Paraffin wax is a white or colorless soft solid derivable from petroleum, coal or oil shale, that consists of a mixture ofhydrocarbon molecules containing between twenty and forty carbon atoms. It is solid at room temperature and begins to melt above approximately 37 °C (99 °F);^[1] its boiling point is >370 °C (698 °F).[2] Common applications for paraffin wax includelubrication, electrical insulation, and candles. [3] It is distinct from kerosene, another petroleum product that is sometimes called paraffin.

In chemistry, paraffin is used synonymously with alkane, indicating hydrocarbons with the general formula C_nH_2n+2. The name is derived from Latin parum ("barely") + affinis, meaning "lacking affinity" or "lacking reactivity", referring to paraffin's unreactive nature.[4]

Applications

In industrial applications, it is often useful to modify the crystal properties of the paraffin wax, typically by adding branching to the existing carbon backbone chain. The modification is usually done with additives, such as EVA copolymers, microcrystalline wax, or forms of polyethylene. The branched properties result in a modified paraffin with a higher viscosity, smaller crystalline structure, and modified functional properties. Pure paraffin wax is rarely used for carving original models forcasting metal and other materials in the lost wax process, as it is relatively brittle at room temperature and presents the risks of chipping and breakage when worked. Soft and pliable waxes, like beeswax, may be preferred for such sculpture, but "investment casting waxes," often paraffin-based, are expressly formulated for the purpose.

Properties[edit]

Paraffin wax is mostly found as a white, odorless, tasteless, waxy solid, with a typical melting point between about 46 and 68 °C (115 and 154 °F),[5] and a density of around 900 kg/m³.[6] It is insoluble in water, but soluble in ether, benzene, and certain esters. Paraffin is unaffected by most common chemical reagents but burnsreadily.[7] Its heat of combustion is 42 kJ/g.

Paraffin wax is an excellent electrical insulator, with a resistivity of between 10¹³ and 10¹⁷ ohm metre.[8] This is better than nearly all other materials except some plastics (notably Teflon). It is an effective neutron moderator and was used in James Chadwick's 1932 experiments to identify the neutron.[9][10]

Paraffin wax is an excellent material for storing heat, with a specific heat capacity of 2.14–2.9 J g⁻¹ K⁻¹ (joules per gramkelvin) and a heat of fusion of 200–220 J g⁻¹.[11] This property is exploited in modified drywall for home building material: a certain type of wax (with the right melting point) is infused in the drywall during manufacture so that it melts during the day, absorbing heat, and solidifies again at night, releasing the heat.[12] Paraffin wax phase-change cooling coupled with retractable radiators was used to cool the electronics of the Lunar Rover.[13] Wax expands considerably when it melts and this allows its use in wax thermostatic element thermostats for industrial, domestic and, particularly, automobile purposes.