Overview – What is Wax?
Wax is an organic, plastic-like substance that is solid at ambient temperature and becomes liquid when melted. Because wax is plastic in nature, it usually deforms under pressure without the application of heat.
The General Features of Wax:
- Solid at ambient temperature
- Thermoplastic in nature
- Liquid at 110 to 200°F
- Insoluble in water
Wax Varieties. Wax Categories.
The term “wax” is applied to a large number of chemically different materials. Technological advances in the world today have led to an increasing number of commercially available substances of various chemical compositions and properties which have acquired the name “wax”. In the most general terms, waxes are “naturally” or “synthetically” derived. Waxes can be further categorized by origin as follows:
- Ethylenic polymers
(e.g. polyethylene & polyol ether-esters)
- Chlorinated naphthalenes
- Hydrocarbon type, e.g. Fischer-Tropsch
Petroleum wax is ultimately derived from crude oil. Obtained from the ground, crude oil is a compositionally varied product, consisting of a mixture of hydrocarbons. It is the resultant product of the decomposition of tiny aquatic plants and animals that lived in the ancient seas millions of years ago. Another name for crude oil is fossil fuel. Crude oil is transported to refineries where it is refined into finished products by complex processes. One of the many products derived from refining is lubricating oil. It is from the lube oil refining process that petroleum waxes are derived.
There are three general categories of petroleum wax that are obtained from lube oil refining. They include paraffin, microcrystalline and petrolatum. Paraffin waxes are derived from the light lubricating oil distillates. Paraffin waxes contain predominantly straight-chain hydrocarbons with an average chain length of 20 to 30 carbon atoms. The general properties of paraffin waxes are described in more detail below.
Microcrystalline waxes are produced from a combination of heavy lube distillates and residual oils. They differ from paraffin waxes in that they have poorly defined crystalline structure, darker color, and generally higher viscosity and melting points. Microcrystalline waxes (sometimes also called micro wax) tend to vary much more widely than paraffin waxes with regard to physical characteristics. Microcrystalline waxes can range from being soft and tacky to being hard and brittle, depending on the compositional balance.
The last category of petroleum wax is referred to as petrolatums. Petrolatums are derived from heavy residual oils and are separated by a dilution and filtering (or centrifuging) process. Petrolatums are microcrystalline in nature and semi-solid at room temperature.
Other terms are also used to refer to petroleum wax. In general these terms refer to the amount of oil contained in the product. Slack wax refers to petroleum wax containing anywhere from 3 to 50% oil content. Scale wax refers to wax containing 1 to 3% oil. Fully refined paraffin (FRP) wax is wax that has had nearly all of the oil refined out of it. Fully refined paraffins typically have less than 0.5% oil content.
General Properties of Paraffin Wax
Paraffin Wax is a natural product derived from the molecular components of decayed vegetable and animal material. Paraffin wax consists of a complex mixture of hydrocarbons with the following general properties.
- Good water barrier
- Clean-burning fuel
Paraffin waxes are characterized by a clearly defined crystal structure and have the tendency to be hard and brittle. The melt point of paraffin waxes generally falls between 120° and 160°F.
Individual test methods are determined by molecular size & structure, chemical composition and oil content. Paraffin wax consists mostly of straight chain hydrocarbons with 80 to 90% normal paraffin content and the balance consists of branched paraffins (iso-paraffins) and cycloparaffins.
Typical test methods that can be measured and controlled include melt point, congealing point, hardness, oil content, viscosity and color. However, these physical properties alone do not completely define the suitability of a wax for a particular application. The functional properties of wax should be considered as well. These include the translucency & opaqueness of the wax, solid appearance (e.g. dry, waxy, mottled, shiny), flexibility, etc. It is the combination of physical and functional properties that ultimately determine if a particular wax is right for a given application.