thumb|right|Cetyl palmitate, a typical wax ester. Wax refers to a class of chemical compounds that are plastic (malleable) near ambient temperatures. Characteristically, they melt above 45 °C (113 °F) to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents. All waxes are organic compounds, both synthetic and naturally occurring.

Types

Waxes are organic compounds that characteristically consist of long alkyl chains. Natural waxes are typically esters of fatty acids and long chain alcohols. Synthetic waxes are long-chain hydrocarbons lacking functional groups.

Plant and animal waxes

Waxes are biosynthesized by many plants and animals. They typically consist of several components, including wax esters, wax acids, wax alcohols, and hydrocarbons. Wax esters are typically derived from a variety of carboxylic acids and a variety of fatty alcohols. The composition depends not only on species, but also on geographic location of the organism. Because they are mixtures, naturally produced waxes are softer and melt at lower temperatures than the pure components.

Animal waxes

The best known animal wax is beeswax, but other insects secrete waxes. A major component of beeswax is the ester myricyl palmitate substance which is used in constructing their honeycombs. Its melting point is 62-65 °C. Spermaceti occurs in large amounts in the head oil of the sperm whale. One of its main constituents is cetyl palmitate, another ester of a fatty acid and a fatty alcohol. Lanolin is a wax obtained from wool, consisting of esters of sterols.

Plant waxes

Especially in warm climates, plants secrete waxes as a way to control evaporation and hydration. From the commercial perspective, the most important wax is Carnauba wax, a hard wax obtained from the Brazilian palm. Containing the ester myricyl cerotate, it has many applications. Other more specialized vegetable waxes include candelilla wax, ouricury wax, sugarcane wax, retamo wax, jojoba oil. The epicuticular waxes of plants are mixtures of substituted long-chain aliphatic hydrocarbons, containing alkanes, fatty acids, primary and secondary alcohols, diols, ketones, aldehydes.

Petroleum derived waxes

Although most natural waxes are esters, paraffin waxes are hydrocarbons, mixtures of alkanes usually in a homologous series of chain lengths. These materials represent a significant fraction of petroleum. They are refined by vacuum distillation. Paraffin waxes are mixtures of saturated n- and isoalkanes, naphthenes, and alkyl- and naphthene-substituted aromatic compounds. The degree of branching has an important influence on the properties. Millions of tons of paraffin waxes are produced annually. They are used in adhesives, in foods (such as chewing gum and cheese wrapping), in cosmetics, and as coatings.

Montan wax

Montan wax is a fossilized wax extracted from coal and lignite. It is very hard, reflecting the high concentration of saturated fatty acids and alcohols, not esters that characterize softer waxes. Although dark brown and smelly, they can be purified and bleached to give commercially useful products.

Polyethylene and related derivatives

Some waxes are obtained by cracking polyethylene at 400 °C. The products have the formula (CH₂)_nH₂, where n ranges between about 50 and 100. As of 1995, about 200 million kilograms/y were consumed.

Uses

Waxes are mainly consumed industrially as components of complex formulations, often for coatings. The main use of polyethylene and polypropylene waxes is in the formulation of colourants for plastics. Waxes confer matting effects and wear resistance to paints. Polyethyelene waxes are incorporated into inks in the form of dispersions to decrease friction. They are employed as release agents. They are also used as slip agents, e.g. in furniture, and corrosion resistance.

Candles

Waxes and hard fats such as tallow have been used to make candles, used for lighting and decoration in a number of religious traditions, including Christianity and Hinduism, as well as various neo-pagan religions such as Wicca. The Emperor Constantine is reported to have called for the use of candles during an Easter service in the 4th century AD. Candles continue to be used today by Christians in worship as symbols of the light of Christ. In the Roman Catholic Church, beeswax candles are used, since a colony of bees is a celibate sisterhood with a single mother. Candles of wax or tallow took the place of lamps used in various Jewish rituals such as the Sabbath lights; in the Havdalah ceremony; and the Hanukkah lights. A synagogue had to be well lit, and pious folk used to donate candles for the purpose. On the basis of the verse: 'The soul of man is a candle of the Lord', a special candle which burns twenty-four hours is kindled on the anniversary of the death of a near relative (Yahrzeit) and often two lighted candles are placed at the head of the corpse awaiting burial. In fact, according to the Shulchan Aruch, wax candles are the only kind of light which can be used for Bedikat Chametz, and not tallow or oil. Candles have also played a role in pagan religions and in modern humanist festivals. Virtually all rituals in Wicca include the lighting of altar candles, where two main candles are often used to represent the God and the Goddess; and the lighting of candles is a central theme at the Wiccan holiday of Brigid or Imbolc, which is also known as Candlemas or the Feast of the Waxing Light. Wax candles were also used in secular life for lighting, signals in warfare, safety in travel and for time keeping, and are still in popular use today to provide soft lighting for meals and other social activities.

Other uses

Sealing wax was used to close important documents in the Middle Ages. Waxes are used to make wax paper, impregnating and coating paper and card to waterproof it or make it resistant to staining, or to modify its surface properties. Waxes are also used in shoe polishes, wood polishes, and automotive polishes, as mold release agents in mold making, as a coating for many cheeses, and to waterproof leather and fabric. Wax has been used since antiquity as a temporary, removable model in lost-wax casting of gold, silver and other materials.

Wax with colorful pigments added has been used as a medium in encaustic painting, and is used today in the manufacture of crayons and colored pencils. Carbon paper, used for making duplicate typewritten documents was coated with carbon black suspended in wax, typically montan wax, but has largely been superseded by photocopiers and computer printers. In another context, lipstick and mascara are blends of various fats and waxes colored with pigments, and both beeswax and lanolin are used in other cosmetics. Ski wax is used in skiing and snowboarding. Also, the sports of surfing and skateboarding often use wax to enhance the performance. Beeswax or coloured synthetic wax is used to decorate Easter eggs in Ukraine and the Czech Republic. Paraffin wax is used in making chocolate covered bon-bons. Wax is also used in wax bullets, which are used as simulation aids.

Wax types

Animal waxes

Beeswax - produced by honey bees

Chinese wax - produced by the scale insect Ceroplastes ceriferus

Earwax - found in the human ear.

Lanolin (wool wax) - from the sebaceous glands of sheep

Shellac wax - from the lac insect Kerria lacca

Spermaceti - from the head cavities and blubber of the sperm whale

=== Vegetable waxes ===

Bayberry wax - from the surface wax of the fruits of the bayberry shrub, Myrica faya

Candelilla wax - from the Mexican shrubs Euphorbia cerifera and Euphorbia antisyphilitica

Carnauba wax - from the leaves of the Carnauba palm, Copernica cerifera

Castor wax - catalytically hydrogenated castor oil

Esparto wax - a byproduct of making paper from esparto grass, (Macrochloa tenacissima)

Japan wax - a vegetable triglyceride (not a true wax), from the berries of Rhus and Toxicodendron species

Jojoba oil - a replacement for spermaceti, jojoba is pressed from the seeds of the jojoba bush, Simmondsia chinensis

Ouricury wax - from the Brazilian feather palm, Syagrus coronata.

Rice bran wax - obtained from rice bran (Oryza sativa)

Soy wax - from soybean oil

Mineral waxes

Ceresin waxes

Montan wax - extracted from lignite and brown coal

Ozocerite - found in lignite beds

Peat waxes

Petroleum waxes

Paraffin wax - made of long-chain alkane hydrocarbons

Microcrystalline wax - with very fine crystalline structure

Petroleum jelly

Synthetic waxes

Polyethylene waxes - based on polyethylene

Fischer-Tropsch waxes

Chemically modified waxes - usually esterified or saponified

substituted amide waxes

polymerized α-olefins

See also

Slip melting point

References

External links

Waxes

www.microcrystallinewax.net, resource for microcrystalline wax research

Waxes

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