User:OppositeWorlds/Wax

From Wikipedia, the free encyclopedia For other uses, see Wax (disambiguation).

Waxes are a diverse class of organic compounds that are lipophilic (fat-soluble) and malleable solids at room temperatures. Waxes have melting points typically above 40 °C (104 °F) which makes them low viscosity liquids. Waxes are insoluble in water but soluble in non-polar organic solvents such as hexane, benzene and chloroform. Natural waxes of different types are produced by plants and animals and occurs in petroleum. Synthetic waxes can be made from natural gas or ethylene.

Chemistry
Waxes are organic compounds that consists of long aliphatic alkyl chains and in some, aromatic compounds. Natural waxes may contain unsaturated bonds and include various functional groups such as fatty acids, primary and secondary alcohols, ketones, aldehydes and fatty acid esters. Synthetic waxes often consist of repeated series of long-chain aliphatic hydrocarbons (alkanes or paraffins) that lack functional groups.

Plant and animal waxes
Waxes are made by many plants and animals. Those of animal origin typically consist of wax esters derived from a variety of fatty acids and carboxylic alcohols. In waxes of plant origin, characteristic mixtures of un-esterified hydrocarbons may predominate over esters. [2] The composition depends not only on species, but also on geographic location of the organism.

Animal waxes
The best-known animal wax is beeswax used in constructing the honeycombs of beehives, but other insects also secrete waxes. A major component of beeswax is myricyl palmitate which is an ester of triacontanol and palmitic acid. Beeswax has a high melting point of 62-65 °C, making beeswax candles last longer than other candles. Another type of animal wax is spermaceti. It is produced large amounts in the head oil of sperm whales. Lanolin, also an animal wax, is obtained from wool, consists of esters of sterols.[1]

Plant waxes
Plants secrete waxes into and on the surface of their cuticles as a way to control evaporation and hydration. [3] The epicuticular waxes of plants are mixtures of substituted long-chain aliphatic hydrocarbons, containing alkanes, alkyl esters, fatty acids, primary and secondary alcohols, diols, ketones and aldehydes.[2]

From the commercial perspective, the most important plant wax is carnauba wax, a hard wax obtained from the Brazilian palm Copernicia prunifera. It contains ester myricyl cerotate which has many applications, such as confectionery and other food coatings, car and furniture polish, floss coating, and surfboard wax. Other more specialized vegetable waxes include jojoba oil, candelilla wax and ouricury wax.

Modified plant and animal waxes
Plant and animal based waxes or oils can undergo selective chemical modifications to produce waxes with more desirable properties than are available in the unmodified starting material.[4] This approach has relied on green chemistry approaches including olefin metathesis and enzymatic reactions and can be used to produce waxes from inexpensive starting materials like vegetable oils.[5][6] Olefin metathesis is an organic chemical reaction that redistributes fragments of alkenes by forming new carbon-carbon double bonds.

Petroleum derived waxes
See also: Paraffin wax

A significant fraction of petroleum constitutes hydrocarbons that makes up paraffin waxes which are are refined by vacuum distillation. A typical alkane paraffin wax chemical composition comprises hydrocarbons with the general formula CnH2n+2. The degree of branching has an important influence on the properties. Microcrystalline wax is a lesser produced petroleum based wax that contains higher percentage of branched hydrocarbons and naphthenic (cyclic) hydrocarbons.

Millions of tons of paraffin waxes are produced annually. They are used in foods such as chewing gum and cheese wrapping; in candles and cosmetics as non-stick and waterproof coating; and in polishes.

Montan wax
Montan wax is a fossilized wax extracted from coal and lignite. [7] This type of wax is very hard, reflecting the high concentration of saturated fatty acids and alcohols. Although they are dark brown and odorous, they can be purified and bleached to give commercially useful products. Such as car and shoes polishes, paints, and instrument polishes.

Polyethylene and related derivatives
As of 1995, about 200 million kilograms of polyethylene waxes were consumed annually.

Polyethylene waxes are manufactured by one of three methods:


 * 1) The direct polymerization of ethylene, potentially including co-monomers also;
 * 2) The thermal degradation of high molecular weight polyethylene resin;
 * 3) * Reduces chain length and molecular weight.
 * 4) The recovery of low molecular weight fractions from high molecular weight resin production.

Each production technique generates products with slightly different properties. Key properties of low molecular weight polyethylene waxes are viscosity, density and melting point.

Polyethylene waxes produced by means of degradation or recovery from polyethylene resin streams contain very low molecular weight materials that must be removed to prevent volatilization and potential fire hazards during use. Polyethylene waxes manufactured by this method are usually stripped of low molecular weight fractions to yield a flash point >500°F (>260°C). Many polyethylene resin plants produce a low molecular weight stream often referred to as Low Polymer Wax (LPW). LPW is unrefined and contains volatile oligomers (a molecule with a few repeating units), corrosive catalyst and may contain other foreign material and water. Refining of LPW to produce a polyethylene wax involves removal of oligomers and hazardous catalyst. Proper refining of LPW to produce polyethylene wax is especially important when being used in applications requiring FDA or other regulatory certification.[citation needed]

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 give matting or non-glossy finishes and wear resistance to paints. Polyethylene waxes are incorporated into inks in the form of dispersions to decrease friction.

Candles
Candles are made from waxes such as paraffin wax, beeswax or soy wax, and hard fats such as tallow. Soy wax is made by the hydrogenation process using soybean oil.

Wax products
Waxes are used as finishes and coatings for wood products. [8] Beeswax is frequently used as a lubricant on drawer slides where wood-to-wood contact occurs.

Other uses
In the Middle Ages, sealing wax was used to close important documents, and wax tablets were used as writing surfaces. The four different types of waxes in the Middle Ages were: Ragusan, Montenegro, Byzantine, and Bulgarian. They were unrefined waxes from Spain, Poland, and Riga with colours (red, white, and green).[9][10] Waxes are used to make wax papers and coating papers, both have moisture- and stain-resistant applications. Polishing, Molding, and Coating Applications

Waxes are also used for polishing (shoe polishes, wood polishes, and automotive polishes), molding (mold release agents), and coating purposes (cheeses, and to waterproof fabric). Some waxes are considered food-safe and are used to coat wooden cutting boards and other items that come into contact with food. Beeswax or coloured synthetic wax is used to decorate Easter eggs in Romania, Ukraine, Poland, Lithuania and the Czech Republic. Paraffin wax is used in making chocolate covered sweets.

Art and Paper Applications

Wax has been used before the Middle Ages 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, china markers 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 replaced by photocopiers and computer printers.

Cosmetics Applications

In another context, lipstick and mascara are blends of various fats and waxes colored with pigments, and both beeswax and lanolin are used in various cosmetics.

Board-sport and Bullet Applications

Ski wax is used in skiing and snowboarding, surfing and skateboarding.[11] The hydrophobic (water-repelling) characteristic of wax helps enhance the athlete's performance by reducing friction.[12 ] Wax is also used in wax bullets, which are used as simulation aids.

Animal waxes

 * Beeswax - produced by honey bees
 * Chinese wax - produced by the scale insect Ceroplastes ceriferus
 * 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, Copernicia 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 liquid wax ester, from the seed of 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
 * Tallow Tree wax - from the seeds of the tallow tree Triadica sebifera.

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