Wax

For other uses, seeWax (disambiguation).

Waxesare a diverse class oforganic compoundsthat arelipophilic,malleablesolids near ambient temperatures. They includehigher alkanesandlipids,typically withmelting pointsabove about 40 °C (104 °F), melting to give lowviscosityliquids. Waxes areinsolublein water but soluble in nonpolar organic solvents such ashexane,benzeneandchloroform.Natural waxes of different types are produced by plants and animals and occur inpetroleum.

Cetyl palmitate,a typicalwax ester

Commercialhoneycombfoundation, made by pressing beeswax between patterned metal rollers

Chemistry

Ceroline brand wax for floors and furniture, first half of 20th century. From theMuseo del Objeto del Objetocollection.

Waxes are organic compounds that characteristically consist of longaliphaticalkylchains, although aromatic compounds may also be present. Natural waxes may contain unsaturated bonds and include variousfunctional groupssuch asfatty acids,primaryandsecondary alcohols,ketones,aldehydesand fatty acidesters.Synthetic waxes often consist ofhomologous seriesof long-chain aliphatic hydrocarbons (alkanesor paraffins) that lackfunctional groups.

Plant and animal waxes

Waxes aresynthesizedby many plants and animals. Those of animal origin typically consist ofwax estersderived from a variety of fatty acids and carboxylic alcohols. In waxes of plant origin, characteristic mixtures of unesterified hydrocarbons may predominate over esters.The composition depends not only on species, but also on geographic location of the organism.

Animal waxes

The best-known animal wax isbeeswax,used in constructing thehoneycombsof beehives, but other insects also secrete waxes. A major component of beeswax is myricyl palmitate which is anesteroftriacontanolandpalmitic acid.Its melting point is 62–65 °C (144–149 °F).Spermacetioccurs in large amounts in the head oil of thesperm whale.One of its main constituents iscetyl palmitate,another ester of afatty acidand afatty alcohol.Lanolinis a wax obtained from wool, consisting of esters ofsterols.

Plant waxes

Plants secrete waxes into and on the surface of theircuticlesas a way to control evaporation, wettability and hydration.Theepicuticular waxesof plants are mixtures of substituted long-chain aliphatic hydrocarbons, containing alkanes, alkyl esters, fatty acids, primary and secondary alcohols,diols,ketones and aldehydes.From the commercial perspective, the most important plant wax iscarnauba wax,a hard wax obtained from the Brazilian palmCopernicia prunifera.Containing the ester myricyl cerotate, it has many applications, such as confectionery and other food coatings, car and furniture polish, floss coating, andsurfboard wax.Other more specialized vegetable waxes includejojoba oil,candelilla waxandouricury 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.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.

Petroleum derived waxes

See also:Paraffin wax

Although many natural waxes contain esters, paraffin waxes are hydrocarbons, mixtures of alkanes usually in ahomologous seriesof chain lengths. These materials represent a significant fraction of petroleum. They are refined byvacuum distillation.Paraffin waxes are mixtures of saturated n- and iso-alkanes,naphthenes,andalkyl- and naphthene-substituted aromatic compounds. A typical alkane paraffin wax chemical composition comprises hydrocarbons with the general formula C_nH_2n+2,such ashentriacontane,C₃₁H₆₄.The degree of branching has an important influence on the properties.Microcrystalline waxis a lesser produced petroleum based wax that contains higher percentage of isoparaffinic (branched) hydrocarbons and naphthenic 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 waterproofing coatings and in polishes.

Montan wax

Montan waxis a fossilized wax extracted from coal andlignite.It is very hard, reflecting the high concentration of saturatedfatty acidsand alcohols. Although dark brown and odorous, they can be purified and bleached to give commercially useful products.

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;
2. The thermal degradation of high molecular weight polyethylene resin;
3. 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 melt 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, 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.

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 (i.e., to confer non-glossy finishes) and wear resistance to paints. Polyethylene waxes are incorporated into inks in the form of dispersions to decrease friction. They are employed asrelease agents,find use as slip agents in furniture, and confer corrosion resistance.

Candles

Wax candle

Waxes such asparaffin waxorbeeswax,and hard fats such astalloware used to makecandles,used for lighting and decoration. Another fuel type used in candle manufacturing includessoy.Soy waxis made by the hydrogenation process using soybean oil.

Wood products

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

Other uses

A wax coating makes thisManila hempwaterproof.

Alava lampis a novelty item that contains wax melted from below by a bulb. The wax rises and falls in decorative, molten blobs.

Sealing waxwas used to close important documents in theMiddle Ages.Wax tabletswere used as writing surfaces. There were different types of wax in the Middle Ages, namely four kinds of wax (Ragusan,Montenegro,Byzantine,andBulgarian), "ordinary" waxes fromSpain,Poland,andRiga,unrefined waxes and colored waxes (red, white, and green).Waxes are used to makewaxed paper,impregnating andcoating paperand card to waterproof it or make it resistant to staining, or to modify its surface properties. Waxes are also used inshoe polishes,wood polishes,and automotive polishes, asmold release agentsinmold making,as a coating for manycheeses,and towaterproofleather and fabric. Wax has been used since antiquity as a temporary, removable model inlost-wax castingofgold,silverand other materials.

Wax with colorful pigments added has been used as a medium inencaustic painting,and is used today in the manufacture ofcrayons,china markersand coloredpencils.Carbon paper,used for making duplicatetypewrittendocuments was coated withcarbon blacksuspended in wax, typicallymontan wax,but has largely been superseded byphotocopiersandcomputer printers.In another context,lipstickandmascaraare blends of various fats and waxes colored with pigments, and bothbeeswaxandlanolinare used in othercosmetics.Ski waxis used inskiingandsnowboarding.Also, the sports of surfing andskateboardingoften use wax to enhance the performance.

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 decorateEaster eggsin Romania, Ukraine, Poland, Lithuania and the Czech Republic.Paraffin waxis used in making chocolate covered sweets.

Wax is also used inwax bullets,which are used as simulation aids, and forwax sculpturing.

Specific examples

Animal waxes

• Beeswax– produced byhoney bees
• Chinese wax– produced by thescale insectCeroplastes ceriferus
• Lanolin(wool wax) – from thesebaceous glandsofsheep
• Shellacwax – from thelac insectKerria lacca
• Spermaceti– from the head cavities and blubber of thesperm whale

Vegetable waxes

• Bayberry wax– from thesurface waxof thefruitsof the bayberry shrub,Myrica faya
• Candelilla wax– from the Mexican shrubsEuphorbia ceriferaandEuphorbia antisyphilitica
• Carnauba wax– from the leaves of the carnauba palm,Copernicia cerifera
• Castor wax– catalytically hydrogenatedcastor oil
• Esparto wax – a byproduct of making paper fromesparto grass(Macrochloa tenacissima)
• Japan wax– a vegetabletriglyceride(not a true wax), from the berries ofRhusandToxicodendronspecies
• Jojoba oil– a liquidwax ester,from the seed ofSimmondsia chinensis.
• Ouricury wax– from the Brazilian feather palm,Syagrus coronata.
• Rice bran wax– obtained fromricebran(Oryza sativa)
• Soy wax– from soybean oil
• Tallow treewax – from the seeds of the tallow treeTriadica sebifera.

Mineral waxes

• Ceresinwaxes
• Montan wax– extracted fromligniteandbrown coal
• Ozocerite– found in lignite beds
• Peat waxes

Petroleum waxes

• Paraffin wax– made of long-chainalkanehydrocarbons
• Microcrystalline wax– with very fine crystalline structure

See also

• Slip melting point
• Wax acid
• Wax argument,or the "ball of wax example", is a thought experiment originally articulated by Renė Descartes.

External links

• WaxesArchived2016-12-02 at theWayback Machine