Waxes aresynthesized by many plants and animals. Those of animal origin typically consist ofwax esters derived from a variety of fatty acids and carboxylic alcohols. In waxes of plant origin, characteristic mixtures of unesterified hydrocarbons may predominate over esters.[2] The composition depends not only on species, but also on geographic location of the organism.
The best-known animal wax isbeeswax, used in constructing thehoneycombs of beehives, but other insects also secrete waxes. A major component of beeswax is myricyl palmitate which is anester oftriacontanol andpalmitic acid. Its melting point is 62–65 °C (144–149 °F).Spermaceti occurs in large amounts in the head oil of thesperm whale. One of its main constituents iscetyl palmitate, another ester of afatty acid and afatty alcohol.Lanolin is a wax obtained from wool, consisting of esters ofsterols.[1]
Plants secrete waxes into and on the surface of theircuticles as a way to control evaporation, wettability and hydration.[3] Theepicuticular 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 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 wax andouricury wax.
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]
Although many natural waxes contain esters, paraffin waxes are hydrocarbons, mixtures of alkanes usually in ahomologous series of 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 CnH2n+2, such ashentriacontane, C31H64. 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 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 is a fossilized wax extracted from coal andlignite.[7] It is very hard, reflecting the high concentration of saturatedfatty acids and alcohols. Although dark brown and odorous, they can be purified and bleached to give commercially useful products.
As of 1995[update], about 200 million kilograms of polyethylene waxes were consumed annually.[3]
Polyethylene waxes are manufactured by one of three methods:
The direct polymerization of ethylene, potentially including co-monomers;
The thermal degradation of high molecular weight polyethylene resin;
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.[citation needed]
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 forplastics. 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.[3]
Waxes such asparaffin wax orbeeswax, and hard fats such astallow are used to makecandles, used for lighting and decoration. Another fuel type used in candle manufacturing includessoy.Soy wax is made by the hydrogenation process using soybean oil.
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.
A wax coating makes thisManila hemp waterproof.Alava lamp is a novelty item that contains wax melted from below by a bulb. The wax rises and falls in decorative, molten blobs.
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 eggs in Romania, Ukraine, Poland, Lithuania and the Czech Republic.Paraffin wax is used in making chocolate covered sweets.
^abWilhelm Riemenschneider1 and Hermann M. Bolt (2005). "Esters, Organic".Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim.doi:10.1002/14356007.a09_565.pub2.
^abEA Baker (1982) Chemistry and morphology of plant epicuticular waxes. In The Plant Cuticle. Ed. DF Cutler, KL Alvin, CE Price. Academic Press.ISBN0-12-199920-3
^abcUwe Wolfmeier, Mr. Hans Schmidt, Franz-Leo Heinrichs, Georg Michalczyk, Wolfgang Payer, Wolfram Dietsche, Klaus Boehlke, Gerd Hohner, Josef Wildgruber "Waxes" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002.doi:10.1002/14356007.a28_103.
^Floros, Michael C.; Raghunanan, Latchmi; Narine, Suresh S. (2016-11-01). "A toolbox for the characterization of biobased waxes".European Journal of Lipid Science and Technology.119 (6): n/a.doi:10.1002/ejlt.201600360.ISSN1438-9312.
^Schrodi, Yann; Ung, Thay; Vargas, Angel; Mkrtumyan, Garik; Lee, Choon Woo; Champagne, Timothy M.; Pederson, Richard L.; Hong, Soon Hyeok (2008-08-01). "Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable Feedstocks".CLEAN – Soil, Air, Water.36 (8):669–673.Bibcode:2008CSAW...36..669S.doi:10.1002/clen.200800088.ISSN1863-0669.
^The rational arts of living: Ruth and Clarence Kennedy Conference in the Renaissance, 1982, page 187, Studies in History, No 50, Alistair Cameron Crombie, Nancy G. Siraisi, Dept. of History of Smith College, 1987.
