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From Wikipedia, the free encyclopedia

For other uses, see Wax (disambiguation).

Cetyl palmitate, a typical wax ester.

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[edit]

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[edit]

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

Animal waxes[edit]

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 in large amounts in the head oil of sperm whales. Lanolin, also an animal wax, is obtained from wool and it consists of esters of sterols. ^[1]

Ceroline brand wax for floors and furniture, first half of 20th century. From the Museo del Objeto del Objeto collection.

Plant waxes[edit]

Waxy cuticle of a variegated Geranium leaf.

Plants secrete waxes into and on the surface of their cuticles as a way to control transpiration 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[edit]

Waxes made from plants or animals can be chemically modified to improve their properties.^[4] This can be done using environmentally-friendly methods like olefin metathesis and enzymatic reactions. ^[5][6] By doing this, waxes can be made from low-cost materials like vegetable oils.

Petroleum derived waxes[edit]

See also: Paraffin wax

Petroleum contains hydrocarbons that can be processed into paraffin wax through vacuum distillation. Paraffin waxes are made up of hydrocarbons with the formula CnH2n+2. How much the hydrocarbons branch affects the wax's properties, like melting and boiling points. Another type of petroleum-based wax is microcrystalline wax, which contains more branched and cyclic hydrocarbons, and is produced less often.

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[edit]

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. Examples of these are cars, shoes, and instrument polishes, as well as paints.

Polyethylene and related derivatives[edit]

As of 1995, about 200 million kilograms of polyethylene waxes were consumed annually. ^[3]

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;
   • Reduces chain length and molecular weight.
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 melting point.

Polyethylene waxes made through degradation or recovery from polyethylene resin contain tiny particles that could evaporate and cause fires if not removed. To prevent this, these waxes go through a process to remove these particles, which results in a flash point of more than 500°F (260°C).

Polyethylene resin plants often generate a byproduct called Low Polymer Wax (LPW), which is unrefined and can contain harmful substances like volatile oligomers, corrosive catalysts, foreign materials, and water. To create polyethylene wax, the LPW must be refined by removing the oligomers and hazardous catalysts.

Properly refining LPW is important for several reasons:

First, the refining process helps to remove impurities that can affect the color, odor, and overall quality of the wax. ^[13] This is especially important for LPW that will be used in food contact applications, as any contaminants could potentially contaminate the food and pose a health risk.

In addition, refining can help to improve the properties of the wax, such as its melting point, hardness, and adhesion. This can make it more suitable for specific applications, such as coatings or adhesives. ^[14]

Finally, refining LPW is important for regulatory compliance. ^[15] The FDA has strict regulations in place for food contact materials, including LPW. ^{[citation needed]} Refining the wax can help to ensure that it meets these regulations and is safe for use in food contact applications.

Uses[edit]

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.

Handmade wax candle.

Candles[edit]

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[edit]

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[edit]

Wax coating on Red Dragon Welsh cheese.

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 in the production of wax papers and coating papers, which are known for their effective resistance to moisture and stains.

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.

Art and Paper Applications

Wax was used in the Middle Ages as a model in lost-wax casting. It was also used for encaustic painting, and is now used to make crayons, china markers, and colored pencils. Carbon paper used to make copies was coated with wax and carbon black, but is now less common due to photocopiers and computer printers.

Cosmetics Applications

Lipstick and mascara consist of different fats and waxes with added pigments for color. Beeswax and lanolin are also common ingredients 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.

Specific examples[edit]

Animal waxes[edit]

• 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[edit]

• 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[edit]

• Ceresin waxes
• Montan wax - extracted from lignite and brown coal
• Ozocerite - found in lignite beds
• Peat waxes

Petroleum waxes[edit]

• Paraffin wax - made of long-chain alkane hydrocarbons
• Microcrystalline wax - with very fine crystalline structure

See also[edit]

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

References[edit]

1. Wilhelm Riemenschneider1 and Hermann M. Bolt "Esters, Organic" Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a09_565.pub2
2. ^ Jump up to:^{a b} EA Baker (1982) Chemistry and morphology of plant epicuticular waxes. In The Plant Cuticle. Ed. DF Cutler, KL Alvin, CE Price. Academic Press. ISBN 0-12-199920-3
3. ^ Jump up to:^{a b c} Uwe 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.
4. ^ 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. ISSN 1438-9312.
5. ^ 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. doi:10.1002/clen.200800088. ISSN 1863-0669.
6. ^ Petersson, Anna E. V.; Gustafsson, Linda M.; Nordblad, Mathias; Börjesson, Pål; Mattiasson, Bo; Adlercreutz, Patrick (2005-11-17). "Wax esters produced by solvent-free energy-efficient enzymatic synthesis and their applicability as wood coatings". Green Chemistry. 7 (12): 837. doi:10.1039/b510815b. ISSN 1463-9270. Archived from the original on 2019-12-09. Retrieved 2016-12-06.
7. ^ Ivanovsky, Leo (1952). Wax chemistry and technology.
8. ^ "Minwax® Paste Finishing Wax | Specialty Products". Minwax.com. 2012-01-31. Archived from the original on 2012-11-05. Retrieved 2012-12-15.
9. ^ 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.
10. ^ Handbook To Life In The Medieval World, Volume 2, page 202, Handbook to Life, Facts on File Library of World History, Madeline Pelner Cosman, Linda Gale Jones, Infobase Publishing, 2008. ISBN 9780816048878
11. ^ "How To Make Skateboard Wax: A Home DIY Guide". www.blackspell.co.uk. 28 July 2021. Retrieved 2021-09-22.
12. ^Almqvist, A.; Pellegrini, B.; Lintzén, N.; Emami, N.; Holmberg, H-C.; Larsson, R. A Scientific Perspective on Reducing Ski-Snow Friction to Improve Performance in Olympic Cross-Country Skiing, the Biathlon and Nordic Combined. Frontiers in Sports and Active Living 2022, 4. https://doi.org/10.3389/fspor.2022.844883.
13. Osswald, T. A.; Hernandez-Ortiz, J. P.; Hyer, M. W. Polymer Processing, 2nd ed.; Hanser Publishers: Munich, Germany, 2006.
14. Fried, J. R. Polymer Science and Technology, 3rd ed.; Prentice Hall: Upper Saddle River, NJ, 2013.
15. Forrest, M. J. Food Contact Materials - Rubbers, Silicones, Coatings and Inks; Rapra Technology Limited: Shawbury, UK, 2009.