Waxes



Waxes
To my knowledge, there is no satisfactory definition of the word "wax" in chemical terms. It is derived from the Anglo-Saxon word "weax" for beeswax, so a practical definition of a wax may therefore be "a substance similar in composition and physical properties to beeswax". Technologists use the term for a variety of commercial products of mineral, marine, plant and insect origin that contain fatty materials of various kinds. Biochemists link waxes with the thin layer of fatty constituents that cover the leaves of plants or provide a surface coating for insects or the skin of animals.
 
The other way to define wax is in the way..
 
“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.”
 
All of these tend to contain wax esters as major components, i.e. esters of long-chain fatty alcohols with long-chain fatty acids.

The nature of the other lipid constituents can vary greatly with the source of the waxy material, but they include hydrocarbons, sterol esters, aliphatic aldehydes, primary and secondary alcohols, diols, ketones, β-diketones, triacylglycerols, and many more.

Types of waxes:


Waxes are organic compounds that characteristically consist of a 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 or 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 (s a waxpresent in the head cavities of the sperm whale (Physeter macrocephalus). ) 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 isCarnauba 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 aliphatichydrocarbons, 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.


Lanolin (wool wax)
This material is secreted by sheep sebaceous glands and collected from crude wool by dilute alkali or detergent washing. Unwashed wool contains about 10-24% of greasy matter and a small proportion of salts of long-chain fatty acids. Lanolin contains fatty esters (14-24%), sterols and triterpene alcohol esters (45-65%), free alcohols (6-20%), sterols (cholesterol, lanosterol) and terpenes (4-5%). Hydroxylated fatty acids (mainly hydroxy palmitate) are found either free or esterified.
 
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 long been use 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 forBedikat Chametz, and not tallow or oil. Candles have also played a role in paganreligions 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
Subscribe to: Posts (Atom)