What is wax?
The word “wax” usually refers to a variety of organic substances that are solid at ambient temperature but become free-flowing liquids at slightly higher temperatures.
The chemical composition of waxes is complex, but normal alkanes are always present in high proportion and molecular weight profiles tend to be wide. The main commercial source of wax is crude oil but not all crude oil refiners produce wax. “Mineral” wax can also be produced from lignite. Plants, animals and even insects produce materials sold in commerce as “wax.”
What are types of waxes?
Paraffin and Microcrystalline waxes are derived from petroleum. They are easy to recover and offer a wide range of physical properties that can often be tailored by refining processes.
Most producers offer two distinct types of petroleum waxes: paraffins, which are distinguished by large, well-formed crystals; and microcrystallines, which are higher melting waxes with small, irregular crystals. Microcrystalline wax contains substantial proportions of branched and cyclic saturated hydrocarbons in addition to normal alkanes.
Some producers also sell “intermediate” wax, in which the boiling range is cut where the transition in crystal size and structure occur. Petroleum wax producers also characterize wax by degree of refinement; fully refined paraffin has oil content generally less than 0.5%, and fully-refined micro-crystalline less than 3%.
“Slack wax,” precursors to the fully refined versions in either case, would have oil content above 3%, and as high as 35% by weight. Paraffin wax produced from petroleum is essentially a pure mixture of normal and iso-alkanes without the esters, acids, etc. found in the animal and vegetable-based waxes.
- Synthetic waxeshave entered the wax market in the past 50 years. Polyethylene waxes are low molecular weight polyethylenes (less than 10,000 Mn) having wax-like properties made by either high-pressure or low-pressure (Zeigler-type catalyst) polymerization. All such waxes have the same basic structure, but the various production processes yield products with distinctly different properties, and these have a major impact on the use of products. Products from one manufacturer may satisfy one particular application, while product from a similar process will not work well.
Beeswax has been traded for over 2,000 years and references to “wax” before the 19th century typically meant beeswax. Yellow beeswax is secreted by bees to build honeycombs; the empty comb is melted in boiling water to recover the wax.
Other animal-based waxes include lanolin from the wool of sheep; ambergris produced in the intestines of sperm whales; and tallow from beef fat.
Some Wax applications
- Building materials:wax is added as a water repellent in the production of wood-based manufactured composite boards such as particle board, medium density, oriented strand and other board products.
- Candles:one of the oldest uses of wax, but still vital. No longer used for primary illumination, candles are the fastest growing segment of the wax market with new decorative and therapeutic uses.
- Chlorinated paraffins:chemicals manufactured by chlorination of paraffin waxes. The largest application for chlorinated paraffins is as a plasticiser and flame-retardant in flexible PVC. It is also used as an extreme pressure-additive for metalworking fluids and other lubricants.
- Corrugated board:food-grade wax is applied to corrugated containers in order to provide strength and waterproofing for food packaging during transportation.
- Coatings:wax can be used to form a coating that allows oxygen to pass but not water; generating numerous applications in such diverse areas as cosmetics, food, packaging, furniture, time release properties, etc.
- Flexible packaging:Food-grade waxes and wax blends are used in laminating compounds and surface coatings to provide strength, to waterproofing, and improve appearance and moisture-vapor transmission.
- Cosmetics and pharmaceuticals:fully-refined wax is non-toxic, and many products are approved for direct use in food and personal care formulations. Waxes are widely used in the cosmetic industry in products such as lipstick, mascara, moisturizing creams and sunblock.
- Chewing gum:chewing gum base is a compound of elastomers, resin and food-grade wax to which other materials are added to produce chewing gum. Hard, high melt-point waxes are used in this application, including microcrystalline and candelilla waxes.
- Crayons:Food grade wax provides the solid structure for a crayon and, since most crayon users are young children, its non-toxic characteristics are critical.
- Fire logs:a modern convenience product, wax acts as both a binder and as fuel.
- Food:Food grade wax is used to cover certain types of cheese that would dehydrate if not properly protected. It is sprayed on citrus and other fruit to protect from oxidation and enhance appearance, and in meat and bone wraps.
- Hot melt adhesives:waxes are present in most hot melt adhesive formulations to control the viscosity of the adhesive and contribute to open time, flexibility and elongation.
- Inks:graphical printing inks include wax in their formulation as an anti-scuff agent.
- Investment casting:in the “lost wax” method of casting jewelry, and other industrial products, a wax model of the piece is made and used to create a clay mold. The wax is melted out and the clay is used to cast the final piece.
- Polishes:the application of waxes to wooden floors to improve their appearance and provide protection dates back several hundred years. It serves to retard the penetration of air and moisture, thereby increasing the life of the flooring material as well as preventing abrasion by surface grit.
- PVC:two different lubricants are used in the manufacture of polyvinyl chloride thermoplastic: internal and external; and two different types of wax are used in the lubricants. Internal lubricants are formulated to help PVC flow in the manufacturing process by forming a solution with PVC. External lubricants are not soluble in PVC and can produce a film between the PVC and its extrusion equipment.
- Tire and rubber:wax is a vital component in rubber tire formulations and is added for protection from atmospheric ozone that will “dry” unprotected rubber, causing cracking that compromises the strength of the tire. Wax creates a physical barrier between the tire surface and the atmosphere.