TL;DR
Soluble wax refers to wax materials that can completely dissolve in specific liquids. These waxes fall into two main categories: water-soluble waxes (like polyethylene glycols and PEG fatty acid esters) that dissolve in water, and organic solvent-soluble waxes (including natural animal, plant, and mineral waxes as well as synthetic varieties) that dissolve in chemicals like alcohol or benzene.
Fundamental Principles of Solubility
When something dissolves, tiny pieces of it mix evenly with another substance. This happens because of how molecules interact with each other. The rule “like dissolves like” explains this well – substances with similar chemical structures tend to dissolve in each other.
For waxes to dissolve, their molecules must be able to mix with the solvent’s molecules.
Soluble Wax
Soluble waxes come in two main types based on what they dissolve in: water-soluble waxes and organic solvent-soluble waxes.
- Water-soluble waxes: Water-soluble waxes can mix with water. This is unusual for waxes since most natural waxes are made of fats and oils that don’t mix with water. These special waxes have been changed to include parts that attract water molecules.
- Organic solvent-soluble waxes: Organic solvent-soluble waxes dissolve in chemicals like alcohol, benzene, or turpentine. Most traditional waxes fall into this category. They mix well with these solvents because they share similar chemical properties.
Types of Water-Soluble Wax
Polyethylene Glycols
Polyethylene glycols (PEGs) are the most common water-soluble waxes. They’re made by linking many ethylene glycol molecules together. The longer the chain, the more solid and wax-like they become.
PEGs with molecular weights between 1,000 and 2,000 have wax-like properties. They dissolve easily in water and feel waxy to the touch.
PEG Fatty Acid Esters
PEG fatty acid esters are nonionic surfactants derived from the chemical reaction between Polyethylene Glycols and fatty acids.
While the PEG segment imparts hydrophilicity, the fatty acid segment contributes lipophilicity. The overall solubility in water is therefore dependent on the balance between these two parts, often quantified by the Hydrophile-Lipophile Balance (HLB) value.
Other Water-Soluble Polymeric Materials with Wax-Like Properties
- Hydroxypropylmethyl Cellulose (HPMC): This plant-based material forms a clear gel in water.
- Hydroxypropyl Cellulose (HPC): Similar to HPMC but dissolves in both hot and cold water.
- Hydroxyethyl Cellulose (HEC): This forms a slippery solution in water.
- Sodium Carboxymethyl Cellulose (Na-CMC): This creates thick solutions even at low concentrations.
Types of Organic Solvent-Soluble Wax
| Wax Type | Origin | Key Chemical Components | Typical Melting Point (°C) | Common Organic Solvents | Key Properties/Applications |
|---|---|---|---|---|---|
| Beeswax | Animal (Honeybee) | Esters (e.g., myricyl palmitate), free fatty acids, hydrocarbons, polyesters, free alcohols | 62-64 | Oils, warm alcohol, chloroform, ether, benzene, carbon disulfide | Cosmetics (emollient, structurant), candles, pharmaceuticals, polishes |
| Carnauba Wax | Plant (Copernicia cerifera palm) | Esters (aliphatic, hydroxycinnamic acid diesters), ω-hydroxycarboxylic acids, fatty alcohols | 82-86 | Hot ethyl acetate, hot xylene | High gloss polishes (car, shoe), coatings, cosmetics (hardener), food additive |
| Candelilla Wax | Plant (Euphorbia species) | Hydrocarbons (>50%), esters (~35%), free fatty acids, alcohols, resins | 68-73 | Acetone, chloroform, benzene, turpentine | Cosmetics (lipsticks – gloss, structure), polishes, food additive |
| Paraffin Wax | Mineral (Petroleum) | Long-chain linear alkanes ($C_{18} – C_{60}$) | 50-70 (can vary) | Non-polar solvents (toluene, xylene, hexane, petrol) | Candles, coatings (paper, food), crayons, investment casting, waterproofing |
| Microcrystalline Wax | Mineral (Petroleum) | Branched and cyclic alkanes, some linear alkanes | 60-90 (can vary) | Oils, hydrocarbon solvents | Cosmetics (oil binding, flexibility), adhesives, laminating, polishes |
| Polyethylene Wax (PE Wax) | Synthetic | Low MW polymers of ethylene ($-(-CH_2-CH_2-)-$) | 100-135 | Hot aromatic/aliphatic hydrocarbons (benzene, xylene, toluene, decalin) | Coatings, inks, polishes, plastics processing aid, hot melt adhesives, lubricants |
| Fischer-Tropsch Wax | Synthetic | Long-chain linear alkanes ($C_{20} – C_{100}$) | 95-105 | Non-polar organic solvents | Polishes, coatings, inks, adhesives, cosmetics, candles; high purity and consistent properties |
| Ethylene Vinyl Acetate (EVA) Wax | Synthetic | Copolymers of ethylene and vinyl acetate | Varies with VA content (e.g. 47°C for 40% VA) | Toluene, xylene, TCE, THF, MEK, n-butanol (solubility increases with VA content) | Adhesives (hot melt), coatings, plastic modification, wax blending for flexibility and adhesion |
Natural Waxes
These are derived from living organisms or geological sources.
- Animal-Based Waxes: Produced by animals.
- Plant-Based Waxes: Obtained from various parts of plants, where they often serve as protective coatings.
- Mineral Waxes: These are typically derived from fossil fuels (petroleum or coal/lignite) or other geological deposits.
Synthetic Waxes
These are manufactured through various chemical processes.
- Polyethylene Wax (PE Wax): Low molecular weight polymers of ethylene, characterized by their lubricity and resistance.
- Polypropylene Wax (PP Wax): Low molecular weight polymers of propylene.
- Fischer-Tropsch Wax: Synthetic hydrocarbons produced from carbon monoxide and hydrogen via the Fischer-Tropsch process; typically linear alkanes.
- Ethylene Vinyl Acetate (EVA) Wax: Copolymers of ethylene and vinyl acetate, with properties varying based on the vinyl acetate content.
- Amide Waxes: Synthesized from fatty acids and amines or diamines, such as ethylene bis-stearamide (EBS).
