What Is Vinyl Acetate Monomer (VAM)?
Vinyl acetate monomer, abbreviated VAM, is an organic compound registered under CAS number 108-05-4 with the molecular formula C4H6O2. It is the vinyl ester of acetic acid, a colorless liquid with a characteristic sweet odor and a low flash point. VAM is soluble in most organic solvents, including chlorinated solvents, but has only limited solubility in water.
Because it contains a reactive carbon-carbon double bond, VAM polymerizes readily. Commercial material is therefore supplied inhibited, normally with hydroquinone, so that it remains stable during storage and transport and does not begin to polymerize before it reaches the reactor.
Why VAM Is a Versatile Reactive Monomer
The double bond in VAM allows it both to homopolymerize into polyvinyl acetate and to copolymerize with a broad family of partners, including acrylate esters, ethylene, vinyl chloride and maleate esters. Each copolymer has its own balance of hardness, tack, flexibility and water resistance, so a single feedstock supports a very wide product range.
High reactivity: fast, controllable polymerization in bulk, solution and emulsion processes.
Copolymerization flexibility: grades can be tailored for adhesion, softness, film formation or water resistance.
Emulsion friendly: water-based latex systems are produced directly from VAM without special handling.
Good adhesion and flexibility: bonds hold under mechanical stress and movement.
Durability: VAM-based films resist moisture, ultraviolet light and temperature cycling.
Cost efficiency: VAM is one of the most economical reactive monomers available at industrial scale.
Physical and Chemical Properties
| Property | Typical value |
|---|---|
| CAS number | 108-05-4 |
| Molecular formula | C4H6O2 (CH3COOCH=CH2) |
| Molar mass | About 86.09 g/mol |
| Appearance | Clear, colorless liquid |
| Odor | Characteristic sweet odor |
| Density at 20 °C | About 0.934 g/cm³ |
| Boiling point | About 72.7 °C |
| Melting point | About −93.5 °C |
| Flash point | About −8 °C (closed cup) |
| Solubility in water | Limited; miscible with most organic solvents |
| Inhibitor | Hydroquinone, typically a few parts per million |
| Transport classification | UN 1301, class 3 flammable liquid |
These values represent standard commercial material and provide a general reference for storage, dosing and process design.
Benefits in Adhesives, Coatings and Polymers
Adhesives and sealants. Polyvinyl acetate homopolymer emulsions are the workhorse of woodworking, packaging and paper converting. Copolymers with ethylene or acrylates raise water resistance and adhesion to difficult substrates such as plastic films and coated papers.
Paints and coatings. VAM-based latices form the binder in interior and exterior architectural paints, where they deliver good pigment binding, low odor and resistance to UV light, moisture and temperature change.
Redispersible polymer powder. Spray-dried VAM copolymer powders improve adhesion, flexibility and water retention in dry-mix mortars, tile adhesives and renders.
Films and laminates. Modified VAM copolymers are used in laminated safety glass interlayers and in flexible packaging films, where clarity, toughness and long-term stability are required.
Textiles and paper. VAM binders and sizes give strength, hand and printability to nonwovens, textiles and coated paper grades, and they are compatible with water-based formulations.
Storage, Inhibition and Safe Handling
VAM is a flammable, readily polymerizable liquid and must be treated accordingly. Because its flash point is about −8 °C, vapors can form ignitable mixtures at ordinary ambient temperatures; storage tanks and transfer lines should be grounded and bonded, and all sources of ignition kept away. Vapors are heavier than air and can travel to distant ignition points.
Inhibitor must be maintained within specification at all times, and inventory should be rotated so that material is not stored for extended periods or exposed to excessive heat or sunlight, which can consume the inhibitor and trigger runaway polymerization. Tanks should be blanketed with inert gas where the process allows, and temperature must be monitored. For handling, use chemical-resistant gloves, goggles and, where vapor concentrations may be elevated, respiratory protection. Contact with eyes, skin and the respiratory tract should be avoided, and all work should be carried out with good ventilation and local exhaust.
Frequently Asked Questions
Q: What is VAM used for?
VAM is polymerized into polyvinyl acetate and a wide range of copolymers used in adhesives and sealants, paints and coatings, redispersible polymer powder for dry-mix mortars, laminated safety glass interlayers and flexible packaging films.
Q: What is the CAS number of vinyl acetate monomer?
Vinyl acetate monomer has the CAS registry number 108-05-4 and the molecular formula C4H6O2.
Q: Is VAM soluble in water?
VAM has only limited solubility in water, but it dissolves readily in most organic solvents, including chlorinated solvents.
Q: Why is VAM inhibited with hydroquinone?
The reactive double bond makes VAM prone to unwanted polymerization, and hydroquinone stabilizes the monomer during storage and transport so it stays within specification until it is used.
Q: What are the benefits of VAM in adhesives?
VAM-based polymers provide strong adhesion, good flexibility and durability, which makes them reliable for bonds that face mechanical stress and outdoor exposure.
Q: Is VAM flammable?
Yes. VAM has a flash point of about −8 °C, so it is highly flammable and must be handled away from ignition sources, with proper grounding and bonding of equipment.
Q: What is the boiling point of vinyl acetate monomer?
VAM boils at about 72.7 °C at atmospheric pressure, and it has a molar mass of about 86.09 g/mol and a density of about 0.934 g/cm³ at 20 °C.