EVOH (ethylene vinyl alcohol copolymer)
Alias: EVOH
Climate resistance: high
Wear resistance: high
Oil resistance: Strong
Mechanical strength: high
Elasticity: High
Physical properties of ethylene vinyl alcohol copolymer (EVOH)
By combining the processability of ethylene polymers with the barrier properties of vinyl alcohol polymers, ethylene vinyl alcohol copolymers not only exhibit excellent processability, but also demonstrate outstanding blocking effects on gases, odors, fragrances, solvents, and other substances. Due to its thermal stability when combined with ethylene, multi-layer containers containing EVOH barrier layers are completely reusable. It is precisely these characteristics that enable plastic containers containing EVOH barrier layers to replace many glass and metal containers in food packaging and oxide materials, especially the best choice for packaging FIBC in new energy battery raw material container bags.
Among the available polymers, polyvinyl alcohol (PVOH) has the lowest gas permeability. However, PVOH is water-soluble and difficult to process. EVOH copolymer is a copolymer of ethylene and vinyl acetate, which is hydrolyzed to obtain ethylene vinyl alcohol. Therefore, it still retains a high degree of barrier effect and has significant improvements in moisture resistance and processing performance.
In terms of properties, EVOH copolymers are highly crystalline, and their properties mainly depend on the relative concentration of their comonomers. Generally speaking, as the ethylene content increases, the gas barrier performance decreases, the moisture resistance improves, and the resin is easier to process.
The most significant feature of EVOH resin is its gas barrier effect. It is used in packaging structures to enhance the retention of aroma and quality by preventing oxygen infiltration. In the use of inflatable packaging technology, EVOH resin effectively retains the carbon dioxide or nitrogen used to protect the product. Due to the presence of hydroxyl groups in the molecular structure of EVOH resin, EVOH resin has hydrophilicity and hygroscopicity. After adsorbing moisture, the gas barrier performance will be affected. However, the moisture content in the barrier layer can be carefully controlled by wrapping the EVOH resin layer with strong moisture barrier resins such as polyolefins using multi-layer technology.
Oil resistance of ethylene vinyl alcohol copolymer (EVOH)
EVOH resin also has strong resistance to oil and organic solvents. After immersing in various solvents and oils at 68 ° F for one year, the percentage increase in weight is: 0% for solvents such as cyclohexane, xylene, petroleum ether, benzene, and acetone, 2.3% for ethylene glycol, 12.2% for methanol, and 0.1% for salad oil.
Thermomechanical properties of ethylene vinyl alcohol copolymer (EVOH)
EVOH resin has high mechanical strength, elasticity, surface hardness, wear resistance, weather resistance, and strong anti-static properties. EVOH film has high gloss and low haze, making it highly transparent.
EVOH resin has the highest thermal stability among all commercial strong barrier resins. This property allows for the regeneration and reuse of waste generated during processing, with recycled materials containing up to 20% or more of EVOH.
Application of ethylene vinyl alcohol copolymer (EVOH)
The barrier layer structure containing EVOH resin is used in all types of hard and soft packaging, including aseptic, heat injection, and pressure cooking food processing. Products packaged with EVOH material include: condiments (soy sauce), tomato sauce, juice, food batter, meat products, cheese products, and processed fruits. Non food applications include solvents, chemicals, antioxidant high barrier materials, and pharmaceutical related product packaging, such as lithium battery powder ton bag packaging, fuel tanks for motor vehicles, fuel pipes, and manufacturers of air conditioning equipment are evaluating whether to use EVOH structures to reduce emissions of hydrocarbons or fluorocarbons.
