How to achieve the barrier properties of vinyl acetate in food packaging films such as EVOH?

How to achieve the barrier properties of vinyl acetate in food packaging films such as EVOH?

With the continuous improvement of food preservation and packaging material performance requirements, the barrier performance of food packaging film has become the focus of attention. Among them, the application of vinyl acetate in EVOH (ethylene-vinyl alcohol copolymer) materials is favored because of its excellent barrier properties. This article will analyze in detail how the barrier properties of vinyl acetate in EVOH are achieved.

1. Vinyl acetate and EVOH relationship

EVOH is an ethylene-vinyl alcohol copolymer, and its molecular structure includes an ethylene segment and a vinyl alcohol segment. Among them, the ethylene chain segment provides the thermoplastic and processing properties of the material, while the vinyl alcohol chain segment gives the material excellent barrier properties. Vinyl acetate plays an important role in the formation of EVOH, because it can be converted into vinyl alcohol through chemical reaction, and then participate in the copolymerization reaction to produce EVOH. This structural feature makes EVOH have good gas barrier properties and water vapor barrier properties in food packaging films.

2. EVOH barrier properties of the source

The barrier properties of EVOH are mainly derived from the high polarity and high crystallinity of its molecular structure. The high polarity of the vinyl alcohol chain segment makes the intermolecular force stronger, thus forming a dense structure, which effectively prevents the penetration of oxygen, carbon dioxide and water vapor. The high crystallinity of the vinyl alcohol segment further improves the mechanical strength and thermal stability of the material, thereby enhancing its barrier properties.

3. Co-extrusion technology applications

In actual production, EVOH is usually compounded with other materials by co-extrusion technology to form a multi-layer packaging film. For example, compounding polyethylene (PE) or other thermoplastic materials on both sides of the EVOH layer can effectively improve the mechanical properties and heat sealing properties of the film while maintaining the barrier properties of EVOH. This multilayer structure design allows the barrier properties of EVOH in food packaging films to be fully exploited.

4. EVOH and other barrier material combination

In addition to co-extrusion technology, EVOH can also be combined with other barrier materials (such as aluminum foil, silica, etc.) to form a more efficient barrier layer. For example, the oxygen barrier property and the moisture barrier property can be further improved by coating a silicon dioxide nanoparticles on the surface of the EVOH film. The development of this composite material not only improves the barrier properties of EVOH, but also reduces the production cost.

5. EVOH surface modification and filling modification

In order to further improve the barrier properties of EVOH, it can also be optimized by surface modification and filling modification. For example, by chemical grafting or plasma treatment, more polar groups can be introduced on the surface of EVOH, thereby enhancing its binding force with the barrier layer. By adding nano-scale fillers (such as montmorillonite, calcium carbonate, etc.) to EVOH, its rigidity, strength and barrier properties can be further improved.

6. Summary

The barrier properties of vinyl acetate in EVOH are achieved by the high polarity and high crystallinity of its molecular structure. Co-extrusion technology, combination with other materials and surface modification methods can further improve the barrier properties of EVOH, making it play an important role in food packaging films. As an environmentally friendly and excellent packaging material, EVOH has broad application prospects, and future research and development will further promote its application in the field of food packaging.