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1. Basic characteristics of EVOH
EVOH is a hydrolysis copolymer of ethylene and vinyl alcohol and is a semi-crystalline thermoplastic resin. Its molecular structure contains hydroxyl groups and intermolecular hydrogen bonds, which results in strong intramolecular and intermolecular cohesion energy, low molecular chain flexibility, and small space probability of free movement between molecules, thus showing excellent gas barrier properties. EVOH also has good transparency, gloss, mechanical strength, stretchability, wear resistance, cold resistance and surface strength, as well as good molding processability.
2. The impact of EVOH’s gas barrier properties on sealing effect
EVOH's gas barrier property is one of its most significant features. Due to the hydroxyl and hydrogen bonding structures in the EVOH molecular chain, it is difficult for oxygen molecules to diffuse through its molecular chain segments. Compared to other plastic materials, such as polyethylene (PE) and polypropylene (PP), EVOH has a much higher gas barrier. This makes EVOH sealing films excellent at preventing oxygen from entering the interior of the package, thereby extending the shelf life of the contents.
Specifically, the gas barrier properties of EVOH can prevent the aroma components in drinks such as milk tea from escaping, and prevent external oxygen from entering, causing the drinks to oxidize and deteriorate. This characteristic makes EVOH sealing film have broad application prospects in the field of beverage packaging such as milk tea.
3. The impact of EVOH’s humidity sensitivity on sealing effect
Although EVOH has excellent gas barrier properties, it is sensitive to humidity. In an environment with high humidity, EVOH will absorb moisture, causing water molecules to plasticize EVOH, thereby reducing the rigidity of its molecular chain and making it easier for gas molecules to pass through. Therefore, the sealing effect of EVOH sealing film may be reduced in environments with high relative humidity.
This does not mean that EVOH sealing film cannot be used in humid environments. Through reasonable structural design and material formulation, the impact of humidity on the performance of EVOH sealing films can be reduced. For example, materials with better barrier properties, such as polyethylene (PE) or polypropylene (PP), can be added to both sides of the EVOH layer to form a multi-layer co-extruded structure, thereby improving the overall barrier performance and sealing effect.
4. The impact of EVOH processability on sealing effect
EVOH has good processability and can be processed into packaging materials of various shapes and sizes through injection molding, extrusion molding, multi-layer co-extrusion, casting and blow molding. This good processability allows the EVOH sealing film to maintain stable size and shape during the production process, thereby ensuring the reliability of the sealing effect.
During processing, parameters such as the melting temperature and fluidity of EVOH also have an important impact on the performance of the sealing film. If the melting temperature is too high or the fluidity is insufficient, defects in the sealing film may occur during the molding process, such as bubbles, cracks, etc., thus affecting its sealing effect. Therefore, parameters such as the melting temperature and fluidity of EVOH need to be strictly controlled during processing to ensure the quality and performance of the sealing film.
5. The impact of the transparency of Transparent EVOH Sealing Film on the sealing effect
Transparent EVOH Sealing Film has good transparency, which makes its sealing film more visually beautiful and attractive. Transparency also helps consumers observe the status and freshness of the items inside the package, thereby increasing consumers' purchase intention and trust.
It should be noted that although transparency has no direct impact on the sealing effect, packaging materials that are too transparent may allow light to directly shine on the items in the package, causing the items to deteriorate or oxidize. When designing EVOH sealing films, it is necessary to consider the balance of transparency and light-shielding properties to ensure the stability and shelf life of the contents of the package.
