What factors determine the quality of an EVA bag?

What factors determine the quality of an EVA bag?

As a common packaging material, the quality of EVA bags is affected by many factors. Here are some key factors that jointly determine the quality and performance of EVA bags:

1. Material composition
The quality of EVA bags depends first on its material composition, especially the content of ethylene-vinyl acetate (VA). EVA is a material made by copolymerization of ethylene and vinyl acetate, and the VA content is generally between 5% and 40%. The amount of VA directly affects the performance of EVA bags, such as flexibility, impact resistance, transparency, etc.

2. Molecular structure
The molecular structure of EVA also has an important influence on quality. After the introduction of vinyl acetate monomer into the EVA molecular chain, the high crystallinity is reduced and the toughness and impact resistance are improved. Therefore, the molecular structure design of EVA bags is crucial to their performance.

3. Production process
The production process of EVA bags is also an important factor. Most companies use high-pressure continuous bulk polymerization processes, including kettle method and tubular method. The differences in these processes will lead to differences in the performance of EVA products, such as shock resistance and aging resistance.

4. Processing and molding
EVA is a thermoplastic polymer that can be used for a variety of processing and molding processes such as injection molding, extrusion molding, and blow molding. EVA molding has a low processing temperature (160-200℃), a wide range, and a low mold temperature (20-45℃). These processing conditions will affect the final quality of the EVA bag.

5. Density and hardness
The density of the EVA bag is usually between 0.9-0.95 g/cm³, and the hardness is usually tested using Shore A hardness, with a common hardness range of 30-70. These physical performance parameters are directly related to the strength and cushioning performance of the EVA bag.

6. Environmental performance
EVA bags should meet environmental protection requirements, contain no harmful substances, and comply with relevant environmental standards and regulations. Environmental performance is a factor that modern consumers are increasingly concerned about when choosing products.

7. Design
The design of the EVA bag will also affect its quality. Design includes the choice of fabrics, the thickness and hardness of EVA, and the structural design of the product. Good design can improve the practicality and aesthetics of EVA bags.

8. Compression resistance and shock resistance
EVA bags should have certain compression resistance and shock resistance to protect packaged items from external impact and extrusion

9. Water resistance and corrosion resistance
High-quality EVA bags should have good water resistance and corrosion resistance, and be able to resist corrosion from seawater, grease, acid, alkali and other chemicals

In summary, the quality of EVA bags is determined by multiple factors such as material composition, molecular structure, production process, processing and molding, physical properties, environmental protection performance, design, compression resistance and shock resistance, as well as water resistance and corrosion resistance. Manufacturers need to consider these factors comprehensively to produce high-quality EVA bags.