Factors Affecting Barrier Properties of Polymer Materials

In the previous chapter, we introduced the permeation mechanism. In this issue, we will introduce the factors that affect the barrier properties of polymer materials. Reminder: It is recommended to read the first three chapters first, which is helpful for reading this chapter.

First of all, there are two main factors affecting the barrier properties of polymer materials.

1.The permeability of the permeate to the packaging material depends on the type of the permeate (molecular volume, shape and polarity), the structure and performance of the polymer material, and the interaction between the permeate and the polymer material (the polarity is similar and compatible). The actual permeation process is usually affected by these three factors. Since the types of permeates and their interactions with materials are relatively complex, here we only analyze the impact of the structure and properties of polymer materials on the barrier properties of packaging.

2.Factors affecting the barrier properties of packaging materials include the chain structure, phase structure, crystallinity, chain orientation and stacking state of the material itself. In addition, the difference in the packaging process will also affect the barrier properties of the final material.

In addition, different material processing and molding processes also affect the barrier properties of materials. Selecting polymers with different characteristics and adopting appropriate processing methods can obtain barrier materials with excellent comprehensive properties. For example, the barrier properties of LLDPE and LDPE are lower than that of HDPE. When extruding single-layer tubes, LLDPE, LDPE and HDPE can be physically blended to obtain a tube package with certain barrier properties and easy heat sealing. Another example is EVOH, which is a copolymer of ethylene/vinyl alcohol, a crystalline polymer with a chain structure, which combines the good processability of polyethylene and the extremely high gas barrier properties of polyvinyl alcohol. The presence of polar vinyl alcohol segments in the molecular chain makes it also have good barrier properties to non-polar solvents such as hydrocarbons, and the presence of non-polar vinyl segments can improve its barrier properties to polar solvents such as water. However, there are hydroxyl groups in the molecular structure of EVOH resin. EVOH resin is hydrophilic and hygroscopic. After absorbing moisture, the gas barrier performance will be affected. Therefore, it is necessary to use multi-layer technology to wrap the EVOH resin layer with a strong moisture barrier resin such as polyolefin to make a composite material with excellent comprehensive barrier properties.

In this chapter, the factors affecting the barrier properties of polymer materials have been introduced. The next chapter will explain the application of barrier materials in cosmetic packaging, which is also the last chapter of this series. Welcome everyone to pay attention to us, we are a professional manufacturer integrating production and sales.

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