Common shockproof packaging materials and performance requirements (on)

The role of shockproof packaging is mainly to overcome the impact of shock and vibration on packaged goods. The method used to overcome the impact is usually called the buffer material; the method used to overcome the vibration is usually called anti-vibration, vibration isolation, and the materials used are called shockproof materials and vibration isolation materials. Cushioning materials, vibration-proof materials, and vibration-isolation materials are collectively referred to as shockproof materials. Shockproof packaging is a method that takes into consideration the impact of shock and vibration. The use of shockproof materials plays a very important role and is one of the keys to shockproof packaging.
I. Classification of Earthquake Resistant Materials Earthquake resistant materials are widely used in protective packaging for precision instruments, electronic products, weapons, glass instruments, handicrafts, ancient artifacts, various shaped fragile articles, certain chemical products and mechanical products, etc. There are many kinds of natural, synthetic, shaped, amorphous and so on.
1. According to the appearance of points can be roughly divided into two categories, namely amorphous shockproof materials and shaped shockproof materials.
(1) Amorphous cushioning materials, mainly crumbs, filaments, granules, small pieces or small strips, etc., are shaped to fill them around the product. The amount of amorphous buffer material in the shipping package has a tendency to decrease compared to the size of the cushioning material.
(2) Shaped cushioning materials, mainly composed of padding angles, spacers, and liners of various materials, are used to separate, fix or enclose the products. Such as molding pulp, corrugated board liners, paper cotton materials, mats, springs, synthetic materials.
2. According to material classification (1) Cellulose, such as paper scraps, pulp, rice straw, wheat straw, synthetic fiber, etc.
(2) Animal fibers, such as pigs, goats, and felt.
(3) Mineral cellulose, such as glass fiber, asbestos, mineral wool, etc.
(4) Air bubble structure, such as natural rubber, synthetic rubber, foam, bubble plastic film, bubble sheet, foam sheet and in-situ foam material.
(5) Paper, such as corrugated board, slotted partitions, cellophane linings, old newspapers, and crepe paper.
(6) Shockproof devices such as springs, suspension devices, etc.
Second, the performance requirements of shockproof materials As mentioned above, the role of shockproof materials is to ease the impact of the contents of the package in the transport, loading and unloading in the shock and vibration external force, so the shockproof material must have its specific properties.
1. Absorbing Impact Energy The shock-absorbing material absorbs impact energy, which is the property that when the packaged product is impacted during transportation, loading and unloading, the external impact force can be attenuated to a level that does not damage the product. When the product compresses the shockproof material to a certain extent, due to the elasticity and "stickiness" of the shockproof material, the energy when the product falls is reduced, that is, the impact energy is absorbed. For the same material, the greater the amount of deformation of the material, the greater the impact energy absorbed. It is generally desirable to use a material that absorbs a large amount of energy as a shock-proof packaging material, but a material that does not have a high impact-absorbing force is suitable under all circumstances. When the external impact force is small, the corresponding acceleration is small, so it is appropriate to produce a soft material with a large deformation; in the case of a large external impact force, a harder material is appropriate. Therefore, a material with an appropriate energy absorption does not mean that it has a large absorption of energy, but it means that it has a greater ability to absorb energy for impacts of the same size.
2. Can absorb vibration external force, make it decay In the transportation process, when the vibration frequency of the truck or other transportation tool is close to the natural frequency of the packaged object, resonance occurs. Resonance will damage the product, so the buffer packaging material must have a viscosity that can attenuate the resonance without increasing the vibration amplitude due to common vibration.
3. Earthquake-resistant materials with good resilience should have high resilience (ie, resilience) and low modulus of elasticity, and be deformed when subjected to an external force; when the external force is removed, it can be restored to its original shape and be subjected to external forces again. There is also the ability to deform when acting. This ability to restore the original shape is called resilience. Resilience is divided into two categories: static recovery (by static pressure) and dynamic recovery (impact and vibration). The shockproof material has good resilience and it can ensure sufficient close contact with the package, even if Materials with good resistance are also not suitable for shockproof materials if they have poor resilience.
Bulk or crumbs of amorphous cushioning material, due to the large gaps between the pieces, so the recovery is very small, can produce permanent deformation after impact, not suitable for use in the more demanding shockproof packaging, It can be used in a shock-proof package that drops once, such as airdrops, and it is effective to use it.
4. Temperature and humidity stability materials are subject to temperature and humidity. As a shockproof material, vibration resistance should be maintained within a certain range of temperature and humidity. In the range of temperature and humidity of the material, shock and vibration absorption The buffering performance such as resilience is smaller as the temperature and humidity of the environment change. In other words, in the widest range of temperature and humidity, the change in the cushioning properties of the material should be as small as possible.
For thermoplastic shockproof materials, temperature and humidity stability is particularly important. At low temperatures, the thermoplastic shockproof material will harden and the cushioning capacity will decrease. When subjected to vibration or impact, the inner package will generate greater acceleration. The minimum operating temperature for thermoplastics can be found in Table 8-7.
Table 8-7 Minimum use temperature of several buffer materials

5. Hygroscopicity of materials with low moisture absorption has two hazards, one is to reduce the shockproof performance; the second is to cause the rust of the metal products being packaged and the deformation and deterioration of non-metal products. Paper is hygroscopic and not suitable for packaging metal products. Continuous foaming foams are also prone to water absorption and are not suitable for packaging of metal products. Non-continuous foamed foams are not easy to absorb water and are suitable for metal packaging.
(To be continued)