Nylon is a kind of synthetic polymer material widely used in textile, engineering plastics and industrial fields, and is famous for its excellent wear resistance, fatigue resistance and mechanical strength. However, there is also a significant disadvantage of nylon material in use-strong hygroscopicity. Because its molecular structure contains a large number of amide groups (–-NHCO-–), these polar groups are prone to hydrogen bonding with water molecules, which leads to nylon's easy absorption of water in humid environment, which further affects its physical properties and service life. Therefore, how to effectively control the moisture absorption of nylon materials has become an important topic in the field of materials science and engineering.

First, the effect of moisture absorption on the properties of nylon

Nylon will cause a series of performance changes after moisture absorption. First of all, moisture absorption will lead to material size expansion, affecting its application in precision parts or textiles; Secondly, moisture will reduce the strength and rigidity of nylon, especially in high temperature and high humidity environment; In addition, long-term moisture absorption may also trigger hydrolysis reaction, leading to polymer chain breakage, thus reducing the life of materials. Therefore, solving the problem of moisture absorption is the key to improve the comprehensive properties of nylon.

Second, the strategy to control the moisture absorption of nylon

1. Chemical modification

Changing the molecular structure of nylon by chemical means is the fundamental method to control hygroscopicity. For example, nonpolar groups, such as benzene ring and fatty chain, can be introduced into nylon molecular chain to reduce the hydrogen bonding between amide groups and water molecules. In addition, the development of low moisture absorption nylon varieties, such as nylon 12, nylon 46, etc., its moisture absorption rate is significantly lower than the traditional nylon 6 or nylon 66.

2. Blending modification

Blending nylon with other low hygroscopicity resins (such as polypropylene and polyester) can effectively reduce the hygroscopicity of the whole material. By adding compatibilizer or adopting graft copolymerization technology, the uniformity and stability of the blending system can be improved, while retaining the original excellent properties of nylon.

3. Surface treatment technology

Surface treatment of nylon products, such as coating hydrophobic coating or plasma surface modification, can effectively block the penetration of water vapor. Commonly used coating materials include silicone resin, fluorocarbon resin and so on, which have good waterproof and weatherability.

4. Dry pretreatment

It is an important technological means to prevent moisture absorption by fully drying nylon raw materials before processing. Usually, hot air drying or vacuum drying equipment is used to reduce the water content to below 0.1%, so as to avoid defects such as bubbles and cracks caused by water vaporization during processing.

5. Environmental management

During the storage and use of nylon products, it is also very important to control the temperature and humidity of the environment. It is suggested that nylon materials should be stored in a dry and well-ventilated environment, and desiccant or dehumidification equipment can be used to assist moisture prevention.

Third, the future development direction

With the development of science and technology, the introduction of new nano-materials and intelligent response materials provides a new idea for nylon moisture absorption control. For example, adding inorganic fillers such as nano-silica or montmorillonite to nylon can not only improve its mechanical properties, but also effectively inhibit the diffusion of water. In addition, the development of composite materials with moisture absorption and self-regulation function is also an important direction of future research.

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As an important engineering material, nylon faces the challenge of moisture absorption, but its moisture absorption behavior can be effectively controlled by various means such as chemical modification, blending treatment, surface coating, drying technology and environmental control. With the progress of materials science, future nylon products will achieve lower moisture absorption rate and wider application prospects while maintaining their excellent properties.