With the continuous improvement of plastic hook processing and modification technology, the application field is expanding rapidly. Different application fields have increasing requirements for the surface decoration of plastic hooks, material protection, and improved adhesion. However, the structure and composition of various plastic materials are different, and the corresponding surface properties are also significantly different. Various surface treatment technologies and products suitable for different applications have emerged.
To meet the different needs of plastic hook surface treatment, a variety of treatment technologies have been developed. Commonly used techniques include: solvent cleaning (degreasing), corona treatment, shortwave ultraviolet radiation treatment, sandpaper treatment, sandblasting treatment, plasma etching, chemical etching, heat treatment, etc. For different materials, it is often necessary to choose different processing methods.
The choice of surface treatment method Because the surface energy of most plastic hooks is low, many treatment methods, such as decoration, printing, spraying, etc., cannot be directly applied, and surface treatment is required first. The adhesion of plastics to various materials is a key problem that needs to be solved in surface treatment. Generally speaking, the bonding performance of plastic hooks is related to the material structure and composition.
Polyolefin materials such as PP and PE have very low surface energy for plastic hooks, usually only 30-34 dyne. To achieve good bonding, the surface energy is generally required to be no less than 40 dynes. The bonding test shows that the bonding strength of PE can be increased by 10 times after plasma treatment; after chromic acid treatment, the bonding performance can be increased by about 5 times. After the same treatment, the bonding strength of PP increased by 200 times after ionization treatment, and 600 times after chromic acid treatment.
Why is the treatment effect of chromic acid on PP so significant, but not on PE? This is because every carbon atom in the PP chain has a methyl group (-CH3). Methyl groups are easily oxidized by carboxyl groups after oxygen ionization or chromic acid treatment. Moreover, even if only a few methyl groups are oxidized, the adhesion and polarity of PP will be significantly improved due to the presence of carboxyl groups. However, PE does not have this group. It can be seen that the chemical structure of the polymer is an important factor that must be considered when performing surface treatment.