Several anti-aging methods commonly used in plastic materials
2021-12-14
In fact, polymer materials have become a necessity in every aspect of modern life. The latest progress in production and processing has further broadened the application range of plastics. In some applications, polymer materials have even replaced other materials. Such as glass, metal, paper and wood.
However, the structural characteristics and physical state of the polymer material itself and the external factors such as heat, light, thermal oxygen, ozone, water, acid, alkali, bacteria and enzymes received during use, make it difficult to Performance degradation or loss occurs, such as yellowing, relative molecular weight reduction, product surface cracking, loss of gloss, and more serious, resulting in a significant decrease in mechanical properties such as impact strength, tensile strength and elongation, which affects polymer materials Normal use.
This phenomenon is referred to as aging for short. Aging may occur at all stages of polymer material synthesis, storage, processing, and final application. It can lead to the end of the service life of the material and a large amount of waste, resulting in a great waste of resources and serious environmental pollution. The aging of polymer materials during use is more likely to cause huge disasters and irreparable losses.
Therefore, the anti-aging of polymer materials has become a problem that the polymer industry has to solve. In fact, the anti-aging of polymer materials is an important issue in polymer chemistry. At present, there are four main methods to improve and enhance the anti-aging performance of polymer materials:
1. Physical protection (such as thickening, painting, outer compounding, etc.)
The aging of polymer materials, especially photooxidative aging, first starts from the surface of the material or product, showing discoloration, chalking, cracking, and decreased gloss, and then gradually deepens into the interior. Thin products are more likely to fail earlier than thick products, so the service life of the products can be prolonged by thickening the products.
For products that are prone to aging, you can coat or coat a layer of weather-resistant coating on the surface of the product, or compound a layer of weather-resistant material on the outer layer of the product, so that a protective layer is attached to the surface of the product, thereby Delay the aging process.
2. Improve processing technology
Many materials also have the problem of aging during the synthesis or preparation process. For example, the influence of heat during polymerization, thermal oxygen aging during processing, and so on. Correspondingly, the effect of oxygen can be mitigated by adding deoxygenation devices or vacuuming devices during polymerization or processing.
However, this method can only guarantee the performance of the material when it leaves the factory, and this method can only be implemented from the source of the material's preparation, and cannot solve the problem of aging in the process of reprocessing and use.
3. Structural design or modification of polymer materials
Many polymer materials have very aging groups in the molecular structure, so through the design of the molecular structure of the material, replacing the aging groups with non-aging groups can often achieve good results.
4. Add anti-aging additives
At present, an effective way and a common method to improve the aging resistance of polymer materials is to add anti-aging additives, which are widely used due to their low cost and no need to change the existing production process. There are two main ways to add these anti-aging additives:
(1) Direct addition method of additives
That is, anti-aging additives (powder or liquid) and resin and other raw materials are directly mixed and stirred, and then extruded, granulated or injection molded. Because of its simplicity and ease, this addition method is widely used by the majority of pumping and injection molding plants.
(2) Adding method of anti-aging masterbatch
Manufacturers that have higher requirements for product quality and quality stability, more often use the method of adding anti-aging masterbatch during production.
Its application advantage is that the anti-aging additives are firstly pre-dispersed during the preparation of the masterbatch, then in the later material processing process, the anti-aging additives are secondarily dispersed to achieve the uniform dispersion of the additives in the polymer material matrix The purpose of this is not only to ensure the quality stability of the product, but also to avoid dust pollution during production, making the production more green and environmentally friendly.
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