The method commonly used by plastic manufacturers to determine the relative viscosity of PA66 engineering plastics is the capillary viscometer method. This method is mainly divided into three steps: sample preparation, dissolution and measurement. At 25°C, a Ubbelohde viscometer is used to measure the solvent flow The ratio between the time of passing and the passing time of the solution is the relative viscosity of the PA66 engineering plastic. In the process of measurement, the required equipment includes analytical balance, dispenser, constant temperature bath, Ubbelohde viscometer with capillary inner diameter of 1.03mm; in order to ensure the accuracy and reliability of the measurement results, it is necessary to ensure the measurement equipment and The solvent meets the measurement requirements.

In the process of melting PA66 engineering plastics with concentrated sulfuric acid, temperature control is very important. If the temperature is too low, the dissolution speed of the sample will become slow; if the temperature is too high, the sample will undergo degradation reactions during the dissolution process, resulting in a relatively low sample relative viscosity; it can be seen that the dissolution temperature will affect the relative viscosity measurement results of PA66 engineering plastics Accuracy and repeatability.

(1) Polyamide (nylon)

Polyamide is applied thermoplastic engineering plastics. It is a long-chain polymer compound composed of many units with an amide group () structure. For example, nylon-66, which is polycondensed from adipic acid and hexamethylene diamine, has the structural formula

Because polyamide has light weight, excellent mechanical strength, wear resistance and good corrosion resistance, it is widely used to replace copper and other metals in the manufacture of bearings, gears, pump blades and other industries in machinery, chemical, surface, and car industries. Other parts. Polyamide has high strength after melt-spun filament, and it is mainly used as synthetic fiber and can be used as medical suture.

The influence of humidity on engineering plastics

Considering the humidity factor, when the relative humidity is greater than 80%, the moisture in the air penetrates into the material or forms a water film on the surface of the plastic, which will reduce the application function of the plastic; when the relative humidity in the air is less than 100% At 50 o’clock, the moisture contained in the plastic will evaporate into the air, which will also change the function of the plastic, making some plastics brittle and cracking.

The main effect of humidity on the function of engineering plastics is the absorption process. At present, the research on the influence of humidity on the structure and mechanical functions of plastics mainly includes two aspects. On the one hand, the material deformation and residual stress caused by the swelling caused by humidity are studied, including the use of constitutive or numerical simulation methods to study the penetration and dispersion of humidity. The structural stress and interface stress caused by uneven moisture content; on the other hand, the influence of humidity and temperature on the physical properties of plastics, such as the influence on physical functions such as strength, density, modulus, and lifespan, is discussed.

The impact of environmental humidity on the performance of plastic machinery is significant. Generally, plastics that can absorb water are sexual materials. These materials can generally form some kinds of bonds. Such bonds may be hydrogen bonds. Materials such as nylon are such materials. On the other hand, moisture does not have any effect on polyethylene or polytetrafluoroethylene, and the function of these plastics is almost lazy in terms of environmental humidity changes.

2. Application in fuel cell
The thickness of the polymer electrolyte membrane will have a great impact on the battery performance, and reducing the thickness of the film can greatly reduce the internal resistance of the battery and obtain a large power output. The macromolecular backbone structure of the perfluorosulfonic acid proton exchange membrane has good mechanical strength and chemical durability. Fluorine compounds have hydrophobic properties and water is easily discharged, but the water retention rate decreases during battery operation, which will affect the electrolyte membrane. Therefore, the reaction gas must be humidified. The humidification technology of the polymer electrolyte membrane ensures the excellent conductivity of the membrane, and also brings about problems such as the increase of the battery size, the complexity of the system, and the management of water in a low-temperature environment. Now a batch of new polymer materials, such as enhanced perfluorosulfonic acid polymer proton exchange membrane, high temperature resistant aromatic heterocyclic sulfonic acid-based polymer electrolyte membrane, nano-scale carbon fiber materials, and other new conductive polymer materials have been obtained. The attention of researchers.

3. Application in modern agricultural seed treatment
Application of polymer materials in modern agricultural seed treatment: A new generation of seed chemical treatment can generally be divided into physical packaging and use of dry and wet polymer film-forming agents to coat seeds. The seed surface coating uses a polymer film-forming agent to coat agricultural drugs and other ingredients on the seed surface. Seed physical granulation mixes seeds and other polymer materials to granulate to improve the appearance and shape of seeds and facilitate mechanical sowing. Progress in the research and development of polymer materials in modern agricultural seed treatment: polymer materials for seed treatment have gradually developed from petroleum-based polymer materials to natural and functional polymer materials. Among the more common and important types of polymer materials include polysaccharide natural polymer materials, polymer materials that maintain good membrane performance at low temperatures, super absorbent materials, temperature-sensitive materials, and comprehensive utilization of natural biological resources. Among them, seed coating agents that use sustainable biological resources concurrently attract attention.

4. Application in the electrical industry
In the electrical and electronic industries, polymers are mainly used as insulation, shielding, conductive, and magnetic materials; in the field of communication, the demand for polymer materials is with the development of society, and polymer materials are not only widely used in various terminal equipment, but also as It is used in the production of high-performance materials such as optical fibers and optical discs. my country is a big country in electrical production, and the entire industry has a large demand for polymer materials. Polymer materials are characterized by light weight, insulation, corrosion resistance, high surface quality and easy forming and processing. This is the best material for the production of various household appliances, and household appliances are essential daily necessities for people. The development of polymer materials in the electrical industry It will not stop.

5. Application in construction engineering
In the current construction projects, there are no high-molecular materials. It can be seen that the high-molecular materials products include drainage pipes, conduits, plastic doors and windows, furniture, sanitary ware, decoration materials and waterproof materials. After the 1970s, the development of low-foaming plastics and other structural materials largely replaced wood, making the use of polymer materials as structural parts in building materials to grow rapidly. At present, the cumulative use of plastic pipes in my country’s construction field is as high as nearly 20 million tons.

6. Application in agriculture
In recent years, new technologies such as mulching, greenhouses, and water-saving irrigation implemented in large areas of my country have increased the demand for polymer materials in agriculture. The use of mulching film can keep warm, moisturizing, fertilizer, moisture, weeding and insect prevention, promoting plant growth, and harvesting in advance, thereby increasing the yield of crops; greenhouses and shading nets should be used to make vegetables and flowers grow in all seasons; polymer materials Lightweight, corrosion-resistant, non-scaling, easy to transport, install and use, it is widely used in modern agricultural irrigation; in addition, ropes, laundry equipment, fishing nets, fish baskets, etc. are also made of polymer materials, which are durable and easy to clean.