Among them, PA has the advantages of excellent mechanical properties, corrosion resistance, oil resistance, heat resistance, high modulus, etc. Its enhancement and flame retardant modification can significantly improve its heat resistance, modulus dimensional stability, and flame retardancy. Used in industries such as automobiles, electrical and electronic, and power tools. The modified PA series materials include laser engraving, flame retardant, abrasion resistance, antistatic, carbon fiber modification, injection molding grade magnetic permeability, wading products, automobile use, etc.

Plastic modification is used, so what is plastic modification?

Plastic modification is the use of general resins through physical, chemical, and mechanical methods to improve or increase their functions, and use them under special environmental conditions in terms of electricity, magnetism, light, heat, aging resistance, flame retardancy, and mechanical properties. Function.

When it comes to plastic modification, many people think of filling, blending, fiber reinforcement, etc., but few people have a comprehensive understanding of plastic modification technology and methods. In fact, the commonly used methods of plastic modification are as follows:

1. Add modification

(1) Add small-molecule inorganic or organic matter

A modification method in which small-molecule inorganic or organic substances are added to the polymer (resin) to obtain a certain expected performance through physical or chemical action. This method is the earliest modification method. Its modification effect is obvious, the process is simple, and the cost is low, so it is widely used. It is believed that all those who have done graduation projects in colleges and universities will come into contact with and understand this method.

(2) Adding polymer substances

This method is also known as blending modification, and its main method is to mix one or more other resins (including plastics and rubber) into a resin to change the original resin properties. Since the blended and modified composite systems are all high-molecular substances, their compatibility is better than the system with small molecules added, and the modification does not have much impact on the other properties of the original resin at the same time. The common polymer alloys are the modified products of this method. Blending modification is the most effective way to develop new polymer materials, and it is also the main way to achieve high performance and refinement of existing plastic varieties.

Reducing the cost of plastics has always been the pursuit of manufacturers, so some modification methods will be used to reduce costs. The main methods include adding fillers and blending cheap resins. Of course, it is hoped that suppliers can reduce costs while not forgetting the need for performance.

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.

In the process of producing PA66 engineering plastics, the more commonly used polycondensation methods include sequential polycondensation and intermittent polycondensation. The successive polycondensation method can be divided into horizontal tube type decompression continuous polycondensation, vertical tube type continuous polycondensation, and “five major device” type continuous polycondensation according to the different equipment capabilities used for polycondensation. The application is more common. The “five major” type sequential polycondensation method means that nylon 66 material is made into PA66 engineering plastics with good performance after passing through the evaporator, preheater, tubular reverberator, flash evaporator and finishing reverber in sequence.

The intermittent polycondensation method and the successive polycondensation method produce PA66 engineering plastics in the same principle, and the reaction conditions are basically the same. Only the reaction process in the intermittent method (such as heating, high-pressure polymerization, decompression, evacuation, etc.) needs to be completed intermittently in the high-pressure reactor. The processes of pre-condensation, flash evaporation, and finishing polycondensation in successive polycondensation are successively carried out in different connected equipment. That is to say, the polycondensation process of PA66 engineering plastic in the batch method changes with the change of the response time, while the reaction process in the continuous method changes with the change of the spatial orientation. These two polycondensation methods have their own advantages and disadvantages. Ask to choose.

(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 method commonly used for engineering plastics 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. The detailed measurement principle is to dissolve engineering plastic slices into 96% concentrated sulfuric acid. In, at 25°C, a Ubbelohde viscometer is used to measure the flow time of the solvent and the flow time of the solution. The ratio of the two times is the relative viscosity of the PA66 engineering plastic. In the process of measurement, the instruments and equipment that need to be prepared include analytical balances, dispensers, constant temperature baths, and Ubbelohde viscometer with capillary inner diameter of 1.03mm; the solvent that needs to be prepared is concentrated sulfuric acid with a concentration of 96%, in order to ensure the measurement results For accuracy and reliability, it is necessary to ensure that the measurement equipment and solvent meet the measurement requirements.

In the process of blending 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 slow down; if the temperature is too high, the sample will have a degradation response during the dissolution process, resulting in a low relative viscosity of the sample; it can be seen that the dissolution temperature will affect the relative viscosity measurement results of PA66 engineering plastics Accuracy and repeatability.

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.

There are two ways to improve the flame retardancy of PA66 engineering plastics: one is to use increased flame retardants, and the other is to use reactive flame retardants. The increased flame retardant is added to the PA66 resin, and then mechanical blending is used to fuse the two. Physically dispersing the flame retardant in the PA66 resin matrix is ??the primary method of flame retardant modification. The advantages of this method are convenience, wide applicability and significant modification effect. According to people’s experience in the manufacture of PA66 engineering plastics, commonly used increased flame retardants include phosphorus flame retardants, nitrogen flame retardants, halogen flame retardants, inorganic flame retardants and so on.

Two methods for the flame retardant modification of PA66 engineering plastics are to combine flame retardants as reactive monomers to the PA66 macromolecular chain to make them the flame retardant components in the PA66 structural unit. The advantages of this modification method are good stability, long-lasting flame retardant effect and little impact on other properties of the material, and it will not present flame retardant evaporation and migration problems; but this method has the complex processing technology and high modification cost. Defects are subject to certain constraints in the actual production and manufacture of PA66 engineering plastics. The commonly used reactive flame retardants are mainly phosphorus-containing polyols and halogenated acid anhydrides, such as bis(4-carboxyphenyl)phenyl phosphorus oxide and bis(hydroxyethyl)methyl phosphine oxide.

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.

Innovation drive has been established as one of the two major development strategies of the petrochemical industry during the 13th Five-Year Plan period, and new chemical materials have also been established as one of the five key areas of the petrochemical industry’s scientific and technological development guidelines. The federation assisted in organizing the national key special research and development projects of polymer materials, formed a special nylon engineering plastics alliance, and identified a number of technological innovation demonstration enterprises in the field of polymer materials. In the future, the innovation in the field of polymer materials should closely follow the new progress in the international science and technology field and the new changes in industrial development, aim at the high-end differentiation and specialization of products, strengthen the construction of an innovation system with enterprises as the main body, and focus on conquering a group of ” “Stuck neck” technology, shortcoming technology, disruptive technology, build a number of high-quality, high-level public innovation platforms and innovation alliances, strengthen the cultivation and growth of innovative talents and innovative teams, and at the same time, face new energy and high-end manufacturing countries Focus on key projects and strategic emerging industries, highlight new chemical materials and specialty chemicals, increase innovation, and achieve sustainable development.

02|Green development is the fundamental policy of sustainable development

In the context of the deep adjustment of the global petrochemical industry structure, green development has become the main direction of the technological revolution and the optimization and upgrading of the industrial structure, and an important means to promote supply-side structural reform and high-quality development. The Petrochemical Federation cooperated with the Development and Reform Commission and the Ministry of Industry and Information Technology to study and formulate the “Guiding Opinions on Promoting the Green Development of the Petrochemical Industry”, and issued the “Petrochemical Industry Green Development Action Plan” to the entire industry. , We should also continue to deepen the construction of the green manufacturing system, increase the cultivation of typical green development demonstrations, and actively adopt advanced green technology to implement clean transformation. For example, the earliest traditional material of polyvinyl chloride, in view of my country’s resource endowment and the increasing dependence on foreign oil, it is impossible for developed countries to adopt the ethylene route. The calcium carbide process will continue to play a long-term role, facing the implementation of international conventions and elimination For the problem of mercury pollution, low-mercury catalysts have been adopted, and the research and development of mercury-free processes are also speeding up. The recycling and reuse of calcium carbide slag has also achieved good results. Through technological upgrading and transformation, the source control and process of green development have been realized. Progress is being made.

The United States, Germany, Japan, the United Kingdom, the Netherlands, Brazil and other developed countries and regions with rich biological resources attach great importance to and accelerate the development, industrialization and application of biodegradable materials. This is an important future for the sustainable development of polymer materials; Fermentation and synthesis of polyhydroxy fatty acid esters and biodegradable polyamides, polyurethanes, polyesters and other products have achieved good results and have been widely recognized.

03|Being international first-class is an important measure to achieve the goal of becoming a strong country

my country has been a major producer and consumer of polymer materials for many years, but there has always been a big gap with developed countries and multinational companies. As a leading industry, polymer materials are the first choice for sustainable development in the future. In accordance with the goal of cultivating world-class companies with international competitiveness, polymer materials companies should choose global competitive multinational companies such as Dow, DuPont, Mitsubishi, LG, and Covestro. They can also learn from Solvay and Sabic. , DSM, INVISTA and other companies have successfully transformed and upgraded their practices and experience, strengthened benchmarking with world-class companies, highlighted their main businesses and advantages, and made great efforts to strengthen their main businesses and core competitiveness.

04|Grasping new technology and new trends is an important direction for sustainable development

For example, ExxonMobil’s new process for direct production of chemicals from crude oil is the only industrialized plant in the world. It has been in operation for 5 years. A flash tank is added between the convection section and the radiant section of the cracking furnace. The chemical output rate varies from 50% to 70% due to different raw materials. It processes 5.796 million tons of light crude oil and produces 3.115 million tons of chemicals, of which the output of olefins is as high as 2.039 million tons, and then produces metallocene polyethylene and high-impact, homo-polypropylene.

Then there are a number of new technologies under development, such as direct synthesis gas to olefins, methane direct to olefins, and my visit to the Southwest Research Institute in the United States to learn about the hydrocarbons they are developing to produce polymers through membrane reactors, etc. Disruptive technologies are directly related to polymer materials, and we should pay close attention to their progress and grasp it.