Thermoset Resin mould

 

1. The glass transition temperature 

 

Cured thermosetting resins are linear amorphous polymers, linear amorphous polymers due to temperature change (in a certain stress) can present three kinds of mechanical condition, that is glassy, high elastic and viscous flow state . When the temperature is high, macromolecules and chain segments can be thermal motion. Then a viscous polymer flow by external force, the molecular deformation caused by sliding each other; remove the external force, you can not be reinstated, so deformation is irreversible, such deformation as the viscous flow deformation or plastic deformation, there This is called flow temperature deformation temperature Tf, this state became viscous flow (also known as plastic state). If the polymer is viscous flow decreased temperature. Viscosity also increases, and finally was elastic state, plus the stress generated when the slow deformation, and can slowly discharge after external force be reinstated, and this state is called high-elastic state. When the temperature continues to drop, becoming more and more hard polymer, the external force produced only a small deformation in this state called the glassy state. Cured thermosetting resin is used in the glass state, so the Tg as high as possible, is to measure an indicator of heat resistance resin. Such as: 898 high-cross-linked epoxy vinyl resin Tg = 190 ℃, the high heat resistance, in the flue gas desulfurization industry can bear 200 ℃ high temperature. 

 

Glass transition temperature measurement methods commonly used are: thermal mechanical analysis (TMA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) of three. Their principle of different testing methods, so the disparity in test results can not be compared. 

 

In addition, after annealing (the heating treatment) of resin, glass transition temperature will increase, this is because the products of the internal stress has been eliminated through annealing temperature of the reason. 

 

2. Heat distortion temperature and heat-Martin 

 

2.1 Heat distortion temperature 

 

Heat distortion temperature (in full load heat distortion temperature, the English abbreviation: HDT) refers to the dip in the 120 ℃ / h heating rate of the thermal conductivity of the liquid heating medium in a certain size requirements imposed rectangular resin specimens load (1.81N / mm2 or 0.45 N/mm2), the deformation of the sample to reach the midpoint of the sample height with the provisions of the corresponding value of the temperature. To note: the load of different heat distortion temperature set value is different, and are not comparable, the measured thermal deformation temperature must be pointed out that the values used in load requirements (ie, the criteria used). Heat distortion temperature is a measure of plastic (resin), the main indicator of heat resistance, and now the world's most plastic (resin) product standards, there are heat distortion temperature of the indicators as quality indicators, but it is not the highest use temperature, maximum temperature is the force should be based on product requirements and the usage of integrated factors. 

 

Heat distortion temperature of the standard measurement of many domestic now common are: China National Standard (GB), American Society for Testing and Materials Standards (ASTM), International Organization for Standardization standards (ISO), European standards, as required by the standard test method, unit systems differ, so the test results are also different. For example: a well-known foreign brands of phenolic epoxy vinyl ester resin ASTM heat distortion temperature test typical :149-154 ℃, GB measured value: 137 ℃; 898 GB resin measured: 155 ℃. 

 

2.2 Martin Heat 

 

Martin Heat test method for testing plastic (resin) heat resistance of the methods. Proposed in 1924 by Martin, 1928 for Germany, Bakelite formal test. Later, some other hard plastic is also used in the test methods. It is used in Europe and the former Soviet Union more widely. 1970, China has issued national standards for the test method, and has become the early establishment of plastic (resin) test methods in a national standard, so use a long history in China. 

 

Martin is the sample heat-resistant temperature of a certain bending moment, the temperature environment in a certain constant velocity deformation occurs when the required temperature during deformation. 

 

2.3 The heat distortion temperature and heat of Discrimination Martin 

 

Heat distortion temperature and heat are the Martin test plastic (resin), heat resistance one way, but because of the essential differences between test methods, no comparable, there is no change in the formula. 

 

As Martin put heat temperature is measured cantilever bending moment, the operation is not easy; and values imposed by the large bending moment, so after a lot of plastic in the initial load deflection on the very substantial, and thus the scope is limited generally more used to hard plastic. In addition, it uses air as heat transfer medium temperature cabinet uneven distribution of heat on the sample slowly, thus heating rate must be controlled. Unless stopped, so this method has not been adopted in many countries, in our country have been gradually eliminated. 

 

Therefore, the inspection of plastic (resin), heat resistance, you can not use Martin's heat distortion temperature compared with the heat. Also note that while they are not plastic (resin) is the highest temperature, plastic (resin) of the maximum temperature should be based products, pressure, and use requirements and other factors to determine. In addition, the thermosetting resin after annealing, which is our daily said heating processing, heat distortion temperature and Martin will heat increased, the general annealing can improve the heat distortion temperature of 10 ℃, which shows in the daily use of thermosetting resin after heating treatment is still very necessary. 

 

3. Corrosion temperature: 

 

As the resin than fiberglass and metal, light weight, high strength, good corrosion resistance, good transient performance and ultra-high temperature lower than the metal prices, has been applied in related fields. 8mm common carbon steel, such as 0.1% in the concentration of sulfur dioxide and humid environment, only 1-3 months can be through corrosion, and corrosion resistant layer of 6mm 890 resin, fiberglass can be maintained 10 years of life. So all kinds of resin-based composite materials extensively used in various corrosion occasions, especially heavy-duty situations. This involves an important concept: corrosion temperature. 

 

Corrosion-resistant resin temperature generally refers to a specific environment (a specific corrosive medium, the concentration of a specific corrosive medium), the resin can withstand the highest temperature. The temperature is different from heat distortion temperature, glass transition temperature and thermal insulation levels, for example: vinyl resin, heat distortion temperature of 898 155 ℃, the glass transition temperature of 190 ℃, thermal insulation level of C-level (Chinese standard), wet desulfurization process, the mixed gas temperature of 160-200 ℃ imported about components in the system have to bear the temperature of the alternating moments of potential heat damage and corrosion by-products generated strong. Table 2.1 is 898 corrosion-resistant resin extract using the thermometer. 

 

Not difficult to see from the above table, the total temperature corrosion have a specific media use, not use anti-corrosion medium temperature does not hold. Conditions in different media, the same corrosion-resistant resin temperature is usually different. It also requires anti-corrosion resin used, be sure to pay attention to corrosive conditions. However, the current market there are some scientific argument, and even directly write the description in the resin products, such as: "How many degrees the temperature of resin used; the use of temperature resistant resin, the number of degrees; heat distortion temperature is the number of degrees corrosion-resistant temperature is the number of degrees. "These claims have no scientific basis, and is corrosion-resistant resin temperature of misunderstanding, the misunderstanding is the resin used. We need to use the process of resin, get rid of these misleading, the correct use of the resin. 

 

4. Insulation thermal resistance 

 

4.1 Overview 

 

Polymer resin as insulating materials in addition to have good mechanical properties and dielectric properties, but also has good heat resistance requirements. Such as for aviation, rocket plastic installed lines generally work at 350 ℃, and some even require high temperature tolerance of 500 ℃, but after flying into the stratosphere, the temperature suddenly dropped to about -70 ℃, the temperature at this time the impact of the material is a severe test. So, good heat resistance, not only requires high temperature and the temperature required to endure the impact. The so-called heat-resistant, that is, short or long period of materials under high temperature and rapid temperature changes in the next, maintaining its basic performance ability of normal use. 

 

Heat-resistant materials under high temperature in accordance with the length of time can be divided into short-term heat resistance (heat resistance for short) and long-term heat resistance (or thermal aging). Short-term heat resistance and heat aging properties are two entirely different concepts, not be confused. Short-term heat resistance is material if there is softening in the high temperature deformation, decomposition and other phenomena or material performance in the thermal state changes, usually Tg, Tf, Tm, Td, etc. said. Long-term heat resistance is at a certain temperature polymer resin can be expected under the life, usually in the heat insulating material level, the temperature index, said. 

 

Usually the temperature index is based on the life of the standard aging test provides the value obtained for. Therefore, the softening point temperature, such as heat index and index of the meaning is different. Materials can be used in a temperature, not only a short time can not have a significant performance changes (such as constant soft, vain fuel, no significant decrease dielectric properties, etc.), but not in a long time produce undue As performance changes. Therefore, the wish to identify the material temperature, must be measured short-term heat resistance and heat aging properties. - Short-term heat resistance as the first test, in the short-term heat resistance to meet the use conditions and further thermal aging test done to assess the temperature index, but in the insulation technology is focused on long-term heat resistance. 

 

4.2 The long-term heat resistance - insulation thermal resistance 

 

Thermal aging properties of insulating materials has long been expressed by heat level, our current heat levels are as follows: 

 

 

Here's maximum allowable operating temperature is not equal to short-term heat indicators, such as: 902 resin heat distortion temperature 82 ℃, heat-resistant grade of F-class; 890 resin, heat distortion temperature of 135 ℃, heat-resistant grade for the H-level. 

 

Since the development of high temperature materials, has raised another foreign Heat level: 

 

 

Because of this heat level of name does not reflect the maximum allowable operating temperature insulating materials, production and research work to bring a lot of inconvenience. Therefore, it was suggested that representatives of the maximum allowable working temperature heat level, about the level of the heat, straight as 90, 105, 220 and so on ... ... apparently the name of this one kind of heat is more intuitive level, but also more scientific. 

 

The implications of such a rating system refers to a heat insulation material applied to the appropriate level of electrical, electronics. But in fact, a different motor or electrical insulation parts in not all run at the highest design temperature, it should be the motor or electrical parts of the actual temperature of all select the appropriate level of heat insulation material, insulation system composed of, in order to give full play to the characteristics of materials, improvement of economic rationality. Therefore, the traditional heat-resistant grade of insulating material is clearly not suited to the needs of such a combination of insulation system. Temperature and heat index is used to characterize the profile of the long-term resistance to heat insulating materials, due to the performance of the same material with different thermal aging as a measure of the parameters of life can be different profile of temperature and heat index, so can the motor or heat-resistant electrical insulating material with a single level of the heat capacity distinguished from the effective area. 

 

5. Summary 

 

Temperature is closely related with the production index, the above heat distortion temperature of resin, Martin, heat, glass transition temperature, heat insulation and corrosion resistant grades five temperature using the temperature Concepts, we can clearly see several temperature The physical meaning of indicators, effective use of their properties, and better service for the actual production.