Commonly used materials are characterized by the highest use temperature.There are different standards and test methods for different materials.For general use as plasticMartin heat resistance temperatureTo represent.Used in coating industryBlast thermostatic ovenorHigh temperature furnaceAfter reaching the specified temperature and timefilmThe surface condition shall be inspected, tested, or other properties such as impactbend, immersionSalt spray testAnd then expressed as pre and post test data.All coatings used in high temperature occasions must be heat resistantfilmImportant technical indicators.
Reference standards
GB 11026.1 Guidelines for Determining the Heat Resistance of Electrical Insulating Materials Part 1: General Procedures for Formulating Heat Aging Test Methods and Evaluating Test Results
Heat resistance assessment
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Evaluation of heat resistance of insulating materials
Many insulating materials of the same genus may be very different in heat resistance.Therefore, it is not appropriate to judge the heat resistance of insulating materials according to their chemical names.
Various insulating materials used in the insulation structure of electrical products, their respective heat resistance may be affected by other materials.In addition, the heat resistance of various materials depends to a large extent on their specific functions in the insulation structure.
As far as the use of insulating materials in electrical products is concerned, there are two purposes for material evaluation: one is to evaluate the insulation materials as electricalInsulation structureThe evaluation of a certain material of a component, and the evaluation of a certain material used alone or as a simple combination of components of an insulation structure.
In general, the qualification test and operating experience are recognized asInsulating materialAcceptable basis for heat resistance assessment.
When based on operating experience, attention shall be paid to ensuring that the experience is applicable.However, in some cases, it may also be appropriate to apply one experience to another application.Appropriate methods should be developed to determine the relationship between operating experience.
Significant progress has been made in the research of material evaluation test methods.It has been more perfect in determining and expressing the heat resistance of insulating materials. For this, please refer to GB 11026.1, and other parts of this guide will also be formulated.
For a material, different temperature indexes and half differences can be obtained by using different properties (such as electrical, mechanical, etc.), methods and failure criteria to draw heat resistance charts.The different temperature index and half difference indicate that the heat resistance is different, and it determines the use mode of the material and the functions it can undertake.
The results obtained by the standard sample test may be different from the results obtained by the material test according to its actual use form.The insulation structure is closer to the actual situation.Therefore, the results of insulation structure test can prove the applicability of materials in relevant applications.[1]
Heat resistance evaluation of insulation structure
It is better to evaluate the heat resistance of insulation structure based on relevant operating experience.Without such operating experience, appropriate functional tests should be carried out.For this purpose, it is necessary to use a structure proven by operating experience as the reference insulation structure.The heat resistance of the new insulation structure is evaluated by comparing with it.Insulation research unit andelectricianThe research, design, manufacturing, testing and use units of products shall design and conduct appropriate tests.When designing appropriate tests and formulating standardized test procedures for heat resistance evaluation, reference should be made to relevant data for evaluating insulation structures.
When selecting the components of the insulation structure, the heat resistance evaluation results of a single material can be referred to (see 4.1).
As long as the proper insulation structure test or operation experience proves that a certain insulation material has satisfactory operation characteristics, it can be judged whether the material is suitable for a specific insulation structure.Regardless of the material itselfHeat resistance。
For very simple insulation structure and insulation structure subject to single stress, it can be determined according to the specific situation, and it is necessary to carry out the functional test of insulation structure;A satisfactory result can be obtained by simply evaluating the heat resistance data of the material.If it is necessary to evaluate whether a material is suitable for an electrical product, a pair test shall be conducted with materials that have been proved by appropriate operating experience as reference materials.In this regard, relevant units shall provide data of materials proven by operating experience in specific applications.At the same time, in order to be able to properly grade materials, guidelines on how to evaluate operating experience should also be provided.
Standardized test procedures applicable to comparative evaluation shall be formulated.In the absence of such standardized test procedures, the insulation research unit and the research, design, manufacturing, testing and user of electrical products shall select appropriate test procedures for testing.
Heat resistance grade
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The service life of electrical product insulation is affected by many factors (such as temperature, electrical and mechanical stress, vibration, harmful gases, chemicals, moisture, dust and irradiation), and the temperature usually affects the insulation materials andInsulation structureThe dominant factor of aging.Therefore, there has been a practical and internationally recognized method of heat resistance classification, that is, the heat resistance of electrical insulation is divided into several heat resistance grades. The heat resistance grades and corresponding temperature values are as follows:
Heat resistance grade temperature, ℃
Y 90
A 105
E 120
B 130
F 155
H 180
200 200
220 220
250 250
If the temperature exceeds 250 ℃, the heat resistance grade shall be set at an interval of 25 ℃.
It is also possible not to use letters to indicate the heat resistance grade, but the above correspondence must be followed.For equipment used under special conditions and with special requirements, the above classification methods are not necessarily applicable, and other identification may be requiredclassification method 。
The heat resistance grade marked on the electrical product usually indicates the maximum temperature that the product can withstand when reaching the expected service life under rated load and other specified conditions.Therefore, in electrical products, the temperature pole of insulation used at the highest temperature should not be lower than the temperature corresponding to the heat resistance grade of the product.
For customary reasonsInsulation structureAnd electrical products generally use the term "heat resistance rating".However, the trend in the future is that "temperature index" and“Relative temperature index”These two terms;For insulation structure, the term "identification mark" is recommended;The "identification mark" of the insulation structure is only related to the specific product designed;The term "heat resistance grade" is reserved for electrical products.
Selection and determination of insulation:
The research, design and manufacturing units of electrical products shall select appropriate insulation materials and insulation structures according to the insulation temperature limit.The basis for determining the reasonable temperature limit value of insulation can only be operating experience or appropriate and acceptable tests.Operating experience is to select insulation materials andInsulation structureThe important foundation of.However, when selecting new materials and new structures, appropriate tests are the basis for such selection.[2]
Heat resistance of fiber
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stayNatural fiberMedium, hemp has the best heat resistance, followed bysilkAnd cotton, wool worst.
stayChemical fibreMedium,Viscose fibreIt has good heat resistance and is often used as tire adhesiveCord fabric，polyester fiberHeat resistance is also very good, followed byacrylic fibres, andnylonandVinylon、PolypropyleneThe heat resistance of nylon is poor. Nylon shrinks when heated. Vinylon is not resistant to damp heat. Polypropylene is not resistant to dry heat. The fiber with the worst heat resistance should beChloro fiber。
