Insulation Materials and Home Appliance Safety

Insulation Materials and Home Appliance Safety

1. Performance of insulation materials
The use of insulating materials in household appliances is related to the quality and performance of electrical products, so there is no doubt that insulating materials play an important role in electrical products. There are many types of household appliances, and each product has different requirements for insulation materials. However, in order to ensure the safety of home appliances, the insulation materials used in home appliances should meet the following requirements:

A. Good dielectric properties
The dielectric properties of insulating materials, including resistance, leakage current, dielectric constant, dielectric strength, dielectric loss, etc., are used to represent changes in dielectric properties and insulation quality under applied voltage conditions. Any insulating material will have leakage current flowing through the insulating material when a voltage is applied. During this process, the resistance encountered by the current on the surface of the insulating material is the surface resistance, and its resistance value is generally between 107~108Ω; when passing through the insulating material The resistance encountered by a medium is volume resistance. Under the same conditions, the volume resistance is greater than the surface resistance. The dielectric constant is the increase in the capacitance between the two plates in the presence of a dielectric and the capacitance in a vacuum state. The ability of an insulating material to resist electrical breakdown is called electrical strength, while dielectric loss is the electrical energy consumed in heating the dielectric under an applied voltage. In daily use, dust or moisture can affect the dielectric properties of insulation materials.

b. Good heat resistance and flame retardant properties
During the use of electrical appliances, due to the continuous flow of current, long-term uninterrupted use will cause the temperature of the electrical appliance to rise. When the external temperature of the insulating material increases, its own conductivity will increase, and the degradation of the insulation performance will be significantly reduced. As a result, there is a risk of the insulation material softening and catching fire, which can cause devastating damage to the entire appliance or even the entire circuit system being used. Therefore, in addition to basic resistance properties, insulating materials must also be heat-resistant and flame-retardant at high temperatures.

C. Good anti-aging properties
When insulation materials are ravaged by heat, electromagnetic fields, light, oxidation, mechanical force and microorganisms during long-term use, depreciation losses will occur. This depreciation loss will gradually weaken the insulation performance and insulation strength of the insulation materials. Electricity and heat are the two most important factors affecting the aging of insulation materials. Therefore, the aging resistance of insulation materials after long-term use directly affects the service life of home appliances.

d. Good moisture-proof performance
Moisture-proofing is generally a preventive measure when using electrical products. Moisture can cause the entire circuit to short-circuit. As a physical medium, insulation material may produce cracks or capillaries due to its own processing process. If the external environment of the insulation material is relatively humid, water molecules may penetrate into the insulation material through these fine lines or pores. When the insulation material becomes damp, not only the insulation performance will be affected, but the insulation material will gradually corrode, causing the insulation performance of the entire electrical appliance to decrease and the safety index to decrease.

2. Standard safety requirements
The development and popularization of household appliances has brought huge social benefits. It reduces housework and allows users to have more time to study, entertain, and rest, and gain a lot of convenience. However, electrical appliances also bring many hazards to humans: fire, electric shock, harmful rays, electromagnetic interference, etc. Among them, fire is the most dangerous and is directly related to the safety of people's lives and property. Therefore, the safety features of household appliances are particularly important. my country's GB4706 series of standards have strict regulations on the safety characteristics of household appliances. The safety requirements for insulating materials are explained below in conjunction with the standards.

(1) Electrical performance safety requirements
In electrical products, the role of insulating materials is to isolate conductive parts of different potentials and polarities from each other for energy conversion. Insulating materials are affected by the electric field during the operation of electrical appliances. Insulating materials play a decisive role to a certain extent whether the electrical appliances can operate normally. The greater the resistivity of the insulating material, the better the insulation performance and the smaller the leakage current. Chapter 13 of GB4706 "Leakage Current and Electrical Strength of Appliances at Operating Temperature" stipulates the testing of the electrical performance of appliances at operating temperature. Leakage current generally refers to the current flowing through insulating parts under the action of high DC voltage. The measurement of leakage current is essentially the same as the measurement of insulation resistance, and both can reflect the insulation status of electrical products to a certain extent. Chapter 29 of the standard limits the leakage resistance index of different material groups. The leakage start-up resistance test is an accelerated test that simulates very harsh conditions to test whether insulating materials will form leakage traces, so as to distinguish the ability of solid insulation materials to resist leakage start-up in a short time and ensure the safe use of products under specific environmental conditions. Chapter 29 of the standard limits the leakage resistance index of different material groups. The leakage start-up resistance test is an accelerated test that simulates very harsh conditions to test whether insulating materials will form leakage traces, so as to distinguish the ability of solid insulation materials to resist leakage start-up in a short time and ensure the safe use of products under specific environmental conditions. Chapter 29 of the standard limits the leakage resistance index of different material groups. The leakage start-up resistance test is an accelerated test that simulates very harsh conditions to test whether insulating materials will form leakage traces, so as to distinguish the ability of solid insulation materials to resist leakage start-up in a short time and ensure the safe use of products under specific environmental conditions.

(2) Mechanical performance safety requirements
Parts and their structures made of insulating materials should have sufficient mechanical strength to resist external forces. Mechanical strength refers to the maximum load that a unit area can withstand when subjected to external forces. Chapter 21 of GB4706 specifically conducts a mechanical strength test, and the electrical performance of the appliance should not be affected after the test. Article 21.2 of the General Standard also stipulates that solid insulation of easily accessible parts should be strong enough to prevent puncture by sharp tools. Therefore, the mechanical properties of insulating materials cannot be ignored.

(3) Heat resistance and flame retardant safety requirements
Electrical products will generate heat during normal use, causing the heating temperature of insulating material parts to increase, causing the conductivity of the insulating material to increase and the insulation performance to decrease. At the same time, if the temperature is too high, it will also cause the insulating material parts to soften. Even aging reduces its mechanical properties; in some cases, insulation materials can also pose a fire hazard. Therefore, insulation materials must have certain heat resistance and flame retardancy to ensure safety in use. GB4706 General Standard 30.1: For external parts made of non-metallic materials, thermoplastic material parts used to support additional insulation live reinforced insulation materials used to support live parts (including connectors), the deterioration of which may cause the appliance to fail to comply with this standard, shall be completely Heat resistant. Qualification is determined by conducting a ball pressure test on the relevant parts. In Standard 30.2, parts of non-metallic materials used in devices requiring ignition and spread of flame shall be resistant. Among them, tests 30.2.2 and 30.2.3 are special tests carried out on insulating material components of current-carrying connections. The flame retardant performance of insulating materials is generally judged through the burnt wire test. Qualification is determined by conducting a ball pressure test on the relevant parts. In Standard 30.2, parts of non-metallic materials used in devices requiring ignition and spread of flame shall be resistant. Among them, tests 30.2.2 and 30.2.3 are special tests carried out on insulating material components of current-carrying connections. The flame retardant performance of insulating materials is generally judged through the burnt wire test. Qualification is determined by conducting a ball pressure test on the relevant parts. In Standard 30.2, parts of non-metallic materials used in devices requiring ignition and spread of flame shall be resistant. Among them, tests 30.2.2 and 30.2.3 are special tests carried out on insulating material components of current-carrying connections. The flame retardant performance of insulating materials is generally judged through the burnt wire test.

(4) Moisture-proof safety requirements
There are capillaries and certain cracks in the thermal insulation material components on a microscopic level. Since the diameter of water molecules is much smaller than these capillary pores and cracks, the thermal insulation material is easily penetrated by water molecules. Water molecules in moisture enter the insulating material through condensation, adsorption, absorption, diffusion, breathing, etc. After the insulating material absorbs moisture, the insulation performance will be greatly deteriorated, resulting in damage to the electrical performance of electrical products. Therefore, electrical products should have sufficient moisture-proof properties to maintain their good electrical performance and provide safety protection. Chapter 15 of GB4706 is for the safety requirements of different appliances under possible wet conditions.

In summary, the performance of insulating materials is closely related to the safety characteristics of household appliances. Therefore, when selecting insulating materials, it is necessary to ensure the quality of the insulating materials and consider factors such as the use of household appliances, so ensure that the appliances are in use Medium and long-lasting safety.