Electrically Heated Clothing Testing

Electric heating garment inspection mainly conducts scientific testing and analysis on electrical safety performance, heating characteristics and temperature control, mechanical safety and durability, material safety and biocompatibility, environmental adaptability and reliability, and electromagnetic compatibility, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Electrical safety performance: Mainly evaluates the electrical safety of the electric heating garment under the normal and single fault conditions, and is the basis for preventing the risks such as the electric shock and fire. The core items include the input power and current, leakage current and electric strength at the working temperature, electrical safety after the waterproof grade testing, and the power density and uniformity of the heating elements, ensuring the basic safety of the product in the intended use environment.

Heating characteristics and temperature control: Evaluates the core function of the garment heating system, including the surface temperature of the heating areas, temperature rise rate, temperature uniformity, temperature fluctuation, and the accuracy and stability of the temperature control system. The testing needs to cover all the preset gears and simulate the different environmental conditions, preventing the local overheating from causing the burns or material damage.

Mechanical safety and durability: Simulates the physical stresses that the garment may bear during the wearing, washing and storage, evaluating its structural integrity. The key items include the bending fatigue, tensile strength and abrasion resistance of the heating wires/pads, as well as the seam strength and tear resistance of the overall fabric of the garment, ensuring that the heating elements and the garment body work reliably within the life cycle.

Material safety and biocompatibility: Detects the safety of the materials that directly or indirectly contact the skin, preventing the precipitation of the hazardous substances. The items cover the pH value, formaldehyde content, decomposable carcinogenic aromatic amine dyes and heavy metal content of the textile, as well as the release of the hazardous substances (such as the VOCs) from the insulation layer of the heating elements at high temperatures, ensuring the health of the wearers.

Environmental adaptability and reliability: Verifies the performance retention ability of the electric heating garment in the specific use environments. Including the high and low temperature cycling testing, damp-heat testing, salt spray testing (for the metal parts), low-temperature start-up performance, and the long-time continuous working reliability testing simulating the actual use scenarios, evaluating its environmental tolerance.

Electromagnetic compatibility (EMC): Evaluates whether the electromagnetic disturbance generated by the control circuit of the electric heating system during operation is within the limits, and its own immunity to the external electromagnetic interference. The items include the conducted disturbance, radiated disturbance, electrostatic discharge immunity and surge immunity, preventing the interference with the other electronic equipment or its own functional abnormalities.

Testing Scope

Heating elements and wires: As the core heating components, the testing scope includes the resistivity of the materials such as the metal heating wires, carbon fibre heating pads and conductive fabrics, the insulation layer thickness and voltage resistance, the reliability of the joint welding/crimping, the current-carrying capacity, and the electrical property changes after the repeated bending, ensuring the safety and life of the heat source.

Temperature control and power supply system: Covering the controllers (such as the button type and APP control), temperature sensors (NTC and thermocouple), rechargeable battery packs (mainly lithium batteries), power adapters and connection interfaces. The control accuracy, the charge and discharge performance and safety of the battery (such as the overcharge and overdischarge protection), and the anti-misinsertion and durability of the interfaces need to be tested.

Garment body and auxiliary materials: The testing scope includes the outer fabric, lining, filling materials, sewing threads, zippers and Velcro. In addition to the conventional colour fastness, pilling, air permeability and moisture permeability, special attention needs to be paid to the flame retardant performance (especially the parts near the heat sources) and the dimensional stability and strength retention rate after heating and dampening.

Finished garment as a whole: The systematic testing is carried out on the fully assembled electric heating garment. Including the rationality of the heating area distribution of the whole garment, wearing comfort (whether the heating elements have a foreign body sensation), the overall performance after washing (needs to be carried out according to the washing procedure indicated by the product), and the comprehensive safety and functional evaluation under the simulated use state.

Products for specific uses: For the electric heating garments for the special application scenarios, the testing scope needs to be extended. For example, the outdoor sports garments need to strengthen the waterproof and moisture permeable and low-temperature performance testing; the medical and health care garments need to add the biosafety and the relevant standards of the medical electrical equipment; and the garments for the industrial explosion-proof environments need to meet the explosion-proof electrical certification requirements.

Packaging and marking: Checks the completeness and accuracy of the product nameplate, instruction manual and safety warning markings. The contents must include the rated voltage/power, battery specifications, cleaning and maintenance instructions, safety precautions (such as the prohibition of the folding powered storage and the prohibition for the specific populations), the number of the complied standards and the manufacturer information. This is the important guidance for the product compliance and the safe use by the users.

Testing Methods

Standard temperature rise method: In accordance with the GB 4706.1, GB 4706.8 or IEC 60335 series standards, the garment is operated at the rated voltage until the stable state in a specified test corner or temperature measuring frame, and the temperature rise of the various parts is measured with the thermocouples or a thermal imager. The temperatures of the heating element surface, controller, battery and the adjacent textile materials are monitored emphatically, and must not exceed the standard limits.

Electrical safety test method: The testing is carried out with the equipment such as the withstand voltage tester, earth resistance tester and leakage current tester. Including the electric strength test at the working temperature (such as 1250V/1min), leakage current measurement, earth continuity testing (if applicable), and the insulation performance testing after simulating the rain (IPX4) or immersion (IPX7), verifying the effectiveness of the basic insulation and protection.

Mechanical stress simulation method: Dedicated equipment is used to simulate the mechanical damage in the actual use. For example, a flexing testing machine is used to carry out tens of thousands of reciprocating bendings on the sample sections containing the heating wires; a Martindale abrasion tester is used for the abrasion testing of the fabric in the heating areas; and multiple domestic washes and drying are carried out according to the standard procedures, subsequently detecting the attenuation of the electrical performance and mechanical strength.

Environmental test method: Carried out in the environments such as the programmable constant temperature and humidity chamber, thermal shock chamber and salt spray chamber. The sample is placed under the conditions such as the high temperature (such as 40 ℃), low temperature (such as -20 ℃), high humidity (such as 93% RH) or temperature cycling, powered on and operated or stored for a certain time, and then the changes in its appearance, function and safety performance are evaluated, verifying the environmental adaptability.

Material chemical analysis method: Carried out in accordance with GB 18401, GB 31701 and the ecological textile standards (such as the OEKO-TEX® Standard 100). The instruments such as the pH meter, UV-visible spectrophotometer and gas chromatography-mass spectrometer are used to quantitatively analyse the contents of the hazardous chemicals in the textile, ensuring the safety and harmlessness of the materials contacting the human body.

Electromagnetic compatibility test method: Carried out in a semi-anechoic chamber or shielded room. The equipment such as the EMI receiver, signal generator, electrostatic discharge gun and surge generator is used to respectively execute the disturbance emission testing (CE/RE) and immunity testing (ESD, EFT and Surge), and the qualification is judged in accordance with GB/T 4343.1 and the GB/T 17626 series standards.

Testing Standards

Domestic Standards:

1. GB 4706.1-2005, Household and similar electrical appliances — Safety — Part 1: General requirements

2. GB 4706.8-2012, Household and similar electrical appliances — Safety — Particular requirements for blankets, pads and similar flexible heating appliances

3. GB 31241, Lithium ion cells and batteries used in portable electronic equipments — Safety requirements

4. GB 18401-2010, National general safety technical code for textile products

International Standards:

1. IEC 60335-1, Household and similar electrical appliances — Safety — Part 1: General requirements

2. IEC 60335-2-17, Household and similar electrical appliances — Safety — Part 2-17: Particular requirements for blankets, pads, clothing and similar flexible heating appliances

3. ISO 105, Textiles — Tests for colour fastness

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Comprehensive safety performance tester: A professional equipment integrating the functions such as the withstand voltage, insulation resistance, earth resistance and leakage current testing, which can automatically apply the test voltage, record the data and judge the results. It is used to quickly and accurately complete the electrical safety item testing of the electric heating garment, and is one of the core equipment of the laboratory.

Multi-channel temperature recorder and thermal imager: The temperature recorder continuously monitors and records the temperature change curves of the various points through the multiple thermocouples arranged at the key positions of the garment, evaluating the temperature rise and uniformity. The thermal imager can intuitively and non-contactly display the temperature distribution on the whole surface of the garment, and quickly find the local hot spots.

Environmental simulation test chambers: Including the high and low temperature test chamber, constant temperature and humidity chamber and salt spray chamber. They are used to create the extreme or alternately changing climate environments, examining the low-temperature start-up ability of the electric heating garment, the working stability under the high temperature and high humidity, and the corrosion resistance of the metal parts, verifying its environmental reliability.

Material physical property testing equipment: Such as the universal material testing machine (testing the tensile, tearing and seam strengths), Martindale abrasion tester, flexing fatigue testing machine and washing testing machine. These equipment are used to evaluate the mechanical durability of the fabric, heating wires and finished garment, simulating the physical wear and tear caused by the long-term use and care.

Battery comprehensive testing system: Specially used to test the performance and safety of the rechargeable battery packs. The capacity, cycle life, internal resistance, overcharge/overdischarge protection function testing can be carried out, as well as the safety abuse tests such as the forced internal short circuit, crushing and nail penetration, ensuring that the battery as the power source is safe and reliable.

Electromagnetic compatibility (EMC) testing system: The composition is complex, including the semi-anechoic chamber, conducted disturbance testing system, power frequency magnetic field generator, electrostatic discharge simulator and electrical fast transient/burst generator. It is used to comprehensively evaluate the electromagnetic emission and anti-interference ability of the electric heating garment control system, ensuring that its electromagnetic compatibility meets the regulatory requirements.