Keywords: Adhesives; Testing The purpose of adhesive testing is to ensure that its performance, quality and safety meet the requirements and standards of specific applications. The following is a detailed introduction to these testing indicators and methods: I. Main Testing Indicators Appearance: To inspect the adhesive for impurities, foreign matter, particles, bubbles, odor, and uniformity. Viscosity: A factor characterizing the flow resistance of liquids. It is commonly measured by capillary viscometers and rotational viscometers. Thixotropy (Anti-sagging): The property whereby the shear stress of an adhesive decreases over time under a constant shear rate. Adhesives with good thixotropy have moderate viscosity during application and are resistant to sagging. Tack-free Time: The time required for moisture-curing adhesives (e.g., silicone adhesives, polyurethane adhesives, PUR hot melt adhesives) to cure when exposed to the atmosphere and lose surface tack. Hardness: Measured using a Shore durometer, including Type A, Type C, and Type D. The appropriate durometer is selected according to the hardness range of the material. Adhesion: To evaluate the bonding performance of the adhesive to different material surfaces. Shear Strength: To measure the strength of the adhesive under shear force. Peel Strength: To evaluate the resistance of the adhesive under peeling force. Temperature Resistance: To test the stability and performance changes of the adhesive under different temperature conditions. Chemical Resistance: Includes chemical resistance, solvent resistance, water resistance, ablation resistance, monomer content, corrosivity, free formaldehyde content, heavy metal content, non-volatile content, etc. Electrical Properties: Such as surface resistance, voltage, volume resistivity, dielectric loss, electrostatic performance, dielectric strength, etc. Physical and Chemical Indicators: Such as air permeability, moisture permeability, density, Mooney viscosity, creep, stress relaxation, bond strength, surface roughness, swelling, refractive index, light transmittance, etc. Mechanical Properties: Such as hardness, tensile properties, tear properties, impact resistance, friction properties, fatigue resistance, compression properties, bending properties, etc. Reliability Performance: Such as oil/liquid resistance, salt spray test, impact test, package drop test, compressive strength, dust resistance, water resistance, etc. II. Main Testing Methods Tapping Method: A small hand hammer is used to tap the bonded surface. The bonding quality is judged by the sound produced. A clear sound indicates no defects, while a dull sound suggests possible defects or air bubbles. Visual Inspection Method: The bonded joint is visually observed for cracks, fissures, and insufficient adhesive. Pressurization Method: For sealed and pressurized bonded parts, a pressure sealing test can be conducted under the working medium and working pressure. No leakage indicates qualification. Acoustic Impedance Method: An acoustic impedance detector is used to measure changes in the mechanical resistance of the bonded joint, thereby evaluating the bonding quality. Ultrasonic Method: Ultrasonic waves are used to detect defects in bonded joints, such as air bubbles and delamination. Universal Testing Machine: Used for tensile, compression, bending, and shear tests to evaluate the mechanical properties of adhesives. Differential Scanning Calorimetry (DSC): Evaluates the thermal properties of adhesives, such as glass transition temperature and melting point. Dynamic Mechanical Analyzer (DMA): Measures the mechanical properties of adhesives at different temperatures and frequencies. Fourier Transform Infrared Spectrometer (FTIR): Analyzes the molecular structure and chemical composition of adhesives. Gas Chromatography-Mass Spectrometry (GC-MS): Used to analyze volatile components and additives in adhesives.