Definition
Putty flexibility tester is a special testing equipment used to evaluate the cracking resistance of putty coatings in building decoration materials under deformation conditions. It quantitatively measures the flexibility of the putty layer by simulating the stress of the substrate when it undergoes deformation, which is a key parameter to measure the ability of putty products to adapt to the expansion and contraction of the substrate, vibration and other factors, and is of great significance for ensuring the construction quality and coating durability.
Principle
The core working principle of the instrument is based on the three-point bending or shaft bending test method. The prepared putty sample is coated on the standard metal test plate at a specific thickness, cured to the specified state, and placed on the instrument bending device. The test plate is bent at a uniform speed around a shaft rod of a certain diameter through a drive device until a predetermined angle is reached or cracking of the coating is observed. The minimum diameter of the shaft rod that the putty layer can withstand without cracking, or the maximum angle at which it bends without cracking on a certain diameter shaft rod, is characterized by its flexibility. The basic bending stress relationship can be referred to the material mechanics formula: σ = (M * y) / I, where M is the bending moment, y is the distance from the neutral axis, and I is the cross-sectional moment of inertia, which helps to understand the stress state of the coating when it is bent.
Measurement method
Measurements usually follow relevant national or industry standard procedures. First, the putty sample is evenly applied and scraped on the standardized tinplate or aluminum plate, the thickness of the wet film is controlled and the specified period is cured under standard temperature and humidity conditions. Insert the cured test plate into the bending test position of the tester so that the painted side is facing outward or oriented according to the standard requirements. Start the instrument so that the test plate is wound on a shaft rod of a specific diameter at a uniform speed within a set time. Immediately after completion, the putty film is inspected with the naked eye or magnifying glass for cracks or peeling. A series of tests were carried out by replacing the shaft rods of different diameters to determine the minimum shaft rod diameter in which the coating did not crack. Some methods also use tapered shaft rods for rapid determination.
Influencing factors
The measurement of putty flexibility is influenced by a variety of factors. Material formulation is a key internal factor, including the type and content of binders, the use of plasticizers, the ratio and particle size of fillers, etc., which directly affect the elastic modulus and elongation at break after film formation. Construction and preparation conditions such as coating thickness, uniformity, and temperature, humidity and duration of the curing environment will affect the curing process and final internal stress of the putty. The type of substrate and surface treatment can also have an impact on adhesion and stress transfer. In addition, operational variables during the testing process, such as bending speed, the accuracy of the rod diameter, and the standard consistency of observation and evaluation, need to be strictly controlled to ensure the reliability and comparability of the results.
Applications
Putty flexibility tester is mainly used in the fields of building materials, coating chemical and construction engineering quality inspection. In manufacturing enterprises, it is used for new product formulation development, production process optimization, and finished product quality control to ensure that products meet flexibility specifications. In third-party testing institutions and scientific research units, the instrument is used to verify and compare product performance according to national standards or industry standards. In the quality control process of construction projects, it can assist in evaluating whether the selected putty products are suitable for the base surface with certain deformation risks, such as the settlement period wall of a new building, the exterior wall with large temperature difference or the flexible base layer, so as to prevent the problem of later cracking.
Equipment selection considerations
When choosing a putty flexibility tester, it is necessary to comprehensively consider the technical parameters and functional requirements. The core parameters include the range and accuracy of the diameter of the shaft rod, which should cover the series sizes specified in the relevant standards. The stability of the drive mechanism and the control accuracy of the bending speed directly affect the reproducibility of the test. The structure of the instrument should be sturdy, and the fixture design should ensure that the test plate is firmly clamped and accurately aligned. Whether the operation interface is clear and the degree of automation is also the key to improving the inspection efficiency. In addition, the equipment must meet the requirements of the standard system implemented by the target market and have reliable calibration and maintenance convenience. Users should conduct a comprehensive evaluation based on their own main test standards, sample throughput and budget.