Hot melt elasticity test: full analysis of international general standards

Hot melt elasticity test: full analysis of international general standards
In the production, research and development and application of hot melt wires, elasticity testing plays a vital role. It directly determines the key factors such as the performance, service life and scope of application of hot melt wires under various actual working conditions. Using internationally accepted standards to test the elasticity of hot melt wires can not only provide companies with accurate and reliable testing methods, but also ensure that product quality is comparable and competitive in the international market, and win the trust of international wholesale buyers. This article will explore in depth the representative international general standards for hot melt elasticity testing to help you fully understand the specifications and requirements in this field.

1. ASTM D3111: Hot Melt Adhesive Flexibility Test Standard
ASTM D3111 is an important standard developed by the American Society for Testing and Materials (ASTM). It uses a mandrel bending test to determine the flexibility of hot melt adhesives. This test method is simple, practical and highly operable.
(I) Test Principle
The hot melt adhesive sample is made into a sheet and then wound on a mandrel of a certain diameter. The flexibility of the sample is evaluated by observing the bending performance of the sample under specific temperature conditions, such as whether cracks or fractures occur. The diameter of the mandrel can be selected according to different test requirements and sample characteristics to simulate various bending stress scenarios that the hot melt wire may encounter in actual applications.
(II) Test Steps
First, accurately weigh a certain mass of hot melt adhesive sample, heat it to a molten state, and evenly coat it on a flat substrate to form a sheet sample with uniform thickness. The thickness is generally controlled within a specified range, such as the common 1mm-3mm.
The prepared sheet sample is pretreated at a set test temperature. Usually, this temperature is determined according to the actual operating temperature range of the hot melt wire to ensure that the test results can truly reflect its flexibility performance under actual working conditions.
Select a mandrel of appropriate diameter and carefully wind the pretreated sheet sample on the mandrel. During the winding process, pay attention to keeping the sample flat and tight to avoid wrinkles or looseness, and ensure that the winding speed is uniform.
Observe the surface condition of the sample during the winding process and within a certain period of time after winding, and record whether cracks, breaks or other abnormal phenomena occur. If the sample remains intact and crack-free after winding, the mandrel diameter can be further reduced for retesting until the sample cracks or reaches the preset minimum mandrel diameter.
(III) Result evaluation and application
Assess the flexibility level of the sample based on its performance on mandrels of different diameters. If the hot melt wire can still remain crack-free on a mandrel with a smaller diameter, it means that it has good flexibility and can adapt to more complex and tighter bending requirements. In practical applications, it is less likely to break or debond due to bending stress. For example, in some scenarios where the hot melt wire needs to fit closely to complex curved products, such as the assembly of automotive interior parts and the fixing of electronic equipment circuits, hot melt wires with higher flexibility can better meet these requirements.
This standard provides a clear basis for flexibility testing for the production and quality control of hot melt wires, helping companies optimize product formulas and production processes to improve the flexibility performance of hot melt wires and enhance the competitiveness of products in the market. At the same time, it also provides a unified and objective evaluation index for international wholesale buyers, making it easier for them to compare and screen products from different suppliers.

2. ISO 23673: Test standard for elastic properties of plastic melts
ISO 23673:2021 is a standard for the determination of elastic properties of plastic melts issued by the International Organization for Standardization (ISO). For materials such as hot melts that have unique rheological properties when in a molten state, this standard has important guiding significance.
(I) Test principle
The elastic index is determined based on the measurement of shear storage modulus using an oscillating rheometer. During the test, the hot melt sample is placed between the test fixtures of the rheometer, and an oscillating shear stress is applied under certain temperature and frequency conditions. By measuring parameters such as the storage modulus and loss modulus of the sample during the shear process, the elastic index is calculated, thereby quantitatively characterizing the elastic properties of the hot melt melt.
(II) Test steps
Accurately weigh an appropriate amount of hot melt sample and place it in the sample tray of the rheometer, and ensure that the sample surface is flat and smooth, without defects such as bubbles and impurities, to ensure the accuracy of the test results.
Set a suitable test temperature. Generally speaking, the test temperature will be close to the actual processing temperature or the upper limit of the use temperature range of the hot melt, because in this temperature range, the elastic properties of the hot melt have a more significant impact on the actual application.
Select an appropriate oscillation frequency range. Usually, a multi-frequency scanning test is performed to fully understand the elastic response characteristics of the hot melt at different deformation rates. The common frequency range can be from 0.1Hz to 100Hz or even higher, depending on the characteristics of the sample and the purpose of the test.
Start the rheometer and perform an oscillatory shear test. During the test, the rheometer automatically records the storage modulus (G’), loss modulus (G”) and phase angle (δ) of the sample, and calculates the elastic index based on these data.
(III) Result evaluation and application
The higher the elastic index, the better the elastic properties of the hot melt. Hot melt wires with a higher elastic index are less likely to break or spin during processing, which can ensure the continuity and stability of production. In practical applications, they can also better adapt to minor deformations caused by temperature changes, mechanical vibrations and other factors, and reduce problems such as debonding and cracking caused by insufficient elasticity, such as in some scenarios where hot melt wires need to withstand dynamic stress for a long time, such as elastic sewing of textiles and flexible connection of pipes. This standard provides an accurate elastic performance test method for the research and development and production of hot melt wires, which helps companies develop more competitive high-performance hot melt wire products and meet the strict requirements of different customers in the international market for product quality and performance.

3. ISO 16790: Test standard for tensile properties of thermoplastics in the molten state
ISO 16790:2021 specifies methods for determining the tensile and fracture properties of molten plastics, which is directly related to the evaluation of the mechanical properties and elastic behavior of hot melt wires in the molten state.
(I) Test principle
This standard involves measuring the force generated when a molten filament is deformed under specified extrusion temperature and tensile conditions. By simulating the extrusion and stretching process of the hot melt wire in the actual processing process, the hot melt wire sample is stretched at a specific temperature and stretching speed, and its tensile force, elongation, breaking strength and other parameters are measured, so as to fully understand the elastic characteristics and mechanical properties of the hot melt wire in the molten state.
(II) Test steps
First, the hot melt wire sample is pretreated. It is usually necessary to cut the sample into small sections of a certain length and dry it under the specified temperature and humidity conditions to remove the moisture in the sample and ensure the accuracy of the test results.
The pretreated sample is placed in the extrusion device and extruded at the set extrusion temperature. The extrusion speed should be kept constant. The hot melt wire sample after extrusion should be clamped on the fixture of the tensile tester immediately.
Set a suitable stretching speed. The stretching speed can be selected according to different test purposes and sample characteristics. The common stretching speed range can range from 10mm/min to 1000mm/min to simulate the different deformation rates of hot melt wire in actual applications.
Start the tensile testing machine and stretch the hot melt sample, while recording the tensile force, elongation and other data until the sample breaks.
(III) Result evaluation and application
According to the tensile force-elongation curve obtained from the test, the key mechanical performance indicators of the hot melt such as elastic modulus, yield strength, fracture strength and elongation can be analyzed. These indicators can comprehensively reflect the elastic and toughness characteristics of the hot melt in the molten state. For example, higher elastic modulus and yield strength indicate that the hot melt can better resist deformation and maintain shape stability in the initial stage of force; while higher fracture strength and elongation indicate that the hot melt can still maintain a certain integrity when subjected to a large tensile force and is not easy to break. In actual production, these mechanical performance indicators can be adjusted by optimizing the raw material formula, processing parameters and other means, so that the hot melt can better meet the needs of different application scenarios, such as in the wood processing and packaging industries where the hot melt needs to have higher tensile strength and toughness to withstand certain tensile and impact forces. This standard provides a standardized test method for the performance evaluation and quality control of thermal fuses, which helps to improve the stability and reliability of product quality and establish a good brand image in the international market.

4. Summary
International general standards for thermal fuse elasticity testing, such as ASTM D3111, ISO 23673 and ISO 16790, standardize and quantify the elastic properties of thermal fuses from different angles. These standards cover the test methods and evaluation systems for multiple key performance indicators such as flexibility, elastic modulus, and tensile properties of thermal fuses in different states, providing a unified and scientific test basis and quality evaluation criteria for thermal fuse manufacturers, R&D institutions and international wholesale buyers.
For thermal fuse manufacturers, strictly following these international standards for product quality control and R&D innovation will help enhance the international competitiveness of products, expand overseas markets, and meet the strict requirements of different customers for thermal fuse performance. For international wholesale buyers, understanding and being familiar with these standards can better screen and compare products from different suppliers, ensure that the purchased thermal fuse products are of reliable quality and stable performance, thereby providing strong guarantees for downstream production and application.
In the future, with the continuous advancement of thermal fuse technology and the increasing diversification of application scenarios, the international standards for elasticity testing will continue to be improved and updated. Enterprises should pay attention to the changes in these standards in a timely manner and actively participate in the formulation and revision of international standards to occupy a favorable position in the fierce international market competition and promote the healthy and sustainable development of the thermal fuse industry.