How the heat resistance of colour coated aluminium coils is tested and assessed？

Everyone wants to know how to test and evaluate the heat resistance of colour coated aluminium coils, The following article lets us know how the test was conducted.

Laboratory Oven Tests

High Temperature Exposure：

Samples of the colour coated aluminium coils are placed in a laboratory oven set at specific high temperatures, typically ranging from 100°C to 300°C or even higher, depending on the expected application conditions. They are left in the oven for a predetermined period, which can vary from a few hours to several thousand hours.

Visual Inspection：

After the exposure time, the samples are removed from the oven and visually examined for any signs of colour change, such as fading, discoloration, or the development of yellowing. The presence and extent of these visual changes are recorded and used to assess the degree of heat resistance. For example, if a coil shows significant colour fading after exposure to 200°C for 500 hours, it indicates relatively poor heat resistance.

Microscopic Examination：

In addition to visual inspection, microscopic techniques can be employed to look for more subtle changes in the coating structure. This may include the formation of cracks, blisters, or delamination within the coating layer. These microscopic defects can provide early indications of coating failure and help in understanding the mechanisms of heat-induced degradation.

Thermal Cycling Tests

Cyclic Temperature Exposure：

The colour coated aluminium coil samples are subjected to repeated cycles of heating and cooling within a specific temperature range. For instance, they may be heated to a high temperature, say 250°C, held at that temperature for a certain time, and then rapidly cooled to room temperature or a lower specified temperature. This cycle is repeated multiple times, often hundreds or even thousands of times, to simulate the thermal stresses that the coils may experience during actual use.

Performance Evaluation：

After the thermal cycling, the samples are evaluated for various properties. This includes checking for any loss of adhesion between the coating and the aluminium substrate, which can be determined by using adhesion tests such as the cross-cut test or the peel test. Any reduction in adhesion strength compared to the untested samples indicates a potential decrease in heat resistance. Additionally, the samples are inspected for any changes in mechanical properties, such as flexibility or hardness, which can affect the coil's performance in practical applications.

Instrumental Analysis

Differential Scanning Calorimetry (DSC)：

DSC measures the heat flow associated with transitions in the material as it is heated or cooled. For colour coated aluminium coils, DSC can be used to detect any phase changes, glass transitions, or curing reactions in the coating material that occur during heating. By analyzing the DSC curves, information about the coating's thermal stability and the temperature range over which it remains stable can be obtained.

Thermogravimetric Analysis (TGA)：

TGA measures the weight change of a sample as it is heated in a controlled atmosphere. In the case of colour coated aluminium coils, TGA can help determine the temperature at which the coating begins to decompose or degrade significantly. This provides valuable data on the upper temperature limit for the coating's stability and its resistance to thermal degradation.

Accelerated Weathering Tests

UV and Condensation Exposure：

Accelerated weathering testers are used to expose the colour coated aluminium coil samples to intense ultraviolet (UV) light and cycles of condensation. These conditions mimic the effects of long-term outdoor exposure, including the combined effects of sunlight, heat, and moisture. The samples are continuously exposed to UV radiation for a specified number of hours, followed by a condensation cycle to simulate night-time or humid conditions.

Performance Monitoring：

During and after the accelerated weathering tests, the samples are regularly inspected for changes in colour, gloss, and coating integrity. Colour measurement instruments can be used to quantitatively assess any colour changes, and gloss meters can measure the reduction in glossiness. The formation of cracks, peeling, or other forms of coating damage is also noted. Based on these observations, the heat resistance and overall durability of the colour coating under simulated outdoor conditions can be evaluated.

International standards for testing the heat resistance of color coated aluminium coils

BS EN 13523-13:2014：

This standard specifies the procedure for determining the behavior of an organic coating on a metallic substrate when submitted to accelerated ageing by heating at a defined temperature for a defined period of time. It provides a basic test method for evaluating the effect of heat on the coating, although it may not cover all possible conditions of use. Special applications might require additional tests or properties to be checked, which should be agreed upon by the interested parties.

ISO/TS 16688:2017：

This document provides guidelines for the selection of coating types, tests, and methods of assessing the performance of coated aluminium in architectural applications. It includes considerations for radiation and heat resistance testing, among other performance aspects related to coated aluminium products used in building applications.

I hope this article can be of assistance to you. It presents a comprehensive overview of the heat resistance testing and assessment methods of colour coated aluminium coils. By understanding these details, you can make more informed decisions regarding the quality and performance of such coils. Whether for industrial applications or research purposes, this knowledge is valuable for ensuring the reliability and durability of the products.