In this blog post we'll explore Shear Adhesion Failure Temperature (SAFT) in hot melt adhesives. SAFT is a critical property that plays a significant role in whether an adhesive stays put when things get hotter. In this article, we will delve into the concept of SAFT, its testing process, and highlight its importance in hot melt adhesive applications.
Before we delve into the details, we have prepared a short video that briefly explains Shear Adhesion Failure Temperature and common problems associated with it.
Now, let's proceed with a comprehensive overview of SAFT and its significance in hot melt adhesive applications.
Understanding SAFT in Hot Melt Adhesives
Shear Adhesion Failure Temperature (SAFT) is a critical property for hot melt adhesives as they are extensively used in applications where they are subjected to elevated temperatures.
In various industries, hot melt adhesives are relied upon for their fast-setting properties and excellent bond strength. However, their performance at high temperatures is a crucial consideration, especially when applications involve exposure to heat or temperature fluctuations.
Testing SAFT in Hot Melt Adhesives
It is important that the SAFT of a hot melt is tested for products that may get exposed to hotter temperatures in its journey to the end user.
The SAFT test for hot melt adhesives follows a specific procedure to determine the failure temperature as temperatures rise. Here's an overview of the SAFT testing process for hot melt adhesives:
Specimen Preparation: Samples of the hot melt adhesive are applied between two substrates, in the pictures shown these are cardboard, but they change depending on each application.
Curing: The adhesive is allowed to cool and solidify, creating a strong bond between the substrates.
Testing Setup: The bonded substrates are securely fixed in an oven, with a known weight attached to them - typically this is either a 500 gram or 1000 gram weight.
Temperature Ramp-up: The test starts at ambient temperature, and the temperature is then increased by 1°C per minute through use of a technical computer program. This ramp-up continues until the adhesive joint fails due to shear stress and the weight drops. When this happens, the weight hits a sensor on the oven floor which records the oven temperature, which will also therefore be the failure temperature of the adhesive.
Failure Detection: During the test, the program continuously records the temperature and identifies the exact degree at which the adhesion fails.
SAFT Determination: The temperatures are captured on the above screen - typically several samples of the same grade would be run to get an average.
Importance of SAFT in Hot Melt Adhesive Applications
Knowing the Shear Adhesion Failure Temperature of a hot melt adhesive is crucial for selecting the appropriate adhesive for specific applications. High SAFT values indicate that the adhesive can maintain its bond strength and integrity at elevated temperatures.
This property is particularly vital in applications where the adhesive will encounter high temperatures during the product life - such as export across the equator, washing machine temperatures, hot weather etc.
By understanding the SAFT of hot melt adhesives, you can ensure that the chosen adhesive will perform reliably, even under demanding environmental conditions, reducing the risk of bond failure and potential product defects.
Shear Adhesion Failure Temperature (SAFT) is a crucial parameter to consider when working with hot melt adhesives. It provides critical insights into the adhesive's performance and reliability at elevated temperatures, which is particularly important in applications where exposure to heat is expected.
If you have experienced issues with your hot melt adhesive and you think it may be linked to the adhesive failure in the heat, then please get in touch to see if we can help choose a grade which gives higher temperature resistance to give you peace of mind that your product will stay bonded when things heat up!
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