Adhesive Testing

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When it comes to adhesive testing, finding the right solution is crucial for ensuring product quality and performance. That's where our expertise and extensive range of adhesive test machine solutions come in.

We take pride in offering a diverse selection of products, making us your go-to source for all your adhesive testing needs. From peel strength testers to shear testers, we have more products than anyone else in the market.

Our team of adhesive testing experts is dedicated to helping you find the right solution that meets your specific requirements.

What is an Adhesive Test?

The purpose of adhesive testing is to determine the suitability of a substance for a specific application. Adhesives are often subjected to various forces and stresses throughout their lifespan, with shear, tension, peel, or a combination of these being the most common.

By testing adhesives, we can determine their strength, which can be summarized by their tensile strength, shear strength, and peel strength. Each of these measures the point at which the adhesive fails under specific forces. During adhesive testing, one of three types of failures may occur. The adhesive may fail in cohesion, where the actual adhesive material is ruptured. Alternatively, it may fail in adhesion, where the adhesive is cleanly separated from the bonded surface. Lastly, it may experience a combination of both adhesion and cohesion failures.

How to Perform an Adhesive Test?

There are many different methods for the testing of adhesives but the most popular involve tensile, shear, and peel forces. The tensile testing of adhesives is generally performed for two different situations: the bonding of two rigid substrates and the bonding of a flexible and rigid substrate.

Tensile testing of two rigid substrates bonded together with an adhesive requires that both substrates be gripped properly and pulled apart at a constant rate until either the adhesive or the substrates fail. For a flexible to rigid bonded assembly, a loop tack test is used for the testing of tensile properties. The rigid substrate is gripped at the bottom while the flexible substrate is formed into a loop with the adhesive facing out and gripped from above. The flexible surface is then adhered to the rigid surface and then pulled straight up so that the two materials are separated cleanly.

Shear testing of adhesives generally involves a single or double lap joint and a universal shear testing machine. The adhesive is applied to the joint between the two materials so that one continuous length is formed. The two ends of the new sample are then placed into their respective grips in the shear tester. The tensile shear tester is then used to apply a load to the joint until it is ruptured in shear.

A peel test is used for the testing of the bond of the adhesive between a flexible substrate and a rigid substrate or two flexible substrates. When a flexible material is bonded to a rigid material either a 90 or 180-degree peel test will be used. These two tests involve the flexible substrate being bent to the required angle and then pulled away from the rigid substrate breaking the adhesive bond between the two. If two flexible substrates are bonded together the common test method is the T peel test in which the sample is loaded into a tensile tester in a manner that causes one substrate to point upwards and the other to point downwards effectively forming a &#;T&#; at the joint. The peel tester then pulls the two substrates away from each other destroying the bond in the process.

Get a Complete Adhesive Test Solution

Completing your adhesive test system is easy. Simply start by choosing a test machine, choose your accessories, and select your controller software. We are your one-stop shop for all your adhesive testing needs.

Adhesive Testing Machines

Universal test machines specifically configured for testing adhesives.

Newton Universal Test Software

From simplified test setups to an intuitive controller software interface and pre-configured methods for industry standards - this innovative technology ensures that your adhesive tests are conducted seamlessly and with precision.

Accurate & Repeatable Test Results

• Simple test setup, operation, and reporting
• Flexible and scalable software packages - Get what you need now with room to grow!
• Prebuilt test methods for many of the most common application-specific testing standards (like ASTM D904, ASTM F88, or Tack)

High-performance and easy-to-use controller with logical workflow design

With an intuitive interface, Newton makes it easy for users to navigate through various options and settings, ultimately enhancing the overall user experience. By streamlining complex procedures into user-friendly steps, this software serves both experienced test engineers and beginners alike to conduct tests with confidence and accuracy.

Due to the massive selection of products that we offer, it can be difficult to narrow down what you need. Let us help you select and configure based on your testing application.

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Adhesive Testing Accessories

General Purpose

Choose from 100's of standard adhesive test accessories as well as custom solutions. All of our adhesive fixtures will fit any brand of test machine through the use of an adapter.

Specialized Adhesive Testing Accessories

In addition to our general purpose accessories we have fixtures specifically designed for testing adhesives.

Use the tables below to search for the fixture that matches your sample the best. Can&#;t find what you are looking for? Contact us. We are confident we have what you need.

Talk to one of our Engineers to help you navigate the vast selection of adhesive testing accessories to find the perfect fit for your testing application.

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Adhesive Testing Standards

There are numerous adhesive testing standards available, with some of the most common ones being ASTM D897, ASTM D, and ASTM D. If you have a specific standard that you will be using, please refer to this table to find and learn more about the products we recommend for that particular standard.

I am a HUGE fan of the test fixtures, clamps, etc. from TestResources. The quality is about the same as our Tinius Olsen, and looks similar to Instron, for a FRACTION of the price. The different brands are largely interchangeable (we use the pin connection for attaching clamps).

When anticipating using adhesives in structural bonding, a common need is developing the testing protocol to demonstrate bonded system effectiveness. While pressure-sensitive tapes are used in structural joining, this discussion will focus on liquid, paste, and film adhesives in structural joints.

There are three questions to consider: What is the adhesive expected to do; what conditions will it encounter, both mechanically and environmentally; and what is the risk to the system or subsystems if performance degrades over time and exposure?

Adhesives bond to substrates and have intrinsic mechanical properties differing from those of the joined materials. For modeling purposes, adhesive properties must be known to the end user and to its vendors, including:

• Bonding characteristics and the expected range of application dynamics
• Specified adhesion values relative to the substrate and joint design
• Surface stability under adverse conditions

Another consideration is the joint design incorporating the adhesive. Adhesives perform best in compression or shear. They perform poorly in peel, so peel resistance for the joint may require rivets, welds, or crimping to augment peel performance. Good joint design converts tensile loads into shear or compression. Tensile loading frequently offsets into multi-axial loading, resulting in peel. Butt joints and perpendicular T-joints should be avoided.

Proper use of joint and structure modeling cannot be overemphasized. Considerable time and random testing can be circumvented, resulting also in significant materials and labor savings. In the absence of modeling ability, many more samples must be produced and broken to achieve statistical significance. With modeling, it suffices to produce a few exploratory samples for data input to the modeling, and then to build a few proof samples to confirm, deny, or modify the model.

Test Selection

So, what kinds of tests should be run? Table 1 lists several representative tests grouped into four categories: basic tests of adhesive mechanical properties, shear tests of joints, peel tests of joints, and environmental conditioning. These are combined into a protocol based on the responses to the main questions mentioned previously.

The third question&#;considering risk&#;gives an indication of the degree to which safety is a mitigating factor under the most adverse circumstances. If a joint must provide at least a certain strength regardless of circumstances, it is wise to demonstrate an additional performance margin of 20% or even 50% under the worst expected conditions to mitigate that risk.

The most basic mechanical tests include ASTM D638 test for tensile mechanical properties of the cured adhesive, often referred to as &#;dogbones.&#; These can be environmentally preconditioned in many ways. Additional useful information regarding adhesive intrinsic mechanical properties come from dynamic mechanical analysis studies providing modulus vs. temperature, glass transition temperature, and creep information (D).

For shear tests, single-lap shear tests (D) are universal and widely adapted to meet specific interests (see Figure 1). Simple D samples are routinely used for screening and comparisons, but they do not provide suitable engineering data for modeling because of inherent peel introduction.

Double-lap shear tests, as illustrated in Figure 2, often produce superior data (D). These can be run in tensile or compressive modes and feature a center line of thrust, avoiding peel moments. Many tests are modified to suit a specific combination of substrates, surface preparations, and adhesive types. Each condition should be evaluated with 5-10 samples.

Single- and double-lap shear tests are often performed using baseline samples augmented by environmental stressing exposures, either cyclic or static with heat, and exposures lasting up to weeks. There are many humidity exposures employed, sometimes combined with UV exposure to identify &#;weathering&#; properties. The most common exposure to saline environments is the ASTM B117 Salt Fog test.

Peel tests are highly variable in outcome because of &#;slip-stick&#; failure modes, where the adhesive sequentially grabs and then zips in spurts. Output curves are quite noisy and require smoothing to get an average peel load. The two most common peel tests are D903, which has broad applicability, and D, known as the T-Peel Test.

Tapes require their own protocols, many of which have been adopted from criteria discussed here. Collected into recommended test practices of the Pressure Sensitive Tape Council (PSTC), they focus heavily on peel, tensile creep under load, and adhesive grab.

Developing testing protocols requires knowledge, experience, and even some art. Some companies develop their own series of test protocols based on field experience or specific end-use requirements. There are several laboratories available to assist with the development and implementation of test protocols. They will certify the results, if needed, or simply pass them along to the client for internal use. Ultimately, test protocols can be developed methodically and reliably based on the specific requirements of the end use.
 

Find testing equipment suppliers at www.adhesivesmag.com/equipmenthandbook.

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