How to test the adhesive strength of tape

Different standards have been devised to test the properties of adhesives. First, there are the standards like the American Society for Testing and Materials (ASTM), the FINAT, the AFERA, and PSTC. All of these organizations uphold the bar in any adhesive-type industry.

Aside from the above standards, there are practical applications and tests that anyone can perform to check if their products measure to the same standard as the industry. But before we delved into that topic, let's understand how scientists have discovered adhesives.

The Gecko and its adhesive toe pads

Photo source: Youtube

In 1993, a Masters student of Biology at the University of Akron, Stephanie Lopez, have discussed how a gecko inspired the polymer scientists in their school to invent different types of adhesives. 

While studying geckos, they realized that they could stick to any surfaces without any liquid, and the bond is strong. They have concluded that Gecko's microscopic hairs on its feet can bend fill the uneven spaces on a surface resulting in its strong bond. 

They then developed gecko-inspired adhesives that are dry, reusable, not time-sensitive, and can work in a vacuum to also use this in the space program.

What are the different types of adhesives, and what does adhesive tape do?

Adhesive tapes are materials used to join objects together instead of using screws, fasteners, or welding. It is usually used to lessen the manufacturing process. Also, adhesive tapes are the most gentle alternative not to damage any surface when applied. 

There are different types of adhesive tapes in the market for various applications. Here are some of the types of adhesive in the market:

1. Pressure Sensitive Adhesive Tapes. This type of adhesive is the most common type, which bonds directly to the surface. PSAs use thinner and lighter materials and used in different applications in daily life. 

One of the most common examples of a PSA is the Double-Sided Tape and Carpet Tape. Double-Sided Tapes can adhere to almost any surface, may it be smooth, rough, or uneven surfaces. On the other hand, Carpet Tape is specially made for carpet to floor, carpet to carpet, rugs to carpet, and other applications. 

2. Water Activated Tapes or the Gummed Paper Tape. This adhesive is a starch-based adhesive that becomes sticky when moistened. There are also some advantages of using water activated tape. Top on the list is it forms a powerful and secure bond. It also creates a tamper-evident seal that shreds if pulled before delivery. 

The XFasten Gummed Tape is also popular for its fiberglass backbone that secures each package and acts as a good base for the bottom of the boxes. 

3. Non-Adhesive Tape. Non-adhesive tapes, commonly known as self-adhering tapes, include protective films, stretch wraps, hook-and-loop, etc. 

The XFasten Hook and Loop Tape is an industrial-grade tape that's easy to install and allows you to attach and detach objects repeatedly.

So, how to test the adhesive strength of a tape?

That's a question that's really hard to answer. There are different ways of testing each adhesive's stickiness. There are many technical terms that you will encounter, like cohesion, adhesion, and tack. Let's define the terms first before we proceed with the testing process.

According to ACS Chemistry for Life, Adhesion describes how strongly the tape and the surface bond. On the other hand, cohesion is how strongly the molecules on the adhesive attract and hold on to each other. And lastly, tack is how quickly a bond forms between the surface and the tape. 

So, how do you test adhesive strength if you do not have the equipment? 

Students at the University of Akron proposed an experiment on how anyone can test adhesive strength without machinery. Here's the step-by-step procedure and materials based on the experiment to test adhesive strength.

Step 1: Prepare the following to set up a measuring device on the testing board. You need a tape measure or ruler, a testing board (approximately 12" X 24"), and a pencil. To start, place the tape measure on the board and begin marking the inches on the length. 

Photo source: Youtube

Step 2: This is for adhering the testing tape to the board. You need scissors, the tape you are going to test, and an object to elevate the testing board. Cut 1-pc 14" of the tape and 2-pcs 3" tape. Attach the tape on the testing board; the sticky part of the adhesive should be exposed. 

Photo source: Youtube

Step 3: This part is the testing part. You need to prepare marbles and a protractor to get the exact angle. Each tape should be tested in 0 degrees and 90 degrees. Start to roll the marble down the test track. The marble should be set lightly on the tape because pushing it firmly will compromise the result. This roll test should be repeated three times; record the length that the marble traveled; then find the mean distance.

 
Photo source: Youtube

Note that the farther the marble rolls down the test track, the weaker is the sticky tape.

This adhesive roll test is just one of the ways to check if the product is worth your money or not. Remember that two kinds of forces break the bond of the adhesive and the surface - shear force and peel force. Shear pulls parallel to the surface while peel pulls in a direction perpendicular to the surface.

If your project is attaching an object to the wall, you will choose an adhesive with strong shear force. On the other hand, if you'd like to paint your walls and want a removable adhesive, your tape should have low peel strength.