How to calculate the Bursting Factor of Paper and Corrugated Sheets

Bursting factor is the property of materials like paper and cardboard that gives very crucial information about the quality as well as strength of the materials. In the packaging industries, there is a vast variety of materials that is used for packaging a plethora of products in different industries. In order to ensure the best safety and quality of the products, it is essential that the products are given the best level of quality when it comes to packaging. When we are talking about packaging, it is essential that packaging is sturdy, rugged and strong enough so that it could ensure the best level safety and security to the products inside during the time of storage, handling and transportation. The industries that use the paper and corrugated boxes for packaging of products include textile, food processing, pharmaceuticals and many more. In order to ensure the best level of safety of the products, the manufacturers of packaging materials as well as the products must test the quality of the outer packaging used for the products in industries. There is a long list of tests that can be used for assessment of strength and quality of packaging materials. One such test is termed as Mullen’s test or Bursting strength test that can give the best assessment of the strength of the packaging materials that are being used for manufacturing the packaging containers for industrial goods. This test gives the resistance of the materials against a bursting test that can be applied on the materials during various stages of delivery. With the help of this test, the manufacturers of packaging materials and containers can easily analyze the strength of their products and can ensure that they are delivering the best quality products to the clients that will provide best safety to their products during transit and handling.

What is Bursting Strength?

Bursting strength of a material is that resistance that a material offers to the forces applied on when the force applied is coming from all the direction and is uniform in nature. It is measured as the maximum amount of force that a material can bear before its rupture. When a bursting force is applied on the materials like paper and corrugated sheets, it can cause the surface of the material to rupture. This force can be uniform from all direction or can be distributed unevenly. Now the main concern is that every industry has different packaging needs and hence there is different requirement of strength of packaging materials for different industries. This is why, the manufacturers of these materials need to keep in mind that only with right assessment of the packaging materials, and it is possible to provide the most optimum strength of the materials to the customers. For example, the paper used for wrapping the products needs to have a very low bursting strength as they don’t have to face very high amplitudes of pressure during their handling and transit. But at the same time, it should be able to bear the bursting force applied on it however smaller its amplitude be. On the other hand, the cardboard and corrugated sheets that are used to manufacture the outer packaging of the products need to have a much higher bursting strength as they are subjected to much fierce amounts of forces when they are stored, stacked or transported. If they fail during this time, it can pose a very great threat to the quality and integrity of the products that are packaged inside them. Hence the manufacturers of these materials need to ensure that they test the strength of these materials so that the best level of safety of the products could be ensured during stacking and transit. The accuracy and precision of the testing procedure is also a very important aspect to decide the bursting strength of the materials. Wrong testing data can lead to botched strength and hence can compromise the quality of the packaging. Additionally, if the packaging is made too strong than needed then it can be a monetary loss for the manufacturers. The same is the case with the industrial fabrics that are used for purposes where they have to bear much higher forces such as parachutes. Here also, the fabrics need to be of very high strength so that they could easily fulfill the purpose of their usage without failing.


Bursting Strength Test or Mullen Test

Mullen test is the testing procedure that is used for determining the bursting strength of any material. This can be very helpful in calculating the capacity of the packaging boxes and containers. The Mullen test gives the value of the force that is required for a material to burst or rupture. This value of force is very useful in calculating the strength of the material against the bursting force or rupture force. However it cannot be an indicator of its performance or how much products can be put in the container as it is decided by the construction of the container. To calculate the overall strength of the corrugated boxes and containers, There are several other values needed along with Bursting strength such as Edge Crush Test value and Ring Crush Test Value.

Bursting Strength Calculation

The bursting strength of any material like fabrics, cardboards, paper or any similar material is very important to determine as it mainly impacts the performance of the final products. This is why, there is a need for very high level of precision and accuracy while determining the bursting strength of the specimen. When it comes to testing the bursting strength, the best instrument must be chosen to calculate the force. The very sophisticated mechanism is required to attain such level of precision. The instrument that can be used for testing the bursting strength is called the bursting strength tester. It uses the hydraulic pressure to apply the force that is transferred to the specimen with the help of a rubber diaphragm. This ensures a uniform distribution of force during testing so that the best accuracy of results could be ensured. When the test machine is chosen, it should be ensured that the instrument is capable of producing the results again and again so that its accuracy can be considered credible. The easy operation of the instrument is another feature that needs to be kept in mind when choosing the machine. A complicated operating procedure can cause the test results to deviate from expected.

Relation Between Bursting Strength and Bursting Factor formula

When the bursting strength of the specimen is calculated, it becomes very easy to determine its bursting factor as well. The both properties of a material are correlated and can have a great impact on the quality of materials and hence the performance of the end products. The Bursting strength can be used for calculation of the burst factor with the help of a formula. The bursting factor expressed in the terms of bursting strength as the measure of strength per unit GSM of the material.

Corrugated Box Calculation Formula

Once the bursting strength of a specimen is determined with the help of Mullen test or Bursting strength tester, it makes it very easy to determine the burst factor with a simple formula. The bursting factor formula is expressed as

Burst factor = Burst strength (gf/cm2) / Grammage (grams/m2)

Here the bursting strength is the value determined through Mullen test and the grammage is the measure of the weight of the material in grams per meter square of the material. Along with burst factors, one can also calculate the burst index of the material with the help of a simple formula. The burst index of the material is measure of the bursting strength per unit of grammageand is expressed in the terms of pressure. The formula for bursting index is expressed as

Burst Index = Burst strength (kPa) / Grammage (Kg/m2)

With the help of these formulae, it becomes very easy to find out the critical information about the properties of the material that can affect its ability to bear the forces applied on them during usage. These formulae are applicable on a variety of materials such as textile fabrics, paper, corrugated sheets and cardboards sheets. A higher burst index or n=burst factor indicates higher quality and performance of the products. The manufacturers can use these values to increase or decrease the quality of the products. These factors are also used for determining the prices for the materials in the open market.

Performing Mullen Test or Bursting Strength Test

The first step towards finding the bursting index or bursting factor is to determine the bursting strength of the material with the help of Mullen test. This test must be performed as per the guidelines given in the standards such as ISO 1060 and ASTM D-3876. Here are the steps to perform the Mullen test using a bursting strength tester.

1. The first step is to prepare the specimen for the test. To prepare the specimen, a round piece of sheet is cut from the material. The size of the sound piece cut must be greater than the diameter of the annular clamps in the instrument. As the size will be greater, there will be better hold of the clamps on the specimen without a chance for slippage.
2. The instrument is plugged in a prescribed electrical socket.
3. The specimen is placed in the clamp and the clamp is tightened properly. It needs to be clamped in a proper manner so that there is no chance of slippage.
4. The machine can be started for starting the test. The push button is used for starting the application of hydraulic force on to the diaphragm. This force is transferred from the diaphragm to the specimen.
5. The force is increased until the specimen is ruptured. Once there is rupture in the specimen, the force application is stopped immediately and the peak force is recorded in the gauge provided with the machine.
6. The specimen is replaced with new one, in case there is several other specimen to be tested.
The instruments are provided with either the digital display or an analogue meter which ensure accurate reading of the applied force on the specimen and hence give it bursting strength. This value is used for calculation of bursting factor and bursting index.

Relevance of Bursting Factor

The manufacturers of products such as packaging materials need to keep in mind that they cannot afford to compromise with the quality of the products as bad quality of packaging is a threat to the quality of the products also. The bursting factor is also an important aspect that impacts the efficiency of the packaging used in the industries. With the help of the burst factor, one can analyse the ability of the material to survive the forceful environments and protect the products from different threats such as dust, moisture, and forces that might damage the integrity of the products as well.

Better Bursting factors ensure that the packaging materials will stay intact during their transportation process and ensure the best safety of the products as well. The bursting factor is not only applicable to the paper and packaging (Paper Testing Instruments)materials but it also impacts the quality of the fabrics that is used in various industries for various purposes. In industries where fabrics are used, it required that the fabrics must have the best quality as well as have best strength so that they could perform well in the industries. If the low strength fabrics are used in the industries, they can easily fail as there are many fierce forces acting upon the fabrics. The bursting strength of fabrics must be tested before using them for any sort of industrial purposes. With the help of this test, the manufacturers can be assured of the fact that the fabric will be able to withstand the forces and will provide the best performance even in the harshest working conditions.

The bursting strength plays an important role in determining quality of the materials and hence helps in calculation of the burst factor and burst index of the materials.

How to increase bursting strength of corrugated box?

As we can see from the formula of the bursting factor is directly proportional to the bursting strength of the material. In order to increase the bursting factor, the construction and composition of the material needs to be changed. The corrugated sheets have several layers of corrugated paper that give the required strength to the materials. There are several types sheets such as double faced, single faced and triple faced sheets. The manufacturers of the products need to understand that to increase the bursting strength of the corrugated sheets, there needs to be an addition of layers to attain the required strength and hence ensure better performance of the end products. Similarly to increase the bursting strength of fabrics, the weave pattern and the yarn used for the fabrics can be changed to increase the strength. Although the bursting strength gives very significant amount of information about the quality of the products, but in order to ensure the best quality and strength, there are several other tests that must be conducted to ensure best quality of the products such as edge crush, ring crush test, puncture resistance, water absorbency and so forth.

Quality control With Bursting Strength

Better quality is the goal of every manufacturing unit. Along with better quality, there is also a need for optimization of manufacturing processes and the profits of the business. Bursting strength can help in better quality control as we know the strength of the materials, we can ensure that it is enough to provide better protection. The manufacturers can easily make changed is in the manufacturing process to increase or decrease the strength of the materials and have a better quality control. The bursting strength and burst factor calculation helps the manufacturers in having the best manufacturing process and prevent addition of more than required material during manufacturing and hence ensure better profitability by optimization of the manufacturing process.

Bursting Strength Tester Formula

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Bursting Strength Tester by Pacorr
Pacorr is one of the most prominent bursting strength tester manufacturers and suppliers offering a wide range of products including high precision testing instruments for paper and packaging industries. The bursting strength tester offered by Pacorr comes with a very sturdy design and make which makes it ideal for bearing the rugged handling and harsh working conditions. The instrument comes with a two options that are analogue and digital displays. High grade rubber is used for making the diaphragm of the instrument. Lab grade glycerine is used for exerting hydraulic pressure on the specimen. The annular clamps that are incorporated in the instrument have serrated teeth that make it impossible for the specimen for slippage. With this instrument installed in the industries, the manufacturers can easily determine the quality of their products and hence can avoid losses due to rejection. Additionally, with better quality assurance, it becomes easier to bring confidence of the customers in the brand.