For those who are not aware, kraft paper is the most commonly used and the strongest packaging material. It is prepared using 80% of the pure kraft fibers obtained by the chemical sulfate pulping process. Due to its high potency, it finds use in applications where optimum strength is required. For example, plain wrapping paper, grocery bags, industrial bags, etc.
Besides, this paper is highly resistant to tearing, stress, and puncture, and therefore kraft fibers are used to make liners of complex corrugated boxes.
Types Of Kraft Papers
- White Top
The white top kraft paper is a two-ply product. The first or the top play consists of 100% bleached hardwood kraft fibers and the base ply consists of unbleached softwood kraft fibers. This paper is used for premium quality printing and packaging industrial products, food, beverages, and consumer goods. (Check the printability of the kraft paper with UECIN’s Printability tester)
The brown kraft paper is also a two-ply paper. However, here the top ply consists of 100% unbleached softwood fibers, and the base has a blend of unbleached softwood fibers and premium quality recycled fibers. Just like the white top, the brown paper also serves excellent printing quality and strength.
Unlike both the above papers, virgin kraft paper is a one-ply product made with virgin wood fibers. Corrugated boxes with single or more flutes use this kraft paper as liners for both the top and base. This is because it has high resistancy to moisture, pressure, tearing, and puncture.
The Most Significant Tests For Kraft Paper
A kraft paper goes through multiple tests during the tenure of its manufacturing. These tests include the following:
- Cobb Value
A cobb sizing tester is used to evaluate the cobb value of the kraft paper. In other words, this test measures the water absorptiveness of the kraft paper, i.e. the amount of water absorbed by the paper in a certain amount of time. This test is essential in order to determine if it can hold or protect a particular product when exposed to water.
- Tensile Strength
Just like any other paper, kraft paper is also tested for its tensile strength. This test evaluates the maximum pressure or stresses a kraft paper can withstand before it breaks.
- Burst and Tearing
The burst and tearing are among the most widely used strength measuring factors for the kraft paper. This test determines the maximum strength that paper can resist until it bursts or tears.
GSM or grams per square meter refers to the basis weight of the kraft paper. This factor is essential to test as different gsm thickness is required to serve different package needs. The gsm of a basic kraft paper ranges between 180-500.
- Load Bearing Capacity
A load-bearing capacity test is performed to know the load-bearing capacity of a bag made of kraft paper. In other words, this test ensures that the right product is put in the bag of the right capacity and not the one which cannot carry it effectively.
Testing the kraft paper can get easy with the right testing equipment. Get in touch with UECIN to source suitable testing machines for your business and take your products to the next competitive level.