Corrugated paper is a packaging material created by combining smooth and corrugated base papers with gluing and can be made in various quality. The corrugated paper used for our products can be 3, 5 or 7 layers. In addition, there are also 2- or 4-layered corrugated papers for other uses, these are called fluted paper.
It is common in english speaking territories that the corrugated paper is identified by the number of the corrugated sheets included. Therefore we can talk about single-wall, double-wall and tri-wall sheets. These are the same as the 3-, 5- and 7-layer papers we use.
Quality
The quality is determined by the type of the base papers used (composition), their basis weight and the type of fluting used during production.
Base paper grades
Basically, 4 types of basic paper are used and their special versions (e.g. white papers).
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Kraftliner (KL)
high-quality base paper with strong bearing capacity and easy printability does not contain recycled paper or only in special cases
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Testliner (TL)
generally used all purpose base paper contains recycled paper in varying proportions depending on its quality (~30-70%)
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Wellenstoff (WS)
recycled base paper commonly used for fluting
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Srenz (S)
base paper made from 100% recycled mixed paper with weak physical parameters
Basis weight
Mass (weight) of 1 m2 of paper in grams, unit of measure: g/m2 The higher the basis weight, the more resistant the paper is considered to be.
Composition
Corrugated paper sheets can be produced in countless variations based on a matrix made up of base paper grades and different basis weights. With this method we can specify the composition, which includes the corrugated, (middle) and cover layers of the base papers used in the material. e.g. KL100/WS100/TL100, where the letters indicate the base paper grades and the numbers indicate the basis weight of the material. The variety is further expanded by the use of different types of fluting, with which we can further refine the production of paper plates with properties that best suit our purposes.
Corrugation (fluting)
Fluting is primarily classified based on the height. The most used flutings at our company are the following:
B ~ 2,5 mm
C ~ 3,66 mm
E (microflute) ~ 1,5 mm
The thickness of a paper containing more corrugated layers is determined by the overall height of the flutings in them, such plates for example:
BE ~ 4 mm
BC ~ 6,16 mm
AAC ~ 13,66 mm
In addition other corrugations are also available (e.g. A, D, F and others), but these are less common in Europe and Hungary.
The density of the fluting distribution, i.e. the number of fluting per running meter, - in addition to the overall phísical characteristics - also affects the quality of the surface's printability.
When specifying the size of the base board, the wave direction and the running direction must be taken into account.
FLUTE DIRECTION: the side parallel to the flutes (width of the sheet)
CHOP: the side vertical to the flute direction (length of the sheet)
Upon request, our company prepares technical specifications for the products and raw materials, which include the properties of the given product and raw materials, general packaging information and various commonly used test values, such as:
ECT (Edge Crush Test)
Dimension: kN/m
It specifies the resistance of the paper to the compressive force applied to the (vertical) flute direction. The compressive strength of the corrugated paper sheet is very high. It plays an important role in the stackability of the corrugated box. As the thickness and width of the paper increases, the compressive strength also increases.
Burst (or Mullen Test)
Dimension: kPa
Burst strength determines how well the packaging can withstand internal (from the packaged goods) and external pressure. The paper sample is subjected to increasing hydraulic pressure until it bursts.
PET (Puncture Energy Test)
Dimension: J
PET indicates the energy required to penetrate the plate. The corrugated paper can be punctured if the contents of the package or an external object impact it. As a result, the strength of the packaging may decrease, the contents may spill out and the aesthetic appearance may deteriorate. We can get information about this property by measuring the penetration energy.
In the optimal case, these parameters are the same as the nominal value of the corrugated sheet used for box production, but as a result of the processing operation, usually they are minimally less, since the raw material is exposed to the forces of the machines (compressed during the manufacturing process and printing).
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