Evaluation of conformity specific migration (SML)/ NIAS- Screening/ Single substance analyses/ GC- MS- analysis Overall migration (OML), Sensory analysis, colour fastness, microbiology Damage resp. complaint analyses Mechanical/ technological properties Material analysis optical tests permeation

Information about tests

Curling or flatness

The curling of sheet materials depends generally on temperature and conditioning state. So multilayer materials made of materials having different coefficients of thermal expansion or unequal expansion/shrinkage due to deviating hygroscopic tendency may tend to curl caused by a kind of bi-metall effect. In addition to that excessive mechanical stress in the processing of rolls can lead ot curling.

test method:	Mechanical/ technological properties
Norms:	DIN 55403 (2014-07)
Needed sample size:	Small reel (if not available: film stack or hand roll without folds, creases and contaminations)

Standardprüfungen

flatness: cross section method
When materials with strong curling tendency have to be tested this method differentiates better than the methodologically similar circle method. A diagonal cross cut is made in the film, and the sample is stored. The direction of curling and the distance between the tips of the cross cut are recorded in [mm]. The measurements are carried out in standard climate at 23°C and 50% relative humidity and are well suitable for material comparisons. Measurements under varying climatic conditions are possible for an additional charge, please contact us.
Norm: DIN 55403

flatness: flatness temperature
This method is useful for determining the flatness temperature of multi-layer films, which are produced by usage of individual layers with different coefficients of thermal expansion. This can cause a tendency to curl in consquence of temperature variations ("bimetaleffect").
Norm: DIN 55403

flatness: circle method
A circle cut with a diameter of 113 mm is stored, the direction of curling and the edge distance in [mm] is measured. The measurements are carried out in standard climate at 23°C and 50% relative humidity and are well suitable for material comparisons. Measurements under varying climatic conditions are possible for an additional charge, please contact us.
Norm: DIN 55403

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