Evaluation of conformity specific migration (SML)/ NIAS- Screening/ Single substance analyses/ GC- MS- analysis Overall migration (OML), Sensory analysis, colour fastness, microbiology Expert opinions and assessments (e.g. damage analyses), custom tests Mechanical/ technological properties Material analysis optical tests permeation

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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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Your contact person

Matthias Böhne

+49 441 94986-11

matthias.boehne@innoform.de

Information about tests

Curling or flatness

Standardprüfungen

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Examinations in this area