Mechanical properties of Lexan films

Zugverhalten

Zugfestigkeit, Dehnung und Zugmodul beschreiben das Verhalten einer Folie unter Zugspannung. Tabelle 8 nennt typische Werte für GE-Folien bei Raumtemperatur..

Table 8: Tensile behavior at room temperature

Tensile behaviour at room temperature

These properties are important when using adhesive tapes and when processing films from the roll.

Spannung und Dehnung

Spannungs-/Dehnungskurven illustrieren die Kurzzeitbelastbarkeit. Diagramm 2 zeigt eine typische Kurve mit Definition der Kenngrößen.

Diagram 2: Typical stress / strain curve

Typical tension-elongation curve

Stresses can be calculated using basic engineering equations for mechanical properties. The basis is Hooke’s law of elasticity, according to which the stress in the linear area of ​​the curve is directly proportional to the elongation. Above the proportionality limit, the material behavior deviates from this constant.

According to Hooke:

E= σ / ε

Where: σ = stress (N / mm2)
E = modulus of elasticity (N / mm2)
ε = elongation (mm / mm)

Like most thermoplastics, so do Lexan®, Valox®, and Ultem® a spring-back behavior in the case of tensile stress in the range up to the proportionality limit.
This means that the foils stretch and return to their original state when the tension is relieved. The associated dimensional differences
should be taken into account when printing and / or punching stretched foils.
With the following formula this behavior can be calculated or calculated relatively precisely. compensate:

ε = F / A x E

Where: ε = elongation (mm / mm)
F = train (N)
A = cross-sectional area of ​​the film
(mm2, width x thickness)
E = tensile modulus (N / mm2), temperature dependent

The value “E” changes with the temperature.

A corresponding reduction in width occurs under tension, which can be quantified with the help of the Poisson’s ratio. For Lexan® and Valox® Foils, this number is 0.38 (for Ultem®Foils 0.42
Multiplied by the elongation in the above formula, the result is the reduction in width.

Reißfestigkeit

Die Reißfestigkeit einer Folie entspricht der benötigten Kraft bis zur Rißbildung bzw. Rißausdehnung. Die Spannung wird notiert, und die Einreiß- und Weiterreißfestigkeit
normalerweise in Newton angegeben. Sie kann auch als Kraft pro Dicke ausgedrückt werden. Vergleiche zwischen verschiedenen Materialien und/oder Folien unterschiedlicher Dicke sind dann aber möglicherweise nicht aussagefähig. Tabelle 9 nennt Reißfestigkeiten, gemessen nach ASTM D1004 und ASTM D1925.

Table 9: Tear resistance and tear strength according to ASTM D1004 / D1925

tear resistance and –propagation strength

Frictional behavior

Valox® Due to their high smooth walls, foils is an ideal surface material for numerous load-bearing applications. Valox® also offers very low static and dynamic coefficients of friction in the
Contact with metals. Valox’s static coefficient of friction® Film, measured according to ASTM D1894, is 0.39.