Film Properties & Measurements

Percent Shrinkage

Figure 1 Image

Figure 1.
Click image to see larger image in new window.

The oven shrinkage test measures the area reduction of a 10-cm x 10-cm unrestrained film sample held at a given temperature and time (ASTM D1204). Film with a high percent shrinkage is ideal for wrapping irregular shapes and minimizing “dog ears.”

All Clysar films have balanced shrinkage in both MD and TD directions, which ensures tight packages and increases shelf appeal.

to top of pageGo to Top

Shrink Force

Figure 2 Image

Figure 2.
Click image to see larger image in new window.

Shrink force is the force exerted by a film, as it is restrained, while attempting to achieve full shrinkage at a given temperature. Shrink force, which represents amount of pressure exerted on product being wrapped, increases with film thickness.

A high shrink force gives window boxes a taut, wrinkle-free surface and provides stability for multipacking. A lower shrink force is desirable for wrapping delicate or thin packages that may deform or curl.

to top of pageGo to Top

Tear Strength

Figure 3 Image

Figure 3.
Click image to see larger image in new window.

Elmendorf tear is the force required to tear, by propagation, a notched film sample. A high tear strength helps prevent tear propagation when the film is punctured by uneven or angular product shapes, or needle perforations.

When using tear strips or specialty perforations, a low tear strength may be a desirable, easy-open feature.

to top of pageGo to Top

Tensile Strength

Figure 4 Image

Figure 4.
Click image to see larger image in new window.

Tensile strength is the force required to break a 1 inch wide film sample that is pulled between two grips moving at a fixed speed (ASTM D882).

A high tensile strength gives improved toughness and durability, high resistance to machine tension, and an easy adjustment for manual feeding operations. A low tensile strength gives increased puncture resistance and improved recovery/memory properties.

to top of pageGo to Top

Modulus

Figure 5 Image

Figure 5.
Click image to see larger image in new window.

Modulus is a measure of film stiffness or rigidity. The test is measured using a universal test machine (ASTM D882). A higher stiffness generally equates to faster running high-speed films.

A high stiffness (“hard”) film gives low elongation, outstanding performance on high-speed automatic shrink equipment and excellent printability. A low stiffness (“soft”) film gives a softer feel, less “rustle” or noise and improved conformance to package shape.

to top of pageGo to Top

Coefficient of Friction

Figure 6 Image

Figure 6.
Click image to see larger image in new window.

Coefficient of friction (COF) is a measure of how easily film will slip across metal surfaces or other film surfaces. COF is the ratio of the frictional force to the gravitational force between the two surfaces in contact (ASTM D1894).

When case packing warm products at high speeds, there is a tendency for the packages to not slip easily across each other in the case. Reduced COF of warm items can be achieved with a surface treatment on Clysar HPGS, Clysar EZS, Clysar LLGS, Clysar CHS, Clysar VEZS, and Clysar VHGS.

to top of pageGo to Top

Shrink Tunnel Temperature

Figure 7 Image

Figure 7.
Click image to see larger image in new window.

Clysar films have a wide range of shrinking temperatures, which makes them functional on many types of machines. These values can vary depending on tunnel characteristics.

to top of pageGo to Top