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Testing of Thin Sheeting and Plastic Films

Plastic films have become an integral part of daily life. We use them to package food, carry our groceries home from the store, and cover vegetables grown in greenhouses and fields. Film packaging is common in the medical engineering industry and often saves lives. A wide variety of films are also used in construction. Moisture barriers ensure that our roofs do not leak and that water does not damage the walls of our homes. Sophisticated plastic films are used to cover sports arenas, opening up new possibilities for architects.

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Requirements for testing of films

Films today are high-tech products that have a wide variety of characteristics. Mass production uses cost-effective plastics, such as high- and low-density PE, PP, PVC, and PS. In cases where special characteristics such as toughness, permeability, or light resistance are required, high-quality polymers such as various polyesters, PTFE, or ETFE are used. Films such as EPDM and EVA are used to waterproof roofs. Multilayer films have various characteristics such as strength, impermeability in regard to gas and bacteria, and suitability for contact with food.

Thin sheeting with a thickness of up to 1 mm is a constituent material for many hollow bodies in packaging technology, which are formed by means of processes such as thermoforming or compression molding.

Due to the broad scope of film manufacture and its downstream processing, requirements of the applicable test method vary greatly. The objectives of the tests can be very different in nature.

In an incoming goods inspection, the first step involves testing raw material. This step determines the melt index—meaning the melt mass-flow rate—of plastic granulate.

In the second step, the plastic films are tested after the extrusion or blow molding process. In addition to testing film thickness, a variety of other mechanical characteristics are important. These are strength, strain, yield point, and the tensile modulus in the longitudinal and transverse directions of the film. Toughness is also important, which is determined during impact tests. In the case of multilayer films, adhesion between the layers is crucial.

Yet the focus lies on other characteristics during and after processing, including adhesive strength, weldability, and strength of adhesives and joints. If sharp objects are packaged, the puncture resistance of the film is measured. Understanding the coefficient of friction is interesting for packing machines or in film printing. Changes in light and moisture is also important when evaluating thin sheeting and plastic films.

Testing films with ZwickRoell

ZwickRoell testing systems are specifically designed for these requirements and address a wide range of mechanical tests:

  • Extrusion plastometers characterize the materials of incoming goods.
  • Universal testing machines provide accurate, reliable measurement of values for stress-strain characteristics, adhesion forces between two layers, coefficients of friction, penetration resistance and flexure characteristics.
  • Creep test benches measure the creep behavior at ambient temperature and at operating temperature.
  • Pendulum impact testers are used to determine impact strength values, typically in an impact tensile test.
Tensile test ISO 527-3 wafers and films

Tensile properties

ISO 527-3, ASTM D882, ASTM D5323
Standard-compliant determination of tensile properties on films and sheets to ISO 527-3.
to Tensile properties
Puncture test EN 14477, ASTM F1306 also known as Parker Ball-Point Test

Puncture Resistance

EN 14477, ASTM F1306
Puncture resistance is important when films are used as packaging material, for example, for food or parts with sharp edges. It is described in the following standards: EN 14477, ASTM F1306.
to Puncture Resistance
Static and dynamic friction behavior of films COF with zwickiLine materials testing machine and test fixture

Coefficients of friction COF

ISO 8295, ASTM D1894, JIS K 7125, DIN 53375
The COF provides information about the surface structure and printability. The static and dynamic coefficient of friction is particularly interesting for films that are further processed on packaging and printing machines.
to Coefficients of friction COF
Melt flow determination/melt index test ISO 1133-1/-2, ASTM D1238

Melt flow determination

Melt flow index (MFR, MVR, FRR); ISO 1133, ASTM D1238
Determination of the melt mass flow rate (MFR) and melt volume flow rate (MVR) to ISO 1133, ASTM D1238, and similar standards ZwickRoell produces straightforward extrusion plastometers for Method A, together with instruments which feature automatic displacement measurement and can be used for measurements to Methods A and B.
to Melt flow determination
ISO 4578, Finat FTM 9, EN 1939, AFERA 4001: Tear growth, peel, and adhesion characteristics of films and sheets

Tear growth, peel, and adhesion characteristics

ISO 4578, Finat FTM 9, EN 1939, AFERA 4001
Our materials testing machines are ideal for the determination of tear growth, peel and adhesion characteristics on films, and are used, for example, for pull-off tests to measure peel resistance, tests on sealed seams, initial adhesion of adhesive labels, etc.
to Tear growth, peel, and adhesion characteristics
Impact tensile test, impact tensile strength ISO 8256, ASTM D1822

Impact tensile strength

ISO 8256, ASTM D 1822
For ISO 8256 / ASTM D1822, ZwickRoell has the ideal pendulum impact testers for standard-compliant determination of impact tensile strength of films
to Impact tensile strength
Film magazine_automation_roboTestF

Automated Tensile Test

The roboTest F (clamp) robotic testing system is designed for tensile tests on non-rigid specimens such as films, textiles, and non-wovens.
to Automated Tensile Test

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