Plastic film testing
Plastic film has become an integral part of daily life. We use them it 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 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.
Various test methods are used for tests on plastic film to evaluate the material’s mechanical and fracture mechanics properties. In addition to the classic tensile test on sheets and films according to ISO 527-3 or ASTM D882, the determination of the coefficient of friction according to ISO 8295 / ASTM D1894 or the determination of tear growth, peel and adhesion characteristics according to ASTM D3330, among others, the most important test methods and test standards for film testing are described in more detail below.
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Testing films with ZwickRoell
Film testing has never been this easy!
Various tests are required to determine the characteristics of films:
- Tensile tests on films according to ISO 527-3 or ASTM D882
- Determination of the coefficient of friction according to ISO 8295, ASTM D1894, JIS K 7125 and / or
- puncture tests according to ISO EN 14477 and ASTM F1306
All these tests can be performed on the same ZwickRoell testing machine with fast conversion from one test type to another.
For efficient film testing you need:
- Easy and quick to open and close specimen grips for high specimen throughput with 100% quality assurance.
- Pneumatic grips with special jaw inserts that prevent specimens from slipping or breaking.
- Control of the complete test sequence, which is easily carried out via the control panel of the electronics.
- Constant gripping force for repeatable and 100% standard-compliant test results.
- Reliable test results, even when working with different machine operators who run tests with intelligent step-by-step instructions through our testXpert testing software.
Requirements for film testing in the film manufacturing process
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.
Incoming goods inspection of outgoing material:
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.
Film materials / film rolls or sheets
In the second step, the plastic films are tested after the extrusion or blow molding process. In addition to film thickness, various other mechanical properties are important when testing film. These include strength, strain, yield strength, and the tensile modulus in the longitudinal and transverse directions of the film. Toughness is also a significant characteristic, which is determined using impact tests on films. In the case of multilayer films, adhesion between the layers is crucial.
Film testing during the further processing of film materials:
For further processing of films and after further processing, the focus is on other features. This includes the bondability, weldability, that is the strength of adhesives and welds. If sharp objects are to be packaged, thpuncture resistance of the film is measured. Knowledge of the friction coefficients of plastic films is of interest for the operation of packaging machines or for the printing of films. Changes in light and moisture is also important when evaluating thin sheeting and plastic films.
Testing films with ZwickRoell
ZwickRoell testing systems are designed for these special requirements in film testing and cover a wide range of mechanical tests on plastic films:
- Extrusion plastometers characterize the material in the incoming goods department.
- Universal testing machines provide accurate and reliable measurement of values for stress-strain characteristics, adhesion forces between two layers, coefficients of friction, penetration resistance and flexure characteristics.
- Creep testing machines measure the creep behavior at ambient temperature and at operating temperature.
- Pendulum impact testers for tests on plastics are used to determine impact strength values, typically in the form an impact tensile test.
