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{{PSM_Infobox}}
Film testing 
__FORCETOC__

==General==

Various experimental methods of [[Polymer Testing|polymer testing]] and [[Polymer Diagnostic|diagnostics]] can be used to evaluate the mechanical and [[Fracture Mechanical Testing|fracture mechanical properties]] of plastic films. In addition to the basic [[Tensile Test|tensile test]] according to ISO 527-3 and, as a special feature, [[Peel Test|peel tests]], the methods described in more detail below are used to obtain information, in particular on the [[Toughness|toughness]] properties of the [[Material & Werkstoff|materials]] under investigation.

==Conventional impact and notched tensile impact test==

The aim of the conventional impact tensile test according to ISO 8256 ‘Plastics – Determination of impact strength’ is to examine the behaviour of [[Specimen|test specimens]] under relatively high impact [[Velocity|velocity]] and to evaluate the [[Toughness|toughness]] or brittleness (see: [[Fracture Types|fracture types]]) of films.

In principle, the [[Tensile Impact Test|tensile impact test]] (using unnotched [[Specimen|test specimens]]) and [[Notched Tensile Impact Test|notched tensile impact test]] (using [[Notching|notched]] [[Specimen|test specimens]]) are particularly suitable for testing materials for which [[Impact Test|impact]] and [[Notched Impact Test|notched impact tests]] according to [[Charpy, Georges|Charpy]] (3-point bending arrangement) are unsuitable due to the nature of the test specimens (thickness, flexibility). Very thin test specimens, e.g. those made of film or very flexible test specimens ([[Elastomers|elastomers]]), can therefore be subjected to impact stress (see also: [[Impact Loading Plastics|impact loading plastics]] and [[Impact Loading Free-falling Dart Test|impact loading free-falling dart test]]) and their toughness properties can thus be evaluated under impacting loading conditions.

The test is carried out in the [[Tensile Impact Test|impact]] and [[Notched Tensile Impact Test|notched tensile impact test]] at a relatively high [[Test Speed|test speed]] with the aid of specially designed [[Impact Loading Pendulum Impact Tester|pendulum impact tester]]. The method is suitable for [[Specimen|test specimens]] made from [[Moulding Compound|moulding compounds]], semi-finished products or moulded parts and is used, among other things, for production and quality control. With the conventional impact and notched tensile impact test, it is also possible to determine the mechanical [[Anisotropy|anisotropy]] behaviour by taking [[Specimen|test specimens]] from test plates or [[Component Testing|components]] in different directions and testing them.

For conducting such experiments, [[Polymer Service GmbH Merseburg]] has pendulum impact testers (Zwick HIT5.5P and HIT25P as well as Ceast Resil Impactor Junior) with the additional equipment required for impact tensile tests, such as pendulum hammers of various masses and clamping devices. The dimensions of the test specimens for determining the notched impact tensile strength ''a''tN are: Length ''L'' = 80 mm, width ''W'' = 10 mm, notch depth a of the notches on both sides 2 mm each. The test [[Specimen|specimens]] for determining the impact tensile strength ''a''tU are preferably shoulder bars with a length ''L'' = 80 mm, length of the parallel part of the web ''l''0 = 10 mm, web width 10 mm and shoulder width 15 mm.

To perform [[Tensile Impact Test|impact]] and [[Notched Tensile Impact Test|notched tensile impact tests]], the test specimens are fixed within the test device by means of a fixed clamping device on one side and a cross-head on the other (see '''Fig. 1'''). After the pendulum hammer is released from its swing position, the test specimens are loaded in the longitudinal direction until [[Fracture|fracture]]. The result of the experiment is the corrected impact energy ''E''c, which is used to determine the conventional notched tensile-impact strength ''a''tN or impact tensile strength ''a''tU.

[[File:Film_Testing_Fig-1.jpg|500px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px" |Schematic representation of the test setup for the [[Tensile Impact Test|impact]] and [[Notched Tensile Impact Test|notched tensile impact test]] with a fork-shaped pendulum hammer
|}

==Instrumented tensile impact test==

The [[Instrumented Tensile Impact Test (ITIT)|instrumented tensile impact test]] (ITIT) is performed with the aim of determining the fracture mechanics characteristics of [[Plastics|plastics]] in accordance with the MPK procedure ‘[https://www.polymerservice-merseburg.de/fileadmin/inhalte/psm/veroeffentlichungen/MPK_IKBV_englisch.pdf Testing of plastics – Determination of crack resistance behaviour using the instrumented tensile-impact test]’ (accredited standard of the MPK testing laboratory – Mechanical testing of plastics).

The [[Electronic Instrumentation|instrumentation]] of pendulum tensile impact testers, i.e. the attachment of [[Strain Gauge|strain gauges]] or a [[Piezoelectric Force Transducer|piezoelectric force transducer]] to record the load–time signal as a basis for calculating the load–[http://192.168.81.5/en-wiki/index.php/MPK-Procedure_MPK-ITIT extension] diagram, provides additional information for evaluating the [[Toughness|toughness]] properties. It is possible to define and evaluate different energy contributions to the total deformation and to determine [[Measured Variable|measured variables]] such as maximum load ''F''max and the associated deformation variable ''l''max. In the context of a material comparison or material optimisation, the measured variables provide important information for interpreting the determined [[Material Value|material values]] of [[Crack Toughness|crack toughness]].

For the tests, [[Polymer Service GmbH Merseburg|PSM GmbH Merseburg]] has access to the instrumented pendulum impact tester Resil Impactor Junior from Ceast (see image). This enables tests to be carried out to determine fracture mechanical characteristics on test specimens with [[Notching|metal blade notches]] on both sides ([[DENT-Specimen|DENT-specimen]]) in various energy and hammer speed ranges. The test specimens have dimensions of ''L'' = 64–80 mm, ''W'' = 10 mm and a total notch depth of ''a'' = 2 mm.

As a result of the [[Instrumented Tensile Impact Test (ITIT), Examples|instrumented tensile impact test]], fracture mechanical toughness parameters are calculated on the basis of the evaluated load–extension diagrams. These toughness parameters are preferably ''J''d values (see also: [[J-Integral Evaluation Methods (Overview)|J-integral evaluation methods (overview)]]), which quantify the resistance of the material under investigation to the propagation of an unstable [[Crack|crack]]. One advantage of these [[Material Parameter|material parameters]] compared to the notch impact toughness ''a''tN determined in the conventional [[Notched Tensile Impact Test|notched tensile impact test]] is, for example, their particular sensitivity to structure.

==Instrumented puncture impact test==

The [[Instrumented Puncture Impact Test|instrumented puncture impact test]] according to ISO 7765-2 is used to determine the [[Multiaxial Stress State|multiaxial]] impact behaviour of films. Falling weights with appropriate equipment for measuring the load–time signal are used for the experimental implementation. A selection of impact bodies and a temperature control chamber are available for the Fractovis device from Ceast with electronics from Coesfeld, which is available from [[Polymer Service GmbH Merseburg|PSM GmbH]]. This means that investigations can be carried out on the influence of temperatures from -70 to 150 °C on the impact behaviour under multiaxial [[Stress|stress]] (see: [[Impact Loading Free-falling Dart Test|impact loading free-falling dart test]]).

The instrumented puncture test is a metrological extension of the conventional puncture test and is used when a load–deformation diagram or [[Measured Variable|measured variables]] from this diagram are required for material characterisation. The load–deformation diagrams are recorded by the [[Electronic Instrumentation|instrumentation]] of the impact test body.

During the test, a film or a thin, plate-shaped [[Specimen|test specimen]] (square, 80 mm x 80 mm, or round, diameter 80 mm) is pierced perpendicularly to its [[Surface|surface]] by the impact test body at a practically constant [[Velocity|velocity]] (standard: 4.4 m/s), while the load–deformation diagram is recorded. This diagram can then be used to evaluate the material behaviour under impact stress. For example, the shape of the diagram (see '''Fig. 2''') can be used to distinguish between brittle, tough or very tough fractures (see: [[Fracture Types|fracture types]]).

[[File:Film_Testing_Fig-2.jpg]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px" |Schematic representation of different types of load–deformation diagrams from the [[Instrumented Puncture Impact Test|instrumented puncture impact test]]: brittle material with almost linear-[[Deformation#Elastic deformation|elastic]] deformation behaviour and unstable [[Crack Propagation|crack propagation]] during puncture (a); [[Ductility Plastics|ductile]] [[Material & Werkstoff|material]] with elastic-plastic deformation behaviour and stable crack growth during puncture (b) and highly ductile materials with predominantly stable crack growth (c): characteristic [[Measured Variable|measured variables]]: ''F''M – maximum load, ''s''M – deformation at maximum load, ''W''M – energy up to maximum load, ''W''T – total puncture energy
|}

In the diagrams in the '''Fig. 2''', ''F''F represents the damage load, ''s''F represents the deformation at the damage load, and ''W''F represents the damage energy.

Comparisons between individual materials can only be made using this method if the test specimen production, test specimen dimensions, surface quality and test conditions (see also: [[Surface Testing Technology|surface testing technology]]) are comparable. The thickness of the film or test specimen plays a particularly important role here. In addition to the qualitative evaluation of the load–deformation diagrams and the fracture appearance of the test specimens, the results of the [[Puncture Impact Test|puncture impact test]] can also include the mean values of the following measured variables:

* maximum load ''F''M,
* deformation at maximum load ''s''M,
* energy up to maximum load ''W''M.

==Tear test for films==

A tried-and-tested method for characterising the tear behaviour of films is the [[Tear Test|tear test]] to determine the tear resistance ''T''s under [[Quasi-static Test Methods|quasi-static test conditions]]. The testing machines to be used for this test are [[Material Testing Machine|universal testing machines]].

To determine the tear resistance, [[Trapezoidal Specimen|trapezoidal specimens]] can be used in accordance with DIN 53363 (see '''Fig. 3'''), which have a central incision from which the tear process is initiated by the notch stress. The length ''L'' of these trapezoidal test specimens on the long side is 120 mm, and the width ''W'' is 50 mm.

[[File:Film_Testing_Fig-3.jpg]]
{|
|- valign="top"
|width="50px"|'''Fig. 3''':
|width="600px" |Trapezoidal specimen for determining the tear resistance of polymeric films
|}

During the [[Stress|loading]] of the [[Specimen|test specimen]], the load–extension curve is recorded (see '''Figure 4''' below for an example). The tear resistance ''T''S is calculated using the following equation:

{|
|-
|width="20px"|
|width="500px" | <math> T_s = \frac {F_M} { B} </math>
|}

with
{|
|-
|''F''M
|width="15px" |
|maximum load or median load and
|-
|''B''
|
|specimen thickness
|}

[[File:wrv_folienpruefung.jpg|500px]]
{|
|- valign="top"
|width="50px"|'''Fig. 4''':
|width="600px" |Typical load–extension diagram for a polyamide ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: PA) film (a) and clamped [[Trapezoidal Specimen|trapezoidal specimen]] (b)
|}

Depending on the material behaviour, either the maximum load (as shown in the figure) or the median load from the load–time or load–extension diagram is used for ''F''M. However, the [[Material Value|material value]] determined using this test method only allows relative comparisons between different [[Material & Werkstoff|materials]]. In the case of [[Plastics|plastics]], it is particularly dependent on:

* the material quality and the treatment condition,
* the preferred direction resulting from the processing process for [[Thermoplastic Material|thermoplastics]],
* the duration of [[Vulcanization|vulcanisation]] for [[Elastomers|elastomers]], and
* the test temperature and the [[Deformation Velocity|deformation velocity]].

The determination of the tear resistance of elastomers is explained under [[Tear Test|tear test]].

==See also==

* [[Puncture Impact Test|Puncture impact test]]
* [[Instrumented Puncture Impact Test|Instrumented puncture impact test]]
* [[Instrumented Tensile Impact Test (ITIT)|Instrumented tensile impact test]]
* [[Hole Formation Films|Hole formation films]]
* [[Peel Test|Peel test]]
* [[Peel Properties of Peel Systems|Peel properties of peel systems]]
* [[Testing Plastic Packaging|Testing plastic packaging]]
* [[Tear Test|Tear test]]

Plastics film and sheeting - Determination of impact resistance by the free-falling dart method - Part 2: Instrumented puncture test

==References==

* [[Grellmann,_Wolfgang|Grellmann, W.]], [[Seidler,_Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see [[AMK-Library]] under A 22)

* [[Reincke,_Katrin|Reincke, K.]], [https://www.researchgate.net/profile/Wolfgang-Grellmann Grellmann, W.]: Verfahren zur Charakterisierung der mechanischen Eigenschaften von Folien und Elastomeren. Kautsch. Gummi Kunstst. 63 (2010) 203–208

* [[MPK-Procedure MPK-ITIT]] (2012-06): Testing of Plastics – Instrumented Tensile-Impact Test – Procedure for Determining the Crack Resistance Behaviour Using the Instrumented Tensile-Impact Test

* ISO 527-3 (2019-02): Plastics – Determination of Tensile Properties – Part 3: Test Conditions for Films and Sheets

* ISO 7765-2 (2025-05): Plastic Film and Sheeting – Determination of Impact Resistance by the Free-falling Dart Method – Part 2: Instrumented Puncture Test (Replacement for DIN 53373 (1970-09): Testing of Plastic Films – Impact Penetration Test with Electronic Data Recording (withdrawn))

* ISO 8256 (2023-11): Plastics – Determination of Tensile-impact Strength

* DIN 53363 (2003-10): Testing of Plastic Films – Tear Test Using Trapezoidal Test Specimen with Incision (withdrawn); replaced by DIN EN 17679 (2022-08)

* Reincke, K., [https://de.wikipedia.org/wiki/Wolfgang_Grellmann Grellmann, W.]: Verfahren zur Charakterisierung der mechanischen Eigenschaften von Folien und Elastomeren. In: Grellmann, W. (Eds.): Neue Entwicklungen in der Werkstoffprüfung – Herausforderung an die Kennwertermittlung. Tagung "Werkstoffprüfung 2011", December 1st and 2nd, 2011, Berlin, Proceedings pp. 185–192 (ISBN 978-3-9814516-1-0; see [[AMK-Library]] under A 13)

* Reincke, K., Grellmann, W.: Approaches to Characterise the Mechanical Properties of Films and Elastomers. In: Grellmann, W., Langer, B. (Eds.): Deformation and Fracture Behaviour of Polymer Materials. Springer Series im Materials Science 247, Springer Berlin Heidelberg (2017) 257–270 (ISBN 978-3-319-41877-3; e-Book: ISBN 978-3-319-41879-7; see [[AMK-Library]] under A 19)

* Nentwig, J.: Kunststoff-Folien – Herstellung, Eigenschaften, Anwendung. Carl Hanser, Munich Vienna (2006) 3rd Edition (ISBN 978-3-446-40390-1; see [[AMK-Library]] under G 7-1)

* Reincke, K.: Testing of Polymeric Films. In: Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser, Munich (2022); 3rd Edition, pp. 643-678 (ISBN 978-1-56990-806-8; e-Book ISBN 978-1-56990-807-5; ePub ISBN 978-1-56990-802-2; see [[AMK-Library]] under A 22)

[[Category:Film Testing]]
[[Category:Impact Tests]]

Film Testing - Revision history