ISO 8295 pdf download.Plastics – Film and sheeting – Determination of the coefficients of friction
1 Scope
1.1 This International Standard specifies a method for determining the coefficients of starting and sliding friction of plastic film and sheeting when sliding over itself or other substances. The method is intended to be used for non-sticky plastic film and sheeting (in the following text, referred to simply as “film”) of up to approximately 0,5 mm thickness. 1.2 This test method serves primarily for quality control. It does not give a comprehensive assessment of the machinability on packaging or processing ma- chines since other effects, e.g. electrostatic charges, air cushion, local rise of temperature and abrasion are, as a rule, involved. 1.3 The static frictional force increases as a rule, with the time the surfaces are in contact. Therefore, to get comparable results, this time span is specified. 1.4 Slip properties are sometimes generated by ad- ditives in the plastic material. The additives have varying degrees of compatibility with the film matrix. They may bloom or exude to the surface and change the slip properties, Since these effects are time- dependent, measurements on such films have to be related to the age of the film.
2 Normative reference
The follovwing standard contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most re- cent edition of the standard indicated below. Mem- bers of IEC and IS0 maintain registers of currently valid International Standards. IS0 291: 1977, Plastics – Standard atmospheres for conditioning and testing.
3 Definitions
For the purposes of this International Standard, the following definitions apply. 3.1 friction: The resistance that two surfaces lying in contact with each other build up against sliding. A distinction is made between static friction and dynamic friction. 3.1.1 static friction: Friction which has to be over- come as a “threshold value” at the onset of sliding motion. 3.1.2 dynamic friction: Friction which persists dur- ing a sliding motion at a given speed. 3.2 frictional force: The force necessary to over- come friction. A distinction is made between the static frictional force F, and the dynamic frictional force Fo. 3.3 normal force, Fp: The force acting perpendicular to the surfaces in contact.
5 Apparatus
5.1 The test device may be constructed in different ways. In general, it consists of a horizontal test table, a sled, and a driving mechanism to produce a relative motion between the sled and the test table, regard- less of which is the moving part. Figure 1 shows an example of apparatus in which the table is moved horizontally. The vertical motion of a tensile tester may also be utilized; in this case, the test table is fixed to the crosshead of the machine and the force is deflected to the horizontal direction by a pulley. The force is recorded by a chart recorder or an equiv- alent electrical data-processing unit. 5.2 The test device shall comply with the following conditions. 5.2.1 The surface of the test table shall be flat and smooth, and made of a non-ferromagnetic metal. 5.2.2 The normal force shall be generated by a sled with a square-shaped contact base of 40 cm* (edge length 63 mm). To ensure uniform pressure distri- bution, the base of the sled shall be covered with an elastic material, for example felt. The structure of this covering material shall be fine enough to avoid embossing thin films. The total mass of the sled shall be 200 g -t 2 g (exerting a normal force of I,96 N + 0,02 N).