introduction
ISO (International Organization for Standardization) is a global alliance of national standards bodies (ISO member bodies). The development of international standards is usually carried out through ISO technical committees. Each member institution interested in a subject on which a technical committee has been established has the right to be represented on that committee. International governmental and non-governmental organizations liaising with ISO are also involved in this work. ISO works closely with the International Electrotechnical Commission (IEC) on all matters of electrical standardization.
The draft international standard adopted by the Technical Committee will be circulated to the member bodies for voting. Publication as an international standard requires approval by at least 75% of member institutions.
The international standard ISO 8295 was developed by the Technical Committee ISO/TC 61, Plastics, Subcommittee SC 11, Products.
The second edition cancels and replaces the first edition (ISO 8295:1986), which has been technically revised.
Annex A to this standard is for reference only.
ISO 8295-1995 “Determination of friction coefficient of plastic film and sheet”
1 Range
1.1 This standard specifies methods for determining the starting and sliding friction coefficients of plastic films and sheets when sliding on themselves or other substances. The method is intended for use with non-adhesive plastic films and sheets up to a thickness of approximately 0.5 mm (hereinafter referred to as “films”).
1.2 This test method is mainly used for quality control. It does not provide a comprehensive assessment of the machinability of packaging or processing machines, as other effects are often involved, such as electrostatic charges, air cushions, local temperature increases and wear.
1.3 Static friction forces usually increase with the time of surface contact. Therefore, this time span is specified in order to obtain comparable results.
1.4 Slippery properties are sometimes produced by additives in plastic materials. The additive has different degree of compatibility with the film matrix. They may bloom or seep to the surface and change slip characteristics. Since these effects are time-dependent, the measurement of such films needs to be related to the age of the film.
ISO 8295-1995 “Determination of friction coefficient of plastic film and sheet”
2 Normative Reference
The following standards contain provisions that, by reference herein, constitute the provisions of this International Standard. At the time of publication, the version shown is valid. All standards are subject to revision and parties to an agreement based on this international Standard are encouraged to investigate the possibility of applying the following new versions of the standard. IEC and ISO members maintain a register of currently valid international standards.
ISO 291:1977, Plastics – Standard atmospheres for regulation and testing.
3 Definition
For the purposes of this standard, the following definitions apply.
3.1 Friction
Two surfaces in contact with each other will accumulate resistance to sliding. There is a difference between static friction and dynamic friction.
ISO 8295-1995 “Determination of friction coefficient of plastic film and sheet”
3.1.1 Static friction
Friction that needs to be overcome as a “threshold” at the beginning of sliding motion.
3.1.2 Dynamic friction
Friction that persists during sliding motion at a given speed.
3.2 Friction Force
The force needed to overcome friction. There is a difference between static friction force F S and dynamic friction force FD.
3.3 Normal force Fp
Force perpendicular to the contact surface.
ISO 8295-1995 “Determination of friction coefficient of plastic film and sheet”
3.4 Friction coefficient
The ratio of the friction force to the normal force perpendicular to the two surfaces in contact.
3.4.1 Static friction coefficient mml_m1
3.4.2 Dynamic friction coefficient mml_m2
Note 1: The friction coefficient of the film is usually between 0,2 and 1.
Note 2: * In this case, the coefficient of friction is a property independent of the test equipment and test conditions. Since thin films generally perform poorly, all test parameters are specified in this international standard.
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