ISO 6691:2021 pdf download – Thermoplastic polymers for plain bearings — Classification and designation.
4.4 Data block 3 4.4.1 General The levels of distinctive properties are coded by letters and numbers. The properties used for the designation are different for every thermoplastic polymer. Owing to manufacturing tolerances, single property values can lie on, or to either side of, two intervals. lt is up to the manufacturer to state which interval will designate the thermoplastic polymer. 4.4.2  Polyamides Polyamides are designated in data block 3 by their viscosity number, represented by two digits (see Table 5) in accordance with ISO 16396-1 and, separated by a dash, their modulus of elasticity represented by three digits (see Table 6). In the last position, rapid-setting products may be indicated with the letter N. The viscosity number shall be determined in accordance with ISO 307 using the solvents given in Table 5. The modulus of elasticity shall be determined in the dry state in accordance with ISO 527-1, ISO 527-2, ISO 527-3, ISO 527-4 and ISO 527-5, under the conditions specified in ISO 16396-2.
4.4.3 Polyethylenes Polyethylenes are designated by their density represented by two digits (see Table 7) in accordance with ISO 17855-1 and, separated by a dash, their melt flow rate (MFR) represented by one letter and three digits (see Table 8). The density of the base material shall be determined in accordance with ISO 1183-1, ISO 1183-2 and ISO 1183-3 under the conditions specified in ISO 17855-2. The melt mass-flow rate shall be determined in accordance with ISO 1133-1 at 190 °C with a load of 2,16 kg (symbol D). For thermoplastic polymers with a melt mass-flow rate <0,1 g/10 min, a test under a load of 5 kg (symbol T) is recommended. If the melt mass-flow rate is still <0,1 g/10 min, the test should then be carried out under a load of 21,6 kg (symbol G). The symbols D, T and G shall precede the code for melt flow rate given in Table 8.
4.4.5 Other polymers The coding for the distinctive properties of polyoxymethylene, polytetrafluoroethylene, poly(amide- imide), polyimide, Polyetheretherketone, Polyvinylidene fluoride and Polyphenylene sulfide will be included in a future edition of this document. 4.5 Data block 4 The fillers and reinforcing materials, as well as additives specific for the application in plain bearings, are coded as follows: — position 1: types of fillers and/or reinforcing materials, coded by a letter (see Table 10); — position 2: physical forms of fillers and/or reinforcing materials, coded by a letter (see Table 11); — positions 3: mass content of fillers and/or reinforcing materials, coded by two digits (see Table 12); — positions 4: Types of lubricants, coded by two letters (see Table 13).