BS 771:1992 download

06-10-2021 comment

BS 771:1992 download.Specification for Phenolic moulding materials.
1 Scope
1.1 General
BS 771 specifies requirements for the physical and chemical properties of phenolic moulding materials, classified by type and grade according to their use and properties.
1.2 Types
Four types of phenolic moulding material are specified, as follows:
— Type A: General purpose
— Type C: Heat resistant
— Type D: Impact resistant
— Type E: Electrical applications 1.3 Filler
The type of filler to be used in each type of phenolic moulding material is not specified but is usually as shown in the following examples:
Type of moulding Filler
Wood flour
Mineral filler
1.4 Resin
Abbreviations are used to indicate the type of phenolic resin, as follows:
— One-step phenolic resin: PF 1
— Two-step phenolic resin: PF 2 1.5 Grades
The various types of material are further sub-divided into grades based on the property levels and requirements.
PF 2A1 is a phenolic moulding material made from two-step resin, intended for general applications. The last digit indicates a particular grade of one type of material.
1.6 Classification
Table 1 shows the types and the grades of phenolic moulding material covered by BS 771, together with their applications and distinguishing properties.
3 Definitions
For the purposes of this International Standard, the following definitions apply.
phenolic moulding material thermosetting material based on a phenolic resin and used in the manufacture of thermoset-moulded articles. Other ingredients such as fillers. plasticizers, catalysts and colorants may be incorporated
phenolic resin
generic term for a class of resins made by the polycondensation of phenol, and/or its homologues and/or derivatives of phenol or its homologues, with aldehydes or ketones. These thermosetting resins can be either novolaks (two-step PF 2) or resols (one-step PF 1)
NOTE 1 Novolak resins require a crosslinking agent, generally hexamethylenetetramine.
4 Requirements
Phenolic moulding materials complying with this specification shall meet the appropriate property requirements shown in Table 2.
Though no specific limits are placed on the flow rate in Table 2, a suitable flow rate is essential for the satisfactory use of a phenolic moulding material and the flow rate shall therefore be specified in any contract.
The method of test and the flow rate value shall be as agreed by the interested parties.
In addition, for some applications, it may be desirable for information to he made available on other properties of the moulding material, for example curing time, particle size or moisture content. If this is so, these properties and the method to be used shall be agreed by the interested parties.
5 Test specimens
Bulk factor, moisture content, flow and particle size shall be measured on the moulding material itself. Other properties shall be determined on moulded test specimens prepared in accordance with ISO 295. It is permissible to machine test specimens from sheet (see ISO 2818) moulded under the moulding conditions of ISO 295, as long as it can be shown that the test specimens give results which do not differ significantly from those with moulded test specimens.
Test specimens to be used for determining the properties given in section B of Table 2 shall be conditioned under prevailing atmospheric conditions as indicated in ISO 291, unless otherwise stated in the method of the test or agreed by the interested parties.
Tests shall comence not less than 16 h and not more than 72 h after the test specimens have been moulded, unless otherwise specified in the methods. When test specimens have been moulded from powder which has been preheated or dried, then this fact shall be stated in the test report. The preheating or drying conditions shall also be given.
6 Methods of test
6.1 Determination of specific gravity See ISO 1183, method A. Test specimens may be prepared from any moulded plate or bar. At least two test specimens shall be used for the determination.
6.2 Determination of flexural stress at rupture See ISO 178. Five test specimens of length not less than 80 mm, of width 10 mm and of thickness 4 mm shall be used.
For both moulded bars and test specimens machined from material moulded in the form of a plate, the load shall be applied parallel to the direction of moulding pressure. The testing speed shall be 2,0 mm/mm ± 0,2 mm/mm.
6.3 Determination of Charpy impact strength See ISO 179. For both moulded bars and test specimens machined from material moulded in the form of a plate, the load shall be applied parallel to the direction of moulding pressure.
6.3.1 Charpy notched impact strength See ISO 179, method 3C. Five test specimens shall be used for the determination.
6.3.2 Charpy unnotched impact strength See ISO 179, method 3D. Five test specimens shall be used for the determination.
6.4 Determination of Izod impact strength See ISO 180, method 2A. Five test specimens shall be used for the determination.
6.5 Determination of temperature of deflection under load
See ISO 75, method A. Two t.est specimens of length not less than 110 mm, of width 10 mm and of thickness 4 mm shall be used.
6.6 Determination of flammability characteristics
Use three test specimens, each measuring 120 mm X 10 mm x 4 mm, for the determination. The test shall be carried out in accordance with ISO 181, except for the following details: alter 3 mm, remove the incandescent rod from the specimen and note whether there is any flame on the specimen during the next 30 s.
6.7 Determination of insulation resistance See IEC 167. The test specimen shall be in the form of a flat plate moulded to a thickness
of 3,0 mm ± 0,25 mm. Taper pin electrodes shall be used. Before carrying out the test, the test specimens shall be conditioned (without electrodes) in an oven at 50 °C ± 2 °C for 24 h * 1 h, and then cooled to room temperature in a desiccator. It shall then be immersed in distilled or deionized water maintained at 23 °C ± 2 °C for 24 h ± 1 h. Before the specimen is tested, water on its surface shall be removed with blotting paper or filter paper or with a clean absorbent cloth, and the electrodes then fitted. Measurement of insulation resistance shall be made within 5 mm of the end of the immersion. At least two test specimens shall be used for the determination.
6.8 Determination of electric strength at power frequencies
See IEC 243-1. At least three test specimens shall be used for the determination.
It may be necessary to measure the short-time value on an additional test specimen in order to determine the initial voltage to be applied.
Each specimen shall be 3,0 mm ± 0,25 mm thick and not less than 100 mm in diameter. Each test specimen shall he immersed in oil at a temperature of 90°C ± 2 °C for 15 mm to 20 mm before the test, and also during the test. The oil should preferably be one complying with the requirements of class II as defined in IEC 296. The 20 s step-by-step method shall be used.
6.9 Determination of dielectric dissipation factor
See IEC 250. The test frequency shall be 1 MHz. Three test specimens shall he used for the determination.
6.10 Determination of comparative tracking index (CTI) under moist conditions
See IEC 112. Test solution A shall be used. For quality-control purposes, the proof test may be used. The numerical value of the applied voltage shall be that of the CT! given in Table 2. Two determinations shall be made.
6.11 Determination of free ammonia and ammonium compounds
See ISO 120. The powdered test portion may be prepared from any moulded plate or bar.
6.12 Determination of water absorption See ISO 62, method 1. Two test specimens measuring 50 mm ± 1 mm in diameter and 3,0 mm ± 0,25 mm thick shall be used.
As an alternative, when agreed by the interested parties, square specimens of side 50 mm ± 1 mm cut from 4,0 mm ± 0,2 mm thick moulded plates may be used. If this alternative type of test specimen is used, the requirements shall also be the subject of agreement by the interested parties.

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