458/1 (ISO International Standard INTERNATIONAL ORGANIZATION FOR STANDARDIZATION+MEKAYHAPOAHAR OPTAHM3ALMR NO CTAHAAPTM3ALMM+ORGANISATION INTE RNATIONALE DE NORMALISATION Plastics -- Determination of stiffness in torsion of flexible materials -- Part 1 : General method Firstedition-1985-03-15 50458/1-1985 (E) UDC 678.5/.8:620.175.251 Ref.No.ISO 458/1-1985(E) Descriptors : plastics, tests, torsion tests, determination, torsion angle, rigidity, test equipment. Price based on 4 pages Foreword Iso (the International Organization for Standardization) is a worldwide federation of national standards bodies (isO member bodies).The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject forwhich a technical committee has been established has the right to be represented on that committee. International organizations,govern- mental and non-governmental, in liaison with iso, also take part in the work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISo Council. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 458/1wasprepared byTechnical Committee ISO/TC 61, Plastics. International StandardsISO458/1andISO458/2cancelandreplaceISORecommen- dation R 458-1965, of which they constitute a technical revision. International OrganizationforStandardization,1985 Printed in Switzerland INTERNATIONALSTANDARD ISO458/1-1985(E) Plastics s - Determination of stiffness in torsion of flexible materials Part 1 : General method Scope andfieldof application 4 Apparatus This part of ISo 458 specifies a general method for determining 4.1 Testing machine, capable of exerting a torque sufficient to deflect a test specimen with a span between 35 and 55 mm. the stiffness in torsion of flexible plastics various temperatures, particularly at temperatures below oo c,1) A schematic diagram of a machine suitable for this test is shown in the figure. References 4.2 Different weights,to vary the amount of torque depending on the stiffness of the specimen and its span. It is Iso291,Plastics-Standardatmospheresfor conditioning recommended that the actual amount of torque being applied and testing. by any given combination of weights, torque pulley and shaft bearings be determined by periodic calibration. Iso458/2,Plastics-Determinationofstiffnessintorsionof NOTE -- For oporation at low temperatures, it is recommended that flexiblematerials -Part2:Applicationto plasticized com- the shaft of the machine be provided with a heated collar next to the pounds of homopolymers and copolymers of vinyl chloride. lower bearing to prevent the formation of ice. 4.3 Dewar flask Principle orthermal chamber of suitable dimensions. An observation of torque and angle of deflection.is made after an arbitrarily fixed time of load application. This procedure is 4.4 Thermometer,accurate to1° and havingthe employed at single temperatures or at selected temperature necessary range. The bulb should be placed in close proximity intervals over a range specified for the material to be tested. to the test specimen. NOTES 4.5 Timer, accurate to 0,1 s. It is necessary that the duration of load application be arbitrarily fixed and the values of angles of deflection be limited because of thc 4.6 Heat-transfer medium. Fornormal laboratory known non-linear characteristics of plastics and their tendency to purposes, a substance which is liquid over the desired creep. temperature range is used for the heat-transfer medium, provided it has been shown that the liquid does not soften,or 2 Comparison between values of stiffness in torsion may be made only when the values have been obtained using test specimens of the otherwise affect the test specimen. With special precautions, a same thickness and at the same span and