(ISo 458/1 International Standard INTERNATIONAL ORGANIZATION FOR STANDARDIZATION-ME KAYHAPOAHAR OPTAHW3ALWA NO CTAHAPTM3ALMW-ORGANISATION INTE RNATIONALE DE NORMALISATION Plastics --- Determination of stiffness in torsion of flexible materials Part 1 : General method Plastiques - Determination de la rigidite en torsion des plastiques souples - Partie 1: Methode generale First edition - 1985-03-15 30 458/1-1985 (E) UDC 678.5/.8 : 620.175.251 Ref.No. ISO458/1-1985 (E) Descriptors : plastics, tests, torsion tests, determination, torsion angle, rigidity, test equipment. 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 for which 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 458/1 was prepared by Technical Committee ISO/TC 61, Plastics. International Standards ISO 458/1 and IS0 458/2 cancel and replace ISO Recommen- dationR458-1965,ofwhichtheyconstituteatechnicalrevision. @International Organization for Standardization, 1985 Printed in Switzerland INTERNATIONALSTANDARD ISO458/1-1985(E) Plastics - Determination of stiffness in torsion of flexible materials - Part 1 : General method Scope and field of application 1 Apparatus 4 This part of ISO 458 specifies a general method for determining 4.1 Testingmachine,capableofexertingatorquesufficient to deflect a test specimen with a span between 35 and 55 mm. the stiffness in torsion of flexible plastics at various A schematic diagram of a machine suitable for this test is temperatures, particularly at temperatures below oo c.1) shown in the figure. 2 References 4.2 Different weights, to vary the amount of torque depending on the stiffness of the specimen and its span. It is Iso 291, Plastics - Standard atmospheres for conditioning recommended that the actual amount of torque being applied and testing. byanygivencombinationofweights,torquepulleyandshaft bearings be determined by periodic calibration. ISO 458/2, Plastics - Determination of stiffness in torsion of NOTE -- For operation at low temperatures, it is recommended that flexible materials -- Part 2: Application to 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 or thermal chamber of suitable 3 Principle dimensions. An observation of torque and angle of deflection.is made after Thermometer, accurate to 1 'c and having the an arbitrarily fixed time of load application. This procedure is 4.4 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. 1 It is necessary that the duration of load application be arbitrarily fixed and thevalues of angles of deflectionbelimited becauseof the 4.6 Heat-transfer Fornormal medium. 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 Comparison between values of stffness in torsion may be made provided it has been shown that the liquid does not soften.or 2 otherwise affect the test specimen. With special prec