BS EN ISO 75‑1:2020 pdf download.Plastics – Determination of temperature
of deflection under load Part 1: General test method.
1 Scope
1.1 This document gives a general test method for the determination of the temperature of deflection under load (flexural stress under three-point loading) of plastics. Different types of test specimen and different constant loads are defined to suit different types of material.
1.2 ISO 75‑2 gives specific requirements for plastics (including filled plastics and fibre-reinforced plastics in which the fibre length, prior to processing, is up to 7,5 mm) and ebonite, while ISO 75‑3 gives specific requirements for high-strength thermosetting laminates and long-fibre-reinforced plastics in which the fibre length, prior to processing, is greater than 7,5 mm.
1.3 The methods specified are suitable for assessing the relative behaviour of different types of material at elevated temperature under load at a specified rate of temperature increase. The results obtained do not necessarily represent maximum applicable temperatures because, in practice, essential factors, such as time, loading conditions and nominal surface stress, can differ from the test conditions. True comparability of data can only be achieved for materials having the same room‑temperature flexural modulus.
1.4 The methods specify preferred dimensions for the test specimens.
1.5 Data obtained using the test methods described are not intended to be used to predict actual end‑use performance. The data are not intended for design analysis or prediction of the endurance of materials at elevated temperatures.
1.6 This method is commonly known as the heat deflection temperature or heat distortion temperature (HDT) test, although there is no official document using this designation.
6.3 Specimen inspection Specimens shall be free of twist and shall have mutually perpendicular adjacent surfaces. All surfaces and edges shall be free from scratches, pits, sink marks and flash. NOTE Injection moulded test specimens usually have draft angles of between 1° to 2° to facilitate demoulding. Therefore, side faces in moulded test specimens will generally not be parallel. Injection moulded test specimens are never absolutely free of sink marks. Due to differences in the cooling history, generally, the thickness in the centre of the specimen is smaller than at the edge. Ensure that all cut surfaces are as smooth as possible, and that any unavoidable machining marks are in the lengthwise direction. The specimens shall be checked for conformity with these requirements by visual observation against straight edges, squares and flat plates, and by measuring with micrometer calipers. Specimens showing measurable or observable departure from one or more of these requirements shall be rejected or machined to proper size and shape before testing.BS EN ISO 75‑1 pdf download.