BS EN ISO 178:2019

What is ISO 178 — Flexural properties of plastics about? 

ISO 178 is an international standard that covers specifications for good quality plastics.  

ISO 178 specifies a method for determining the flexural properties of rigid and semi-rigid plastics under defined conditions. A preferred test specimen is defined, but parameters are included for alternative specimen sizes for use where appropriate. A range of test speeds is included. 

ISO 178 includes the method that is suitable for use with the following range of materials: 

• Thermoplastic moulding, extrusion and casting materials, including filled and reinforced compounds in addition to unfilled types, rigid thermoplastics sheets 
• Thermosetting moulding materials, including filled and reinforced compounds; thermosetting sheets following methods 

Note 1: The method given in ISO 178 is not normally suitable for use with rigid cellular materials or sandwich structures containing cellular material.  

Note 2: The method is not suitable for the determination of design parameters but can be used in materials testing and as a quality control test. 

Who is ISO 178 — Flexural properties of plastics for? 

ISO 178 on Flexural properties of plastics is useful for: 

• Plastics industries 
• Plastics product manufacturers 
• Industries where plastic is used  
• Test laboratories for Plastics 

Why should you use ISO 178 — Flexural properties of plastics? 

The flexural properties such as flexural strength, modulus, stress, etc. of plastic can be termed as the ability of the plastics to resist bending or deformation when the load is applied.  

ISO 178 specifies the technicalities for the test method used for investigating the flexural behavior of the plastics and to determine the flexural strength, flexural modulus, and other aspects of the flexural stress/strain relationship under the conditions defined, which helps the users to estimate the capacity and quality of the plastics. 

ISO 178 gives you elaborated information about the apparatus used to perform the test, explains the principle of the test method, as well as helps the users with a sampling of the test specimen, calculation, and expression results to conclude the final test report.  

Overall, ISO 178 helps the users to assess the flexural properties of the plastics, in order to manufacture good quality, reliable and durable plastics as well as to reduce any risks caused due to bending or deformation of the plastic and its products. 

What’s changed since the last update? 

BS EN ISO 178:2019 supersedes BS EN ISO 178:2010+A1:2013, which is withdrawn. The main changes compared with the previous edition are as follows: 

• Differentiating calibration requirements according to the type of test 
• The introduction of a deflectometer 
• The reinstatement of procedures for compliance correction 
• The addition of a new Annex D showing the relation between tensile and flexural modulus