This part of GB/T 1634 specifies three methods, using different values of constant flexural stress, which can be used for the determination of the temperature of deflection under load of plastics (including filled plastics and fiber-reinforced plastics in which the fiber length, prior to processing, is up to 7.5 mm) and ebonite.
—— method A, using a flexural stress of 1.80 MPa;
—— method B, using a flexural stress of 0.45 MPa;
—— method C, using a flexural stress of 8.00 MPa.
The standard deflection, Δs, used to determine the temperature of deflection under load corresponds to a flexural-strain increase, Δεf, defined in this part. The initial flexural strain due to the loading of the specimen at room temperature is neither specified nor measured in this part. The ratio of this flexural-strain increase to the initial flexural strain depends on the modulus of elasticity, at room temperature, of the material under test. This method is, therefore, only suitable for comparing the temperatures of deflection of materials with similar room-temperature elastic properties.
Note 1: The methods give better reproducibility with amorphous plastics than with semi-crystalline ones. With some materials, it can be necessary to anneal the test specimens to obtain reliable results. Annealing procedures, if used, generally result in an increase in the temperature of deflection under load (see 6.6).
Note 2: For additional information, see GB/T 1634.1-2019, clause 1.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 1634.1-2019 Plastics - Determination of temperature of deflection under load - Part 1: General test method (ISO 75-1: 2013, MOD)
GB/T 9352-2008 Plastics - Compression moulding of test specimens of thermoplastic materials (ISO 293: 2004, IDT)
GB/T 17037.1-1997 Plastics - Injection moulding of test specimens of thermoplastic materials - Part 1: General principles and moulding of multipurpose and bar test specimens (ISO 294-1: 1996, IDT)
GB/T 37426-2019 Plastics - Test specimens (ISO 20753: 2008, MOD)
ISO 2818: 1994 Plastics - Preparation of test specimens by machining
ISO 10724-1: 1998 Plastics - Injection moulding of test specimens of thermosetting powder moulding compounds (PMCs) - Part 1: General principles and moulding of multipurpose test specimens.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 1634.1-2019 apply.
GB/T 1634.2-2019 The following standards are cited：
GB/T 1634.2-2019 Cited by the following standards：
