ASTM D648-18 PDF

Full title and description

Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position — ASTM D648-18. This test method (commonly referred to as a heat‑deflection or deflection‑under‑load test) defines procedures to determine the temperature at which a plastic specimen deforms a specified amount when subjected to a defined flexural (edgewise) load and controlled heating conditions, primarily for material control, development and comparison purposes.

Abstract

ASTM D648-18 specifies a laboratory procedure to measure the temperature at which an arbitrary deformation occurs for molded and sheet plastics subjected to a flexural load in the edgewise position. The method is intended for quality control, material development and specification purposes and is not intended to predict long‑term elevated temperature performance except where test conditions closely match the application.

General information

• Status: Active standard (current edition D648-18).
• Publication date: 2018 (published April 2018; listed as D648-18).
• Publisher: ASTM International.
• ICS / categories: Plastics in general — ICS 83.080.01 (Plastics).
• Edition / version: D648-18 (2018 edition); revises/supersedes D648-16.
• Number of pages: 14 pages.

Scope

This test method covers determination of the temperature at which an arbitrary deformation occurs when specimens are subjected to a defined set of testing conditions. It applies to molded and sheet materials of thickness 3 mm (1/8 in.) or greater that are rigid or semirigid at normal temperature (with provisions for composite specimens of thinner laminae). SI units are the standard reference in this method. The method is intended for control and development work and is not intended for design or long‑term performance prediction unless application and test conditions are similar.

Key topics and requirements

• Measurement of deflection temperature under a specified flexural (edgewise) load (heat‑deflection temperature / deflection‑under‑load concept).
• Applicability to molded and sheet plastics ≥ 3 mm thickness; procedures for preparing composite specimens when laminae are thinner.
• Controlled heating rate and loading conditions to determine the temperature at which specified deformation occurs (ensures repeatability and comparability).
• Test is intended for material control and development; results are not generally to be used as a universal predictor of long‑term elevated temperature performance.
• References and alignment considerations with related international methods (ISO 75 series) — results may differ between methods.

Typical use and users

Used by polymer and compound manufacturers, materials laboratories, OEMs, quality control and R&D teams to characterize and compare the elevated‑temperature stiffness/softening behavior of rigid and semirigid plastics, to support specification limits, material selection, and process development. Test data are commonly cited in material data sheets and product specifications.

Related standards

ISO 75‑1 and ISO 75‑2 (determination of temperature of deflection under load) cover similar subject matter but differ in technical content and test details; results are not directly interchangeable. ASTM classification and related material standards (for example references listed in ASTM D4000) and earlier ASTM D648 revisions (D648‑16, etc.) are directly related.

Keywords

heat deflection temperature; deflection temperature under load (DTUL); HDT; flexural load; edgewise position; plastics testing; material specification; elevated temperature deformation.

FAQ

Q: What is this standard?

A: ASTM D648-18 is the 2018 edition of the Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position, which defines a laboratory procedure to determine the temperature at which plastics deform under a specified flexural load.

Q: What does it cover?

A: It covers specimen types (molded and sheet plastics ≥ 3 mm unless composite specimens are used), test setup (edgewise flexural loading and controlled heating), and procedures to determine the temperature at which a defined deformation occurs. It also clarifies intended uses and limitations (control and development, not a general predictor of long‑term behavior).

Q: Who typically uses it?

A: Polymer manufacturers, independent testing laboratories, OEMs, design and materials engineers, and quality/production groups that need comparative elevated‑temperature stiffness data for plastics.

Q: Is it current or superseded?

A: D648‑18 is the current ASTM edition published in 2018 and it supersedes D648‑16. ASTM lists D648‑18 as active; a review/revision work item (WK92848) was recorded in 2024 to consider updates, so future revisions may appear pending that work.

Q: Is it part of a series?

A: It is part of ASTM Committee D20 (Plastics) test methods and aligns in subject matter with the ISO 75 series (ISO 75‑1, ISO 75‑2) and related ASTM material classifications; however, technical details differ across the standards.

Q: What are the key keywords?

A: Heat deflection temperature (HDT), deflection temperature under load (DTUL), flexural load, edgewise position, plastics testing, elevated‑temperature stiffness.