ASTM D1238-23a PDF

Full title and description

ASTM D1238-23a — Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer. This test method specifies procedures for measuring the rate of extrusion (melt mass flow rate, MFR, and melt volume flow rate, MVR) of thermoplastic resins using an extrusion plastometer under prescribed temperature and load conditions.

Abstract

This standard describes instrument setup, specimen preparation, and four measurement procedures (A, B, C, and D) for determining melt flow/melt volume flow of thermoplastic materials. Results are reported as mass flow (g/10 min) or volume flow (cm3/10 min) depending on the procedure. The method includes precision and bias information, recommended reporting practices, and guidance for multi-load (flow rate ratio) testing used to assess molecular-structure-related processing behaviour.

General information

• Status: Published / Active
• Publication date: 15 November 2023
• Publisher: ASTM International (ASTM)
• ICS / categories: 83.080.20 — Thermoplastic materials
• Edition / version: D1238-23a (current revision)
• Number of pages: 19

Scope

The standard covers the determination of extrusion rates of molten thermoplastic resins using an extrusion plastometer. It applies to a wide range of thermoplastics and defines the controlled heating, preconditioning, die geometry, piston/load conditions and timing procedures necessary to obtain reproducible melt flow (MFR) or melt volume flow (MVR) values. The method is intended for quality control, specifications, and material comparison and does not address all safety concerns associated with test operation.

Key topics and requirements

• Apparatus requirements: extrusion plastometer, specified barrel and die dimensions, piston, temperature controllers and measurement timing systems.
• Test procedures: Procedure A (manual mass-based MFR), Procedure B (automatically timed mass MFR and MVR), Procedure C (automatic measurement for high flow rates), and Procedure D (multi-load/Flow Rate Ratio, FRR).
• Units and reporting: mass flow in grams per 10 minutes (g/10 min) and volume flow in cm3/10 min; procedure used must be reported.
• Specimen conditioning and charge preparation: prescribed preheat times and handling to ensure repeatability.
• Precision and bias: interlaboratory precision tables and repeatability/interlaboratory reproducibility guidance for common thermoplastics.
• Calculation methods: formulas for converting extrudate mass and volume to standard flow rates and for FRR calculations.
• Comparison and correlation: notes on relationship to ISO 1133 and recommendations where procedures differ.
• Health & safety: advisories on hot equipment, fumes, and safe operation—users must adopt appropriate safety practices.

Typical use and users

Used widely by plastics processors, polymer producers, quality control and R&D laboratories, recyclers, material specification writers, and test laboratories to characterize polymer flow behavior for processing selection (injection molding, extrusion), batch acceptance, and material comparisons.

Related standards

Commonly referenced and related documents include ISO 1133 (Determination of Melt-Mass Flow Rate and Melt Volume-Flow Rate of Thermoplastics), ASTM D4000 (classification system for plastics), ASTM D5947 (physical dimensions of plastics specimens), and other ASTM test methods and classification standards for thermoplastics and related materials.

Keywords

melt flow rate, melt mass flow rate (MFR), melt volume flow rate (MVR), melt flow index (MFI), extrusion plastometer, flow rate ratio (FRR), thermoplastics, melt flow testing, ASTM D1238-23a

FAQ

Q: What is this standard?

A: ASTM D1238-23a is the ASTM test method that defines how to measure melt flow and melt volume flow of thermoplastic resins using an extrusion plastometer.

Q: What does it cover?

A: It covers apparatus, specimen preparation, four measurement procedures (A–D), calculation and reporting of MFR and MVR, precision information, and guidance for multi-load testing (FRR). It also notes equivalence and differences with ISO 1133.

Q: Who typically uses it?

A: Polymer manufacturers, processors, QC and R&D labs, recyclers, standards writers, and independent testing laboratories use this standard for material specification, batch acceptance and process selection.

Q: Is it current or superseded?

A: It is the current published revision (designation D1238-23a), approved and published in November 2023; it supersedes the prior D1238-23 edition.

Q: Is it part of a series?

A: Yes — D1238 is a long-standing ASTM series of test methods for melt flow measurement; it is commonly used alongside related ASTM and ISO standards for plastics testing and classification.

Q: What are the key keywords?

A: melt flow rate, MFR, MVR, melt flow index, extrusion plastometer, thermoplastics, flow rate ratio, ASTM