Information on the most widely used ASTM standards within the materials testing industry
ASTM D3364: Standard Test Method for Flow Rates for Poly(Vinyl Chloride) with Molecular Structural Implications
ASTM D3364 test method is an extension of Test Method ASTM D1238 specific to the measurement of flow rates of poly(vinyl chloride) (PVC) compounds while detecting and controlling various polymer instabilities associated with the flow rate. it is useful for quality-control tests on PVC compounds having a wide range of melt viscosities. Measurements are made at shear rates close to 1 s−1. Unlike general-purpose thermoplastics, PVC often exhibits complex flow behavior due to its sensitivity to temperature, shear, and thermal degradation, making this tailored test essential for quality control and processing optimization.
Test Principle of ASTM D3364:
The test leverages rheological principles to link flow behavior to PVC molecular structure, with three core tenets:
Flow-Viscosity Relationship: Flow rate is the reciprocal of viscosity, defined as volumetric displacement through a controlled orifice (expressed as shear rate/shear stress). For PVC (obeying the power law), this is formalized as:

where N (power law exponent) ranges from 0.1 to 0.33 for PVC. Flow is far more sensitive to molecular changes than viscosity.
Instability Detection: Identifies three types of polymer instability driving flow changes:
Thermal instability: Degradation from temperature effects.
Shear instability: Bond breaking under mechanical stress.
Rheological instability: Non-uniform distribution of viscosity/molecular weight elements.
Molecular Structure Implications: By tracking flow rate variations, the test predicts changes in PVC molecular weight, plasticizer content, and stability.
This testing method is widely used for quality control testing of PVC compounds with a wide range of melt viscosity. It is specifically designed to measure the melt flow rate (MFR or MFI) of polyvinyl chloride compounds, while detecting and controlling various polymer instabilities related to flow rate. The sensitivity of this testing method makes it useful as an aid in correlating with processing conditions and predicting processing changes. This test is capable of detecting and tracking profound changes that occur during extrusion, injection molding, milling, or mixing processes due to three types of measured polymer instability, including thermal instability caused by temperature effects, shear instability caused by polymer chain breakage, and rheological instability caused by uneven distribution of viscosity or molecular weight elements.Test a PVC sample at 175 ° C.
Due to the corrosiveness of PVC material, the melt flow index tester need equip with a special corrosion-resistant kit to prevent any interaction between the material and metal during testing.
Test Methods:
ASTM D3364-26 employs a single primary procedure (with optional automation) tailored to non-rigid PVC, building on ASTM D1238 but with modified conditions and enhanced instability detection. Core features include:
Standard Conditions: Fixed test temperature of 190°C and total piston load of 14,900 g (14.9 kg) .
Flow Rate Definition: Quantified as the mass of polymer extruded through a specialized die in grams per 10 minutes (g/10 min).
Cutting Protocol: Specimens are cut at intervals dictated by flow rate, ranging from 4 minutes (15–30 mg/min) to 10 seconds (1000–2000 mg/min). Newer models support automatic specimen cutting tools to reduce human error.
Averaging: Results are averaged from the five most stable consecutive specimens near the end of the test.
Under standard configuration, measurements are taken at a temperature of 190 ° C and a load of 14.9kg.
For rigid PVC, using a larger test load of approximately 50kg may be more advantageous. Semi hard or soft PVC is measured at 150 ° C/50kg.
The mold is 25.43mm (1 inch) long, with a diameter of 2.095mm compared to the standard mold, and has a conical feeding port.
Compared to standard molds, this mold reduces MVR by approximately 10 times. The filling volume is 2.15 grams and must be strictly followed.
The MFR value is calculated in milligrams per minute, and the instability of the molten material is expressed as a percentage.
Through the testing method of ASTM D3364, it is possible to detect polymer bond breakage caused by temperature effects, shear, or instability caused by rheological effects (such as uneven distribution of viscosity or molecular weight).
Test Device of the ASTM D3364 PVC material melt flow index test:
The apparatus is a modified ASTM D1238 extrusion plastometer (melt flow index tester) with key components optimized for PVC:
| Plastometer | Identical to ASTM D1238 but with a custom die |
| Die | ~3x longer than D1238’s standard die (regular dimensions in Fig. 1) to control rheological instability. High-flow applications use dies ≥2 inches (improving length-to-diameter ratio, L/D)
Fig. 1 |
| Thermoregulator | Maintains 190±0.1°C (critical for sensitivity: 1°C change alters flow by ~19%). Newer models use touchscreen controls (±0.1°C accuracy). |
| Thermometer | Resting on the die orifice top, matching D1238’s 1/2-inch offset |
Test Specimen:
Material: Non-rigid PVC compounds (e.g., flexible films, coatings, cable insulation).
Form: Powder, granules, or pellets (no specific grinding required, unlike D1238).
Mass: 7.00±0.05 g (precise charging to minimize pressure loss).
Preparation: Avoid thermal degradation; charge directly into the preheated cylinder (190°C) and pack with a phenolic tool.
Related products and device
Related Standard
ASTM D1238 Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer
ASTM D1238 test method test method covers the determination of the rate of extrusion of molten thermoplastic resins using an extrusion plastometer. it is particularly useful for quality control tests on thermoplastics. The data produced by ASTM D1238 test serves to indicate the uniformity of the flow rate of the polymer as made by an individual process. It is not to be used as an indication of uniformity of other properties without valid correlation with data from other tests.
ISO 1133: Plastics -- Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics.
ISO 1133 standard specifies two procedures for the determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastic materials under specified conditions of temperature and load. One is a mass-measurement method. The other is a displacement-measurement method. Normally, the test conditions for measurement of melt flow rate are specified in the material standard with a reference to ISO 1133. The test conditions normally used for thermoplastics are listed in annexes.
FAQs About ASTM D3364 (PVC Melt Flow & Instability Test)
Q1. What is ASTM D3364 primarily designed to test?
A: ASTM D3364 measures the melt flow rate (MFR) of PVC compounds and specifically detects flow instability during extrusion. Unlike general melt flow tests, it focuses on how consistent PVC flows and whether it degrades thermally or rheologically under test conditions.
Q2. How is ASTM D3364 different from ASTM D1238?
A: ASTM D1238 is a general method for most thermoplastics, only measuring average MFR/MVR.
ASTM D3364 is PVC-specific; it uses frequent sampling to track flow changes over time and calculates an instability index to detect degradation, shear variation, or inconsistent melting in PVC.
Focus: Non-rigid PVC (D1238 covers general thermoplastics).
Die: ~3x longer than D1238’s standard die (controls rheological instability).
Conditions: Fixed 190°C/14.9 kg (D1238 uses variable conditions).
Sensitivity: Enhanced to molecular structural changes (thermal/shear/rheological instability).
Specimen Mass: 7.00±0.05 g (D1238 varies by melt flow rate).
Q3. Why is the ASTM D3364 test important?
A: The test is critical for quality control in PVC manufacturing and serves three key purposes:
It correlates flow behavior with real-world processing conditions (extrusion, injection molding, milling).
It detects profound changes in PVC composition (e.g., plasticizer content, molecular weight, thermal/rheological stability).
It predicts material stability during processing, helping manufacturers optimize formulations and avoid failures.
The test’s sensitivity makes it invaluable for ensuring consistent performance in non-rigid PVC products (e.g., flexible films, cables, coatings).
Q4. Can ASTM D3364 be used for plastics other than PVC?
A: No. It is exclusively intended for poly(vinyl chloride) compounds. Other thermoplastics use ASTM D1238, as their flow and thermal behaviors are very different from PVC.
Q5. What does a falling flow rate indicate?
A: Decreasing flow often suggests cross-linking, excessive filler agglomeration, or partial thermal decomposition that restricts flow, which can cause defects in actual processing.
Q6. Does a good MFR value guarantee good PVC processability?
A: Not entirely. Even with a normal average MFR, high flow instability (from D3364) means the PVC will perform poorly in real production, leading to inconsistent product quality.
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