I. Overview

The Melt Flow Index Tester (MFI) is a crucial testing instrument used to measure the melt mass-flow rate (MFR) or melt volume-flow rate (MVR) of polymer plastics under specified conditions of temperature and load. Accurate and standardized Melt Flow Index Tester Operating Procedures are essential prerequisites for ensuring the reliability and repeatability of test results. They also constitute a vital component of laboratory quality management systems.

II. Scope of Application

This operating procedure applies to the melt flow index testing of plastics, rubber, and other polymer materials, including but not limited to:

Polyethylene (PE)、Polypropylene (PP)、Polystyrene (PS)、Polyurethane (PU)、Plastic modified materials and copolymer samples

III. Equipment Description

Heating Barrel and Insulation System

Precise temperature control range typically from room temperature to 400 °C.

Temperature fluctuation ≤ ±0.1 °C.

Piston and Plunger Assembly

Precision ground.

Compatible with standard test loads (e.g., 2.16 kg, 5 kg, 10 kg).

Timing and Cutting Device

Timer accuracy 0.1 s.

Automatic or manual melt strand cutting for collection.

Digital Display and Data Output

Equipped with RS-232/USB interface.

Supports data export and printing.

IV. Operator Requirements

Familiarity with polymer material properties and common testing standards (ISO 1133, ASTM D1238).

Trained on the equipment and possessing basic knowledge of electrical and mechanical safety.

Wear personal protective equipment (PPE) compliant with laboratory regulations (Lab coat, heat-resistant gloves, safety glasses).

V. Safety Precautions

High-Temperature Burn Hazard:

Avoid direct contact with the heating barrel surface during operation.

Be mindful of gaps between the machine cover and heating elements.

Load Falling Hazard:

Keep hands secured on the load hanger while loading weights.

Never release weights while they are suspended.

Melt Splatter Hazard:

Hot melt splatter is possible during strand cutting.

Strictly wear a face shield or safety goggles.

Electrical Safety:

Ensure proper grounding.

Absolutely prohibit disassembling circuits or replacing components while the device is powered.

VI. Standard Operating Steps

6.1 Instrument Startup and Preheating

Check the oil circuit (if applicable), water cooling (if applicable), and ventilation; confirm no abnormalities.

Turn on the power supply and preheat the heating barrel to the test temperature (±1 °C).

Verify the consistency between the temperature display and a reference thermometer.

6.2 Sample Preparation

Place the plastic pellets or chips to be tested in a drying oven at 50 °C for 2 hours.

Weigh a sample mass ≥ 10 g to ensure continuous filling.

6.3 Installation and Loading

Remove the plunger.

Slowly fill the heating barrel with the sample using the charging funnel.

Insert the plunger and perform gentle tapping to ensure complete filling and avoid air gaps.

Select the standard test load (e.g., 2.16 kg) and hang it on the load hanger.

6.4 Pressurization and Temperature Stabilization

Start the timer. The piston descends into the sample under its own weight plus the standard test load.

Wait for temperature and pressure to stabilize, allowing continuous melt extrusion.

6.5 Melt Collection and Measurement

Precisely control the collection time according to the standard (generally 30 s or 60 s) using the timer.

Place weighing paper or a collection tray in front of the cutter.

Cut the extruded melt strand.

Weigh the mass of the extrudate, record as M1.

6.6 Calculation and Recording

Melt Flow Index (MFR, g/10 min) = M1 × 10 min / Test time (s).

Perform three independent tests, calculate the average value and standard deviation.

Record the results in the test report or the laboratory LIMS system.

VII. Routine Maintenance and Calibration

Cleaning the Heating Barrel:

After each test, allow the equipment to cool to room temperature.

Clean using a dedicated cleaning rod and cleaning material (e.g., polystyrene).

Temperature Calibration:

Calibrate the temperature display error monthly using a standard platinum resistance thermometer.

Load and Timer Calibration:

Check the mass of test load weights and timer accuracy quarterly; calibrate or replace as necessary.

Lubrication and Safety Inspection:

Periodically apply high-temperature grease to components like guide columns and slideways.

Inspect wiring, grounding, and the integrity of protective covers.

VIII. Summary

Standardized Melt Flow Index Tester Operating Procedures are critical for ensuring accurate, efficient, and safe testing. Operators must strictly follow the above steps, integrate with laboratory quality management requirements, and perform regular equipment maintenance and calibration. Only then can the reliability and repeatability of data be guaranteed, meeting the dual demands of research & development and quality control.