Melt Volume-Flow Rate Tester

What is the Melt Volume-Flow Rate Tester?

A melt volume-flow rate tester measures piston displacement with a high-resolution encoder instead of weighing cut extrudate, giving a fast, automated result in cubic centimetres per ten minutes. It is preferred when the material is difficult to cut cleanly or when results are needed quickly.

Overview

Method B of ISO 1133 determines flow from the distance the piston travels in a known time once steady flow is established, for example 0.25 in or 6.35 mm. A high-resolution encoder registers that distance, the software applies the barrel cross-section and time base and reports MVR directly. Because the measurement needs no cutting and weighing, it removes operator timing error and reduces test duration to a few minutes of steady flow after the preheat. The same data can be converted to MFR using the melt density at the test temperature, and instrument software typically stores density values per material so both numbers are reported together. The result is more sensitive to piston friction, temperature uniformity and correct die seating than the gravimetric method.

How does it work?

A melt flow tester consists of a heated vertical barrel with a defined bore, a hardened steel die at the bottom, a piston and a set of certified weights. Polymer granules are loaded, compacted and held at the test temperature, then extruded through the die under a specified load. In method A, timed portions of extrudate are cut and weighed, and the result is expressed in grams per ten minutes. In method B, an encoder records piston displacement against time and the melt volume-flow rate is calculated in cubic centimetres per ten minutes, which can be converted to mass flow using the melt density. Temperature, load, die geometry and thermal equilibration time are all fixed by the method, because melt viscosity depends steeply on temperature and shear rate.

What are the key features?

• Encoder-based piston displacement measurement
• Direct MVR output in cm³/10 min
• MFR calculation from stored melt density
• No cutting or weighing required
• Raw displacement curves saved with each result
• Repeatability verified with reference polymers

What are the technical specifications?

A typical melt volume-flow rate tester configuration offers measuring principle of Piston displacement, ISO 1133 method B, displacement resolution of 0.01 mm, MVR range of 0.1–2000 cm³/10 min, temperature range of 50–400 °C, temperature accuracy of ±0.2 °C and load weights of 1.2 / 2.16 / 5 / 10 / 21.6 kg. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Melt Volume-Flow Rate Tester is used in rapid QC of polyolefin production lots, materials that tear or curl when cut, comparison of uncoloured base resins and automated testing lines with data export. Across the wider Melt Flow Testers class, laboratories also deploy it for polyolefin resin production and grade certification, incoming inspection of polyethylene and polypropylene and recycled plastics quality screening.

Which standards and certifications apply?

Relevant standards and methods include ISO 1133-1, ISO 1133-2, ASTM D1238, GB/T 3682.1, GB/T 3682.2 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Install the tester on a level, vibration-free bench away from draughts, and allow the barrel to reach thermal equilibrium before the first test, which usually takes 15 to 30 minutes. Clean the barrel and die after every test or every material change, using purging compound for degraded polymer; never scrape the barrel bore with hardened tools. Verify temperature with an external thermometer in the bore at defined intervals, check die dimensions against the method tolerance, and keep weights traceable. Dry hygroscopic polymers before testing, discard any extrudate containing bubbles or voids, and repeat the test when a single cut deviates strongly from the others.

How do I select the right Melt Volume-Flow Rate Tester?

Choose method B when cutting is unreliable or when the laboratory reports results into a digital QC system and wants minimal manual steps. Confirm that the software supports your melt densities and can recalculate between MVR and MFR, because customers often specify one of the two. Verifying piston friction and die seating should be written into the procedure, since these are the most common reasons for disagreement between method A and method B results.

How does it compare with other Melt Flow Testers variants?

Start from the standard your customer or specification cites, because ISO 1133 and ASTM D1238 fix different loads and procedures. Method A is sufficient for routine resin grading, while method B is preferable when the laboratory needs a fast result or the material is difficult to cut cleanly. Choose a high-temperature barrel when the scope includes engineering polymers such as polyamide, polysulfone or polyether ether ketone, and a corrosion-resistant barrel for PVC and fluoropolymers. Automatic units pay back where more than about ten tests per day are run, and multi-station units suit polyolefin plants that compare several production lines in one shift. Specify the load set, temperature range, data export format and cleaning accessories.