Melt Flow Indexer

The melt flow indexer is also called a melt flow rate tester, melt indexer, melt index tester, melt flow index tester, etc.

Melt flow rate is the extrusion rate of a melt through a standard die of specified length and inner diameter under specified conditions of temperature, load, and piston position. The mass extruded in a specified time is the melt mass-flow rate (MFR), in grams per 10 minutes (g/10 min); the volume extruded in a specified time is the melt volume-flow rate (MVR), in cubic centimeters per 10 minutes (cm³/10 min). Melt flow rate characterizes the viscous flow behavior of thermoplastics in the molten state.

According to different testing principles, melt flow rate testers can be divided into mass method (MFR) melt flow indexers and volume method (MVR) melt flow indexers; in instrument design, both methods can be integrated into one device.

Melt Flow Indexer Explained

Definition: Melt flow rate is the extrusion rate of a melt through a standard die of specified length and inner diameter under specified conditions of temperature, load, and piston position. The mass extruded in a specified time is the melt mass-flow rate (MFR), in grams per 10 minutes (g/10 min); the volume extruded in a specified time is the melt volume-flow rate (MVR), in cubic centimeters per 10 minutes (cm³/10 min).

Melt flow rate characterizes the viscous flow behavior of thermoplastics in the molten state, and has important guiding significance for ensuring the quality of thermoplastics and their products and for adjusting production processes. It applies both to engineering plastics with high melting temperatures such as polycarbonate, polyarylsulfone, fluoroplastics, and nylon, and to plastics with lower melting temperatures such as polyethylene (PE), polystyrene (PS), polypropylene (PP), ABS resin, polyoxymethylene (POM), and polycarbonate (PC) resin. It is widely used in plastics production, plastic products, petrochemicals and other industries, as well as related universities, research institutions, and commodity inspection departments.

The melt flow indexer is suitable for determining the melt mass-flow rate of thermoplastics as specified in the national standard GB/T 3682-2000 "Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics." This standard is identical to ISO 1133:1997, and the instrument also meets the ASTM D1238 test standard.

Melt mass-flow rate and melt volume-flow rate have been clearly specified in ISO standards, and China's standards will be revised accordingly. In import and export business, the determination of melt volume-flow rate will soon be applied.

Melt Flow Indexer Construction

The melt flow indexer mainly consists of a heating furnace, temperature control module, intelligent control, human-machine interface, load weights, printer, and other parts.

The lower part of the instrument is the temperature control system, which adopts intelligent PID temperature control technology with strong anti-interference ability and high control accuracy, automatically controlling the temperature inside the main barrel within the set range, with temperature fluctuation maintained within ±0.2°C to ensure test stability. The upper part is the heating furnace; its barrel heater consists of two sets of heating elements — one set supplies the heat required to bring the barrel to the set temperature with continuous current supply, while the other maintains the barrel temperature within the fluctuation range. Different manufacturers use different heating methods, such as heating jackets or heating rods, but regardless of the method, precise temperature control must be achieved to meet standard requirements. The human-machine interface allows setting of test temperature, cutting count, cutting interval, material type, material weighing, etc. The mass load of the weights acts on the molten sample in the barrel via the piston rod, pressing the melt out of the capillary. During testing, extruded melt strands are cut at regular intervals and weighed to obtain the sample's melt index; the printer can print test results in real time or from query records.

Standard Melt Flow Indexer

A standard melt flow indexer is a basic instrument that meets the fundamental test requirements for melt index and complies with relevant national standards. These basic requirements include: a precise temperature control system; support for both mass method (MFR) and volume method (MVR) test methods; and an over-temperature protection device. In addition, it should have common basic functions such as printing, integrated manual/automatic cutting, data storage, and automatic result analysis.

According to user operation preferences and system maturity, they are generally divided into touchscreen melt flow indexers and push-button melt flow indexers.