No. 17 - Melt Indexers

The melt indexer originated with ICI in England as an adjunct to its work on developing LDPE in the 1940s. DuPont also used early melt indexers manufactured by Swiss Slocomb in its LDPE work.

The melt-flow test detailed in the ASTM D1238 and ISO 1133 standards quickly measures one point on the viscosity curve under standard conditions. While the test today retains its relative simplicity, melt indexers have evolved considerably. Computerization and automation have reduced operator variables, yielding results with greater accuracy and repeatability. Some models feature auto-tuning PID temperature control with feed-forward circuitry to provide fast response without overshoot.

The first melt indexers to be introduced in the U.S. came from Slocomb, followed soon after by Tinius Olsen in 1958-59. Tinius Olsen’s Model 1 was its first “true” melt indexer. Prior to that, the company had been making a parallel-plate plastometer since 1948, which was designed for determining flow characteristics of polymers at low shear rates.

Other melt indexers were launched by Dynisco Polymer Test (formerly Kayeness), Ceast, Haake, Goett fert, and Atlas Electric Devices.

In 1995, Creative Technology Systems, Inc. (CTS), acquired the rights to Slocomb’s device and came out with upgraded models.

A melt indexer is just about the very first instrument plastics molders, extruders, and compounders are likely to consider when outfitting a lab. With the pressure on plastics processors to comply with ISO 9000 standards for quality management, these instruments are being used more than ever to evaluate incoming material and test finished products.