A Case Study: Failure Analysis of a Thermoplastic Elastomer;

Melt Flow Index (MFI) Method Provided Critical Data Sets

The Case

For companies that manufacture rubber and plastic parts, processing issues are a serious contributor to reduced profit and increased waste. Rapid evaluations that can pin-point the root cause of a process issue are vital to maintain productivity. In addition, third-party materials evaluations often serve to swiftly identify raw material compliance issues. Based on scientific data, the business issues caused by the raw material can be properly addressed and the production process can get back on track.

As is typically the case, Polymer Solutions Incorporated received a pair of samples that were described as "good" and "bad." It was critical to our client and the rapid resumption of their manufacturing process that an objective science-based determination be made as to whether or not there were variations in the raw material. Comparative testing of the two samples was performed. From a root cause analysis perspective, three analytical methods were proposed and implemented. This was considered to be a technically appropriate, robust, and cost-effective first step. The three analytical methods included:

• Thermogravimetric Analysis (TGA) to Determine Inorganic Filler Content
• Differential Scanning Calorimetry (DSC) to Document Thermal Transitions
• Melt Flow Index (MFI) Tests to Compare Melt Flow Characteristics

Full Study> Failure Analysis (pdf 1.2MB)

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The Approach

Small portions of Good and Bad extrudates were cut using scissors and a razor blade. These specimens were then dried at 120°C in a convection oven. Preliminary melt flow index (MFI) tests were performed. Two critical observation resulted.

In order to compare the degradation profile of the two samples, thermogravimetric analysis (TGA) was carried out using a TA Instruments Q500 instrument. Approximately 15 mg of sample was placed in a tared platinum TGA pan and heated from 30°C to 900°C at 10°C per minute in an atmosphere of air. The inset Figure shows the TGA curves that were recorded for this pair of samples.