With global plastic production soaring to almost 450 million tonnes annually, slight variations in polymer quality can quickly cascade, leading to scrap, downtime, or even recalls. Stephanie Williams, senior product specialist at Instron, states that melt flow testing (MFT), a precise “flow speed” test, helps ensure consistency and efficiency in polymer processing for medical device manufacturing.
Precise control begins at the pellet level. Even slight variations in polymer composition can affect melt flow and final part performance. Image: Instron
During MFT, molten polymer is forced through a die under standardized conditions, yielding a melt flow rate (MFR) in grams per 10 min (g/10min). While high MFRs can ease mold filling and cycle times, they can also signal thermal degradation, especially in engineering materials such as polycarbonates or acrylonitrile butadiene styrene (ABS), risking weaker, crack-prone parts. Conversely, low MFRs usually indicate stronger molecular chains but complicate processing due to higher viscosity and greater energy demand. For quality assurance, however, MFR can also reveal inferior or incorrect products.
MFT also aids production-floor quality control. For example, a medical device maker faced complaints about hairline cracks in prefilled syringes after shipment. MFT confirmed the pellets used for the syringes met viscosity specifications and, therefore, the manufacturer had received the correct batch.
This knowledge enabled the company to shift focus to its production processes. Upon investigation, an unevenly heated cavity in an injection press caused poor flow and weak walls. Without MFT, blame might have fallen on suppliers, leading to wasted material and regulatory issues. Instead, fast, consistent MFR results enabled targeted fixes and prevented costly disruptions.
Instron’s melt flow tester has a touchscreen directly on the instrument. Mirroring the look and feel of Bluehill Melt software, it guides users step by step, allowing operators to be trained and testing in under an hour. Image: Instron
Additionally, with sustainability goals now mainstream, compounders are increasingly using recycled or mixed-source polymers, with forecasts predicting the global recycled plastic market will reach $107 billion by 2032. With this shift comes variability in composition and degradation, and makes ensuring consistent processing and performance more important than ever.
MFT offers a quick check. If a recycled HDPE batch shows an MFR of 25 g/10min instead of the expected eight, it may indicate degradation or contamination. While MFT cannot identify exact chemistry, it can flag nonconforming batches before they reach production. For compounders, tracking MFR helps determine whether a batch meets specs, needs blending, or should be rejected.
The extrudate reveals how the polymer flows under heat and pressure, which is key data for maintaining consistency in medical and industrial applications. Image: Instron
With millions of tonnes of plastic produced each year, ensuring consistent polymer quality through melt flow testing is vital to reducing waste and preventing defects.
Instron
instron.com
Filed Under: Medical-device manufacture, Materials • advanced
