Why Melt flow index cannot be tested in nylon 6?

The melt flow index (MFI) cannot be effectively tested in nylon 6 due to its hygroscopic nature, which means it readily absorbs moisture from the environment. This moisture can cause hydrolysis during the melting process, leading to inconsistent and unreliable flow measurements. Additionally, nylon 6 typically has a high viscosity and can degrade at elevated temperatures, further complicating MFI testing. For these reasons, alternative methods like capillary rheometry are often preferred for assessing the flow characteristics of nylon 6.