GB/T 40934-2021 specifies the test method for determining the flowability of powder for rotational molding. It applies to freely flowing powder materials with a particle size D₉₈ ≤ 1 mm and an apparent density ≥ 0.21 g/mL. The standard defines the test principle, sample preparation, operating procedures, and requirements for result calculation. The core equipment includes a specially designed aluminum alloy funnel, a timer with a division value ≤ 0.1 s, an electronic balance with an accuracy of 0.1 g, and a plug gauge meeting specified tolerance requirements. Under conditions of 23°C and 50% relative humidity, the time required for 100 g of the sample to flow out of the funnel is measured. The flowability value is then calculated to characterize the free-flowing capability of the powder, providing a technical basis for material selection and process optimization in rotational molding production.