The single mass method (constant weight loading method) is one of the commonly used testing methods for melt flow rate instruments (MFR)–YYP-400E;
The core of this method is to apply a constant load to the molten plastic using a fixed mass weight, and then measure the mass of the molten material flowing through the standard die at a specified temperature and time to calculate the flow rate. Its advantages are mainly reflected in multiple aspects such as operation, accuracy, applicability, and cost. The details are as follows:
1. The operation process is simple and straightforward, with strong directness. The single mass method only requires the configuration of fixed-sized weights and does not need complex load switching devices. During the test, simply heat the sample to melt, load the fixed weight, time it, and collect the flowing molten material. The steps are few and the standardization is high, with low skill requirements for operators, and it can be quickly mastered and repeated. Compared with the variable load method (such as the multi-weight test for melt volume flow rate MVR), it eliminates the need to replace weights and calibrate loads, significantly reducing the preparation time for a single test.
2. The test data is highly stable and the error is controllable. Under constant load, the shear stress on the molten material is stable, the flow rate is uniform, and the fluctuation in the collected molten material mass is small, resulting in good repeatability of the MFR value. The quality accuracy of the weights can be strictly controlled through calibration (with an accuracy of ±0.1g), avoiding additional errors caused by weight combinations and mechanical transmission in the variable load method. This is particularly suitable for precise testing of low-flow plastic (such as PC, PA) or high-flow plastic (such as PE, PP).
3. The equipment structure is simplified, the cost is lower, and maintenance is convenient. The MFR instrument using the single mass method does not require a complex load adjustment system (such as electric loading, weight storage), and the equipment is smaller in size, with fewer components, resulting in a 20% to 40% lower procurement cost compared to multi-weight type instruments. Daily maintenance only requires calibrating the weight of the weights, cleaning the die and barrel, and no maintenance of the transmission or control system is needed. The failure rate is low, the maintenance cycle is long, and it is suitable for routine quality inspection in small and medium-sized enterprises or laboratories.
4. It complies with standard requirements and is suitable for common quality inspection scenarios. The single mass method fully meets the requirements of mainstream standards such as ISO 1133-1 and ASTM D1238, and is a conventional method for the incoming inspection of plastic raw materials and the quality control of the production process. For the factory inspection of most general plastics (such as PE, PP, PS), only the standar fixed load (such as 2.16kg， 5kg) is required to complete the test， without the need for additional parameter adjustment， and it is suitable for the needs of industrial large-scale quality inspection.
5. The data results are intuitive and for the purpose of comparative analysis. The test results are presented directly in “g/10min” units， and the numerical size directly reflects the fluidity of the molten material， making it easy to conduct horizontal comparison between different batches and different manufacturers of raw materials. For example： for the same brand PP raw material， if the MFR of batch A is 2.5g/10min and that of batch B is 2.3g/10min， it can be directly judged that batch A has better fluidity， without the need for complex conversion or data processing.
It should be noted that the limitation of the single quality method lies in its inability to measure the shear rate dependence of the melt. If one needs to study the rheological properties of plastics under different loads, a multi-load type MVR instrument or a capillary rheometer should be used in combination.
Post time: Dec-13-2025