Meaning
The specific parameters used to measure the melt mass flow rate and melt volume flow rate of thermoplastics provide a basis for material comparison. These iso 1133 test conditions define the temperature and load applied to a resin sample as it is extruded through a die of standard dimensions. The results help a moulder understand how a polymer will behave under the pressures of the injection barrel.
This standard ensures that data sheets from different manufacturers use a uniform baseline for their reported flow values. The method applies to both virgin pellets and recycled flakes destined for industrial production. It sets the limit for verifying the consistency of incoming raw material lots.
Flow Rate
Measuring how quickly a plastic melts and moves through a small opening allows for the grading of different resin types. The iso 1133 test conditions require the material to be preheated for a specific duration to ensure a uniform temperature throughout the sample. A piston then pushes the melt through the die under a constant weight, and the amount of material extruded is weighed.
This value is reported in grams per ten minutes and serves as a primary specification for buyers. If the flow rate is too low, the material may not fill the mould completely, leading to short shots. If it is too high, the part may suffer from flash or reduced mechanical properties.
Consistent testing prevents these processing issues and ensures a stable production environment.
Pressure Consistency
The load applied during the test must be precisely controlled to obtain repeatable results across different laboratory locations. Under the iso 1133 test conditions, the pressure on the melt is determined by the mass of the weights placed on the piston. Any friction between the piston and the barrel can lead to an incorrect reading and a false material grade.
Technicians must maintain the equipment regularly to ensure that the internal surfaces remain clean and smooth. This level of precision allows for the detection of small changes in molecular weight or additive levels. High pressure tests are used for materials with high viscosity while lower weights are used for easy flowing resins.
Reliable pressure management is the foundation of a defensible material certification process.
Material Grading
Resins are categorized into different flow groups based on the results obtained under standardized conditions. The iso 1133 test conditions provide a common language for designers, suppliers and moulders to discuss material suitability. When a part design requires a specific wall thickness, the engineer selects a grade that can reach the end of the cavity at a given pressure.
Switching to a different grade without retesting can lead to significant changes in the cycle time and the final part weight. Quality assurance teams use these grades to verify that every shipment of resin matches the original order. The cost of a dedicated melt flow indexer is small compared to the losses from using the wrong material grade.
Correct grading ensures that the manufacturing process is optimized for both speed and quality.
