Melt Flow Figures Quoted without Their Load and Temperature
An unconditioned melt flow value lacks physical meaning without its test load, temperature, and standard protocol specified.
Material Acceptance Testing
Meaning
Quality assurance procedures performed on incoming batches of polymer resin verify that the material complies with the purchase specification before it is released to the production line. Conducting material acceptance testing prevents the introduction of out-of-specification resin that could cause molding defects or premature part failure. This process typically evaluates properties such as melt flow rate, moisture content, and density.
Molders use these values to confirm that the supplier has delivered a consistent product that matches the approved datasheet.
Testing Protocol
Melt flow rate and moisture analysis are the most common laboratory assessments conducted on incoming pellets. Through material acceptance testing, the molding shop can identify batches that have absorbed excess water, which would cause hydrolytic degradation and loss of mechanical strength in polyamides or polycarbonates. If the melt flow rate is too high, it indicates a lower molecular weight, which translates to reduced impact resistance in the molded parts.
Sourcing Economics
Verification of resin properties is especially critical when purchasing recycled or regrind blends, which exhibit higher variability than virgin resins. Implementing a rigorous material acceptance testing routine protects the molder from costly downtime and tool damage caused by contaminated feedstock. If a batch fails the test, the material is rejected before it can enter the silo, avoiding the cost of purging the molding machines and scrapping molded parts.
Process Stability
Adjusting injection parameters to compensate for minor batch-to-batch variations is made possible by using the test data. Consistent material acceptance testing provides the molding team with the necessary insights to maintain stable cycle times and uniform part dimensions across long production runs.