Measurement of Resin Pellets

Instrumental Innovation Through Automation

With the new automatic sample rotator from BYK-Gardner it is now possible to measure plastic pellets with minimum operator´s effort. The sample rotator is mounted on top of the 45/0 bench-top spectrophotometer color-view. It uses a rotating system that is powered by the instrument. The pellets are poured into a large sample container simulating an infinite film thickness. The container is covered by a lid to avoid any influence of ambient light. As the container is turning over a defined time period, refilling becomes obsolete.
The Windows® based color control software auto-QC that is supplied with each color-view, allows measurement interval time to be set individually dependent on shape and size of pellets.
Using this procedure, multiple measurements are taken on different regions of the sample cup, simulating a much larger measured area than practically used.

Comparing Results: Automated Versus Manual

There is a distinct advantage in using automated sampling over manual as shown in the graph. An intermediate, disc shape pellet type was measured using the manual method as well as the automatic sample rotator.

Each bar represents the standard deviation of 20 readings taken by the same operator. Noticeably, the automated method shows less variation in yellowness index when compared to the manual method of preparation.

Conclusions:

color-view with the automatic sample rotator

  • provides an elegant solution for cost effectively evaluating a significantly larger sample volume
  • improves the variance of averaged results
  • reduces sample preparation time for the operator
  • improves precision within a plant and from plant to plant because each operator will uniformly prepare samples

Sample Preparation Up To Now

Because of the irregular nature of pellets, it is essential that multiple measurements are made and the average is used to represent the sample.
Ideally, a new sample of pellets would be prepared in a glass cup for each measurement. This is impractical due to time pressure on the operator. Instead, often only one sample is prepared and measured. To make additional measurements, the same sample is shaken or vibrated within the cup and then measured again. Variation in shaking technique among instrument operators as well as random distribution of the pellets in the cup provide sources of measurement variance.

Yellowness Measurement of Plastic Pellets Has Never Been Easier!

The yellowness of transparent plastic pellets like polyethylene and polypropylene is a critical parameter because it influences the color of the final product. Nevertheless, measurement of pellets can be a challenge because they come in a variety of shapes and sizes.