What Are Quality Tests for Recycled Plastics?

Melt Filters

Melt Indexer: One of the measures of melt flow is the molecular weight of the material. This measure determines the performance of the material in different areas of use. Upon customer request or if the recycling processor decides this, a capillary rheometer can be included in the quality control process to obtain more detailed information about the viscosity of the material.

 Moisture analyzer: The moisture of the recycled flakes should be measured as well as the starting pellet. Residual moisture can cause defects that can affect quality and performance in subsequent recycling stages. Said moisture comes from the water that the plastic comes into contact with in recycling. The purpose of washing and flotation with water is to determine the density of the plastic and to limit it accordingly, and to ensure that the pollutants in the plastic are removed with water. Recycled plastic may have problems with insufficient coloration, widening, strength, and poor performance if moisture testing is not performed or if the output has a high humidity level. 

 Near-infrared spectroscopy: The purpose of the measurement with this test is to measure the health of the finished product and a NIR unit is used for this. This is because recycled plastics go through many processes before they become output. This makes it important to control purity. It is an analysis that should generally be used for PP and PE. Because PP and PE are not completely separated. The measurement results of this recycled plastic material can be compared with resins of the required health, so that its content and purity can be learned.

 X-ray fluorescence: In this measurement, it detects brominated flame retardants and chlorine contents, which are prohibited for use in some manufacturing industries. Because even though they are recycled, plastics should not contain these substances. X-ray analysis is the only way to measure the presence of these substances. Therefore, recycling processors should know which of their customers will need this test and incorporate XRF analysis into their quality control process.

 Oven. While it may seem insignificant, customers often request this test be done because the ash content of recycled plastic can cause some problems. We can call this analysis baking. The polymer is taken into a furnace where it can be properly incinerated, and the residual ash content is measured after complete combustion. This is an analysis performed for each batch.

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