Quality / Raw Metrial

Raw Material Inspection
Most raw plastic materials are quality inspected in resin or fiber form. For resins, the main criteria include viscosity, moisture levels, and color, while continuous fiber is often examined for its tensile strength. Infrared or nuclear magnetic spectroscopy is typically used to identify basic chemical structures and contamination levels. Other standard methods include wet chemical analysis, which reveals the main acid or epoxide groups in a plastic compound, and liquid or gel chromatography, which determines the average molecular weight and weight distribution among resin molecules.

Chromatography techniques can be particularly useful because molecular weight and distribution are major influences on a plastic material’s viscosity and mechanical characteristics. In polyester, lower molecular weights generally yield higher levels of viscosity, resulting in a slower rate of thickening. This can make the plastic more difficult to handle or prohibitively long to thicken to the appropriate degree. Moisture levels can also affect the thickening rate.

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