Do you know the main problem of first production procedure?

The first one main problems exist in the production process of PVC sheet before the production of seed planting tray.

1). The sheet gets yellow

1. The stability of PVC material is relatively poor. If it is a new raw material supplier, it can be replaced with an old supplier. But even the raw materials of old suppliers have different quality because of different batches, which may cause yellowing.

2. The heat resistance of PVC resin is relatively poor, and its solubility temperature is close to the decomposition temperature, so it is necessary to choose loose suspension, high whiteness, and appropriate viscosity. Resin with good thermal stability, average molecular weight is basically the same, easy to plasticize, short molding time.

There is a problem with the temperature controller. The display temperature is lower than the actual temperature. If the temperature is too high, the PVC will decompose and yellow. At this time, you need to recheck the calibration temperature controller, you can calibrate with a mercury thermometer. In actual production, due to the loosening of the thermocouple or the adhesion of materials, the temperature displayed by the temperature controller will be different from the actual temperature.