How PET Drying to Measure Moisture ?

Polyester polymer chips such as PET are hygroscopic and absorb moisture from the surrounding atmosphere. Too much moisture in chips can cause problems during injection molding and extrusion. When plastic is heated, the water it contains hydrolyzes PET, reducing its strength and quality. It means removing as much moisture as possible from the resin before processing the PET in the molding machine. Under atmospheric conditions, resins may contain up to 0.6% by weight water.

So How PET Drying to Measure Moisture ? 

Here we List Two Tips You Should Care when do PET Drying to Measure Moisture.

PET Pellets Are Dried Before Processing

The wood chips are loaded into the hopper, then hot, dry air with a dew point temperature of about 50°C is pumped into the bottom of the hopper, and it flows upwards over the pellets, removing any moisture en route. The hot air leaves the top of the hopper and passes through the after cooler first, as cold air removes moisture more easily than hot air. The resulting cold, moist air is then passed through the desiccant bed. Finally, the cold, dry air leaving the desiccant bed is reheated in the process heater and sent back through the same process in a closed loop. The moisture content of chips must be less than 30 ppm before processing. When PET is heated, any water present will rapidly hydrolyze the polymer, reducing its molecular weight and destroying its physical properties.

Online Measurement and Spot Check 

There are two techniques for measuring moisture during drying: online measurement and spot check.

① online measurement 

Individual dryers are continuously monitored to ensure that the air supply to the PET is better than the specified dew point temperature limit of 50°C dew point to ensure that the chip material is effectively dried. Where precise measurements with automatic internal calibration are required, can install the HT-608 dew point sensor near the inlet of the drying hopper, and its small size and lightweight make it easy to install in ducts or tight areas to check for leaks in the dryer's air path. High accuracy ±0.2 ° C (5-60 ° C Td), comparable to the quality of imported products, affordable, is a cost-effective alternative.

② Spot check and calibrate 

Regular spot checks with Hengko HK-J8A102 portable calibrated temperature and humidity meterc portable calibrated temperature and humidity meter can provide cost-effective product quality assurance. It's easy to use, simultaneous measuring the temperature, humidity, dew point, wet bulb, and other data. Respond quickly to industrial standard dew points below 50℃.

The dew point measurement range of the temperature and humidity meter is -50℃-60℃, and the large LCD screen is convenient for reading and reading. The measurement data is calculated once every 10 milliseconds, and the response speed is sensitive, and the measurement is accurate.

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