26 July 2021 Monday
15 points to consider when analyzing the drying methods for plastic granules
Selecting the right solution for plastic granule drying depends on several factors. Obviously, such factors often vary from case to case, as no two challenges are exactly the same. Therefore, we have compiled a list of issues, that usually need to be addressed, when searching for the best way towards green energy efficient and cost effective plastic granule drying.
Based on more than sixty years of experience, you might want to consider the 15 issues listed here, when looking for the best possible drying solution for your plastic granule:
- The chemical structure and consistency of the plastics material. Hygorgenic materials are obviously sensitive to atmospheric moisture.
- The level of moisture absorption of the material. Pigmentation and carbon black significantly increases the moisture absorption.
- The environment in which the production is taking place. Variations in temperature and humidity influence dew point. Changes in temperature between storage and processing can cause condensation.
- The variety of temperature and humidity at the production facility. Changes in the weather, particularly during the summertime, can give challenges with condensation.
- The service level and cleaning processes of the drying equipment. Contamination such as dust can attract moisture to the surface.
- The technical sophistication of the operatives of the equipment. Human error is always a factor in handling of the plastic granule materials. Technical variations in the plastic granule may warrant more calibration of the equipment.
- The type and quality of the finished application. Expected lifespan of the finished item is influenced by the level of moisture in the plastic granule.
- The color and consistency requirements to the finished items. Moisture content in the plastic granule influence the appearance with bubbles, blisters and discoloration.
- The need for regrinding. The drying process may cause excessive dust whom may cause rejects, however regrind is able to process with the correct selection of dust separation equipment with the drying system.
- Preventing agglomeration during the drying process. PET & PLA materials need both correct drying- and crystallizationequipment in order to process correctly, since both materials will agglomerate during the drying process.
- Over drying is common when the material flow is lower than the capability of the drying equipment. As a result, the material is residing in the drying hopper for a longer period than recommended. Temporary temperature reduction and air flow control, or a combination of both, is normally the preferred solution. The optimal solution is often an automatic volume regulation in the drying hopper, using loss in weight technology.
- The use of glass reinforced polymers are increasing globally and some polymers holds up to 50% glass content. The glass inside the granules can create "pockets" where the moisture may reside between the glass content and the polymer, such raw materials may extend the drying time as result.
- When drying polymers using vacuum technology, it may be difficult to achieve the appropriate residual moisture content required for correct processing, simply because a rapid process does not allow for the needed moisture evaporation.
- The production volume and exchange frequency of dies is more flexible with correct drying. Moisture can cause issues with drive- torque and -power as well as melt temperature, resulting in long calibration runs.
- The return on investment for the production line is influenced by choice of drying solution. Consideration is thus given to issues such as: volume, lifespan, complexity, and end product quality.
The timeframe and payback on investment in plastic granule drying depend on numerous interdependent factors. Frequently, such factors need to be evaluated together, when defining the solution. Moreover, the expected business case also sets the frame for the decision. A larger investment, for instance, may yield better returns, but take more time to break even.