Desiccant Dryer Operation and Basic Moisture Management in Hygroscopic Polymers
Maintaining desiccant dryers at -40°C dew point prevents hydrolytic degradation, preserving melt viscosity and mechanical performance in hygroscopic polymers.
Synthetic Zeolites
Meaning
Crystalline aluminosilicates with highly uniform pore structures are used as functional additives in polymer compounding to absorb moisture, odors and volatile compounds. In polymer sourcing, synthetic zeolites are added to resins like polyamides, polyesters and recycled polyolefins to prevent moisture-related defects during high-temperature injection moulding. They act as molecular sieves that capture water molecules before they can cause hydrolytic degradation of the polymer chain.
Moisture Control
Polymers that absorb moisture from the air require extensive pre-drying before they can be moulded without defect. When drying is insufficient, adding synthetic zeolites to the masterbatch prevents the formation of silver streaks and splay marks on the surface of the moulded part. This chemical scavenger absorbs the moisture within the melt, maintaining the molecular weight and mechanical properties of the finished product.
Recycled Polymers
Recycled plastics often carry unpleasant odors from their previous life or from volatile organic compounds released during extrusion. Using these crystalline additives allows moulders to produce high-value parts from low-cost recycled resins by trapping the volatile by-products within the zeolite’s porous framework. This compound integration helps molders satisfy customer requirements for low-odor materials in automotive interiors and consumer goods.
Extrusion Stability
Gas bubble formation during extrusion causes voids and structural weaknesses in plastic films and sheets. These functional additives eliminate the moisture that causes foaming, ensuring a uniform melt density and a more stable extrusion process.