Evaluating Dew Point Drift and Desiccant Degradation in Twin Tower Dryers
Dew point drift above minus forty degrees Celsius triggers rapid hydrolytic polymer degradation, demanding structured bed adsorption and crush testing.
Attrition Rate
Meaning
Material loss occurring during polymer compounding and regrind processing describes the attrition rate. Thermoplastic pellet degradation generates fine particles and dust through pneumatic conveying friction and mechanical feeder shear. Processors measure this mass fraction to control hopper feeding consistency and prevent die blockages during high speed extrusion.
Extrusion lines handling abrasive mineral filled polyamides monitor material breakdown closely to avoid screw wear and pressure surges. Production technicians set this parameter during twin screw compounding trials where feeder screw speeds govern mechanical work input.
Regrind Degradation
Thermal history accumulation alters polymer chain length and increases brittleness during subsequent processing runs. Granulator blades shatter brittle regrind particles and produce excessive fines that disrupt melt flow stability. Virgin resin exhibits minimal breakdown under identical mechanical stress due to higher molecular weight distributions.
Moulders balance virgin pellets with regrind fractions to maintain target melt flow indices without triggering severe output fluctuations.
Processing Defect
Excessive material fines cause uneven feeding behavior inside starvation zones and generate severe gauge variations across extruded film sheets. Blocked vacuum ports result from fine particles entering downstream degassing vents during high throughput compounding operations. Defective moulded components display surface blemishes and localized weak spots whenever degraded feedstocks enter injection barrels.
Tooling designers specify larger runner diameters and modify gate geometries to accommodate wider particle size distributions without pressure spikes.
Quality Threshold
Strict material specifications limit allowable dust generation to specific weight percentages before raw material shipments face rejection at the receiving dock. Datasheet values represent ideal laboratory conditions that rarely match the degradation observed across full scale production runs. Moulders establish internal quality limits to catch excessive pellet fracturing before feedstock reaches sensitive hot runner injection systems.
Finished part structural integrity depends directly on maintaining stable feedstock morphology throughout the entire manufacturing cycle.