PET Drying Windows and the Hydrolysis a Moulder Absorbs
Excess residual moisture causes instant ester chain hydrolysis in molten PET, dropping intrinsic viscosity and destroying mechanical part strength.
Mass Flow Hopper
Meaning
Gravity storage vessels engineered with steep wall angles and smooth surfaces eliminate stagnant zones during bulk solid handling. Specifying a mass flow hopper ensures every resin pellet or flake moves downward at uniform velocity during extruder vessel discharge. Material handling managers install these units upstream of drying systems to achieve consistent thermal exposure times.
The design criteria depend on specific internal friction properties, meaning a vessel optimized for pellets may fail when loaded with irregular regrind.
Hopper Geometry
Wall angles exceeding sixty degrees combined with low-friction internal liners promote uniform particle velocity across the entire vessel cross-section. Designing a mass flow hopper requires measuring the internal friction angle and wall friction angle of target polymer feeds. Cone angles that are too shallow induce funnel flow, causing wide variations in pellet residence time.
Correct geometry prevents ratholing and stable arch formation above the outlet flange.
Material Discharge
Particle movement follows a strict first-in, first-out sequence that maintains consistent bulk density at processing machine throats. Utilizing a mass flow hopper eliminates erratic feed fluctuations caused by core flow piping or localized material consolidation. Stable bulk feeding minimizes extruder pressure fluctuations and improves sheet thickness uniformity across continuous extrusion runs.
Virgin and regrind mixtures remain evenly distributed without bulk phase separation.
Process Reliability
Consistent flow prevents processing delays. Sluggish feed problems are eliminated.