Karl Fischer Moisture Testing of Recycled Polyethylene Terephthalate
Coulometric Karl Fischer testing with oven desorption at 170 °C isolates true water content in rPET below 50 ppm, preventing costly IV degradation during melt processing.
Bottle Preform Extrusion
Meaning
Manufacturing stage where molten resin is shaped into a thick-walled tube intended for subsequent blow molding. Although many containers start as injection-molded parts, bottle preform extrusion refers to the continuous production of hollow profiles used in reheat-and-blow or direct-blow systems. The process determines the initial wall thickness and weight of the final container.
Melt Stability
Consistent viscosity is necessary to maintain the dimensions of the extruded shape. During bottle preform extrusion, the screw speed and barrel temperature are balanced to prevent thermal breakdown of the polymer. Regrind levels must be monitored to avoid fluctuations in melt strength.
Dimensional Control
Vacuum sizing tanks and puller speeds define the outer diameter and wall thickness of the tube. When bottle preform extrusion produces an uneven wall, the final bottle exhibits weak spots or thin sections that fail under pressure. Calibrating the die gap ensures a uniform material distribution around the circumference.
Precise control of the cooling bath prevents the tube from collapsing or ovalizing before it hardens.
Output Efficiency
High-volume lines rely on high throughput rates to remain competitive. Optimizing bottle preform extrusion involves matching the cooling capacity of the water tanks to the line speed. Continuous monitoring reduces the volume of scrap material generated during start-up.