Meaning
Nucleated polyethylene terephthalate resin formulations engineered for dual-ovenable packaging achieve rapid crystallization during thermoforming processes. Within tray manufacturing operations, cPET-3 defines a specific material grade possessing high heat deflection temperatures and precise nucleator loading. The specification boundary excludes non-crystallizing packaging applications where optical clarity takes precedence over thermal resistance.
Thermal Behavior
High degree of crystallinity imparts structural rigidity to thin-wall containers exposed to conventional oven temperatures up to two hundred degrees Celsius. Differential scanning calorimetry measures peak crystallization temperatures and enthalpy during cooling cycles for cPET-3 sheet production. Rapid spherulite growth during forming prevents sag and wall thinning in deep-draw tray geometries.
Unfilled resin grades fail to reach the twenty-five percent minimum crystallinity needed for thermal stability under high service heat.
Moulding Control
Heated thermoforming moulds operating between one hundred twenty and one hundred forty degrees Celsius induce rapid crystallization of the extruded sheet. Molders processing cPET-3 must balance tool contact time against line speed to prevent part sticking or incomplete crystalline structure. Regrind incorporation above fifteen percent alters crystallization kinetics and destabilizes container wall stiffness during baking cycles.
Datasheet values for tensile modulus reflect fully crystallized test specimens, whereas actual packaging performance depends on mould temperature control across the web.
Processing Margin
Intrinsic viscosity maintenance during sheet extrusion dictates impact resistance at sub-zero temperatures. Moisture content in cPET-3 resin must remain below fifty parts per million prior to processing to prevent hydrolytic chain scission in the extruder barrel. Melt temperature management prevents thermal degradation while providing sufficient flow to fill complex rim details.
