Polycarbonate (PC) is an amorphous engineering material with exceptionally good impact strength, heat resistance, clarity, sterilizability, flame retardancy, and stain resistance.
PC grades are hygroscopic and pre-drying is important. Recommended that drying conditions are 100 C 120 C [212 F 248 F] for 3 to 4 hours. Moisture content must be less than 0.02% before processing.
260 C 340 C [500 F 644 F]; higher range for low melt mass-flow rates (MFR) grades and vice-versa.
70 C 120 C [158 F 248 F]; higher range for low MFR grades and vice-versa.
As high as possible for rapid molding.
Slow injection speeds when small or edge gates are used; high speeds for other types of gates.
PC is a polyester of carbonic acid. All general-purpose polycarbonates are based on bisphenol A. The bisphenol A component of the molecule contributes to the high glass transition temperature (150 C [302 F]). The rotational mobility of the carbonyl group within the molecule contributes to the high ductility and toughness of the material.
The notched Izod impact strength of PC is high and mold shrinkage is low and consistent [0.1 0.2 mm/mm].
High molecular weight PCs (which translate to low MFR) have higher mechanical properties, but processability of such grades becomes difficult. Base the type of PC chosen for an application on the desired criteria. For high-impact properties, use a low-MFR PC; conversely, for optimal processability, use a high-MFR PC.
The melt viscosities are typically Newtonian up to shear rates of 1000 1/s and decrease beyond that point. The Heat Deflection Temperature Under Load is typically between 130 140 C [266 284 F] and the Vicat Softening Point is typically around 155 C [311 F].