Polycarbonate (PC) is supplied in both high- and low-viscosity molding and extrusion grades, both based on the same bisphenol-A (BPA) homopolymer chemistry. The two grades share identical density, pricing, and the great majority of mechanical, thermal, electrical, and environmental properties – differing chiefly in molecular weight. The high-viscosity grade’s higher molecular weight gives it markedly greater impact toughness (up to roughly three times higher in unnotched impact strength) and a modest edge in heat deflection and maximum service temperature, but it is harder to process, requiring higher melt temperatures and molding pressures. The low-viscosity grade trades some of that toughness for easier processability, slightly better elongation at break, and marginally lower processing energy and emissions. The table below sets the full property sets of both grades side by side, with the properties that actually differ between them highlighted for quick reference.
| Property | PC High Viscosity | PC Low Viscosity | Unit | Difference |
| General Information | ||||
| Designation | High Viscosity, Unfilled, Molding and Extrusion | Low Viscosity, Unfilled, Molding and Extrusion | — | Grade designation differs |
| Compositional note | Higher molecular weight; less processable but more tough | Lower molecular weight; more processable but less tough | — | High-visc = tougher/less processable; Low-visc = more processable/less tough |
| Material family | Plastic (thermoplastic, amorphous) | Plastic (thermoplastic, amorphous) | — | Identical |
| Base material | PC (Polycarbonate) | PC (Polycarbonate) | — | Identical |
| Polymer code | PC | PC | — | Identical |
| Polymer content | 100 | 100 | % | Identical |
| Physical Properties | ||||
| Density | 1.19 – 1.21 | 1.19 – 1.21 | g/cm³ | Identical |
| Mechanical Properties | ||||
| Young’s modulus | 2.32 – 2.44 | 2.32 – 2.44 | GPa | Identical |
| Specific stiffness | 1.93 – 2.04 | 1.93 – 2.04 | MN.m/kg | Identical |
| Yield strength (elastic limit) | 59.1 – 65.2 | 59.1 – 65.2 | MPa | Identical |
| Tensile strength | 62.7 – 72.4 | 62.7 – 72.4 | MPa | Identical |
| Specific strength | 49.2 – 54.4 | 49.2 – 54.4 | kN.m/kg | Identical |
| Elongation | 110 – 120 | 110 – 150 | % strain | Low visc. has higher max elongation (up to 150 vs 120) |
| Compressive modulus | 2.35 – 2.47 | 2.35 – 2.47 | GPa | Identical |
| Compressive strength | 69 – 86.2 | 69 – 86.2 | MPa | Identical |
| Flexural modulus | 2.27 – 2.34 | 2.27 – 2.34 | GPa | Identical |
| Flexural strength (modulus of rupture) | 86.2 – 93.1 | 82.7 – 96.5 | MPa | Low visc. range is wider (lower min, higher max) |
| Shear modulus | 0.829 – 0.872 | 0.829 – 0.872 | GPa | Identical |
| Bulk modulus | 3.83 – 4.03 | 3.83 – 4.03 | GPa | Identical |
| Poisson’s ratio | 0.391 – 0.407 | 0.391 – 0.407 | — | Identical |
| Shape factor | 4.6 | 4.6 | — | Identical |
| Hardness – Vickers | 18 – 20 | 18 – 20 | HV | Identical |
| Hardness – Rockwell M | 70 – 75 | 70 – 75 | — | Identical |
| Hardness – Rockwell R | 104 – 115 | 104 – 115 | — | Identical |
| Elastic stored energy (springs) | 734 – 894 | 734 – 894 | kJ/m³ | Identical |
| Fatigue strength at 10^7 cycles | 23.7 – 30.8 | 23.7 – 30.8 | MPa | Identical |
| Impact & Fracture Properties | ||||
| Fracture toughness | 2.1 – 2.3 | 2.1 – 2.3 | MPa.m^0.5 | Identical |
| Toughness (G) | 1.85 – 2.23 | 1.85 – 2.23 | kJ/m² | Identical |
| Impact strength, notched, 23 °C | 69.7 – 102 | 10.1 – 83.1 | kJ/m² | High visc. is notably tougher (min 69.7 vs 10.1) |
| Impact strength, notched, -30 °C | 12.6 – 15 | 5.65 – 23.3 | kJ/m² | Low visc. has a much wider/lower range at min |
| Impact strength, unnotched, 23 °C | 590 – 600 | 188 – 226 | kJ/m² | High visc. is dramatically tougher (~3x higher) |
| Impact strength, unnotched, -30 °C | 590 – 600 | 183 – 220 | kJ/m² | High visc. is dramatically tougher (~3x higher) |
| Thermal Properties | ||||
| Glass temperature | 142 – 158 | 142 – 158 | °C | Identical |
| Heat deflection temperature, 0.45 MPa | 138 – 142 | 134 – 138 | °C | High visc. slightly higher |
| Heat deflection temperature, 1.8 MPa | 121 – 132 | 121 – 132 | °C | Identical |
| Maximum service temperature | 104 – 119 | 101 – 116 | °C | High visc. slightly higher |
| Minimum service temperature | -47 – -37 | -47 – -37 | °C | Identical |
| Thermal conductivity | 0.189 – 0.205 | 0.193 – 0.218 | W/m.°C | Low visc. slightly higher |
| Specific heat capacity | 1150 – 1250 | 1150 – 1250 | J/kg.°C | Identical |
| Thermal expansion coefficient | 120 – 125 | 120 – 125 | µstrain/°C | Identical |
| Thermal shock resistance | 201 – 226 | 201 – 226 | °C | Identical |
| Thermal distortion resistance | 0.00154 – 0.00168 | 0.00157 – 0.00179 | MW/m | Low visc. slightly higher |
| Electrical Properties | ||||
| Electrical resistivity | 1e20 – 1e21 | 1e20 – 1e21 | µohm.cm | Identical |
| Electrical conductivity | 1.72e-19 – 1.72e-18 | 1.72e-19 – 1.72e-18 | %IACS | Identical |
| Dielectric constant (relative permittivity) | 3.1 – 3.3 | 3.1 – 3.3 | — | Identical |
| Dissipation factor (dielectric loss tangent) | 8.6e-4 – 9.4e-4 | 8.6e-4 – 9.4e-4 | — | Identical |
| Dielectric strength (dielectric breakdown) | 16 – 19.2 | 16 – 19.2 | MV/m | Identical |
| Comparative tracking index | 175 – 325 | 175 – 325 | V | Identical |
| Magnetic Properties | ||||
| Magnetic type | Non-magnetic | Non-magnetic | — | Identical |
| Optical, Aesthetic & Acoustic Properties | ||||
| Refractive index | 1.58 – 1.59 | 1.58 – 1.59 | — | Identical |
| Transparency | Optical quality | Optical quality | — | Identical |
| Acoustic velocity | 1.39e3 – 1.43e3 | 1.39e3 – 1.43e3 | m/s | Identical |
| Mechanical loss coefficient (tan delta) | 0.0164 – 0.0172 | 0.0164 – 0.0172 | — | Identical |
| Critical Materials Risk | ||||
| Contains >5wt% critical elements? | No | No | — | Identical |
| Absorption & Permeability | ||||
| Water absorption @ 24 hrs | 0.135 – 0.165 | 0.135 – 0.165 | % | Identical |
| Water vapor transmission | 1.1 – 2.05 | 1.1 – 2.05 | g.mm/m².day | Identical |
| Permeability (O2) | 91.6 – 105 | 91.6 – 105 | cm³.mm/m².day.atm | Identical |
| Processing Properties | ||||
| Polymer injection molding | Excellent | Acceptable | — | High visc. rated better for injection molding |
| Polymer extrusion | Acceptable | Acceptable | — | Identical |
| Polymer thermoforming | Excellent | Excellent | — | Identical |
| Linear mold shrinkage | 0.5 – 0.7 | 0.5 – 0.7 | % | Identical |
| Melt temperature | 226 – 322 | 205 – 298 | °C | High visc. requires higher melt temperature |
| Mold temperature | 70 – 100 | 70 – 100 | °C | Identical |
| Molding pressure range | 69 – 138 | 55 – 103 | MPa | High visc. requires higher molding pressure |
| Durability | ||||
| Water (fresh) | Excellent | Excellent | — | Identical |
| Water (salt) | Excellent | Excellent | — | Identical |
| Weak acids | Excellent | Excellent | — | Identical |
| Strong acids | Excellent | Excellent | — | Identical |
| Weak alkalis | Acceptable | Acceptable | — | Identical |
| Strong alkalis | Unacceptable | Unacceptable | — | Identical |
| Organic solvents | Limited use | Limited use | — | Identical |
| Oxidation at 500 °C | Unacceptable | Unacceptable | — | Identical |
| UV radiation (sunlight) | Fair | Fair | — | Identical |
| Flammability | Slow-burning | Slow-burning | — | Identical |
| Primary Production Energy, CO2 & Water | ||||
| Embodied energy, primary production | 100 – 111 | 100 – 111 | MJ/kg | Identical |
| CO2 footprint, primary production | 4.53 – 4.99 | 4.53 – 4.99 | kg/kg | Identical |
| Water usage | 165 – 182 | 165 – 182 | l/kg | Identical |
| Processing Energy, CO2 Footprint & Water | ||||
| Polymer extrusion energy | 5.82 – 6.43 | 5.78 – 6.39 | MJ/kg | High visc. marginally higher |
| Polymer extrusion CO2 | 0.437 – 0.483 | 0.434 – 0.48 | kg/kg | High visc. marginally higher |
| Polymer extrusion water | 4.83 – 7.24 | 4.81 – 7.22 | l/kg | High visc. marginally higher |
| Polymer molding energy | 18.7 – 20.6 | 17.6 – 19.5 | MJ/kg | High visc. higher |
| Polymer molding CO2 | 1.4 – 1.55 | 1.32 – 1.46 | kg/kg | High visc. higher |
| Polymer molding water | 12.6 – 18.9 | 12.2 – 18.2 | l/kg | High visc. higher |
| Coarse machining energy (per unit wt removed) | 1.09 – 1.2 | 1.09 – 1.2 | MJ/kg | Identical |
| Coarse machining CO2 (per unit wt removed) | 0.0814 – 0.09 | 0.0814 – 0.09 | kg/kg | Identical |
| Fine machining energy (per unit wt removed) | 6.58 – 7.27 | 6.58 – 7.27 | MJ/kg | Identical |
| Fine machining CO2 (per unit wt removed) | 0.494 – 0.546 | 0.494 – 0.546 | kg/kg | Identical |
| Grinding energy (per unit wt removed) | 12.7 – 14 | 12.7 – 14 | MJ/kg | Identical |
| Grinding CO2 (per unit wt removed) | 0.951 – 1.05 | 0.951 – 1.05 | kg/kg | Identical |
| Recycling & End of Life | ||||
| Recycle | Yes | Yes | — | Identical |
| Embodied energy, recycling | 35 – 38.7 | 35 – 38.7 | MJ/kg | Identical |
| CO2 footprint, recycling | 2.32 – 2.56 | 2.32 – 2.56 | kg/kg | Identical |
| Recycle fraction in current supply | 0.672 – 0.742 | 0.672 – 0.742 | % | Identical |
| Downcycle | Yes | Yes | — | Identical |
| Combust for energy recovery | Yes | Yes | — | Identical |
| Heat of combustion (net) | 30.3 – 31.8 | 30.3 – 31.8 | MJ/kg | Identical |
| Combustion CO2 | 2.7 – 2.84 | 2.7 – 2.84 | kg/kg | Identical |
| Landfill | Yes | Yes | — | Identical |
| Biodegrade | No | No | — | Identical |