Reading A Polycarbonate Abs Datasheet The Ratio Behind The Trade Name
Reading a Polycarbonate/ABS Datasheet: The Ratio Behind the Trade Name requires treating the commercial grade designation as an identifier, not as a composition statement. A product family may use one trade name for a 50 wt% polycarbonate grade and a 70 wt% polycarbonate grade, with only the tested property profile disclosing the difference. The ratio is not routinely printed as a mass fraction on the first page of a technical data sheet. It must be reconstructed from density, thermal resistance, melt volume-flow rate, tensile response, and impact data, all read together. A single datasheet line cannot carry the formulation because additives, fillers, impact modifiers, and flame retardants shift individual values independently.
The first inspection points are the material marking and the test standard. ISO 11469 may identify the material as PC+ABS, but that marking does not state the ratio. Density is reported under ISO 1183-1. Vicat softening temperature is reported under ISO 306/B50. Heat deflection temperature is determined under ISO 75-1/-2 at 1.8 MPa. Tensile yield stress and tensile modulus are determined under ISO 527-2/1A/50 and ISO 527-2/1A/1. When a datasheet omits the specimen type, test speed, temperature, or conditioning protocol, the printed value cannot be used to bracket the ratio.
What Does the Density and Vicat Pairing Actually Quantify?
Bisphenol A polycarbonate homopolymer has a density near 1.20 g/cm³ when measured to ISO 1183-1. General-purpose ABS grades fall between 1.04 g/cm³ and 1.07 g/cm³. A PC/ABS grade reported at 1.15 g/cm³ therefore implies a PC mass fraction near 0.65 if the formulation contains no mineral filler, no heavy flame-retardant system, and negligible pigment loading. A reported density of 1.13 g/cm³ is more consistent with a 50 wt% PC grade. The relationship is approximately linear for binary blends, but only after correction for non-polymeric additives. Mineral-filled PC/ABS can exceed 1.25 g/cm³, at which point density no longer tracks the PC/ABS ratio alone.
Vicat B50 provides a cross-check. Homopolymer PC commonly exhibits Vicat B50 values between 145 °C and 150 °C. General-purpose ABS commonly exhibits Vicat B50 near 100 °C. Commercial PC/ABS grades for electronics housings and interior automotive components typically fall between 120 °C and 135 °C. Heat deflection temperature under 1.8 MPa follows a similar trend, but the correlation is less smooth because HDT is sensitive to molded-in stress, orientation, and thickness. The ratio is better bracketed by density plus Vicat than by heat deflection temperature alone.
Differential scanning calorimetry according to ISO 11357-2 can also reveal the two-phase structure. A PC/ABS blend typically shows a styrene-acrylonitrile-rich glass transition near 105 °C and a PC-rich glass transition near 147 °C. The step heights and midpoint temperatures vary with composition, but direct quantification is confounded by partial miscibility and the composition of the SAN phase. If the datasheet includes DSC data, the two glass transitions are more diagnostic than a single Vicat value.
| Property and test method | PC homopolymer | PC/ABS 70/30 representative range | PC/ABS 50/50 representative range | ABS general-purpose |
|---|---|---|---|---|
| Density, ISO 1183-1 | 1.20 g/cm³ | 1.15–1.17 g/cm³ | 1.12–1.14 g/cm³ | 1.04–1.07 g/cm³ |
| Tensile yield stress, ISO 527-2/1A/50 | 63–70 MPa | 55–60 MPa | 48–52 MPa | 40–50 MPa |
| Tensile modulus, ISO 527-2/1A/1 | 2300–2500 MPa | 2200–2400 MPa | 2000–2200 MPa | 2000–2400 MPa |
| Flexural modulus, ISO 178 | 2300–2400 MPa | 2200–2400 MPa | 2000–2200 MPa | 1900–2300 MPa |
| HDT/A, 1.8 MPa, ISO 75-1/-2 | 124–130 °C | 112–120 °C | 100–108 °C | 92–98 °C |
| Vicat B50, ISO 306 | 145–150 °C | 130–138 °C | 122–128 °C | 98–105 °C |
The representative ranges above apply to unfilled, general-purpose grades. Flame-retardant, impact-modified, or mineral-filled materials can fall outside them, and the datasheet must be checked for those modifying systems before the ratio is estimated.
Commercial PC/ABS compounds are produced on co-rotating twin-screw extruders with L/D 36:1 to 44:1 and side feeding of the ABS or SAN phase. On such equipment, the polycarbonate fraction controls the melt pressure at a given screw speed and throughput. A 70/30 PC/ABS grade requires a higher barrel set point and generates higher specific mechanical energy than a 50/50 grade. Melt temperature at the die is maintained between 260 °C and 280 °C for most PC/ABS formulations. If the melt temperature exceeds 300 °C, the butadiene phase of the ABS begins to degrade, producing surface defects and free butadiene odor. If the die temperature is below 250 °C, high-PC grades show insufficient melt homogenization and visible weld lines.
Drying is a second process variable that responds to the ratio. Polycarbonate hydrolyzes during melt processing when residual moisture exceeds 0.02 wt%. ABS absorbs moisture more slowly, and a PC/ABS blend with higher ABS content can tolerate slightly higher residual moisture than polycarbonate homopolymer. Desiccant dryers with a dew point of −40 °C and inlet air temperature of 80 °C to 100 °C are used for PC/ABS, with residence time of 2 h to 4 h. The exact drying condition is grade-specific and should be taken from the supplier because the ABS rubber phase can agglomerate if the drying temperature is set too high.
| Material | Pre-drying condition | Residual moisture limit | Melt temperature range | Mold temperature range |
|---|---|---|---|---|
| PC homopolymer | 120 °C, 3–4 h, desiccant dryer −40 °C dew point | 0.02 wt% | 280–320 °C | 80–100 °C |
| PC/ABS 70/30 | 80–100 °C, 2–4 h | 0.02 wt% | 260–280 °C | 60–80 °C |
| PC/ABS 50/50 | 80–100 °C, 2–3 h | 0.02 wt% | 250–270 °C | 60–80 °C |
| ABS general-purpose | 80 °C, 2–3 h | 0.1 wt% | 220–250 °C | 40–70 °C |
When the Datasheet Lists Melt Volume-Flow Rate at 260 °C/5 kg
A melt volume-flow rate report without its test condition is ambiguous. PC/ABS grades are often characterized at 260 °C with a 5.0 kg load according to ISO 1133-1. Homopolymer PC grades are often characterized at 300 °C with a 1.2 kg load because polycarbonate has a higher glass transition and higher melt viscosity. A value of 12 cm³/10 min at 260 °C/5.0 kg cannot be compared directly with a value of 10 cm³/10 min at 300 °C/1.2 kg. For a fixed test condition, increasing the ABS content raises the MVR. A 50/50 PC/ABS grade may show an MVR in the range of 15 to 25 cm³/10 min at 260 °C/5.0 kg, while a 70/30 grade may show 8 to 15 cm³/10 min under the same condition. These ranges are indicative and are altered by flame retardants, impact modifiers, and mold release agents.
The flow path length in an injection mold is a more operationally useful measure. A PC/ABS grade with an MVR above 20 cm³/10 min at 260 °C/5.0 kg generally fills a 2 mm-thick section at a lower injection pressure than a PC-rich grade with an MVR below 10 cm³/10 min. The machine clamping force required to prevent flash therefore changes with the ratio. A 70/30 PC/ABS part may require a clamp force of 5.0 kN/cm² of projected area, while a 50/50 grade can often be processed at 3.5 to 4.5 kN/cm² in similar tool configurations. Published values vary with mold design, gate size, and wall thickness.
Flame Retardant Phosphorus Chemistry and the Ratio Masking Effect
Flame-retardant PC/ABS grades disrupt the density–Vicat–PC-content correlation. Non-halogenated phosphate esters such as resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate) are used to achieve UL 94 V-0 at 1.5 mm. These additives can contribute phosphorus contents of 1.0 wt% to 3.5 wt% and may lower the Vicat B50 temperature by 10 °C to 20 °C relative to the same unfilled PC/ABS matrix. They can also raise the density. Consequently, a flame-retardant PC/ABS with a high PC fraction may present the density of a 50/50 general-purpose grade and the Vicat of a lower-PC unfilled grade. The datasheet should be checked for the UL 94 yellow card, the specimen thickness, and the flame-retardant system before density is used to infer composition.
Glow wire ignition temperature according to IEC 60695-2-12 is frequently reported for electrical appliance housings. A PC/ABS grade with high PC content and a volatile phosphorus additive may pass 850 °C glow wire but exhibit increased mold deposit formation. The ratio of PC to ABS also influences the migration of phosphate esters to the surface, which modifies paint adhesion, printability, and contact compatibility. Data sheets rarely list additive concentrations. The ratio behind the trade name must therefore be bracketed using density, thermal, flammability, and processing data together, not through the trade name alone.
For unfilled grades, tensile yield stress measured to ISO 527-2/1A/50 remains one of the more monotonic indicators of PC content. Homopolymer PC typically shows a yield stress of 63 MPa to 70 MPa, while general-purpose ABS shows 40 MPa to 50 MPa. PC/ABS grades appear in the intermediate range. A 70/30 PC/ABS grade is commonly quoted at 55 MPa to 60 MPa, and a 50/50 grade at 48 MPa to 52 MPa. The same trend appears in tensile modulus, but the butadiene rubber content of the ABS phase and any added impact modifier can lower stiffness independently of the PC/ABS ratio. Flexural modulus measured to ISO 178 at 2 mm/min is similarly affected by orientation in the injection-molded specimen.
Moisture conditioning introduces a second correction. PC and ABS absorb water at different rates. A PC/ABS plaque conditioned to equilibrium at 23 °C and 50% RH may reach a moisture content of 0.2 wt% to 0.4 wt%, depending on the ABS fraction and filler content. This moisture level can reduce the glass transition temperature of the PC phase as measured by differential scanning calorimetry according to ISO 11357-2 and can lower melt flow stability if the material is not dried before processing. Conditioned tensile tests are sometimes reported as part of a datasheet but are less standardized than dry-as-molded values. Published data for moisture-conditioned PC/ABS across multiple commercial ratio grades is limited; the datasheet should state whether conditioning followed ISO 1110 or an internal supplier protocol.
Mold shrinkage measured according to ISO 294-4, after 24 h at 23 °C, is another datasheet line that responds weakly to the ratio because PC and ABS shrinkage ranges overlap. PC homopolymer shrinkage is commonly 0.5% to 0.7%; ABS shrinkage is also 0.4% to 0.7%. PC/ABS grades therefore show similar shrinkage. The coefficient of linear thermal expansion, determined by ISO 11359-2, separates the materials more clearly: PC is approximately 65 × 10⁻⁶ K⁻¹, ABS is approximately 80 × 10⁻⁶ K⁻¹ to 90 × 10⁻⁶ K⁻¹, and PC/ABS often falls near 70 × 10⁻⁶ K⁻¹ to 80 × 10⁻⁶ K⁻¹. These values are influenced by filler and orientation. The datasheet should be checked for whether the coefficient was measured in the flow direction or cross-flow direction because the difference can exceed 10 × 10⁻⁶ K⁻¹ in asymmetric molded parts.
Why Notched Charpy Energy Cannot Be Used Alone to Determine the Blend Ratio
Charpy notched impact strength measured according to ISO 179-1/1eA is reported on almost every PC/ABS datasheet, but it is not a reliable standalone ratio indicator. The value depends on the ABS phase rubber particle size, the styrene-acrylonitrile graft shell, the butadiene content, and the presence of core-shell impact modifiers or silicone-acrylic modifiers. A 50/50 PC/ABS with a well-dispersed high-rubber ABS phase may show higher Charpy notched impact at 23 °C than a 70/30 PC/ABS using a low-rubber ABS. At −30 °C, the ductile-to-brittle transition can invert the ranking. A datasheet value of 45 kJ/m² at 23 °C does not identify the PC content without the accompanying rubber morphology and temperature condition.
When a datasheet reports impact only at room temperature, the PC content remains ambiguous. The more diagnostic use of Charpy data is the ratio of 23 °C to −30 °C values. PC-rich grades with sufficient ABS rubber retain a smaller percentage of their room-temperature impact at low temperature, while brittle, low-PC, or degraded grades show a sharper decline. This ratio is still matrix- and modifier-dependent. The datasheet should be read together with the flexural modulus, Vicat, and density to bracket the blend ratio.
Solvent crazing data provides another ratio-sensitive signature. Polycarbonate has poor resistance to ketones, aromatic hydrocarbons, and strong bases, while ABS is attacked by esters and ketones but may be less sensitive to some aliphatic hydrocarbons. In PC/ABS, the PC-rich surface tends to control environmental stress-cracking resistance. Exposure to a 50% toluene/50% heptane mixture under 0.5% flexural strain, evaluated according to ISO 22088-3, can produce crazes earlier in a high-PC grade than in a high-ABS grade, but published standardized data for such specific configurations is limited. Chemical resistance tables on PC/ABS datasheets are therefore grade-specific and cannot be extrapolated across the trade-name family.
Ultraviolet stability and weathering data follow similar constraints. Polycarbonate yellows and loses impact under UV when unprotected, while ABS is more sensitive to photo-oxidation. PC/ABS datasheets may report accelerated weathering to ISO 4892-2 or ASTM D2565. A higher PC fraction generally gives better color retention, but the UV stabilizer package dominates the response. The ratio cannot be read from weathering data alone.
