Guangdong Wanhan PC/ABS 2500A is an unfilled polycarbonate/acrylonitrile-butadiene-styrene alloy supplied in pellet form for injection moulding and for selected extrusion compounding operations. The product is classified within the 2500-series as a general-purpose grade: the polycarbonate phase contributes heat resistance and impact strength, while the styrene-acrylonitrile-grafted butadiene phase contributes melt processability and reduced notch sensitivity. The grade is differentiated from flame-retarded, plated, glass-fibre-reinforced, and high-flow PC/ABS products by the absence of halogenated or phosphorous flame-retardant packages and by a nominal melt volume-flow rate that falls below that of thin-wall grades. Published data for this specific configuration is limited to supplier datasheet values and lot-specific certificates of analysis; independent inter-laboratory data under ISO 10350-1:2017 are not widely available. When 2500A is evaluated on production-scale equipment, the three primary batch-control variables are melt volume-flow rate, retained moisture, and weld-line strength retention in unannealed mouldings.

What separates 2500A from higher-flow PC/ABS grades in thin-wall moulding?

The nominal melt volume-flow rate of 2500A at 260 °C and 5 kg load is reported within 12–18 cm³/10 min according to ISO 1133-1:2022. Grades intended for housings with wall thickness below 1.0 mm may use flow rates above 25 cm³/10 min; those grades fill at lower clamp force but sacrifice notched Izod impact and chemical resistance. Processing of 2500A on a 450 t toggle-clamp injection moulding machine with a 28 mm diameter, 20:1 L/D reciprocating screw has been documented at barrel temperatures of 240 °C/255 °C/265 °C from feed to metering, nozzle temperature 260 °C, mould temperature 60–80 °C, holding pressure 45 MPa, and injection speed 80 mm/s. A 2.0 mm thick housing with a flow length of 240 mm filled under these conditions without short shots. Reducing wall thickness to 1.0 mm at the same flow length required injection pressure above 130 MPa and produced a weld line with notched Izod impact of 18 kJ/m² compared with 52 kJ/m² in the un-welded bulk. This reduction is a function of flow-front cooling and is not specific to 2500A, but it demonstrates that the flow grade must be selected relative to the most restrictive wall section rather than the average wall thickness.

Moisture is the most common cause of process instability with PC/ABS 2500A. The material requires pre-drying to 0.02% moisture by weight before melt processing. A desiccant dryer with a dew point of -40 °C or lower, an inlet air temperature of 80–90 °C, and a residence time of 3–4 h is normally sufficient. At ambient relative humidity above 60%, drying time is extended to 4 h or more, and open material hoppers are blanketed with dried air. On a 75 kg/h throughput hopper dryer, intermittent bridging at the inlet cone allowed undried pellets to enter the barrel at 0.06% moisture; hydrolysis of the polycarbonate phase reduced notched Izod impact from 48 kJ/m² to 22 kJ/m² and produced silver streaks that did not respond to barrel temperature adjustment. The failure is prevented by routine dew-point alarm checks and by replacing desiccant bags at intervals not exceeding the dryer manufacturer’s recommendation.

Thermal, mechanical, and flammability data under ISO and ASTM protocols

The values in the table are supplier-nominal and are not guaranteed minima. Lot-specific certificates of analysis may vary by ±10% for melt flow and ±15% for impact. For design calculations, the lower-bound notched Izod impact at -30 °C is used when snap-fit deflections exceed 0.8 mm during assembly. In instrumented puncture tests according to ISO 6603-2:2000, unfilled PC/ABS plaques at 2.0 mm thickness exhibit a peak force of 3.8–4.5 kN and total energy of 35–45 J at 23 °C, but the energy drops below 10 J when plaques are moulded with wet resin or with regrind above 25% by weight. For applications requiring V-0 behaviour at 1.6 mm, 2500A in unfilled form is not suitable; a flame-retarded PC/ABS grade or an additive package is required.

Compared with a general-purpose ABS, PC/ABS 2500A offers heat deflection temperature approximately 20–30 °C higher and notched Izod impact approximately 2–3 times higher, but at a density penalty of approximately 0.08–0.12 g/cm³ and higher drying cost. Compared with an unfilled polycarbonate homopolymer of equivalent melt flow, 2500A shows lower notched Izod impact at 23 °C but higher melt flow and substantially better resistance to stress cracking in fatty acid or alcohol exposure. Compared with a glass-fibre-reinforced PC/ABS, 2500A has lower flexural modulus by roughly 50–60% but avoids the anisotropic shrinkage and surface roughness that fibre orientation produces in thin ribs. A mineral-filled PC/ABS may reduce mould shrinkage anisotropy, but at the expense of surface gloss and weld-line strength. The 2500A grade remains in the unfilled, general-purpose category and is typically selected over ABS-only resins when heat deflection temperature above 90 °C is required and over PC-only resins when flow length and stress-cracking resistance are more important than optical clarity. Differentiation from 2500B or 2500C, if present in the supplier range, generally concerns melt flow and impact balance; published data for this specific configuration is limited and is confirmed through first-article inspection under ISO 294-1.

Mould temperature, gate geometry, and venting determine weld-line strength in unfilled alloys

Melt temperature at the nozzle of 260–280 °C and mould temperature of 60–80 °C are typical for 2500A. At mould temperatures below 50 °C, the elongated polycarbonate phase freezes before molecular relaxation, increasing frozen-in stress and reducing weld-line strength. In a split-flow mould with a central obstruction, raising mould temperature from 40 °C to 70 °C increased weld-line tensile strength from 25 MPa to 38 MPa, with fracture surface analysis showing enhanced interdiffusion across the melt front. Gate design avoids jetting; direct needle gates on flat surfaces produce jetting if the gate diameter is below 1.0 mm and injection speed exceeds 80 mm/s. Spiral or tab gates with land length 1.5–2.0 mm and gate thickness 50–70% of wall thickness produce laminar filling. Venting depth for PC/ABS does not exceed 0.02–0.04 mm at the parting line to avoid flash while allowing gas escape; burn marks at end-of-fill locations are typically caused by vent depth below 0.015 mm or insufficient vent land length. Hot runner manifold temperatures of 250–270 °C are used, but dead spots above 280 °C produce yellowing and polymer degradation.

At processing melt temperatures, 2500A exhibits shear-thinning behaviour. Apparent viscosity at 100 s⁻¹ is approximately 300–500 Pa·s, falling to 100–150 Pa·s at 1000 s⁻¹ when measured by capillary rheometry according to ISO 11443:2021. The power-law index over the 100–1000 s⁻¹ range is typically 0.35–0.45. This pseudo-plastic response means that raising injection speed from 10 mm/s to 80 mm/s may reduce pressure drop less than a Newtonian assumption predicts; however, shear heating becomes significant in small sprues and gates, and local melt temperature can exceed the barrel set point by 15–30 °C.

When environmental stress cracking, paintability, and dimensional stability determine the specification

Environmental stress cracking resistance of PC/ABS 2500A under controlled strain is evaluated using ISO 22088-2:2006 or ISO 22088-3:2006. In a comparative batch evaluation at 1.0% external fibre strain, unfilled PC homopolymer exposed to isopropanol for 24 h developed visible crazing, while 2500A retained a notched Izod impact retention above 85% relative to the unexposed control. This resistance is used in automotive interior components that contact hand creams, isopropanol-based cleaners, or plasticizer migration from PVC foam. The improvement does not extend to aromatic hydrocarbon exposure; immersion in toluene or xylene swells the SAN phase, and tensile elongation at break can fall below 5% within 24 h. Paint adhesion on moulded surfaces following flame or corona pretreatment is tested by DIN EN ISO 2409 cross-cut. Classification of 0–1 is achieved on surfaces with gloss below 70 GU and with no external mould release. Internal mould release migration can reduce paint adhesion if ejection speeds are high and mould cooling is uneven.

Linear mould shrinkage is anisotropic and depends on flow direction. Values of 0.5–0.7% parallel to flow and 0.4–0.6% perpendicular to flow are typical for 2.0 mm plaques moulded according to ISO 294-4:2018. Post-mould shrinkage at 72 h and 23 °C adds 0.05–0.10% to both axes, while moisture absorption of 0.15–0.25% after 50% relative humidity conditioning may expand dimensions by 0.05–0.15% depending on packing pressure and mould restraint. Tight dimensional specifications below ±0.05 mm require a controlled conditioning protocol before metrology.

The allowable regrind fraction for PC/ABS 2500A is limited by cumulative thermal history and chain scission. Reprocessing at barrel temperatures of 260–280 °C causes hydrolysis of the polycarbonate phase and oxidative degradation of the butadiene phase. In a production trial using a 50 t machine and 100% regrind, melt volume-flow rate increased from 15 cm³/10 min to 21 cm³/10 min after three cycles, while notched Izod impact decreased from 50 kJ/m² to 29 kJ/m². At 20% regrind mixed with virgin pellets, the impact loss was below 10%, which is often acceptable. At 40% regrind, the impact loss exceeded 25% and surface streaking appeared. Processing instructions for 2500A therefore typically limit regrind to 20% by weight unless the application is non-structural and impact requirements are low. The degradation mechanism is heat history rather than particle size; regrind particle size below 4 mm does not alter melt plastication if the screw has a compression ratio of 2.2:1 or higher.

Snap-fit arms moulded from 2500A fail in a ductile manner at room temperature but transition to brittle fracture at sub-zero temperatures or in the presence of weld lines. The notch sensitivity factor, defined as the ratio of notched to unnotched Izod impact, is higher than polycarbonate but lower than ABS. Designers use radii of at least 0.5 mm at the base of snap-fit features; sharp radii below 0.2 mm create stress concentrations and premature failure. In cyclic loading, the fatigue endurance limit of unfilled PC/ABS is approximately 30–40% of the tensile yield stress at 10⁴ cycles, but weld lines and chemical exposure lower this limit.

Under EU Directive 2011/65/EU and Commission Delegated Directive (EU) 2015/863 (RoHS), 2500A as supplied does not intentionally contain lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, or polybrominated diphenyl ethers above maximum concentration values. Under Regulation (EC) No 1907/2006 (REACH), the supplier’s safety data sheet is checked for substances of very high concern above 0.1% w/w. For food-contact use, compliance with Commission Regulation (EU) No 10/2011 is not automatically implied; the polycarbonate phase can release bisphenol A residues, and migration testing under the intended food simulant is required. For electrical and electronic equipment, UL 94 HB classification at 1.6 mm means that 2500A alone does not meet V-0 requirements unless flame-retardant additives are incorporated by the converter.