Nanjing Lihua ABS S704 is an acrylonitrile-butadiene-styrene copolymer supplied in pellet form for injection moulding and extrusion conversion. The resin is manufactured by grafting styrene-acrylonitrile copolymer onto polybutadiene latex, producing a two-phase morphology in which rubber particles on the order of 0.1–1.0 µm are dispersed within a continuous SAN matrix. This structure provides the balance of impact strength, rigidity and melt flow that positions S704 in the medium-impact ABS segment under ISO 19069-2:2016. The grade is normally natural or off-white, with bulk density in the range of 0.55–0.65 g/cm³ when measured by ISO 60:2023. Lot-specific values for melt flow rate, impact energy and heat distortion must be read from the supplier certificate of analysis because the designation S704 does not by itself encode the complete ISO data block.

Specification envelope of Nanjing Lihua ABS S704 under ISO 19069-2 designation

The manufacturer’s certificate of analysis remains the controlling document for lot release. For preliminary engineering calculations, the designatory property range associated with this grade class is shown in the following table. Values are representative of medium-impact ABS resins and are not a substitute for supplier-certified data for S704. Each method designation corresponds to the current ISO or UL test protocol used in commercial specifications.

Why must pellet moisture be kept below 0.02% before melt processing?

Moisture uptake in ABS pellets equilibrates with ambient relative humidity, particularly above 60 % RH. Although ABS is not hydrolytically sensitive to the same degree as polycarbonate or polyamide, residual surface and interstitial moisture generates splay, flow marks and loss of gloss during melt processing. Desiccant drying at 80 °C for 2–4 h is required to achieve a moisture content of ≤0.02 % by mass as determined by ISO 15512:2019. Dryer dew point should be held between -30 °C and -40 °C. On production-scale injection moulding machines with hydraulic clamp force of 1200 kN and screw diameter of 40 mm, barrel temperatures from rear to nozzle are typically 210 °C, 225 °C, 235 °C and 230 °C. Back pressure is maintained at 0.5–1.0 MPa and shot size is held between 50 % and 70 % of barrel capacity. Mould temperature is controlled at 40–60 °C; lower mould temperatures reduce cycle time but increase weld-line visibility and frozen-in orientation.

On single-screw extruders with screw diameters of 60–90 mm and L/D ratios between 24:1 and 30:1, S704 is processed for sheet and profile with melt temperatures of 230–250 °C. Die temperature is set at 230 °C and chill roll temperatures are maintained at 60–90 °C for sheet thicknesses between 1.5 mm and 6.0 mm. The extruder screw should use a moderate compression ratio of 2.5:1 to 3.0:1 and a barrier section to limit shear heating. Because S704 has a medium-high melt viscosity relative to high-flow ABS, melt pressure before breaker plate commonly reaches 10–18 MPa depending on throughput and die restriction. Published data for this specific configuration is limited where narrow die gap below 1.0 mm is used at line speeds above 15 m/min; process trials are recommended before fixed production commitments.

When S704 replaces high-flow ABS in thin-wall injection moulding

Thin-wall parts below 1.2 mm nominal wall thickness expose the melt-flow limitations of S704 relative to high-flow ABS grades with melt mass-flow rates of 20–30 g/10 min at 220 °C/10 kg. S704, with a melt mass-flow rate of 4–6 g/10 min under ISO 1133-1:2022, requires higher cavity pressure and longer filling time. Cavity pressure measured by piezo-electric transducers should be kept below 80–120 MPa to avoid flash and core deflection. Injection speed profiles must compensate for the higher viscosity; a fill time of 0.8–1.5 s is typical for 2.0 mm wall sections, but flow length-to-thickness ratios above 150:1 may produce short shots. Compared with high-flow ABS, S704 offers improved notched impact and higher melt strength, which is advantageous in thermoforming and thick-wall components, but it is not the preferred choice for high-cavitation thin-wall connectors or caps requiring fast cycle times below 8 s.

Benchmarking the S704 property profile against high-heat ABS and PC/ABS

The property profile of S704 is best interpreted against high-heat ABS and PC/ABS. High-heat ABS grades with α-methylstyrene comonomer raise the Vicat softening temperature into the 105–115 °C range under ISO 306:2022, but reduce melt flow. S704 remains easier to process because its Vicat softening temperature of 96–100 °C is paired with a melt mass-flow rate of 4–6 g/10 min. PC/ABS blends exhibit Charpy notched impact values of 45–60 kJ/m² under ISO 179-1/1eA:2020 and higher heat resistance, but density increases to 1.12–1.14 g/cm³ and resistance to aromatic hydrocarbons and certain cosmetic chemicals may decrease. S704 provides a lower-density, lower-cost alternative where continuous service temperature does not exceed 75–85 °C and where impact requirements fall within the 18–22 kJ/m² Charpy notched window.

Operational limits on hot-runner residence time and regrind

Hot-runner systems with valve-gate sequencing impose a maximum melt residence time of 8–10 min at 240 °C before yellowness index shifts by more than 2 units under ASTM E313-20. Extended residence time degrades the polybutadiene phase, reducing impact strength and producing brown specks. Screw-recovery delay should not exceed 30 s when barrel temperature is above 240 °C. Regrind from sprues and runners may be added at ≤25 % by mass without significant shift in tensile yield stress, but repeated heat histories should be limited to 3 cycles. The use of hot-air hopper dryers is not recommended when ambient relative humidity exceeds 60 % RH; desiccant drying is required. Avoid combination of S704 with amine-based color concentrates that accelerate thermo-oxidative degradation at processing temperature, and avoid silicone-based mould release overspray that can interfere with downstream painting or bonding.

Extruded sheet from S704 is converted into refrigerator inner liners and appliance housings where the required balance of low-temperature impact and thermoforming draw is achieved at sheet temperatures of 140–160 °C. In injection moulding, S704 is applied to vacuum cleaner housings, toys, and general appliance components with nominal wall sections of 2.0–3.5 mm. The resin is not recommended for continuous outdoor exposure without a UV stabilization package; weathering under ISO 4892-2:2013 reduces gloss and yellowness index after 500–1000 h depending on pigmentation. Published data for this specific configuration is limited for UV-stabilized S704 in automotive exterior applications, so accelerated weathering trials on molded plaques are required prior to such use.