Dongguan Zhengxian ABS 38NA is a natural-colour acrylonitrile-butadiene-styrene copolymer supplied in pellet form for injection moulding and selected extrusion applications. The grade designation situates the product within the manufacturer’s medium-flow general-purpose ABS series; the numeric segment “38” denotes a nominal melt-flow class and the suffix “NA” identifies natural/undyed feedstock. Publicly available grade-specific datasheet values for this configuration are limited, and procurement specifications should therefore be based on the supplier certificate of analysis, lot-specific melt-flow data, and retained-sample mechanical testing. When proprietary values are not released, the material is reasonably characterised by the structural features of medium-flow ABS: a continuous styrene-acrylonitrile phase providing stiffness and hardness, a dispersed polybutadiene rubber phase providing impact energy absorption, and a melt viscosity suited to filling medium-thickness sections without high packing pressure. Typical polybutadiene contents for general-purpose ABS of this class are reported in the range 8–18 wt%; the exact rubber content of 38NA is not publicly released and may vary with production campaign. Applications documented for comparable natural ABS grades include electrical enclosures, domestic appliance control panels, telephone handsets, audio equipment fascias, furniture edge bands, and general-purpose technical mouldings. The material is not specifically released as a UV-stabilised grade, and outdoor exposure may require additional formulation verification.

What Melt-Flow and Mechanical Property Envelope Applies to ABS 38NA?

Because the manufacturer has not published a complete property schedule in a consolidated format, the following envelope is built from typical values for medium-flow general-purpose ABS grades and must not be read as a guaranteed specification for 38NA. The supplier CoA is the authoritative document for lot-specific values.

The notched impact range shown above is sensitive to specimen thickness, notch radius, and moulded-in stress. At sub-zero temperatures, the ductile-to-brittle transition of general-purpose ABS may occur between -20 °C and -40 °C depending on rubber particle size and graft morphology. For 38NA, low-temperature impact data should be requested before using the grade in cold-climate enclosures; published data for this specific configuration is limited.

Before hopper loading, moisture control takes precedence over barrel profile adjustments. ABS pellets are hygroscopic to the extent that surface moisture produces splay and internal voiding; 38NA should be dried in a desiccant dryer to a residual moisture content below 0.1 % and preferably below 0.05 %. Drying at 80 °C for 2–4 h with a dew point below -30 °C is typical for natural ABS, but extended residence times above 4 h at 85 °C can accelerate yellowing in unstabilised natural stocks. If ambient relative humidity exceeds 60 %, hopper sealing and closed-loop material handling become necessary. A material dryer with a regeneration circuit and a hopper capacity matched to shot weight should maintain inlet air temperature within ±5 °C of setpoint; larger deviations are associated with batch-to-batch surface gloss variation.

Injection Moulding Equipment Settings and Scale-Up Observations

For medium-flow ABS grades of this class, barrel temperature profiles typically follow a rising ramp from 60–80 °C in the feed zone to 180–230 °C in the compression zone and 200–250 °C in the metering zone, with nozzle setpoints between 210 °C and 250 °C. Melt temperatures above 260 °C are avoided because thermal degradation of the polybutadiene phase produces discolouration, free-surface defects, and a reduction in notched impact strength. Screw geometry should use a compression ratio of 2:1–2.5:1 and an L/D ratio of 20:1–24:1; a general-purpose three-zone screw is acceptable for most applications. Back pressure is maintained between 5 bar and 10 bar, and screw decompression is limited to 2–5 mm to prevent air entrapment without causing nozzle drool. On a 1500 kN hydraulic injection moulding machine with a 40 mm diameter screw, medium-flow natural ABS grades of this type typically require a screw cushion of 3–6 mm and a hold-pressure time of 0.5–1.5 s/mm of nominal wall thickness to control sink marks on ribs and bosses. Fill velocity is set sufficiently high to avoid premature freeze-off in thin ribs but low enough to avoid jetting and burn marks at gate locations; shear rates above 50 000 s⁻¹ for long periods can reduce impact properties.

Mould temperature should be held from 40 °C to 80 °C, with the lower half of the range favouring faster solidification and shorter cycle time, and the upper half improving knit-line strength and surface gloss on textured areas. Temperature control channels should be designed to maintain cavity-to-cavity variation within ±3 °C; excursions beyond this band are often visible as gloss differences in natural material.

When colour is critical, natural 38NA can be used as a base for liquid colour or masterbatch. The carrier resin should be SAN or ABS; polyethylene-based carriers are avoided because they can form a separate phase that reduces weld-line strength and alters gloss distribution on textured surfaces. Let-down ratios should follow the masterbatch supplier’s recommendation, but a practical upper limit of 4 wt% is common for non-slip additive concentrates in medium-flow ABS.

Comparing 38NA With High-Gloss, High-Impact, and Heat-Resistant ABS Grades

The primary differences between 38NA and other ABS grades in the same portfolio are in flow, rubber content, heat deflection, and surface appearance. High-gloss grades may use lower rubber content or surface-smoothing additives to reduce surface roughness, but the resulting reduction in polybutadiene phase can lower notched Izod impact values and increase notch sensitivity. High-impact ABS grades often raise rubber content above 18 wt% and may shift the ductile-to-brittle transition to lower temperatures, but tensile modulus and hardness fall, which makes them less suitable for large flat panels requiring creep resistance at elevated ambient conditions. Heat-resistant ABS grades based on α-methylstyrene or maleimide comonomer increase Vicat softening temperature above 105 °C, but melt viscosity rises and the processing window narrows; a medium-flow natural grade such as 38NA is used where the part does not require heat resistance beyond 95 °C but does require stable filling of multi-cavity tools. Flame-retardant ABS formulations containing brominated additives or antimony oxide require lower melt temperatures and more aggressive venting because decomposition products can corrode tool surfaces and generate plate-out. 38NA, as a non-flame-retardant natural grade, does not carry the same venting burden, but it also cannot be substituted into electrical enclosures requiring UL 94 V-0 at thicknesses below 1.5 mm without requalification.

When Mould Temperature Falls Below 40 °C, Skin-Layer Solidification Changes

If the mould surface temperature drops below 40 °C, the quenched skin layer of the ABS melt solidifies before the core can fully pack, producing higher frozen-in stress and a weaker knit line at the confluence of flow fronts. The condition is particularly observable in natural grades because residual stress differences appear as surface haze or local gloss variation after annealing. At temperatures between 20 °C and 35 °C, the material can still fill simple geometries, but impact strength at knit lines may decline by 10–30 % relative to the same part moulded with a 60 °C mould. The degradation is amplified by low melt temperature, short hold time, and high injection velocity. Therefore, for any part where the knit line is located in a load-bearing or drop-impact area, the lower mould temperature limit should be treated as 40 °C unless prototype testing satisfies the end-use impact requirement.

At the other extreme, mould temperatures above 80 °C extend cycle time and increase the risk of sticking in deep-draw tools, especially with untextured cores. Ejection temperature should be below the Vicat softening point by at least 10 °C; ejection before this threshold leads to deformation at bosses and snap-fit features.

For electrical enclosure and domestic appliance applications, the finished part must be evaluated against the end-product enclosure requirements of IEC 62368-1 or IEC 60335-1, depending on the final device category. The resin itself is not the sole determinant of compliance; wall thickness, colourants, regrind ratio, and moulding stresses influence ignition resistance, creepage, and clearance performance. For REACH and RoHS documentation, a batch-specific supplier statement covering the actual 38NA lot is required; a generic ABS declaration is not sufficient.

When switching to 38NA from a flame-retardant ABS or a filled styrenic, the screw and hot-runner system should be purged with a low-viscosity SAN or ABS purge compound until melt pressure traces stabilise and the extrudate is clear. The presence of polyamide or polyacetal residues in the barrel should be avoided because their thermal degradation products can generate black specks in the natural melt. Regrind ratios should not exceed 20 % for critical surfaces unless the regrind is derived from the same production campaign and has been re-dried. Published data for this specific configuration is limited; final processing limits should be established by a structured design-of-experiments trial on the intended tool.