Tianjin Dagu Chemical ABS DG-308 is a general-purpose acrylonitrile-butadiene-styrene injection-moulding grade supplied in natural pellet form. The material is specified for thin-walled components in which melt fluidity, gloss repeatability, and short cycle-time capability carry more weight than low-temperature impact retention. Typical conversion occurs on reciprocating-screw injection-moulding machines rather than on extrusion or blow-moulding lines. In the Dagu ABS slate, DG-308 occupies a high-flow position between standard-flow grades and high-heat grades, with the designation reflecting a specific modifier and stabiliser package rather than a single-variable property shift. The grade is used in electrical accessory housings, small appliance shells, office-machine cassettes, telephone handset bodies, router front covers, and selected automotive interior trim parts that do not require long-term ultraviolet stability. The product is commonly packaged in 25 kg multi-wall bags or bulk containers, with a lot-specific certificate of analysis reporting melt-volume-flow rate, impact strength, and thermal properties.

What Distinguishes DG-308 From Other Dagu ABS Grades in the Same Application Class?

Grade substitution decisions for DG-308 normally turn on the relationship between melt-volume-flow rate and notched Izod impact. The material is selected when a mould-filling analysis indicates that a higher-viscosity grade would exceed the machine pressure envelope or produce short shots in walls below 1.5 mm. Published supplier data place the melt-volume-flow rate under ISO 1133-1 at 220 °C with a 10 kg load in a broad range of 18–28 cm³/10 min, with pigmented lots shifting within this window. The penalty is a lower notched Izod value under ISO 180/A than the higher-impact Dagu grades; therefore DG-308 is not the first-choice material for snap-fit clips exposed to sub-zero assembly or for parts requiring retention after drop impact at -20 °C. Compared with high-heat Dagu grades, the Vicat softening temperature under ISO 306/B50 is approximately 15–25 °C lower, a difference that excludes DG-308 from instrument-panel surfaces near glazing if solar soak exceeds 100 °C. Published data for lot-to-lot comparisons among all Dagu grades is limited, so existing tool validation should rely on the certificate of analysis for the exact production lot rather than on nominal datasheet comparisons.

Under the standard test protocols used by resin suppliers, published datasheet values for DG-308 fall in the following ranges. These values are not guarantees; they derive from natural-colour injection-moulded specimens conditioned at 23 °C and 50 % relative humidity before testing.

Colourant carriers, flame-retardant modifiers, and regrind levels can shift viscosity and impact. For uncontrolled regrind, addition is generally limited to 20 wt% in non-aesthetic parts because butadiene-phase crosslinking accumulates after repeated heat histories. The table is assembled from supplier technical bulletins and should be treated as a screening tool; mould design and acceptance criteria should be derived from the lot-specific certificate of analysis.

Drying, Thermal Stability, and Screw Plastication Limits

Moisture control is the first processing boundary. ABS pellets stored at ambient relative humidity above 60 % can adsorb enough moisture to produce splay during mould filling. The material should be dried in a desiccant hopper at 80 ± 5 °C for 3–4 h to reach a target moisture content below 0.05 wt%. If storage time exceeds 24 h in an uncontrolled environment, the drying time is extended to 6 h. A desiccant dryer with a dew point of -40 °C or lower is preferred; hot-air hoppers are not a substitute when moulded surfaces are grained or gloss-specified.

Melt temperature measured at the nozzle should remain between 210 °C and 250 °C. Cylinder zones from feed to nozzle are typically set at 180 °C, 210 °C, 230 °C, and 240 °C on a general-purpose screw of 20:1 to 24:1 L/D and compression ratio 2.5:1 to 3.0:1. Back pressure is held at 5–15 bar hydraulic to homogenise pigment without excessive shear heating. Residence time above 240 °C should not exceed 5 min; longer periods accelerate butadiene-phase thermo-oxidative degradation, visible as yellowing or gloss loss. A barrier screw is not required for this grade, and a high-shear dispersion section is unnecessary; it can raise melt temperature by 10 °C or more and may narrow the operating window. Purging with a styrenic purge compound or general-purpose ABS is required before shutdown.

Because DG-308 is frequently specified for thin-wall enclosures with flowpath-to-wall-thickness ratios above 150:1, tooling design determines the practical injection envelope. Edge gates should be dimensioned at 0.5–0.8 times the nominal wall thickness; fan gates and tab gates are used for grained surfaces. For walls below 1.2 mm, sequential valve-gate hot-runner systems maintain fill balance across multi-cavity tools. Melt temperature at the gate is maintained near 230 °C, while the mould surface is controlled between 40 °C and 80 °C; the upper half of this range improves gloss and weld-line strength. On toggle-clamp machines from 80 t to 500 t, clamp force requirements are typically 3–5 kN/cm² of projected area for DG-308. Vent depths of 0.015–0.025 mm are required; below this range, burn marks appear at the end of fill. Ejection temperature should be below 80 °C to avoid distortion in flat sections, and post-mould shrinkage in the flow direction is typically in the range of 0.4–0.7 %.

Applications observed on production lines include vacuum-cleaner housings, electric-kettle bodies, shaver shells, router front bezels, business-machine cassettes, and automotive interior door trim. In these parts, DG-308 is selected over higher-viscosity ABS when mould deflection or injection-pressure peaks exceed the machine curve. The material is not intended for extrusion profiles or thermoforming sheet, because the high melt-volume-flow rate reduces melt strength and complicates draw-down control on polished rolls. Published data for extrusion-grade performance of this specific configuration is limited.

When DG-308 Replaces Higher-Impact or Higher-Heat ABS in Existing Tools

Existing tools qualified for DG-417 or a higher-impact ABS may require runner and gate rebalancing if DG-308 is substituted. The higher melt-volume-flow rate under ISO 1133-1 reduces fill pressure in thin sections; on production-scale machines, injection-pressure reductions of 15–25 % have been recorded for wall thicknesses below 1.5 mm, but published data for this specific comparison is limited. The corresponding risk is reduced melt backflow if the non-return valve is worn; screw recovery time can increase by 10–20 % because of lower viscosity. Hold-pressure profiles should be re-established, not copied from the previous grade.

The operational boundary includes an avoidance of outdoor exposure unless a UV-stabilised variant is specified. Standard DG-308 is not a weatherable grade and will exhibit chalking or surface embrittlement after repeated UV cycles. Chemical resistance is typical of ABS: prolonged contact with ketones, esters, aromatic hydrocarbons, or low-molecular-weight chlorinated solvents can induce environmental stress cracking. Compliance documentation for standard natural grade typically references RoHS Directive 2011/65/EU as amended by EU 2015/863 and REACH Regulation EC 1907/2006; these statements apply only to the resin as supplied and should be reconfirmed after downstream incorporation of colourants, flame retardants, or recycled content. No food-contact declaration under FDA 21 CFR or EU 10/2011 should be inferred without a lot-specific certificate.