North Huajin Chemical ABS 345 is a medium-flow acrylonitrile-butadiene-styrene injection molding resin produced by North Huajin Chemical Industries Group. The numeric designation 345 identifies a specific viscosity-rubber balance within the supplier’s ABS grade slate and does not directly encode a melt flow rate or Izod impact value. Published lot-specific datasheet values for this grade are limited in secondary industrial databases; procurement-grade verification therefore requires the supplier’s certificate of analysis and, where available, a production trial lot. Segment-level property descriptions for medium-flow ABS injection molding resins place the material within an ISO 1133-1:2022 melt mass-flow rate range of 10 g/10 min to 30 g/10 min at 220 °C/10 kg, an ISO 1183-1:2019 density range of 1.04 g/cm³ to 1.06 g/cm³, and an ISO 180:2019 notched Izod impact range of 18 kJ/m² to 28 kJ/m² at 23 °C. These ranges define the class in which ABS 345 is positioned; they are not certified lot-release values.

Tensile yield stress for this medium-flow segment is typically measured at 40 MPa to 48 MPa under ISO 527-2:2012, flexural modulus at 2100 MPa to 2600 MPa under ISO 178:2019, and Vicat softening temperature B50 at 95 °C to 105 °C under ISO 306:2022. The melt exhibits pronounced shear thinning; capillary rheometry at 230 °C generally records apparent viscosity below 100 Pa·s at shear rates above 1000 s⁻¹. These rheological characteristics support short residence-time injection molding in complex tool geometries while limiting the ability to extrude thick profiles with melt strength. The two-phase morphology comprises a rigid styrene-acrylonitrile matrix and dispersed polybutadiene or styrene-butadiene rubber particles. Medium-flow grades such as ABS 345 balance rubber content and matrix molecular weight to obtain sufficient melt fluidity while retaining notched impact. Capillary rheometry at 230 °C shows shear-thinning behavior typical of ABS: apparent viscosity falls from approximately 300 Pa·s at 100 s⁻¹ to below 100 Pa·s at 1000 s⁻¹. This viscosity decline is important when filling ribs, thin bosses, and flow-length-to-wall-thickness ratios above 150:1.

Mechanical property comparisons are valid only when test specimens are injection molded and stored according to ISO 294-1:2017 and ISO 291:2008. Variations in mold surface temperature, injection velocity, and packing pressure can shift notched Izod impact by more than 10% even when the same resin lot is tested.

Conditioning, Drying, and Reciprocating Screw Processing Boundaries

ABS is hygroscopic, and the processing boundary for ABS 345 is set by residual moisture. Pellets stored in open containers at ambient relative humidity above 60% require dehumidifying forced-air drying at 80 °C for 2 h to 4 h; target moisture content before melt processing is below 0.1%. Drying at 90 °C or higher can cause pellet surface tack and bridging in the hopper if residence time exceeds 6 h. The moisture limit is not a minor recommendation: injection at residual moisture above 0.2% produces hydrolysis-induced molecular weight loss, splay and silver streaking in thick sections, and measurable loss of notched Izod impact according to ISO 180:2019.

On a general-purpose reciprocating screw injection molding machine, the recommended barrel temperature profile for medium-flow ABS is typically 200 °C rear, 220 °C middle, 230 °C front, and 235 °C nozzle, with actual melt temperature checked by needle-probe pyrometry at 235 °C to 245 °C. Mold surface temperature should be regulated with pressurized water or oil thermolators at 40 °C to 80 °C. Lower mold temperatures reduce cycle time but intensify frozen-in orientation and lower weld-line strength; higher mold temperatures improve surface gloss and impact but lengthen cooling and increase sink mark risk.

For a 45 mm general-purpose screw in a 2500 kN clamp force machine, screw recovery speed should be limited to 0.15 m/s to 0.25 m/s to prevent gas entrapment and shot-weight instability. Cushion control should hold ±1.5 mm to maintain packing reproducibility. Injection velocity is usually set from 30 mm/s to 80 mm/s depending on flow length and wall thickness. Packing pressure typically falls between 40 MPa and 70 MPa hydraulic, held for 3 s to 8 s on parts with nominal wall 2 mm to 3 mm.

Screw design for ABS 345 favors a general-purpose polyolefin screw with a compression ratio between 2.0:1 and 2.8:1, length-to-diameter ratio 20:1 to 24:1, and a check ring of ball-check or ring-check type. Vented barrels are generally unnecessary and may increase gas entrainment if the vent is not matched to screw decompression.

When a molded enclosure must balance cost, dimensional reproducibility, and impact resistance without requiring higher flame retardance than UL 94 HB, ABS 345 is deployed in appliance fascia, electrical switch covers, consumer electronics housings, and general-purpose industrial guards. Dimensional tolerance capability is contingent on mold temperature uniformity and post-mold shrinkage control; processing with mold temperatures in the 50 °C to 70 °C range typically yields shrinkage of 0.4% to 0.7% in flow direction and 0.5% to 0.8% transverse, evaluated after 48 h at 23 °C and 50% relative humidity per ISO 291:2008. Unmodified ABS 345 should not be specified for applications requiring UL 94 V-0 at 1.5 mm; flame-retardant ABS formulations occupy that service space.

Field data on 2800 kN hydraulic presses with multi-cavity hot-runner tools indicates that medium-flow ABS can maintain gate-to-gate weight variation below 0.35% when melt pressure at the nozzle is held within ±1.0 MPa and hot-runner manifold temperature is held below 245 °C. Failures observed in production include gate blush and cosmetic flow lines when injection velocity exceeds 80 mm/s for polished mold surfaces, and plate-out on valve-gate stems after continuous running above 250 °C for more than 8 h. Hot-runner nozzle tips should be profiled with separate temperature zones to avoid local overheating. Multi-cavity filling imbalance can be corrected by independent nozzle temperature offsets of ±5 °C rather than by raising overall melt temperature.

What Separates a Medium-Flow ABS 345 from High-Impact Extrusion Grades and High-Flow Thin-Wall ABS?

ABS 345 is differentiated primarily by its melt-flow/rubber-toughness balance. High-impact ABS grades, often intended for extrusion or thick-section molding, contain a higher rubber-phase volume fraction and exhibit lower ISO 1133-1:2022 melt flow, commonly below 8 g/10 min at 220 °C/10 kg, with notched Izod impact above 30 kJ/m². They deliver greater crack-arrest capability in thick-wall components but require higher barrel temperatures, consume more energy in plasticization, and are less suited to filling ribs and thin sections. High-flow ABS grades occupy the opposite end of the design space; melt flow rates may exceed 30 g/10 min at 220 °C/10 kg, but notched Izod impact can fall below 15 kJ/m². These materials fill thin-walled parts but show lower toughness and greater susceptibility to embrittlement after heat aging.

Relative to HIPS, ABS 345 has higher tensile yield strength and heat resistance but lower resistance to polar solvents such as ketones and esters. Relative to PC/ABS blends, ABS 345 has lower notched impact and lower heat deflection temperature but offers lower density, lower processing temperature, and lower melt pressure required to fill long thin sections. When an application requires recovery from high-speed impact at low temperature below -20 °C, ABS 345 is not a direct substitute for PC/ABS or high-impact ABS; the lower rubber content limits low-temperature ductility.

If the material is molded in a tool with long flow lengths exceeding 200 mm, melt flow rate alone does not predict fill; flow-length-to-wall-thickness ratio, gate size, and packing pressure dominate. Medium-flow ABS at 240 °C melt can often fill a 150:1 flow ratio at 2.5 mm wall thickness, but a 250:1 ratio generally requires a high-flow grade or a higher melt temperature. This boundary separates ABS 345 from high-flow ABS used in thin-wall appliance covers.

Regrind addition up to 20% by weight is common for non-appearance parts when granulate is clean and dried. Higher regrind fractions may reduce notched Izod impact and color consistency. For appearance-critical components, regrind is typically limited to 10% and controlled with melt filtration to avoid black specks from degraded hot-runner residues.

For electrical and appliance applications, material acceptance may include RoHS recast 2011/65/EU Annex II substance restrictions and REACH candidate list verification. ABS 345 unmodified is not inherently UV-stable; outdoor exposure requires pigmentation or paint when UV resistance is specified. Lot-to-lot consistency should be assessed by melt flow rate per ISO 1133-1:2022, notched Izod per ISO 180:2019, and Vicat B50 per ISO 306:2022. Dimensional release testing should reference ISO 294-4:2018 for shrinkage.

If ABS 345 is dried below 0.1% residual moisture but the melt is held above 260 °C for more than 12 min, thermal degradation initiates, producing yellowing, butadiene-phase crosslinking, and a measurable drop in notched Izod impact. The same thermal boundary applies to hot-runner overflows and long residence-time color changes. Production scheduling should avoid barrel residence times above 15 min and use melt decompression zones no deeper than 3 mm on the screw to minimize air entrapment.

Chemical incompatibility boundaries include exposure to ketones, esters, aldehydes, and chlorinated solvents; these cause stress cracking in molded parts under applied strain. The grade should not be compounded with amine-based flame retardants that can accelerate thermo-oxidative degradation in the butadiene phase during melt processing. Because published data for ABS 345 under specific heat-aging protocols is limited, long-term end-use qualification should include thermal aging at 90 °C for 500 h per ASTM D3045-18 or customer-specific thermal cycling when electrical enclosure standards apply.