Within the LG Chem acrylonitrile-butadiene-styrene product range, the HI-165 designation identifies an unfilled, high-impact injection-moulding grade supplied in pellet form. The grade is specified for parts in which room-temperature notched impact resistance, dimensional consistency, and practical fill in complex tools are weighted over elevated continuous service temperature. HI-165 is not a heat-resistant, flame-retarded, or UV-stabilized compound. The nominal values discussed in this product introduction are characteristic of unfilled high-impact ABS in this viscosity band; lot-specific certificates of analysis and the supplier technical data sheet are the controlling documents for batch acceptance. Test methods applicable to the grade include ISO 1133-1, ISO 527-2, ISO 178, ISO 179-1, ISO 75-2, and ISO 306.

Is HI-165 a High-Flow or High-Toughness Grade Within the ABS Portfolio?

HI-165 is positioned in the high-impact, medium-to-high-flow segment. Melt volume-flow rate at 220 °C under 10 kg load according to ISO 1133-1 is generally reported in the 25–35 cm³/10 min band. This flow level distinguishes HI-165 from low-flow high-impact grades that require greater injection pressure for thin-wall fill. Notched Charpy impact at 23 °C under ISO 179-1/1eA is typically 25–35 kJ/m²; this is adequate for small appliance and consumer-electronics housings but below the level expected from a PC/ABS blend at sub-zero temperatures. The flexural modulus is typically 2100–2400 MPa under ISO 178, and the tensile yield stress is typically 40–46 MPa under ISO 527-2. Because the grade contains no reinforcing filler, modulus and heat-deflection performance remain close to other unfilled high-impact ABS grades. In mould-filling simulation, shear-viscosity curves obtained by capillary rheometry according to ISO 11443 are preferred over a single melt-flow value.

In production, a hydraulic injection moulding machine with a 35–40 mm screw and 20:1–24:1 L/D is commonly used. Barrel temperatures are set in the range 210–240 °C, with the nozzle at 220–240 °C and the mould at 40–70 °C. Mould temperatures below 40 °C reduce gloss and knit-line strength, while temperatures above 70 °C extend cycle time with limited benefit for unfilled ABS. Back pressure is typically maintained below 1.5 MPa hydraulic to avoid excessive shear heating. Holding pressure is determined by part weight versus hold-time trials, not by data-sheet values alone.

Molecular-Level Origins of the Impact–Flow Balance

The impact resistance of HI-165 arises from a continuous poly(styrene-acrylonitrile) matrix and a dispersed polybutadiene rubber phase. The rubber-phase content, particle-size distribution, and grafting ratio are proprietary to the manufacturer; published data for this specific configuration is limited. In general, high-impact ABS of this class uses a bimodal rubber particle-size distribution to balance low-temperature toughness and surface finish. Larger rubber particles initiate energy absorption through craze formation, while smaller particles increase rubber-phase interaction with the SAN matrix. The higher melt flow of HI-165 compared with low-flow high-impact ABS is normally achieved by modifying the SAN molecular weight or the rubber-phase structure. This directly affects chemical resistance: the material is attacked by ketones, esters, aromatic hydrocarbons, and chlorinated solvents. Environmental stress-cracking resistance should be tested according to ISO 22088-3 for parts exposed to cleaners, plasticizers, or adhesive vapours.

Molecular-weight metrics for the SAN phase are not stated in typical commercial documentation. A lower molecular-weight SAN fraction improves melt flow but can reduce fatigue resistance and long-term creep. HI-165 is therefore not specified for continuously loaded structural components in hot environments. Snap-fits with low local strain can be acceptable, but cyclic loading data under ISO 6603-2 instrumented puncture and ISO 527-2 tensile fatigue are not typically supplied for this grade and require end-use testing.

Predrying before processing is mandatory when ambient relative humidity exceeds 60%. A desiccant dryer with a dew point of -20 °C or lower is operated at 80 °C for 2–4 h. The target moisture content in the melt is 0.05 wt% or lower; measurement is performed by Karl Fischer titration or a calibrated moisture analyser on a purged sample. Failure to dry produces surface splay, gloss variation, and brittle knit lines, particularly in hot-runner tools with narrow gates. If bulk containers are opened for more than 8 h in humid plant conditions, the material should be re-dried before processing. Return-map systems that expose the resin to ambient air for longer than 12 h should be sealed or purged with dry air.

When Mould Temperature Falls Below 50 °C, What Happens to Weld-Line Ductility?

Weld-line formation is a process-sensitive limitation in high-impact ABS parts. At a mould temperature below 50 °C, the melt fronts do not fully interdiffuse; the weld line may exhibit a transition from ductile deformation to brittle fracture even when the bulk material retains high notched impact. For parts with wall thickness below 2 mm, the notch radius at the weld line and the orientation of the rubber phase near the melt front further reduce ductility. To preserve weld-line strength, the mould surface temperature is held at 50–70 °C. Injection velocity is increased where feasible, and the gate position is selected to move the weld line away from high-tensile stress regions. Venting at the weld line should have land width of 0.01–0.02 mm and depth of 0.1–0.2 mm before the vent channel; trapped gas at the melt front increases local degradation and worsens weld strength.

Hot-runner manifold and nozzle temperatures should not exceed 260 °C. Residence time above 260 °C causes depolymerization of SAN and rubber-phase oxidation, visible as yellowing and brown streaking. In a 16-cavity hot-runner tool, balancing the runner system is critical because cavities fed by longer flow paths may show lower packing pressure and higher weld-line notch sensitivity.

Extrusion of sheet from HI-165 is conducted on a single-screw extruder with a barrier screw and L/D of 30:1. Temperature profiles from feed zone to die commonly run from 180 °C to 220 °C, with die temperature at 210–230 °C. Screen packs with 60/80/100 mesh are used to remove gels. Back pressure across the screen pack should be monitored because excessively high pressure causes melt-temperature rise. Edge tear during polishing is a practical defect when the melt temperature at the die exceeds 230 °C or when draw ratio exceeds 1.1:1. Sheet is then thermoformed at a surface temperature of 150–170 °C; higher temperatures cause gloss reversal and local wall thinning in plug-assisted forming. Because HI-165 is an injection-grade ABS, its melt strength is lower than that of dedicated extrusion grades; sag control is required for sheet widths above 600 mm.

What Performance Limits Distinguish HI-165 from Glass-Filled ABS and PC/ABS Blends?

HI-165 is not a substitute for glass-filled ABS when flexural modulus and creep resistance are primary requirements. Glass-filled ABS with 20 wt% glass fibre can exhibit a flexural modulus above 4500 MPa, roughly double the unfilled grade. The unfilled HI-165 has lower mould shrinkage anisotropy and a smoother surface, which is advantageous for visible parts. PC/ABS blends maintain higher impact at low temperature and higher heat deflection, but require more aggressive drying and often higher melt temperatures. HI-165 is chosen for interior housings where ambient impact resistance, ease of colouring, and lower tool wear from unfilled material are valued. In painted exterior trim with oven baking above 110 °C, HI-165 is not suitable; heat-resistant ABS or PC/ABS is specified instead. The notched Charpy impact of HI-165 at -30 °C under ISO 179-1/1eA is typically 10–15 kJ/m², compared with higher low-temperature impact in PC/ABS blends. This is a critical selection boundary for outdoor enclosures in cold climates.

Decorative painting and electroplating are secondary operations. For painting, the surface is cleaned with isopropanol or a mild detergent; solvent-borne adhesion promoters based on ketones can craze the surface. Adhesion is verified by ASTM D3359 cross-cut tape pull on moulded plaques. Electroplating of HI-165 is not a primary application; plating-grade ABS typically uses a tailored high-butadiene rubber phase and etch-roughening behavior. If plating is required, a dedicated plating ABS should be selected. The grade may be coloured with masterbatch at 2–4 wt%; preblending in a low-shear tumble mixer is sufficient for uniform distribution on injection machines with a mixing screw.

Regulatory Status and Documentation Requirements

Documentation supplied with the resin generally states compliance with the restriction-of-hazardous-substances requirements of Directive 2011/65/EU Annex II and Directive (EU) 2015/863 as applicable to the grade as supplied. REACH compliance is addressed through the safety data sheet prepared under Regulation (EC) No 1907/2006 Article 31; converters should verify whether any substance-of-very-high-concern declaration is current for their supply chain. The unfilled grade is not a food-contact resin; FDA 21 CFR 177.1020 should not be cited for HI-165 unless a grade-specific clearance is delivered by the supplier. UL 94 flammability classification for unfilled ABS is typically HB at 1.5 mm and should not be used for enclosures that require V-2, V-1, or V-0 listing. For toy applications, the converter must verify migration of certain elements under EN 71-3 and formaldehyde under EN 71-11 at the final article level.

Production-line failure modes include gloss variation from inconsistent mould temperature, splay from wet material, and gate blush from high shear. When a 25 mm twin-screw extruder with L/D 40:1 is used to compound masterbatch into HI-165, screw speeds above 400 min⁻¹ can increase melt temperature above 260 °C and degrade the rubber phase. Melt temperature at the die should be monitored. Vacuum venting at -0.08 MPa or deeper is used only when volatile levels warrant it.

If Regrind Ratios Exceed 30% in Semi-Structural Housings

Regrind is common in production of ABS housings, but high-impact grades lose rubber-phase morphology through repeated melt history. Up to 30% regrind is often operationally acceptable for non-appearance and semi-structural parts if the regrind is generated from clean sprues and rejects. Above 30%, the melt-flow index may increase and the notched impact may decrease because of repeated shear on the polybutadiene phase. A production line using a central granulator should screen regrind through a 4–6 mm mesh and avoid dust; fine particles below 0.5 mm can cause feeding instability. If the tool is a hot-runner mould with small gates below 0.8 mm diameter, higher regrind levels may produce gate blockage from unmelts. Validation should include melt-flow measurement per ISO 1133-1, Charpy impact per ISO 179-1, and visual inspection of moulded plaques at each regrind ratio.

Post-mould dimensional movement is influenced by packing and cooling. Mould shrinkage in the flow direction is typically 0.4–0.7% under ISO 294-4; transverse shrinkage may be 0.5–0.7%. Annealing at 80 °C for 2 h may stabilize dimensions for precision parts, but can slightly reduce impact. Parts held at elevated service temperatures above 65 °C may undergo physical aging and show a small increase in stiffness and a decrease in impact. This should be tested before specifying snap-fits.

Automotive interior trim, small appliance housings, personal care devices, and consumer-electronics casings are typical applications for HI-165. In automotive interior parts, the surface finish and dimensional stability are generally acceptable for steering-column covers and console side panels when moulded under controlled temperatures. Chemical contact with plasticizers, sun cream, and interior cleaners can produce stress cracking; environmental stress-cracking screening under ISO 22088-3 should be performed. Bonding is typically limited to mechanical fastening or solvent-free adhesives; solvent-borne adhesives containing ketones may craze the surface. Published data for this specific configuration is limited for fatigue and creep; final part validation should include instrumented puncture testing under ISO 6603-2 and UV exposure according to ISO 4892-2 for any exterior-adjacent use.