Lotte Chemical STAREX® MABS TX-0585 NP is a methyl methacrylate-acrylonitrile-butadiene-styrene copolymer manufactured and supplied as natural, uncolored cylindrical pellets. The NP suffix denotes a natural pellet feed without added pigments or carbon black; coloration is normally introduced by the converter through a SAN- or MABS-based masterbatch. The material is intended for injection-moulded transparent components that require a balance of thin-wall flow, notched impact strength, and surface replication. In contrast to general-purpose ABS, the methyl methacrylate comonomer and a controlled rubber-phase morphology suppress gross light scattering, producing transparent mouldings when the melt is processed within a narrow thermal window.

Specification Profile Under ISO 1133 and ISO 527

Published typical values for the natural pellet grade are reported in the following table. These values are not simultaneous specification limits and batch-to-batch variation should be confirmed against the manufacturer's certificate of analysis. The melt volume-flow rate is determined at 220 °C with a 10 kg load, placing the material in the high-flow transparent styrenic range. This flow level permits thin-wall filling at lower injection pressures than standard MABS grades, but it also reduces the maximum continuous service temperature relative to higher-viscosity optical grades.

Specimen preparation for the above values follows ISO 291 with conditioning at 23 °C and 50 % relative humidity. The Charpy notched value is a single-point reference, not a design load. Components containing weld lines, sharp corners, or poorly located gates will exhibit lower impact performance than the resin baseline. The Vicat B50 value is a single-point softening temperature obtained under a 50 N load with a 50 °C/h heating rate according to ISO 306; it is not an upper service temperature for load-bearing parts.

Why Does TX-0585 NP Depart from Opaque ABS in Optical and Rheological Behaviour?

Transparency in MABS rests on two simultaneous optical conditions. The continuous SAN phase is modified with methyl methacrylate so that its refractive index approaches the refractive index of the dispersed butadiene-based rubber domains, and the rubber domains are held at a particle size below roughly 0.1 µm. In opaque ABS, the rubber domains are larger and the refractive-index mismatch is sufficient to produce Mie scattering. In the transparent MABS grade, the smaller domains and closer index match shift the scattering regime toward Rayleigh scattering and reduce the measured haze to 1.5–2.5 % on a 3-mm plaque under ASTM D1003. This morphology is thermally fragile. If the melt is exposed to excessive temperature or shear, the rubber phase can oxidize or agglomerate, the SAN continuous phase can yellow, and the refractive-index difference increases, permanently raising haze and yellowness.

Rheologically, the melt volume-flow rate of 22–26 cm³/10 min measured under ISO 1133-1 places the grade in the high-flow region for transparent styrenics. This viscosity level permits lower injection pressure in thin-wall tools, but it also reduces the margin between adequate packing and jetting. In a general-purpose injection screw with L/D 20:1–24:1 and compression ratio 2.2:1–2.8:1, the plasticising time is usually shorter than the cooling time for wall sections up to 2.0 mm. For multi-cavity layouts, the high-flow grade requires geometrically balanced runners because small flow-length differences become visible as cavity-weight variation and differential gloss.

For injection moulding, desiccant drying is mandatory whenever the pellets have been exposed to ambient air for more than 2 h at relative humidity above 60 %. The granulate is dried at 80–90 °C for 4 h with a dew point of −20 °C or lower; residual moisture immediately before melt entry is maintained at ≤0.05 wt%. The equilibrium moisture uptake at 23 °C and 50 % RH is approximately 0.15–0.25 wt% under ASTM D570; this quantity is sufficient to produce splay and hydrolysis-induced molecular weight loss if drying is omitted.

A reciprocating screw with L/D 20:1–24:1 and compression ratio 2.2:1–2.8:1 is suitable. Barrel setting: rear zone 190–210 °C, middle zone 210–230 °C, front zone 220–235 °C, nozzle 230–240 °C. The mould surface temperature is held at 40–70 °C. The material is processed with a melt cushion of 3–6 mm, back pressure 0.5–1.5 MPa, and screw rotation speed 50–120 rpm. Hot runner manifold temperature should not exceed 240 °C, and total melt residence time above 230 °C should be kept below 10 min. Vent depths on the tool are set at 0.02–0.03 mm to vent moisture-derived gases. Injection speed is set to fill the cavity in 1–3 s for wall sections of 1.2–2.0 mm; final hold pressure is determined by short-shot and gate-seal evaluation.

Relative to PMMA, TX-0585 NP has lower tensile modulus and lower scratch resistance but higher notched impact strength. PMMA transmits slightly more visible light and has a harder surface, whereas the MABS grade tolerates snap-fit assembly and local impact without the brittle cracking often seen in PMMA at thin hinges. Relative to polycarbonate, the MABS grade has a lower Vicat softening temperature and lower impact energy, but it processes at lower melt temperature and with lower melt viscosity. It is not a substitute for polycarbonate in applications requiring autoclave sterilisation or continuous service above 95 °C.

Typical injection-moulded applications include cosmetic caps, compact cases, transparent appliance panels, vacuum cleaner sight windows, and office-machine paper guides. In cosmetic packaging, the formulation should be tested against the final fragrance or skin-care matrix because ester-based formulations can plasticize the styrenic matrix and reduce surface gloss over time. Long-term compatibility is evaluated by an ASTM D543 immersion test or an equivalent package-seal test on the actual moulded component. For appliance lenses with wall thickness down to 0.8 mm, the high-flow behaviour reduces filling pressure, but wall thickness below 0.8 mm increases orientation haze and the probability of short shots. Flow simulation and prototype shot evaluation are required before tool hardening.

When Mould Temperature and Shear History Control Haze

The optical appearance of a moulded part is set during the filling and cooling phases, not by pellet properties alone. The two process variables that most influence final haze are the mould surface temperature and the local shear rate at the gate. At mould temperatures below 40 °C, the melt is quenched before molecular orientation can relax; the resulting birefringence appears as haze or iridescence near the gate. At 60–70 °C, relaxation is more complete and the surface replicates the polished tool more closely, but the cycle time lengthens and thick sections may show sink marks.

The gate shear rate is controlled through gate diameter and injection speed. A small edge gate with a high injection speed can generate local melt temperatures above 250 °C at the gate wall even when the bulk melt temperature is within specification. This local temperature spike initiates butadiene oxidation and SAN yellowing, which appear as a dull halo around the gate. Weld lines represent a second optical discontinuity. When two flow fronts meet, the dispersed rubber particles are locally depleted at the junction and light scattering in the weld area increases. Weld-line haze cannot be removed by drying or by raising the mould temperature alone; the tool must be gated to place weld lines on non-visible surfaces or the part must be redesigned to permit flow-front reheating. In multi-cavity tools, geometrically balanced runners are used because a cavity-weight difference of more than 5–8 % can produce visible gloss variation even when no cavity is short.

Coloration is performed with a SAN- or MABS-based masterbatch at let-down ratios of 1–3 %. Polyethylene-based masterbatch carriers are not recommended because the incompatible carrier forms discrete domains that reduce impact strength and increase haze. The final colour concentrate must be dried together with the natural pellets before processing.

Chemical Resistance Boundaries and Solvent-Induced Stress Cracking

Chemical resistance is moderate and is defined by the styrenic matrix rather than the rubber phase. Dilute aqueous acids and alkalis at room temperature are usually resisted for short contact periods, but esters, ketones, chlorinated hydrocarbons, and aromatic hydrocarbons must not remain on the surface. These solvents plasticize the matrix and induce craze formation in stressed regions. Moulded-in stress, especially around metal inserts and snap-fit hooks, accelerates environmental stress cracking. If an assembled component is exposed to alcohol or surfactant solutions, annealing at 70–80 °C for 2 h may reduce internal stress, but solvent compatibility should be confirmed by an ASTM D543 immersion test with the actual chemical formulation and the actual moulded part.

Unstabilized natural MABS is not recommended for permanent exterior use. Ultraviolet radiation promotes yellowing and surface microcracking; if an exterior part is required, a weatherable grade or an ultraviolet absorber package should be evaluated under ISO 4892-2. Regulatory declarations are lot-specific. RoHS 2011/65/EU and REACH Regulation (EC) No 1907/2006 documentation is typically provided on request, but no medical-grade USP Class VI or food-contact claim applies to the natural pellet unless confirmed by the supplier for the specific lot.