LG Chem LUPOS MABS TR558A INP is a transparent methyl methacrylate-acrylonitrile-butadiene-styrene injection-moulding compound supplied as cylindrical pellets. The grade identity combines the Lupos trade name with the TR558A product code and the INP documentation suffix, which is retained in purchase specifications and should be checked against the supplier certificate for lot-specific characteristics. The material belongs to the MABS family according to ISO 19066-1:2014; it is produced by continuous bulk polymerisation, a route that reduces emulsifier residues compared with emulsion-grade transparent ABS. The molecular architecture consists of a rigid terpolymer matrix and a dispersed grafted polybutadiene phase whose particle-size distribution and refractive-index contrast are controlled to preserve visible-light transmission and notched impact resistance simultaneously.

Moulded components made from this grade are used in transparent engineering enclosures, diagnostic device housings, cosmetic packaging, medical consumables and office automation covers. Optical performance is specified on polished plaques with a total luminous transmittance of 90 % and a haze of 2.0 % measured per ASTM D1003. These values are not intrinsic; they depend on mould surface finish, melt-temperature history, moisture content and wall thickness. In high-gloss applications, cavity and core surfaces are usually polished to an SPI A-1 finish because a lower surface polish reduces transmission and raises haze beyond the values shown in producer literature.

Table values are representative laboratory data obtained on injection-moulded specimens under standardised conditions. They are not specification minima and must not be used for design allowables without lot-specific certificate data. Batch-to-batch variation in graft rubber content, residual monomer and molecular-weight distribution can alter notched impact and flow by a measurable amount; for load-bearing or regulated parts, conversion trials should be conducted on each lot against agreed process capability limits.

Prior to melt processing, the pellets are dried in a desiccant-bed dryer with a supply air dew point below -30 °C at 75 °C to 85 °C for 3 h to 4 h. If the ambient relative humidity exceeds 60 %, drying time is extended to 6 h and the hopper is kept closed and purged with dry air. Target residual moisture is below 0.02 wt% to 0.05 wt%; above this range, moisture converts rapidly to splay, silver streaks, gate blush and increased haze. Hot-air tray dryers are not recommended because localised pellet surface overheating can produce yellowing before the core moisture is removed. Feed-throat temperature is maintained below 60 °C to prevent particle fusion and bridging. Vacuum loaders should be fitted with clean stainless-steel hoppers; regrind should be re-dried under the same conditions and limited to 20 wt% unless optical testing per ASTM D1003 demonstrates no shift in haze or transmittance. Higher regrind ratios may reduce light transmission and increase mould deposit formation on core surfaces.

Injection moulding is typically performed on hydraulic or hybrid machines with clamp force selected from a projected-area requirement of approximately 0.35 kN/mm² to 0.55 kN/mm² for wall sections between 1.0 mm and 3.0 mm. A general-purpose screw with a compression ratio of 2.4:1 to 2.8:1 and an L/D ratio of 20:1 to 22:1 is used. The barrel temperature profile is set from 220 °C at the rear zone through 235 °C to 240 °C in the metering zone, with nozzle temperature between 230 °C and 240 °C. Melt temperature measured by an infrared pyrometer at the nozzle should not exceed 260 °C, because the polybutadiene phase undergoes thermo-oxidative degradation that increases yellowness index. Below 220 °C, thin-wall filling pressure rises and gate blush or sprue pull-in becomes frequent in sections below 1.2 mm.

Filling velocity is set by short-shot study: fill speed is increased until 95 % to 98 % of the cavity volume is reached before transfer to hold pressure. For a 110-tonne hydraulic press with a 32 mm diameter screw, nominal injection pressures between 600 bar and 900 bar are usually sufficient for thin-wall MABS applications, but machine-specific calibration is required. Hold pressure is started at 50 % to 70 % of peak injection pressure and then minimised by gate-seal time determined through part-weight stabilisation. Back pressure during screw recovery is maintained between 3 bar and 7 bar hydraulic, with screw speed between 50 rpm and 120 rpm on a 32 mm screw to avoid shear heating beyond the expected melt-temperature gain of 2 °C to 5 °C. Shear heating in the check ring and nozzle can increase melt temperature at high screw speeds; barrel set points should be reduced if measured nozzle melt temperature exceeds the front-zone setting by more than 5 °C.

Mould temperature is controlled separately for core and cavity. For mechanically neutral containers, 40 °C to 60 °C is adequate. For transparent parts produced with an SPI A-1 cavity finish, core and cavity temperatures are maintained between 60 °C and 80 °C to delay freeze-off and replicate the polish. Higher mould temperatures reduce haze but increase cycle time and cooling water demand. Uniformity across the cavity surface should be within ±5 °C; uneven cooling produces differential shrinkage and residual stress gradients that are visible as colour fringes under polarised light.

Mould shrinkage for this grade is typically 0.4 % to 0.7 % according to ISO 294-4 for 2 mm plaques; the actual value shifts with wall thickness, gate location, hold pressure and flow orientation. Gates should be located away from optical inspection zones and in the thickest section. Converging tunnel gates or edge gates with land lengths below 1.0 mm are preferred; a cold sprue bush with a reverse-taper cold well is used unless the hot runner is validated for MABS. Hot-runner systems must have fully balanced thermal profiles and no dead spots because residence times above 10 min at 250 °C create brownish discoloration and gel particle release. Because MABS is shear-thinning, thin-wall fill is optimised using high injection velocity with profiled transfer. The melt volume-flow rate of 22 cm³/10 min at 220 °C/10 kg is a single-point index, not a shear-rate-dependent viscosity function. Flow simulation should use pressure-volume-temperature data and cross-WLF viscosity coefficients from the producer, not the MVR value alone. Published data for this specific configuration is limited in open literature; the converter must request the current flow-analysis data set from LG Chem for accurate gate pressure prediction.

How Is MABS TR558A INP Differentiated from PMMA, SMMA, and Opaque ABS?

When compared with opaque ABS, the essential difference is optical: the methyl methacrylate comonomer and the refractive-index-matched polybutadiene phase reduce light scattering across the visible spectrum, permitting transparent articles with a haze level that would not be attainable with ordinary ABS. The transparency is achieved without eliminating the impact benefits of the grafted rubber phase. Opaque ABS can exhibit Charpy notched impact values similar to or slightly higher than MABS, but optical transmission is effectively zero and the product is unsuitable for diagnostic windows or transparent housings.

Relative to PMMA, the MABS grade sacrifices a small amount of surface hardness and long-term outdoor appearance because PMMA has higher scratch resistance and better UV weathering. PMMA also has higher tensile modulus and higher light transmittance, often above 92 % per ASTM D1003. The decisive difference is impact sensitivity: PMMA notched Charpy values per ISO 179-1/1eA are commonly below 5 kJ/m² at 23 °C, while the MABS value listed in the producer literature is above 15 kJ/m² at 23 °C. For snap-fit enclosures and sterile medical packaging subjected to drop loading, the higher notched impact of MABS reduces the probability of brittle failure.

Compared with styrene-methyl methacrylate copolymer, SMMA has high clarity and better resistance to some aqueous chemicals, but lower notched impact and lower practical toughness at stress concentrators. PC provides higher heat deflection temperature, typically above 120 °C under 1.8 MPa per ISO 75-2/A, and greater toughness, but requires melt temperatures near 280 °C to 320 °C and desiccant drying at 120 °C. MABS TR558A INP flows at lower melt temperature and fills thin-wall sections at lower injection pressure, but its heat resistance is lower and its chemical resistance to aromatic hydrocarbons, ketones and esters is limited.

Within transparent ABS materials, the bulk polymerisation route used for this grade reduces emulsifier residues and generally improves colour and water-blush resistance. Emulsion-grade transparent ABS may show higher haze after hot and humid exposure due to residual surfactant migration; the comparative magnitude is formulation-dependent and must be tested using ASTM D1003 after exposure to the intended service environment.

Regulatory Boundary Conditions for Healthcare and Consumer-Contact Applications

Material compliance is application-specific and requires current grade certificates from LG Chem or an authorised distributor. Under the EU RoHS Directive 2011/65/EU, including Delegated Directive (EU) 2015/863, converter documentation must demonstrate that restricted substances in homogeneous materials do not exceed the prescribed maximum concentration values. Under REACH 1907/2006/EC, Article 33 requires communication of substances of very high concern above 0.1 % w/w. Because additive packages and colourants can vary by production site, the grade should not be considered automatically compliant without a lot-specific supplier declaration.

For medical device applications, biological safety is evaluated under ISO 10993-1:2018 according to the nature and duration of body contact. The grade should not be assumed suitable for implantation or long-term tissue contact. Sterilisation compatibility must be validated with the final part because the resin has a Vicat softening temperature of 94 °C per ISO 306 and will distort in steam autoclave cycles above that temperature. Ethylene oxide and gamma irradiation may be practicable for short-contact devices, but dose-response and post-sterilisation optical and mechanical performance must be characterised according to ISO 11135:2014 or ISO 11137-1:2006. Repeated ethylene oxide cycles can reduce visible transmittance if the part is not fully degassed and can leave residues requiring compliance with ISO 10993-7:2008.

For food-contact or cosmetic-packaging use, the converter should request grade-specific migration and compositional statements. Published data for this specific configuration is limited; the supplier certificate should state the applicable food-contact regulation, if any, including the United States 21 CFR section or EU 10/2011 migration test condition. Without that certificate, the grade must not be used in direct food apposition.

Operational boundaries are set by heat resistance and solvent sensitivity. The Vicat softening temperature of 94 °C and the heat deflection temperature under 0.45 MPa of approximately 85 °C do not support continuous load-bearing service above 75 °C. Contact with ketones, esters, chlorinated solvents, aromatic hydrocarbons and strongly alkaline cleaners produces stress cracking or surface haze. Compatibility testing should use the actual moulded part, the actual chemical cleaner, and the actual residual stress state rather than coupon data alone. Chemical compatibility screening may follow ISO 22088-3 bent-strip testing at 0.5 % or 1.0 % strain, but the result is strongly affected by residual stress in the final part. The resin is not recommended for continuous exposure to acetone, methyl ethyl ketone, ethyl acetate, toluene, xylene, dichloromethane, or aqueous sodium hydroxide above 5 % concentration.

If ultrasonic welding is required, amplitude and weld time should be reduced relative to opaque ABS because the energy director melts rapidly and can produce visible flash or weld-line haze. The polybutadiene phase limits outdoor UV resistance; transparent UV protective topcoats or coextruded acrylic cap layers are required for prolonged outdoor use. Without additional stabilisation, yellowing and embrittlement may occur after accumulated UV exposure, although published xenon arc data for this specific grade is limited.

In production-scale troubleshooting, silver streaks are addressed first by confirming dryer dew point, hopper oxygen ingress and residual moisture, then by checking barrel temperature uniformity and screw recovery time. Yellowing is addressed by reducing hot-runner manifold temperature, removing dead spots and minimising residence time; the onset is accelerated above 250 °C and becomes severe above 260 °C. Surface haze in transparent parts is frequently caused by low mould temperature, poor cavity polish or premature gate freeze, not solely by material variability.