Lotte Chemical ABS ST-100 is an unfilled acrylonitrile-butadiene-styrene injection-moulding grade positioned in commercial grade-selection documents as a heat-resistant ABS with a nominal Vicat softening temperature near 100 °C. The alphanumeric designation identifies the thermal classification rather than a filler system; no glass fibre, mineral reinforcement, or polycarbonate alloying is required to achieve the stated short-term heat resistance. In the manufacturer’s ABS range, ST-100 is placed above general-purpose ABS grades for hot-air tolerance and below polycarbonate/ABS alloys for continuous load at higher temperatures. The material is supplied as pre-compounded pellets in which a grafted polybutadiene rubber phase is dispersed in a styrene-acrylonitrile matrix. The continuous SAN phase governs stiffness, chemical resistance, and heat distortion, while the rubber phase provides impact-energy absorption. This two-phase morphology gives ST-100 a density close to 1.04 g/cm³ and distinguishes it from filled high-heat polymer grades that achieve thermal stability through mineral reinforcement.

How is ST-100 specified under current ISO and ASTM protocols?

Table 1 consolidates representative property ranges shown in commercial technical literature for Lotte Chemical ABS ST-100. These values are typical values, not specification limits, and are generated on injection-moulded specimens conditioned according to ISO 291 at 23 °C and 50 % relative humidity. A supplier certificate of analysis is required for a given production lot, particularly when the part is moulded from a specific colour concentrate or with added regrind.

Acrylonitrile content in the SAN matrix is the primary variable governing solvent resistance and thermal stiffness. In ST-100, the styrene-acrylonitrile continuous phase is adjusted so that the matrix glass transition is sufficient to maintain rigidity above 90 °C under low stress. The trade-off is melt fluidity: as the Vicat softening temperature rises from approximately 95 °C to 100 °C, the melt mass-flow rate under ISO 1133-1 can decrease by 30–50 % relative to a high-flow general-purpose ABS. That inverse relationship directly influences tooling, gate size, and cycle-time decisions. Compared with a high-impact ABS grade in the same product family, ST-100 may exhibit lower sub-zero impact but higher short-term thermal stiffness. The improvement is obtained through matrix modification rather than mineral filler addition; therefore the unfilled density remains close to 1.04 g/cm³ and the material does not produce the abrasive tool wear associated with glass-fibre-reinforced thermoplastics.

Injection Moulding Parameters, Screw Requirements, and Dryer Settings

Drying before moulding is mandatory. In desiccant-bed drying, a dew point of −30 °C and an inlet air temperature of 80 °C are used for a residence time of 2–4 h. The target residual moisture is 0.08 % by weight. When ambient relative humidity exceeds 60 %, drying time is extended to 4–6 h because ABS pellets can re-absorb surface moisture in unsealed hoppers and regrind feed streams. Residual moisture above 0.12 % principally affects surface quality and weld-line appearance; it does not hydrolyze the SAN backbone in the manner observed with polycarbonate or polyamide.

The plasticating unit used on production lines is typically a three-zone screw with a reverse-cut non-return valve to maintain shot-weight consistency. Barrel temperature profiles are set from 210 °C at the rear zone to 240 °C at the nozzle, with melt temperature verified by a pyrometer probe at 220–250 °C. Mould temperature is held at 40–80 °C; higher mould temperatures improve surface gloss and knit-line strength but extend cooling time. For a 2.0–3.0 mm wall section, initial injection speed is set at 60–100 mm/s, with pack pressure at 50–70 % of peak injection pressure and holding time determined by gate-seal studies. On a 1,200 kN clamp injection-moulding machine filling a 2.5 mm wall-thickness enclosure, short-shot conditions are commonly observed when cavity pressure falls below 35 MPa, while flash begins above 55 MPa. These values are machine- and part-specific and are not grade constants, but they provide a useful initial processing boundary.

Hot-runner tools require externally heated manifolds with thermocouple feedback in each zone. The allowed setpoint deviation in critical gate zones is ±1.5 K because the lower melt fluidity of ST-100 can produce slug formation in cold zones. If an internally heated hot-runner is used, local melt temperature at the tip may exceed the measured barrel setpoint by 15–20 K, pushing the material into the thermal degradation band. Gate diameters below 0.8 mm for a 2.0 mm wall section are not recommended at the lower end of the melt-temperature window. Melt residence time must be controlled: at melt temperature above 250 °C, gel particles can form after 10 min in the barrel, leading to black specks in natural parts. Regrind addition of 20 wt% is common in non-appearance parts; above 30 wt%, Charpy notched impact may fall by 5–10 % and melt flow may increase by 10–20 %. Closed-loop regrind fraction should be held within ±5 % to keep tensile yield stress within ±2 MPa.

When a housing design shifts from ambient exposure to sustained load at 80–95 °C

Short-term Vicat values do not guarantee creep resistance. The heat-distortion temperature under 1.8 MPa for ST-100 is in the range of 88–95 °C, and continuous service temperature should remain at least 10–15 K below that value when load-bearing ribs or bosses are present. In an electronics enclosure where an internal heat spreader raises local air temperature to 85 °C, the material is generally appropriate for nonstructural snap-fit panels at low stress, but published data for this specific configuration is limited. Load-bearing bosses exposed to 0.45 MPa flexural stress should be validated by thermal cycling according to ISO 16750-4 or an equivalent OEM test profile. The difference between ST-100 and a general-purpose ABS is most evident in this regime: at 80 °C, a lower-heat grade may show visible sink marks at a 0.1 mm tolerance, while ST-100 typically holds tolerance under the same short-term condition if moulded at the upper end of the mould-temperature range.

Applications listed in commercial selection guides for heat-resistant ABS include ventilation housings, electric-kettle skirts, power-tool motor housings, and rear lamp brackets where local radiant heat exceeds 80 °C but does not exceed 100 °C. The selection criterion is often the Vicat B50 value of 100 °C; if the part must tolerate continuous temperatures above 100 °C, a PC/ABS alloy or heat-resistant ASA/ABS is substituted. The polymer does not provide intrinsic UV stabilization for exterior use; unpigmented ABS exposed to sunlight loses gloss and embrittles because of polybutadiene oxidation at the part surface.

What boundaries apply to outdoor, chemical, and flame-retardant use?

ABS is not inherently weather-resistant. Outdoor use of ST-100 in direct sunlight requires capping, painting, or UV-stabilized alloying. If a part is evaluated under xenon-arc radiation according to ISO 4892-2, the end-user must obtain grade-specific data from the supplier; the base ABS is not a long-term exterior resin. Chemical resistance is similarly bounded. The polymer shows resistance to dilute aqueous acids and alkalis at 23 °C, but aromatic hydrocarbons, esters, and ketones attack the SAN phase and can cause stress cracking. Contact with plasticised PVC gaskets should be avoided in design because phthalate migration reduces interfacial glass transition temperature. If cleaning-agent compatibility is evaluated by immersion according to ASTM D543-21 for 7 days, acetone and toluene produce visible surface softening, while ethanol and 10 % sodium hydroxide typically produce a mass change below 0.5 %. For flame-retardant applications, the base ST-100 grade is not a V-0 solution. When a housing must meet UL 94 V-0 at 1.5 mm, a dedicated flame-retardant ABS is specified. The use of halogenated additives to upgrade the base grade is not recommended without full compounding and property validation.

Regulatory compliance is batch- and colour-specific. The base polymer is expected to satisfy RoHS Directive 2011/65/EU for lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and polybrominated diphenyl ethers at the 0.1 % homogeneous-material threshold for lead and 0.01 % for cadmium. REACH Candidate List substances above 0.1 % by weight per Article 33 of Regulation (EC) No 1907/2006 should be confirmed for the specific production lot. Food-contact status under FDA 21 CFR 177.1020 or Commission Regulation (EU) No 10/2011 is not automatic for every colour or lot; compliance must be obtained in writing for the exact grade and pigment package. Incoming lots should be tested under ISO 1133-1 before tool transfer to a new production line because lot-to-lot melt-flow variation within ±1.0 g/10 min can shift fill pressure in thin-wall sections.