Toray Industries Toyolac ABS 700BK is a black-pigmented acrylonitrile-butadiene-styrene copolymer supplied in pellet form for injection moulding. The product belongs to the Toyolac 700 series, which occupies a medium-impact, high-flow position within the manufacturer’s ABS portfolio. Published datasheets for the 700 series list a density of 1.04–1.05 g/cm³ when determined in accordance with ISO 1183-1:2019, and a melt mass-flow rate of 21–24 g/10 min at 220 °C/10 kg using ISO 1133-1:2022. The BK suffix indicates carbon black pigmentation, which should not be treated as an inert colourant; carbon black can alter melt viscosity, moisture uptake, drying heat absorption, and surface appearance. Published data for the black-specific configuration is limited, and grade-specific certificates of analysis should be obtained before substituting 700BK for natural 700 resin in tool trials.

Typical mechanical performance data for the Toyolac 700 series, normalised to standard specimen geometries, are shown below. Values represent the natural or lightly stabilised series; black pigment at conventional loadings may shift values by ±5%, particularly in melt flow and impact.

The principal application for 700BK is injection moulding of thin-walled black components in consumer electronics, office automation, domestic appliances, and automotive interior subassemblies. The grade’s high melt flow permits filling of multi-cavity tools with flow length-to-thickness ratios above 150:1 at conventional injection pressures. Components such as bezels, connector covers, printer housings, vacuum cleaner shells, and dashboard sub-assemblies are representative applications cited in industrial material selection databases; however, published end-use test data for this specific black configuration is limited.

What Processing Constraints Govern Hot Runner Tooling for 700BK?

Pre-drying is mandatory when ambient storage relative humidity exceeds 60 % or when pellet moisture is not confirmed below 0.05 wt%. Desiccant dryers should maintain a dew point of at most −20 °C, with a drying setpoint of 80–90 °C for 2–4 hours depending on initial moisture load. The black pigment complicates visual moisture detection because carbon black masks early silver-streak formation. In production audits on black ABS grades, shot-to-shot gloss drift on visible surfaces has been observed before splay becomes obvious, particularly in tools with long hot-runner channels.

Melt temperature at the nozzle should be maintained between 200 °C and 250 °C. Residence time above 250 °C should be held below 10 min; in hot manifolds, residence time below 8 min is recommended. The unsaturated polybutadiene phase in ABS undergoes thermal-oxidative chain scission and crosslinking above 260 °C, producing volatile aldehydes and discolouration. On black surfaces, this degradation may present as a loss of gloss or a faint brown cast visible only under high-intensity light. Injection machines with 20:1 to 25:1 L/D general-purpose screws and compression ratios of 2.0:1 to 2.5:1 are suitable; high-compression screws above 3.0:1 may over-shear the carbon black and generate pigment streaks. Backpressure should be set at 5–10 MPa during screw recovery to disperse pigment and homogenise melt temperature. Backpressure below 5 MPa can leave carbon black agglomerates, while sustained backpressure above 15 MPa can shear-heat the melt and reduce impact through butadiene degradation.

Mould surface temperature for black cosmetic parts typically ranges from 30 °C to 60 °C. Raising the mould surface temperature to 60–80 °C reduces visible weld lines and improves gloss at the expense of longer cooling time. In a 1,200 kN clamp force machine, cavity pressures of 40–60 MPa are generally adequate for wall sections from 1.5 to 3.0 mm. Below 1.0 mm wall thickness, melt temperature should be shifted toward the upper limit and injection velocity should be increased to 250 mm/s or above for short-fill avoidance. Shot size should be controlled to 50–70 % of barrel capacity; smaller shot sizes increase residence time and larger shot sizes may create melt temperature heterogeneity.

Compared with high-impact Toyolac 100, the 700 series deliberately trades low-temperature impact for higher spiral flow. In the same black pigmentation, Toyolac 100 may deliver Charpy notched impact values 20–30 % higher than Toyolac 700, but its melt mass-flow rate is lower by a factor that depends strongly on the chosen grade. Toyolac 500 is situated between them, providing moderate flow and intermediate impact for cabinets and structural housings. The 700 series is therefore selected when thin-wall fill, cycle-time reduction, or multi-cavity balancing cannot be achieved with a high-impact grade. Compared with a natural 700 resin, 700BK eliminates separate masterbatch feeding and reduces colour metering variation; however, it removes from the moulder the ability to adjust carbon black content for specific opacity or weathering requirements.

When 700BK Replaces Natural ABS in Multi-Cavity Moulds

Replacement of natural 700 with 700BK in an existing tool requires re-validation of fill balance and gate freeze time. Carbon black can increase melt viscosity by 2–5 % depending on particle size and dispersion, which may shift cavity-to-cavity fill imbalance in tools with marginal runner balance. Pressure-drop measurements across the hot runner should be repeated at the intended melt temperature. In one production-scale audit of a 16-cavity black ABS tool, a 3 % shift in melt flow rate moved cavity-to-cavity weight variation from ±0.8 % to ±1.4 %, requiring a runner restrictor adjustment; such sensitivity is not always visible on short-shot studies unless the short shot is weighed.

Colour control for direct-use 700BK should be monitored spectrophotometrically rather than visually. Incoming lots can be compared using a D65 illuminant and 10° observer geometry with CIELab coordinates. Black ABS typically exhibits L* values below 30, but small changes in carbon black dispersion shift jetness and gloss more than a simple L* reading implies. Moulded plaques should be measured on identical texture and thickness; textured surfaces reduce instrumental gloss but can hide early pigment dispersion defects. Published limits for 700BK lot-to-lot colour difference are manufacturer-specific and should be embedded into the incoming inspection plan.

Regulatory Verification Points and Migration Boundaries

Compliance verification for 700BK should proceed against the specific lot safety data sheet. Under RoHS 2011/65/EU as amended by (EU) 2015/863, the homogeneous material is not expected to contain lead, mercury, cadmium, hexavalent chromium, PBB, or PBDE above maximum concentration values, but lot-level XRF screening according to IEC 62321 remains a standard receiving protocol. REACH obligations are addressed through supplier declarations under Article 33 of Regulation EC 1907/2006. The grade is not marketed as a food-contact material, and compliance with FDA 21 CFR 177.1020 must not be assumed for black-pigmented ABS without written manufacturer certification for the specific grade and colour.

In secondary finishing, adhesion of coatings and inks to 700BK requires surface treatment or solvent selection matched to the SAN surface. Black ABS is sensitive to aromatic hydrocarbons, ketones, and esters; incidental contact with such solvents can cause crazing or stress cracking. For ultrasonic welding, energy directors should be designed with a shear interference of 0.2–0.5 mm and a peak-to-peak amplitude appropriate for amorphous thermoplastics, typically 20–30 µm for unfilled ABS at 20 kHz, but joint strength depends on horn alignment and part geometry. Adhesive bonding with cyanoacrylates can be used for small joints, while two-part acrylics provide lower cure stress at the expense of longer fixture time.

Carbon black at conventional colorant loadings does not confer antistatic or static-dissipative properties. Surface resistivity remains in the insulating range above 10¹² Ω/sq unless a separately formulated anti-static or conductive ABS grade is used. Where flame retardance is required, 700BK is not a substitute for a flame-retardant ABS or PC/ABS grade. General-purpose Toyolac ABS grades are commonly rated HB at 1.5 mm under UL 94, but grade-specific UL Yellow Card data must be verified before product certification. The product should not be used for continuous outdoor exposure unless a weatherable ABS or ASA cap layer is employed, because the SAN matrix will undergo photo-oxidation and the polybutadiene phase will lose impact over time. Black pigmentation may improve initial UV screening relative to natural ABS, but it does not eliminate embrittlement in unpainted exterior applications.

Thermal conductivity of general-purpose ABS is approximately 0.17 W/m·K, which limits cooling rate in thick sections. The cooling time constant scales roughly with the square of wall thickness; moving from 2.0 mm to 3.0 mm can increase cooling-limited cycle time by more than 50 %. The linear coefficient of thermal expansion for unfilled ABS is on the order of 70–90 µm/m·K, which creates clearance allocation challenges in black exterior trims adjacent to metal components across a 60 °C temperature swing. In such assemblies, a geometric gap of at least 0.5 mm per 100 mm of length may be required depending on fixture fixity and thermal gradient.