The polycarbonate/acrylonitrile-butadiene-styrene compound Dongguan Zhongen PC/ABS T88G20BK is a black, 20% glass-fiber-reinforced injection-molding grade. The designation segment 20 identifies nominal glass-fiber content, and BK identifies the black color package. The product is applied in rigid structural components requiring higher stiffness, reduced thermal expansion, and improved heat deflection relative to unfilled PC/ABS. Because supplier-specific published data for the exact T88G20BK configuration may be limited, the numerical ranges in this technical note are representative of a 20% short-glass-filled PC/ABS class and must be confirmed against the Dongguan Zhongen certificate of analysis before production qualification. Primary test standards referenced for this material class include ISO 1183-1, ISO 527-2, ISO 178, ISO 75-2, ISO 180/A, ISO 1133-1, and ISO 294-4.

How Does the 20% Glass Loading Alter Mechanical and Thermal Performance?

In a 20% short-glass-fiber PC/ABS compound, the fiber network raises stiffness and load-bearing capacity but suppresses ductility. The failure mode changes from shear yielding in unfilled PC/ABS to fiber-matrix debonding and brittle tensile fracture. This property shift is the principal difference between T88G20BK and general-purpose PC/ABS. In tensile testing per ISO 527-2, the representative tensile modulus reaches 5,500–6,500 MPa, compared with 2,200–2,600 MPa for unfilled PC/ABS. Tensile stress at break is in the range of 85–100 MPa, but elongation at break drops to 2%–4%. Notched Izod impact at 23 °C under ISO 180/A is generally 8–12 kJ/m², while many unfilled PC/ABS grades absorb 35–50 kJ/m². The user should not specify T88G20BK for snap-fit geometries that rely on long-beam deflection or high-energy impact unless the design is ribbed and strain-limited.

The comparative values are class-representative, not lot-specific; the manufacturer’s certificate controls for production. The T88G20BK designation with 20% glass content provides higher modulus and heat deflection than a 10% glass-filled PC/ABS, but lower tensile elongation and lower notched impact.

Drying, Melt Temperature, and Injection Molding Parameters

Hydrolytic degradation of the polycarbonate phase occurs if the resin is processed with residual moisture above 0.02%. The material should be desiccant-dried at 80–100 °C for 3–4 h, with a drying-air dew point of -40 °C or lower. At plant relative humidity above 60%, open hoppers are insufficient; closed conveyors, dried regrind, and hopper dryers with insulated feed throats are required. Melt temperature at the nozzle should be maintained at 250–280 °C, and mold temperature should be 80–110 °C. A mold temperature below 80 °C reduces inter-laminar bonding at the surface and may produce glass-fiber read-through. The melt volume-flow rate measured at 260 °C/5 kg per ISO 1133-1 is expected to fall between 8 cm³/10 min and 15 cm³/10 min for this class.

For production-scale injection molding, a general-purpose screw with 20:1 to 25:1 L/D and a compression ratio of 2:1 to 2.5:1 is typical. The screw and barrel should be bimetallic or nitrided because glass fiber accelerates wear. Shot size should be 50%–75% of barrel capacity to avoid extended residence time. At melt temperatures above 300 °C or residence times beyond 5 min, PC/ABS degrades, producing brown streaks, splay, and impact loss. Injection speed should be moderate to high to maintain surface uniformity and minimize fiber orientation differences; however, excessive shear heating above 15,000 s⁻¹ can degrade the matrix. Back pressure of 0.3–0.7 MPa and screw speed of 30–80 rpm are common starting points. Injection pressure at the nozzle is typically 80–140 MPa, with holding pressure set to 50%–70% of peak injection pressure. Venting depths of 0.01–0.03 mm are required to prevent burn marks and gas traps. Capillary rheometry under ISO 11443 should be used to obtain viscosity coefficients for mold-filling simulation, because glass-filled compounds exhibit pronounced shear thinning and fiber orientation effects.

In electrical enclosures and structural brackets, T88G20BK is typically processed with clamp tonnage of 3–5 kN/cm² of projected area. The fiber orientation produced during filling yields anisotropic shrinkage: parallel shrinkage is 0.15%–0.35%, and perpendicular shrinkage is 0.35%–0.55% per ISO 294-4. Weld lines from multi-gate filling or holes reduce local tensile strength by approximately 30%–50% because the reinforcing fibers do not bridge the weld plane. Parts with snap-fits, bosses, or mounting tabs should be gated so the weld line is moved away from the primary load path. Production-scale observations on twin-screw compounded glass-filled PC/ABS show that poor fiber dispersion increases melt-pressure variation, can cause surface roughness, and can generate visible black flow lines. Rib thickness should not exceed 50% of nominal wall to avoid sink marks; boss outside diameter should be approximately 2× hole diameter. Surface gloss measured at 60° under ISO 2813 is typically 30–50 GU, lower than unfilled PC/ABS; visible tool surfaces are therefore textured to VDI 3400 reference 27–33 or coated with an elastomeric surface treatment when appearance is critical. Tool-cut adjustments for T88G20BK should be based on measured mold shrinkage on a prototype tool, not on generic unfilled PC/ABS shrinkage data.

When Dimensional Stability Under Load Is Required

The glass-fiber network lowers linear thermal expansion in the flow direction to approximately 0.35×10⁻⁴ K⁻¹ to 0.45×10⁻⁴ K⁻¹ under ISO 11359-2. Unfilled PC/ABS typically exhibits 0.7×10⁻⁴ K⁻¹ to 0.9×10⁻⁴ K⁻¹. Heat deflection temperature at 1.8 MPa is 115–125 °C, roughly 10–20 °C above unfilled PC/ABS. These properties suit enclosures near power electronics, under-hood interior mounts, and optical-mechanical chassis where dimensional change after thermal cycling must remain low. However, glass-filled PC/ABS has lower surface gloss and higher roughness than unfilled grades. The anisotropic orientation can also produce warpage on flat ribbed parts if the gate is not aligned with the dominant dimension. Mold-flow simulation should use fiber orientation tensor data from the compound supplier; isotropic mechanical assumptions are not sufficient for warpage prediction. Creep tests under ISO 899-2 may be required when load durations exceed 1,000 h at temperatures above 60 °C.

Compared with mineral-filled PC/ABS, T88G20BK provides higher tensile strength and lower density, but mineral-filled products may generate less warpage and lower formulation cost. Compared with PA66 GF30, the product absorbs much less moisture. Under ISO 62 at 23 °C and 50% RH, a 20% glass-filled PC/ABS class typically takes up 0.2%–0.4% moisture, whereas PA66 GF30 can reach 1.5%–2.0%. This difference reduces hygroscopic dimensional change and property drift in humid service. Compared with aluminum or zinc die-castings, the compound lowers mass and offers electrical insulation, but its tensile modulus is approximately 6,000 MPa, roughly an order of magnitude below die-casting alloys. Metal-replacement designs must therefore add ribs, gussets, or thicker sections and should be verified by finite-element analysis with fiber orientation data.

For compliance, finished articles made from T88G20BK require supplier declarations for Regulation (EC) No 1907/2006, Directive 2011/65/EU, and relevant UL 94 flammability ratings at the intended thickness. The material should not be considered food-contact or medical grade without migration testing under Regulation (EU) 10/2011 or FDA 21 CFR 177.1580. The product is not inherently UV-stabilized unless the black colorant package or additional stabilizers provide specific outdoor performance. Blending with amine-based additives or certain flame-retardant synergists is contraindicated because such agents can accelerate polycarbonate decomposition. Regrind should be limited to 20% or less in load-bearing parts, and regrind must be dried and free of fines and glass-fiber dust. Processing equipment and molds should be purged with a low-viscosity polystyrene or dedicated purge compound when switching from this glass-filled grade to avoid black specks and fiber carryover.