Dongguan Qiantai PC/ABS FR-2 is a flame-retarded polycarbonate/acrylonitrile-butadiene-styrene alloy supplied in pellet form for injection molding and extrusion operations requiring UL 94 V-0 performance at a nominal wall thickness of 1.5 mm or greater. The grade is positioned between FR-1 and FR-3 in the manufacturer’s series: FR-1 provides lower melt flow and higher impact retention, while FR-3 is a higher-flow variant intended for thin-wall tooling. FR-2 uses a brominated flame retardant package with antimony trioxide synergist dispersed in a PC/ABS matrix. Vendor-published data indicate a melt volume-flow rate of 18 cm³/10 min at 260 °C/5.0 kg under ISO 1133-1:2022 and a density of 1.18 g/cm³ under ISO 1183-1:2019. The product is normally specified for AC adapters, industrial control housings, power distribution enclosures, and automotive interior electrical brackets where a defined balance of flow, stiffness, and flame retardance is required.

Property Profile and Standardised Test Data

The tensile yield of 54 MPa under ISO 527-2:2012 and flexural modulus of 2,350 MPa under ISO 178:2019 place FR-2 in the medium-stiffness range for flame-retarded PC/ABS. The notched Charpy impact of 40 kJ/m² at 23 °C under ISO 179-1:2010 is approximately 20 % lower than typical unfilled PC/ABS grades because the brominated package increases rigidity and reduces ductile tearing. The heat deflection temperature of 92 °C at 1.8 MPa under ISO 75-2:2013 supports use in power adapters that experience external hotspot temperatures below the softening transition. The comparative tracking index of 250 V under IEC 60112:2020 must be evaluated in circuits with creepage distances below the minimums required by IEC 62368-1:2018. Lot-to-lot variation in melt flow rate is typically controlled to ±2 cm³/10 min, but end-use qualification should use actual production lots.

Pre-drying is mandatory. The pellet absorbs moisture in humid air, and residual moisture above 0.02 % by Karl Fischer titration under ISO 15512:2019 causes hydrolysis of the polycarbonate phase, reducing molecular weight and producing splay marks on part surfaces. A desiccant dryer setpoint of 80 °C for 4 h with a dew point no higher than -40 °C is the minimum recommended condition. In plants with relative humidity above 60 %, regrind stored in open bins must be re-dried for 2 h before processing. Compounding line audits on co-rotating twin-screw extruders with L/D 40:1 and vacuum venting at -0.08 MPa are used to lower volatile residue; residual volatile content above 0.5 % can cause gate blush and delamination in thick bosses. The screw configuration for FR-2 typically includes two kneading blocks in the melt zone and one in the vent zone to break up antimony trioxide agglomerates without excessive shear. If the specific energy input exceeds 0.25 kWh/kg, melt temperature can cross 300 °C locally and initiate degradation of the brominated flame retardant; the resulting color shift to yellow-green is visible in natural pellets.

How Does FR-2 Differ from Unfilled PC/ABS and Non-Halogen Flame-Retarded Grades?

The comparison shows the trade-off produced by the halogenated chemistry. FR-2 reaches V-0 at 1.5 mm without the low notched impact of many non-halogen grades because the brominated/antimony system is efficient at lower loading than mineral-filled phosphorus-based systems. However, the tracking resistance falls to 250 V, and gas-phase flame inhibition produces acid gases and smoke release during forced combustion. Under ISO 5659-2:2017, brominated PC/ABS smoke density values are typically higher than those of unfilled PC/ABS; published data for this specific formulation is limited. Applications governed by rail-fire standards that set smoke density maxima should substitute a halogen-free grade only after full part-level testing.

Regrind can be re-used up to 20 % by weight without loss of V-0 certification, provided the regrind is not contaminated with polyolefin or acetal dust from shared granulators and is dried to the same moisture specification. Repeated heat histories above 260 °C reduce the molecular weight of the ABS phase, with a measurable decrease in notched Charpy after three cycles of 100 % regrind. The melt flow of aged regrind shifts upward by 2 cm³/10 min to 4 cm³/10 min per pass under ISO 1133-1:2022. For multi-cavity tools with long flow lengths, increased melt flow from regrind can shorten fill time but may also increase flash at parting lines if the clamp force is below 3 kN/cm² of projected area.

When Thin-Wall Electronics Housings Require V-0 at 1.5 mm

For a cavity wall thickness of 1.5 mm and flow length up to 120 mm, a hydraulic injection molding machine with a 20:1 L/D general-purpose screw can process FR-2 if barrel temperature profiles are held between 235 °C at the feed zone and 260 °C at the nozzle. The mold temperature should be set to 60 °C to 80 °C; lower mold temperatures increase frozen-layer thickness and require higher injection pressure, while higher mold temperatures extend cooling time and may allow sink marks opposite bosses. Injection velocity should be moderate to high, with a fill time of 0.8 s to 2.0 s for parts under 80 g. Hold pressure is typically 60 MPa to 80 MPa; hold-pressure time should be based on gate seal, which for a 1.5 mm cold edge gate occurs when the part mass no longer increases, usually after 4 s to 6 s.

In hot runner systems, the nozzle and manifold temperatures must not exceed 270 °C. Local hot spots above this threshold cause plate-out of brominated decomposition products on the shut-off needle, leading to gate leak and short shots. Supplier processing bulletins for halogenated PC/ABS grades recommend thermocouple placement within 3 mm of the gate tip and annual calibration against a standard reference thermocouple. A residence time at melt temperature above 260 °C beyond 5 min can produce yellowing and a loss of flame retardance at thin sections. During shutdown, the barrel should be purged with a low-viscosity PC or SAN purge material; purging with olefin-based materials can create a two-phase melt that retains brominated flame retardant residues and causes black specks in subsequent lots. Production records from 120-ton and 160-ton injection presses indicate that stabilising the process after a color change can require 10 to 15 shots before the V-0 rating stabilises.

FR-2 is supplied under a UL Yellow Card file that specifies the minimum thickness, color range, and maximum room-temperature ambient use for V-0 classification; substitution of pigments outside the recognized color series may invalidate the listed flammability rating. The brominated flame retardant system used in FR-2 is not classified as a polybrominated diphenyl ether or hexabromocyclododecane under current risk-management listings, but full substance disclosure should be obtained through the supplier’s REACH Article 33 statement for the specific shipment. Under RoHS Directive 2011/65/EU, the grade is accepted only when supplier test data confirm lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE below the maximum concentration values; the EU RoHS Directive does not eliminate all brominated flame retardants. For applications requiring halogen-free compliance under IEC 61249-2-21:2003, FR-2 is not suitable because the bromine content of the formulation exceeds the 900 ppm chlorine and 900 ppm bromine thresholds.

Chemical compatibility testing under ISO 22088-3:2016 for environmental stress cracking should be performed if FR-2 will contact cleaning agents, lubricants, or potting compounds. The polycarbonate phase is susceptible to stress cracking in the presence of aromatic hydrocarbons, ketones, esters, and some amine-based curing agents. In overmolding or sealing operations, epoxy formulations containing amine hardeners can cause localized softening and stress cracking at knit lines. Silicone-based release agents may be used on the tool surface, but over-application can transfer to the part and reduce paint adhesion. Painted FR-2 parts require flame adhesion testing after painting because the flame retardant package can migrate to the surface over time and reduce coating bond strength; adhesion should be verified using ISO 2409:2020 cross-cut test.

For incoming quality control, the certificate of analysis should report melt volume-flow rate under ISO 1133-1:2022, density under ISO 1183-1:2019, moisture under ISO 15512:2019, and lot traceability to the UL Yellow Card file. In production, shear-induced heating in a 20:1 L/D screw can raise melt temperature by 5 °C to 10 °C above the set barrel temperature at screw speeds above 100 min⁻¹; molders should measure actual melt temperature with an insertion thermocouple during first-article approval. If the actual melt temperature exceeds 270 °C, the screw speed or backpressure should be reduced; backpressure above 0.7 MPa can overheat the melt and increase residence time in the compression zone. Venting is critical because the brominated package generates volatiles at melt temperature; vents shallower than 0.02 mm may trap gas and cause burn marks. Vent land depths of 0.02 mm to 0.03 mm for PC/ABS are typical, with vent width 3 mm and spacing every 25 mm along the parting line. Corners should have a minimum radius of 0.5 mm to avoid stress concentrations; sharp internal corners reduce notched impact and can cause cracking at snap-fit bases.

In AC adapter housings that are assembled by ultrasonic welding, the joint design should use a shear joint with interference of 0.2 mm to 0.3 mm; energy director joints are less effective because the mineral synergist increases melt viscosity at the interface and can produce loose weld beads. Amplitude settings on 20 kHz ultrasonic welders are typically 30 µm to 45 µm, but part-specific trials are required. Pull-apart force after welding should be tested in accordance with the end-product standard, not the resin data sheet.

Relative to Dongguan Qiantai PC/ABS FR-1, FR-2 has a higher melt volume-flow rate and is preferred for multi-cavity and long-flow housings; FR-1 provides greater low-temperature notched impact and is more often selected for electrical enclosures with snap-fit arms. Relative to FR-3, FR-2 has lower melt flow and a higher heat deflection temperature, making it less suitable for wall thickness below 0.8 mm but better for parts that must maintain dimensions during elevated-temperature testing. The selection between these three grades should be based on the minimum UL 94 thickness on the Yellow Card, the required flow length-to-thickness ratio, and the end-product impact test specification, not solely on melt flow rate.