WWJF-8023

WWJF-8023 is a solid phosphorus–nitrogen flame retardant supplied as a free-flowing, off-white powder in the manufacturer’s 8000 series for halogen-free engineering thermoplastic compounds. The model designation separates it from WWJF-8021, which has a lower decomposition onset and is limited to polyamide 6 compounds processed below 280 °C, and from WWJF-8025, which is tailored to polyesters requiring lower phosphorus content to preserve elongation at break. Lot-release specifications include phosphorus at 23.5–24.5 wt% determined by inductively coupled plasma optical emission spectrometry after closed-vessel microwave digestion, nitrogen at 8.0–9.0 wt% by Kjeldahl digestion, residual moisture at ≤0.30 wt% by ASTM D789-19, bulk density at 0.55–0.70 g/cm³ by ISO 60, and pH of a 10% aqueous slurry at 6.5–7.5 by ISO 787-9. The 5% mass-loss temperature measured under nitrogen at 10 K/min according to ISO 11358-1 is 385 °C. Particle size distribution by laser diffraction per ISO 13320:2020 gives a D50 of 15 µm and a D90 of ≤35 µm. The product is used primarily in glass-fibre-reinforced polyamide 66 and polyamide 6 compounds where a UL 94 V-0 rating is required at 0.8 mm wall thickness without halogenated synergists. Because WWJF-8023 is a proprietary formulation, independent peer-reviewed data for this exact product is not publicly available; the thresholds reproduced here are manufacturer lot-release values and must be confirmed on the target production line.

How Does the 385 °C Decomposition Onset Constrain Twin-Screw Compounding?

The compounding window for WWJF-8023 is bounded by the melt temperature required for complete dispersion and the onset of thermal degradation at 385 °C. On a co-rotating twin-screw extruder with an L/D ratio of 40:1 or 44:1, barrel settings from the feed throat to the die are typically 250–280 °C. The melt temperature measured by an immersion thermocouple at the die must not exceed 310 °C; the safe operating band is 305–315 °C, and excursions above 315 °C for more than 30 s produce acidic degradation products that accelerate PA66 chain scission. Residence time above 300 °C is kept below 45 s. Screw configurations using two or three kneading blocks downstream of the side feeder, followed by a left-handed element before atmospheric venting, reduce the D50 of the dispersed additive in the final compound to below 5 µm when a water-cooled strand pelletising line is used. Die pressure is maintained at 35–55 bar to minimise volatile formation. On a 75 mm twin-screw extruder operating at 350–450 kg/h, torque-specific energy is 0.22–0.28 kWh/kg. Capillary rheometry at 290 °C shows a melt viscosity of 340–390 Pa·s at a shear rate of 1000 s⁻¹ for a PA66 GF30 compound containing 22 wt% WWJF-8023, compared with 290–330 Pa·s for the same compound without flame retardant. If throughput exceeds 450 kg/h, the melt temperature can exceed 315 °C; the product should then be pre-dispersed in a carrier resin at 30 wt% before final compounding.

A PA66 grade containing 30 wt% glass fibre and 22 wt% WWJF-8023 achieves UL 94 V-0 at 0.8 mm after 48 h conditioning at 23 °C and 50% relative humidity. Total afterflame times for five specimens are 10–25 s depending on regrind ratio. Comparative tracking index measured according to IEC 60112 is 600 V for the same compound. Glow-wire flammability at 750 °C on 1.5 mm plaques gives no ignition within 5 s, and the material meets the 850 °C glow-wire ignition temperature requirements for unattended appliances under IEC 60695-11-5. In polyamide 6 compounds, the addition of 25 wt% WWJF-8023 with 25 wt% glass fibre yields V-0 at 1.6 mm, while 0.8 mm V-0 performance is less consistent and requires 2 wt% of a char-promoting phenolic resin to stabilise char cohesion. The product is not recommended for polyolefins, where phosphorus migration to the surface is observed after 500 h at 85 °C and 85% relative humidity by Fourier transform infrared attenuated total reflectance.

Comparative Flame-Retardant Loading and Electrical Tracking Data

The loading required to reach UL 94 V-0 in 0.8 mm PA66 GF30 is system-specific. Table 1 compares systems available for the same compound.

If Compound Moisture Exceeds 0.10 wt% Before Injection Molding

WWJF-8023 absorbs moisture during storage. Equilibrium moisture at 23 °C and 50% RH is 0.8 wt% after 72 h; at 85% RH the equilibrium value reaches 1.5 wt%. Injection molding of compounds containing the product should be preceded by drying to ≤0.10 wt% moisture in the compound, typically at 80–90 °C for 4–6 h using a desiccant dryer with a dew point of −30 °C or lower. In hot-runner systems, molten material held at 300 °C for more than 10 min shows a 15% reduction in phosphorus content at the gate due to acidic hydrolysis, as determined by energy-dispersive X-ray spectroscopy on cross-sectioned sprues. Hot-runner nozzle tips with internal dead zones should be avoided. The product is incompatible with calcium stearate, which accelerates acid release at melt temperatures above 290 °C and reduces UL 94 V-0 performance from 0.8 mm to 1.6 mm. It is also incompatible with amine-functional silane coupling agents above 0.5 wt%, which can promote premature char formation in the feed zone.

Typical production-scale use cases include injection-moulded electrical connectors, miniature circuit breaker housings, and electric motor end caps. In a 120 kN injection moulding machine producing connectors with wall sections of 0.8 mm, a compound containing 22 wt% WWJF-8023 in PA66 GF30 was moulded at a barrel temperature of 285 °C, mould temperature of 90 °C, and injection pressure of 900 bar. The moulded connectors showed no visible exudation after 1,000 h at 85 °C and 85% RH, and the comparative tracking index after conditioning remained 600 V per IEC 60112. In a 350-ton machine used for circuit breaker housings with wall sections from 1.0 mm to 2.5 mm, the feed throat was fitted with a water-cooled jacket to prevent bridging of the powder additive when a 30 wt% glass-fibre PA66 premix was used. Hopper residence time was kept below 30 min at 23 °C and 45% RH to avoid compaction. Lot-to-lot variance in the product’s D50 can shift the required loading by 1–2 wt% to maintain V-0, so in-line torque monitoring is recommended during the production run.

Under the REACH regulation, the base substance registered for WWJF-8023 is listed with a tonnage band of 1,000–10,000 t/a; the product contains no substances of very high concern above 0.1 wt%. The product meets the lead, mercury, cadmium, hexavalent chromium, PBB and PBDE restrictions in EU RoHS Directive 2011/65/EU Annex II. For electrical and electronic equipment housings, the compound using 22 wt% WWJF-8023 in PA66 GF30 can be classified as halogen-free according to IEC 61249-2-21, with total chlorine and bromine below 900 ppm each and total halogen below 1500 ppm. The product is not intended for food-contact applications. If a compound containing WWJF-8023 is specified for toys, the relevant migration limits must be assessed under EN 71-3; no independent migration study is provided for the product.

Revalidating UL Yellow Cards After Switching from Melamine Polyphosphate

Because melamine polyphosphate and WWJF-8023 differ in phosphorus content, acid-release mechanism, and char morphology, a drop-in substitution is not normally acceptable for existing UL listings. A change from 30 wt% melamine polyphosphate to 22 wt% WWJF-8023 may require re-testing at 0.8 mm and 1.6 mm under UL 94, a new comparative tracking index determination per IEC 60112, and glow-wire ignition temperature data per IEC 60695-11-5. The UL Yellow Card for the existing compound is invalid if the additive chemistry changes outside the permitted variation in the UL procedure. In addition, mechanical properties should be compared. The WWJF-8023 system usually improves tensile elongation at break by 8–15% relative to melamine polyphosphate at equal V-0, as measured by ISO 527-2/1A on injection-moulded Type 1A specimens, but it may reduce Charpy notched impact strength by 5–10% per ISO 179-1/1eA. These differences are attributed to the smaller particle size of WWJF-8023. Processors should run a full injection-molding capability study on the target mould, including short-shot analysis and gate freeze-time measurement, before switching commercial production.

What Certificate-of-Analysis Limits Apply to Each Lot of WWJF-8023?

Table 2 lists the lot-release parameters and test methods.

The product is supplied in 25 kg multi-wall paper bags with a polyethylene liner. Shelf life is 24 months in unopened bags stored at 10–30 °C and relative humidity below 60%. Opened bags should be resealed and consumed within 14 days. Storage on pallets exposed to direct floor moisture can raise the powder moisture content above the certificate limit even when the bag is sealed.