CHIMEI Zhangzhou ABS PA-707K is an amorphous acrylonitrile-butadiene-styrene terpolymer supplied as pellets for injection moulding of low-load enclosures, small appliance components, and non-loadbearing internal parts. The grade is classified within the Polylac portfolio as a high-flow general-purpose ABS; the classification is based on melt flow behaviour rather than ignition resistance or impact modification. Typical specific gravity is 1.04 when tested under ISO 1183-1:2019, and melt flow rate at 220 °C with a 10 kg load is usually reported between 22 g/10 min and 26 g/10 min under ASTM D1238-20, with lot-to-lot variation influenced by pigmentation. The polymer consists of a styrene-acrylonitrile continuous phase and a grafted polybutadiene rubber dispersion; the lower rubber content compared with high-impact ABS grades reduces melt viscosity and improves surface gloss potential when measured at 60° under ASTM D523-14 but limits energy absorption under sub-0 °C impact. Safety-data documentation references CAS 9003-56-9 and indicates screening for REACH SVHC and RoHS 2011/65/EU, but pellet-level regulatory statements do not transfer to finished articles. Where food-contact use is contemplated, article-level migration testing under EU 10/2011 or FDA 21 CFR 181.32 is required because the product is not supplied with a blanket food-contact certification.

What changes when a moulder selects PA-707K instead of a standard-flow Polylac grade?

The primary difference from PA-757 is melt viscosity: PA-707K fills thin sections at lower pressure and supports shorter cycle times in multi-cavity tools where flow-length-to-wall-thickness ratios exceed 150:1. In hot-runner systems with narrow gates, the lower viscosity reduces pressure drop through the gate land, but it increases the risk of drooling when hot-runner valve-pin seat wear exceeds 5 µm radial clearance or when decompression settings are not retuned. Compared with PA-757, the manufacturer typical notched Izod impact shifts to approximately 18 kJ/m² at 23 °C under ISO 180/1A, while standard-flow general-purpose grades may fall near 20–24 kJ/m²; the practical consequence is that snap-fit beams with high local strain should be revalidated. The grade is not a substitute for flame-retardant PA-765A: PA-707K is not rated UL 94 V-0 at 1.5 mm, and end-product vertical-burn assessments under IEC 60695-11-10 remain the responsibility of the manufacturer. Compared with high-impact PA-709, PA-707K has lower rubber content, lower sub-ambient ductility, and higher surface gloss potential in unpainted parts. Published data for this specific configuration is limited.

In high-volume injection moulding cells using hydraulic machines in the 1,200–3,000 kN clamp force class, PA-707K is processed after desiccant drying at 80 °C for 3–4 h to a residual moisture target below 0.1 wt%. Dryers should maintain a dew point of -40 °C or lower and deliver a closed-loop hopper feed; open hopper exposure above 60 % RH for more than 4 h requires re-drying. A general-purpose screw with 20:1–24:1 L/D, compression ratio 2.0:1–2.4:1, and check-ring clearance verified at each tool change is adequate. Melt temperature measured at the nozzle is typically 200–230 °C; sustained excursions above 250 °C accelerate rubber-phase degradation and yellowing. Mould temperature at the cavity wall should be 40–60 °C; values above 70 °C improve weld-line strength in some geometries but extend cooling time and increase sink depth in thick bosses. Back pressure is normally set at 5–15 bar, and screw rotation speed is adjusted so recovery time remains shorter than cooling time; if recovery exceeds 90 % of cooling time, melt supply becomes the cycle-limiting step. The processing table gives typical setpoint ranges, not universal limits.

Short-Term Mechanical and Thermal Property Indicators Under Laboratory Load Conditions

Typical values are reproduced from manufacturer technical data and are not specification limits; they may shift with colour, regrind, and test laboratory.

Application screening is appropriate for electronics accessory enclosures, toner cartridge housing panels, and small appliance covers where wall stock is 1.0–1.5 mm and the flammability rating can remain UL 94 HB at 1.5 mm. The grade can be filled at injection speeds of 30–100 mm/s; fill pressure should be limited to 70 MPa to avoid gate blush and flash. Because the notched Izod impact is comparatively limited, snap-fit geometry with outer-fibre strain above 2 % should be probed with prototype testing or finite-element analysis rather than direct material substitution. Continuous service above 70 °C under load is outside the typical design envelope because the SAN matrix undergoes creep and dimensional relaxation. Contact with methyl ethyl ketone, toluene, or chlorinated hydrocarbons can craze and embrittle surfaces; chemical compatibility should be verified under ISO 22088-3 or an equivalent method before commercial release.

When existing tooling is converted from lower-flow ABS, which processing discipline becomes critical?

Melt cushion, switch-over position, holding time, and decompression stroke must be revalidated because PA-707K fills at lower cavity pressure. If the cushion drops below 2 mm, the holding-pressure signal may not transmit through the screw tip and dimensional variation increases. In hot-runner tools, gate stringing can appear when valve-pin seat wear exceeds 5 µm radial clearance, particularly if decompression is retained from a lower-flow grade. Recovery behaviour should be monitored over at least 20 consecutive cycles; if recovery time falls below 30 % of cooling time, screw speed may be reduced to limit frictional heating, and if recovery exceeds cooling time, cycle time is controlled by plastication capacity. Ultrasonic welding settings should not be transferred unchanged from PA-757 tools because melt viscosity affects interfacial heating; weld amplitude and trigger force require production-fixture reoptimization. Published data for this specific configuration is limited.

Storage in unopened bags at 40–60 % RH and 15–30 °C is conventional. After 4 h of open-hopper exposure above 60 % RH, pre-drying is required because absorbed moisture reacts with nitrile functionality during plastication and produces surface splay, silver streaks, and molecular weight reduction. Regrind addition is typically limited to 20 wt% for cosmetic surfaces and 30 wt% for non-cosmetic internal parts; higher regrind levels reduce impact, increase black speck formation, and widen shrinkage. The material should not be blended with polyamide residues or metallic-soap lubricants above trace levels because such contamination can cause plate-out on cavity surfaces and weaken weld lines. If colouring with carbon black masterbatch on a 40:1 L/D twin-screw extruder is required, melt temperature should not exceed 240 °C and residence time should remain below 5 min to limit rubber-phase crosslinking and gloss loss. Release documentation should record lot number, melt flow rate, moisture content, and the standard used for each test; out-of-range results require review of drying, hold pressure, and gate-seal behaviour.

Melt Rheology and Screw Torque Behaviour Are Constrained by Barrel Temperature and Screw Recovery Demand

Because PA-707K is a high-flow grade, the feed-throat temperature should be kept low enough to maintain pellet friction and avoid premature melting; typical feed-throat settings range from 40 °C to 60 °C. Barrel compression and metering zones are set to achieve the target melt temperature. Frictional shear heating can raise melt temperature by 5–15 °C above the metering-zone setpoint at screw rotation speeds above 120 rpm, so high-speed recovery should be validated with an air-shot temperature measurement rather than assumed from barrel thermocouples. Screw torque is generally lower than with glass-filled or impact-modified grades, but torque spikes can indicate hopper bridging, check-ring sticking, or feed-throat blockage. Capillary rheometry at 220 °C, 230 °C, and 240 °C is recommended for lot acceptance when long flow paths or multi-gate filling are used; apparent viscosity at 1,000 s⁻¹ can help set initial injection speed but must be correlated with mould-filling trials. Published data for this specific configuration is limited.