CHIMEI PA-717C is an unfilled injection-moulding grade of acrylonitrile-butadiene-styrene produced by Chi Mei Corporation. The grade is classified under ISO 1043-1:2011 as ABS, which denotes a moulding compound with a styrene-acrylonitrile continuous phase and a polybutadiene rubber dispersed phase. The supplier positions PA-717C for high-gloss, thin-wall components that require a longer cavity flow length than medium-flow ABS grades. The material is supplied as cylindrical pellets, and no halogenated flame-retardant system is included in the base resin. Colour concentrates, processing aids, or regrind additions can shift melt viscosity, notched impact, and surface appearance, and therefore each production recipe must be qualified separately.

Representative datasheet values published by the supplier include a melt mass-flow rate of 2.5 g/10 min at 220 °C with 10 kg load under ISO 1133-1:2022, a tensile stress at yield of 46 MPa at 50 mm/min under ISO 527-2:2012, a flexural modulus of 2300 MPa under ISO 178:2019, a notched Izod impact of 18 kJ/m² at 23 °C under ISO 180/A:2023, a heat deflection temperature of 88 °C at 1.82 MPa under ISO 75-2/A:2020, a Vicat softening temperature near 98 °C under ISO 306/B50:2022, and a density of 1.04 g/cm³ under ISO 1183-1:2019. Mould shrinkage is typically reported in the range 0.4–0.7 % under ISO 294-4:2018. The flammability rating is generally HB at 1.5 mm under UL 94, but the recognised component listing can change with colour, thickness, and regrind content.

The following table summarises commonly cited property bench marks for the unfilled natural grade. The values are supplier typicals, not lot-specific acceptance limits, and they are generated on standardised specimens rather than end-use parts.

How Should PA-717C Be Dried and Processed to Retain Impact?

Pre-drying in a desiccant hopper dryer should be carried out at 80 °C for 3–4 h to bring residual moisture below 0.02 % by weight. Dryers should be fitted with a dew-point monitor on the drying air; desiccant-wheel units with a drying-air dew point of −40 °C or lower are appropriate, whereas compressed-air membrane dryers may not maintain sufficiently dry conditions in high-humidity plants. If pellets are left in an open hopper at ambient relative humidity above 60 %, they should be re-dried before moulding. Karl Fischer titration at 160 °C is more reliable than a gravimetric moisture balance for verifying moisture below 0.02 %.

Barrel temperature profiles from the rear zone to the nozzle are normally maintained between 200 °C and 240 °C. The nozzle is often kept at 220–230 °C to balance drool against cold-slug formation. Melt temperature should not exceed 250 °C, and total residence time in the barrel should remain below 5 min. Above this boundary, the unsaturated butadiene phase undergoes thermal oxidative degradation, leading to yellowing, an increase in thermoplastic odour, black specks, and a measurable loss in notched Izod impact. Mould temperature is usually held between 40 °C and 60 °C; higher temperatures improve knit-line strength and surface gloss but extend cycle time and can produce sink marks near thick bosses if the hold-pressure profile is not re-optimised.

Reciprocating screw injection moulding machines with a three-zone screw of 20:1 to 24:1 L/D and compression ratio of 2.0:1 to 2.5:1 are suitable for the neat resin. Shot size should be between 30 % and 70 % of barrel capacity to avoid excessive residence time or poor melt uniformity. Back pressure is typically set in the hydraulic range of 5–15 bar to homogenise the melt without excessive frictional heat. Hot-runner manifolds should be thermally balanced within ±3 °C across all drops; unbalanced heat profiles create differential viscosity between adjacent cavities, resulting in gloss variation, warpage, and sink. Vent depths on parting lines should be 0.02–0.03 mm; insufficient venting produces gas burns at the end of fill, while excessive venting produces flash at normal packing pressures.

For high-gloss surfaces, cavity pressure at switchover is a more reliable control variable than injection time alone. A properly configured process often uses fill-to-pack transfer at 95–98 % of visual fill, followed by a packing-pressure profile that maintains cavity pressure until gate freeze. The gate-freeze time can be found by increasing hold time stepwise and recording part mass until no further increase occurs. In production, if the process drift exceeds ±2 % in part mass, the material lot, moisture, or check-ring wear should be investigated. On large flat parts, unbalanced cooling produces post-ejection warpage that can exceed 0.5 mm over a 300 mm span; conformal cooling or targeted baffle inserts may be required.

Property Benchmarks and the Flow–Impact Trade-Off

The flow position of PA-717C places it between CHIMEI PA-757 and PA-747 in the supplier’s ABS range. PA-757 is a medium-flow general-purpose grade with higher impact and similar high-gloss capability; PA-747 is lower-flow, higher-impact, and is also used in sheet extrusion. In thin-wall tooling, PA-717C reduces short shots and injection pressure relative to PA-757, but the flow improvement is obtained through a shift in the rubber-phase population and SAN matrix molecular weight, which produces a lower notched Izod value. The exact difference varies with colour and lot; comparative flow-spiral data should be generated on the target mould because published data for this specific configuration is limited. On the shop floor, the trade-off appears as fewer end-of-fill defects in ribs and grilles, but a higher sensitivity to sharp-corner fractures during ejection or assembly.

Users should not treat laboratory mechanical data as design allowables. The heat deflection temperature of 88 °C at 1.82 MPa is a short-term thermal deformation indicator, not a continuous-use temperature. Under sustained load at elevated temperature, creep and stress relaxation in the styrene-acrylonitrile matrix dominate dimensional response. For load-bearing parts, a creep rupture test under the maximum service temperature and load should be performed. Low-temperature impact data for PA-717C at sub-zero conditions are not consistently published; if ductility below −20 °C is required, PA-747, a high-rubber grade, or a PC/ABS blend should be evaluated instead.

Regrind management affects property retention. When PA-717C runners and sprues are reintroduced, the regrind fraction should be kept at or below 20 % of the total shot weight. Regrind should be re-dried and screened through a 2 mm mesh to remove fines before reintroduction, because fines can char and appear as black specks in high-gloss surfaces. If regrind fraction exceeds 20 %, melt viscosity may increase due to crosslink formation in the butadiene phase, and notched impact may fall below the lower acceptance limit.

If Thin-Wall High-Gloss Enclosures Are Being Evaluated

PA-717C is used in injection-moulded television bezels, monitor frames, audio front panels, small household appliance housings, vacuum cleaner shrouds, and power-tool casings. In these applications, the grade is selected where UL 94 HB at 1.5 mm is acceptable and where polished-cavity gloss can replace post-mould painting. Wall sections as low as 1.0 mm are feasible when the gate location is placed to minimise flow path and when the flow front reaches the last fill point before the melt cools to the solidification temperature. For panels with a flow length above 250 mm, filling simulation should be used to verify pressure drop, shear rate at the gate, and weld-line placement.

Tool surfaces should be free of micro-scratches because the grade does not hide surface defects. Draft angles should be at least 0.5° for textured surfaces and 0.25° for polished surfaces. Gate locations should be positioned away from visible surfaces where possible; direct gates on the front face often produce jetting or gate blush. In high-humidity moulding areas, mould sweating occurs when the mould surface temperature is below the plant dew point. The resulting water marks and flow lines are frequently mistaken for resin defects; the problem is controlled by raising the mould temperature above the dew point or by dehumidifying the clamp-side air. For painted or metallised components, the moulded surface should be inspected for surface energy after an isopropanol wipe; poor wetting is usually caused by mould release agents, grease, or excessive silicone from tool maintenance.

Table 2 lists the regulatory references most often requested for ABS moulding compounds. A supplier declaration remains necessary for each production lot, because the injection moulding plant is responsible for contamination control and for documenting any regrind, colour concentrate, or processing aid added on-site.

In high-gloss ABS moulding, jetting and weld lines are a common production bottleneck. For PA-717C, reducing injection speed at the gate and increasing mould temperature often reduce jetting, but both actions increase cycle time. A more stable solution is to locate the gate so that the melt fills a core or step before entering the visible flat surface. Batch-to-batch variation in colour and impact can be amplified by high regrind ratios; the regrind ratio should therefore be fixed after process validation and documented in the production record.

The material is incompatible with PVC contamination. Even small PVC residues in the hopper or granulator produce hydrogen chloride at ABS processing temperatures, causing tool corrosion, acid odour, and black charred particles. PA-717C should not be dry-blended with polycarbonate pellets without a compatibilised PC/ABS formulation, because direct hopper blending produces delamination, poor surface appearance, and non-homogeneous mechanical properties. The base grade has limited inherent weatherability and will yellow under ultraviolet exposure unless a UV-stabilised variant, co-extruded capstock, or painted surface is specified; weathering evaluation is typically performed under ISO 4892-2:2013 with exposure cycles relevant to the intended geographic location. Aromatic hydrocarbons, ketones, esters, and chlorinated solvents should be excluded from cleaning operations and end-use environments, because environmental stress cracking can occur in moulded parts even below the tensile yield stress of the resin.