Fourteen questions that come up in almost every PA66 enquiry, answered with figures from our own grade sheets. Where price is concerned we explain the cost drivers rather than quoting numbers.
PA66 is a semi-crystalline engineering polyamide made from adipic acid and hexamethylene diamine. Its melting point of 252–265°C and stiffness are higher than PA6, it absorbs less moisture, and it resists creep and wear better — which is why it dominates thermal-break strips, engine-bay parts and connectors.
Unfilled PA66 sits at 1.13–1.15 g/cm³; 30% glass fibre raises it to about 1.36–1.38 g/cm³. Density drives cost per part on weight-priced mouldings, so a 5% density difference is a 5% material difference at the same volume.
PA66 melts at 252–265°C, roughly 40°C above PA6. The barrel has to run 30–50°C above the melting point for a stable melt, which is why PA66 machines need barrels rated for 290–300°C rather than the 250°C used for PA6.
Unfilled PA66 reaches 70–90°C HDT at 1.80 MPa; 30% glass fibre lifts it to 240–250°C. Design long-term load cases at roughly 70% of the HDT — continuous over-temperature shortens life through creep and oxidation rather than sudden failure.
PA66 takes up 1.0–1.5% in 24 hours, less than PA6 but far more than PPS (0.02–0.05%). Absorbed moisture swells the part slightly and lowers strength, so precision parts need conditioning or a tolerance allowance, and pellets must be dried before moulding.
Unfilled PA66 shrinks 0.8–1.5%; with 30% glass fibre it drops to 0.3–0.5%. Shrinkage is anisotropic — glass fibre orientation reduces shrinkage in the flow direction — so toolmakers should apply directional allowances rather than a single factor.
Unfilled PA66 tests at 75–85 MPa, 30% glass fibre at 180–210 MPa. Datasheet values are dry-as-moulded; conditioned parts read lower, and glass-fibre grades lose proportionally less because the fibre carries the load.
15%, 20%, 30% and 40% glass fibre are the standard steps. Stiffness, HDT and dimensional stability rise with fibre content while impact and flow fall, so thin-wall or long-flow parts usually step down one level and gain flow instead.
Yes — brominated, phosphorus (including red phosphorus) and nitrogen systems all reach V-0, and the rating is thickness-dependent (0.8 mm and 1.6 mm can differ for the same grade). Flame retardants cost impact strength and tracking resistance, so re-validate electrical properties after switching systems.
Dry PA66 at 90–110°C for 4–6 hours in a desiccant or vacuum dryer, targeting a dew point below −20°C. Under-dried resin shows silver streaks and bubbles; a hot-air oven is not enough in humid weather because it cannot push the dew point down.
Run the barrel at 260–290°C (250–270°C for flame-retardant systems) and the mould at 80–100°C, taking the upper end for thin walls and optical parts. Low mould temperature cuts crystallinity, which raises shrinkage and internal stress.
Four things: glass fibre or flame-retardant loading, colour, order quantity and the current adipic acid / HMDA market. A 30% GF grade and a V-0 grade are two cost steps above natural unfilled resin, so fix the performance requirement before comparing quotes. Send the application and monthly volume for a comparable offer.
PA66 wins above 100°C and where creep and dimensional stability matter; PA6 wins on toughness, flow and cost at ambient temperatures. PA66 melts 40°C higher and absorbs less water, which is why thermal-break strips and engine-bay parts are PA66 while clips, housings and cable protection are often PA6.
Thermal-break strips for aluminium windows (PA66 GF25), engine-bay brackets and covers, connectors, power-tool housings, gears, cable ties and appliance structures. The common thread is a part that carries load, sees heat and must keep its dimensions.
Send the part, the service conditions and your monthly volume — we will propose an equivalent grade, a sample and a quote.