ISO-TECH ISO-MID PA 12 is a semi-crystalline polyamide 12 compound supplied as pelletized feedstock for injection molding and profile extrusion. The material is designated PA12 under ISO 1043-1:2011 and is controlled by the manufacturer’s certificate of analysis for density, melt volume-flow rate, residual moisture, and tensile properties. Published product-specific data for the ISO-MID formulation remains limited; the numerical ranges referenced below are representative unfilled PA12 injection and extrusion grade values measured under ISO 527-1/-2, ISO 1183-1, ISO 62, ISO 1133-1, and ISO 11357-3. Incoming inspection of ISO-TECH ISO-MID PA 12 typically applies a density window of 1.01–1.04 g/cm³, a melt volume-flow rate at 235 °C and 5 kg of 8–20 cm³/10 min, and a dried pellet moisture content below 0.10% by mass. The polymer occupies a processing niche between short-chain PA6/PA66 and long-chain PA11: lower amide group density produces saturated water absorption near 1.5% by mass, reducing hygroscopic dimensional movement and stabilizing electrical surface resistance in humid production environments.

What Differentiates ISO-MID PA 12 from PA 6 and PA 66 in Moisture-Conditioned and Low-Temperature Service?

The distinction is rooted in the C12 aliphatic repeat unit. A longer methylene sequence lowers the concentration of hydrogen-bonding amide groups, reducing equilibrium moisture uptake relative to PA6 and PA66. Under ISO 62 saturation at 23 °C in water, unfilled PA12 typically reaches 1.5% by mass, whereas PA6 reaches 9.5–10.0% and PA66 reaches 8.0–9.0%. At 23 °C and 50% relative humidity, PA12 attains approximately 0.7–0.8% moisture, while PA6 and PA66 reach approximately 2.5–3.0%. This differential changes part dimensions, tensile modulus, and impact behavior. The lower dry tensile modulus of PA12, commonly 1400–1600 MPa, relative to PA6 at 2500–3500 MPa and PA66 at 2700–3300 MPa, is a design trade-off: rigidity is sacrificed for lower hygroscopic expansion, lower density, and higher elongation at break. At –40 °C, PA12 retains more impact ductility than dry PA66 in many unfilled systems; notched Charpy impact values for conditioned PA12 are commonly reported between 6 kJ/m² and 12 kJ/m², while dry PA66 values may be 3–5 kJ/m². The melting temperature of PA12 is 175–180 °C, which limits continuous service above 80–100 °C unless the grade is glass-fiber reinforced.

Compared with PA11, PA12 displays a melting point approximately 10–15 °C lower and a slightly narrower processing window. Compared with PA610 and PA1012, PA12 typically exhibits lower water absorption but also lower modulus; the selection is governed by dimensional tolerance, chemical exposure, and low-temperature impact requirements.

Melt-Processing Requirements, Screw Geometry, and Drying Limits

Before melt processing, ISO-TECH ISO-MID PA 12 must be dried in a desiccant dryer with a dew point at or below –30 °C. Drying at 80 °C for 4–8 h normally reduces residual moisture from sealed-bag levels to below 0.10% by mass. A hot-air tray dryer is not sufficient when ambient relative humidity exceeds 60%, because PA12 equilibrium moisture at 50% RH is 0.7–0.8% and diffusion from the pellet core is slow below 80 °C. Residual moisture above 0.15% at melt temperatures above 230 °C leads to hydrolytic chain scission, observed as a drop in melt viscosity, silver streaks, and reduced tensile elongation.

On a conventional reciprocating-screw injection molding machine with a three-zone general-purpose screw of 20:1 to 25:1 L/D and compression ratio 2.0:1 to 2.5:1, barrel temperatures from feed to nozzle are typically 210–230 °C, 235–250 °C, 240–255 °C, and 230–250 °C. Mold temperature is set at 30–80 °C. Lower mold temperatures reduce cycle time but produce lower crystallinity and higher post-mold shrinkage. Higher mold temperatures near 80 °C improve dimensional stability and reduce internal stress in snap-fit geometries. Hold pressure is typically 50–80% of the first-stage injection pressure; hydraulic injection pressure commonly falls between 60 MPa and 100 MPa depending on flow length and wall thickness. Back pressure is maintained at 0.3–0.7 MPa hydraulic to ensure melt homogeneity without excessive frictional heat. Melt residence time at 250 °C should not exceed 10–15 min; beyond this window oxidative degradation can increase yellowness index and lower notched impact strength. If interruption occurs, the barrel is purged with a low-viscosity polyolefin or a dedicated purging compound, not with PVC or acetal, because acid buildup can accelerate degradation of polyamide.

Profile extrusion uses a single-screw extruder with 24:1 to 30:1 L/D, a 3:1 compression ratio, and barrel zones from 190–210 °C at the feed throat to 230–250 °C at the die. Melt temperature measured by an immersion thermocouple should remain between 230 °C and 250 °C. A melt pump between screw tip and die reduces surging and controls wall thickness in pneumatic tubing. Vacuum venting at –0.8 bar gauge is recommended if regrind content exceeds 20%, because recycled flake can carry surface moisture. Regrind levels above 30% can raise melt viscosity fluctuations and increase tube ovality. Die land length and drawdown ratio must be adjusted for PA12’s higher die swell relative to PA6; published values for die swell in unfilled PA12 depend on shear rate, but die diameter is commonly sized 5–10% smaller than final outer diameter when a vacuum calibration tank is used.

Capillary rheometry on unfilled PA12 at 235 °C shows shear-thinning behavior with apparent viscosity falling from approximately 800–1200 Pa·s at 100 s⁻¹ to 150–250 Pa·s at 1000 s⁻¹. These are representative ranges; lot-specific curves should be generated on a capillary rheometer with a 1 mm diameter die and 20:1 length-to-diameter ratio. The flow-length-to-wall-thickness ratio for unfilled PA12 is typically limited to 200:1 at 1 mm wall and 260 °C. Thin-wall connectors below 0.75 mm wall thickness may require fast injection velocities above 150 mm/s screw speed and melt temperatures near 250–260 °C, but this narrows the residence-time window. Shear rates above 10,000 s⁻¹ in gate lands produce melt fracture and surface haze; gate diameters below 0.5 mm should be avoided unless a hot-runner system with independent nozzle heating is used.

Across automotive fluid-handling and industrial automation applications, ISO-TECH ISO-MID PA 12 is processed into pneumatic tubing, fuel-vapor lines, cable sheathing, and quick-connect housings. In coiled pneumatic tube production, lower moisture uptake helps maintain outer diameter and roundness after conditioning cycles at 23 °C and 50% RH for 168 h. Resistance to zinc chloride stress cracking is not absolute; stressed snap-fit connectors exposed to zinc chloride road de-icer have exhibited stress crack initiation at outer fiber strain above 1.0–1.5% in PA12 grades. Snap-fit retention features therefore keep maximum fiber strain below 1.0% or use radiused corners with at least 0.5 mm radius to reduce notch sensitivity. In cable harness conduit, PA12 offers lower specific density than PA66. At a wall thickness of 0.5 mm, the mass per meter of PA12 convoluted tube is about 15–20% lower than PA66 tube of equal outer diameter, assuming a density difference of about 0.10 g/cm³.

For selective laser sintering or film applications, ISO-MID PA12 powder or sheet variants, if supplied, require separate specifications; this description addresses only pelletized injection and extrusion grades. Published data for this specific configuration is limited, so part qualification must include verification of tensile properties, heat deflection temperature under ISO 75-1/-2, and impact behavior on specimens cut from production parts.

When Dimensional Stability Under Variable Relative Humidity Governs Part Acceptance

Hygroscopic expansion is a primary failure mode in assemblies that contain both PA12 and metal inserts. The coefficient of linear thermal expansion of unfilled PA12 is typically 100–150 × 10⁻⁶ K⁻¹ in the flow direction and 120–160 × 10⁻⁶ K⁻¹ transverse to flow; moisture-induced linear expansion from dry to 50% RH is approximately 0.15–0.25%. The corresponding value for PA66 can be 0.5–0.8% under the same moisture swing, creating greater risk of insert cracking or dimensional interference. For a gear or clip with a 20 mm critical dimension, PA12 would be expected to change roughly 0.03–0.05 mm due to moisture absorption from dry to 50% RH; the same geometry in PA66 could move 0.10–0.16 mm unless annealed and conditioned.

Part acceptance tests should include conditioning to equilibrium at 23 °C and 50% RH for 168 h and dimensional measurement with a calibrated coordinate measuring machine. Post-mold annealing of unfilled PA12 at 120–150 °C for 2 h per 5 mm wall thickness reduces locked-in orientation and stabilizes crystallinity, but temperatures above 160 °C may cause surface oxidation and discoloration. Shrinkage prediction must account for flow direction: mold shrinkage values for unfilled PA12 are typically 0.7–1.5% in the machine direction and 1.0–1.8% transverse, depending on wall thickness, mold temperature, and gate size. Using a mold temperature at the low end of the range, 30–40 °C, can produce post-mold growth of 0.2–0.5% when the part is subsequently heated or humidified. This is a frequent batch-to-batch variability source in injection facilities that do not control mold temperature tightly.

For regulatory documentation, ISO-TECH ISO-MID PA 12 is typically evaluated under REACH Article 33 obligations and RoHS Directive 2011/65/EU Annex II restrictions. A supplier certificate of conformity should confirm the absence of cadmium, lead, mercury, hexavalent chromium, PBB, and PBDE above the permitted maximum concentration of 0.1% by mass in homogeneous materials. Food-contact status is not implied for all grades; where applicable, the supplier must state compliance with FDA 21 CFR 177.1500 or EU 10/2011 with specific migration limits for laurolactam and caprolactam. Unfilled PA12 is not inherently flame retardant; the material typically meets UL 94 HB at thicknesses of 1.5 mm or greater, but a passing UL 94 V-2 or V-0 classification requires a listed flame-retardant variant. For electrical applications, the comparative tracking index of unfilled PA12 is often 600 V under IEC 60112, but this value drops in the presence of carbon black or high regrind content.

These standards positions are verification starting points, not a substitute for lot-specific certificates. The purchaser must request the manufacturer’s ISO 11469 marking recommendations and any UL Yellow Card if the part enters electrical enclosures.