LATI Latimass 82-05 D040 PA12 is a high-density thermoplastic compound based on polyamide 12 and a high-mass-fraction metallic filler system. The D040 segment of the designation corresponds to a nominal density of 4.0 g/cm³ when measured in accordance with ISO 1183-1. The 82-05 prefix is associated in LATI’s Latimass nomenclature with a high filler mass fraction, commonly approaching 82 wt%; the exact filler chemistry and surface treatment should be confirmed from the production batch documentation. The polyamide 12 matrix is selected to provide lower equilibrium moisture absorption than PA6-based dense compounds, while the filler system contributes radiopacity, mass attenuation, and high specific gravity for diagnostic X-ray, industrial CT, and nuclear instrumentation housings. The material is typically supplied as dark granules and requires density verification at incoming inspection because small changes in filler distribution shift shot weight, part mass, and shielding behaviour.

What Distinguishes the D040 Density Grade from Standard PA12?

An unfilled PA12 resin exhibits a density near 1.01 g/cm³ under ISO 1183-1 and behaves as a ductile semi-crystalline thermoplastic. The Latimass 82-05 D040 grade increases density approximately fourfold through metallic filler loading; the filled compound shifts from ductile deformation to a low-elongation, high-stiffness composite. Published data for this specific configuration in open technical bulletins is limited beyond density, base polymer, and filler-mass class; mechanical values should be taken from the batch certificate rather than transferred from general-purpose PA12 or from lower-density filled systems. Compounds with 80–85 wt% metallic filler in a PA12 matrix commonly show elongation at break below 5% and require mould-filling analysis that accounts for reduced melt elasticity and shorter flow length. The low PA12 continuous-phase content reduces moisture-related dimensional movement relative to filled PA6, but it also lowers weld-line strength when multi-gate layouts are used.

Because the melt viscosity of a 4.0 g/cm³ metallic-filled PA12 is substantially higher than unfilled PA12, hot-runner and cold-runner tooling must be designed for high shear heating and reduced melt elasticity. Gate sizes below 1.5 mm diameter are generally unsuitable for high-mass-filler compounds; the metallic filler promotes jetting and accelerates gate wear. A minimum full-round gate diameter of 2.0 mm to 3.0 mm is common for thin-wall medical housings. For larger components, edge gates with a land length between 0.8 mm and 1.2 mm are used to prevent premature freeze-off. The high thermal conductivity of the filler accelerates cooling at the cavity wall and can produce a frozen skin layer that masks sink marks; packing pressure must therefore be maintained until gate seal, not merely until the cavity appears visually full. On a 100 t hydraulic injection moulding machine producing collimator housings from this material, screw rotation speed is normally limited to 40–80 min⁻¹ for a 35 mm three-zone screw, with back pressure maintained between 2 MPa and 5 MPa to improve melt homogeneity without excessive shear heating.

When Lead Replacement Requires Injection Mouldable Geometries

In radiation-shielding applications, the reference material is often lead sheet with a density of 11.34 g/cm³. A PA12-based compound at 4.0 g/cm³ cannot be used as a drop-in thickness replacement for lead because equal photon attenuation requires a thicker path length. The required thickness ratio for a monoenergetic beam is governed by the mass attenuation coefficient ratio, not by density ratio alone, and should be calculated from NIST/XCOM or Monte Carlo data for the specific filler chemistry. Nonetheless, the injection moulding advantage appears when a single thermoplastic part must combine shielding, structural snap-fits, cable channels, threaded inserts, and gas-tight seals. A lead casting or lead-lined machined housing would require secondary operations and cannot produce the same thin-wall rib integrity or part consolidation. The Latimass grade is therefore specified for X-ray detector housings, dental handheld X-ray tube shields, nuclear medicine collimator components, and industrial CT enclosures where low-volume production does not justify die-cast tungsten alloy tooling.

Even with a low-moisture PA12 matrix, surface moisture on the high filler surface area and granule porosity can produce splay and surface defects on the first injection cycle. Manufacturer documentation for PA12-based compounds generally recommends pre-drying at 80°C for 4–8 h using a desiccant dryer with a dew point of −30°C or lower. Residual moisture should be measured by ISO 15512 or Karl Fischer titration, with a target below 0.10 wt%. In high-humidity environments above 60% RH, drying should be extended toward the upper end of the range, and open granule residence time in the machine hopper should be limited to 30 min or less. A heated hopper at 70–80°C is acceptable only if the hopper is sealed and insulated; otherwise condensation on the cold granule surface reintroduces moisture before plastication.

Why High Filler Loading Changes Screw, Barrel, and Non-Return Valve Life

Filler levels approaching 82 wt% classify this material as abrasive. General-purpose nitrided screws and barrels show measurable wear after fewer than 500 production hours. Bimetallic barrels with tungsten carbide or high-hardness powder-metallurgy screw elements are recommended. The non-return valve should be a radial-ring or ball-check design with hardened sealing surfaces, because severe leakage at the check ring leads to inconsistent cushion and shot volume. Processing with open nozzles is preferred; shut-off nozzles with sliding pins can seize when metallic filler accumulates in the pin-bore clearance. Mould steel should be hardened to at least 50 HRC for gate inserts and wear plates; unhardened P20 cavitation is acceptable only for short prototype runs. Sprue bushes and runner blocks should be inspected for erosion at the sharp corner where the melt changes direction, and runner diameters should be kept at least 1.5 times the gate thickness to avoid excessive pressure loss.

If PA6-Based Dense Compounds Are Replaced by PA12 in Humid Environments

Substituting a PA6-based Latimass grade with Latimass 82-05 D040 PA12 reduces equilibrium moisture uptake and improves dimensional stability in housings exposed to ambient humidity cycles. PA6 can absorb approximately 2.5–3.0 wt% moisture at 23°C and 50% RH, while PA12 typically absorbs approximately 0.7–1.0 wt% under the same conditions when measured by ISO 62. The dense filler dilutes the polymer phase further, but dimensional change is still controlled by the continuous matrix. The trade-off is that PA12 has a lower melting point than PA6, so continuous use above 160°C may produce deformation under load. If steam sterilization at 134°C is required, the component should be validated in an unloaded condition or a high-temperature matrix such as PPS or PEEK in the Latimass range should be evaluated. Chemical compatibility is generally advantageous for oils, greases, aliphatic hydrocarbons, and saline solutions; strong oxidizing acids and polar organic solvents can attack the matrix or corrode the filler system, and compatibility should be tested according to ISO 22088 or the specific OEM test protocol.

Photon attenuation calculations for the 4.0 g/cm³ compound should not be based on a single linear attenuation coefficient supplied without an energy reference. At diagnostic photon energies between 40 keV and 120 keV, dense metal-filled thermoplastics are used to replace lead foil in non-critical shielding zones. The manufacturer does not specify a single linear attenuation coefficient because attenuation is energy-dependent and filler-dependent. Designers should determine the effective linear attenuation coefficient using narrow-beam geometry tests or Monte Carlo models calibrated to the production-grade filler system. For comparative purposes, a 4.0 g/cm³ compound with a tungsten mass fraction near 82 wt% provides substantially higher attenuation per millimetre than unfilled PA12 but lower than pure tungsten alloy with density 17.0–18.5 g/cm³. Part thickness required for a given attenuation target should be calculated from the mass attenuation coefficient at the incident energy, not from density ratio alone.

Processing Conditions and In-Mould Rheology for a 4.0 g/cm³ Grade

Melt preparation for a 4.0 g/cm³ high-density PA12 grade requires a compromise between plastication rate and shear heating. The screw should be selected for low compression and high wear resistance, typically a three-zone geometry with compression ratio between 1.5:1 and 2:1 rather than the higher compression ratios used for semi-crystalline unfilled PA12. Metering depth should be increased where possible to accommodate the high melt viscosity and reduce melt temperature spikes. Mould surface temperatures below 50°C may create a cold skin that freezes off thin ribs before packing; mould temperatures above 80°C extend cycle time and can produce surface blush. Short-shot studies should be used to identify the transfer position, and the final cushion should be held between 2 mm and 4 mm to maintain a stable packing profile.

Batch release and incoming quality assurance for Latimass 82-05 D040 PA12 should include density measurement by ISO 1183-1 or Archimedes immersion, residual moisture by ISO 15512, and filler content by ashing or thermogravimetric analysis. Density variation of ±0.2 g/cm³ changes shot weight by approximately 5% for the same cavity volume, which is significant for radiation-shielding parts where wall thickness is a critical design variable. Regrind usage should be limited to 20–30 wt% of the shot; repeated pelletizing of metallic-filled compounds reduces flow stability and increases screw wear. Cross-contamination with unfilled PA12, PA6, or other dense grades must be avoided because density stratification in the hopper and melt pool can shift attenuation and mechanical performance within a single part. RoHS and REACH declarations must be obtained for the specific batch because filler chemistry and surface treatments can affect concentration limits under Directive 2011/65/EU and the REACH candidate list. The material should not be combined with amine-based processing aids or incompatible regrind streams unless the compounder has explicitly qualified the mixture.