EMS-Griltech Grilamid DN 80 Nylon 12 Monofilament is a melt-spun, oriented monofilament derived from polyamide 12. The base chemistry places the product in the EMS Grilamid family, while the DN 80 designation is specific to the monofilament grade supplied by EMS-GRILTECH. Published manufacturer documentation indicates that the material is intended for drawn technical monofilament applications rather than injection-molded or film-extruded polyamide 12. Semicrystalline PA12 homopolymer typically exhibits a melting range of 175–180 °C as measured by differential scanning calorimetry according to ISO 11357-3, a density of 1.01–1.02 g/cm³ per ISO 1183-1, and equilibrium moisture absorption at 50 % relative humidity of approximately 0.7–1.0 %. The lower amide-group density compared with polyamide 6 and polyamide 66 reduces water plasticization and improves the retention of wet flexural stiffness. Published data for the exact DN 80 configuration are limited outside EMS-GRILTECH technical datasheets; therefore the following engineering observations are based on PA12 monofilament behavior and representative industrial conversion tests.

Monofilament specifications for DN 80 should be obtained from EMS-GRILTECH for linear density, nominal diameter, tenacity, elongation at break, and boil shrinkage. Without such lot-specific values, the product cannot be safely specified against ISO 527-2 or ASTM D638-14 acceptance limits. Industrial PA12 monofilaments after orientation commonly show tensile strength in the range 350–600 MPa and elongation at break between 15 % and 40 %, depending on draw ratio and quench history. These ranges are not a substitute for DN 80 certificate values. The coefficient of friction of PA12 monofilament against polished steel is typically lower than that of polyamide 6 under dry sliding; this difference can reduce fabric wear in sliding applications, but it also depends on finish formulation and surface roughness.

Selecting DN 80 over PA6 is especially justified in dewatering fabrics, filter mesh, and paper machine clothing exposed to cyclic wet stress. After water saturation, PA12 monofilament retains more of its dry tensile strength than PA6 because its equilibrium water content is about one-third of the PA6 value, as reflected in ISO 62 moisture absorption data. At −40 °C, PA12 monofilament retains impact resistance that PA6 grades may lose, which is relevant for outdoor conveyor belts in cold climates. The material is not recommended for continuous service above 80–100 °C in oxidative environments, because polyamide 12 undergoes thermo-oxidative degradation over time. For applications involving hot nitric acid or concentrated mineral acids, PEEK or PVDF monofilament should be evaluated instead.

How Does the Drawing Sequence Affect DN 80 Monofilament Properties?

The tensile response of Grilamid DN 80 is controlled by the pseudo-affine orientation of the polyamide 12 lamellae during solid-state drawing. A two-stage draw process is typical: first-stage drawing in hot water at 60–80 °C, second-stage drawing in hot air at 120–150 °C, followed by annealing under controlled relaxation of 5–10 %. Draw ratios in the range 3.5:1 to 5.0:1 are common for PA12 monofilament; increasing draw ratio raises the tensile modulus and tenacity while lowering elongation at break. Too high a draw ratio produces fibrillation and a loss of knot strength. Measurement of knot strength is performed using a simple overhand knot and a tensile tester according to ASTM D2256 or ISO 2307. Monofilament fabric suppliers often specify a minimum knot strength as a percentage of straight tensile strength; for oriented PA12 monofilament, knot strength values in the region of 60–80 % of straight tensile strength are industrially accepted, but DN 80-specific values must be confirmed with lot testing. Take-up speeds in monofilament lines typically range from 50 m/min to 250 m/min depending on diameter, with thinner filaments drawn at higher linear speeds.

Production-Scale Extrusion and Quench Equipment for Grilamid DN 80

Conversion of Grilamid DN 80 on a production line requires a single-screw extruder with a screw length/diameter ratio of 25:1 to 30:1 and a compression ratio selected for polyamide 12, usually 3:1 to 3.5:1. Barrel temperatures are typically profiled from 200 °C at the feed section to 230–250 °C at the metering section and die; polyamide 12 has a narrower processing window than PA66 and is subject to oxidative yellowing if melt temperature exceeds 260 °C for extended hold-up. A gear pump between the extruder and the spinneret is recommended to stabilize melt pressure and reduce surging. Melt filtration through a screen pack with mesh sizes between 25 µm and 50 µm removes gels before the die. Quenching is performed in a water bath at 20–40 °C, with a quench length long enough to prevent crystallization heterogeneity. Hot-water drawing and hot-air annealing are then performed as described above. Moisture is critical: PA12 should be pre-dried to below 0.10 % residual moisture using a desiccant dryer with a dew point below −40 °C at 80 °C for 4–6 h. Residual moisture above 0.15 % causes hydrolysis and bubble formation in the melt. These are standard PA12 extrusion settings; EMS-GRILTECH may provide DN 80-specific processing instructions.

Thermal degradation during start-up and shutdown is a known bottleneck on monofilament lines. If the melt remains in the extruder barrel for more than 10–15 min at 250 °C, melt viscosity can drop, and the resulting filament shows increased diameter variation and lower tensile strength. For this reason, production equipment often uses start-up purging with a higher-MFR PA12 or a purge compound. The DN 80 grade should not be combined with amine-rich additives or recycled PA6/PA66, because amine end groups can promote transamidation and shift melt rheology during long runs. Incompatibility with PA66 is especially relevant in multi-polymer shops; cleaning the screw and die is required before switching from PA66 to DN 80. Production staff should monitor melt pressure and drive current; pressure fluctuation above ±10 % of setpoint usually indicates melt instability or insufficient back pressure.

Rheological evaluation of PA12 monofilament grades is conventionally performed by capillary rheometry at 230 °C using a die with 40:1 length/diameter ratio; this method detects shear sensitivity and extrudate swell before line trials. Commercial PA12 monofilament grades typically exhibit an apparent melt viscosity at 1000 s⁻¹ in the range 80–200 Pa·s, but DN 80-specific values are not publicly available and should be requested from EMS-GRILTECH. The solution viscosity number per ISO 307 is a more robust incoming QC parameter because it correlates with molecular weight and final tensile strength after orientation. A drop in viscosity number of more than 10 % between lots may indicate degradation or unintended blending; such material should be quarantined before spinning.

Diameter uniformity and linear density are critical for weaving. Monofilament diameter is measured with a contact gauge per DIN 53830 or optical micrometer; coefficient of variation below ±2 % is required for high-mesh-count screen fabrics. Linear density in tex or denier is measured by ISO 2060. A diameter variation above ±3 % produces mesh opening distortion after weaving and heat-setting. Batch-to-batch variance in DN 80 should be monitored through melt flow rate measured per ISO 1133-1:2022 and solution viscosity per ISO 307. If the supplier cannot provide those values for a particular lot, incoming QC should include tensile testing of drawn monofilament at 500 mm/min per ISO 527-2.

When Grilamid DN 80 Is Compared with PA6, PA66, and PET Monofilament

The choice between DN 80 and other monofilament polymers depends on moisture uptake, thermal resistance, abrasion behavior, and cost per linear meter. Polyamide 6 and 66 have higher dry tenacity and higher melting points but lose more tensile strength in humid service. Polyethylene terephthalate monofilament has lower elongation and higher modulus, making it more dimensionally stable under high loads, but its resistance to flex fatigue and UV hydrolysis can be lower than PA12 in certain acidic environments. The DN 80 designation should not be confused with Grilamid injection-molding grades such as L 16 or transparent TR grades. Monofilament-specific grades are formulated to withstand the high extension ratios of solid-state drawing and to produce uniform diameter under high-speed winding; injection-molding grades are not optimized for this orientation window. Table 1 summarizes representative engineering ranges for drawn monofilament; these are not DN 80 guarantees.

PA12 monofilament generally exhibits lower hysteresis heating in cyclic bending than PET, which reduces internal fatigue failure in filter belt spirals. However, published data for DN 80 specifically concerning S-N curves or abrasion mass loss under ISO 4649 is limited; manufacturer validation is required for fatigue-limited designs.

Common fabrication routes for DN 80 include weaving into open-mesh filter fabrics, spiral-link formation for dryer belts, and knitting into tubular filters. The monofilament diameter range is typically 0.08–1.00 mm for technical mesh, with smaller diameters used in screen printing and larger diameters for spiral fabrics. Post-weaving heat-setting at 120–160 °C for 2–5 min is common to relax internal stresses and stabilize mesh dimensions. The heat-setting temperature should remain below the annealing temperature used during drawing to avoid excessive loss of tenacity. For chemical filtration, the operating pH range of PA12 is broadly between 3 and 11 at room temperature; prolonged exposure to strong acids above 50 °C or strong bases above 60 °C may cause surface hydrolysis and should be validated case by case.

Regulatory Status Requires Migration Testing, Not Resin Certification

Food-contact use of Grilamid DN 80 depends on the formulation of the monofilament and any processing additives. Polyamide 12 homopolymers are generally recognized for food-contact use under FDA 21 CFR 177.1500(a)(4) when the finished article meets extractives limits for the intended food type and temperature. In the European Union, compliance with EU Regulation 10/2011 requires an overall migration limit of 10 mg/dm² and specific migration limits for any additives used. The finished fabric or mesh manufacturer, not the resin supplier, is responsible for migration testing under EN 1186 test conditions. Industrial uses under RoHS 2011/65/EU require that lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE do not exceed 0.1 % by weight for lead and 0.01 % for cadmium in homogeneous materials. REACH registration is normally held by EMS-GRILTECH for the monomer and polymer; downstream users must verify that their article production does not release SVHC above communication thresholds. Table 2 lists the compliance matrix.

Operational boundaries for DN 80 must be observed in the field. Continuous service above 80 °C in air may lead to progressive surface oxidation and embrittlement. Repeated autoclaving at 121 °C is generally not recommended for PA12 monofilament unless validated, because repeated saturated steam cycles can cause surface hydrolysis and tensile loss. Contact with concentrated formic acid, phenol, or chlorine bleach at elevated temperature should be avoided. When UV exposure is significant, carbon black or hindered amine stabilizers are required; PA12 monofilament without UV stabilization degrades under ISO 4892-2 accelerated weathering and loses surface gloss and tensile strength. Published data for this specific configuration under combined chemical and thermal stress is limited; field validation remains the final step before specification.