Luminy Polylactic Acid (PLA) D120 is a high-stereoregularity poly(L-lactic acid) homopolymer supplied by TotalEnergies Corbion. The product is identified in supplier documentation as having a D-lactic acid monomer content below 1 mol%. This low D-isomer fraction reduces the concentration of stereo-irregular sequences along the polymer backbone and is directly responsible for the elevated melting and crystallisation temperatures observed in thermal analysis. Under ISO 11357-3, the peak melting temperature is reported as 175°C; the glass transition temperature, measured under ISO 11357-2, is reported as 58°C. Melt-flow-rate data obtained under ISO 1133-1 at 210°C with a 2.16 kg piston load place the material in the 8–15 g/10 min range. These values are representative of the supplier data sheet and are not lot-specific certificates. The grade is intended for injection moulding, sheet extrusion, thermoforming and profile extrusion. Primary application domains include injection-moulded coffee capsules, thin-wall containers and thermoformed trays where thermal dimensional stability after crystallisation is required. Published data for this specific configuration in blown-film and foam processes is limited; the material is not specified where elongation at break above 4% is required.

Thermal degradation pathways and crystallization thresholds

Under nitrogen purge, the onset of notable mass loss in polylactic acid is reported in thermogravimetric analysis near 250°C; D120 is therefore processed below 230°C to limit lactide regeneration, random chain scission and discolouration. Supplier processing guidance recommends melt temperatures of 195°C to 220°C for injection moulding. Residence time at barrel temperatures above 210°C should not exceed 10 min; longer hold times at 230°C or higher produce molecular weight loss, an increase in residual lactide and a measurable drop in melt viscosity. Crystallisation from the melt follows nucleation-controlled kinetics with the maximum linear growth rate close to 105°C–110°C. When the tool surface is held at 100°C–110°C, the crystalline fraction develops sufficiently to raise the heat-deflection temperature under ISO 75-2/B at 0.45 MPa from 55°C–65°C in the quenched amorphous state to ≥100°C after crystallisation. The exact value depends on part thickness, nucleating additives, packing pressure and cooling time. Annealing of cold-moulded parts at 80°C–110°C for 30–60 min can produce comparable crystallinity, but differential shrinkage and dimensional change must be compensated in the tool. For single-screw extrusion, barrel settings from feed throat to die are typically 180°C to 210°C; screw designs with an L/D ratio of 28:1 to 32:1 and a compression ratio of 2.0:1 to 2.5:1 are recommended to avoid excessive shear heating.

Isothermal crystallisation studies on high-stereoregularity PLA report crystallisation half-times at 110°C below 60 s depending on nucleating agents. D120, by virtue of low D-isomer content, is expected to show faster crystallisation than general-purpose grades, but published data for this specific configuration is limited. In practice, hot-tool injection moulding at 100°C–110°C uses cooling times of 15–30 s for wall thicknesses of 2 mm; shorter cooling times yield incomplete crystallinity and lower heat-deflection temperature. The cooling-time requirement must be determined by differential scanning calorimetry of the moulded part, not by appearance alone.

On a 40 mm single-screw extruder with a 30:1 L/D barrier screw, the melt pressure before the screen changer typically increases by 0.5–1.0 MPa for every 100 ppm increase in residual moisture above the 250 ppm limit. This pressure rise is used as an indirect control signal in sheet extrusion. Die drool and surging in the feed section are observed when the rear barrel zone is set above 60°C, because pellet surface softening causes premature sticking and irregular solids conveying. For co-rotating twin-screw extrusion used to compound masterbatch or nucleating agents into D120, a screw speed of 200–250 min⁻¹ and a specific mechanical energy input below 0.2 kWh/kg are recommended to limit lactide formation; higher SME inputs produce a measurable increase in melt acidity and a corresponding reduction in intrinsic viscosity. These operational boundary values are derived from supplier processing guidelines and equipment manufacturer recommendations; line-specific optimisation is mandatory.

What limits the injection moulding window for D120?

Two process parameters define the usable window: melt temperature and tool temperature. Melt temperature below 195°C results in incomplete melting of the crystalline fraction and visible unmelts in thin-wall sections; melt temperature above 220°C increases the concentration of lactide in the melt stream and can generate acetaldehyde, which is a regulatory concern in food-contact articles. Tool temperature controls crystallisation. A cold tool at 20°C–30°C produces a transparent amorphous skin with heat-deflection temperature under ISO 75-2/B of 55°C–65°C. A hot tool at 100°C–110°C produces an opaque semicrystalline part; the same ISO 75-2/B method then yields values of ≥100°C. Mould temperature variation across the cavity should be maintained within ±5°C; larger gradients produce warp from differential crystallinity and anisotropic shrinkage. Injection speed has a secondary effect. Shear rates above 20 000 s⁻¹ generate shear heating and can improve filling of sub-1 mm wall sections, but the maximum shear rate should be verified through pressure-drop analysis because excessive shear can reduce molecular weight. Hold pressure must be maintained until gate freeze; for semicrystalline D120, gate-freeze time is shorter than for amorphous PLA at equivalent tool temperature. Clamp force requirements follow standard cavity-pressure calculations; parts with projected area exceeding 0.1 m² may require clamp forces above 1500 kN. The grade is unsuitable for hot-runner systems with residence times above 10 min at 210°C.

Before melt processing, D120 pellet moisture must be reduced to below 250 ppm by weight. A desiccant-bed dryer with a dew point of -40°C or lower and inlet air temperature set to 80°C for 4–6 h is specified in supplier literature. Hopper residence time should not exceed 2 h at 80°C if the material is not immediately consumed; prolonged heating in the hopper can cause pellet agglomeration and feed instability. Moisture above 250 ppm induces hydrolytic chain scission during melt processing; the effect is observed as a drop in melt viscosity exceeding 5% and a reduction in tensile strength of injection-moulded specimens. Storage at relative humidity above 60% requires re-drying before processing. The granules should not be blended with amine-based masterbatches because residual amines catalyse ester cleavage and accelerate molecular-weight loss. The same incompatibility applies to uncleaned processing equipment previously used with amine-containing engineering resins.

D120 is evaluated as a rigid biopolymer. The following representative values are from injection-moulded specimens conditioned at 23°C and 50% relative humidity for 48 h according to ISO 291. The data are not to be interpreted as minimum or maximum lot values. Elongation at break is lower than for impact-modified PLA grades, and notched impact strength should be considered for snap-fit or threaded closures.

Lot-to-lot variation in melt-flow rate is controlled within the supplier release limits, but converters should verify the actual value on each certificate of analysis because melt viscosity directly affects fill pressure and gate design. Dynamic mechanical analysis under ISO 6721-1 shows a steep storage-modulus decline at 58°C, limiting continuous load-bearing use of amorphous D120 to ambient conditions. Semicrystalline specimens retain a plateau modulus above 100°C up to the melting region, but creep resistance remains time-dependent and must be measured under ISO 899-2 for structural parts.

Food-contact and compostability documentation

Compliance statements for D120 are application-specific. Under European Regulation (EU) No 10/2011, the grade may be used for food-contact articles provided that migration testing under EN 1186 and EN 13130 is performed on the finished article; the supplier provides a Declaration of Compliance for the raw polymer. In the United States, food-contact status is governed by the supplier Food Contact Notification; article-specific end-testing remains the responsibility of the converter. Industrial compostability is certified under EN 13432 when the wall thickness and geometry are within the certification scope; certification does not extend to home composting under AS 5810 or to anaerobic digestion without separate validation. The biobased carbon fraction can be verified by ASTM D6866 or EN 16640; the supplier reports 100% renewable carbon in the polymer backbone. The product is not a drop-in replacement for PET in hot-fill applications without barrier coatings because PLA has higher water vapour transmission than PET under ISO 15106-1. The converter must also assess overall migration limits under EU Regulation (EU) No 10/2011 for the specific food simulant, time and temperature conditions.

When D120 replaces lower-purity PLA grades in rigid packaging

When D120 is substituted for a general-purpose PLA grade with a higher D-lactic acid content, the following processing and performance differences apply. The melt temperature must be raised by 10°C–15°C to accommodate the higher melting point, and the melt viscosity at constant shear rate is higher, which may require an increase in injection pressure or a reduction in flow-path length. The mould temperature should be raised to 100°C–110°C to exploit crystallinity; otherwise, the heat-deflection advantage is lost. The resulting part is less transparent than amorphous PLA because spherulites scatter visible light; for clarity-critical packaging, D120 is not appropriate unless the part is thin enough to quench crystallisation. In comparison with impact-modified PLA grades, D120 has higher tensile modulus and lower elongation at break; tensile modulus is approximately 3500 MPa under ISO 527-2, whereas impact-modified grades may fall below 2500 MPa. D120 also exhibits lower mould shrinkage after annealing than amorphous PLA: supplier data indicate linear mould shrinkage under ISO 294-4 of approximately 0.3%–0.5% for semicrystalline parts, compared with 0.5%–0.8% for amorphous parts, depending on fibre orientation and wall thickness. These differences affect tool design, gate location, and part tolerances; converters should perform dimensional capability studies at the intended crystallinity level before transferring existing tools.

Injection-moulded coffee capsules made from D120 are typically specified with a wall thickness of 0.3–0.8 mm. The combination of hot-tool crystallisation and post-mould annealing provides adequate resistance to hot-water contact at 85°C–95°C, but capsule lids and seals require barrier films because PLA has higher oxygen permeability than PVDC or aluminium. The target oxygen transmission rate under ISO 15105-2 is application-specific and must be validated on the finished capsule assembly.