INZEA F58 AL30 is a rigid polylactic acid compound supplied by Nurel Biopolymers for sheet extrusion, roll-fed or sheet-fed thermoforming, and injection molding of rigid disposable packaging. The grade is formulated for applications requiring industrial compostability under EN 13432 or ASTM D6400, with a property envelope typical of high-stiffness PLA rather than flexible PBAT or PBS. Manufacturer literature lists a melt flow rate of 6 g/10 min at 190 °C/2.16 kg according to ISO 1133-1, a density of 1.24 g/cm³ according to ISO 1183-1, a tensile yield strength of 60 MPa according to ISO 527-2, and a tensile modulus of 3600 MPa according to ISO 527-2. The notched Charpy impact value is approximately 3.5 kJ/m² (ISO 179-1/1eA), indicating rigid failure behavior rather than ductile deformation. The product is intended for use in cooled tools; continuous service above the Vicat softening temperature of approximately 58 °C (ISO 306/B50) must be avoided.

Drying and hydrolytic degradation thresholds before melt processing

Moisture control is the controlling variable for melt processing of this PLA-based grade. PLA undergoes hydrolytic chain scission when residual moisture exceeds 0.025 wt%, and the reaction rate increases with residence time and melt temperature. Drying in a dehumidifying hopper dryer with a dew point of -40 °C to -50 °C at 70–80 °C for 4–6 h is required. If incoming granulate moisture exceeds 0.4 %, drying time is extended to at least 8 h and dryer airflow must be sufficient to maintain hopper outlet temperature. Residual moisture should be verified by Karl Fischer titration or a calibrated moisture analyzer to below 250 ppm before melt processing. On production-scale twin-screw sheet extrusion lines with L/D 30:1 to 44:1, incomplete drying is observed as edge instability, gear pump surging, and falling melt pressure. Melt pressure variance above ±0.5 MPa at constant screw speed is commonly traced to residual moisture or bypass of the drying system.

Melt temperature is maintained at 190–210 °C for sheet extrusion and 190–205 °C for injection molding. Prolonged residence above 220 °C generates lactide and oligomeric deposits on die lips and vent ports; the condition appears as white plate-out and increased screw torque. Screw speed is kept in the moderate range of 80–150 rpm on 30:1 to 40:1 L/D extruders, depending on barrel diameter, to limit shear heating. Injection unit back pressure is set at 5–15 bar gauge to maintain stable shot size without overworking the melt.

In sheet-fed thermoforming, the extruded sheet is typically produced at a thickness of 0.3–1.5 mm and processed on plug-assisted or pressure-forming lines with sheet surface temperatures of 90–120 °C. The forming window is narrower than amorphous PET. Below 90 °C the sheet develops stress whitening at corner radii, while above 120 °C sag becomes excessive. The AL30 formulation is designed to reduce sag during index heating; however, draw ratios above 3:1 still require a heated plug at 90–110 °C and forming air pressure of 4–6 bar to prevent wall thinning below 0.15 mm in cup sidewalls. Thermoforming operations running multi-cavity trays with 32 or 48 cavities can reintroduce edge regrind at up to 30 wt% when the regrind is re-dried and the sheet is not used as a direct food-contact sealing layer.

What separates the AL30 formulation from unmodified PLA, PET and PBAT?

The differentiation from unmodified PLA is most visible in melt tension during sheet take-off. Unmodified PLA grades of similar melt flow rate show greater neck-in and web flutter on polished three-roll stacks, whereas the AL30 package increases melt strength and allows higher line speeds. The formulated grade maintains a tensile modulus near 3600 MPa, which is approximately 3–5 % higher than several unfilled PLA injection grades and more than an order of magnitude above PBAT film grades in the 50–500 MPa modulus range. Compared with PET, the density is lower by approximately 0.13 g/cm³, but the heat deflection temperature under load is approximately 55 °C (ISO 75-2/B), below that of PET. Oxygen barrier is also inferior to oriented PET; published oxygen transmission values for PLA sheet at 250 µm are commonly in the range 20–40 cm³/(m²·day·bar) at 23 °C and 50 % RH (ASTM D3985), whereas oriented PET of similar thickness is typically below 5 cm³/(m²·day·bar). This grade is therefore not a drop-in replacement for barrier trays unless additional coatings or multilayer structures are used.

Against PBAT and PBS, rigidity is the decisive difference. PBAT has a tensile modulus near 100 MPa and yields flexible film, while PBS occupies a flexural modulus range of approximately 300–700 MPa. INZEA F58 AL30 occupies a stiff plateau suitable for rigid tray geometries without reinforcing fibers. The trade-off is impact: PBAT remains ductile at low temperature, while this PLA grade exhibits Charpy notched impact below 5 kJ/m² and should not be specified for snap-fit or living-hinge components.

Compostability certification boundaries and barrier data

Compostability claims for this product are valid only in industrial composting facilities meeting the temperature and moisture conditions of the test standard. Disintegration is evaluated under EN 13432 or ASTM D6400 using compost at 58 °C and approximately 50 % moisture; these conditions are not replicated in ambient soil or marine water. Certification under one standard does not automatically confer certification under the other, and country-specific conformity programs such as DIN CERTCO or TÜV Austria require separate assessment. For food-contact applications, compliance must be confirmed against 21 CFR 175.300 or Regulation (EU) No 10/2011 as applicable; the grade is not self-certified for all food types and all alcohol or fat levels.

Injection molding of the grade is carried out with a general-purpose or low-compression screw having a compression ratio of 2.0:1 to 2.5:1 and a check ring suitable for shear-sensitive melts. Mold temperatures between 15 °C and 30 °C are used to shorten cycle time; mold temperatures above 40 °C increase crystallinity but extend cycle and can cause sticking in unpolished cavities. The material solidifies rapidly, so injection speeds are set to fill thin-wall cavities in 0.5–1.5 s, with holding pressure at 60–80 % of injection pressure. Shrinkage after molding is in the range 0.3–0.7 % (ISO 294-4), and tool dimensions are calculated accordingly. For multi-cavity closures or trays, clamp force requirement is approximately 3–5 kN/cm² of projected part area.

When cold-wall molds and high injection speeds become process risks

Cold-wall molds below 15 °C can generate jetting and surface flow marks because the melt freezes before the cavity is fully packed. High injection speeds above 150 mm/s generate shear heating that may exceed the 220 °C degradation threshold even when the barrel set temperature is 195 °C. In valve-gated hot-runner systems, dead spots above 10 s residence time lead to yellowing and black specks; hot-runner manifolds are therefore maintained at 190–200 °C with free-flow shutoff nozzles. The product should not be compounded with amine-based antistatic or slip additives without compatibility testing because basic additives can accelerate PLA chain scission in the melt. If regrind is used, it must be re-dried to 250 ppm and limited to 30 wt% in direct food-contact parts unless migration testing under Regulation (EU) No 10/2011 demonstrates compliance.

Long-term dimensional stability is bounded by the glass transition of PLA near 55–60 °C and by moisture-induced hydrolysis at elevated relative humidity. In high-humidity storage above 85 % RH, tensile strength retention after 60 days may fall below 80 % of the conditioned value. Applications requiring sustained load at 45 °C or above should be validated in the specific geometry and wall thickness, because published data for this specific grade under combined thermal and mechanical load is limited.