INZEA F22 Rigid is a polylactic acid-based thermoplastic compound with a renewable carbon fraction greater than 60% when measured by accelerator mass spectrometry or liquid scintillation counting in accordance with ASTM D6866-21 Method B or EN 16640:2017. The product is positioned as a rigid compostable grade for injection moulding and thermoforming; industrial compostability of the final article is assessed under EN 13432:2000 and ASTM D6400-23, subject to maximum thickness, pigment loading, and conversion history. The designation “Rigid” separates the grade from flexible compostable polyesters and starch blends: unfilled PLA literature values for tensile modulus commonly fall between 3000 MPa and 4000 MPa, while elongation at break for unmodified rigid PLA remains below 10% measured per ISO 527-2:2012. The F22 grade is not a thermoplastic starch compound and does not exhibit the rapid wet-strength collapse characteristic of dry starch-based formulations exposed to high relative humidity. Independent published data for this exact formulation is limited; process validation on production tooling remains mandatory.

Renewable carbon accounting should not be conflated with total bio-based mass content. The 60%+ threshold refers to the proportion of total organic carbon derived from contemporary biomass, not the mass fraction of bio-based polymer. Functional additives of fossil origin—nucleants, slip agents, colour concentrates, or mineral fillers—can reduce the total renewable carbon fraction while preserving compostability. Certification under EN 13432:2000 requires aerobic biodegradation of the material to at least 90% CO₂ relative to a cellulose control within 180 days at 58°C, followed by disintegration and ecotoxicity assessments. Claims made without article-specific certification are not equivalent to industrial compostability labeling.

What separates F22 Rigid from lower-renewable PLA compounds and filled olefin replacements?

The primary difference from general-purpose PLA is the documented renewable carbon minimum and the rigidity-led property envelope. Many commercial PLA resins are inherently bio-based above 85% by radiocarbon; F22 Rigid allows a broader range of fossil-derived property modifiers while retaining the 60%+ renewable-carbon position. Compared with filled polypropylene, the material redirects end-of-life options toward industrial organic recycling but imposes a narrower melt-processing window. Unfilled PLA undergoes random chain scission when held above 230°C for extended periods; filled polypropylene tolerates melt temperatures above 240°C with much less molecular weight loss. Melt temperature controls on PLA conversion lines therefore require thermocouple verification at the nozzle and hot runner manifold, not reliance on barrel set-point readings alone.

Differences from high-impact polystyrene and filled polypropylene also extend to melt rheology, density, and shrinkage. Unfilled PLA has a density typically between 1.20 g/cm³ and 1.25 g/cm³, whereas high-impact polystyrene ranges near 1.03 g/cm³ to 1.07 g/cm³; tooling and shot mass calculations must be corrected for this difference. Amorphous PLA mould shrinkage is commonly 0.2% to 0.6%, while polypropylene homopolymer spans 1.0% to 2.0%. Ejector pin area, gate position, and draft angle specifications therefore require re-evaluation when replacing a filled olefin. Impact-modified PLA grades trade stiffness for toughness; the rigid designation indicates a preference for tensile modulus and load-bearing deformation over impact absorption. Notched Izod impact for unmodified rigid PLA remains low—often below 5 kJ/m²—so thin-wall parts with sharp corners may need radius modifications or localized thickening.

Within the INZEA portfolio, the F22 Rigid designation also separates the material from flexible compostable film grades. Those grades are typically blends of PLA with polybutylene adipate terephthalate or thermoplastic starch and show elongation at break above 200%; F22 Rigid is intended where dimensional stability under load is more important than tear propagation resistance. This product differentiation affects tooling design: a flexible grade may fill thin-wall parts at lower injection pressure, while a rigid grade requires generous gate area and venting to avoid short shots and gas burn at the flow front.

When residual moisture exceeds 250 ppm, the melt-processing boundary narrows

When pellet moisture exceeds 250 ppm at the feed throat, the observed melt flow index of PLA-based compounds can increase by more than 20% relative to a dried baseline. This increase is a degradation signal, not a stable viscosity adjustment: ester linkage hydrolysis releases carboxylic acid end groups, and the autocatalytic cycle accelerates chain scission. In injection moulding, the corrective action is not a barrel temperature reduction alone, because moisture hydrolyses the melt in the compression zone before the nozzle thermocouple registers a deviation. The appropriate intervention is a dryer audit—dew point sensor calibration, desiccant rotation cycle, air flow per kilogram of pellets, and return air humidity. Hopper throat blanketing with dry air is recommended in high relative humidity production environments.

Residual moisture is especially critical in vacuum-vented twin-screw compounding lines. A co-rotating twin-screw extruder with L/D 40:1 and multiple vacuum ports can still deliver moisture-degraded pellets if the first vacuum port is starved of surface area or if the pellet cooling water bath carries residual surface water into the classifier. Production-scale equipment logs show batch-to-batch melt flow index variation when dryer return air exceeds 60% relative humidity. The dry-air dew point should be at or below −40°C, and pellet inlet temperature should be confirmed before extrusion. Storage in unlined paper bags or exposed silos in humid climates can reintroduce moisture within hours; sealed aluminium-lined packaging or central dry-air conveying is required after drying.

Injection moulding of rigid PLA compounds generally begins with a general-purpose screw geometry with L/D 20:1 to 24:1 and compression ratio 2.5:1 to 3:1. Barrel profiles from feed to nozzle typically range from 175°C to 210°C for unfilled grades; mould surface temperatures of 25°C to 60°C are used where amorphous transparency and dimensional stability are acceptable. Higher mould temperatures above 90°C increase crystallinity and heat distortion temperature but extend cycle time and can amplify shrinkage anisotropy. Hot runner systems require independent zone control because stagnant melt at elevated temperatures can discolour within minutes. Published data for this specific grade configuration is limited; these values are a starting window derived from unfilled PLA literature and should be confirmed on the actual tool.

Low back pressure and fast screw recovery reduce cumulative residence time at temperature. A 120-tonne clamp injection moulding machine with a 40 mm screw, for example, exhibits longer melt residence when shot size falls below 20% of barrel capacity; cyclic barrel residence becomes a hidden variable that thermal set-points do not capture. Moulders transferring from polypropylene often apply higher back pressure and longer recovery times; in PLA conversion, this practice can produce yellowing and molecular weight loss even when the melt temperature appears stable. Screw speed should be set to achieve smooth recovery without excessive shear heating, and cushion should be held at 3 mm to 5 mm where cavity geometry permits.

Thermoforming of sheet made from F22 Rigid requires careful sheet moisture control and roll release. Amorphous PLA sheet is brittle below its glass transition temperature near 55°C to 60°C; sheet preheating should be uniform and limited to avoid crystallisation haze. Edge trim and skeletal scrap can be reground and reintroduced at controlled levels, but repeated thermal histories increase carboxylic acid content and reduce viscosity. Regrind ratios above 20% should be qualified by melt flow index and tensile testing per lot.

Rheometrical and thermal degradation windows for F22 Rigid

Capillary rheometry and parallel-plate oscillatory rheometry provide the boundary conditions for mould-flow simulation. For unfilled PLA, the viscosity at 200°C and shear rate 100 s⁻¹ generally overlaps the range used for medium-flow polystyrene but is more sensitive to moisture and temperature history. Melt flow index for a rigid PLA grade is commonly reported at 190°C/2.16 kg under ISO 1133-1:2022 or ASTM D1238-23a. However, a single MFI value does not capture degradation: two pellet batches may show the same MFI with different molecular weight distribution, so capillary rheometry across shear rates from 10 s⁻¹ to 1000 s⁻¹ is required for gate sizing and shear stress limits. In production-scale injection moulding, shear heating across small gates can exceed 20°C; this is manageable if the melt is dry but accelerates degradation if residual moisture is present.

Thermal degradation follows pseudo-first-order kinetics within the narrow processing window; the rate constant increases sharply above 230°C. Published literature on PLA thermal degradation demonstrates that holding at 240°C for 30 min reduces molecular weight substantially and increases melt flow index correspondingly; actual values depend on stabilizer package. The specific F22 grade may deviate due to additive chemistry, but the general mechanism is chain scission, not crosslinking. For this reason, purge protocols should use a lower-viscosity PLA purge compound rather than polyethylene or polypropylene, which are incompatible and can form interfacial residues in hot runner channels.

Table 1 summarizes the test methods and boundaries applicable to this product category. The listing is a compliance matrix rather than a product certificate; final article certification must be issued by an accredited body under the specific standard and article geometry.

For single-use food service and rigid packaging, INZEA F22 Rigid can be considered where industrial composting infrastructure exists. The actual compostability claim remains article-specific: pigments, mineral fillers, printing inks, adhesives, and process-induced molecular weight reduction alter disintegration behaviour. Thin-wall injection-moulded parts below 1 mm may exhibit lower crystallinity and therefore lower heat distortion temperature but improved impact brittleness threshold. The material is not intended for durable applications requiring continuous exposure to water above 50°C, as PLA undergoes hydrolysis with progressive loss of tensile strength. Chemical incompatibility with concentrated alkaline cleaning media above pH 10 should be considered for reusable serviceware; surface etching and stress cracking have been reported in PLA under repeated alkaline washing. Storage before processing should be in sealed packaging at 20°C to 25°C and below 60% relative humidity.