INZEA F28 HT Rigid 80% Renewable Compostable Polylactic Acid is produced under the INZEA brand as a rigid polylactic acid compound. The grade designation F28 HT separates this material from flexible film grades and from standard amorphous PLA: the HT suffix indicates a heat-resistant formulation, while the 80 % renewable carbon claim refers to the biogenic fraction of total organic carbon rather than to a mechanical property. Polylactic acid is a linear aliphatic polyester obtained by ring-opening polymerisation of lactide derived from fermented plant starch or sugar. The final behaviour of the compound depends on stereochemical composition, nucleating agents, filler content, and melt-processing history. Because additive load and molecular weight vary within manufacturing tolerance, lot-specific data should be taken from the certificate of analysis rather than from generic PLA literature.

The renewable carbon content and compostability of INZEA F28 HT are regulated by separate standards. Renewable carbon is normally measured by ASTM D6866 or EN 16640, both of which distinguish modern biogenic carbon from fossil carbon by isotopic analysis. Compostability is certified under EN 13432 for packaging or ASTM D6400 for plastics intended for aerobic municipal or industrial composting. Certification may impose limits on part thickness, pigmentation, and lamination. These limits are relevant for heat-resistant PLA grades because nucleating agents and mineral fillers can change disintegration kinetics. A formulation that meets the disintegration requirement at 1.5 mm thickness may not automatically meet it at 5 mm wall thickness.

What Distinguishes High-Heat Rigid PLA from Standard PLA Grades?

The principal difference is crystallisation behaviour. Standard amorphous PLA parts are usually limited to a heat deflection temperature near 55 °C under ISO 75-2 Method B because the glass transition temperature of PLA is approximately 55–60 °C. High-heat PLA compounds are formulated to develop measurable crystallinity during moulding or annealing, which can raise heat deflection temperature into the approximate class range of 80–110 °C depending on filler content and part geometry. In rigid high-heat PLA, tensile modulus measured by ISO 527-2 typically falls between 3000 MPa and 4200 MPa, while elongation at break remains below 5 %. This is a stiff, low-elongation response. Compared with standard PLA, the processing window narrows because nucleation accelerates solidification. For the F28 HT designation, published data for this specific configuration is limited; the values below represent a class envelope rather than a lot-specific guarantee.

In twin-screw compounding lines with 40:1 L/D and vacuum venting, moisture ingress is the dominant source of batch-to-batch variation. PLA undergoes hydrolytic chain scission at melt-processing temperatures when residual moisture exceeds approximately 250 ppm. Production-scale desiccant dryers should maintain a dew point of -40 °C or lower. A common drying profile is 80 °C for 4 h, but the actual condition must be validated for the specific dryer bed depth and air flow. Residual moisture is measured before extrusion by Karl Fischer titration under ISO 15512. Inadequate drying is observed on the line as screw torque fluctuation, die-lip build-up, splay, and reduced melt strength. These symptoms cannot be corrected by raising barrel temperature because thermal degradation then competes with hydrolysis and further reduces molecular weight.

Injection moulding of rigid HT PLA grades is controlled more by mould-temperature strategy than by melt temperature alone. Barrel profiles from 180 °C to 210 °C are commonly used, with the nozzle held below 220 °C to limit molecular weight loss. Cold-mould cycles at approximately 25 °C are suitable for thin-walled amorphous parts with short cycle targets, but the resulting heat deflection temperature remains close to the glass transition. Hot-mould cycles at 90–110 °C induce crystallisation during filling and packing, raising heat resistance at the cost of longer cycle time and higher mould maintenance. Clamp force requirements follow standard PLA viscosity. A hydraulic injection pressure of 80–120 MPa is typical for rigid PLA compounds, but the exact value depends on gate geometry, wall thickness, and flow length. Hydrocarbon-based mould release agents are generally compatible. Amine-based release agents and amine-containing additives should be avoided because they can accelerate degradation through aminolysis.

When an 80 % Renewable Claim Requires Certification Evidence

The 80 % renewable carbon figure is a supply-chain claim, not a mechanical specification. Under ASTM D6866, the result is reported as the fraction of modern carbon in total organic carbon. Under EN 16640, the result is expressed as biogenic carbon content. These methods rely on isotope ratio measurements and do not identify trace additives or inorganic fillers unless sample preparation accounts for total carbon. Audit documentation should therefore include the certification scope, sample identification, and the exact standard and method used. In European packaging applications, a renewable carbon measurement does not replace conformity to EN 13432 or the applicable compostability certificate. If food-contact use is claimed, migration testing under Regulation (EU) No 10/2011 is also required. The final article must be tested in its actual thickness, surface-to-volume ratio, and intended contact conditions because lactic acid and additive migration depend on the finished part rather than on the polymer resin alone.

Certification bodies such as DIN CERTCO and TÜV Austria operate certification schemes under the relevant compostability standards. The supplier’s certificate number should be verified against the specific product grade and production site. A general brand certificate is insufficient because different INZEA grades can carry different additives, fillers, and thickness limits. The renewable content certificate should also be current: feedstock changes, mass-balance allocation choices, and production location can affect the audit result even if the nominal biobased carbon fraction remains at 80 %.

Compostability, Disintegration Time, and Thickness Limits

Compostability under EN 13432 requires four measurable properties: chemical characterisation for regulated metals and hazardous substances; aerobic biodegradation of at least 90 % relative to a reference within 180 days at 58 °C; disintegration with no more than 10 % residue retained on a 2 mm sieve after 12 weeks; and absence of negative effects in ecotoxicity tests specified by the standard. For high-heat PLA compounds, the filler package can slow disintegration if the mineral content is high or if the part thickness exceeds the certification boundary. Similar criteria apply under ASTM D6400, but the test environment and inoculum are defined by that standard. Industrial compost operators may impose shorter residence times than the laboratory test maximum, so passing the standard does not guarantee acceptance at every facility. Compostability does not imply home compostability or anaerobic digestion compatibility unless a separate certification exists. The property also disappears if the material is commingled with conventional plastics, placed in landfill, or incinerated.

In high-humidity storage, PLA compounds absorb moisture from ambient air. At relative humidity above 60 %, pre-drying is mandatory before melt processing. Storage should be in sealed moisture-barrier packaging, and opened bags should be consumed within one shift or re-dried before use. The material is incompatible with prolonged contact with hot alkaline solutions, strong acids, and certain amine-based additives. For extrusion lines, purging with a suitable PLA purge compound before and after processing is recommended to avoid cross-contamination with polyolefin stock. Residual polyolefin domains reduce impact resistance and create visible delamination at part surfaces. The F28 HT grade should not be specified for continuous service above 100 °C unless the part has been crystallised and tested under the actual service load and environment. Heat deflection data are short-term results; they do not guarantee creep resistance at elevated temperature. Where sustained load-bearing performance is required, creep testing under ISO 899-2 or the relevant application standard should be performed.