Futerro PLA Extrusion Clear Extrusion/Thermoforming Sheet Polylactic Acid is a semicrystalline polylactide product designation for monolayer clear sheet extrusion and subsequent roll-fed or cut-sheet thermoforming of rigid articles. The product is based on poly(L-lactic acid) with the linear aliphatic polyester repeat unit [–O–CH(CH₃)–CO–]ₙ, obtained by ring-opening polymerization of lactide. The designation refers to a clear sheet/resin system, not an injection-molding or fiber grade. Published data for this specific Futerro grade configuration is limited; the processing and property boundaries below are drawn from public technical data for semicrystalline PLA extrusion/thermoforming resins and should be confirmed against lot-specific Futerro documentation. The material is applied to clear clamshells, blister trays, portion cups, lids, bakery containers, produce punnets, and cosmetic blisters. Sheet for these formats is commonly specified at 150 µm–2 mm gauge, with optical transmission above 90 % and haze below 3 % on 1.0 mm sheet measured according to ASTM D1003. Density is in the range of 1.24 g/cm³ per ISO 1183-1; melt mass-flow rate for extrusion/thermoforming grades is generally 2–8 g/10 min at 210 °C/2.16 kg per ISO 1133-1:2022. Tensile yield strength is in the range of 50–65 MPa and tensile modulus 3.0–3.5 GPa per ISO 527-2; flexural modulus is 3.0–3.6 GPa per ISO 178; notched Izod impact is 2–4 kJ/m² per ISO 180/A. Glass transition occurs at 55–60 °C and melting endotherm at 145–160 °C per ISO 11357-2/3. These values separate the sheet extrusion grade from Futerro injection-molding and fiber grades, which are formulated with different melt-flow and crystallization kinetics.

What pre-drying and melt-temperature limits prevent hydrolytic degradation during flat-sheet extrusion?

Hydrolysis is the dominant melt-processing failure mode. PLA is hygroscopic, and moisture in the pellet feed reacts through ester cleavage, reducing molecular weight, increasing melt mass-flow rate, and lowering melt strength. On production lines, insufficient drying is observed first as die-lip drool, melt curtain instability, microbubbles, or random haze bands. The resin is pre-dried in a desiccant bed at 80 °C for 4 h to residual moisture below 250 ppm, measured by ISO 15512 Karl Fischer titration. A dry-air hopper with dew point below -40 °C is required; unprotected transfer at 23 °C and 50 % RH can reintroduce process-limiting moisture within minutes. Regrind is limited to 30 % by weight and re-dried under identical conditions, because multiple heat histories reduce molecular weight and raise carboxylic acid end-group concentration. If pellet moisture exceeds 500 ppm, drying time is extended beyond 4 h, and melt viscosity loss becomes measurable as an upward shift in melt mass-flow rate.

Flat-sheet extrusion is performed on single-screw extruders with 30:1 to 36:1 L/D, barrier-flight screws, and vacuum venting. Barrel temperatures are generally set from 180 °C to 210 °C, with adapter and sheet die temperatures near 200 °C. Sustained melt temperatures above 230 °C accelerate lactide reformation, yellowing, and thermal degradation. The melt is shear-sensitive; high screw speed or restrictive die gaps can generate frictional heating that is not reflected in barrel set-points. Melt pressure at the die lip is maintained below the onset of melt fracture, and polished die lips are used to preserve surface smoothness. The melt is cast onto a chrome-plated three-roll stack with roll temperatures held at 20–40 °C to quench the web to an amorphous state. Roll temperatures above approximately 60 °C can induce cold crystallization and haze. Edge bead control, vacuum trim, and independently heated die zones are used to maintain sheet gauge variation below ±5 % of nominal for stable thermoforming.

The upper processing limit is lower than that of PET. PLA sheet typically processes near 200 °C, whereas PET sheet extrusion normally operates at 270–300 °C. This lower melt-temperature ceiling requires tighter thermal control and places greater demand on screw design to avoid unmelted polymer at low stock temperatures and local overheating at high shear.

On roll-fed thermoforming lines with zoned ceramic or quartz IR ovens, clear extruded sheet is heated to a surface temperature of 90–120 °C depending on gauge, orientation state, and line speed. The forming window is narrower than amorphous PET because PLA undergoes rapid cold crystallization above 100 °C, which can freeze orientation and produce visible haze. Plug-assist tools made from syntactic foam or PEEK are used to reduce surface sticking and heat transfer from the plug. For amorphous clear parts, mold temperatures are held at 20–40 °C to preserve optical clarity and reduce cycle time. When heat-set thermoforming is specified, mold temperature is raised to 100–110 °C to permit lamellar thickening and improve dimensional stability at the expense of haze. Published data for this specific Futerro grade is limited; heat-set PLA resins generally require low D-lactide content, often below 2 mol%, because stereochemical defects depress the maximum obtainable crystalline fraction. Unannealed sheet has a heat deflection temperature of 50–60 °C at 0.455 MPa per ISO 75-2/B, so continuous service above 45–50 °C is not recommended for clear amorphous parts. Draw ratios above 3:1 can create localized thinning at pinch points and hinge regions; plug displacement, pre-blow timing, and mold venting are adjusted to avoid orientation-induced stress concentration. The notched Izod impact of 2–4 kJ/m² per ISO 180/A indicates brittle failure in thin-wall parts; living hinges and snap-fit features should be radiused and aligned to avoid crack propagation perpendicular to the extrusion direction.

When 150 µm–2 mm clear sheet enters finished-food-contact packaging, compliance follows the finished-article doctrine.

Regulatory status is not determined solely by resin composition. For European food-contact use, the finished article must comply with Commission Regulation (EU) No 10/2011, including overall migration limits of 10 mg/dm² or 60 mg/kg depending on the food simulant and contact ratio. Specific migration of residual lactide, lactic acid, and any processing aids is assessed under the intended time–temperature conditions. In the United States, PLA is not automatically covered by 21 CFR 177.1520, which addresses olefin polymers; food-contact status for PLA resins is generally established through a Food Contact Notification or other FDA clearance for the specific grade and conditions of use. The converter must verify that the final sheet and formed article meet the relevant migration limits under the actual food type, temperature, and contact duration.

Industrial compostability claims for PLA packaging should be based on certification of the finished article to EN 13432 or ASTM D6400. These standards require aerobic biodegradation of at least 90 % of organic carbon to CO₂ within 180 days, disintegration with at least 90 % of material passing a 2 mm sieve after 12 weeks, and compliance with ecotoxicity and heavy metal limits. Home compostability should not be assumed; separate certification to a standard such as AS 5810 or NFT 51-800 is required. Under REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU, the product is supplied with substance declarations and does not require the cadmium- or lead-based stabilizers typical of some PVC formulations.

Barrier performance in formed articles is not directly equivalent to flat-sheet data because thermoforming induces variable wall thinning and localized orientation. Oxygen permeability of PLA at 23 °C and 0 % RH is typically 40–60 cm³·mm/m²·day·atm per ASTM D3985; at 50 % RH, permeability may rise to 80–120 cm³·mm/m²·day·atm as water plasticizes the amorphous regions. Water vapour transmission rate at 23 °C and 85 % RH is commonly 15–25 g·mm/m²·day per ISO 15106-2. Carbon dioxide permeability is typically 3–5 times the oxygen permeability, which is relevant for respiring produce packaging. Permeability coefficients increase sharply as service temperature approaches the glass transition; at 40 °C, oxygen permeability can be substantially higher than at 23 °C. These properties place the material between PET and PS for oxygen barrier and below PET for moisture barrier. Shelf-life modelling for food packaging therefore requires normalized transmission rate data integrated over the actual time–temperature distribution rather than single-point values at ambient room temperature. Formed articles with wall thickness below 200 µm may require additional barrier coatings or multilayer structures if shelf-life targets exceed the intrinsic permeability of PLA.

Comparative property boundaries against PET, PP, and amorphous PLA

The combination of lower density, moderate stiffness, and renewable carbon differentiates this PLA extrusion/thermoforming sheet from comparative clear rigid packaging substrates. Compared with PET, the PLA density is lower (1.24 g/cm³ versus 1.33 g/cm³), but heat deflection temperature is substantially lower, limiting hot-fill and retort use. Compared with polypropylene, the tensile modulus is higher, but notched impact strength is lower, making PP more ductile in thin-wall closures. Compared with polystyrene, PLA provides lower oxygen permeability at chilled temperatures but has lower water-vapour resistance than PET. Compared with amorphous PLA injection grades, the extrusion/thermoforming designation uses a lower melt mass-flow rate and higher melt strength to resist draw resonance; however, the resin remains unsuitable for extrusion blow molding or stretch blow molding unless a dedicated high-melt-strength or crystallizable grade is selected. The table below summarizes representative public property ranges for clear rigid packaging substrates.

These comparative values are representative general ranges from public polymer data; the Futerro grade-specific values should be taken from the technical data sheet and not from the table alone.