Luminy LX175 is processed as a high-viscosity PLA grade for monolayer rigid sheet in thicknesses from 0.20 mm to 1.50 mm. Melt flow rate determined in accordance with ISO 1133-1:2022 at 210 °C under 2.16 kg falls within the extrusion-grade range of 3 g/10 min to 6 g/10 min, with converter validation required for lot-specific control. Pre-drying in a desiccant dryer at 80 °C for 4 h reduces moisture to below 250 ppm; resin exposed to ambient air above 40 % relative humidity can regain sufficient surface moisture within 30 min to reduce melt viscosity and cause lactide reformation. A single-screw extruder with L/D 30:1 and a barrier screw having a compression ratio of 2.8:1 to 3.2:1 delivers a melt temperature of 200 °C to 210 °C. Barrel set points are profiled from 180 °C at the feed throat to 205 °C at the metering zone. A gear pump between the extruder and coat-hanger die is required to stabilize output and reduce gauge variation to ±0.02 mm on polished steel rolls held at 25 °C to 35 °C. High melt strength permits web tension of 8 N/mm² to 12 N/mm² without sag. Thermoforming of the resulting sheet is run at sheet surface temperature 95 °C to 115 °C, measured by contact pyrometer, with plug temperature 70 °C to 90 °C and plug material acetal or syntactic foam. Cavity mold temperature is held at 25 °C to 40 °C for amorphous transparent parts. A draw ratio up to 1.5:1 can be produced with uniform sidewall thickness; draw ratio above 2.0:1 requires plug-assisted pre-stretching and is not recommended without pilot validation. Finished articles include transparent cups, produce trays, and bakery clamshells. Food-contact validation is based on finished-article overall migration testing under EN 1186-1:2002 and limits in Commission Regulation (EU) No 10/2011. ASTM D6400-21 certification applies to industrial compostability claims, not to ambient landfill degradation. US food-contact submissions for PLA are typically supported by an FCN or food-contact statement from the resin supplier; the converter remains responsible for migration and end-use compliance.

What limits draw depth when LX175 sheet enters a plug-assisted cup mold?

Deep-draw cup forming from LX175 sheet is constrained primarily by the narrow thermoforming window and the strain-rate sensitivity of PLA at temperatures near its glass transition. The practical heating window for deep-draw sheet is narrower than for PETG: 100 °C to 115 °C, with a web tolerance of ±3 °C across the forming area. At surface temperatures below 90 °C, amorphous PLA develops stress whitening and microcracks during drawing; above 120 °C, sag becomes severe and premature crystallization haze appears. In plug-assisted forming of a 200 mL cup, plug displacement is set at 60 % to 80 % of cavity depth, plug speed at 150 mm/s to 300 mm/s, and plug temperature at 70 °C to 90 °C. Forming pressure of 4 bar to 6 bar and vacuum of 0.6 bar to 0.8 bar are applied in sequence to hold the sheet against the cavity. Sidewall thickness variation in a 200 mL cup can be controlled to ±0.03 mm if incoming sheet gauge is within ±0.02 mm and heating is uniform. The lower glass transition of PLA at approximately 55 °C to 58 °C means amorphous cups distort above 55 °C under load. For hot-fill above 80 °C, post-mold crystallization at 100 °C to 110 °C for 20 s to 60 s is required. This crystallization step converts part of the amorphous matrix to a crystalline fraction, raising Vicat softening temperature measured by ISO 306/A120 and heat deflection temperature under ISO 75-2/B. Terminal products are cold-fill drink cups, yogurt cups, and thin-wall cup lids where draw depth is moderate and rims require controllable thickness distribution.

For returnable transit trays and material-handling dunnage, heavy-gauge amorphous PLA sheet from Luminy LX175 can be extruded in thicknesses from 2.0 mm to 6.0 mm on a twin-screw or single-screw line fitted with a flex-lip die. The high viscosity maintains sheet integrity at die exit but creates higher melt pressure; gear pump inlet pressure is maintained below 150 bar to avoid shear heating and localized molecular weight loss. Melt temperature is kept at 195 °C to 205 °C, lower than thin sheet extrusion, to limit thermal degradation during extended residence time. The sheet may be cut and reheated for thermoforming into returnable transit trays, internal material-handling trays, and dunnage. These trays are typically non-food-contact but require dimensional tolerance of ±0.5 mm across a 600 mm length. Forming uses double-sided quartz or ceramic infrared heating with sheet surface temperature 100 °C to 120 °C. The heating cycle for 4 mm sheet is 60 s to 90 s, with a soak phase of 15 s to 20 s to equalize core temperature. Molds are aluminum, temperature-controlled at 30 °C to 60 °C. Corners may develop stress cracks if plug assist speed exceeds 250 mm/s or if sheet temperature is below 95 °C. Service temperature of amorphous grades remains limited to 50 °C under continuous load. The trays must not be exposed to high-humidity washdown above 60 °C because hydrolysis accelerates and Charpy impact strength measured by ISO 179-1/1eU can fall below 10 kJ/m² after 500 h of exposure. For applications requiring repeated use, crystallized trays are preferred, but the additional crystallization fixture and dwell time increase piece cost.

When LX175 replaces PETG in medical tray forming

Replacement of PETG with Luminy LX175 in single-use medical procedure trays requires redesign of draw geometry and validation of cold-chain drop performance. PETG sheet typically exhibits elongation at break above 100 %; LX175 sheet typically exhibits elongation at break from 2 % to 10 % when measured according to ISO 527-2. This difference means that thin corners, sharp edges, and vertical walls of a PETG tray design may fail during PLA forming or subsequent distribution. Draft angles above 3° and corner radii above 4 mm are necessary to avoid local stress concentration. Forming is conducted in a cleanroom with sheet surface temperature 100 °C to 115 °C, plug temperature 70 °C to 90 °C, and mold temperature 35 °C to 55 °C. Sterile barrier packaging must meet ISO 11607-1:2019 for seal integrity and package performance. Distribution simulation is conducted under ASTM D4169-22; low-temperature drop tests at 0 °C are required because PLA embrittlement increases fracture risk. Sterilization limitations apply: gamma irradiation above 25 kGy can reduce molecular weight and lower impact strength; ethylene oxide and autoclave sterilization are not recommended due to the low glass transition and hydrolytic sensitivity. Low-temperature hydrogen peroxide gas plasma may be compatible, but published data for this specific grade and tray configuration is limited. RoHS compliance is generally declared at the homogeneous material level under 2011/65/EU because LX175 contains no phthalate plasticizers or halogenated flame retardants. Terminal products are single-use dental procedure trays, syringe nests, and surgical instrument positioning trays that require transparent or translucent visibility.

When a physical blowing agent is injected into a barrier screw, low-density PLA foam sheet can be produced from LX175 at expansion ratios between 1.5 and 3.0. Published data for this specific grade in foam extrusion is limited; process validation on the target line is required before commercial output is established. The high melt strength of LX175 suppresses cell coalescence at the die exit, but it also increases melt pressure and shear heating compared with lower-viscosity PLA grades. A tandem extrusion line with a primary screw L/D 32:1 and a cooling screw L/D 24:1 is used. Barrel temperatures in the secondary extruder are set to 160 °C to 175 °C to lower melt temperature before the annular or coat-hanger die. Physical blowing agents such as CO₂ or nitrogen are dosed at 0.5 wt% to 2.0 wt%, with talc nucleation at 0.5 wt% to 1.0 wt%. Die pressure above 80 bar is needed to keep the blowing agent in solution and avoid pre-expansion inside the die. Cell density, skin thickness, and surface smoothness depend on die geometry, cooling roll temperature, and web tension. Thermoformed foam clamshells for fruit and vegetable packaging are produced from the foamed sheet. The resulting foam is not transparent and cannot be decontaminated in hot-wash systems above 60 °C without distortion. Compostability remains achievable under EN 13432 only if the blowing agent and nucleating additives are listed as acceptable in the certification scope; not all talc surface treatments are automatically compostable.

Crystallization oven dwell and dimensional stability in LX175 lids

Thermoformed PLA lids intended for hot beverage cups require constrained crystallization to raise service temperature from the amorphous limit of approximately 55 °C to the 85 °C to 100 °C range. Lids are transferred from the forming tool into a crystallization oven held at 100 °C to 110 °C for 30 s to 120 s. Crystallinity measured by differential scanning calorimetry under ISO 11357-3 increases to 25 % to 40 % using a reference enthalpy of 93.6 J/g for fully crystalline PLA. Heat deflection temperature under ISO 75-2/B at 0.45 MPa rises accordingly; amorphous LX175 lids show deformation at 55 °C, while constrained crystallized lids can withstand brief contact with liquids at 85 °C. The crystallization step imposes linear shrinkage of 0.3 % to 0.8 %; lid tooling must be dimensionally compensated or the part must be held in a fixture during oven dwell. Warpage occurs when fixture release is premature or when oven airflow creates temperature gradients above 5 °C across the lid diameter. Plug-assisted forming of the lids uses sheet surface temperature 105 °C to 120 °C, forming pressure 4 bar to 6 bar, and plug temperature 80 °C to 95 °C. The final lid rim forms a snap-fit with the cup, so dimensional stability of the rim is critical. Post-crystallization reheat above 110 °C may continue crystallization and shrink the rim beyond 0.5 %, causing leakage. Terminal products are hot cup lids, soup lids, and reusable rigid lids for takeaway containers where moderate heat resistance is needed without PET or PP.