Hycail HM 1011 Clear General Purpose Extrusion/Thermoforming Polylactic Acid is an amorphous, high-clarity polylactide grade supplied as pellets for flat-die sheet extrusion and subsequent thin-gauge thermoforming. The designation HM 1011 identifies a general-purpose molecular weight distribution tuned for melt strength, sheet gauge stability, and optical clarity; it is not a nucleated high-heat compound and is not an impact-modified blend. As an aliphatic polyester derived from lactic acid, the material is subject to hydrolytic chain scission at melt temperature if residual moisture exceeds the supplier limit. The processing and property values compiled below are drawn from supplier technical literature and standard polymer engineering practice; lot-specific certificates of analysis control actual release limits for specific production campaigns.

Before extrusion, pellets must be dried in a desiccant dryer at 80 °C for 4 h to a residual moisture content below 250 ppm. Drying air with a dew point of -40 °C or lower and airflow of 3.7 m³/h per kg/h pellet throughput are required. If dried pellets remain in open hoppers for more than 1 h at ambient relative humidity above 60%, surface moisture re-adsorption is sufficient to produce molecular weight loss and edge curl on the sheet line. Overdrying above 100 °C causes pellet surface tack and bridging; therefore, hopper temperature setpoints above 100 °C are not recommended without continuous agitation. Moisture content should be verified by Karl Fischer titration or an equivalent calibrated moisture analyser, not by weight-loss methods alone, because PLA pellets can release volatiles that distort loss-on-drying readings.

Thermal and rheological limits on flat-die sheet extrusion

On a single-screw extruder with 24:1 to 30:1 L/D and a barrier screw, melt temperature at the die is held at 190 °C to 210 °C. Die zone temperatures are normally 200 °C to 220 °C; polished roll stacks between 25 °C and 40 °C quench the amorphous sheet before spherulite growth occurs. The material’s melt volume-flow rate at 190 °C/2.16 kg under ISO 1133-1 falls in the range of 6 g/10 min to 10 g/10 min, providing moderate melt strength but a narrow sag window. A die gap of 1.5 to 2.5 times the target sheet thickness is used because PLA has lower melt strength than polystyrene or polyethylene terephthalate; excessive draw-down creates gauge variation and machine-direction orientation. Screen packs of 40/80/40 mesh are standard. Extruder head pressure above 250 bar indicates either insufficient melt temperature or screen blockage; sustained operation above 240 °C promotes lactide reformation, racemisation, and yellowing.

Production-scale flat-die lines have shown that melt pressure fluctuation above ±5 bar causes visible gauge bands in thin sheet. Barrel zones are profiled from approximately 170 °C at the feed throat to 200 °C at the metering zone, with the feed throat maintained below 45 °C to prevent pellet bridging. Screw speed is set to maintain a metering-zone fill factor above 80%; starved feeding above 85% fill may improve devolatilisation but reduces output stability unless controlled by a gravimetric feeder. Melt residence time above 220 °C should be minimised because thermal degradation follows a time-temperature superposition; long residence times at lower temperatures can produce the same lactide reformation as short residence times above 240 °C.

Optical clarity in HM 1011 is process-dependent. Rapid quenching on the roll stack is required to suppress spherulite growth; roll temperatures above 40 °C or melt temperatures above 230 °C increase haze and shift transmitted colour toward yellow. Light transmission measured on 1 mm plaques under ASTM D1003 is reported in the range of 90% to 94%, with haze below 3%. The grade is not externally lubricated; therefore, surface migration during storage is minimal, and corona discharge treatment for printing or lamination should be applied at 38–44 dyn/cm for consistent surface energy. Crystalline content in the amorphous sheet should remain below 5%; crystallinity above this level produces stress whitening at thermoformed corners and dimensional instability after trimming.

Primary application formats include clear clamshell packaging, display trays, lids, cups, and thin-gauge blisters for ambient or cold-chain products. The unannealed heat deflection temperature remains below 60 °C; therefore, the material is not recommended for hot-fill containers or microwave reheating unless the part is crystallised after forming. Published data for high-speed plug-assisted forming of this specific grade is limited; the forming window is therefore defined by the measured glass transition and cold-crystallisation onset in supplier technical literature.

What separates HM 1011 from high-heat and impact-modified PLA grades?

HM 1011 is differentiated from high-heat PLA by the absence of nucleating agents such as talc, phenylphosphonic acid zinc salt, or stereocomplex PDLA additives. High-heat grades crystallise during annealing at 100 °C to 120 °C and can achieve heat deflection temperatures above 100 °C at 0.45 MPa under ISO 75-2/B; unannealed HM 1011 remains below approximately 55 °C. Compared with impact-modified PLA, HM 1011 offers higher tensile modulus and optical clarity but lower ductility: notched Charpy impact strength measured under ISO 179-1/1eA is typically below 4 kJ/m², whereas impact-modified extrusion grades can exceed 20 kJ/m² but exhibit haze above 5% and tensile modulus below 2600 MPa.

Compared with injection moulding PLA grades, HM 1011 is deliberately less fluid: its melt volume-flow rate of 6–10 g/10 min at 190 °C/2.16 kg is lower than typical injection moulding PLA grades at 15–30 g/10 min. This lower fluidity is required because sheet extrusion depends on melt strength to support the web from die to roll stack; an injection moulding grade would sag excessively and produce gauge variation. Conversely, HM 1011 is not recommended for thin-wall injection moulding because filling pressure would be higher and weld-line strength lower than with grades designed for that process.

When thin-gauge packaging tools are run above 100 °C

When thin-gauge packaging tools are run above 100 °C, the amorphous sheet enters the crystallisation regime. The HM 1011 preheat window is 90 °C to 110 °C, with aluminium tooling maintained at 30 °C to 50 °C for clear parts. Tool temperatures above 60 °C cause spherulite growth, haze increase, and dimensional instability because the part shrinks as it crystallises. Forming pressures of 3 bar to 5 bar and plug assist are typical on continuous thermoforming lines; plug temperature should not exceed 80 °C, because a hot plug induces premature crystallisation on the sheet surface. After trimming, residual stress in corners can be reduced by annealing at 80 °C for 30 min, but the anneal will reduce transparency and raise heat deflection temperature because crystallinity increases. Edge trim regrind can be reintroduced at 20 wt% to 30 wt%; repeated heat histories lower melt viscosity, so higher regrind levels increase gel formation and black specks. Sheet surface temperature uniformity should be maintained within ±2 °C across the forming area, verified by infrared pyrometry, to avoid non-uniform stretching and corner thinning.

For food-contact articles, compliance must be established for the specific converted part. PLA grades of this class are commonly evaluated under EU 10/2011 for overall migration in food simulants such as 10% ethanol, 3% acetic acid, and vegetable oil; the supplier of HM 1011 must provide the relevant migration data. Under United States regulations, PLA food-contact status is typically addressed through Food Contact Notifications rather than 21 CFR 177.1520, which covers polyolefins. Industrial compostability claims must reference EN 13432 or ASTM D6400; successful degradation depends on a managed composting environment at 58 °C ± 2 °C with sufficient moisture and oxygen. HM 1011 does not degrade in ambient landfill or marine conditions. RoHS and REACH declarations must be obtained from the supplier for the specific lot, because additive packages may vary by production site.

Storage of unopened bags should be maintained at 25 °C and 50% RH or lower. If bags are opened for more than 8 h, re-drying before extrusion is mandatory. Condensation during transfer from cold storage to a warm production area must be prevented; immediate pellet feeding from an unheated silo can produce surface moisture which hydrolyses the melt. HM 1011 should not be combined with strong bases, amines, or alkaline fillers because alkaline species catalyse ester hydrolysis and molecular weight loss. Prolonged contact with ketones, esters, and aromatic hydrocarbons can swell or stress-crack the formed article, and the material is not recommended for continuous service above 50 °C in the amorphous state.