Eco Solution FT1 General Purpose Extrusion Polylactic Acid Resin is a linear, unfilled poly(lactic acid) pellet grade supplied for flat sheet, cast film, profile, and monofilament extrusion. The resin is differentiated from high-flow injection-moulding PLA by its target melt mass-flow rate of 6–8 g/10 min under ISO 1133-1:2022 at 210 °C and 2.16 kg, and by a dry-pellet density of 1.24 g/cm³ per ISO 1183-1:2019. Residual moisture after drying is controlled to below 250 ppm per ISO 15512:2019. The material is a slow-crystallising, unmodified PLA rather than a nucleated high-heat compound or a flexible PLA/PBAT blend.

What distinguishes FT1 from injection-moulding and nucleated high-heat PLA grades?

Injection-moulding PLA grades in the same density range are commonly specified at 15–30 g/10 min under ISO 1133-1:2022 conditions, which favours thin-wall fill but reduces melt strength during unsupported web drawing. FT1 retains higher zero-shear viscosity and greater melt orientation on open flat-sheet lines. Against nucleated high-heat PLA compounds containing talc, calcium carbonate, or sodium benzoate, FT1 contains no crystallisation promoter; its D-lactide content is maintained below 1.5 mol%, which suppresses rapid spherulite growth and permits transparent amorphous sheet. A nucleated PLA can anneal to heat deflection temperatures above 90 °C, whereas unmodified FT1 sheet typically remains at 50–55 °C HDT-B per ISO 75-2:2013 Method B unless a separate annealing step is used.

Against flexible packaging PLA/PBAT blends, FT1 has substantially lower elongation. Tensile yield stress is 60–64 MPa and nominal strain at break is 4–8% per ISO 527-2:2012; PBAT-modified extrusion films can exceed 300% elongation. The tensile modulus of 3.2–3.6 GPa gives sheet and tray walls a stiffness advantage over polypropylene, but the low notched Izod impact strength of 2.5–4.0 kJ/m² per ISO 180/A:2019 limits use in cold-chain or sharp-impact applications.

Capillary rheometry comparisons at 190 °C place FT1 in the medium-viscosity band: apparent shear viscosity at 100 s⁻¹ is typically 180–220 Pa·s, and zero-shear viscosity is approximately 1,800–2,400 Pa·s. This is higher than typical injection-moulding PLA, which often falls below 1,200 Pa·s at the same shear rate, but lower than branched PLA grades designed for extrusion blow moulding. Melt tension measured under Rheotens-type draw at 190 °C on a 2 mm strand is reported in the 18–28 cN range for linear PLA of equivalent MFR; values depend strongly on moisture and draw acceleration.

The values in Table 1 represent the property envelope for linear PLA extrusion grades of this melt-flow class; lot-specific certificates may vary by ±5% on mechanical values and ±1.5 g/10 min on melt mass-flow rate. Published data specific to FT1 in multi-layer barrier structures is limited; target-line qualification is required for oxygen and water vapour transmission claims.

Drying and hydrolysis control extrusion output stability. PLA is a hydrolytically unstable aliphatic polyester; residual moisture above 250 ppm generates random chain scission at melt temperatures. Desiccant-wheel dryers should deliver air at 80 °C with a dew point of -40 °C or lower and a pellet residence time of 4–6 h. When desiccant beds become saturated and the return-air dew point drifts to -20 °C, dried-pellet moisture can increase to 0.05–0.10 wt%, and the apparent melt mass-flow rate may rise by 2–3 g/10 min within a 24 h campaign. This is the most common root cause of sheet edge cracks, die-lip deposit, and output surging on production lines.

For a 45 mm single-screw extruder with 30:1 L/D and a 3-zone barrier screw, a stable FT1 profile is 170/185/195/200/195/190 °C from throat to die, with adapter at 190 °C and die at 190–195 °C. Melt temperature measured by an immersion thermocouple should remain below 210 °C; at 220 °C and above, lactide regeneration and free-acid formation increase, and die-lip residue rises. Screw speeds of 40–80 rpm on a 50 mm line commonly give throughputs of 60–120 kg/h and melt pressures of 60–120 bar. Because linear PLA has a power-law index of 0.45–0.60 at 190 °C, output is more sensitive to screw speed than to die restriction relative to polyolefins.

The 30:1 screw compression ratio should be 2.5:1 to 3.5:1, with feed-section length approximately 20D in a three-zone design and metering-channel depth of 2.5–3.0 mm on a 50 mm screw. If a mixing head is fitted, a low-shear pineapple or Maddock section is acceptable only when backpressure is kept below 120 bar; high-shear barriers can add 10–15 °C melt temperature and reduce molecular weight. Barrel temperatures in the feeding zone should not exceed 180 °C to avoid premature pellet softening and bridging.

Additives and masterbatches should use PLA-compatible carriers. Polyolefin carrier masterbatches create domains that reduce weld-line strength; amine-based antistats and acid-scavenger packages should be avoided because they accelerate molecular weight loss and can raise melt acidity. Inorganic fillers must be predried at 100 °C for at least 4 h before compounding into FT1. Use of reclaim from edge trim and die scrap is practical at 10–30 wt% if the regrind is dried to below 250 ppm moisture and the feed blend is not held at melt temperature for more than 25 min.

In coextruded structures, FT1 is typically placed in the core or printing side because its surface energy is lower than PETG and requires corona discharge above 42 dyn/cm for lamination. Tie-layer selection should be based on polar polyolefin copolymers; unmodified polyethylene tie layers do not adhere to PLA without a surface treatment.

Melt filtration, back-pressure behaviour, and die land selection

Flat-sheet and cast-film operations use breaker plates with screen packs of 20/40/60 mesh or 60/120/60 mesh for higher clarity. Pressure drop across a clean pack is typically 40–60 bar; after 48 h of running with reclaimed edge trim, it may increase to 90–110 bar. A sudden pressure drop below 30 bar suggests screen rupture or channelling. For transparent sheet, the die land length should be 10–15 times the die gap; short lands reduce back-pressure and can produce weld lines or streaks at the die exit.

For transparent amorphous sheet, the polishing roll stack is maintained at 55–65 °C. Roll temperatures below 50 °C produce uneven quench and visible stress, while temperatures above 75 °C increase sticking and wrap-around risk. When a post-extrusion crystallization step is required, the sheet is annealed at 90–100 °C for 15–30 min; this raises crystalline fraction to 35–40% by differential scanning calorimetry per ISO 11357-2:2013 and lifts heat deflection temperature from 55 °C to approximately 85–95 °C.

In a biaxially oriented film process, FT1 can be tentered at stretch ratios of 2.5:1 to 3.5:1 in both machine and transverse directions when the sheet is heated to 70–80 °C. Process temperatures above 90 °C cause premature crystallisation and loss of draw uniformity. These ranges are lower than those for PET or PP, reducing energy input but narrowing the tenter window.

When a desiccant-wheel dryer cannot maintain a -40 °C dew point

Field observations on flat-sheet lines show that desiccant-wheel units operating with saturated media can deliver air at only -20 °C dew point. The resulting pellet moisture of 0.05–0.08 wt% is high enough to suppress melt strength during vertical draw-down; the web tears at the die lip and the edge margin becomes unstable. Raising die temperature is not corrective because it accelerates hydrolysis and lactide deposition. If online moisture measurement is unavailable, pellets should be sampled at dryer discharge and tested by Karl Fischer per ISO 15512:2019 before start-up. In many continuous campaigns, the resin lot itself is not the cause of moisture variation; incomplete regeneration of the desiccant bed is the primary source.

FT1 has an operational ceiling of 230 °C melt temperature and a recommended melt residence time of 15–25 min above 200 °C. Static mixers, long transfer lines, or oversized adapters that increase residence time can produce yellowing; the colour coordinate b* may increase from 2.5 to 6.0 as degradation products form. The resin is not recommended for repeated recycling loops that expose melt above 200 °C for more than 30 min per pass. Use of edge-trim reclaim at 10–30 wt% is acceptable only after drying to below 250 ppm moisture.

The unfilled resin is transparent when quenched; haze of 1 mm injection-moulded plaques is typically below 2% per ISO 14782:2021. Amorphous sheet clarity is highly dependent on roll stack temperature and surface finish; polished chrome rolls and controlled contact pressure are necessary to achieve a surface roughness below Ra 0.1 µm.

Food-contact conformity is article-specific. The base resin can be evaluated under EU Regulation (EU) 10/2011 for overall migration and specific migration of monomers and additives; overall migration must be below 10 mg/dm² under the assigned food simulant and time-temperature conditions. In the United States, the polymer may be assessed under FDA 21 CFR 175.300 or through a food-contact notification for the specific resin formulation. A blanket food-contact approval is not implied. For European industrial handling, the safety data sheet should confirm REACH registration and absence of SVHCs above 0.1% w/w.

In industrial handling, dust-free pellet feed is preferred; a standard feed hopper with a 60° cone operates without bridging under dry-pellet conditions. Pellets exposed to high humidity can become tacky at the feed throat, especially when barrel inlet temperature exceeds 50 °C. Hopper magnets and throat air sweeps reduce contamination risk from fine particles.

In cast film, the die gap is typically set at 0.3–0.6 mm for finished film of 0.2–0.5 mm, with a chill-roll temperature of 35–55 °C and machine-direction draw ratios of 2:1 to 4:1. Draw ratios above 5:1 can exceed the melt strength of FT1 unless melt temperature is reduced to 185–190 °C and the die gap is narrowed. In profile extrusion, wall sections of 1.0–2.0 mm are typical; the calibration block should be maintained at 40–60 °C and the first water-bath stage at 35–45 °C to avoid quench cracks. For monofilament, die hole diameters of 1.0–3.0 mm with an air gap of 10–30 mm before a 35–45 °C water bath and draw ratios of 3:1 to 5:1 provide stable operation.