Ecopond Flex-64D is a flexible polylactic acid compound formulated for monolayer blown and cast film extrusion where the converter requires polypropylene-like handling and ductility without moving to a non-compostable polyolefin. The product designation identifies a target Shore D hardness of 64 after conditioning at 23°C and 50% RH for 40 h according to ISO 868, placing it between rigid PLA packaging grades typically above 80 Shore D and high-modulus PBAT/PLA extrusion compounds below 55 Shore D. Manufacturer-reported values for density are 1.25 g/cm³ (ISO 1183-1), melt flow rate 4.0 g/10 min at 190°C/2.16 kg (ISO 1133-1:2022), and melting endotherm onset 155°C with peak 162°C by differential scanning calorimetry at 10°C/min. The compound is supplied as cylindrical pellets with a bulk density of 0.78 g/cm³; pellet geometry permits gravimetric blending with PLA regrind at up to 20 wt% before melt strength and dart impact decline below target film specifications.

What limits the practical melt processing window of Ecopond Flex-64D?

Pre-extrusion moisture is the controlling boundary condition. Residual moisture above 0.025 wt% by Karl Fischer titration (ISO 15512) reduces molecular weight through hydrolytic ester cleavage; at a melt temperature of 180°C, films produced from pellets with 0.05 wt% moisture exhibit a melt flow rate increase of 0.8 g/10 min and a reduction in tear initiation resistance of 15–20% when compared to dried control film. Drying in a desiccant dryer at 80°C for 4 h to a dew point of -40°C is required when ambient relative humidity exceeds 60%, and dried pellets must be conveyed in closed vacuum loaders to the extruder throat to limit moisture reabsorption.

Extrusion on a single-screw line with L/D 30:1 to 36:1 and a barrier screw with compression ratio 3.0:1 to 3.5:1 is recommended. Barrel set temperatures from hopper to die are 160°C, 170°C, 175°C, 180°C, and 180°C; die melt temperature must be held at 175 ± 5°C. Output rates are constrained by screw speed rather than thermal homogeneity, and melt pressure before the screen pack should not exceed 350 bar. Pressures above 350 bar on a 60 mm extruder with 30 L/D have produced shear heating and gel formation from the flexible ester phase. Screen packs of 60/80/100 mesh are employed for cast film; blown film lines benefit from a 100/80/60 mesh reverse pack to avoid pressure spikes during start-up.

The principal compositional distinction from unmodified PLA film grades is the presence of a flexible aliphatic ester phase. Unmodified PLA film at 25°C typically fails in tension at 5–10% elongation with necking; Ecopond Flex-64D, when converted as cast film at 25 µm, exhibits tensile elongation at break above 200% in the machine direction and 150% in the transverse direction under ASTM D882-18. The flexible phase also suppresses the sharp yielding peak observed in standard PLA, producing a lower secant modulus closer to that of polypropylene random copolymer. The property table below summarises comparative data for conditioned film samples.

Tensile, Tear, and Impact Response Measured Against ASTM Film Protocols

Data in the following table are representative of monolayer cast films at 25 µm thickness conditioned for 48 h at 23°C and 50% RH. Comparative values for unmodified PLA film and propylene random copolymer film are included to define the mechanical position of Ecopond Flex-64D. Published intergrade comparisons at identical thickness and processing history are limited, and converter-specific data should be generated for final lot acceptance.

On a 45 mm blown film line with 30 L/D barrier screw, die diameter 150 mm, die gap 1.2 mm, and lip cooling ring, stable bubble formation has been observed at blow-up ratios 2.5:1 to 3.5:1 and frost line heights 150–300 mm above the die. Bubble instability occurs below 2.0:1 when the outer skin cools below the crystallisation onset before molecular orientation is set; at blow-up ratios above 4.0:1, the melt strength is insufficient to resist transverse stretching forces, producing gauge bands of ±5 µm on a 25 µm target. Cast film trials on a 750 mm coat-hanger die with 0.8 mm lip gap and 18–22°C chill roll temperature show acceptable layflat width contraction after slitting of 1.5–2.5 mm/m, but edge neck-in is higher than PP at the same air-knife position; operators position the air-knife at +2 mm relative to the die edge to maintain edge thickness.

Batch-to-batch variance in melt flow rate has been recorded at ±0.4 g/10 min across production lots when the flexible ester phase is fed by separate gravimetric dosers; this variance is sufficient to shift blown bubble stability on thin-gauge films below 15 µm. Converters running below 15 µm should pre-qualify each lot by capillary rheometry at 180°C and 100 s⁻¹, accepting only lots with shear viscosity between 900 Pa·s and 1200 Pa·s at that shear rate. Below 900 Pa·s, draw resonance in cast film appears at line speeds above 80 m/min; above 1200 Pa·s, melt pressure on a 60 mm extruder rises by 10–15%.

Avoid combining the compound with primary or secondary amine-based slip or antiblock masterbatches used in polyolefin film lines. Amine-bearing additives can promote chain scission in PLA during extrusion and can generate a pH shift that accelerates hydrolysis in stored film. If slip is required, erucamide loading should be limited to 0.1–0.3 wt% and verified by coefficient of friction testing under ISO 8295; above 0.3 wt%, surface bloom may reduce ink adhesion to below 3 N/15 mm in tape adhesion testing. Antiblock should be synthetic silica or talc, not calcium carbonate, at 1–3 parts per hundred resin; calcium carbonate at equivalent loading increases film haze by 4–6% and reduces tear propagation resistance in the machine direction.

Compostability Certification Does Not Automatically Confirm Food Contact

End-articles made from Ecopond Flex-64D may be submitted for certification under EN 13432:2000 or ASTM D6400-21 provided the final film thickness does not exceed the maximum allowed by the certifying body. Biodegradation of PLA proceeds through a two-step hydrolytic degradation followed by microbial assimilation; the flexible ester phase does not alter the overall disintegration profile if present below a threshold that the compounder has not publicly disclosed. Composting test data for similar PLA/flexible ester films at 58°C and 50% moisture show greater than 60% mineralisation within 180 days, but published data for this specific Flex-64D formulation is limited. Converters are advised to request a third-party certification certificate for each film thickness, colour masterbatch, and print ink combination.

For food contact, compliance must be verified under EU 10/2011 or FDA 21 CFR 175.300 as applicable to the final food type and simulant. PLA polymers are not automatically cleared for all food-contact uses. The presence of the flexible ester modifier introduces an additional migration variable; overall migration into 3% acetic acid and 10% ethanol should be below 10 mg/dm² of food contact surface when tested according to EN 1186-1. The material carries no halogens, and a RoHS screening under IEC 62321-3-1 for lead, mercury, cadmium, and hexavalent chromium is expected to fall below the maximum concentration values in EU 2011/65/EU Annex II. The compliance matrix below summarises the material position.

When flexible cast film replaces polypropylene in non-durable packaging

Ecopond Flex-64D can be evaluated for monolayer packaging where the article is expected to enter an industrial composting stream. Suitable conversion targets include produce bags, magazine overwrap, flow-pack film for dry bakery items, and document envelopes. In these applications, converter trial data on vertical form-fill-seal lines indicate heat-seal initiation at 82°C and a plateau seal strength of 8–12 N/15 mm when sealed at 105°C, 0.3 s dwell, and 0.4 MPa jaw pressure. The seal window is narrower than PP; seal strength falls below 6 N/15 mm below 78°C and film puckering occurs above 115°C because the outer film surface approaches crystallisation and shrinks. This boundary limits process tolerance on older form-fill-seal machines with analogue temperature control, where a ±10°C jaw swing can produce weak seals or localised edge curl.

Cold-temperature resistance is lower than PP. Charpy notched impact tests on extruded sheet at -10°C show a 30–40% reduction relative to 23°C values, and film that is flexed at -20°C may develop stress whitening. Therefore, the product is not assigned for deep-freeze packaging or for applications requiring repeated flexure below 0°C. The compound should not be specified for hot-filled liquids, retort, microwaveable trays, or contact with high-ethanol food simulants above 10% unless migration testing under EU 10/2011 demonstrates compliance for the specific food category.