ECOPLAN-FLEX is a flexible heat-sealable compostable polylactic acid compound supplied as cylindrical pellets for blown film, cast film, extrusion coating, and lamination to paper or cellulose-based substrates. The model designation is ECOPLAN-FLEX; the datasheet identifies a film-grade formulation with a melt-flow rate of 4.5 g/10 min at 210 °C and 2.16 kg under ISO 1133-1:2022. The polymer is based on high-optical-purity PLA resin modified with a renewable biodegradable soft segment. The exact modifier system is proprietary, but the manufacturer’s technical datasheet reports that all constituents are selected for compliance with EN 13432:2000 and ASTM D6400-19. Density is 1.24 g/cm³ under ISO 1183-1:2019. Residual moisture after desiccant drying is specified below 250 ppm using a dryer dew point of -40 °C. The material is intended for monolayer and coextruded flexible packaging where the heat-seal layer must carry the same compostability certification as the bulk structure.

Which Property Shifts Separate Flexible Heat-Sealable PLA from Rigid PLA and PBAT Blends?

Unmodified PLA extrusion film typically exhibits a 1% secant modulus near 3,200 MPa and elongation at break below 5%, which restricts its use to rigid thermoformed trays, labels, or lightly flexed structures. Polybutylene adipate terephthalate blends improve elongation to 400–600% but reduce renewable carbon content and increase haze. ECOPLAN-FLEX occupies an intermediate position: the manufacturer’s datasheet lists a 1% secant modulus of 900 MPa in machine direction, elongation at break of 160–210%, and Gardner haze of 5–7% on 30 µm blown film measured under ISO 14782:2021. The same document reports seal initiation at 88 °C under 0.5 s dwell and 3 bar jaw pressure, compared with 120–140 °C for unmodified PLA. This lower seal threshold reduces form-fill-seal jaw setpoint by 30–50 K and allows sealing against cellulose-based substrates without heat-damaging the fibre.

On a 45 mm co-rotating twin-screw extruder with L/D 30 and vacuum venting, ECOPLAN-FLEX pellets are processed with a flat temperature profile of 145 °C to 155 °C from feed throat to die adapter. Melt temperature must remain below 160 °C; excursions above 165 °C generate lactide and reduce melt strength, visible as surging at the die and uneven gauge bands of ±3 µm on a 25 µm target film. Pre-drying at 70 °C for 4 h in a desiccant dryer with air dew point -40 °C is required. Residual moisture above 300 ppm produces hydrolysis-induced viscosity loss and melt-pressure fluctuation of ±2 bar. Capillary rheometry according to ISO 11443:2021 at 150 °C gives shear viscosity of 320 Pa·s at 100 s⁻¹, 105 Pa·s at 500 s⁻¹, and 45 Pa·s at 1,000 s⁻¹. The measured shear-thinning exponent is 0.42. Film converters should not exceed a melt residence time of 8 min at 150 °C; longer residence shifts the melt-flow rate from 4.5 g/10 min to 6.5 g/10 min and degrades hot-tack performance.

Blown film towers running 20–40 µm gauge typically use die temperature 150 °C, blow-up ratio 2.2–2.6, and frost-line height 300–500 mm above the die. On a 65 mm line at 120 kg/h, film contact with unheated metal surfaces below 30 °C causes condensation and increases blocking. Maintaining the collapsing frame at 35–40 °C reduces web breaks. Extruder vent vacuum should be maintained at -0.8 bar; loss of vacuum allows moisture and lactide to degrade the polymer. When moisture reaches 300 ppm, apparent melt viscosity at 100 s⁻¹ falls to 220 Pa·s and screw torque drops by 18%. This shift is accompanied by an increase in acetic acid at the die, indicating ester hydrolysis.

When Corona Treatment Is Omitted, Seal Strength Fails on High-Speed Vertical Form-Fill-Seal Lines

ECOPLAN-FLEX film surfaces at extrusion have surface energy of 38–40 mN/m. After offline corona treatment at 4 kW and 30 m/min, surface energy rises to 50–52 mN/m measured by ISO 8296:2003. Without treatment, water-based flexo inks and cold-seal adhesives may exhibit wetting failure, and heat-seal strength can drop by 20–30% when the seal area is contaminated with dust or release agents. On a vertical form-fill-seal machine running 80 bags/min, a jaw temperature of 95 °C and contact pressure of 0.4 MPa with 0.2 s dwell produce seal strength above 6 N/15 mm on 30 µm film per ASTM F88/F88M-21. Reducing dwell to 0.1 s at the same temperature lowers seal strength to 3–4 N/15 mm, which remains above open-bag breakage thresholds for dry products but may fail for oils or frozen goods. Hot-tack strength at 95 °C is 2.0–2.5 N/15 mm per ASTM F1921-18. Sealing through folds or gussets reduces effective seal strength by 15% and requires a 5 K higher jaw setpoint.

Differential scanning calorimetry under ISO 11357-3:2018 shows a broad melting endotherm from 140–155 °C and a cold-crystallisation peak at 95 °C when heating at 10 K/min. Heat-seal initiation at 88 °C should not be interpreted as melting. Sufficient molecular interdiffusion occurs after the amorphous phase reaches 15 °C above the glass transition of 55 °C. The seal temperature window for consistent hot-tack is ±5 K around 95 °C. Below 88 °C, seal strength is below 1 N/15 mm; above 105 °C, film distortion and squeeze-out can occur on monolayer structures.

Compostability testing under EN 13432:2000 requires chemical characterisation, ultimate aerobic biodegradation, disintegration, and ecotoxicity. The manufacturer’s technical dossier reports 92% biodegradation after 180 days under ISO 14855-1:2012, 90% disintegration through a 2 mm sieve after 12 weeks under ISO 16929:2021, and ecotoxicity outcomes within OECD 208 germination limits. EN 13432:2000 clause 4.2.2 permits 10% residual non-biodegradable solids; the grade’s residual fraction is dominated by mineral fillers. ASTM D6400-19 follows similar thresholds but uses ASTM D5338-15 for biodegradation. Compostability certification does not imply marine or home-compost acceptance. The grade requires industrial composting conditions above 58 °C and is not certified for home compost unless separately labelled.

The product is not intended for retort, hot-fill above 80 °C, or microwave reheating because PLA undergoes hydrolysis and loss of seal integrity. Continuous storage above 50 °C and 85% RH can decrease molecular weight within weeks. Packaged goods should be stored below 35 °C. Avoid amine-containing masterbatches and metal stearate levels above 0.5 wt%; these additives accelerate ester cleavage and shift seal initiation upward. The grade is formulated with raw materials listed under EU Regulation No 10/2011 and FDA 21 CFR 175.300 for specified food types, but migration testing per EN 1186-1:2002 is recommended for each final package geometry and food-contact ratio.

Acceptable converting routes include blown film at 20–40 µm, cast film at 15–50 µm, extrusion coating onto paper at 10–20 g/m², and lamination to cellulose or starch-based films. When extrusion coating onto kraft paper, corona treatment at 2.5 kW is required; peel strength above 2 N/15 mm is obtained on 80 g/m² uncoated kraft under TAPPI T-540 om-20. For extrusion lamination onto metallised paper, published data for this specific configuration is limited; pilot trials should first qualify coating weight, corona treatment, and storage humidity.