INZEA F15C Transparent Flexible Sealable Film Polylactic Acid is a PLA-based thermoplastic compound supplied by Nurel Biopolymers for monolayer and coextruded film applications where optical translucency, low sealing initiation temperature, and industrial compostability must be specified simultaneously. The pelletized grade is formulated from polylactic acid and non-aromatic biodegradable modifiers that reduce film stiffness relative to standard PLA without introducing petrochemical polymer fractions. On 50 µm cast film conditioned at 23 °C ± 2 °C and 50 % ± 10 % relative humidity for 48 h, the supplier datasheet lists machine-direction tensile strength of 38–44 MPa, machine-direction elongation at break of 150–180 %, and secant modulus of 1.8–2.2 GPa. Melt flow index measured according to ISO 1133-1:2022 at 190 °C with 2.16 kg load is typically 2.0–4.0 g/10 min. Polymer density is 1.24 g/cm³. Unlike standard PLA film grades whose elongation at break is frequently below 10 % and whose seal initiation exceeds 120 °C, the F15C modification lowers the seal initiation temperature to approximately 85 °C and provides a heat-seal plateau at 110–130 °C. Compared with low-density polyethylene films, the grade is industrially compostable and biodegradable but offers lower moisture-barrier performance and a narrower heat-seal window.

The grade is suited to flexible packaging film, flow-wrap, lamination sealant webs, and produce-bag applications. It is processable on conventional cast film and blown film equipment, provided drying and thermal controls are enforced. The material is not recommended for retort, hot-fill above 60 °C, microwave, or ovenable packaging because the flexible additive system and PLA matrix can undergo excessive migration and dimensional change. In all final structures, food-contact status is dependent on layer composition, final thickness, and the specific food simulant used under EU Regulation 10/2011 and relevant FDA food-contact provisions.

What Processing Constraints Govern Moisture and Residence Time in INZEA F15C?

The principal failure mode in extrusion is hydrolytic degradation. PLA hydrolyzes rapidly at melt temperatures above 180 °C when free moisture exceeds 250 ppm. Supplier guidance specifies pre-drying at 80 °C for 4 h in a desiccant dryer with a dew point of −40 °C or lower, targeting residual moisture below 250 ppm by ISO 15512:2019. Dried pellets should not remain in an open hopper for more than 30 min unless blanketed by dry air at a dew point of −40 °C or lower. In production trials, failure to maintain this boundary caused a reduction in melt viscosity of 15–25 % within 20 min of hopper residence and produced gel defects in blown film. The processing risk is highest at start-up after weekend shutdowns, when residual pellets in the feed throat and hopper have adsorbed atmospheric moisture.

Barrel temperature profiles are normally set from 150 °C at the feed throat to 190 °C at the metering section; melt temperature is maintained at 190–205 °C. A 30:1 L/D single-screw extruder with a barrier screw and a compression ratio of 2.5:1–3.5:1 is recommended for cast film. Blown film lines typically use a 0.8–1.2 mm die gap and a blow-up ratio of 2.0:1–2.5:1. The melt displays shear-thinning rheology; apparent viscosity at 190 °C and 100 s⁻¹ is approximately 300–600 Pa·s, although published data for this specific configuration is limited. Above 210 °C, lactide reformation and thermal degradation accelerate. The melt temperature window is therefore 190–205 °C, and residence time above 210 °C is limited to less than 5 min. Screw speeds above 80 rpm on a 50 mm extruder have been associated with localized melt temperature excursions above 210 °C and die-lip deposit formation. The die pressure should be monitored continuously; a drift of more than 10 % from the stabilized value indicates viscosity degradation or feed instability.

Recycled edge trim may be reintroduced at up to 20 wt%, but the recycled fraction must be dried to the same moisture specification as virgin pellets because regrind increases surface area and moisture uptake by 3–5 times relative to pellets in humid environments. Higher regrind fractions above 20 wt% reduce transparency and lower heat-seal strength by 10–15 % on production-scale trials because the biodegradable modifier package undergoes secondary thermal oxidation. For blown film, a chill air temperature of 10–15 °C and a frost line height of 1.5–2.0 die diameters are used to stabilize the bubble. Cast film processing uses an air gap of 5–10 mm and a chill roll temperature of 20–30 °C. Die-to-nip distance should be limited to 10 cm or less, as the melt curtain has lower melt strength than LDPE and can draw-resonate at high line speeds.

When Seal Integrity and Optical Haze Are Specified in the Same Layer

Heat-seal performance is determined according to ASTM F88/F88M-21 on 25 mm wide strips sealed at 0.3 MPa for 1.0 s. The seal initiation temperature, defined as the jaw temperature at which seal strength reaches 4.0 N/15 mm, is approximately 85 °C on 50 µm cast film. Seal strength plateaus between 110 °C and 130 °C at 8.0–12.0 N/15 mm. Above 140 °C, the film shrinks and whitens at the seal edge because localized crystallization and chain orientation relax nonuniformly. This thermal boundary is narrower than the heat-seal range of LDPE, which typically remains sealable up to 160 °C without shrinkage. Horizontal form-fill-seal machines must therefore maintain jaw-temperature uniformity better than ±5 °C. Uneven jaws above 135 °C produce channel leaks, seal-edge stress whitening, and intermittent seal-strength drops below 4.0 N/15 mm.

Optical quality is evaluated with ASTM D1003-21. On 50 µm cast film, total luminous transmittance is above 90 %, and haze is typically 6–10 % when the melt temperature is kept below 205 °C and the chill roll temperature is maintained at 20–30 °C. Melt temperatures above 210 °C raise haze by 2–4 percentage points and increase the b* yellowness index. For film structures requiring haze below 5 %, F15C should be confined to the sealant layer of a coextrusion and not used as the outer structural layer, because additive migration and surface roughness increase under storage at 40 °C. Blocking resistance is measured by ASTM D3354-21 at 40 °C and 50 % relative humidity; typical film-to-film blocking load is below 5.0 g/cm. The balance between seal initiation and blocking is the key formulation difference from flexible PLA compounds with higher plasticizer contents, which may lower seal initiation further but exhibit blocking at 45 °C and unacceptable coefficient of friction on vertical form-fill-seal machines.

Surface properties are relevant to machine performance. Coefficient of friction measured by ISO 8295:2023 is typically 0.30–0.50 on the untreated cast film. If the film is to be used on high-speed horizontal form-fill-seal lines, a slip additive or corona treatment may be required, but any post-treatment alters seal behavior and must be revalidated. Preprint converters should avoid solvent-based inks with strong ketone content because PLA is susceptible to stress cracking at high crystallinity; this constraint is different from LDPE, where solvent-based inks do not normally reduce film integrity.

Migration and food-contact testing are executed on the finished structure, not on the pellet alone. The F15C compound is typically supplied with documentation indicating that its monomers and additives are listed for specific food-contact uses under EU Regulation 10/2011 and relevant FDA food-contact provisions. However, the flexible additive package used to lower modulus and seal initiation can increase overall migration above the EU limit of 10 mg/dm² if the film is used above 60 °C or with fatty food simulants. Published data for this specific configuration is limited; converters must perform total migration testing under 10/2011 Annex III and specific migration testing for the additive package. Cold-fill and ambient distribution below 40 °C are the validated operating boundary for most documented applications. Hot-fill, retort, microwave, and ovenable packaging are outside the supported operational envelope.

Compostability Certification and End-of-Life Test Matrix

Industrial compostability of the unfilled, unpigmented grade is certified under EN 13432:2000 and ASTM D6400-21. Biodegradation exceeds 90 % within 180 days under controlled composting conditions according to ISO 14855-1:2012; disintegration is complete within 12 weeks. Heavy metals and fluorine are below the limits of EN 13432:2000, Annex E. These certifications apply only to the polymer at the specified maximum thickness; printed, laminated, metallized, or coated structures require revalidation by the converter. Home compostability and marine biodegradability are not claimed. When the film enters an industrial composting facility, it should be handled as a high-surface-area material and can degrade faster than rigid PLA thermoforms; moisture and temperature in the first 4 weeks of composting influence fragmentation rate more than film thickness alone.

The table below summarizes the principal specification methods and representative values. These values are typical data from supplier technical documents and production-scale film evaluations; they are not to be interpreted as sales specifications.

The Grade Occupies a Narrow Position Between Rigid PLA and Low-Density Polyethylene

Substitution of LDPE with F15C is not a drop-in replacement. The melt has lower melt strength than LDPE, limiting maximum draw ratio and line speed. Cast film trials on a 30:1 L/D single-screw extruder with a 1200 mm die achieve stable webs at 60–120 m/min, whereas LDPE on the same equipment can exceed 150 m/min. The heat-seal initiation temperature of 85 °C is lower than many LDPE grades, but the F15C plateaus only to 130 °C, requiring tighter jaw-temperature control. Moisture vapour transmission rate for a 50 µm film measured by ISO 15106-1 at 38 °C and 90 % RH is typically above 100 g/m²/day, while LDPE at the same thickness is approximately 3–5 g/m²/day. This restricts the use of F15C in high-moisture barrier applications unless a barrier layer or coating is added.

In comparison with standard PLA film, F15C demonstrates a lower tensile modulus and higher elongation, which reduces film crinkle and improves puncture resistance in flexible packaging. Standard PLA film often exhibits tensile modulus above 3.0 GPa and elongation below 10 %; F15C reduces stiffness to 1.8–2.2 GPa and increases elongation to 150–180 %. This property shift is achieved at the cost of oxygen and moisture barrier; PLA-based films already have moderate humidity-dependent barrier properties, and the flexible modifiers increase segmental mobility, which raises permeability relative to rigid PLA. Converters requiring oxygen transmission below 500 cm³/m²/day·atm at 23 °C and 50 % RH should verify the final structure because published data for this specific configuration is limited.

Slitting and winding parameters influence final roll quality. After extrusion, the film reaches dimensional stability after 24–48 h aging at 23 °C and 50 % relative humidity. Immediate slitting can produce 1–2 % width loss because of relaxation. Turret winders are operated with taper tension from 10–15 N/m at the core to 5–8 N/m at the outer roll. Storage above 30 °C increases blocking tendency and should be limited to 6 months in unopened original packaging. Rolls are shipped with moisture-barrier packaging because PLA film reabsorbs atmospheric moisture and can shift seal initiation if stored at high humidity.

Corona treatment raises surface energy to 38–42 mN/m for water-based inks and laminations. Because the treatment decays over time, lamination or printing should be performed within 24 h of treatment or inline after extrusion. Untreated film surface energy is typically 30–34 mN/m. Shellac-based cold-seal adhesives and natural rubber latex are generally incompatible with PLA films; solvent-based polyurethane laminating adhesives require migration testing before final use.