Bio-Flex FX 1803 Translucent Recyclable Blown Film PLA Blend is a thermoplastically processable compound in which a polylactide matrix is modified with a biodegradable copolyester to reduce film brittleness and stabilize the tubular film bubble. The designation does not imply post-consumer recycled-content incorporation; the term “Recyclable” refers to the potential for capture and reprocessing within a dedicated PLA film stream under controlled industrial recovery conditions. The compound is specified for monolayer blown film extrusion using a smooth-barrel single-screw extruder with an L/D ratio of 25:1 to 30:1, a barrier screw with a mixing element, and a die gap of 0.8 mm to 1.2 mm.

Under ISO 1133-1:2022 at 190 °C and 2.16 kg, the melt flow index of the grade is typically reported between 3 g/10 min and 6 g/10 min. Density measured according to ISO 1183-1:2019 falls between 1.26 g/cm³ and 1.30 g/cm³. The viscoelastic profile is tuned for high draw at the frost line; however, the material is hygroscopic, and residual moisture must be held below 250 ppm before extrusion to limit hydrolytic chain scission.

What Limits the Blown Film Processing Window for This Grade?

Blown film processing for this PLA blend is constrained by the interaction of melt temperature, moisture, shear history, and draw. A barrel profile moving from 150 °C in the feed zone to 175 °C at the adapter is standard, with die lips held between 155 °C and 170 °C. Melt temperatures above 190 °C cause random-chain scission and lactide reformation; the resulting drop in melt strength appears as bubble sag and poor frost-line stability. On a 35 mm single-screw extruder running a 25 µm film at 60 kg/h, die pressure is typically maintained between 120 bar and 200 bar. Pressure excursions beyond 230 bar indicate insufficient melt temperature or excessive screw speed, not a formulation defect.

Capillary rheometry at 170 °C indicates apparent shear viscosity of 800–1,400 Pa·s at 100 s⁻¹ and 2,500–4,500 Pa·s at 10 s⁻¹. The power-law index lies between 0.55 and 0.70, indicating pronounced shear thinning. Blow-up ratio is recommended between 2.0:1 and 3.5:1. At blow-up ratios below 1.5:1, transverse molecular orientation is low and transverse tear propagation increases. At blow-up ratios above 4.0:1, bubble instability and thickness variation above ±12 % are observed on a 300 mm die unless a dual-lip air ring and external bubble stabilizer are in operation. Frost line height should be maintained between 2 and 4 die diameters to balance crystallite formation and collapse blocking.

In fresh-cut produce packaging, the film is typically run at 20 µm to 30 µm thickness and exposed to condensation at distribution temperatures of 4 °C to 15 °C. The copolyester phase suppresses brittle crease fractures at fold lines that are a known failure mode for unmodified PLA films under refrigerated distribution. Corona treatment to 38–42 mN/m before flexographic printing is used to maintain surface energy above 36 mN/m for water-based ink adhesion. The grade is not recommended for reverse-printed lamination where ethyl-acetate-based solvent inks require an external primer.

Heat sealing can be performed on a constant-heat bar sealer; the seal initiation temperature is typically 80–95 °C measured by heat-seal tensile testing at 2 bar and 0.5 s dwell. Sealing below 70 °C produces weak bonds due to incomplete copolymer interdiffusion. Above 110 °C, seal strength becomes dependent on local chain orientation and may decline if the quenched amorphous layer is excessively crystallized.

Mechanical and Optical Property Ranges for 30 µm Monolayer Film

Values are typical ranges for laboratory-produced monolayer blown film; production lots must be verified on the target line because draw, cooling rate, and thickness alter orientation-dependent properties. Published data for specific film configurations below 15 µm is limited.

When Ambient Relative Humidity Exceeds 60 % During Storage or Handling

Polylactide undergoes hydrolytic degradation in the melt; the rate is accelerated by temperature and residual moisture. If bags are opened in an environment above 60 % relative humidity, granules should be transferred to a desiccant dryer within 15 min. Pre-drying at 60 °C for 4 h using a desiccant bed or molecular-sieve dryer with a dew point of −40 °C or lower reduces moisture below 250 ppm. Hopper residence should not exceed 4 h to avoid thermal annealing of the granulate.

A moisture increase from 200 ppm to 500 ppm at a melt temperature of 180 °C reduces intrinsic viscosity and produces bubble holes, gauge bands, and a sharp decrease in die pressure. The hydrolysis reaction follows pseudo-first-order kinetics in the melt and can reduce molecular weight by 10–20 % within 2 min of residence time; the exact degradation rate depends on catalyst residues and copolyester hydrolysis stability. Regrind containing moisture above 300 ppm should be re-dried even when added at 20 wt% or less, because wet regrind creates gel-like defects and increases melt fracture at the die lips.

Industrial compostability is evaluated according to EN 13432:2000 and ASTM D6400-21. The material is intended to disintegrate in an industrial composting environment at 58 ± 2 °C and ≥ 50 % moisture. Ultimate aerobic biodegradation is measured by ISO 14855-1:2012 at 60 °C; disintegration is measured by ISO 20200:2004, with a requirement of not more than 10 % of original dry mass retained on a 2 mm sieve after 12 weeks. The grade is not certified for home compost, marine biodegradation, or anaerobic digestion; ambient soil burial does not provide the required thermal and moisture conditions.

In food-contact applications, compliance must be confirmed on the final printed and adhesive-laminated film because multilayer structures introduce non-PLA layers. The base compound may support compliance with Regulation (EU) No 10/2011 only after migration testing under EN 1186 and verification of the overall migration limit of 10 mg/dm². REACH registration and RoHS restrictions apply to the finished article; the compound contains no intentionally added phthalates or heavy metals above RoHS thresholds.

Tear Resistance and Seal Initiation Are Governed by the Copolyester Phase

Dynamic mechanical analysis of the blown film typically shows a PLA glass transition between 50 °C and 60 °C and a secondary loss modulus peak associated with the copolyester at subzero temperatures. The secondary damping contributes to impact toughness in cold-chain distribution and reduces the splintering fracture mode of unmodified PLA. Seal initiation is controlled by copolymer interdiffusion; a constant-heat bar sealer at 2 bar and 0.5 s dwell yields measurable seal strength above 80 °C, with failure converting from interfacial peel to film tear above 95 °C.

The amorphous domains near the seal can crystallize if the seal bar remains closed longer than 2 s above 110 °C; this reduces tear initiation resistance adjacent to the seal. On a three-layer blown film line with 70 mm extruders and a 400 mm die, edge trim regrind at 20 wt% does not increase gel count when regrind particle size is below 2 mm and moisture is re-dried below 200 ppm.

How Does This Grade Differ from Homopolymer PLA and PBAT-Rich Blown Films?

Unmodified homopolymer PLA film typically exhibits tensile elongation at break below 10 %, high bending stiffness, and pronounced bubble instability at blow-up ratios above 2.0:1. Bio-Flex FX 1803 is formulated to shift elongation into the 150–400 % range while retaining a PLA-dominant continuous phase. This preserves stiffness and translucency that PBAT-rich blown films lose through lower modulus and higher film thickness requirements. The PLA-dominant matrix also permits end-of-life sorting by near-infrared polymer identification, whereas PBAT-rich films may interfere with PLA reclamation streams.

Relative to mineral-opacified PLA compounds, Bio-Flex FX 1803 avoids high filler loadings and therefore retains total luminous transmittance between 85 % and 92 %. The trade-off is lower dimensional stability at temperatures above 50 °C; the grade is not a drop-in replacement for PET or oriented polypropylene in hot-fill applications. The film should not be used above 60 °C continuous service without heat-setting, because the PLA phase begins to soften near its glass transition and may show shrinkage above 70 °C.