Compostable 7003A is introduced to sheet extrusion lines as a pre-conditioned PLA-based compound for rigid food-service and packaging sheet. Before start-up, the pellet is dried in a desiccant dryer at 70°C to 80°C with a dew point no higher than -40°C; target equilibrium moisture is below 250 ppm because the PLA continuous phase is sensitive to hydrolytic chain scission in the metering zone. If warehouse relative humidity exceeds 60%, open pellet storage should be limited to 30 min and hopper loading should proceed under a dry-air purge. Melt-flow-rate stability is checked under ISO 1133-1:2022 at 190°C/2.16 kg. The extrusion line is specified with a single-screw machine having an L/D ratio of 30:1 to 36:1, a barrier screw with a compression ratio between 2.8:1 and 3.2:1, and a gravimetric feeder. Barrel temperatures are set within 160°C to 190°C, with the die zone held 5°C to 10°C below the metering zone to preserve melt strength; exact setpoints are validated with melt-pressure and melt-temperature probes. Melt pressure at the gear-pump inlet is held between 80 bar and 120 bar. A 60/80/100 mesh screen pack protects the coat-hanger die, and the die gap is set between 0.6 mm and 1.0 mm. The sheet is polished on a three-roll stack with first, second, and third roll temperatures of 25°C, 30°C, and 20°C, respectively; first nip pressure is loaded to 18 N/mm to 25 N/mm. Edge trim is returned to the extruder at a maximum regrind fraction of 20 wt%; higher regrind fractions raise gel-fleck counts and reduce sheet tear resistance. Thermoforming is run at sheet surface temperatures of 85°C to 105°C. Heated syntactic foam plug assist is required when the draw ratio exceeds 1.5:1; below that threshold, cavity-only forming is limited to shallow trays and lids. Finished articles include cold-fill deli containers, clamshell lids, produce punnets, and portion cups. The material is not rated for hot-fill, microwave, or dual-ovenable applications. Continuous-use temperature is validated under ISO 75-2:2013 method B at 0.45 MPa; typical PLA-based sheet can deflect under this load once the part reaches 45°C to 55°C. Compostability verification follows EN 13432:2000 or ASTM D6400-23; industrial composting conditions of 58°C with active aeration are mandatory because PLA hydrolysis is sluggish under ambient soil conditions. Migration testing for cold-contact food use is conducted under EU 10/2011, and U.S. food-contact status must be confirmed through the food-contact notification or 21 CFR citation supplied in the grade-specific regulatory dossier.

Why Chill-Roll Neck-In Exceeds 15% in Thin Cast Film Without a Long-Chain Branching Package?

On chill-roll cast film lines, the 7003A grade is extruded through a flat die with a die gap of 0.5 mm to 0.8 mm and an air gap between 5 mm and 15 mm. The first chill roll is set at 15°C to 25°C, and the second roll at 10°C to 15°C; roll surface roughness is specified at Ra 0.02 µm to Ra 0.05 µm to reduce blocking. Melt temperature at the die lip is held between 155°C and 180°C; above 180°C, PLA thermal degradation increases gel formation, while below 155°C, die-lip drool and surface haze can appear. The film is corona-treated inline to a wetting tension of 38 mN/m to 42 mN/m, measured with ISO 8296:2003 test inks. Neck-in on unmodified PLA cast film is frequently above 15% at gauges below 20 µm; the melt-strength modification in 7003A is intended to reduce neck-in, but the actual value must be characterised in production trials because die width, air gap, and melt temperature interact. Extensional viscosity can be measured before scale-up with a Sentmanat extensional rheometer under ISO 20965-1:2019; if the supplier does not provide such data, start-up trials should include edge-pinning video records. Film gauges for compostable produce bags range from 12 µm to 25 µm, and for bin liners from 20 µm to 35 µm. Sealing is performed on rotary sealers at 95°C to 120°C and 0.3 MPa jaw pressure; serrated jaws are preferred over flat jaws because the PLA continuous phase can yield a brittle fusion line when overheated. Tear initiation is evaluated under ASTM D1922-23; if machine-direction tear strength is insufficient for the final bag format, the film should not be downgauged without a sharp-edge seal test. Water vapour transmission rate is substantially higher than LDPE or cast polypropylene at equivalent gauge when measured by ISO 15106-2:2014; the produce bag format is therefore restricted to short shelf-life, low-moisture produce or dry goods and should not be specified for wet or frozen product. Regulatory claims for compostable carrier bags or bin liners require certification under EN 13432:2000, ASTM D6400-23, or AS 4736-2006 as applicable; home-compostability claims require separate certification such as AS 5810-2010 or NF T 51-800:2015.

Extrusion coating of paper and board with Compostable 7003A uses a 30:1 to 34:1 L/D single-screw extruder with a barrier screw and a flat die fitted with adjustable inner deckles; melt temperature at the die is controlled between 180°C and 210°C. The paper substrate is preheated to 80°C to 100°C by infrared panels or flame treatment, and surface treatment is adjusted to achieve a minimum wetting tension of 38 mN/m before the melt curtain contacts the substrate. Coating weight is typically 15 g/m² to 25 g/m²; below 12 g/m², pinhole frequency increases because the PLA-rich melt has a narrower draw window than low-density polyethylene. The chill roll is held at 15°C to 20°C, and nip pressure is set between 20 N/mm and 40 N/mm; a matte-finish chill roll improves adhesion to fibre surfaces by increasing contact area. The coated board is converted into cold-service cups, food trays, and carton blanks requiring a compostable barrier layer. Edge curl is a known converting failure when PLA coating is applied to board below 200 g/m²; curl is controlled by balancing coat weight and substrate moisture content. In the European Union, the coated board falls under EU 10/2011 for plastic materials in food contact, with overall migration testing conducted under cold-contact conditions; the paper substrate must also comply with EC 1935/2004. In the U.S., components of paper and paperboard in contact with aqueous and fatty foods may be evaluated under 21 CFR 176.170, but the PLA component clearance must come from the supplier regulatory dossier. The structure is not intended for hot liquid service above 50°C because dimensional change and seal delamination can occur at the coated surface.

Soil-Contact Mulch Film and the Discrepancy Between Industrial Compostability and Ambient Soil Fragmentation

Cast film for agricultural mulch is produced at 10 µm to 25 µm, with standard lay-flat widths of 0.9 m to 1.6 m. The film is laid with tractor-mounted mulch layers at 5% to 10% field tension; excessive tension combined with the low ambient-temperature modulus of PLA can cause edge splits at planting holes. Carbon black or pigment masterbatch is added to suppress weed germination; pigment addition above 3 wt% can reduce tear initiation and should be validated under ASTM D1922-23. A central compliance issue is that EN 13432:2000 compostability is demonstrated at 58°C under humid industrial composting conditions, while ambient soil temperatures in temperate agriculture are typically 10°C to 30°C. PLA hydrolysis under those soil temperatures is substantially slower; ISO 17556:2019 soil biodegradation testing at 25°C will not produce the same time-to-fragmentation as the 12-week industrial compost disintegration window. Unless the blend contains a soil-biodegradable copolyester component and is certified under EN 17033:2018 for biodegradable mulch films, the film must not be described as soil-biodegradable. If such certification is claimed, the test report must include ecotoxicity testing on soil organisms and demonstration of fragmentation within the relevant crop cycle. Published data for this specific grade in soil-contact configurations is limited; field trials should monitor remaining film area, tensile strength retention under ISO 527-3:2018, and visible fragmentation at 8-week, 16-week, and 24-week intervals. Processing-side failure modes include blocking on the reel when low melt temperature and high winding tension exceed 0.5 N/mm² roll pressure; centre winders with taper tension control are preferred over surface winders for this application.

Transparent window patches for paperboard cartons are converted from 20 µm to 40 µm cast film of Compostable 7003A. The film is corona-treated to a wetting tension of at least 38 mN/m using ISO 8296:2003 test inks, then bonded to the carton blank with a water-based polyvinyl acetate adhesive or a solvent-free polyurethane adhesive; adhesive selection must avoid acidic components that accelerate PLA hydrolysis within the laminate. The windowing machine runs at 60 m/min to 120 m/min depending on blank size, with vacuum transfer and ionising-bar static neutralisation required because PLA film accumulates static charge at low humidity. Migratory antistatic additives are not preferred, since ester-based antistatic additives can alter surface adhesion and long-term compostability. Optical clarity is evaluated by ASTM D1003-21; the required haze value is grade-dependent and must be fixed in the film specification. Published data for this specific configuration is limited, so before die-cut tooling is finalised, tear propagation under ASTM D1922-23 and puncture propagation under ASTM D3420-21 should be characterised at the final film gauge. End products include bakery boxes, pasta cartons, cosmetics cartons, and greeting card windows. The window patch will pass package-level industrial compostability only if the adhesive and paperboard are also certified under EN 13432:2000 or ASTM D6400-23; the PLA film alone cannot carry the package-level certification. Moisture absorption under high-humidity storage above 60% RH can cause film dimension change and adhesive cleavage; laminated cartons should be stored below 40°C and 60% RH before filling.

When a 20 µm Cast Web Replaces LDPE as the Sealant Layer in a Compostable Two-Layer Flexible Laminate

Flexible packaging converters can use Compostable 7003A film as the sealant web in a two-layer laminate where the outer layer is a metallised cellulose film or a blown starch-based film. The laminate is produced either by adhesive lamination with a compostable adhesive or by thermal lamination on a heated-roll station. Seal initiation temperature for the cast PLA blend is normally reported at 85°C to 95°C, but the exact hot-tack curve must be measured under ASTM F1921-12 at seal dwell times of 0.2 s to 0.5 s to confirm operation on vertical form-fill-seal equipment. The sealant layer is supplied at 20 µm to 35 µm, and the laminate is used for dry snacks, tea overwrap, and small pouches where the total packaging structure is intended for industrial composting. Seal strength under ASTM F88/F88M-23 typically peaks when the seal bar temperature is 15°C to 25°C below the melting point of the continuous PLA phase; overheating causes shrinkage and edge curl at the seal. A key operational boundary is the low impact strength of PLA-rich film at refrigeration temperatures below 5°C; drop testing under ASTM D5276-19 should be performed on the filled pouch before specifying this laminate for chilled distribution. The barrier contribution is moderate: oxygen transmission rate is lower than polyolefin, but water vapour transmission rate is higher, so the laminate is not suitable for hygroscopic products requiring a moisture barrier. If the laminate is printed, the ink system must be certified compostable and the printed film surface must be treated to 38 mN/m to 42 mN/m before lamination. Industrial compostability of the finished laminate requires all components—film, adhesive, ink, and outer layer—to independently meet EN 13432:2000 or ASTM D6400-23. Published data for this specific configuration is limited; the converter must request the supplier test report for overall migration under EU 10/2011 and disintegration under ISO 16929:2021 for the exact laminate stack.