Compostable 3020 blown-film PLA blend is assessed in six downstream converting environments where industrial compostability, home compostability, soil biodegradation, or food-contact status determines formulation limits. Addition ratios are expressed as weight percentage of total hopper blend unless otherwise stated. Extrusion references assume smooth-bore single-screw blown-film lines with 24:1 to 30:1 L/D, barrier screws with Maddock mixing sections, and internal bubble cooling. Published data for proprietary masterbatch carriers in this specific compound are limited; where certification depends on masterbatch identity, the restriction is stated inline.

What Four-Parameter Certification Means for Grocery T-Shirt Bags

Retail checkout film in the 15–30 µm thickness band converts from Compostable 3020 as a 100 % ready-to-use compound; regrind from edge trim may be reintroduced at 10–20 wt% only after desiccant drying to a moisture content below 250 ppm, because PLA hydrolysis at the die lowers melt strength and produces pinhole defects. The industry reference for organic recovery is EN 13432:2000 clause 4.2.1 through 4.2.3, requiring aerobic biodegradation, disintegration, and ecotoxicity testing; the same four-parameter logic appears in ASTM D6400-19 and ISO 17088:2021. Certification marks in this segment are TÜV Austria OK Compost INDUSTRIAL, DIN CERTCO, and BPI; Australian converters reference AS 4736-2006. Additive loading is constrained: slip masterbatch at 1.0–2.0 wt% and antiblock at 0.5–1.5 wt%; pigment masterbatch should remain below 5 wt% and its carrier must carry the same compostability certificate, otherwise the finished article cannot claim compliance. On the converting line, a die gap of 0.8–1.0 mm, a blow-up ratio of 2.5:1–3.5:1, and a melt temperature of 165–180 °C are typical; internal bubble cooling keeps the frost line stable at 2–3 die diameters. Terminal products include printed T-shirt bags, produce roll bags, and lightweight carrier bags with bottom gusset seals, produced at 80–120 kg/h per die meter on high-output lines; water-based inks are preferred because solvent-borne inks contaminate the regrind stream and disrupt industrial compost certification.

Melt Strength and Puncture Thresholds in Industrial Biowaste Liners

In industrial biowaste collection, wall thicknesses of 20–35 µm are required because curbside bins contain garden waste with woody fragments that puncture film made below 20 µm. The compliance framework remains EN 13432:2000 for industrial composting, with disintegration measured by ISO 16929:2021 and ecotoxicity by OECD 208; several municipal tenders also require separate proof of heavy-metal limits under EN 13432:2000 Annex B. Formulations for this scenario commonly blend 85–100 wt% Compostable 3020 with 0–15 wt% certified compostable PBAT to raise dart-impact and Elmendorf tear; the PBAT fraction should not exceed 15 wt% because higher levels reduce film modulus and create uncontrolled gauge variation on single-lip air rings. Slip masterbatch is held at 1.0–2.0 wt%; no talc-based antiblock is added unless the particle-size distribution is below 10 µm and the masterbatch carrier is certified. The extrusion process operates at a lower melt temperature of 160–175 °C to avoid thermal degradation of the PBAT domain, with a wider die gap of 1.0–1.2 mm and a blow-up ratio of 3.0:1; frost line height is kept at 2–3 die diameters to prevent MD orientation from reducing Elmendorf tear. At 15 wt% PBAT addition, dart impact per ASTM D1709-22A is often specified above 200 g for 25 µm film in municipal tenders, but published data for this specific compound are limited and converter trials must verify the PBAT level required to meet the target specification. Terminal products include 10–120 L biowaste liners for curbside organic waste, commercial kitchen caddy liners, and industrial food-waste totes.

Household kitchen caddy liners differ from municipal biowaste liners because home composting certification imposes a lower temperature benchmark than industrial composting and therefore narrows the window for both disintegration and aerobic biodegradation. Compostable 3020 film for this scenario is typically converted at 10–20 µm; the governing certification is TÜV Austria OK compost HOME and, where required, NF T51-800:2015 or AS 5810-2010, because no harmonized EN home-composting standard currently exists for this film category. The formulation is kept close to 100 % neat compound; processing-aid masterbatch may be used at 0.5–1.0 wt%, but only after the masterbatch carrier has been verified against the home-compost certification, since lower microbial activity at 20–30 °C increases the risk of incomplete mineralization. Pre-drying at 80 °C for 6 h to below 200 ppm is mandatory before extrusion; melt temperature is held at 155–170 °C to limit lactide formation at the die lip, and a die gap of 0.8 mm with a blow-up ratio of 2.5:1 produces the required thin film without excessive bubble sag. Processors use winder tension of 25–35 N/m because higher tension on 12 µm film increases permanent blocking and creates roll telescoping. Terminal products are 7–15 L kitchen caddy liners, small home-compostable produce bags, and food-scrap collection bags for residential composting programs; these articles are not automatically industrial compostable unless the same lot also meets EN 13432:2000.

When Soil Contact Exceeds 180 Days in Polyethylene-Free Mulch Film

Where soil contact exceeds 180 days, agricultural mulch film enters an environment in which the relevant degradation standard is not industrial composting but EN 17033:2018, which sets requirements for biodegradable mulch films for agriculture and horticulture; biodegradation in soil is assessed by ISO 17556:2019 because the film must mineralize in biologically active soil at ambient temperature over a period that may extend to 24 months. The compound is processed at 100 % neat resin or with 2–4 wt% soil-contact-compatible pigment masterbatch; carbon black masterbatch is acceptable only if the heavy-metal content meets EN 17033:2018 and the carrier is proven soil-biodegradable. Film thickness is 12–25 µm, with the lower limit used for short-season crops and the upper limit for overwintering layouts where wind uplift and hoeing machinery create puncture loads. On the blown-film line, a die gap of 1.0–1.2 mm and a blow-up ratio of 3.0:1–4.0:1 improve MD/TD tear balance; melt temperature is kept at 165–180 °C, and the bubble is stabilized with internal bubble cooling to 2–3 die diameters frost line height. Laying equipment imposes a practical limit: film below 15 µm tears at the needle punch when tension exceeds 40–50 N/m or when laying speed exceeds 6 km/h, but published field data for this specific compound are limited and must be verified on the target ridge profile. Terminal products include biodegradable mulch strip for tomato, strawberry, pepper, and vine crops; after harvest, the film is incorporated into the soil by disc harrow or rotary hoe where local regulation permits. Degradation rate depends on soil temperature, moisture, and microbial biomass, not on steam-sterilization compost temperature.

At the e-commerce converting station, mailer film from Compostable 3020 is processed to 30–60 µm because automated sorting and courier handling require higher puncture resistance than grocery bag film. Clean edge-trim regrind is added at 0–15 wt%; regrind exceeding 15 wt% increases gel formation in the melt filter and causes visible specks in white film. The compostability reference is EN 13432:2000 and ASTM D6400-19, but the certification applies only to the film component; the double-sided adhesive tape and liner are separate articles and must be either removed or replaced with a certified compostable adhesive system, otherwise the final mailer cannot be marked as compostable. White masterbatch is added at 3–5 wt%; the carrier must be EN 13432:2000-certified, and TiO₂ content above 5 wt% should be avoided because it increases density and reduces elongation at break in the high-speed stretch sections of packaging lines. Downstream conversion runs with a die gap of 1.2 mm, a blow-up ratio of 2.0:1–2.5:1, and melt temperature of 165–180 °C; corona treatment at 36–40 dyn/cm is applied in-line for print adhesion, but over-treatment above 42 dyn/cm accelerates surface degradation and lowers heat-seal strength. Terminal products include e-commerce poly mailers, return shipping bags, and garment overbags; these films are not suitable for high-value liquid products because the compostable adhesive closure and PLA-rich film have lower puncture resistance than LLDPE mailers of the same gauge.

Seal Initiation Below 85°C Is the Limiting Variable in Dry-Food VFFS Film

Dry-food primary packaging imposes two separate regulatory tracks: food-contact compliance under EU 1935/2004 with migration testing per EU 10/2011, and organic recovery claims under EN 13432:2000. The PLA homopolymer component is covered in the United States by FDA FCN 000178, but the copolyester fraction and masterbatch carriers must each hold their own food-contact status; a converted film cannot rely on the resin status alone. Formulation uses 100 % food-contact-approved compound; slip agent is limited to 0.5–1.0 wt%, and post-consumer reclaim is excluded from the food-contact layer unless a specific EFSA or 21 CFR authorization applies. The process window is narrower than non-food compostable film because the seal layer must initiate at or below 85 °C on vertical form-fill-seal equipment running 80–100 packages/min; if seal initiation exceeds 90 °C, the dwell time shortens and seal strength drops below 15 N/25 mm per ASTM F88. Converters run a die gap of 0.8 mm, a melt temperature of 155–170 °C, and a blow-up ratio of 2.5:1, followed by corona treatment at 38–42 dyn/cm; film is wound at 25–35 N/m to avoid blocking. Terminal products include bread bags, sugar and dry pulse pouches, tea outer bags, and produce bags for low-moisture goods. The material is not suitable for high water activity products or long-shelf-life oxygen-sensitive items because the PLA-rich film has a higher oxygen transmission rate than EVOH or PVDC barrier films.