Overview #
Compostable mailers made from PLA/PBAT blends sit at the intersection of functional transit packaging and sustainability compliance — and getting the specification wrong on either front creates real problems for brand partners. The most common brief we receive is a brand asking for a “compostable mailer” without specifying the composting pathway (industrial vs. home), the required certification mark for their target market, or the film thickness needed for their product weight range. This guide covers the material parameters we specify on our production line, the EN 13432 and related certification requirements that govern market access in the EU, US and Australia, and the AQL inspection framework we apply before any shipment leaves our facility. If you are sourcing compostable mailers for an e-commerce or subscription box programme, this is the specification baseline we work from.
PLA/PBAT Film Composition and Mechanical Performance Parameters #
The functional performance of a compostable mailer depends heavily on the PLA-to-PBAT ratio in the blown film compound. PLA contributes stiffness and printability; PBAT contributes elongation and tear resistance. On our production line, we typically run a 55–60% PLA / 40–45% PBAT blend by weight for standard e-commerce mailers. Below 40% PBAT, the film becomes brittle at low ambient temperatures — a real failure mode for mailers shipped through cold-chain logistics corridors in Northern Europe or Canada in winter.
Our standard film thickness for compostable mailers is 50–80 microns depending on the load category:
| Load Category | Film Thickness | Tensile Strength (MD) | Elongation at Break | Recommended Max Fill Weight |
|---|---|---|---|---|
| Light (apparel, accessories) | 50–55 µm | ≥ 28 MPa | ≥ 300% | Up to 500g |
| Medium (books, small electronics) | 60–65 µm | ≥ 32 MPa | ≥ 280% | 500g–1.5kg |
| Heavy (footwear, bundled goods) | 75–80 µm | ≥ 36 MPa | ≥ 250% | 1.5kg–3kg |
Tensile and elongation values are measured per ASTM D882 (Standard Test Method for Tensile Properties of Thin Plastic Sheeting). We test every production lot — not just the raw material certificate — because blown film properties vary with line speed and die temperature. Our internal acceptance threshold for tensile strength in the machine direction is ≥ 28 MPa at 50 µm; any lot falling below this is quarantined and re-tested before release.
Seal integrity is the other critical mechanical parameter. Our heat-seal seam on the self-adhesive closure strip must withstand a peel force of ≥ 8 N/25mm, tested per ASTM F88. We also specify a minimum dart drop impact resistance of 80g at 50 µm per ASTM D1709, which correlates well with real-world puncture resistance during automated fulfilment handling.
EN 13432 Certification and Compostability Compliance Requirements #
EN 13432 is the European standard for packaging recoverable through composting and biodegradation. It defines four test criteria: biodegradation (≥ 90% conversion to CO₂ within 180 days), disintegration (≥ 90% of material passes through a 2mm sieve after 12 weeks), ecotoxicity (no adverse effect on plant growth), and absence of hazardous substances. Our PLA/PBAT film compound is certified to EN 13432 through TÜV Austria, which also issues the OK compost INDUSTRIAL and OK compost HOME marks — the two most recognised certification marks in the EU and Australian markets.
For brand partners selling into the US market, the relevant standard is ASTM D6400 (Standard Specification for Labeling of Plastics Designed to be Aerobically Composted in Municipal or Industrial Facilities). The certification body most accepted by US retailers and composting facilities is BPI (Biodegradable Products Institute). We can supply film certified to both EN 13432 and ASTM D6400 simultaneously — the test protocols overlap significantly, and our compound supplier holds dual certification.
For the Australian market, the AS 4736 standard applies for industrial compostability, and AS 5810 for home compostability. Both are aligned closely with EN 13432 but require separate certification documentation. We provide the relevant certificate of conformity with each shipment.
One point we always clarify with brand partners: industrial compostable ≠ home compostable. Industrial composting requires sustained temperatures of 55–60°C over several weeks. Home composting operates at ambient temperatures, typically 20–30°C, and requires a more demanding biodegradation profile from the material. Our standard PLA/PBAT mailer is certified for industrial composting. Home-compostable certification requires a modified compound with a higher PBAT ratio (typically ≥ 55%) and a longer certification timeline. If your brand’s end-consumer communication promises home compostability, brief us on that requirement at the outset — it affects both material cost and lead time.
Regarding chemical compliance: our PLA/PBAT compound is REACH compliant (no SVHC substances above 0.1% w/w per the ECHA candidate list) and meets RoHS requirements for any printed electronic product packaging. For food-adjacent applications, the compound is assessed against EU Regulation 10/2011 on plastic materials in contact with food, though we recommend confirming the specific food-contact use case with your regulatory team before specifying a compostable mailer for direct food contact.
AQL Inspection System and Defect Classification #
We apply a two-stage inspection protocol to all compostable mailer production: inline process monitoring and pre-shipment AQL sampling inspection.
Inline, our blown film extrusion lines run continuous thickness gauging with a ±3 µm tolerance band. Any roll deviating beyond this band triggers an automatic line stop and operator review. Print registration on our flexographic printing lines is held to ±0.3mm — above this threshold, colour breaks become visible at mailer edges and are classified as a major defect.
Pre-shipment inspection follows ISO 2859-1 (Sampling Procedures for Inspection by Attributes), using General Inspection Level II. Our standard AQL levels by defect class are:
| Defect Class | Examples | AQL Level |
|---|---|---|
| Critical | Seal failure, missing closure strip, contamination with non-compostable material | 0 (zero tolerance) |
| Major | Thickness below 47 µm (at 50 µm spec), print misregister > 0.3mm, seal peel force < 8 N/25mm | AQL 1.0 |
| Minor | Surface scuff not affecting print legibility, minor colour density variation within ΔE < 3.0 | AQL 2.5 |
Colour density variation is assessed against an approved press proof using a spectrophotometer, with a tolerance of ΔE ≤ 2.0 for brand colours and ΔE ≤ 3.0 for background fills, measured per ISO 13655 (Spectral measurement and colorimetric computation for graphic arts).
Every production batch is accompanied by a Certificate of Conformance (CoC) documenting lot number, film thickness measurement results, seal strength test data, and the applicable compostability certification reference number. For brand partners requiring third-party verification, we can arrange pre-shipment inspection by SGS or Bureau Veritas at the brand’s cost.
Specification Notes for Brand Partners #
When you brief us on a compostable mailer project, the first things we need are: your target market (EU, US, Australia — this determines which certification mark is required), your product weight range and dimensions (this drives film thickness selection), and whether your brand communication will claim industrial or home compostability. A common mistake we see is brands specifying “EN 13432 certified” without confirming whether their local waste infrastructure actually supports industrial composting — if your end consumers are in regions without industrial composting access, the certification claim may be misleading under local green claims regulations, including the EU’s incoming Green Claims Directive.
Our typical process: digital proof of print artwork in 3–5 working days, physical pre-production sample in 10–15 working days, production lead time 20–25 working days after sample approval. We supply with each order: EN 13432 / ASTM D6400 certificate of conformity, REACH compliance declaration, material safety data sheet, and AQL inspection report. If your retailer or platform requires additional documentation (e.g. BPI certification letter, SGS test report), advise us at brief stage so we can factor this into the timeline.
Frequently Asked Questions #
Q1: What film thickness do you recommend for mailers carrying products up to 1kg?
A: For products up to 1kg, we specify 60–65 µm PLA/PBAT film, which delivers a tensile strength of ≥ 32 MPa in the machine direction and elongation at break of ≥ 280%, tested per ASTM D882. This thickness provides adequate puncture resistance for standard automated fulfilment handling without over-specifying material cost.
Q2: What is your MOQ and lead time for compostable mailers?
A: Our standard MOQ for compostable mailers is 5,000 units per size per design. Production lead time is 20–25 working days after sample approval, with physical pre-production samples available in 10–15 working days. Rush production at reduced lead time is possible for repeat orders on approved specifications.
Q3: Which certification marks can you supply for the EU and Australian markets?
A: We supply film certified to EN 13432 with TÜV Austria’s OK compost INDUSTRIAL mark for the EU, and we can provide documentation aligned with AS 4736 for the Australian market. For home compostability claims, we use a modified PBAT-dominant compound certified to OK compost HOME and AS 5810 — brief us on this requirement at the outset as it affects material lead time.
Q4: Can you print brand colours on compostable mailers and how many colours are supported?
A: Yes — we print compostable mailers on our flexographic lines with up to 8 colour stations. Print registration is held to ±0.3mm, and brand colour accuracy is verified against approved press proofs using a spectrophotometer with a ΔE ≤ 2.0 tolerance for brand colours per ISO 13655. Water-based inks are standard on compostable substrates to maintain the overall compostability profile of the finished mailer.
Q5: What happens if a production lot fails the seal strength test?
A: Any lot where seal peel force falls below 8 N/25mm (our Major defect threshold per ASTM F88) is quarantined immediately and not released for shipment. We re-test the sealing parameters — temperature, dwell time and pressure — and run a corrective production batch. Under our AQL 1.0 Major defect protocol per ISO 2859-1, a single seal failure in the sample triggers full lot hold and root cause investigation before any units are released.
Planning a compostable mailer programme for your brand? Contact our team to request a complimentary specification review and sample quote.
The cold-chain brittleness point is real — we had a run of 50 µm mailers delaminating at the self-seal strip during a January dispatch out of our 3PL in Doncaster, traced back to a batch that had drifted to 38% PBAT. Took three weeks and a full reformulation sign-off before we’d accept stock again.
The cold-chain brittleness point is real — we had a run of 55µm mailers from a Ningbo supplier last January where the PBAT content came back at 37% on third-party lab verification, and we were seeing seal failures on shipments routed through our Rotterdam 3PL during an unusually cold spell. Took two reformulation rounds and about six weeks to get the blend back to spec before we’d sign off on the next PO.
The PLA-to-PBAT ratio point about printability tradeoffs is something we ran into the hard way — we’d pushed our Shenzhen supplier toward a 62% PLA blend to get better flexo registration on our kraft-look surface print, and by Q3 we were seeing stress-whitening at the fold lines before the mailers even reached fulfilment. Took us two reformulation rounds to land on 58/42 and requalify the print profile.
The industrial vs. home composting distinction is worth expanding on for anyone sourcing into the Australian market specifically — AS 5810 (home compostable) and AS 4736 (industrial) have different disintegration timescales, and some Australian councils have explicitly excluded certified compostable packaging from their FOGO streams regardless of certification mark. We had a brand partner in Q3 last year who’d spec’d AS 4736-certified mailers assuming council acceptance, and it caused a real consumer communication problem when their customers tried to dispose of them correctly.
Switching from a 55% to a 60% PLA blend mid-year to hit EN 13432 certification thresholds cost us roughly $0.09/unit in material uplift at our 30k monthly volume — that’s about $32k annualised before you factor in the retooling time on the blown film line, which ran us an extra two weeks of qualification samples with our Guangzhou converter.
Had a structural failure on a 75µm heavy-spec run for a bundled footwear client — 3,200 units dispatched through a Calgary 3PL in February, and by the time they reached end retailers we had roughly 18% of mailers with longitudinal splits running from the bottom seal toward the center. The film spec on paper was fine, tensile looked right, but the PBAT had been blended toward the lower end of tolerance and the combination of -14°C overnight temps in the warehouse plus the compressive stacking load just tore straight through. Whole rerun was on us.
On the blow film composition side, curious whether you’ve seen any meaningful difference in haze or surface energy between the 55% and 60% PLA end of that blend range — we’re evaluating corona treatment settings for flexo on a 58% PLA trial run and the Dyne level we’re hitting post-treatment is dropping off faster than expected within the 72-hour adhesion window.
The self-seal strip placement relative to the perf line is something that bit us badly on a 60µm medium-spec run — we’d spec’d the lip at 18mm but the actual closure zone was landing 3–4mm short due to film creep through our heat tunnel, which meant anything over 800g was popping the seal under transit compression before it even hit our 3PL in Northampton. Took us about 400 failed units across two SKUs to trace it back to elongation variance at the high end of that ≥280% spec rather than a seal temperature issue.
Worth flagging for anyone running AQL on these: we specify critical defects (pinholes, seal failures) at AQL 1.0 but bump minor cosmetic defects up to 2.5, and collapsing those two into a single AQL level was how we passed a 40,000-unit run for a French skincare client only to pull back 600 units post-dispatch with visible gusset fold contamination that should’ve been caught at goods-in.