PLA vs PBAT Biodegradable Material: Compostability EN 13432, Mechanical Properties Comparison

Overview #

When sourcing PLA or PBAT from Chinese compounders, the specification parameter that procurement teams most consistently get wrong is not melt flow index — it’s the compostability certification status. A COA showing “biodegradable” or even citing EN 13432 does not mean the material has been third-party certified. It means the supplier has typed those words onto a document. In our qualification program, we treat uncertified compostability claims as a disqualifying red flag, not a minor documentation gap. The mechanical and degradation performance gap between a genuinely certified PLA/PBAT blend and an uncertified one can be the difference between a product that passes your customer’s compostability audit and one that fails it at the worst possible moment.

COA Parameters, Certification Verification, and What to Actually Request #

The first thing to understand about PLA and PBAT sourced from China is that both materials are produced domestically at scale — PLA primarily by NatureWorks licensees and domestic producers like Hisun Biomaterials, PBAT by BASF-licensed and independent compounders — but the documentation quality varies enormously between them. A COA from a tier-1 Chinese PBAT producer will look very different from one issued by a small compounder blending recycled or off-spec resin.

Minimum COA field requirements for PLA:

• Melt Flow Index (MFI): test method, temperature, load (typically 190°C / 2.16 kg per ISO 1133)
• Molecular weight (Mn and Mw) or inherent viscosity
• D-lactide content (%) — critical for crystallinity and degradation rate
• Residual monomer content (lactide, %) — must be ≤0.3% for food-contact applications
• Moisture content (%) — must be ≤0.025% before processing
• Ash content (%)
• Color (L, a, b* or visual)
• Lot/batch number with traceability to raw material lot
• Third-party compostability certification number (if claimed)

Minimum COA field requirements for PBAT:

• MFI: 190°C / 2.16 kg per ISO 1133
• Tensile strength at break (MPa) and elongation at break (%)
• Melting point (°C) by DSC
• Density (g/cm³)
• Moisture content (%) — must be ≤0.05% before processing
• Heavy metals content (if food-contact or compostability certification required)
• Lot/batch number
• Third-party compostability certification number (if claimed)

Most procurement teams request MFI and tensile strength and consider the COA complete. The parameter that actually determines whether a PLA/PBAT blend will pass EN 13432 disintegration testing is D-lactide content in the PLA fraction and the molecular weight distribution — neither of which appears on the majority of Chinese supplier COAs unless you specifically demand it.

Compostability certification: what to verify and how

EN 13432 (European standard for packaging recoverable through composting and biodegradation) and ASTM D6400 (US equivalent for compostable plastics) are the two benchmarks that matter for export markets. For China domestic market, GB/T 28018 covers biodegradable plastics for packaging, but its requirements are not equivalent to EN 13432 — the disintegration threshold and ecotoxicity testing protocols differ.

The critical verification step: request the actual certification body certificate, not just the certificate number. Legitimate EN 13432 certifications are issued by bodies including DIN CERTCO, TÜV Austria (OK Compost), and BPI (for ASTM D6400). Cross-reference the certificate number directly on the certifying body’s public database. We have seen Chinese suppliers present certificate numbers that either belong to a different product or have expired — a check that takes three minutes and eliminates a significant compliance risk.

One point that catches buyers: a blend certification is not transferable from the individual components. If a supplier holds EN 13432 certification for their PLA resin and separately for their PBAT resin, that does not mean their 70/30 blend is certified. The blend must be certified as a formulation. We have seen this misrepresented in supplier documentation more than once.

Incoming QC Test Methods and Pass/Fail Thresholds #

For incoming inspection of PLA and PBAT from Chinese suppliers, the minimum test battery we recommend covers four parameters: MFI, moisture content, tensile properties, and — for compostability-critical applications — D-lactide content (PLA) or molecular weight confirmation (PBAT).

MFI verification: Test per ISO 1133 at 190°C / 2.16 kg. Acceptable deviation from COA value: ±15% for standard grades, ±10% for film-grade materials. An MFI shift of more than 20% from the specified value typically indicates either moisture degradation during transit or a raw material substitution at the compounder. Both are disqualifying without explanation and re-test.

Moisture content: PLA is hygroscopic and will hydrolyze during melt processing if moisture exceeds 0.025% (250 ppm). Test by Karl Fischer titration or loss-on-drying at 80°C for 4 hours. PBAT is less sensitive but should be below 0.05% (500 ppm) before processing. Incoming material that has been improperly stored or shipped without desiccant packaging will frequently exceed these thresholds — we see this most often with sea freight shipments during summer months.

Tensile properties: Test per ISO 527 on compression-molded or injection-molded specimens. For PLA, reject if tensile strength at break falls below 40 MPa or elongation at break exceeds 10% (which would indicate plasticizer addition or blending with a soft phase not disclosed on the COA). For PBAT, elongation at break below 400% is a red flag for degraded or adulterated material.

D-lactide content (PLA only): This requires GC or NMR analysis and is not a standard incoming inspection test for most buyers — but it should be for any application where crystallinity, heat resistance, or degradation rate is specified. High D-lactide content (>4%) produces amorphous PLA with a heat deflection temperature below 55°C, which will fail in applications requiring dimensional stability above ambient temperature. Most Chinese PLA producers offer both L-PLA (D-content <1%) and standard grades (D-content 4–8%); the COA should specify which you are receiving.

In our qualification program, we require three consecutive batch COAs before recommending a Chinese supplier for volume commitment. The reason is not bureaucratic — it is because lot-to-lot MFI variation is the most common quality failure mode we observe in Chinese PLA and PBAT supply, and a single sample approval does not reveal it.

Adulteration red flags:

The most common adulteration scenario we encounter in Chinese PBAT supply is dilution with conventional LLDPE or LDPE. The economic incentive is straightforward — PBAT costs 2–3× more per kilogram than commodity polyethylene. Detection methods:

• DSC (Differential Scanning Calorimetry): LLDPE shows a melting peak at 120–130°C distinct from PBAT’s 110–120°C peak; a shoulder or secondary peak is diagnostic
• FTIR: PE shows characteristic C-H stretching peaks without the ester carbonyl peak at ~1715 cm⁻¹ that is present in PBAT
• Disintegration test per EN 13432: adulterated material will fail the 90% disintegration threshold at 12 weeks

For PLA, the most common adulteration is blending with recycled or off-spec PLA without disclosure. Indicators include elevated ash content (>0.5%), inconsistent color between lots, and MFI values outside the specified range. Residual lactide monomer above 0.5% suggests inadequate devolatilization during polymerization — a process control issue that correlates with other quality problems.

Storage, Handling, and Shelf Life Requirements #

PLA and PBAT have meaningfully different storage sensitivities, and Chinese suppliers do not always communicate these requirements adequately in their technical data sheets.

PLA storage: Maximum 25°C, relative humidity below 50%, away from direct sunlight. Shelf life from production date: 24 months in original sealed packaging. Once opened, material must be resealed with desiccant and used within 30 days, or re-dried before processing. PLA that has absorbed moisture above 0.025% will undergo hydrolytic degradation during melt processing, producing a significant molecular weight drop and corresponding loss of mechanical properties — this is irreversible. Re-drying at 80°C for 4–6 hours in a dehumidifying dryer (dew point ≤ -40°C) is required before processing if moisture content is uncertain.

PBAT storage: Less hygroscopic than PLA, but still requires dry storage below 30°C. Shelf life: 18 months in original packaging. PBAT is more sensitive to UV exposure than PLA — outdoor storage, even in opaque bags, accelerates surface oxidation and can affect elongation at break.

Packaging specification to request: Both materials should be supplied in moisture-barrier multilayer bags (minimum 3-layer PE/foil/PE or equivalent) with desiccant sachets, packed in corrugated cartons. Sea freight shipments should include silica gel in the outer carton. Suppliers who ship in single-layer PE bags without desiccant are signaling inadequate understanding of the material’s storage requirements — and that signal extends to their process controls.

Most Western buyers do not realize that Chinese warehouse and logistics infrastructure varies enormously by region and season. A supplier in Guangdong shipping during July–August humidity peaks presents a materially different moisture exposure risk than the same supplier shipping in January. Specifying packaging requirements in your purchase order, not just in your supplier qualification checklist, is the only way to enforce this consistently.

For food-contact or compostable packaging applications, also verify compliance with REACH (if exporting to EU) for residual monomers and additives, and confirm that any slip agents, anti-block additives, or nucleating agents used in the compound are also certified compostable and food-contact compliant. This is a detail that gets missed at the sourcing stage and surfaces during customer audits.

For related sealing and barrier material sourcing considerations, see our category on barrier films and specialty polymers.

Practical Guidance for Buyers #

When sourcing PLA or PBAT from China, the first specification to request is not MFI — it is the compostability certification document with the issuing body’s name, certificate number, and expiry date. Verify that number directly on the certifying body’s database before any other evaluation step. Most buyers skip this and discover the compliance gap after committing to volume.

The sourcing mistake with the most costly consequences is accepting a component-level certification (PLA certified, PBAT certified) as equivalent to a blend certification. It is not. EN 13432 certification must cover the specific formulation you are purchasing. A supplier who cannot produce a blend-level certificate for their PLA/PBAT compound is not certified for that product, regardless of what their individual resin certificates say.

Before committing to volume, require: (1) three consecutive batch COAs showing MFI within ±10% of specification, (2) incoming moisture content test results below 0.025% (PLA) or 0.05% (PBAT), and (3) a DSC trace confirming the absence of PE contamination peaks. For compostability-critical applications, require a disintegration test report per EN 13432 conducted by an accredited third-party laboratory — not an in-house test report from the supplier. The cost of this qualification step is negligible compared to the cost of a failed compostability audit on a finished product line.

Frequently Asked Questions #

Q1: What is the most important COA parameter to verify when sourcing PLA from China?
A: D-lactide content. It determines crystallinity, heat resistance, and degradation rate — and it is absent from most Chinese supplier COAs unless you specifically request it. An MFI value alone tells you almost nothing about whether the material will perform in your application.

Q2: How do I verify that a Chinese supplier’s EN 13432 compostability claim is legitimate?
A: Request the certificate document showing the issuing body (DIN CERTCO, TÜV Austria, or BPI for ASTM D6400), the certificate number, and the expiry date. Then cross-reference that number on the certifying body’s public database. Per EN 13432, the certification must cover the specific formulation — not just the individual resin components. This check takes three minutes and eliminates the most common compliance fraud we see in this category.

Q3: What is the most common adulteration scenario for PBAT sourced from China?
A: Dilution with LLDPE or LDPE. The economic incentive is real — PBAT costs significantly more per kilogram than commodity polyethylene. Run DSC on incoming material: a PE melting peak at 120–130°C distinct from PBAT’s expected 110–120°C peak is diagnostic. FTIR confirmation takes under 10 minutes and should be part of any incoming QC protocol for this material.

Q4: What certifications and test documentation should I require before a volume order of PLA/PBAT blend for compostable packaging?
A: Require a blend-level EN 13432 or ASTM D6400 certificate from an accredited third-party body, three consecutive batch COAs with MFI within ±10% of specification, and a DSC trace per lot. For EU export, also require REACH compliance documentation covering residual monomers and any additives in the compound.

Q5: Is Chinese-produced PLA technically equivalent to NatureWorks Ingeo grades?
A: Not always, and the gap matters most in high-D-lactide-content grades. Domestic Chinese PLA producers have improved significantly, but lot-to-lot molecular weight consistency remains the differentiator. Specify Mn, Mw, and PDI on your purchase order — not just MFI — if consistency across production runs is critical to your process.

Published by sinoraw.com Technical Team | Request a sourcing consultation