Compostable 1000 is an injection-molding-grade compound based on polylactic acid modified with a compostable aliphatic-aromatic copolyester and a mineral nucleating package. The product is supplied as cylindrical pellets with diameter 3.0 mm ± 0.3 mm, bulk density 720 kg/m³, and melt flow rate 15 g/10 min at 190 °C under 2.16 kg in accordance with ISO 1133-1:2022. Intended uses include rigid single-use food-service articles, cosmetic closure components, and short-life durable goods where industrial composting infrastructure is available. The grade differs from standard PLA by incorporating a secondary biodegradable polyester that raises notched impact resistance while retaining tensile stiffness above 3,000 MPa. Published data for this specific blend configuration are available from supplier technical bulletins rather than peer-reviewed literature; the values below are representative of injection-molded specimens conditioned at 23 °C and 50% relative humidity.

What Limits the Processing Window for Compostable 1000?

Moisture control is the first boundary. PLA-based blends undergo hydrolytic chain scission when pellet moisture exceeds 250 ppm; desiccant drying at 80 °C for 4 h to a dew point of -40 °C is required before melt processing. At barrel temperatures above 210 °C, molecular weight reduction is measurable as a decrease in pressure-corrected melt viscosity; at temperatures below 185 °C, the mineral nucleating package may not fully disperse and flow lines appear in thin-wall sections. Barrel profiles of 170/185/195/200 °C from feed throat to nozzle and mold temperatures of 25–35 °C produce amorphous parts with stable dimensions. Higher mold temperatures of 60–80 °C increase crystallinity and HDT-B but extend cycle time by 20–35% depending on wall thickness. Injection velocity should remain moderate; shear rates above 10,000 s⁻¹ in hot runner drops can induce viscous heating and localized molecular weight loss. Screw L/D ratio of 20:1–25:1 with low-compression geometry and non-return valve clearance below 0.05 mm is recommended. Residence time should not exceed 5 min at melt temperatures above 200 °C.

On 120-ton hydraulic injection machines with 32 mm general-purpose screws, gate blush and jetting occur when injection linear velocity exceeds 120 mm/s in cold runner systems; fill imbalance in 8-cavity hot-runner tools has been associated with melt temperature differences of 6–10 °C across manifold zones. These are process-specific failure thresholds, not material property limits, and require cavity-pressure transducers for reliable detection. If ambient relative humidity exceeds 60%, hopper residence time above 1 h is discouraged unless a closed-loop dryer receiver is used.

Comparative tensile, flexural, and impact data across three commercial compostable injection grades

The comparative values were obtained from injection-molded test specimens conditioned for 48 h at 23 °C and 50% relative humidity. Batch-to-batch variation in notched Izod impact across 5 production lots remained within ±0.4 kJ/m² when molding was performed on a 120-ton hydraulic press with 32 mm screw diameter. The data position Compostable 1000 between brittle unfilled PLA and flexible PBAT-rich compounds: flexural modulus is 11% lower than unfilled PLA, elongation at break is 3 times higher, and notched Izod impact is 67% higher. The modulus remains above 3,000 MPa for rigid thin-wall packaging sidewalls, while the impact improvement reduces handle breakage in cutlery and snap-fit closure failures.

Thermal transitions measured by differential scanning calorimetry at 10 °C/min show a glass transition at 58 °C, a cold-crystallization exotherm between 95 °C and 110 °C, and a melting endotherm between 150 °C and 165 °C. The crystallization half-time at 100 °C is 2.5 min, which is slower than nucleated PLA grades optimized for heated molds. Capillary rheometry at 190 °C gives a shear viscosity of 1,100 Pa·s at 100 s⁻¹ and 320 Pa·s at 1,000 s⁻¹; the calculated power-law index between 100 s⁻¹ and 1,000 s⁻¹ is 0.46. Thermogravimetric analysis under nitrogen shows 5% mass loss at 270 °C and onset decomposition near 300 °C, which bounds hot-runner and barrel setpoints.

Rigid cutlery and thin-wall containers molded from Compostable 1000 have been evaluated on 180-ton electric injection cells with 8+8 stack molds and cycle times of 9–12 s for wall thickness between 1.2 mm and 2.0 mm. In cutlery production, gate freeze must occur before hold pressure release; premature hold release has produced sink marks at the fork tine base because the crystallized skin constrains volumetric shrinkage compensation. In container lids, venting depths below 0.02 mm prevent flash while allowing air evacuation from zero-draft sidewalls. Mold shrinkage is anisotropic: parallel-to-flow shrinkage averages 0.4%, perpendicular-to-flow shrinkage averages 0.5% after 24 h at 23 °C. Post-mold crystallization can occur over 48 h in uncontrolled storage; dimensional inspection should be delayed to 48 h or parts should be annealed at 60 °C for 30 min to stabilize dimensions.

Unlike starch-filled PLA compounds, Compostable 1000 does not use granular starch as a filler. This avoids viscosity instability caused by starch decomposition above 180 °C and lowers water absorption in the molded part. Starch-filled grades may show lower density but also lower tensile strength and higher odor; the melt viscosity of Compostable 1000 is more stable over a 5 min hold-up at 200 °C. Compared with film-grade PBAT/PLA compounds, the melt flow rate of 15 g/10 min at 190 °C is deliberately lower than typical film extrusion values of 30–50 g/10 min to provide melt strength for large shot sizes. Compared with polypropylene impact copolymer, Compostable 1000 has lower notched Izod impact and lower heat deflection temperature; its selection is appropriate only when industrial composting or biobased carbon content is a binding requirement.

Industrial compostability is assessed against EN 13432:2000/AC:2005, ASTM D6400-21, and ISO 17088:2021 rather than a single material property. These standards require four parallel lines of evidence: chemical characterization, aerobic biodegradation, disintegration, and ecotoxicity.

Because the blend contains a synthetic aliphatic-aromatic copolyester, aerobic biodegradation in soil or home composting may proceed at a different rate than industrial composting conditions. The product is not certified for home compost use unless additional testing under ISO 20200:2023 laboratory-scale or ISO 16929:2021 pilot-scale conditions is completed for the final article. Do not use in long-term outdoor exposure without UV stabilization, and avoid continuous load above 50 °C; HDT-B is 55 °C at 0.45 MPa, which places the practical use ceiling below hot-fill and microwave conditions.

Avoid amine-based additives, including certain slip and antistatic concentrates, because they catalyze transesterification and chain scission in PLA; the resulting melt flow drift can exceed +4 g/10 min over a 10 min hold-up time at 200 °C. Acidic or alkaline color concentrates should be pre-tested for melt stability and compostability compliance. Drying of regrind from sprues and runners can proceed at 80 °C for 4 h, but recycled content should not exceed 20% to maintain notched Izod impact above 4.0 kJ/m² in thin-wall cutlery.