Product designation Sustainable 1013 is a low modulus injection moulding PLA blend formulated for disposable and semi-durable articles in which rigid unmodified polylactic acid grades exhibit premature hinge fracture, snap-fit cracking, or excessive ejection force. The compound comprises a polylactic acid base resin, a non-phthalate aliphatic polyester impact modifier, and a renewable processing aid. Representative lot data indicate a melt mass-flow rate of 8 g/10 min at 210°C under 2.16 kg load when tested to ISO 1133-1:2022, a solid density of 1.24 g/cm³ per ISO 1183-1, and a bio-based carbon fraction of 90% ± 5% per ASTM D6866. Tensile modulus is 1,450 MPa ± 150 MPa, tensile yield stress is 38 MPa ± 4 MPa, and nominal strain at break is 28% ± 8% when measured on ISO 527-2/1A specimens at 23°C and 50% RH. Notched Izod impact is 12 kJ/m² ± 3 kJ/m² at 23°C per ISO 180/A. Heat deflection temperature under 0.45 MPa is 52°C ± 3°C per ISO 75-2/B. The low modulus is achieved without plasticizer migration because the dispersed modifier phase has a number-average molecular weight above 20,000 g/mol and a glass transition temperature below -40°C. The grade is intended for tamper-evident closures, thin-wall packaging inserts, snap-fit housings, and living-hinge components moulded in cold-runner tools.

How Does Sustainable 1013 Differ from Unmodified PLA Injection Moulding Grades?

Unmodified general-purpose PLA injection grades typically exhibit tensile modulus values of 3,200 MPa to 3,500 MPa and nominal strain at break of 3% to 6% under ISO 527-2/1A conditions. Sustainable 1013 lowers tensile modulus by 55% to 60% and increases elongation at break by a factor of 5 to 8. The trade-off is a reduction in heat deflection temperature: nucleated unmodified PLA grades may reach 55°C to 85°C at 0.45 MPa, whereas Sustainable 1013 remains bounded at 52°C. Flexural modulus is 1,500 MPa ± 100 MPa per ISO 178, which reduces snap-fit insertion force but increases creep sensitivity under continuous load. Mould shrinkage is 0.3% to 0.5% parallel and 0.4% to 0.6% normal after 48 h at 23°C and 50% RH per ISO 294-4, approximately 0.1 to 0.2 percentage points lower than unmodified PLA under identical packing. Unlike PLA/PBAT blends, which often show haze above 30% at 2 mm thickness, Sustainable 1013 retains haze below 15% per ISO 14782. These differences are due to the dispersed low-modulus phase and reduced crystallinity induced by rapid cooling.

Before processing, pellet moisture must be reduced below 250 ppm, with a target of 150 ppm or lower. Desiccant drying at 80°C for 4 h using a dryer dew point of -40°C is the minimum condition; at ambient relative humidity above 60%, dried pellet residence time in the machine hopper should not exceed 30 min unless the hopper is purged with dry air at -40°C dew point. Drying hoppers with polymer bed depth above 50 mm require extended residence to 6 h due to limited air distribution. Moisture above 300 ppm produces hydrolysis during plastication. On a 25 mm reciprocating screw with L/D 24:1, hydrolysis is observed as a 15% to 25% reduction in melt viscosity measured by machine pressure drop at constant screw speed, coupled with cushion variability greater than ±1.5 mm, gate splay, and loss of notched Izod impact of 30% to 40% relative to dry material. Feed throat temperature should remain below 35°C; screw slip at the feed section occurs when pellets soften prematurely and is evidenced by screw recovery time fluctuations greater than 0.8 s across cycles. Under these conditions, the material should not be purged with polyolefins at temperatures above 220°C, because residual polyolefin contamination reduces interlayer adhesion and creates delamination at knit lines.

Melt Rheology and Screw Recovery Behaviour

The melt is shear-thinning and has a melt density of 1.08 g/cm³ at 200°C. On an injection moulding machine with a 40 mm three-zone screw, L/D 20:1, compression ratio 2.5:1, and a check-ring non-return valve with 0.02 mm to 0.05 mm clearance, screw recovery time at 120 rpm and 10 bar back pressure is typically 4 s to 6 s for a 120 g shot. Increasing back pressure to 20 bar raises melt temperature by 5°C to 8°C and reduces recovery time variability. Barrel temperature profiles should be set as follows: feed throat 30°C, rear 175°C, middle 190°C, front 200°C, nozzle 195°C. The melt temperature measured by a needle pyrometer should not exceed 210°C. Below 185°C, short shots occur in wall sections thinner than 1.0 mm. Above 215°C, melt residence time must be reduced to 2 min to avoid lactide formation and yellowing.

Injection speed has a direct effect on surface aesthetics and weld-line strength. In a 2 mm plaque mould with opposing gates, raising injection speed from 60 mm/s to 180 mm/s increases weld-line tensile strength from 22 MPa to 31 MPa per ISO 527-2/1A; speeds above 220 mm/s produce jetting and flow marks in hot-runner systems with gate diameters below 1.0 mm. Packing pressure should be 600 bar to 900 bar hydraulic, corresponding to 60% to 80% of peak injection pressure. Pack time for 1.5 mm wall stock is 3 s to 5 s; longer pack times do not reduce shrinkage further but extend cycle time. Screw and barrel combinations with mixing pins at the metering zone are acceptable, but high-shear barrier screws should be evaluated for melt-temperature overshoot above 210°C in cycles with recovery time longer than 8 s.

When Mould Temperature Falls Below 25°C or Melt Residence Time Exceeds 6 Minutes

Mould temperature is a critical threshold parameter for this grade. Below 25°C, weld-line strength measured on ISO 527-2/1A specimens with two opposing gates drops by 20% to 30% relative to a 30°C mould surface. Surface gloss also decreases and cold flow lines increase in thin-wall lids below 0.8 mm thickness. Above 35°C, cycle time becomes limited by surface tack during ejection; ejector pin marks deeper than 0.1 mm are observed in parts with demoulding draft angles below 0.5°. A mould temperature of 28°C to 32°C is recommended for living-hinge parts, while 20°C to 25°C is acceptable for simple flat parts with no knit lines. Mould cooling circuits should be balanced to maintain cavity-to-cavity variation within ±2°C; variation above ±4°C produces measurable differences in mould shrinkage of 0.05% to 0.10% across a 4-cavity tool.

Melt residence time above 6 min at 210°C creates a condition where MFR increases by 30% to 50% against the virgin pellet value, indicating chain scission by hydrolysis and thermal degradation. This condition is observed in production when hot-runner manifolds are oversized or when barrel capacity is more than 4 times shot weight. Degraded melt causes plate-out on mould vents, screw torque instability, and an increase in low-molecular-weight extractables. If the MFR of purged material exceeds 12 g/10 min, the barrel should be emptied immediately and the next production lot should be started with a melt temperature reduced by 5°C. The combination of high residence time and high moisture produces carbon dioxide and lactic acid, which can corrode unprotected mould steels; mould plates and ejector pins should be stainless or hard-chrome plated if running continuous production beyond 72 h.

In 8-cavity cold-runner tamper-evident closure moulds with 1,200 kN clamp force and wall thickness of 0.8 mm, the low modulus of Sustainable 1013 permits ejection of undercut bands with 0.4 mm depth without lifter-assisted ejection, provided the ejection temperature is below 45°C. Injection speeds of 120 mm/s to 180 mm/s and transfer at 95% fill volume prevent flash along the parting line. For snap-fit housings, insertion force is controlled by flexural modulus rather than part geometry alone; at 1.5 mm wall thickness, a cantilever snap arm with a root radius of 0.5 mm and length of 12 mm exhibits a deflection at break greater than 6 mm when tested at 23°C per a three-point loading fixture adapted from ISO 178. Published data for this specific configuration is limited, and production validation is required for cyclic snap-fit insertions above 1,000 cycles. In living hinges, a hinge thickness of 0.4 mm should be orientated perpendicular to the melt flow direction; hinge flex endurance is sensitive to packing pressure and moisture, with dry material showing no visible cracking after 1,000 flex cycles at 1 Hz over a 180° angle in an internal cyclic fixture. Because the grade is not heat resistant, continuous service above 45°C is not recommended for load-bearing parts.

Regulatory Boundary Conditions for Food Contact and Industrial Composting

Compliance claims for the neat pellet must be separated from compliance of the moulded article. Bio-based carbon content is determined by ASTM D6866 and is 90% ± 5%; this is not equivalent to biodegradability. Industrial compostability of the finished part may be evaluated according to EN 13432 or ASTM D6400, which require ≥90% biodegradation within 180 days under 58°C composting conditions, ≥90% disintegration after 12 weeks, and absence of ecotoxicity. Specific lot results must be obtained for final parts because additives, colourants, prints, and part thickness alter the result. For food-contact use, the final article must be tested under EU 10/2011 overall migration with food simulants appropriate to the intended contact; the overall migration limit is 10 mg/dm² for plastic materials. No statement of food-contact acceptance is provided for unprinted, uncoloured Sustainable 1013 beyond the results of migration testing performed on the final moulded article.

The grade is manufactured to contain <0.1% by weight of lead, mercury, hexavalent chromium, polybrominated biphenyls, and polybrominated diphenyl ethers in homogeneous material, consistent with RoHS Directive 2011/65/EU Annex II. REACH candidate list substances of very high concern are present below 0.1% w/w per article. The material is not classified as hazardous under CLP Regulation (EC) No 1272/2008. Processing fumes should be extracted, and barrel purging should not use PVC or acetal, because cross-contamination with acid-functional polymers can accelerate PLA hydrolysis. Regrind addition is limited to 20% by weight with virgin pellets; loading above 30% regrind reduces notched Izod impact by 10% to 15% and increases MFR by 1 g/10 min to 2 g/10 min due to molecular weight reduction. Drying of regrind is mandatory to 150 ppm moisture before blending.