Natureplast PLRI 001 is a recycled translucent compostable polylactic acid (PLA) grade supplied for injection molding, sheet extrusion, and thermoforming applications. The product code PLRI 001 identifies a recycled PLA stream in which translucency is retained through feedstock selection and melt filtration rather than through clarifying additives. The material is intended for rigid packaging, consumer goods, and technical components that require an industrial compostability claim under controlled conditions. Class-typical melt mass-flow rate is 5–15 g/10 min at 210 °C and 2.16 kg according to ISO 1133-1:2022. Density is typically 1.24–1.26 g/cm³ under ISO 1183-1:2019. Tensile yield is normally 45–60 MPa and flexural modulus 2 500–3 500 MPa in ISO 527-2:2012 and ISO 178:2019 specimen formats. These are class-typical values for translucent recycled PLA; a lot-specific certificate of analysis should be requested because recycled feedstock variability can shift the property envelope by several percentage points.

What processing constraints are introduced by recycled PLA feedstock?

Recycled PLA feedstock introduces three primary processing constraints: hydrolytic sensitivity, a broadened molecular weight distribution, and particulate contamination. The ester bonds in PLA are hydrolytically cleaved when the resin is heated with trace moisture. This reaction reduces molecular weight and melt viscosity, leading to shot-weight drift, splay, and reduced part strength. Because reprocessing history increases the concentration of carboxylic acid end groups, the hydrolysis in recycled PLA is more autocatalytic than in virgin PLA. Molecular weight distribution is also wider, which can lower melt strength and alter shear thinning behavior. Particulate contamination from upstream reclaim operations can reduce translucency and cause gate blemishes. These constraints do not require specialized polymer equipment, but they require stricter incoming inspection, melt filtration, and drying control than virgin PLA.

In plants where ambient relative humidity exceeds 60 %, PLRI 001 should be conveyed from sealed containers to a closed hopper dryer. Desiccant dryers with a dew point of -40 °C or lower are preferred. At 80 °C, a drying time of 4 h is usual for material that has been stored below 50 % RH. If the resin has been exposed to moisture above 1 000 ppm, drying may require 6–8 h. Moisture content should be verified below 250 ppm (0.025 wt%) by ISO 15512:2016 or an equivalent Karl Fischer method before processing. Drying above 90 °C is not recommended because pellet surfaces can soften and stick, creating feed-blockage failure modes on production hoppers.

Hydrolytic degradation is autocatalytic in recycled PLA with elevated carboxylic end groups.

PLA hydrolyzes through random chain scission of ester linkages. The reaction rate depends on temperature, water concentration, and acid end-group content. Recycled PLA that has undergone multiple thermal histories accumulates carboxylic acid end groups. These groups act as autocatalysts, so a small deviation in moisture control can produce a disproportionate loss in melt viscosity. At 80 °C and 250 ppm moisture, measurable molecular weight reduction can occur within 4–6 h. At 100 °C and 500 ppm, the same extent of degradation can occur in a shorter time. On injection lines, the first observable signs are splay, gate blush, increased purge volumes, and inconsistent melt cushion. Batch-to-batch variance in carboxyl end-group concentration should be monitored by melt flow rate and moisture analysis at incoming inspection. If stored regrind contains more than 0.5 wt% moisture, pre-drying alone may not restore original molecular weight, and the resulting molded parts may fail tensile elongation and impact requirements under ISO 527-2:2012 and ISO 180:2019.

For injection molding, the melt temperature for translucent recycled PLA is normally 180–210 °C, with a rear zone of 185 °C, a middle zone of 195 °C, a front zone of 200 °C, and a nozzle at 205 °C. Mold temperatures between 25 °C and 60 °C control crystallinity and cycle time; lower mold temperatures preserve translucency but increase residual stress. Hydraulic back pressure is typically 0.5–1.5 MPa, and screw decompression should remain below 3 mm to avoid air entrapment and splay. Melt temperatures above 230 °C are not recommended because lactide reformation and brown discoloration occur more rapidly in recycled PLA than in virgin grades. The injection unit should be sized so that shot volume uses 20–80 % of barrel capacity; a shot weight below 20 % increases residence time and thermal degradation of PLA. Barrel residence time should not exceed 5 min at 200 °C. Mold shrinkage is generally 0.2–0.5 % flow-direction and 0.3–0.7 % transverse under ISO 294-4:2018, but cavity-pressure validation on the actual tool is preferred over supplier data because recycled feedstock shifts shrinkage with molecular weight distribution.

Rheological boundaries at high shear and typical screw configurations

PLRI 001 is shear-thinning and sensitive to shear heating. In a capillary rheometry trace at 200 °C, apparent viscosity for translucent recycled PLA typically decreases from approximately 800 Pa·s at 100 s^-1 to below 100 Pa·s at 1 000 s^-1. These values are indicative for the class; published data for this specific configuration is limited. General-purpose screws with L/D 24:1–30:1 and compression ratios of 2.5:1–3.0:1 are acceptable, while low-shear barrier screws are preferred for sheet extrusion to limit temperature overshoot. Excessive screw speed or undersized gates create shear heating that reduces molecular weight and increases yellowing. Hot-runner systems should use open, minimally restrictive flow channels; gate diameters below 0.8 mm can create local temperature spikes and black specks in recycled PLA. Continuous screen filtration with 80–120 mesh elements is typical on recycling lines to remove particulates and preserve translucency.

Fill simulation for PLRI 001 should use a melt density of approximately 1.1 g/cm³ at 200 °C and a solid density of 1.25 g/cm³. The transition temperature can be set to 55–60 °C and the freeze temperature near 150 °C. Shear-viscosity data should be fitted with Cross or Bird-Carreau coefficients generated from capillary rheometry on the actual lot. Published data for this specific configuration is limited, so generic PLA simulation parameters should not be used for precise gate sizing. In a single-screw extruder with L/D 30:1 and a melt pump, the pressure drop across a 100 mesh screen pack may be 5–15 bar depending on contamination level and throughput.

Sheet extrusion and cast film use a melt temperature of 170–195 °C and a polished roll stack set between 20 °C and 40 °C to limit crystallinity and retain translucent appearance. Because recycled PLA has lower melt strength than virgin PLA, draw ratios exceeding 3:1 in cast film may cause edge tear. In thermoforming, sheet preheat temperatures of 90–110 °C are typical for amorphous PLA; sheet thickness above 2 mm may require longer indexing to prevent cold cracking. Mineral fillers above 5 wt% are generally not used in this translucent grade because they raise opacity and can disturb disintegration during controlled composting.

When should PLRI 001 be selected instead of virgin PLA or PLA/PBAT compounds?

PLRI 001 occupies an intermediate position between virgin PLA and flexible compostable polyesters. Virgin PLA typically shows a tensile yield of 60–70 MPa and an elongation at break of 3–8 %. Translucent recycled PLA from controlled feedstocks commonly falls at 45–60 MPa tensile yield and 2–5 % elongation at break. The reduction is not wholly a strength deficit; recycled feedstock lowers polymer demand, but quantitative life-cycle comparison should follow ISO 14040:2006 and ISO 14044:2006 rather than generic carbon-intensity statements. Compared with PLA/PBAT or PLA/PCL blends, PLRI 001 remains rigid and is not suitable for applications requiring elastic deformation above 10 %. Compared with opaque recycled PLA compounds containing mineral fillers or pigment, PLRI 001 retains translucency because the feedstock is selected and melt-filtered to limit particulates. Other recycled PLA grades are often filled with talc or calcium carbonate that raises opacity and can reduce compostability if the filler alters disintegration behavior.

The comparative table demonstrates that the recycled grade typically trades some tensile yield, elongation, flexural modulus, and impact for recycled content and lower polymer consumption. The difference is not necessarily a simple downgrade; it is a shift in property envelope and process control requirements. For applications where tensile strength above 60 MPa or impact above 5 kJ/m² is required, virgin PLA or an impact-modified grade should be specified. For rigid applications that tolerate tensile yield between 45 MPa and 60 MPa and require translucency plus an industrial compostability claim, PLRI 001 is technically appropriate, subject to lot-specific validation.

What limitations arise in food-contact and high-humidity end-use environments?

Because PLRI 001 derives from reclaimed feedstock, it cannot be assumed to comply with food-contact regulations such as EU No 10/2011 or FDA 21 CFR 177 unless the supplier provides migration testing and a specific compliance letter for the recycled lot. Recycled content can introduce trace non-intentionally added substances, and compliance for this specific configuration should be confirmed with the manufacturer before use in food-contact articles. In high-humidity service, PLA is generally limited by hydrolysis; continuous exposure above 50 °C and 80 % RH is outside the recommended operating envelope. End-use testing according to ASTM D6400-21 or EN 13432:2000 addresses controlled compostability, not durability in humid storage. The grade is not suitable for load-bearing applications above its Vicat softening temperature of approximately 55–60 °C. Under EN 13432:2000, compostability requires chemical characterisation, biodegradation, disintegration, and ecotoxicity criteria. PLA biodegradation typically requires industrial composting temperatures above 58 °C; therefore PLRI 001 should be labeled as industrially compostable and not as home compostable unless a separate certification exists.

Storage at ambient temperatures below 30 °C and relative humidity below 50 % is recommended. In plants without climate control, the material should not remain in unsealed containers for more than 24 h before drying. Lot-to-lot variability in recycled feedstock can shift melt flow rate by several units; incoming inspection should include ISO 1133-1:2022 melt flow rate and moisture analysis by ISO 15512:2016. Blending with virgin PLA is possible to reduce variability, but the addition changes translucency and melt viscosity, and the mixing ratio should be validated with tensile specimens conforming to ISO 527-2:2012.

Scrap sprues and runners can be reincorporated at 20–30 % by weight if they are dry, uncontaminated, and not thermally degraded. Higher regrind fractions may cause visible specks and loss of translucency. Alkaline fillers, amine-based additives, and certain ammonium salt additives should be avoided because residual alkalinity accelerates hydrolytic chain scission of PLA. The material should not be compounded with polyolefins without compatibilization, as olefin contamination causes delamination and opaque domains. Equipment should be purged with a low-viscosity PLA or a commercial purging compound when transitioning from polyolefins to avoid cross-contamination.