Polylactic Acid (PLA) REVODE213 is an unfilled, injection-moulding-grade thermoplastic polyester supplied in pellet form within the REVODE series of Zhejiang Hisun Biomaterials Co., Ltd. The resin is positioned for thin-wall disposable cutlery, food-service packaging, cosmetic packs, toys, and non-structural consumer electronic housings. Its melt-viscosity profile is lower than that of REVODE101 and REVODE110 extrusion and thermoforming grades, which reduces filling pressure in multi-cavity tools at flow length-to-wall-thickness ratios above 150:1. As a poly(L-lactic acid) with controlled D-lactic acid content, the grade remains semi-crystalline but is typically moulded in the amorphous state to retain optical clarity. Batch-controlled properties include melt flow rate, tensile properties, flexural modulus, impact strength, and residual lactide content; the certificate of analysis controls each production lot.

Representative values for unfilled PLA injection-moulding materials of this viscosity class include density of 1.24 g/cm³ by ISO 1183-1:2019, tensile strength of 60–70 MPa by ISO 527-2:2012, flexural modulus of 3,300–3,600 MPa by ISO 178:2019, notched Izod impact of 2.5–4 kJ/m² at 23 °C by ISO 180:2019, and heat deflection temperature of 50–60 °C at 0.45 MPa by ISO 75-2:2013 Method B for amorphous specimens. Glass transition is observed near 55–60 °C and the melting endotherm near 150–170 °C when measured by differential scanning calorimetry under ASTM D3418-21. Published property ranges for REVODE213 follow these typical values, but supplier technical bulletins and lot-specific certificates remain the governing documents.

What separates this injection-moulding grade from extrusion and thermoforming PLA resins?

The principal difference between REVODE213 and extrusion-grade REVODE101 is melt viscosity. Lower melt viscosity permits shorter cavity filling time and better replication of thin sections, but the reduced molecular weight also lowers notched Izod impact relative to higher-viscosity PLA grades. Thermoforming grades such as REVODE110 are typically formulated for high melt strength and sheet extrusion; they exhibit lower melt flow rates and greater sag resistance. In injection moulding, such grades can require higher melt temperatures and higher injection pressures. REVODE213, by contrast, is adjusted for short filling times and thin-wall flow, but the reduced molecular weight can lower notched impact toughness relative to higher-viscosity PLA grades.

Melt flow rate differences are not the only distinguishing variable. Molecular weight distribution, D-lactic acid content, and additive package affect crystallization rate and part appearance. In injection-moulding PLA, melt flow rates are typically measured at 210 °C with 2.16 kg load; a low-flow grade used for sheet may show 3–9 g/10 min, whereas an injection-moulding grade usually falls between 10–30 g/10 min. This flow increase shortens fill time but may lower melt strength; hot-runner valve-gate systems are therefore preferred over open gates when the tool has more than eight cavities.

Because PLA polymerizes and degrades through reversible esterification, batch-to-batch variation in residual lactide and moisture can alter the effective melt flow rate even when the nominal grade is unchanged. Incoming inspection should record melt flow rate on dried pellets and compare with the supplier certificate; a shift of more than 3 g/10 min from the established baseline can indicate moisture damage or lot-to-lot molecular weight variation.

Before melt processing, the resin must be dried in a desiccant dryer to a residual moisture level below 250 ppm. Drying at 80 °C for 4 h with a dew point of −40 °C or lower is a standard reference profile for PLA; when ambient relative humidity exceeds 60%, drying time is extended to 6 h and the hopper is kept under dry-air purge. Residual moisture above 250 ppm hydrolyzes the polyester backbone in the barrel, producing splay, lower melt viscosity, and a measurable reduction in molecular weight during plastication. Pellet temperatures above 90 °C in storage hoppers are to be avoided because pellet agglomeration can obstruct the feed throat.

Moisture analysis is performed with a Karl Fischer titration or a calibrated loss-on-drying instrument; 250 ppm corresponds to 0.025 wt% water. Handheld moisture probes are generally insufficient for this threshold. Dryer validation should include air-flow rate, dew-point measurement at the return line, and pellet residence time. The hydrolysis reaction is accelerated by both melt temperature and residence time; at melt temperatures above 220 °C, visible silver streaking can appear within 5–8 min of residence. Unvented barrels are adequate only if the incoming moisture specification is met; a vacuum-vented barrel is not a substitute for drying because the hydrolysis reaction occurs in the melt before volatiles can be extracted.

Processing experience on production equipment shows that moisture-related defects appear as silver streaking at the gate and a sharp decrease in part ductility. The failure mode is often misdiagnosed as mould venting; verification of dryer dew point and actual pellet inlet temperature is therefore required before adjusting injection parameters.

Injection moulding parameter envelope and equipment boundaries

The moulding window for REVODE213 is narrower than that of many amorphous styrenic resins. Melt temperature at the nozzle is normally maintained between 190 °C and 210 °C; residence time above 15 min at these temperatures accelerates thermal degradation and generation of lactide, causing yellowing and screw deposits. Barrel zone settings from hopper to nozzle generally progress from 160–180 °C in the feed zone to 190–210 °C at the nozzle, with the feed throat held below 50 °C to prevent bridging.

Screw geometry should use a low-shear general-purpose design with L/D of 20:1 to 24:1 and compression ratio of 2.5:1 to 3:1. Deep-feed or highly compressive screws can over-shear the low-viscosity melt, causing temperature spikes above the degradation threshold. A free-flow check ring and a nozzle with independent heating and positive shut-off are preferred for thin-wall multi-cavity tools because the melt tends to drool at low melt viscosity. For hot-runner systems, valve-gate nozzles with internal heating and no dead pockets are used. PLA can accumulate in stagnation zones and form lactide-rich residue that intermittently releases into the part as black specks. Hot-runner temperature should be kept within 190–210 °C, and colour changes should be minimized because PLA has a narrow processing window and degraded purge material can contaminate optical surfaces.

Mould temperature determines whether the part retains the amorphous transparent condition or develops crystalline haze and improved temperature resistance. For cold-mould forming, 20–40 °C yields glossy transparent surfaces and shorter cooling time. For crystallizing operations, mould temperatures of 80–110 °C are used; cycle time increases and dimensional shrinkage must be compensated with more aggressive holding pressure. Clamp force requirement is determined by the projected area of the cavities and the melt pressure required to pack the part. For thin-wall cutlery with wall thickness below 1.0 mm, filling pressure at the transfer point can approach 100 MPa; a hydraulic machine with direct pressure control and a closed-loop transducer is preferred to a simple open-loop machine because the viscosity difference between PLA and styrenics changes the pressure integral during switching.

Dimensional stability can be improved by post-mould annealing. Amorphous parts heated above 60 °C begin to soften; annealing at 80–100 °C for 30–60 min under restraint can increase crystallinity and raise the heat deflection temperature, but uncontrolled annealing can warp thin sections and reduce transparency. Mould temperature crystallization achieves some of this in-cycle but requires higher tool temperatures and longer holding times.

Applications for REVODE213 are concentrated in articles where stiffness, clarity, and industrial compostability are primary requirements and where continuous service temperature remains below the amorphous heat deflection envelope. Injection-moulded cutlery, clear lids, cosmetic packaging, and toys are common application categories. In these uses, the resin competes with general-purpose polystyrene and ABS on stiffness but not on impact or high-temperature performance. Compared with ABS, REVODE213 exhibits higher tensile modulus but lower notched Izod impact and lower practical service temperature unless crystallization is induced. The mould shrinkage of PLA is typically 0.3–0.5% in both flow and transverse directions under ASTM D955-21, which is lower than many ABS grades at 0.5–0.9%; tooling must be adjusted accordingly. Compared with impact-modified PLA blends, neat REVODE213 provides higher clarity and stiffness but reduced elongation at break, which is typically below 5% for unmodified PLA.

Biodegradability and industrial compostability are end-of-life attributes of the finished article, not the pellet. Certification under EN 13432 or ISO 17088 requires testing of the final item; additives, printing inks, and thickness can affect disintegration and ecotoxicity outcomes. Food-contact suitability must also be assessed on the finished article. The base resin may be evaluated under EU Regulation 10/2011 and applicable FDA food-contact notifications, but colorants, processing aids, and degradation by-products can alter overall migration. REVODE213 is subject to REACH registration and the RoHS Directive 2011/65/EU as amended by (EU) 2015/863 for electrical and electronic housings only when the finished product falls within the scope.

When REVODE213 replaces amorphous petrochemical thermoplastics in rigid disposable articles

When the grade is substituted for ABS or polystyrene in rigid disposable parts, three processing differences are observed. First, the melt is more shear-sensitive and less thermally stable; barrel temperature must be reduced relative to ABS. Second, the lower melt viscosity can create flashing at parting line clearances that would be acceptable for a styrenic resin, so clamp force and mould maintenance limits must be reviewed. Third, the low melt temperature and high solidification rate can produce gate blush and flow marks if injection velocity is too low; injection velocities above 60 mm/s are commonly used for thin-wall PLA cutlery, with short-shot trials and gate-seal studies performed under ISO 294-1:2017.

Against general-purpose polystyrene, PLA REVODE213 has greater stiffness and environmental end-of-life options but lower melt thermal stability and higher sensitivity to moisture. The required melt temperature is lower, which reduces cooling demand but narrows the melt-temperature window. Against ABS, the PLA grade has inferior impact, lower heat deflection, and different chemical resistance; esters, ketones, and some alcohols can attack PLA, while ABS resistance also varies. The material should be tested with actual service chemicals.

Published data for REVODE213 in hot-fill or retort packaging configurations is limited beyond the amorphous HDT envelope. The resin is not formulated for flame-retardant performance, UV-stabilized outdoor service, or load-bearing applications above 50 °C unless annealed or crystallized. Combination with amine-based additives should be evaluated case-by-case because residual acidity and moisture can hydrolyze the PLA backbone during storage or processing. Use of regrind is possible only when the regrind is dried to the same moisture specification and its proportion is controlled to avoid viscosity drift; published data for high-percentage regrind in this specific grade is limited.