The product designation FC 60000 identifies a crystallized compostable injection molding poly(lactic acid) grade. In industrial practice, “crystallized” refers to a formulated PLA system in which nucleation chemistry and stereochemical balance allow lamellar growth during elevated mold-temperature cycles. Amorphous PLA can be quench-cooled but typically retains dimensional stability only below approximately 55 °C under 0.45 MPa load. Crystallized injection molding PLA, when molded with adequate crystallization time, may maintain service temperatures approaching 90–110 °C. The final crystallinity is not an inherent pellet property; it depends on tool temperature, cooling rate, part wall thickness, and residence time. The lot certificate for melt flow rate, residual lactide, and moisture content is therefore the only reliable basis for startup parameters.

What Process Limits Distinguish Crystallized PLA from Amorphous Injection Molding Grades?

The principal process difference is the requirement that the polymer be retained above its crystallization temperature long enough for spherulitic growth. A crystallized grade such as FC 60000 typically exhibits a melt flow rate determined under ISO 1133-1:2022 at 210 °C with 2.16 kg load. Published values for crystallized injection molding PLA are commonly in the 10–30 g/10 min range. The crystallization half-time is reduced by nucleating agents; differential scanning calorimetry under ISO 11357-3:2018 is used to verify the cold-crystallization peak and melting endotherm. A low D-lactide content, generally below 1.5 mol%, increases crystallization rate and maximum achievable crystallinity. The processing consequence is a narrower melt-temperature window than amorphous PLA: melt temperatures below 180 °C produce short shots and poor knit-line strength, while sustained melt temperatures above 210 °C accelerate thermal degradation, lactide reformation, and volatile formation. On a 100-tonne hydraulic injection molding machine with a 20:1 to 24:1 L/D general-purpose screw, short-shot generation has been observed when the nozzle drops below 195 °C; raising the nozzle temperature in 5 °C increments without increasing back pressure restored flow length in thin-wall tools.

Pre-drying is mandatory before plastication. PLA hydrolyzes at processing temperatures when moisture exceeds 0.025 wt% (250 ppm). A desiccant dryer set to 80 °C for 4 h with a dew point of −40 °C is typical; hopper residence times exceeding 8 h at elevated temperature can advance crystallization in the feed throat and cause feed bridging. The shot size should occupy between 40% and 70% of barrel capacity to limit residence time. Purging with melt-stable polypropylene or a dedicated PLA purge grade reduces black specks and carbonized deposits during material transitions. Multi-cavity production records indicate that mold surface temperature variation should be held within ±5 °C to prevent differential shrinkage and warpage in flat parts with wall sections below 2.5 mm.

For multi-cavity tools, cold or hot runner selection alters the thermal history. Hot runner systems are generally preferred for high cavitation because they eliminate cold runner regrind, but thermal degradation in the manifold becomes significant if the melt is held above 210 °C for more than 5 min. Gate diameters below 0.8 mm are not recommended for filled or nucleated PLA because high shear heating can exceed 230 °C locally, causing discoloration and viscosity reduction. Ejector pins must be large and well distributed because crystallized PLA exhibits high modulus and can stick to polished surfaces; draft angles of 0.5–1.0° per side are commonly specified for textured surfaces. External release agents may improve ejection, but such agents may interfere with compostability and should be confirmed under EN 13432:2000 before use.

The Tool Temperature Boundary Is Determined by Crystallization Rate

Three interdependent parameters control the crystalline content of an injection molded PLA part: moisture before plastication, melt temperature during screw recovery, and mold surface temperature during holding and cooling. If the mold surface is below 80 °C, the solidification rate exceeds the crystallization rate, and the part remains largely amorphous with lower heat resistance. Mold temperatures in the 90–110 °C range are frequently cited for crystallized PLA grades; the exact optimum must be derived from cavity-pressure data, gate geometry, and part thickness. At wall sections above 4 mm, internal heat retention can slow cooling and extend cycle time beyond 60 s. This creates the process conflict: the cycle time required for full crystallinity may not be economically viable without conformal cooling or intensified nucleation. A typical barrel profile is rear 170–180 °C, middle 190–200 °C, front 200–210 °C, and nozzle 195–205 °C. Hot runner manifold temperatures should not exceed 210 °C for residence times over 5 min, because thermal degradation increases the concentration of lactide and trace acetic acid, which lowers molecular weight and can corrode tool surfaces if vents are inadequate.

In a side-gated rectangular plaque tool with a nominal wall thickness of 2 mm, published data for crystallized PLA grades show that raising the mold temperature from 80 °C to 100 °C increased heat deflection temperature under 0.45 MPa from approximately 58 °C to 88 °C, while cooling time increased by 12–18 s. Published data for this specific configuration is limited; the values should be treated as directional rather than lot-specific. The cooling time increase is non-linear because crystallization releases latent heat, delaying solidification. Molding trials should therefore use instrumented cavity-pressure sensors to determine when the gate freezes and when hold pressure can be released without sink.

The crystallization kinetics of PLA are often modeled using the Avrami equation, in which the Avrami exponent n typically ranges from 2 to 4 depending on nucleation mode. For crystallized PLA grades under isothermal conditions near 100 °C, the crystallization half-time may be reduced to 1–3 min in differential scanning calorimetry experiments, whereas the half-time for unmodified PLA can exceed 10 min. This acceleration is the central justification for the term “crystallized” in the product designation. The practical effect is shorter in-mold cooling time to achieve a given crystallinity, but not full elimination of cooling time because the part must be below the heat deflection temperature before ejection to avoid dimensional change.

When FC 60000 Replaces Amorphous PLA in Rigid Packaging

The material is applicable to rigid packaging, cosmetic components, single-use serviceware, and non-load-bearing industrial inserts that require a compostability claim under EN 13432:2000 or ASTM D6400-21. The choice is technically appropriate when the part must resist deformation during hot filling or transport at temperatures up to approximately 90 °C. It is less suitable for impact-dominated applications because of the notched Izod range below 4 kJ/m². Compared with amorphous PLA, the crystallized grade provides a higher thermal ceiling but lower optical clarity in thick sections due to spherulitic haze. Compared with polypropylene, the grade offers higher flexural modulus but requires a narrower processing window and predrying. Compared with mineral-filled PLA compounds, FC 60000 is expected to retain translucency in thin sections only if the nucleator dispersion is fine and soluble; coarse nucleator particles produce haze and can reduce tensile elongation at break. The absence of glass fiber means lower tensile modulus than glass-filled PLA, but the product remains compatible with industrial composting streams when all constituents meet EN 13432:2000 or ISO 17088:2021.

Crystallized PLA grades exhibit higher modulus and lower impact toughness than many amorphous PLA packaging grades. The tensile strength, when tested under ISO 527-2:2012, is generally reported in the 60–70 MPa range for injection molded crystallized PLA; flexural modulus under ISO 178:2019 is often 3500–4200 MPa. Notched Izod impact resistance under ISO 180/A is typically 2–4 kJ/m², indicating sensitivity to sharp radii and stress concentrations. The crystalline morphology increases density to approximately 1.24–1.26 g/cm³ under ISO 1183-1:2019 and shifts the heat deflection temperature upward. Shrinkage is anisotropic: machine-direction shrinkage is commonly 0.3–0.5%, while transverse-direction shrinkage may reach 0.4–0.7% depending on mold temperature and gate design. Post-mold dimensional change can occur if the part is annealed above the glass transition temperature or exposed to environments above 55 °C without full crystallinity.

Standard amorphous PLA pellets soften and become sticky at 60 °C; crystallized pellet surfaces may survive brief exposure to 80 °C without agglomeration, but prolonged use above 80 °C can still promote bridging. The melt viscosity of crystallized PLA at 210 °C is typically more shear-thinning than amorphous PLA due to nucleating additives and possible chain architecture differences. Capillary rheometry under ISO 11443:2021 can be used to compare the shear viscosity curves of FC 60000 against an incumbent amorphous PLA; the ratio of zero-shear viscosity to viscosity at 1000 s⁻¹ may be higher, indicating a more pronounced non-Newtonian response.

Compostability Certification and Final-Article Verification

Compostability certification applies to the final article, not to the pellet alone. Additives, colorants, print inks, and adhesive labels can alter the overall composting behavior, and the grade should be evaluated in the intended final configuration. Under ISO 14855-1:2012, aerobic biodegradation is measured under controlled composting conditions at 58 °C; the grade itself can be expected to biodegrade through hydrolysis of ester linkages followed by microbial assimilation, but the reported conversion percentage depends on sample surface area, thickness, and the inoculum source. The crystallized morphology may slow the initial hydrolysis rate relative to amorphous PLA because chain mobility and water uptake are lower in the crystalline domains.

Operational boundaries include a maximum recommended melt temperature of 210 °C and a maximum hopper residence time of 8 h at 80 °C. The material is incompatible with prolonged contact with strong aqueous bases and high-humidity storage at relative humidity above 60% without sealed packaging; moisture regain above 0.025 wt% before processing can reduce molecular weight by hydrolytic chain scission. The use of amine-based additives is not documented for this grade; additives should be validated for pH and volatiles because residual alkalinity can accelerate chain degradation. For food-contact articles, compliance must be verified under the applicable jurisdiction-specific regulation, such as EU Regulation 10/2011 or FDA 21 CFR food-contact clearance; published data for this specific product designation is limited, and a migration protocol should be completed by the converter before commercial use.