Ingeo™ Biopolymer AW 300D Rigid Heat Resistant Molding PLA is a semicrystalline polylactide resin intended for injection molding of rigid parts that must withstand short-term thermal exposure beyond the capability of unmodified amorphous PLA. The grade belongs to the heat-resistant Ingeo molding class and is differentiated from general-purpose injection-molding PLA by a controlled stereochemical composition that promotes crystallization during elevated mold-temperature processing or post-mold annealing. The material is unfilled, so its mechanical response retains the high tensile modulus and low elongation characteristic of rigid PLA rather than the ductile behavior of impact-modified bio-based compounds. In production practice, the heat-resistance benefit is realized only when the tool is operated in the crystallization window or when the part is annealed after demolding. Published product-specific datasheet values for this grade are limited; processing and property statements below are therefore anchored to the behavior of commercial heat-resistant PLA molding grades and to standard polylactide characterization methods. Lot-specific melt flow rate, residual monomer, and moisture content should be obtained from the certificate of analysis before process qualification.

How Does Low D-Isomer Content Sustain Elevated Heat Deflection?

The thermal performance of PLA is governed less by its 60°C to 65°C glass transition than by the fraction of crystallinity developed during processing. General-purpose PLA often exhibits a heat deflection temperature near 55°C under a 0.455 MPa flexural load when tested according to ASTM D648-18 or ISO 75-2:2013, because conventional mold temperatures are too low to develop significant crystal content. In heat-resistant grades such as AW 300D, the D-lactide content is reduced—typically below 2 mol% in this resin class—to limit chain defects and allow rapid spherulite growth. Nucleating agents may also be present to increase the crystallization onset temperature and reduce the isothermal hold time in the tool. Once crystallization is driven to completion by mold heat or annealing, the deflection temperature can exceed 100°C; however, the value is not an inherent resin constant. It is a process-dependent response that varies with mold temperature, cavity pressure, wall thickness, cooling time, and the restraint applied during post-mold crystallization.

Before melt processing, this material class requires desiccant drying to prevent hydrolytic degradation. Residual moisture above 250 ppm accelerates chain scission at melt temperatures, producing a measurable loss of melt viscosity, gate-area silver streaking, and reduced impact toughness in molded parts. On production-scale dehumidifying dryers with a dew point of -40°C or lower, virgin pellets are commonly dried at 80°C for 4 h to 6 h. The drying hopper should be sized for at least 2 h of residence at the target throughput; a hopper residence below the drying time will continuously deliver under-conditioned material to the feed throat. Regrind additions above 20 wt% may require longer drying because partially crystallized scrap releases moisture more slowly than amorphous virgin pellets. After drying, exposure to ambient air should be minimized unless the machine hopper is blanketed with dry air; plant-floor relative humidity above 60% can reintroduce moisture in less than 30 min in fine regrind fractions.

Melt Temperature and Check-Ring Recovery in Reciprocating Screw Units

On injection molding machines with screw L/D ratios from 20:1 to 24:1, the melt temperature for this high-heat PLA class is maintained between 190°C and 230°C. The feed zone temperature is set at 20°C to 40°C to avoid pellet bridging, while the compression and metering zones are profiled upward to the target melt temperature. The shot size should occupy 40% to 70% of barrel capacity, and total melt residence time should be kept below 8 min when the barrel is above 220°C. Screw speed for screw diameters from 25 mm to 50 mm is typically set between 50 rpm and 120 rpm, with back pressure held below 0.7 MPa to limit viscous heating. Injection velocity is adjusted for flow length and gate geometry; linear screw velocities from 50 mm/s to 150 mm/s are common. The non-return valve should be inspected for polymer stagnation because PLA degrades in dead spots, releasing lactide and causing discoloration. A worn check ring can also reduce volumetric consistency and amplify shot-to-shot weight variation beyond 0.3%.

Heat resistance is developed in the tool only when the mold surface temperature is held within the crystallization range. Mold circuits are commonly operated at 90°C to 120°C, using water at elevated pressure or oil for the upper range. Lower mold temperatures may replicate the appearance of standard PLA but leave the part with insufficient crystallinity to resist post-mold distortion above the glass transition. Cavity-to-cavity temperature variation should be controlled within ±5°C because localized differences in crystallization rate create anisotropic shrinkage, gate-area sinking, and warpage. Hot-runner manifolds should be limited to 230°C, and gate tips should be thermally isolated from mold cooling to prevent premature freeze-off. In thin-wall sections below 2 mm, the cooling rate can arrest crystal growth before sufficient conversion; these geometries may require elevated mold temperatures, nucleating additives, or post-mold annealing to reach the intended heat-deflection outcome.

When Post-Mold Annealing Replaces Extended In-Mold Crystallization

If cycle-time requirements prevent full in-mold crystallization, parts may be removed after surface solidification and transferred to a constrained annealing fixture. Annealing is typically conducted at 100°C to 120°C for 15 min to 60 min, depending on wall thickness, part mass, and the desired crystalline fraction. The fixture must hold the part in the intended shape because the density increase during crystallization produces anisotropic shrinkage; unconstrained annealing can generate linear shrinkage from 1.0% to 2.5% in the flow direction and 0.5% to 1.5% across the flow front. Flat parts longer than 200 mm can show out-of-plane deflection greater than 5 mm when annealed without restraint. The annealing step is appropriate for hot-fill containers, cooking appliance components, and automotive interior parts that face intermittent service near 100°C, but it adds handling cost and can create surface gloss variation if the fixture contacts the part unevenly.

Mold design for high-heat PLA must accommodate anisotropic shrinkage rather than assuming a single isotropic value. Depending on mold temperature, part thickness, and gate geometry, published values for unfilled heat-resistant PLA range from 0.3% to 1.2% in the flow direction and from 0.5% to 1.8% across flow. Ejection forces increase when mold surfaces are polished below 0.2 µm Ra; draft angles below 0.5° on deep cores can cause scuffing, especially on crystalline surfaces that are harder than amorphous PLA surfaces. Venting depths at the parting line are maintained between 0.02 mm and 0.03 mm to prevent gas burn at the end of fill without creating flash. If ejection is attempted before the surface has crystallized sufficiently, the part may exhibit fingernail indentations, witness marks, or permanent deformation at the ejector pin points.

The practical distinction between this product and general-purpose Ingeo molding grades is primarily thermal: standard amorphous grades soften near 55°C under load, whereas a crystallized AW 300D part can tolerate short-term service above 100°C. The difference is not achieved through copolymerization or impact modification, so the rigid character of PLA is retained. Compared with impact-modified PLA, the AW 300D class provides higher tensile modulus—typically in the range of 3.0 GPa to 3.6 GPa according to ISO 527-2:2012—but lower notched impact strength, usually below 20 J/m by ASTM D256-23. Compared with amorphous ABS, the material has a higher density near 1.24 g/cm³ versus 1.04 g/cm³, and lower elongation at break. Compared with isotactic polypropylene, it offers higher modulus and lower creep under room-temperature load, but requires more aggressive drying and a tighter processing window. Table 1 summarizes representative class-level values; they are not lot-specific AW 300D data.

Which Standards Govern Comparative Property Evaluation and Regulatory Review?

Routine incoming resin evaluation for this class should include melt volume-flow rate according to ISO 1133-1:2022 at 210°C with 2.16 kg, tensile properties according to ISO 527-2:2012 or ASTM D638-14, flexural modulus according to ASTM D790-17, and heat deflection according to ASTM D648-18 or ISO 75-2:2013. Polymer melting behavior may be characterized by differential scanning calorimetry under ISO 11357-3:2018, with the crystallization exotherm and melting endotherm used to estimate crystalline fraction and to verify that drying has not shifted the thermal signature. For food-contact parts, compliance must be evaluated on the finished article under the relevant jurisdiction; resin documentation may support a regulatory review under appropriate food-contact provisions, but specific suitability must be confirmed for the final composition and end-use conditions. For industrial articles, documentation should address REACH 1907/2006/EC and RoHS Directive 2011/65/EU Annex II restrictions as applicable.

On manufacturing lines producing small appliances or food-service articles, the achievable heat resistance of an AW 300D-class material is often validated by thermal soak at 80°C to 110°C under a fixed load, using part-specific fixtures rather than relying on resin-level HDT alone. Warpage and creep in such tests are controlled by crystallinity, part thickness, and gate design; thin diaphragms and deep ribs are more sensitive to residual orientation and may require lower annealing temperature or longer cycle time. For assemblies containing metal inserts, the insert temperature should be held near the mold temperature before overmolding to avoid premature crystallization at the interface, which generates weld-line weaknesses and stress cracks. For processes that require post-mold machining or ultrasonic welding, the crystalline surface is harder and less prone to smearing than amorphous PLA, but weld parameters must be re-established because the amorphous skin is thinner after high-temperature molding.