VeryGreen™ VG7264 High Impact High Heat General Purpose Polylactic Acid is a compounded poly(lactic acid) grade supplied as opaque off-white cylindrical pellets for injection molding and extrusion. The VG7264 designation identifies a high-impact, high-heat, general-purpose PLA within the manufacturer’s VG72 series; the numerical suffix denotes the specific impact-modified and nucleated formulation sequence rather than a melt flow rating. Density is stated as 1.24–1.26 g/cm³ under ISO 1183-1:2019, and melt flow rate is given as 10–18 g/10 min at 210 °C with a 2.16 kg load under ISO 1133-1:2022. The product is formulated to raise heat deflection temperature and notched impact resistance above those of unmodified PLA while maintaining density below that of mineral-filled PLA. The compound contains a nucleating package, an impact modifier, and a chain-extension system; it is not a neat resin and requires drying, melt temperature, and residence-time control beyond those used for standard PLA.

Typical mechanical values are 58–65 MPa tensile strength at yield under ISO 527-2:2012, 2.6–3.0 GPa tensile modulus, 8–15 % nominal tensile strain at break, 12–20 kJ/m² notched Izod impact at 23 °C under ISO 180:2023 Method 1A, and 95–110 °C HDT-B at 0.45 MPa under ISO 75-2:2013 Method B. These values are manufacturer-typical data from injection molded multipurpose specimens conditioned for 48 h at 23 °C and 50 % RH in accordance with ISO 291:2018; they are not specification limits. The grade is intended for candidate applications where unmodified PLA would fail through low notched impact or low HDT-B, and where mineral-filled PLA would impose excessive density or surface dullness.

What Limits the Injection Molding Processing Window for VG7264?

The processing window is bounded at the lower end by high melt viscosity and screw torque, and at the upper end by polyester chain scission and impact-modifier coalescence. Production-scale trials on a 1600 kN hydraulic clamp injection molding machine with a 40 mm diameter, 22:1 L/D general-purpose screw and reverse-taper check ring demonstrated stable shot control with barrel zone temperatures of 195 °C, 205 °C, 210 °C, and 215 °C from feed to nozzle. At melt temperatures below 195 °C, screw torque increases by 10–20 % compared with unmodified PLA, and short shots occur in sections thinner than 1.2 mm. At melt temperatures above 225 °C or residence times longer than 8 min at 210 °C, the melt flow rate shifts upward and notched Izod impact decreases by more than 25 % due to hydrolytic chain scission and modifier phase degradation. The recommended melt temperature window is therefore 200–220 °C, with a maximum heater-band setpoint of 230 °C for short residence periods only.

Injection pressure for a 2 mm spiral-flow mold at 210 °C is typically 70–110 MPa, and hold pressure is maintained at 50–70 % of injection pressure. Back pressure is set at 0.3–0.7 MPa; higher back pressure introduces shear heating and can push melt temperature above the degradation threshold. Screw surface speed is limited to 0.2–0.4 m/s to avoid local shear rates above 100,000 s⁻¹, at which the impact-modifier domains may coalesce and reduce gate-region toughness. Mold temperatures must remain between 90 °C and 110 °C for the nucleation package to develop sufficient crystallinity. At mold temperatures below 80 °C, HDT-B can fall to 75–85 °C, which is below the product’s high-heat classification. Cooling time for a 2 mm wall at 100 °C is 20–30 s, approximately 30–50 % longer than unmodified PLA because of the crystallization exotherm and mold heat rejection.

Capillary rheometry data obtained according to ISO 11443:2021 indicate an apparent melt viscosity of 300–600 Pa·s at 210 °C and 100 s⁻¹, falling to 80–150 Pa·s at 1000 s⁻¹. Differential scanning calorimetry used in accordance with ISO 11357-3:2018 indicates an isothermal crystallization half-time at 110 °C of 4–7 min, compared with 12–18 min for unmodified PLA. This faster crystallization permits shorter hold times but narrows the mold-temperature operating band; if mold temperature deviates by more than ±5 °C from the optimized value, warpage and inconsistent HDT-B are observed in parts with wall-thickness transitions.

Failure modes observed during production trials include gate blush when injection speed exceeds 400 mm/s in a 2 mm wall, weld-line brittle fracture when melt temperature drops below 200 °C, and moisture splay at the flow front when pellet moisture exceeds 0.03 %. Weld-line notched Izod impact is approximately 40–60 % of bulk impact; for parts with weld lines, the mold should be gated to place weld lines in low-stress regions. Mold shrinkage in the flow direction is 0.4–0.7 % and transverse shrinkage is 0.5–0.9 % after 48 h at 23 °C. Shrinkage anisotropy is lower than mineral-filled PLA but higher than unmodified PLA in thick sections. Post-mold annealing at 100 °C for 30–60 min may increase crystallinity and HDT-B by 5–10 °C, but parts can grow 0.2–0.5 % and must be fixtured during annealing.

The following comparison places VG7264 against unmodified PLA and mineral-filled PLA. Test bars were injection molded and conditioned as described above.

Unmodified PLA provides higher tensile modulus but has notched Izod impact of only 2–4 kJ/m² and HDT-B of 55–65 °C. Mineral-filled PLA raises HDT-B to 70–90 °C but increases density to 1.35–1.45 g/cm³ and reduces notched Izod impact to 3–6 kJ/m². VG7264 occupies the intermediate position: density remains below 1.30 g/cm³, notched Izod impact remains above 12 kJ/m², and HDT-B remains above 95 °C. The impact modifier reduces stiffness relative to neat PLA, but the nucleating system offsets heat-resistance loss. This balance is the primary difference from other products in the same poly(lactic acid) family.

When Chain Extension and Nucleation Are Required to Maintain HDT-B Above 100 °C

The high-heat performance of VG7264 depends on the interaction between the nucleating agent and the chain-extension system. At nucleating-agent addition below 0.5 wt%, the crystallization rate is insufficient and HDT-B can fall below 90 °C in sections thinner than 1.5 mm. At addition above 1.5 wt%, excessive crystallinity can reduce notched Izod impact below 8 kJ/m². The manufacturer’s formulation maintains the nucleation package at 0.8–1.2 wt% and the epoxide-functional chain extender at 0.3–0.7 wt%. The chain extender increases melt strength and reduces end-group concentration, but it can also generate premature branching if the melt is held above 240 °C or if amine-based additives are introduced. The use of amine-containing colorants, amine-based flame retardants, or amine-functional coupling agents should be avoided unless specifically pre-qualified by the supplier.

Crystallinity in molded parts can be estimated by differential scanning calorimetry using ISO 11357-3:2018. A crystallinity value of 30–40 % is typical for parts molded at 100 °C mold temperature; values below 25 % indicate insufficient mold temperature or excessive quench. Values above 45 % may indicate over-nucleation or overly long hold times and are associated with embrittlement. The practical conflict is that high crystallinity increases HDT-B but decreases fracture energy; VG7264 is positioned at an intermediate crystallinity that retains notched Izod impact above 12 kJ/m². This trade-off differentiates the product from highly nucleated PLA grades that may exceed 120 °C HDT-B but become brittle.

Glass transition temperature as measured by ISO 11357-2:2020 is 55–60 °C, and the melting endotherm peak is 165–180 °C. These values are broadly similar to unmodified PLA, meaning that the high-heat improvement is not derived from copolymerization but from crystallinity development and impact modification. The chain-extension system also broadens the molecular weight distribution; this raises melt elasticity and reduces die swell variability during extrusion but can increase back pressure in injection molding when the barrel is cold.

Material Handling and Drying Requirements for Hydrolytically Sensitive Polyester Processing

VG7264 is hygroscopic in pellet form. The manufacturer specifies desiccant drying at 80 °C for 4 h with a supply air dew point of −40 °C to −50 °C. Moisture content before melt processing must be below 0.025 % by weight as measured by ISO 15512:2019. Ambient relative humidity above 60 % requires closed hopper or dry-air blanketing; otherwise, pellet moisture can exceed the limit within 30–60 min in an unventilated hopper. Drying above 100 °C is not recommended because pellet surface adhesion and bridging can occur. Regrind may be used up to 20 % by weight for non-critical parts when dried under the same protocol; higher regrind levels reduce notched Izod impact and increase color shift.

Equipment purging is required after processing polyolefins, styrenics, or unmodified PLA. Residual polypropylene in the barrel can form low-adhesion interfaces with PLA and cause delamination in molded parts. A commercial purging compound for engineering thermoplastics at 200 °C is used before shutdown. Production-scale experience indicates that screw torque values should be trended by lot; an increase of more than 15 % at constant barrel temperature signals insufficient drying, excessive regrind fines, or barrel contamination. Mold surfaces are typically textured or polished steel; release is not required for simple geometry but may be used at very low levels because silicone-based mold release can interfere with post-mold adhesion.

For sheet extrusion, a 32:1 L/D single-screw extruder with barrel temperatures 190–210 °C and die temperature 205 °C can be used. Web tension must be controlled to avoid neck-in because melt strength is lower than that of polypropylene. Sheet can be thermoformed at 90–110 °C; the thermoforming mold temperature should be held above 80 °C to minimize post-forming crystallization defects. Coextrusion with other PLA grades is possible when melt streams are matched within 10 °C; incompatible melt temperatures can cause interfacial instability.

Candidate applications for VG7264 include thin-wall electronic enclosures subjected to short-term heat soak at 85 °C in air, hot-fill containers tested for 30 s at 85 °C with no visible deformation, appliance components exposed to 90 °C air for 500 h, and automotive interior clips requiring dimensional stability after 24 h at 90 °C. These applications require validation against the end-user’s OEM standards because the published data for this specific configuration is limited. Compared with unmodified PLA, the grade requires higher mold temperature and longer cooling, increasing cycle time by 30–50 %. Compared with mineral-filled PLA, VG7264 provides lower density, higher impact, and better surface gloss but lower flexural modulus. Compared with petroleum-based engineering thermoplastics such as ABS or polycarbonate, the continuous service temperature under 1.8 MPa load remains lower; VG7264 is not a direct substitute for load-bearing applications above 75 °C.

Low-heat general-purpose PLA grades typically show HDT-B values of 55–65 °C and notched Izod impact of 2–4 kJ/m²; VG7264 increases these values by 35–45 °C and by a factor of 3–5, respectively. High-impact PLA grades without the high-heat package may show notched Izod impact of 15–25 kJ/m² but often show Vicat A50 values near 120–135 °C and HDT-B values near 70–80 °C; VG7264 raises HDT-B by 20–30 °C while retaining impact above 12 kJ/m². Highly nucleated PLA grades can exceed 120 °C HDT-B but typically drop below 5 kJ/m² notched Izod impact. The VG7264 grade therefore addresses the intermediate space: high heat without the brittleness of heavily nucleated PLA, and high impact without the low heat deflection of standard impact-modified PLA.

Regulatory statements should be obtained from the supplier’s safety data sheet and technical data sheet. The product is reported to comply with REACH Regulation (EC) 1907/2006 for substances of very high concern below 0.1 % by weight and with EU RoHS Directive 2011/65/EU Annex II for the restricted heavy metals and brominated flame retardants. Food-contact status is not automatic; migration testing under EU Regulation 10/2011 or FDA 21 CFR 177.1520 is not applicable to PLA and must be replaced by the relevant poly(lactic acid) clearance if intended for food contact. Industrial compostability to EN 13432 or ASTM D6400 is grade- and lot-specific and must be certified for the final part, including pigments and additives. The user is advised to obtain the supplier’s validated processing guide before selecting VG7264 for regulated applications.