Ingeo Polylactic Acid (PLA) 1102 is a semi-crystalline thermoplastic polyester supplied by NatureWorks LLC for injection molding applications. The product designation 1102 identifies a melt-flow grade in the Ingeo portfolio that is polymerized from lactide obtained from plant carbohydrate fermentation. The lactide monomer is ring-opened with controlled stereo-isomer content; residual D-lactide units disrupt long-range order in poly(L-lactide), limiting spherulite growth and preserving optical clarity after rapid mold cooling. The resin is supplied as cylindrical pellets with a density of 1.24 g/cm³ when measured to ISO 1183-1:2019. Typical values from the manufacturer’s published data include a melt mass-flow rate of 14–20 g/10 min at 210 °C under a 2.16 kg piston load to ISO 1133-1:2022, tensile yield stress of 55–60 MPa and tensile modulus of 3.2–3.6 GPa to ASTM D638-14, elongation at break of 2.5–5.0%, notched Izod impact of 14–18 J/m to ASTM D256-10e1, and heat deflection temperature under 0.45 MPa load of 50–56 °C to ISO 75-2:2013. These values are representative for injection-molded test specimens; batch certificates should be consulted for critical dimensions and safety factors.

When does residual moisture become a processing boundary?

Injection molding of Ingeo 1102 requires closed-loop desiccant drying because the ester linkages undergo hydrolytic chain scission in the melt. Typical dryer conditions are 80 °C for 4–6 h with supply-air dew point below -30 °C and airflow above 3.5 m³/h per kg resin inventory. The target pellet moisture before plastication is below 250 ppm; at 400 ppm or higher, production equipment typically records falling melt pressure, shortened screw recovery time, splay, silver streaks, and a measurable loss of tensile elongation. Hydrolysis produces lactic acid oligomers and carboxylic acid end groups that autocatalyze further hydrolysis, so feedstock moisture cannot be tolerated as a minor variable. On lines without dry-air hopper purge, ambient humidity above 60% RH can raise surface moisture in 20–30 min and reverse drying. Pellet surface temperature above 55 °C may generate tack and hopper bridging; therefore hopper residence after drying should remain below 15 min unless the hopper is continuously purged with dry air. In hot, humid plants the preferred configuration is a drying hopper mounted directly above the feed throat with an automatic vacuum loader.

Capillary rheometry at 210 °C shows shear-thinning behavior with a power-law index of 0.5–0.7 over the injection molding shear range. Apparent viscosity falls from approximately 200–500 Pa·s at 100 s⁻¹ to 40–90 Pa·s at 1000 s⁻¹. The melt is more shear-sensitive than a general-purpose polypropylene of comparable melt-flow index, which means gate and runner sizing must be larger to prevent excessive pressure drop. At the same time, temperature sensitivity is steep: raising melt temperature from 190 °C to 210 °C can reduce fill pressure by 10–15% while narrowing the degradation margin. The practical operating window is bounded by poor molding at approximately 190 °C and thermal degradation above 220 °C; this 30 °C window is narrower than that of many styrenic and olefinic compounds.

Barrel zone set points from rear to nozzle are commonly 170–180 °C, 180–190 °C, 190–200 °C, and 195–210 °C for screws with 18:1–22:1 L/D and compression ratios of 2.0:1–2.5:1. Melt temperature should remain below 220 °C for cycles longer than 5 min; higher temperatures accelerate lactide reformation, discoloration, and molecular weight loss. Mold temperature of 25–35 °C produces a clear, low-haze surface and stable ejection below 45 °C. Hot-runner systems should use open-pipe or internally heated manifolds with no dead spots; residence zones above 10 min at 210 °C produce yellowing and viscosity variation. Injection speed is set to generate a fill time of 0.3–1.0 s for wall thicknesses below 1 mm, with a cushion of 3–5 mm and decompression of 1–2 mm to limit drool. Clamp-force prediction follows amorphous PET-like flow lengths; gates of 0.8–1.5 mm thickness are suitable for short-flow parts. A reverse-taper nozzle or shut-off nozzle is preferred because PLA has low melt strength and can drool from a standard open nozzle.

Mechanical property envelope and test methodology

Above 55–60 °C, the modulus declines sharply because the amorphous fraction passes through the glass transition. As-molded Ingeo 1102 parts are usually transparent because rapid mold cooling suppresses crystallization; haze measured on 3 mm plaques to ASTM D1003-13 is typically below 2% when mold temperature is held at 35 °C. Dimensional stability under load beyond 60 °C is not equivalent to polypropylene or ABS. Parts intended for dishwasher or hot-fill exposure require annealing at 80–100 °C for 15–30 min in forced-air tooling fixtures to develop crystallinity; annealed heat deflection can rise toward 90–100 °C under 0.45 MPa, while notched impact decreases. Published data for this specific grade’s maximum achievable crystallinity and post-anneal impact retention are limited; validation should include post-anneal dimensional checks and drop-impact testing on the production tool.

Post-mold shrinkage is anisotropic and moisture-dependent. Amorphous parts typically exhibit 0.3–0.5% linear shrinkage after 24 h at 23 °C and 50% RH, but dimensions can continue to drift with aging and humidity uptake. Unopened bags should be stored below 40 °C and protected from ultraviolet exposure. Once opened, the material should be consumed within 8 h in an uncontrolled environment or kept under dry-air purge to prevent moisture regain. Gate blush from excessive injection velocity, splay from moisture, and yellowing from long hot-runner residence are commonly observed production failures; reducing gate shear heating or purging after 15 min hold can restore part quality.

Which applications expose the viscosity advantage over lower-flow PLA grades?

Thin-wall cutlery, caps, closures, compact cosmetic packaging, and multi-cavity consumer goods represent primary uses. In 8–16-cavity cold-runner tools with wall thickness below 1 mm, the elevated melt-flow range reduces short-shot frequency compared with extrusion grades having melt-flow rates of 6–8 g/10 min. Peak injection pressure at equivalent fill speed is typically 15–25% lower, allowing a smaller clamp force reserve; however weld-line strength and notched impact are lower than those of ductile amorphous styrenics or polycarbonate blends. The resin is inappropriate for structural components requiring high-speed ductile failure, for continuous service above 55 °C, or for environments with repeated hot water unless annealed.

Compared with a general-purpose polypropylene, Ingeo 1102 has higher flexural modulus and surface hardness but lower elongation at break, lower tear resistance, and higher density. It also requires stricter drying and narrower barrel-temperature control. Relative to lower-flow PLA extrusion grades, Ingeo 1102 has lower melt viscosity but also lower melt strength and lower sag resistance; it is not suited to sheet extrusion or deep-draw thermoforming where a self-supporting melt curtain is required. Relative to high-heat PLA grades containing talc or nucleating packages, 1102 lacks intrinsic heat resistance; its heat deflection temperature under 0.45 MPa is 50–56 °C, whereas filled and nucleated PLA grades can reach 80–100 °C under the same condition. Compared with polyolefins, PLA also has a narrower drying and melt-temperature window, and equipment dead spots that are tolerable for polypropylene can generate visible yellowing and viscosity drift with PLA.

Color masterbatches based on polyethylene or polystyrene carriers can cause delamination in thin-wall parts; PLA-based carriers with similar melt viscosity are required. Recycled PLA flake containing polylactic acid of unknown D-lactide content can alter crystallization rate and optical clarity. If post-industrial regrind is used above 20 wt%, the blend should be re-dried and the melt flow index verified to ISO 1133-1:2022 before start-up. In high-shear hot-runner systems, melt residence time and temperature should be logged because sub-optimal conditions create lot-to-lot viscosity drift that affects cushion consistency and part weight. Published spiral-flow length data for this exact grade are limited; mold-filling predictions should be confirmed on the production tool with short-shot studies before commissioning multi-cavity tooling.

Food-contact documentation and migration limits

Food-contact status is grade-specific and must be confirmed through the supplier’s current regulatory letter. In the European Union, compliance is assessed under EU Regulation (EC) No 10/2011 with overall migration limit 10 mg/dm² for general food contact; testing is typically performed with simulants such as 3% w/v acetic acid, 10% v/v ethanol, and vegetable oil according to EN 1186-1:2002. In the United States, suitable food-contact use is covered by applicable food additive regulations or food-contact notifications; users should request the current FDA statement for the exact grade rather than transferring clearance from other PLA grades. Lactic acid monomer is permitted as a food additive under FDA 21 CFR 184.1061 and Commission Regulation (EU) No 231/2012, but finished-article compliance depends on colorants, masterbatch carriers, nucleating agents, and conversion aids. For REACH and RoHS declarations, the relevant documentation should reference EC No 1907/2006 and Directive 2011/65/EU as amended.

Incompatible additives include amine-based chain extenders and some unneutralized metal stearates, which can catalyze transesterification or hydrolysis; these should be avoided unless specifically validated in a dried melt stream. Peroxide masterbatches should be avoided at levels above 0.05 wt% unless viscosity control is intended and validated. The neat resin is generally free of bisphenol A, phthalate plasticizers, and halogenated flame retardants at typical formulation. The processing window remains the primary operational constraint: moisture, melt temperature, shear residence time, and mold temperature interact to determine molecular weight retention, optical quality, and part compliance.