Bionolle Starcla™ 10S is a 40% bio-based compound in which polylactic acid (PLA) and starch are melt-compounded into a rigid, compostable material intended for injection molding, sheet extrusion, and thermoforming. The bio-based carbon figure is expressed as the fraction of renewable organic carbon relative to total organic carbon and is determined by ASTM D6866-22 Method B or EN 16640:2017; it is not the starch weight fraction. The grade combines the stiffness of PLA with the renewable-carbon contribution and rapid disintegration behavior of starch, but introduces moisture sensitivity and thermal processing limits not observed in unfilled PLA. Under industrial composting conditions, the compound is engineered to meet the permeability and disintegration thresholds of EN 13432:2000 and ASTM D6400-21: at least 90% disintegration on a 2 mm sieve after 12 weeks, at least 90% biodegradation relative to cellulose within 180 days under ISO 14855-1:2012 or ASTM D5338-15, and no adverse ecotoxicological response in the resulting compost. Exact lot-specific melt flow index, tensile, flexural, and impact values are provided on the manufacturer’s certificate of analysis and should be used for tooling calculations rather than generic compound-class data.

Why must moisture control be tighter for Starcla™ 10S than for unfilled PLA?

Starch contributes hydrophilic hydroxyl groups that raise equilibrium moisture uptake and increase the risk of hydrolysis-induced molecular weight loss in the PLA phase during melt processing. Drying is therefore a mandatory step rather than a secondary recommendation. The material should be dried in a desiccant dryer with a dew point of −40°C or lower, hopper inlet air temperature of 70°C to 80°C, and residence time of 3 h to 4 h. A target residual moisture of 250 ppm or less should be verified by ISO 15512:2019 or ASTM D6980-17 before melt processing. Hot-air ovens are not recommended because they can dry the pellet surface while trapping moisture at the pellet core, producing gas blistering and splay in molded parts.

Melt temperatures should be kept within 165°C to 190°C; excursions above 200°C accelerate starch discoloration and PLA random chain scission. Residence time at melt temperature should be minimized, typically below 8 min, and barrel zones should be profiled so that the feed throat remains below 40°C to prevent bridging. Processing with amine-based additives or polyvinyl alcohol-based purge compounds should be avoided; these materials can alter pH or hydrogen-bonding behavior in the starch phase and lead to inconsistent melt pressure or odor generation. Production-scale single-screw extruders with L/D ratios from 24:1 to 30:1 and compression ratios from 2.5:1 to 3.0:1 are suitable; twin-screw lines should use moderate shear configurations and avoid excessive kneading-block intensity after the starch feed point.

For rigid packaging and food-service tooling, mechanical property comparisons should be made on test specimens conditioned at 23°C ± 2°C and 50% ± 5% relative humidity for at least 40 h according to ISO 291:2008. Representative property ranges for PLA/starch compounds in the 40% bio-based loading class are shown in the following table; they are not guaranteed product specifications and must be confirmed against the manufacturer’s certificate of analysis.

The data indicate a rigid, low-elongation material. The low notched Izod values mean that thin-wall parts should use generous radii and avoid sharp corners; impact modifiers may be added in masterbatch form only after compatibility testing because some elastomeric additives reduce compostability or increase heavy-metal loading. The heat deflection temperature is low enough that articles should not be exposed to temperatures above 45°C under continuous mechanical load unless annealing or post-crystallization is evaluated.

When compostability certification dictates grade selection for food-contact and food-service articles

Compostability certification for Starcla™ 10S is not a single test result but a matrix of endpoints covering biodegradation, disintegration, ecotoxicity, and regulated metals. The following table summarizes the typical certification endpoints that apply to this compound class.

Food-contact approval is not automatically conferred by compostability certification. Finished articles intended for food contact must be assessed under EU 10/2011 using the appropriate food simulants, and for the United States under applicable FDA 21 CFR sections. A starch/PLA compound is not automatically covered by 21 CFR 177.1520, which applies to olefin polymers; therefore end-use clearance must be established for the specific article, food type, contact time, and temperature. Migration testing should include the intended food simulants and conditions. Published data for this specific configuration is limited and should not be substituted for a compliant migration study.

Compared with polybutylene adipate terephthalate/starch blends, Starcla™ 10S exhibits a higher tensile modulus and lower elongation at break, making it more appropriate for rigid cutlery, trays, and caps than for flexible films. The starch phase reduces light transmission and increases water vapor affinity relative to unfilled PLA, so transparent packaging with low haze requires an unfilled PLA grade or a clarified PLA compound. Differences from other Bionolle grades should be confirmed by side-by-side injection molding trials on the intended tool. In sheet extrusion, the polishing roll stack should be set at 20°C to 40°C to reduce blocking; edge trim can be reground at up to 20% by weight if dried with virgin material. Regrind ratios above 20% may increase variability in melt flow and should be validated for each lot.

When the 40% bio-based carbon value is reported under ASTM D6866 and EN 16640

The 40% bio-based content claim is a renewable-carbon measurement rather than a starch percentage. ASTM D6866-22 Method B uses accelerator mass spectrometry to measure the radiocarbon-14 signal of the material and compares it to a modern reference standard; EN 16640:2017 reports bio-based carbon content using a similar radiocarbon approach. The value can differ from bio-based mass content because carbon is not distributed equally among polymer repeat units and organic additives. For this reason, the product data sheet should be checked for the exact reporting basis. If a purchaser needs a starch weight fraction for supply-chain documentation, it must be requested separately from the manufacturer.