ECOPLAN -DURA EN30 Flexible Heat Resistant Microwavable Polylactic Acid is a pelletized polylactic acid compound formulated for injection molding and sheet extrusion of thin-walled, reusable food-contact articles that may be exposed to intermittent microwave reheating. The grade combines a polylactic acid matrix with a dispersed low-glass-transition polyester phase and a nucleating package intended to raise crystallization onset temperature and reduce molded-in amorphous content. Melt volume-flow rate measured in accordance with ISO 1133-1:2022 at 190 °C and 2.16 kg is typically reported in the range of 6 cm³/10 min to 15 cm³/10 min for this product class, placing EN30 in the medium-flow injection molding window. Density determined by ISO 1183-1:2019 is approximately 1.24 g/cm³ to 1.28 g/cm³. Target applications include thin-wall food containers, microwave reheating trays, and lids requiring partial flexural compliance. The producer’s technical datasheet remains the controlling document for exact batch values.

At the molecular level, the flexible phase reduces brittle fracture by introducing shear-yield-dominated deformation in the polylactic acid matrix. Differential scanning calorimetry according to ISO 11357-7:2022 on nucleated polylactic acid compounds of comparable crystallization behavior typically shows a cold crystallization peak near 95 °C to 110 °C and a melt endotherm between 165 °C and 180 °C. The nucleating agent raises isothermal crystallization kinetics; at 110 °C, the crystallization half-time for this compound class is generally below 2 min, whereas unmodified polylactic acid may require more than 10 min. This kinetic shift allows the mold to be held at temperatures between 90 °C and 110 °C without an excessive cycle-time penalty and is the primary structural mechanism behind the heat-resistant designation. However, the flexible phase also lowers modulus relative to rigid polylactic acid and increases elongation at break, which must be considered in snap-fit or load-bearing designs.

What Governs Continuous Use Temperature in EN30 Under Asymmetric Microwave Heating?

Heat distortion temperature and Vicat softening point do not fully capture microwave response, because a 2450 MHz cavity generates non-uniform power absorption driven by food dielectric properties, part wall thickness, and container geometry. For material selection, the relevant short-term heat resistance indicators are ISO 75-2:2013 method B at 0.45 MPa and method A at 1.8 MPa, supplemented by ISO 306:2022 method B50 for Vicat softening. Nucleated polylactic acid compounds with comparable filler-free impact modification typically show an annealed HDT-B between 95 °C and 120 °C, while unannealed specimens often fall between 55 °C and 65 °C. Under method A, the annealed value may range from 75 °C to 90 °C, but this depends strongly on mold temperature, holding time, and post-mold annealing. EN30 is formulated to develop crystallinity in the mold rather than requiring a separate annealing step; nevertheless, maximum heat resistance is achieved only when the article reaches a crystallinity level above approximately 30 % as measured by differential scanning calorimetry. Parts molded against cold tooling at 20 °C to 40 °C may retain a largely amorphous skin and will exhibit lower energy-to-fracture and lower HDT values.

Continuous use temperature should not be read as microwave-safety temperature. A microwave container can experience localized oil or syrup temperatures above 100 °C even when the bulk food is below 80 °C. For that reason, boiling-water immersion, hot-oil simulant tests, or short-chain triglyceride simulants are used to evaluate distortion, not the nominal continuous use temperature printed on a conventional thermoplastic datasheet. EN30 should be subjected to a system-level test under the intended microwave wattage and food simulant, because published data for this specific configuration is limited.

On a 40:1 L/D co-rotating twin-screw extruder with vacuum venting at barrel 9, EN30 is typically compounded at a screw speed of 250 rpm to 400 rpm and a melt temperature of 180 °C to 200 °C. The modifier phase is added downstream after the polylactic acid melt seal to limit thermal exposure, while the nucleating masterbatch is metered at the main feed throat. In injection molding, a reverse temperature profile from 190 °C at the rear zone to 180 °C at the nozzle is used to reduce shear heating and prevent molecular weight loss. The recommended mold temperature of 90 °C to 110 °C requires a mold-temperature control unit capable of sustained operation near the upper end of a standard water system; pressurized water or oil heating is preferred because the crystallization rate falls sharply below 85 °C. Clamp force should be calculated on the basis of 0.4 tonnes/cm² to 0.6 tonnes/cm² of projected area for thin-wall parts.

For thin-wall tooling, the screw should use a low-compression ratio, typically between 2.0:1 and 2.5:1, with a non-return valve clearance no greater than 0.05 mm to avoid dead-spot degradation. Back pressure is maintained between 5 bar and 15 bar; higher back pressure raises melt temperature and accelerates hydrolysis. Short-shot trials are run with a cushion of 3 mm to 6 mm and a fill speed of 30 mm/s to 80 mm/s. Table 2 provides a starting process window for injection molding.

Mechanical Response Across Conditioned and Unconditioned States

Tensile properties of flexible heat-resistant polylactic acid are strongly influenced by conditioning and crystallinity. Under ISO 527-2:2012, conditioned specimens tested at 23 °C and 50 % relative humidity typically show a tensile yield stress between 35 MPa and 50 MPa and an elongation at break between 50 % and 150 %, which represents a substantial departure from unmodified polylactic acid grades that often fail below 5 % elongation. Flexural modulus measured by ISO 178:2019 is generally in the range of 1800 MPa to 2600 MPa, while notched Izod impact according to ISO 180:2019 method A falls between 6 kJ/m² and 20 kJ/m². The property range is intentionally broad because the final values depend on mold temperature, wall thickness, and the degree of crystallinity. Table 1 summarizes representative comparative data for the EN30 product class against unmodified polylactic acid.

After mechanical testing, moisture conditioning is not a cosmetic step. Polylactic acid absorbs water slowly, but molded parts stored at 85 % relative humidity for 7 days can show a measurable reduction in tensile yield stress and an increase in elongation at break due to plasticization. For comparative data, specimens should be conditioned according to ISO 291:2008 class 2 at 23 °C and 50 % relative humidity for a minimum of 88 h. This conditioning requirement is especially important for EN30 because the dispersed elastomer phase has different moisture uptake kinetics than the polylactic acid matrix, and the interphase region can act as a low-energy crack path if the part is tested dry.

When EN30 Replaces Unmodified PLA in Thin-Wall Injection Molding

Replacing unmodified polylactic acid with EN30 in an existing thin-wall tool requires adjustment of the thermal cycle rather than a simple material swap. The mold must be run hot enough to crystallize the nucleated matrix; otherwise the part can exhibit sink marks, post-demolding expansion, and variable microwave distortion. Mold temperature is the dominant variable, and the practical processing window is narrow: crystallization rate drops sharply below 85 °C, while excessively high mold temperatures above 115 °C increase cycle time and may cause the flexible phase to remain mobile during ejection. Ejector pins should be arranged to avoid localized deformation; a draft angle of at least 1° is recommended for textured surfaces. Shrinkage in the flow direction is typically 0.4 % to 0.8 %, compared with 0.3 % to 0.5 % for unmodified polylactic acid, and transverse shrinkage may be lower because the nucleating agent promotes more uniform crystallization. These values should be verified with mold-flow simulation using measured pvT and crystallization kinetics data.

Because the flexible phase reduces melt stiffness, hot-runner and gating modifications may be required. Capillary rheometry data at 190 °C and an apparent shear rate of 1000 s⁻¹ for this product class indicate a shear viscosity between 50 Pa·s and 120 Pa·s, but the extensional viscosity in the gate region may be higher due to the elastomer phase. Gate diameters should be increased by 10 % to 20 % relative to unmodified polylactic acid to reduce jetting and gate freeze-off. Valve-gated hot runners should be profiled with a short hold time after gate seal to prevent stringing. Initial trials should include a design of experiments across melt temperature, mold temperature, and hold pressure rather than single-point sampling.

For material-level testing, microwave suitability is evaluated through dielectric properties and article-level exposure. At 2450 MHz, polylactic acid-based compounds generally have a low dissipation factor, meaning the container wall itself absorbs little microwave energy and heating occurs primarily through conduction from the food. At the article level, the test sequence includes repeated exposure in a 2450 MHz domestic microwave oven at 800 W to 1000 W for 3 min to 5 min with water, 3 % acetic acid, and 10 % ethanol as food simulants, followed by visual inspection, dimensional checks, and migration testing if the article is intended for food contact. Commission Regulation (EU) No 10/2011 sets an overall migration limit of 10 mg/dm² for plastic materials and articles in contact with food; specific migration limits for additives used in the EN30 formulation must be confirmed from the producer’s Declaration of Compliance. Under the RoHS Directive 2011/65/EU Annex II, the compound is formulated to meet the homogeneous material thresholds for lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE, subject to final article verification.

Compared with unmodified polylactic acid, the principal difference in EN30 is the combination of flexibility and heat resistance. Unmodified polylactic acid is inherently brittle, with elongation at break below 5 % and HDT-B below 60 °C unless annealed, and it tends to warp during hot filling or microwave reheating. Impact-modified polylactic acid grades based on high rubber content can achieve elongation above 200 % but often lose heat resistance because the soft phase reduces modulus and promotes cold flow under load. EN30 uses a lower-modulus polyester phase with a nucleated polylactic acid matrix to maintain HDT-B above 95 °C after molding while still providing ductile failure. This distinguishes the grade from polylactic acid/poly(butylene adipate-co-terephthalate) blends, which are flexible but generally exhibit lower HDT and higher creep, and from mineral-filled rigid polylactic acid grades, which can have high HDT but low toughness. The grade is not intended as a barrier material; oxygen transmission rate is higher than that of polyethylene terephthalate or multilayer structures, and it is not recommended for long-term frozen-food packaging where moisture vapor transmission must remain below 1 g/m²/day.

Before processing, drying and moisture control remain the primary constraints for EN30. Polylactic acid is hydrolysis-sensitive at processing temperatures, and the ester linkages in the flexible phase can also undergo chain scission if wet material is fed to the screw. The material should be dried in a desiccant dryer with a supply air dew point of -40 °C or lower at 80 °C for 4 h to 6 h, until the residual moisture content by ISO 15512:2019 is below 250 ppm. Drying time should not exceed 8 h unless the dryer is equipped with temperature and humidity logging, because prolonged exposure can cause pellet surface sticking and bridging in the hopper. Wet-material processing is typically indicated by silver streaks, reduced melt strength, and a drop in melt viscosity measured by ISO 1133-1:2022. Regrind can be used at levels up to 20 % by weight if the regrind is dry and free of contamination, but repeated thermal cycles increase the acid value and reduce the notched Izod impact; each additional heat history should be validated against the original mechanical property specification.

At the operational boundary, EN30 is limited by the combination of temperature, moisture, and shear. Continuous exposure to air temperatures above 80 °C in the amorphous state may cause progressive distortion and should be avoided unless the part has been crystallized to the target degree. The grade is not recommended for food-contact use with high-acid or high-alcohol contents above 40 % ethanol without specific migration testing, because the flexible phase may alter partitioning behavior. The material should not be compounded with amine-based additives or polyamide-based masterbatches, as aminolysis can accelerate chain scission and reduce molecular weight. The grade should not be exposed to boiling water for more than 30 min unless the part geometry and crystallinity have been validated, and it is not a replacement for polypropylene in retort or pressure-cooker applications. Published data for this specific configuration is limited; therefore, end-use qualification remains the responsibility of the converter and brand owner.