INZEA M23 is a flexible low-modulus film extrusion grade within the INZEA family of polylactic acid-based compounds produced by NUREL Engineering Polymers. The grade is supplied in cylindrical pellet form for blown film and cast film converters that require a compostable film with higher elongation at break than unmodified rigid PLA. Compared with standard PLA film grades, the low-modulus formulation lowers secant modulus, raises tear propagation resistance, and modifies the heat seal initiation threshold while retaining the poly(lactic acid) backbone necessary for industrial compostability. The material is typically specified through melt mass-flow rate, tensile modulus, elongation at break, Elmendorf tear strength, heat seal initiation, haze, and gauge-dependent dart impact. Because datasheet values are batch-dependent and may be revised, the data presented below are class representative for flexible low-modulus PLA film grades unless a specific manufacturer value is referenced. Procurement for INZEA M23 should always be made against the current certificate of analysis and technical datasheet supplied by the producer. The designation separates the grade from rigid injection-molding PLA and from higher-elongation PBAT-rich film compounds.

Because PLA-based film compounds hydrolyze at melt-processing temperatures, residual moisture is the first control variable. Extrusion trials have recorded lactic acid oligomer deposits at die lips when hopper moisture exceeds 250 ppm. Desiccant drying at 60 °C to 80 °C for 4 h to 6 h at a dew point of -40 °C or lower is standard before film conversion. Above 60% RH, sealed hopper loading and dried-air conveying are required to prevent moisture regain. The melt temperature window for blown film is usually 150 °C to 175 °C; die-head temperatures above 180 °C can initiate chain scission and generate deposits. Manufacturers of flexible PLA compounds commonly recommend a reverse barrel profile, with the feed zone 10 °C to 15 °C below the metering zone, and a melt pump to stabilize die pressure. Published data for this specific INZEA M23 configuration are limited, but the above ranges are consistent with converter practice for the flexible low-modulus PLA class.

Incoming material control should include melt mass-flow rate by ISO 1133-1:2022 at 190 °C and 2.16 kg, moisture by coulometric Karl Fischer titration, density by ISO 1183, and pellet yellowness index. A shift in melt mass-flow rate of more than 1 g/10 min can correspond to changes in bubble stability and seal initiation; batches with identical MFR but different moisture can still show gauge variation at thicknesses below 25 µm. The most robust incoming QC protocol combines moisture analysis, MFR, and a small-scale blown film trial on a 25 mm single-screw line with a 50 mm die before production-scale release.

What Limits Melt Strength and Bubble Stability in Blown Film Conversion?

Blown film conversion of INZEA M23 is constrained by the same melt strength limitations observed in low-modulus PLA compounds. The bubble is typically run at a blow-up ratio of 2.0 to 3.0 and a frost line height 2 to 6 die diameters above the air ring. Die gaps are generally set between 0.8 mm and 1.2 mm. Single-screw extruders with L/D ratio 25:1 to 30:1 and compression ratios 2.5:1 to 3.0:1 are recommended; high-shear screw designs developed for rigid PLA produce excessive viscous dissipation, leading to local melt-temperature excursions and gel formation. Low melt strength also limits stalk height and makes the process sensitive to air-ring turbulence. Oscillations in frost line position often correlate with hopper moisture variation rather than screw speed. Production-scale converters using dual-lip air rings and internal bubble cooling have reported improved gauge uniformity at thicknesses below 25 µm; however, retrofitting internal bubble cooling requires die head modifications that may not be justified for short runs.

Melt pump pressure control is particularly important because low-modulus PLA does not tolerate long melt residence time at high shear. A pressure fluctuation of more than 5 bar at the die can generate visible gauge bands and alter orientation. The recommended melt pressure at the screen changer is generally 80 bar to 150 bar depending on output, die diameter, and melt temperature. Filtration with screen packs of 100 µm to 150 µm is common to remove carbonized gels. Processors that bypass melt filtration to raise output often report higher bubble breaks and more die-lip buildup.

Mechanical and Seal Property Differentiation Across Rigid PLA, INZEA M23, and PBAT-Based Film

Selection among compostable film polymers depends on competing requirements of bio-based carbon content, elongation, tear resistance, and seal initiation. Rigid PLA films provide high modulus but exhibit low elongation and limited abuse resistance; PBAT-rich films provide high elongation and low seal initiation but often reduce stiffness and bio-based carbon content. Flexible low-modulus PLA film grades such as INZEA M23 are positioned as an intermediate. The comparative envelope below is drawn from published technical bulletins, converter trials, and standardized test data. It is not a guaranteed specification for INZEA M23 and should be verified against the current manufacturer datasheet.

In form-fill-seal conversion of low-modulus PLA film, seal initiation temperature is a critical threshold. The lower seal initiation of INZEA M23 relative to rigid PLA permits shorter dwell times on vertical packaging lines, but the seal plateau is narrower than that of PBAT-rich films. Seal strength at 100 °C and 0.8 N/mm² jaw pressure may be adequate for lightweight produce bags, while heavy organic waste bags require seal strength above 8 N/15 mm per ASTM F88. Because low-modulus PLA has a sharper seal strength curve, jaw temperature variation above ±5 °C can produce either weak seals or tearing at the seal interface. Hot-tack strength by ASTM F1921 Method B is often more important than cold seal strength for vertical form-fill-seal lines running above 40 cycles/min; the hot-tack plateau of flexible PLA films is typically narrower than PBAT-rich films. A jaw temperature range of 5 °C to 10 °C is common for acceptable hot-tack; wider sealing windows require coextrusion with a PBAT-rich skin. Processors have observed that adding antiblock masterbatch at 5 wt% to 15 wt% shifts slip and seal behavior; therefore, additive loading must be validated by seal-strength and hot-tack testing on the target packaging machine.

For cast film lines, the lower modulus of INZEA M23 reduces orientation stress on chill rolls and allows thinner gauge capability than rigid PLA. However, the same low modulus creates higher roll-blocking tendency, especially when film is wound at temperatures above 30 °C. Chill-roll temperatures are typically held at 15 °C to 25 °C, and winding tension is controlled below 15% of the machine-direction yield stress. Slip and antiblock additives are commonly dosed at 1 wt% to 3 wt% in flexible PLA film to reduce blocking; overloaded slip can migrate to the surface and compromise corona treatment retention.

When Tear Resistance and Puncture Energy Are Evaluated on Flexible PLA Film Lines

Elmendorf tear strength by ISO 6383-2 and puncture resistance by the slow puncture method of ASTM D5748 are more informative than tensile elongation alone for low-modulus PLA film. In flexible PLA film, orientation direction controls tear anisotropy: machine-direction tear strength is generally lower than transverse-direction tear strength because of molecular orientation produced during bubble drawing. A fully unmodified PLA film may exhibit MD tear below 10 N/mm, while flexible low-modulus grades are typically specified in the 20 N/mm to 60 N/mm range. However, MD tear values vary with gauge, draw-down ratio, and plasticizer or elongation suppressant content. Puncture energy at rupture, measured with a 19 mm diameter probe and 250 mm/min crosshead speed, often distinguishes films that survive automated bagging systems from those that fail at the loading station. Published data for INZEA M23 in heavy-gauge organic waste applications are limited; converters should generate machine-specific puncture data at the intended thickness rather than extrapolating from thin-film tensile results.

Dart impact by ASTM D1709 Method A is useful for comparing lot-to-lot variability, but the test is thickness-dependent. At 25 µm, flexible low-modulus PLA films commonly show F50 values of 100 g to 250 g; at 50 µm, F50 values may exceed 300 g. Producers should not use dart impact as a surrogate for slow puncture in heavy-gauge applications because the failure mechanism in a falling-dart event is strain-rate-dependent and may not correlate with slow puncture at seam-failure locations.

Because flexible low-modulus PLA has reduced Vicat softening temperature, it is not suitable for hot-fill packaging above 60 °C. Vicat softening temperature by ISO 306 Method A50 is typically below 60 °C for the class, and heat seal strength should be measured below the Vicat point to avoid film deformation during jaw contact. For applications requiring hot-fill or pasteurization, a higher-HDT PLA structural layer or non-PLA polymer system is required. The low thermal resistance also affects sheet extrusion: cooling rolls must be set at 15 °C to 25 °C, and the sheet must be fully crystalline or fully amorphous depending on downstream thermoforming conditions; partially crystallized sheet can exhibit dimensional instability during reheating.

When used as a sealant web in coextruded films, INZEA M23 is typically paired with a structural PLA layer or a PBAT-rich skin to balance stiffness and seal performance. In these structures, the tie-layer chemistry must avoid amine-functional additives because residual amines accelerate PLA chain scission and can cause brittle failure at the interface. The lower hardness of flexible PLA film also affects slitting and winding: razor-blade slitting at blade tension above 1.5 N/mm can generate microcracks that later propagate in bag-opening force tests. Winding tension should be kept below 15% of the film’s yield strength in the machine direction, and inline corona treatment is often set to 38 mN/m to 42 mN/m for water-based flexo inks. Without primer, the corona-treated surface may lose 4 mN/m to 6 mN/m within 72 h, so printing should be scheduled within the measured wetting envelope.

Haze of flexible PLA film depends on crystallinity, surface texture, and additive loading. For clear films, haze below 5% per ASTM D1003 is attainable at thicknesses below 35 µm with low-antiblock formulations and controlled chill-roll temperature; heavier antiblock loadings for automatic bag lines can raise haze above 10%. Gloss at 60° by ASTM D2457 is typically lower than rigid PLA film because the plasticized or blended phase scatters light at film surfaces.

Controlling Gauge Uniformity in Thin Flexible PLA Film

Gauge uniformity at thicknesses below 20 µm is controlled less by melt temperature and more by die gap, air ring velocity, and bubble geometry. A high-velocity dual-lip air ring set to 20 m/s to 30 m/s can stabilize a low-melt-strength bubble but may also produce edge-to-center gauge variation if the frost line is too low. Automatic gauge control using capacitive thickness sensors closes the loop by adjusting die temperature zones; on a 100 mm die with 4 to 8 thermal zones, a gauge error of ±2 µm is common for flexible PLA. Beyond ±2 µm, the film can show weak spots in puncture and seal tests, especially at the transition between the main bubble body and the crease. Processors should map the bubble circumference with a stationary thickness gauge and record the frost line temperature using an infrared pyrometer to separate air-ring variations from die-gauge defects.

Compostability certification of INZEA M23 under EN 13432:2000 or ASTM D6400 is a materials-level certification and does not automatically extend to the final film article. Disintegration testing under EN ISO 20200 or ISO 16929, ecotoxicity assessment according to OECD 208, and heavy-metal analysis by the relevant EN 13432 annexes are required for final article certification. The product is covered under the EU REACH regulation 1907/2006; for food-contact uses, compliance must be demonstrated under Regulation (EU) No 10/2011 or an applicable FDA food-contact notification for the finished structure, because migration of low-molecular-weight esters and plasticizers is both time- and temperature-dependent. Converters should request the manufacturer’s migration data for the specific gauge and sealing conditions.

For thermoformed trays made from INZEA M23 sheet, the low modulus allows deeper draw ratios than rigid PLA at lower sheet temperatures. Plug-assisted thermoforming with plug temperature 60 °C to 80 °C and mold temperature 20 °C to 30 °C can produce draw ratios up to 1.5:1 in shallow trays; published data for deep-draw configurations are limited. However, the same low modulus reduces top-load strength, so vertical walls require ribbing or a higher-molecular-weight PLA support layer. Secondary operations such as ultrasonic welding show narrower amplitude windows than rigid PLA; a starting amplitude of 20 µm to 30 µm at 20 kHz is common, but bond strength must be validated on the actual welder.