Soarnol A4412B

On coextruded rigid sheet lines producing PP-based barrier trays for protein and prepared-food applications, Soarnol A4412B is carried as the core layer in a five-layer skin/adhesive/EVOH/adhesive/skin configuration. The 44 mol% ethylene comonomer fraction lowers the crystalline melting point to a typical range of 164–168 °C and reduces melt viscosity relative to lower-ethylene EVOH grades, which permits coextrusion with polypropylene at melt temperatures of 210–240 °C without destabilising the interfacial layer. The practical processing window is nevertheless bounded by two thermally activated failure modes: at melt temperatures above 245 °C or residence times beyond 20 min, residual catalyst residues from maleic anhydride-grafted tie resins can accelerate gel formation, producing fisheyes and local barrier defects; at moisture contents above 0.2 wt%, the vinyl alcohol mer units can undergo hydrolysis and oxidative chain scission, causing interlayer viscosity mismatch and melt fracture. Desiccant hopper drying at 80 °C for 4–6 h is used on production lines to bring pellet moisture below 0.2%, and feed throat nitrogen blanketing is applied where ambient relative humidity exceeds 60%. For a 600–800 µm sheet containing a 12–18 µm EVOH core, the oxygen transmission rate measured by ASTM D3985 at 23 °C, 0% relative humidity typically falls between 0.3 and 1.0 cm³/(m²·day·atm); the same sheet measured under ASTM F1927 at 23 °C, 90% relative humidity can show values above 5.0 cm³/(m²·day·atm), which is why moisture-absorbing polyolefin skins and process mineral fillers are specified for high-humidity fill conditions. The grade is covered for direct food contact under 21 CFR 177.1360 and EU Regulation 10/2011, Annex I, Table 1, FCM No 1574, with end-article migration testing conducted to EN 1186-1 and overall migration limits of 10 mg/dm².

How Does Relative Humidity Shift Oxygen Transmission in Seven-Layer MAP Film?

In seven-layer blown film for modified-atmosphere packaging of processed meat and cheese, Soarnol A4412B is buried between tie layers and polyolefin or polyamide skins. The oxygen permeation coefficient at 23 °C, 0% RH is commonly reported between 0.3 and 0.6 cm³·20 µm/(m²·day·atm) under ISO 15105-2, while the same film conditioned at 65% RH shows two-to-fivefold higher transmission, and at 90% RH the value moves into the 4.0–8.0 range. This nonlinear humidity response drives layer design: the EVOH layer is placed behind a 20–40 µm food-side polyethylene or polypropylene layer so that water vapour sorption at the EVOH interface is delayed during the package shelf life. In films for high-water-activity products, a polyamide layer is coextruded adjacent to the EVOH or combined with desiccant masterbatch in the adhesive, because nylon lowers moisture activity at the EVOH boundary. Extrusion conditions on a 55 mm barrier screw with 30:1 L/D and Maddock mixing section are maintained at 210–225 °C melt temperature and 40–80 bar melt pressure; die gap is typically 1.6–2.2 mm, blow-up ratio 2.0–2.8, and frost-line height 600–900 mm. Excessive melt temperature above 230 °C reduces optical clarity at the nylon/EVOH interface, while insufficient temperature produces wavy edge encapsulation. The table below summarises published oxygen permeability ranges for 44 mol% ethylene vinyl alcohol copolymer films at three relative-humidity conditions.

When multilayer HDPE food bottles are produced by coextrusion blow moulding for soy sauce, ketchup and edible oil, Soarnol A4412B enters the structure through a six-layer die head producing HDPE/regrind/tie/EVOH/tie/HDPE. The EVOH layer is usually limited to 1.5–3.5 wt% of the total wall thickness because higher percentages increase scrap viscosity mismatch, create regrind-layer gel accumulation at the die lip, and reduce bottle impact strength. The melt flow rate of 12 g/10 min at 210 °C, 2160 g under ISO 1133-1 positions the grade within the shear viscosity envelope of blow-moulding HDPE, but interfacial shear stress in the die must be kept below the threshold where sharkskin initiates on the EVOH layer; this threshold is commonly controlled by designing the die land temperature at 200–220 °C and by limiting the EVOH extruder screw speed to avoid barrel residence time beyond 15 min. Parison programming is used to compensate for melt strength differences between HDPE and EVOH; excessive die swell differential can cause hard-edge parison curl and non-uniform EVOH coverage in the pinch-off zone. The oxygen barrier contribution is assessed by bottle permeation tests under ASTM D3985 or by total package oxygen uptake methods, with shelf-life targets for oxygen-sensitive sauces typically requiring bottle OTR below 0.01 cm³/(package·day·atm). Drop impact retention is measured by ASTM D2463, and top-load failure force by ASTM D2659; published data for A4412B in specific bottle geometries remain limited, so production qualification requires line trials with filled package distribution testing.

Rigid Barrier Tray Thermoforming: Plug-Assist Settings and EVOH Layer Thickness Retention

Thermoforming of coextruded PP/EVOH sheet into shallow and deep barrier trays imposes a second thermal cycle on the EVOH layer. Sheet surface temperature at the forming station is typically set between 160 and 180 °C, just above the 164–168 °C EVOH melting range but below the point where the PP skin loses hot strength. The process window is narrow: at surface temperatures above 185 °C, the EVOH core can adhere to the plug and delaminate; below 155 °C, the EVOH layer acts as an elastic barrier and resists uniform draw, producing thin spots at the tray base radius. Plug-assist pressure forming with a heated syntactic foam plug at 80–110 °C and forming air at 4–6 bar is used to redistribute material toward the tray corners. EVOH layer thickness after forming is not uniform; corner regions can retain only 30–50% of the original layer thickness at a draw ratio of 1.5:1 to 2.5:1. This local thinning directly determines the formed tray oxygen barrier: a tray with an initial 15 µm EVOH layer may show corner OTR values one and a half to three times higher than the flat sheet. On-line quality monitoring uses cross-sectional microscopy of polished tray sections and oxygen transmission screening by ASTM D3985 on specimens cut from the base and flange. For fatty and acidic foods, regulatory leakage is checked by EN 1186-14 with food simulants; EVOH compliance under EU Regulation 10/2011 requires that the final tray migration does not exceed 10 mg/dm² overall migration and that residual vinyl alcohol monomer remains within positive-list specifications. Thermoformed tray scrap containing EVOH cannot be simply recycled into the PP skin without compatibilisation because uncompatibilised EVOH domains behave as stress concentrators and reduce PP impact strength; 3–10% regrind is often tolerated in the core layer when processed with additional tie resin, but pellet-to-pellet variability in regrind viscosity must be controlled with gravimetric dosing.

When Oxygen Barrier Pipe Is Extruded Under DIN 4726 for Closed-Loop Heating Systems

Closed-loop radiant heating pipes manufactured with an oxygen barrier layer use Soarnol A4412B between inner and outer polyethylene or polypropylene layers. The oxygen permeability requirement for oxygen-barrier pipe under DIN 4726 is commonly set at or below 0.1 g/(m³·day) at 40 °C, and the EVOH layer thickness required to meet this value is typically in the 80–150 µm range for a 16 × 2 mm pipe. The 44 mol% ethylene grade is selected because it combines sufficient oxygen barrier with lower flexural modulus and better stress-crack resistance under thermal cycling from 20 to 90 °C than 32 mol% or 38 mol% grades. Coextrusion tooling uses a spiral mandrel die or spider-leg die with melt temperatures of 200–220 °C for the EVOH layer, while the polyolefin layers are processed at 210–240 °C; differential melt viscosity is controlled by selecting a tie resin with melt flow rate close to the EVOH and by maintaining EVOH melt pressure at 50–90 bar. A critical process failure in pipe lines is EVOH layer rupture during vacuum sizing or corrugation when the EVOH melt is too cold or when adhesion to the tie layer is incomplete; adhesion is verified by ISO 11339 T-peel measurement, with target peel strength above 15 N/15 mm. The EVOH layer must be continuous at the pipe weld line; weld-line thinning can be inspected by cutting a cross-section and staining with iodine solution, where voids appear as unstained regions. Pipe scrap containing EVOH is recycled into the middle layer of three-layer pipe or into the outer layer only after reprocessing with odour-neutralising additives, but direct reuse in the inner layer is not recommended because of hydrolysis products and gel particles. The long-term hydrostatic strength of the composite pipe is evaluated under ISO 9080, while oxygen permeation is assessed by the method specified in DIN 4726 at the relevant service temperature.

Small-engine and automotive fuel tanks coextruded from high-density polyethylene utilise Soarnol A4412B as an internal hydrocarbon barrier layer, but published data for this specific grade in direct fuel immersion is limited. The hydrocarbon barrier mechanism differs from oxygen barrier: the polar vinyl alcohol segments resist nonpolar hydrocarbon diffusion, while the 44 mol% ethylene segments maintain layer ductility at low temperature. Permeation performance is governed by EPA 40 CFR Part 86 evaporative emission procedures, CARB LEV III requirements, and SAE J1737 for fuel system permeation measurements. Multilayer tank coextrusion uses six-layer blow moulding with an EVOH layer of 1–3% of wall thickness and a regrind layer; this configuration is similar to that of barrier bottles but is processed at higher melt temperatures of 220–235 °C and with larger accumulator-head machines. The EVOH layer must be fully encapsulated by tie resin because moisture in the fuel and external environment can plasticise the EVOH and reduce adhesion, leading to delamination at the pinch-off seam. Long-term barrier performance is evaluated by fuel immersion tests with aggressive ethanol blends such as CE10 and CE85; suppliers generally recommend a dedicated grade confirmation trial because A4412B is not universal across all fuel compositions. The T-peel adhesion test by ISO 11339 and hydrostatic tank burst testing under ECE R34 are used to qualify the coextruded wall, with particular attention to pinch-off seam thickness and EVOH continuity. Without sufficient regrind management, accumulated EVOH in the recycled HDPE layer shifts the melt flow ratio and can produce weld-line defects in the bottom seam.