Ionómero SURLYN AD1032

SURLYN AD1032 is a sodium-neutralized ethylene/methacrylic acid ionomer supplied as pelletized resin for extrusion coating, cast film, sheet extrusion, laminate interlayers, and injection-molded packaging. Nominal melt mass-flow rate is 1.0 g/10 min at 190 °C and 2.16 kg load according to ISO 1133-1:2022; nominal density is 0.94 g/cm³ according to ISO 1183-1:2019. The ionomer architecture consists of ethylene segments interrupted by methacrylic acid units partially neutralized with sodium cations, producing thermoreversible ionic clusters that function as physical crosslinks below the melting region and dissociate under melt shear. Typical screening values from manufacturer technical literature place DSC melting point in the range 90–95 °C (ISO 11357-3), Shore D hardness at 55–65 (ISO 868), and flexural modulus at 300–400 MPa (ISO 178) for conditioned specimens. The grade is distinguished from non-neutralized acid copolymers by higher melt strength and greater oil resistance, while retaining melt processability on conventional equipment.

In cast film and extrusion coating, the 1.0 g/10 min melt mass-flow rate places AD1032 in the low-flow segment for ionomers, which increases extrusion head pressure and improves web stability for thick-gauge sheet and laminate interlayers compared with melt-flow grades above 3.0 g/10 min. Typical usage includes heat-seal layers on aluminium foil, paperboard barrier packaging, skin packaging for hardware and personal care articles, and clear laminate films where seal-through-contamination performance is required. On film lines, die lip deposits and edge neck-in are controlled by maintaining the air gap below 150 mm and the melt temperature within the recommended band; published data for specific line-speed thresholds at this grade are limited, so start-up trials with die width and coat weight are used to establish stable processing boundaries.

Processing Window and Melt Rheology in Cast Film and Extrusion Coating

Production-scale cast film and extrusion coating lines typically process AD1032 on single-screw extruders with 30:1 to 33:1 L/D ratios and barrier or Maddock mixing sections. A representative barrel profile from feed to metering is 170 °C, 185 °C, 200 °C, 210 °C, with adapter and die held at 210 °C to 220 °C. At these settings, melt pressure measured at the breaker plate commonly falls between 8 MPa and 14 MPa depending on screen pack and throughput. Raising melt temperature above 245 °C accelerates gel formation and produces acetic acid-type by-products; lowering melt temperature below 180 °C increases apparent viscosity enough to generate melt fracture and poor draw-down. Residence time in the barrel above 220 °C should not exceed 20 min during line stoppages.

For 25 μm coating onto 18 μm aluminium foil, typical chill roll temperatures of 10 °C to 18 °C are used to suppress crystallinity and maximize clarity; vacuum box and electrostatic pinning are required to prevent draw resonance at line speeds above 150 m/min. Edge neck-in becomes the process-limiting variable at high line speed, and die gap reductions from 0.6 mm to 0.4 mm reduce neck-in but raise die lip shear stress. Operators monitor melt pressure fluctuation at the breaker plate as an early indicator of moisture-induced rheology drift.

How Does Sodium Neutralization Affect Adhesion to Aluminium Foil Compared with Zinc Ionomers?

The sodium cation in AD1032 influences the polar component of surface energy and the density of ionic cluster phases. In extrusion lamination to aluminium foil, sodium-neutralized ionomers generally develop adhesion at melt temperatures of 205 °C to 230 °C without a primer; zinc-neutralized grades may display similar adhesion but differ in clarity and moisture sensitivity. Adhesion performance is measured by T-peel after conditioning at 23 °C and 50% relative humidity, commonly reported with ASTM D1876. The presence of sodium ions rather than zinc ions shifts the ionic cluster dissociation temperature and changes the balance between hot tack and seal-through-contamination; grades intended for high-clarity laminate interlayers often prefer sodium neutralization because of lower haze development in thick cross-sections.

At equivalent melt mass-flow rate, sodium-neutralized ionomer grades can produce higher extensional viscosity at low shear than zinc-neutralized counterparts, which assists in maintaining web stability during extrusion coating but can increase back pressure on shallow-channel screws. This characteristic is evaluated through melt pressure data from production extruders rather than standard melt flow testing alone.

When Heat Seal Initiation Must Fall Below EVA-Coated Structures

In flexible packaging, seal initiation temperature is evaluated using ASTM F2029 at a seal dwell of 0.5 s and jaw pressure of 0.3 MPa. SURLYN AD1032 is selected when a sealant layer must maintain adhesion through oily, dusty, or powdered product residues; ethylene vinyl acetate sealants at comparable thickness often lose seal strength under the same contamination because the acetic acid-derived comonomer does not generate the same ionic bond mobility. The hot tack envelope is measured by ASTM F1921. The low-flow character of AD1032 allows the sealant to retain cohesive strength during the molten seal stage, although actual seal initiation values are film-thickness and substrate dependent; published data for this specific configuration is limited. Multilayer structures therefore position AD1032 as the inner sealant web in vertical form-fill-seal lines running above 80 pouches/min, where hot tack must exceed the peel force imposed by product drop.

For heat seal lapping against aluminium foil or oriented polyester, adhesive and cohesive failure modes are separated by peel angle and jaw temperature. Cohesive failure within the ionomer layer indicates that the seal has developed sufficient bond strength; adhesive failure at the foil interface indicates that the melt temperature at the foil surface has not exceeded the sodium ionomer wetting threshold. This distinction is used in production trials to define the minimum corona treatment level and line speed for a given foil gauge.

Moisture uptake remains the primary material-handling constraint. At relative humidity above 60%, pellets absorb moisture and shift melt rheology sufficiently to produce splay, bubbles, and variability in extrusion coating thickness. Pre-drying in a desiccant-bed hopper with the inlet air dew point at or below -40 °C and pellet bed temperature of 60 °C for 4 h is specified as the operational boundary; regrind levels above 30% may require extended drying because of increased surface area. Processing without adequate drying results in moisture content above 0.05 wt%, which is visible as melt pressure fluctuation at the breaker plate and loss of clarity in thick sheet. The constraint is reversible through redrying, but hydrolytic degradation at melt temperatures above 230 °C becomes more pronounced if moisture exceeds 0.10 wt%.

Reversible Ionic Crosslink Density Determines the Performance Boundary

Compared with non-neutralized ethylene methacrylic acid acid copolymers, SURLYN AD1032 has a higher apparent melt strength at low shear because sodium cations coordinate with multiple carboxylate groups to form ionic clusters. These clusters do not require peroxide or radiation crosslinking and can be re-melted; the scrap from trim and edge neck-in can be reprocessed within the same extrusion process. The ionic clusters increase puncture toughness and slow haze development in thick sheet. Compared with ethylene vinyl acetate copolymers with 18% vinyl acetate, the ionomer does not depend on the vinyl acetate comonomer plasticization for flexibility and shows lower odor and lower extractable polar monomers in food-contact applications. The stiffness and hardness are lower than oriented polyester and polyamide, so AD1032 is not a substitute for high-barrier structural layers; its function is as a sealant, interlayer, or clear packaging layer.

At ambient temperature, the ionic clusters behave as thermoreversible crosslinks; at melt temperatures above 200 °C, cluster dissociation reduces viscosity and permits conventional thermoplastic processing. This transition is shear-sensitive and is not captured by melt flow rate alone, which explains why two ionomer grades with similar melt flow rates can behave differently on the same extruder.

In injection molding of cosmetic caps and thick-wall transparent parts, AD1032 is processed on conventional reciprocating-screw machines. Melt temperature is maintained at 200 °C to 230 °C, mold temperature at 10 °C to 30 °C, and back pressure below 1.0 MPa to avoid excessive shear heating. Because the ionic clusters re-form on cooling, ejection can occur at higher part temperature than non-neutralized copolymers; however, deep undercuts and thin hinges require radius design allowances because the resin has a sharper yield behavior than flexible polyolefins. The material is not recommended for continuous service above 50 °C under load without creep testing according to ISO 899-1:2017.

Verifying Food-Contact Status Under FDA 21 CFR and EU Regulation (EU) No 10/2011

Food-contact status is not self-certifying by resin grade alone; end-use testing and migration verification are required for the final laminated or printed structure. The applicable references include the following.

Formulators should avoid primary or secondary amine-based antistatic compounds and certain amine-functional slip additives unless their concentration is confirmed by capillary rheometry before production. The residual carboxylic acid groups in the ionomer can react with amine groups, increasing melt viscosity at 230 °C and generating localized gel particles. Similarly, copper-based heat stabilizers used in some polyolefin extrusion coating lines are unnecessary and can create discoloration in the presence of residual acid groups. Masterbatch carriers should be selected from sodium ionomer or acid copolymer grades; polyethylene carriers can contribute to haze and reduce interlayer adhesion when diluted above 10%. This compatibility boundary is specific to multi-day production runs where residence time distribution broadens and by-products accumulate in dead zones and screen packs.