HANWHA EVA 1125 Ethylene Vinyl Acetate Copolymer

On a three-layer cast film line equipped with a 65 mm barrier single-screw extruder having an 30:1 L/D ratio and a flat die with internal deckling, HANWHA EVA 1125 is metered as the heat-seal skin at a layer ratio of 12 wt% to 18 wt% of total web thickness. The grade carries a nominal vinyl acetate content of 11 wt% and a melt index of 25 g/10 min at 190°C and 2.16 kg in accordance with ASTM D1238. Density is typically 0.930 g/cm³ under ISO 1183-1. Its DSC melt endotherm, recorded under ISO 11357-3, falls between 92°C and 96°C, so the thermal seal initiation is reached below 105°C only when dwell time exceeds 0.5 s and seal-bar pressure is held above 0.3 MPa. Chill-roll temperature is controlled at 18°C to 22°C; higher surface temperatures above 25°C increase blocking tendency on rewind after the film passes through the secondary nip. The resin is not a blown-film grade, and attempts to run the same melt index on a high-stalk bubble typically result in bubble instability below 30 µm thickness when no LDPE is blended.

The film structure commonly places the EVA 1125 layer as the innermost plies in lamination-grade sacks for dry food, where seal strength after the converting step is assessed with ASTM F88/F88M. To raise hot-tack strength on vertical form-fill-seal packaging machines, the resin is dry-blended or melt-compounded with a fractional-melt low-density polyethylene at 10 wt% to 25 wt%. At the higher end, the seal initiation trend shifts upward by 3°C to 5°C, while the hot-tack peak measured on a 0.5 mm sealing bar broadens. The converter must hold melt temperature below 230°C in the skin extruder; prolonged exposure above 240°C accelerates thermal deacetylation and releases acetic acid, which attacks the feedblock and die lip surfaces during runs longer than 48 h. Food-contact compliance is evaluated under 21 CFR 177.1350 for ethylene-vinyl acetate copolymers and under EU Regulation 10/2011 for overall and specific migration on the finished laminate, not on the resin alone. A typical structure is 25 µm EVA sealant / 12 µm PET / 50 µm LDPE, with the EVA skin corona-treated to a wetting tension of 40 mN/m before lamination.

What Constrains Melt Curtain Stability During Paperboard Extrusion Coating?

High-speed paperboard extrusion coating lines process EVA 1125 either neat or as a blend with LDPE at 20 wt% to 40 wt% EVA, using a 90 mm main extruder with a 32:1 L/D barrier screw. The melt temperature is deliberately raised to 290°C–310°C to promote adhesion to clay-coated paperboard and to reduce the neck-in of the melt curtain. At this temperature range, thermal deacetylation is already active; therefore all melt-contact surfaces from screw tip to die lip are specified in hardened stainless steel and the die lip is hard chrome-plated. At a line speed of 150 m/min and an air gap of 120 mm, the curtain edge neck-in is typically recorded between 50 mm and 70 mm. Increasing line speed toward 250 m/min without reducing the air gap triggers draw resonance as a diagonal wave extending from the die edge toward the nip. Published data for this specific grade on high-speed paperboard lines are limited, so start-up mapping with a laser curtain profiler is required before commercial output is approved.

The coating weight is usually held between 12 g/m² and 25 g/m² for paperboard cups and folding carton stock. If the EVA fraction is pushed beyond 40 wt%, fuming and odor increase beyond acceptable plant exposure limits, and the catalytic oxidation residue contributes to gel counts above 5 gels/m² on the coated surface. Conversely, below 20 wt% EVA, adhesion to the paperboard drops below the acceptable practical limit unless the substrate is pre-treated with a corona discharge unit positioned at 2.0 kW to 3.5 kW. Compliance for the final article is assessed under 21 CFR 176.170 for paper and paperboard components in contact with aqueous and fatty foods, with extraction testing performed on the coated board and not on the neat polymer. Seal strength of the coated board is measured after jaw sealing with ASTM F2029, and the failure mode must remain fiber tear rather than adhesive peel.

The Cure Plateau Where Blowing Agent Activation Mirrors Peroxide Half-Life

Crosslinked EVA foam manufacture with HANWHA EVA 1125 relies on the lower vinyl acetate content to deliver semi-rigid sheet and technical foam components where higher hardness than conventional 18 wt% VA foam grades is accepted. A typical expansion formulation is composed of 100 phr EVA 1125, 3.0 phr to 5.0 phr azodicarbonamide, 0.8 phr to 1.2 phr dicumyl peroxide, 1.0 phr to 2.0 phr zinc oxide, 0.5 phr stearic acid, and 10 phr to 30 phr calcium carbonate when the target density is between 0.20 g/cm³ and 0.35 g/cm³. The two-roll mill is maintained at 90°C to 100°C for 10 min to 12 min so that the blowing agent and peroxide are distributed without reaching the cure onset. The compounded sheet is then transferred to a hydraulic compression press and cured at 155°C to 165°C under 150 kg/cm² to 180 kg/cm² for 8 min to 10 min.

The operating constraint is the overlap between dicumyl peroxide decomposition and zinc-oxide-activated azodicarbonamide decomposition. At 160°C, dicumyl peroxide exhibits a half-life near 5.5 min, while zinc oxide lowers the ADC decomposition exotherm into the 155°C to 165°C window. A press overshoot to 170°C releases gas before sufficient melt strength has developed and produces internal splits and density loss of 0.03 g/cm³ to 0.05 g/cm³. A cure temperature of 150°C leaves gel content below 60% when measured by solvent extraction in xylene adapted from ASTM D2765, causing compression set to exceed 35% under ASTM D3575. Finished foam sheet is tested for density by ISO 845, tensile properties by ISO 1798, and tear resistance by ISO 8067. The terminal components are semi-rigid gaskets, expansion joint filler, and anti-fatigue mat sheets, where the lower VA content limits low-temperature flexibility but improves abrasion resistance and dimensional recovery.

Where the hot-melt adhesive bench requires an EVA with a moderate melt index and reduced low-temperature flexibility but higher cohesive strength, HANWHA EVA 1125 is evaluated as the base copolymer at 28 wt% to 35 wt% in packaging-grade formulations. The remaining components are a hydrogenated hydrocarbon tackifier at 30 wt% to 45 wt%, a Fischer-Tropsch wax with a congealing point of 72°C to 90°C at 20 wt% to 28 wt%, and a hindered phenolic antioxidant at 0.5 wt% to 1.0 wt%. Mixing is carried out in a jacketed sigma-blade mixer at 150°C to 170°C under a nitrogen sweep; the polymer and antioxidant are added first, followed by the tackifier, and finally the wax to prevent low-viscosity pooling and thermal degradation. Brookfield viscosity at 180°C, measured with a No. 27 spindle according to ASTM D3236, is typically held between 800 mPa·s and 2200 mPa·s for case and carton sealing lines.

Phase compatibility is the primary formulation risk because an 11 wt% VA content narrows the solubility window with low-polarity aliphatic C5 resins; hot-melt blends that appear clear at 180°C can cloud below 150°C, reducing adhesion to coated cartonboard. Preferred tackifiers are therefore hydrogenated C9 aromatic-modified resins or stabilized rosin esters. Application temperature at the slot coater is set between 160°C and 180°C; below 160°C the flow into corrugated flute tips becomes intermittent, while above 180°C the open time shortens below 1 s and char can form in the heated hose after 8 h of continuous recirculation. The final adhesive is subject to 21 CFR 175.105 for indirect food contact, and bond performance is screened with ASTM D1876 T-peel specimens at 25 mm/min. Terminal applications are corrugated case sealing, carton closing, and tray forming for dry food packaging.

Color Concentrate Carrier Resin and Screen-Pack Pressure Filtration Limits

When EVA 1125 is used as a carrier for carbon black and additive masterbatches, the grade is pre-dried at 70°C for 4 h if moisture content by Karl Fischer titration exceeds 0.05 wt%. The compounding step uses a co-rotating twin-screw extruder with a 40:1 L/D ratio, atmospheric and vacuum venting, and a screen changer fitted with 200 µm to 400 µm breaker plates. Melt temperature is controlled between 170°C and 190°C; above 200°C the ester groups undergo hydrolysis at the surface of undried filler, generating free acid and increasing melt acidity. Carbon black loadings from 40 wt% to 50 wt% and titanium dioxide loadings from 60 wt% to 70 wt% are feasible when screw speed is held between 400 rpm and 800 rpm. The specific energy input at these loadings usually reaches 0.20 kWh/kg to 0.35 kWh/kg, and the melt pressure ahead of the screen pack rises to 250 bar–350 bar. A pressure increase above 0.5 bar/min during the run indicates filter blockage from undispersed agglomerates, requiring a reduction in feed rate or a screen change.

Dispersion quality is assessed by pressure filtration according to EN 13900-5, with a maximum permitted filter pressure value established for the final film or injection part. Terminal masterbatches are let down in polyethylene or EVA films at 3 wt% to 5 wt%, in injection molded crates and caps at 2 wt% to 4 wt%, and in extrusion-coated board at 4 wt% to 6 wt%. The use of EVA 1125 as carrier reduces screw slippage and improves pigment wetting compared with straight high-molecular-weight polyethylene carriers, but the carrier itself contributes to seal-temperature shifts when the masterbatch is used in a heat-seal layer. Compliance for masterbatch containing EVA 1125 depends on the final article; food-contact masterbatches require that the carrier and additives comply with the relevant sections of 21 CFR 177.1350 or EU Regulation 10/2011, and migration tests are performed on the final plastic article rather than on the masterbatch alone.

If Injection Molded Flexible Components Demand Dimensional Stability Without Plasticizer Migration

Injection molding of flexible closures, gaskets, and overmolded grips with HANWHA EVA 1125 is conducted at a melt temperature of 180°C to 200°C and a mold temperature of 15°C to 25°C. The resin is delivered to the hopper as pellets, and no predrying is required unless silo storage humidity has exceeded 60% relative humidity for more than 24 h; in that case, drying at 60°C for 2 h is applied. The injection pressure typically ranges from 50 MPa to 80 MPa, with a back pressure of 5 MPa to 10 MPa to maintain a consistent shot size. Molding shrinkage after 48 h is measured in accordance with ASTM D955 and commonly falls between 1.8% and 2.2% for unfilled sections. The Shore D hardness of the molded part is expected in the 45 to 52 range when measured with ASTM D2240, which is higher than flexible EVA grades containing 18 wt% or 28 wt% VA and therefore better suited to semi-rigid snap-fit geometries.

The absence of added plasticizer is a primary advantage when the component is intended for contact with sensitive surfaces; no plasticizer migration means no surface tack at 60°C aging after 72 h. The low-temperature impact retention of EVA 1125 is bounded by the 11 wt% VA content, and notched impact values drop more rapidly below -10°C than higher-VA grades; thus the resin is not selected for deep-freeze load-bearing parts. Terminal components include injection-molded hinge caps, flexible gaskets for industrial containers, and appliance feet, where compliance to RoHS and REACH is normally established by the molder after the final article is assembled. The injection molding screw is a standard three-zone polyolefin design with a 20:1 to 24:1 L/D ratio and a compression ratio of 2.5:1 to 3.0:1. If the melt temperature exceeds 210°C, surface splay appears on the molded article from low-molecular-weight acetate volatiles, and the incidence of gas burns rises on hot-runner systems with long residence time.