HANWHA EVA 1157 (em inglês)

HANWHA EVA 1157 is an ethylene-vinyl acetate random copolymer supplied for injection moulding, profile extrusion, blown film modification, chemical foaming, and hot-melt compounding. The product belongs to the low-vinyl-acetate portion of the producer’s EVA portfolio, with a nominal vinyl acetate content of 11.0 wt% determined by ASTM D5594. Melt flow rate is 5.7 g/10 min at 190°C/2.16 kg under ASTM D1238 or ISO 1133-1:2022. Nominal density is 0.932 g/cm³ under ASTM D1505. The crystalline melting point is approximately 95°C by ASTM D3418, and the Vicat softening point is approximately 78°C by ASTM D1525. Shore D hardness is 46 under ASTM D2240. These values define a grade that retains sufficient ethylene crystallinity for stiffness and dimensional stability while the 11.0 wt% comonomer reduces crystallite thickness, lowers brittle failure risk relative to LDPE, and improves filler acceptance.

The resin is stabilised with a phenolic/phosphite antioxidant package and is supplied as cylindrical pellets. It is not formulated with slip or antiblock agents for injection-moulding applications. Compared with 18.0 wt% or 28.0 wt% vinyl acetate copolymers, 1157 shows lower surface tack, higher Vicat softening temperature, and lower moisture affinity. Compared with LDPE/LLDPE of equivalent melt flow rate, it shows lower tensile modulus, higher elongation, and improved resistance to environmental stress cracking. These differences make the grade a starting point for flexible polyolefin compounds and for injection-moulded parts where polyolefin-like surface feel is required without full plasticisation.

Material drying is generally unnecessary at relative humidity below 50%. At relative humidity above 60% or when surface splay appears in high-gloss or transparent parts, pellet drying at 75°C for 2 h in a desiccant hopper drier is an accepted correction. For injection moulding, barrel temperature profiles from 150°C in the rear zone to 195°C at the nozzle are typical on general-purpose screws with L/D ratios of 18:1 to 22:1 and compression ratios of 2.5:1 to 3.0:1. Back pressure of 0.5 MPa to 1.5 MPa is sufficient for consistent shot weight; higher back pressure can lead to melt temperature overshoot and surface striations. Mould temperatures of 20°C to 40°C are usual for general-purpose cavities.

Melt residence time above 210°C should be limited because thermal deacetylation of the vinyl acetate side groups releases acetic acid, which can stain unplated mould surfaces and discolour transparent formulations. Screw cushion should be maintained between 3 mm and 5 mm for effective packing; excessive cushion beyond 8 mm increases residence time and can produce gas voids. In hot-runner systems, gates below 1.0 mm may freeze prematurely because of the semicrystalline nature of the melt; gates of 1.2 mm to 2.0 mm are advisable for wall sections above 2.0 mm. The material is not recommended for large-parison blow moulding because the 5.7 g/10 min melt flow rate lowers parison sag resistance relative to 1.7 g/10 min or 2.0 g/10 min EVA grades.

On production-scale injection machines, a clamp force estimate of 3 kN/cm² of projected part area is commonly used as a first layout value for this flow range, although thin-walled and large-flow-length parts require filling simulation. If nozzle melt pressure exceeds 18 MPa in a cold-runner tool, gate size and melt temperature should be adjusted before increasing injection speed further. Linear mould shrinkage is typically less than 2.0%; post-mould shrinkage can continue for 24 h to 48 h and should be accounted for in critical dimensions. Knit-line strength improves when mould temperature is raised from 20°C to 40°C, but the cycle-time penalty is typically 10% to 15%.

Colour concentrates based on LDPE or EVA carriers are preferred. A carrier with a melt flow rate below 2.0 g/10 min can produce dispersion striping if let-down ratios exceed 4%; carriers with significantly higher melt flow can cause screw slippage in the feed zone. At let-down ratios above 5% of a highly filled masterbatch, pre-mixing with virgin pellets in a hopper blender is recommended rather than relying on natural pellet mixing.

Why does 1157 fill thin-wall moulds more readily than a 1.7 g/10 min EVA of similar vinyl acetate content?

The 5.7 g/10 min melt flow rate is approximately three times that of a 1.7 g/10 min material, which reduces apparent viscosity under the shear rates of 100 s⁻¹ to 1000 s⁻¹ encountered in thin-wall moulding. This translates into shorter filling time, lower peak injection pressure, and lower clamp force for the same shot volume. In a spiral flow comparison at 190°C, the flow length improves over a lower-flow 11.0 wt% vinyl acetate product, but the relationship is not linear with melt flow rate because shear thinning behaviour converges at high rates. The practical benefit appears most strongly in wall sections below 1.5 mm, where pressure drop is dominated by viscosity rather than solidification.

The same lower molecular weight reduces extensional viscosity and melt strength. In foam extrusion, parison blow moulding, and large deep-draw thermoforming, 1157 will sag or lose cell-gas containment more readily than a 1.7 g/10 min or 2.0 g/10 min EVA. Compared with a 15.0 wt% or 18.0 wt% vinyl acetate product, 1157 has a higher Vicat softening point and higher flexural modulus, lower surface tack, lower blocking, and reduced adhesion to polar substrates. It is not recommended for photovoltaic encapsulant film, where vinyl acetate levels above 28.0 wt% are typically required for peroxide crosslinking density and adhesion to glass.

At the molecular level, the 11.0 wt% vinyl acetate units are randomly distributed along the ethylene chain; they interrupt crystallisable sequence length and lower the amorphous-phase mobility barrier. This changes the thermal behaviour observed in ASTM D3418 melting curves: the main endotherm is broadened and shifted to approximately 95°C, whereas a typical LDPE of similar density melts near 106°C. The reduced crystallinity improves low-temperature impact and lowers modulus, but the product is still not as soft as plasticised PVC or 28.0 wt% EVA.

For service at low temperature, injection-moulded 1157 parts retain flexibility below -40°C. If the application requires elastomeric recovery at -60°C, a higher vinyl acetate EVA or an olefin elastomer blend is normally specified. The resin also has lower resistance to aromatic and ketone solvents than high-density polyethylene; prolonged contact with toluene or methyl ethyl ketone can induce swelling and stress cracking, so solvent-welded assemblies should be tested under ASTM D543 or ISO 22088-2.

Compounding azodicarbonamide foams with controlled cell nucleation and crosslink density

In chemically foamed footwear midsoles, sports mats, and insulation profiles, 1157 is mixed in an internal mixer or kneader at a drop temperature below 125°C when azodicarbonamide at 1.5 phr to 2.5 phr and dicumyl peroxide at 0.1 phr to 0.3 phr are used. The 11.0 wt% vinyl acetate content increases amorphous-phase mobility for gas dissolution, while the residual crystalline fraction retains cell-wall stiffness and reduces demoulding shrinkage. Moulded sole preforms commonly reach foam densities of 0.15 g/cm³ to 0.25 g/cm³. Compression curing at 160°C for 10 min to 15 min is typical; shorter cycles require a coagent such as triallyl cyanurate at 0.1 phr to 0.5 phr, but the network may show higher compression set if cure uniformity is poor.

Compared with a 15.0 wt% or 18.0 wt% EVA of equivalent melt flow, 1157 produces a harder foam at equal density and has a narrower processing window in low-density foam extrusion because the lower amorphous fraction provides less gas retention above the blowing-agent decomposition temperature. Below a density of 0.12 g/cm³, surface defects and cell coalescence become more likely unless a higher-VA grade or a melt-strength-modified polyolefin is blended. Published data for this specific configuration is limited; minimum-density trials must be run with the actual blowing agent, nucleant package, and mould tooling to establish the viable floor.

When 1157 is selected as a base polymer in low-to-medium polarity hot-melt systems

Hot-melt formulations based on 1157 typically use hydrogenated hydrocarbon tackifiers in the 30 wt% to 50 wt% range and paraffin or Fischer-Tropsch wax at 10 wt% to 20 wt% to reach application temperatures of 165°C to 175°C. The 11.0 wt% vinyl acetate level provides adhesion to kraft paper, wood, leather, and some painted metals, but lower adhesion to polar ionomer surfaces and primed metals than a 28.0 wt% VA grade. In high-speed packaging, open time and hot tack are lower than with higher-VA systems; this can shorten setting time on porous substrates, but it is a limitation on semi-gloss board or cold glass containers.

Melt stability requires tank temperature control below 180°C and nitrogen blanketing in low-throughput operations. Colour drift after 8 h at 180°C indicates antioxidant consumption, and stabilisation should be adjusted with 0.1 wt% to 0.5 wt% additional hindered phenol or phosphite rather than by raising application temperature. The grade should not be used as the sole base polymer in automotive interior adhesives with continuous service exceeding 90°C, because the low VA level and medium molecular weight provide lower cohesive strength at elevated temperature.

Profile extrusion of flexible clear or translucent tubing, edge trim, and sheet is performed at melt temperatures between 170°C and 195°C, with a single-screw extruder of 24:1 L/D or greater and screen packs of 24 mesh to 40 mesh. The lower VA content reduces surface tack and blocking in wound profiles, which can eliminate talc separation in thin-walled strip packaging. Die swell is lower than that of LDPE; because secondary crystallisation continues for 24 h to 48 h after extrusion, critical dimensions should be checked after ageing rather than immediately after the water bath. The material should not be held against copper or copper-alloy contact surfaces at melt temperature for extended residence, because residual acetate species can promote contact staining.

In blown film, blending up to 30 wt% 1157 with LDPE improves dart impact and low-temperature puncture resistance but narrows the bubble stability window. A blow-up ratio between 2.0 and 2.5 and a frost-line height below 2.0 m are typical for such blends on conventional low-density film lines. The higher melt flow reduces melt strength, and excessive air-ring velocity can generate edge wrinkles in thin-gauge film.

For mineral-filled compounds, calcium carbonate or magnesium hydroxide loadings up to 40 wt% can be incorporated before mixer torque increases excessively; surface-coated fillers and a silane or titanate coupling agent improve dispersion and low-temperature impact retention. The 11.0 wt% vinyl acetate functionality is sufficient to wet many mineral surfaces but not as effective as maleic anhydride-modified polyolefins for highly polar fillers or glass fibre. Avoid direct combination with Lewis-acid or strong amine additives in prolonged high-temperature processing, because the acetate side groups can undergo accelerated deesterification and shift molecular weight.

Material regulatory status must be confirmed against the current safety data sheet and product stewardship declarations. The producer normally reports compliance with REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU for the industrial grade. For food-contact uses, migration verification under FDA 21 CFR 177.1520 or EU 10/2011 is required on the finished article; the standard industrial grade is not automatically certified for all food types or sterilisation conditions.