HANWHA EVA 1218 (em inglês)

HANWHA EVA 1218 is an ethylene-vinyl acetate copolymer produced in the low-vinyl-acetate segment of the EVA portfolio. Its nominal vinyl acetate incorporation of 12 wt% and melt flow rate of 18 g/10 min at 190°C/2.16 kg, measured under ISO 1133-1:2022 and ASTM D1238, position it as a high-flow, medium-stiffness material for moulding and compounding. The vinyl acetate comonomer disrupts polyethylene crystallinity more than homopolymer LDPE, but less than EVA copolymers containing 18–28 wt% VA. As a result, EVA 1218 retains a higher crystalline fraction, giving higher room-temperature modulus, higher Shore D hardness, lower tack, and lower elongation retention at sub-ambient temperatures than high-VA grades. The nominal density of 0.93 g/cm³ is typically reported under ISO 1183-1:2019 or ASTM D792. The combination of 12 wt% VA and 18 g/10 min melt flow rate is used in fast-cycle injection moulding, chemically blown foam, extruded profiles that do not require high melt strength, and masterbatch carrier formulations where dispersive mixing must be achieved at moderate barrel temperatures.

The values in the specification table are manufacturer-reported reference values, not lot-release tolerances. Certificate-of-analysis data for the production lot should be obtained before tooling trials because vinyl acetate content, melt flow rate, density, and additive package can vary within the supplier’s specification window. Published multi-point mechanical data for this specific configuration is limited; therefore, compound qualification should include tensile and impact testing on actual production-scale plaques or moulded parts, not reliance on nominal grade data alone. Incoming resin should be inspected for flow consistency using ISO 1133-1:2022 and for density using ISO 1183-1:2019 before large-scale production runs.

Does the 12 wt% Vinyl Acetate Fraction Maintain Low-Temperature Ductility?

In tensile testing performed according to ISO 527-2 with type 1B dumbbells or ASTM D638 Type IV specimens, lower-vinyl-acetate EVA copolymers such as EVA 1218 develop higher yield stress and higher modulus at a given melt flow rate than EVA grades with 18–28 wt% vinyl acetate, while elongation at break remains in the several-hundred-percent range. This behaviour is a direct consequence of the lower comonomer content: longer uninterrupted methylene sequences allow thicker lamellae and greater crystalline order, while the amorphous fraction available for energy absorption is reduced. For that reason, EVA 1218 should be benchmarked against higher-VA EVA or olefin block copolymers when a part must withstand repeated impact at temperatures below −40°C. The low-temperature impact transition is strain-rate dependent, and notched Izod or Charpy data alone may not predict product failure in freezer environments. Freezer hinge tests or multi-axial impact tests on moulded prototypes conditioned at −30°C for 24 hours under ISO 291 are more representative. Hardness measurements under ISO 868 or ASTM D2240 should be taken after conditioning at 23°C/50% RH for 40 hours; Shore D values for EVA 1218 are expected to be higher than those of 18 wt% VA copolymers, and this must be accounted for in low-durometer or cushioning part specifications.

Thermal Transitions and Crystallization Rate Effects on Mould Release

Differential scanning calorimetry under ISO 11357-3 is used to characterise the melting endotherm and crystallization exotherm of EVA 1218. Because the 12 wt% vinyl acetate level preserves a significant crystalline fraction, the crystallization temperature and crystallinity are higher than those of high-VA grades; this can shorten cooling time in injection moulding but can also increase shrinkage anisotropy when mould temperature is non-uniform. The melting endotherm is broad and not a single point; the peak melting temperature depends on thermal history and heating rate. Mould release should be validated after measuring the solidification plateau by DSC or by ejector-force transducers on the production tool. A mould temperature from 15°C to 40°C is a typical starting range, but thick sections may require a higher mould temperature to reduce differential shrinkage and avoid sink marks. Because the grade has an 18 g/10 min melt flow rate, freeze-off at the gate can be faster than with lower-MFR grades; gate geometry and holding-pressure time must be adjusted to avoid premature gate sealing, particularly in thin-wall tools with wall sections below 1.5 mm. The crystallization behaviour also affects foam expansion: if crosslinking advances before the blowing agent decomposes, the crystalline regions restrict cell growth and increase foam density; if blowing occurs before adequate melt strength develops, cell coalescence and collapse occur. Therefore, thermal analysis and cure rheometer curves under ISO 6502 are recommended before setting production parameters.

Compounding and conversion of HANWHA EVA 1218 on a 40:1 L/D co-rotating twin-screw extruder are initiated with barrel temperatures from 150°C to 170°C, with the actual zone profile adjusted for screw speed, feed rate, and backpressure. The 18 g/10 min melt flow rate reduces viscosity relative to lower-MFR EVA grades, but high-shear kneading elements can still produce local melt temperatures above 220°C. Residence time above 230°C for more than 5 minutes can initiate acetic acid elimination, gel formation, and discolouration; therefore, screw configurations with excessive neutral kneading blocks should be avoided. A conservative processing boundary is to keep melt residence time below 5 minutes and to check melt-flow shift after compounding as a screening indicator. Pellets stored in opened bags at ambient relative humidity above 60% should be dried at 60–70°C for 2–4 hours in a desiccant dryer before extrusion or injection moulding; regrind above 20 wt% increases the probability of surface silvering and should be dried under the same conditions. In injection moulding, a melt temperature of 150–180°C and a mould temperature of 15–40°C are typical starting values, with clamp force calculated from the projected area using filling pressures near 50–80 MPa. Short-shot studies and capillary rheology curves generated under ISO 11443 are preferred for transferring setting conditions across different injection machines.

Torque-Rheometer Signatures and Filler Dispersion Limits in EVA 1218 Compounds

The acetate groups in EVA 1218 improve filler wetting relative to LDPE in torque rheometer comparisons, but 12 wt% vinyl acetate is still insufficient for high-surface-area fillers such as untreated fumed silica or certain organophilic clays without additional coupling agents. Torque rheometer testing under ASTM D3795 or supplier-internal protocols locates the maximum filler loading before melt viscosity exceeds the extruder’s torque limit. At calcium carbonate or magnesium hydroxide loadings above 40 wt%, torque rise is sharp and throughput usually becomes limited by feed and venting rather than screw speed. Magnesium hydroxide-filled EVA compounds used for flame-retardant cable applications can require a polar wax or stearate lubricant; however, stearate levels above the formulation-specific optimum can plate out on downstream rolls and reduce heat-seal strength. Amine-based antistatic agents and amine-functional coupling agents should be treated as incompatible with peroxide cure systems until a cure study confirms otherwise, because residual amines may consume peroxide radicals and retard crosslinking. A hindered phenolic antioxidant combined with a phosphite processing stabiliser is normally sufficient for short-term processing stability; long-term heat-aging performance must be qualified using ISO 188 or UL 746B if the service temperature exceeds 60°C. Batches that display an unusually low final torque in the rheometer should be checked for vinyl acetate content or contamination, because a reduction in torque can also indicate lubricant overload or blend incompatibility.

Candidate applications for HANWHA EVA 1218 include injection-moulded footwear components, general flexible goods, gaskets and seals that do not require high-temperature compression-set resistance, closed-cell foam pads, and low-temperature masterbatch carrier resins. In chemically blown footwear foam, the grade is typically compounded with azodicarbonamide-based blowing agent, zinc oxide or zinc stearate kicker, and dicumyl peroxide for crosslinking. The process window is bounded by the blowing-agent decomposition onset, commonly 190–220°C, and the crosslinking rate of the peroxide package; expansion must begin after melt temperature is stable but before crosslinking restricts cell growth. Because the 12 wt% vinyl acetate level gives a higher crystalline fraction than high-VA foam grades, cell expansion may require slightly higher blowing-agent loading or higher expansion temperature to reach the same foam density. Published data for this specific configuration is limited; therefore, expansion ratio, cell-size distribution, compression set under ISO 815, and rebound resilience under ISO 8307 should be measured on production-scale press moulding or continuous vulcanisation equipment. The same grade can serve as a carrier resin for pigment and additive masterbatches up to 40–50 wt% additive loading, depending on filler bulk density and oil absorption, provided the final melt flow rate remains compatible with the let-down resin.

When Higher-Vinyl-Acetate Grades Replace EVA 1218 in Impact-Damping Applications

Within the EVA grade portfolio, selection between EVA 1218 and higher-vinyl-acetate grades such as EVA 1810 or EVA 1530 is governed by Shore hardness, low-temperature flexibility, melt strength, and compression set. EVA 1218 yields a higher Shore D hardness and higher tensile modulus at equivalent filler loading than grades containing 18–28 wt% vinyl acetate, but it also provides less softness retention after plasticizer migration and lower low-temperature ductility. Compared with lower-melt-flow EVA grades, EVA 1218 offers lower melt strength and faster freeze-off, which improves thin-wall injection moulding cycle time but reduces suitability for thick sheet extrusion or blown film where parison sag and melt draw are limiting. Compared with very high-flow EVA grades above 25 g/10 min, EVA 1218 provides higher melt strength and less open-nozzle drool. The replacement of EVA 1218 with a high-VA grade is technically justified when low-durometer impact absorption, flexibility below −40°C, or high melt strength are required. Conversely, replacement of a high-VA grade with EVA 1218 may be justified when part hardness, dimensional stiffness, and mould-filling speed are more important. The final grade selection should be confirmed by measuring Shore D after conditioning under ISO 291, tensile modulus under ISO 527-2, and compression set under ISO 815 on the actual part geometry at the intended service temperature.

Regulatory documentation for HANWHA EVA 1218 normally includes REACH SVHC declarations, RoHS recast 2011/65/EU compliance data, and a safety data sheet; these documents do not by themselves establish food-contact status. For food-contact or medical applications, the specific grade formulation and the finished article must be evaluated under EU 10/2011 or FDA 21 CFR 177.1520 where applicable, and migration testing should be conducted at the intended use temperature and duration. Storage should follow the current packaging label and technical datasheet; sealed original bags stored below 40°C and below 60% RH are typically used to minimize moisture uptake and antioxidant depletion. Opened bags should be consumed within 24 hours when practical or resealed under nitrogen, because moisture and oxygen exposure can accelerate additive loss and surface degradation. Incoming lots should be released by melt flow rate, density, and visual pellet inspection before being introduced into a production system where traceability is controlled by lot number.