Copolímero de acetato de vinilo de etileno ELVAX 3165Z

ELVAX 3165Z is a pelletized ethylene vinyl acetate copolymer supplied under the DuPont ELVAX trade name. The nominal vinyl acetate content is 18 wt%, determined by Fourier transform infrared spectroscopy in accordance with ASTM D5594. The melt flow rate is 0.7 g/10 min when measured at 190°C/2.16 kg per ASTM D1238 or ISO 1133-1:2022; density is 0.94 g/cm³ at 23°C per ASTM D792. The “Z” suffix designates a specific stabilization package; the exact antioxidant identity and regulatory status must be confirmed against the supplier technical data sheet. At 18 wt% vinyl acetate, the grade occupies the lower-polarity segment of the EVA family, retaining sufficient ester concentration for polar filler wetting while preserving a polyethylene-like crystalline melting point and modulus.

The low MFR of 0.7 g/10 min corresponds to a high-molecular-weight extrusion grade. The resin is therefore specified where melt strength, bubble stability, profile shape retention or slump resistance governs the operation, rather than where low-viscosity penetration of narrow gaps is required. The material is supplied as pellets and is compatible with standard polyolefin feeding, drying and melt-compounding equipment, provided the temperature limitations described below are observed.

What operational boundaries govern melt processing of 3165Z on production extrusion lines?

Melt temperature should be maintained below 220°C during continuous extrusion and below 230°C only for short residence times. At and above 230°C, the vinyl acetate segments undergo thermally induced deacetylation, releasing acetic acid and leaving conjugated unsaturation in the polyethylene backbone. The liberated acid accelerates corrosion on steel and aluminium tooling and can shift the pH of any condensed vent-stream water. On a 40:1 L/D co-rotating twin-screw extruder equipped with vacuum devolatilization, barrel settings from feed to die typically begin at 120°C and ramp to 180°C; actual melt temperature should be confirmed by an immersion thermocouple rather than inferred from barrel set points. Screw speed and feed rate should be balanced to keep specific mechanical energy input below the limit that raises melt temperature above 220°C. Residence time in zones above 220°C should be minimized, and continuous operation above that threshold is not recommended. If the resin has been stored at relative humidity above 60%, desiccant drying at 60–70°C for 4–6 h to a moisture content below 0.05 wt% is required before extrusion; surface moisture hydrolyzes the ester groups and increases melt acidity.

On a production-scale 40:1 L/D co-rotating twin-screw extruder with atmospheric and vacuum venting, the low melt flow rate produces a comparatively high melt viscosity and elevated screw torque relative to 8 g/10 min or 19 g/10 min EVA grades. This characteristic is exploited in blown film, sheet and profile extrusion where melt strength controls bubble stability, draw sag and die swell. Rotational rheometry at 190°C shows a strongly shear-thinning response; the zero-shear viscosity is substantially higher than that of faster-flowing EVA grades, while the power-law index in the shear-rate range relevant to die flow permits pumping through conventional polyolefin screw designs without excessive head pressure. Capillary rheometry per ASTM D3835 should be used to generate temperature and shear-rate viscosity curves before die design changes are implemented; published data for this specific Z-stabilized grade is limited, so converter-specific measurements are required. Incoming batch-to-batch MFR variation can be detected by ASTM D1238; converters should establish an internal range around the nominal 0.7 g/10 min value rather than assuming all lots behave identically.

Thermal degradation threshold and acetic acid release

The operational ceiling is governed by vinyl acetate stability rather than polyethylene backbone degradation. Differential scanning calorimetry per ASTM D3418 typically places the melting endotherm near 82–86°C for an 18 wt% VA grade. Deacetylation begins kinetically at lower temperatures but becomes significant above 230°C; the reaction is autocatalytic because released acetic acid accelerates further ester cleavage. In a twin-screw extruder with stagnant zones, local residence-time distributions can allow material to approach this threshold even when the average melt temperature is lower. Vent ports should be maintained under vacuum to strip acetic acid and water; condensed volatiles should be neutralized or routed through corrosion-resistant alloy ductwork. The resin should not be compounded with strongly acidic or basic additives that can hydrolyze the ester groups. Amine-based additives require cautious evaluation because published data for their interaction with the Z-stabilized EVA is limited. Direct contact with copper and unalloyed iron at elevated temperature is discouraged due to metal-ion-catalyzed ester cleavage. For long production campaigns, vent-port inspection and neutralization of condensed acetic acid should be part of the shift checklist.

In injection molding of compounded ELVAX 3165Z-based formulations, barrel temperatures from 140°C to 180°C and screw back pressure below 0.5 MPa are typical starting points for laboratory-scale machines. Production-scale clamp force requirements scale with projected area and are not grade-specific. The low MFR increases filling pressure, so gate size and sprue dimensions should be enlarged relative to high-flow EVA grades. Mold temperatures from 10°C to 30°C shorten cycle time without inducing gross crystallinity gradients, but post-mold dimensional stability should be assessed by conditioning specimens at 23°C and 50% RH for 48 h per ASTM D618 before measuring hardness or tensile properties. For hot-runner systems, internal surface temperatures should not exceed 220°C at any point, and the residence time in the manifold should be minimized to avoid deacetylation in stagnant zones.

Foam extrusion lines use the high melt strength of the resin to stabilize cell walls at the die exit. A tandem extruder with a 32:1 L/D primary screw and a cooling extruder is typical; chemical or physical blowing agent injection occurs in the primary after melting, and the melt is cooled to 95–110°C before the die. The 0.7 g/10 min MFR sustains cell walls at the die exit, reducing blow-hole formation relative to lower-viscosity EVA grades. Density reduction and cell structure should be evaluated by ASTM D1622 and ASTM D3576; published data for ELVAX 3165Z foam density at specific blowing agent levels is limited, so pilot-line trials are required to establish the relationship between blowing agent concentration and final density.

In hot-melt adhesive mixing, the resin is blended with hydrocarbon or rosin ester tackifiers and waxes in a vertical mixer at 150–180°C under nitrogen. The low melt flow rate raises mix viscosity and cohesive strength, reduces stringing, and permits higher filler loading before the formulation becomes too fluid at dispensing temperature. Viscosity of the finished adhesive should be measured with a Brookfield thermosel viscometer per ASTM D3236; end-use peel adhesion on polyethylene or aluminium is evaluated by ASTM D1876 after conditioning at 23°C and 50% RH. The migration kinetics of hydrocarbon tackifiers in the EVA phase can shift peel adhesion over time; peel testing should therefore be repeated after 7 days at 60°C per ASTM D1876 to detect migration-driven adhesion loss. Published data for adhesive formula-specific peel values for ELVAX 3165Z is limited; batch-scale validation against the target substrate is required.

Wax and paraffin blends use ELVAX 3165Z as a viscosity builder and cohesive agent. A heated sigma-blade mixer or a low-shear vertical mixer at 130–170°C is used until a clear homogeneous melt is obtained. The low MFR increases blend viscosity faster than higher-MFR EVA at the same weight fraction; therefore, formulators may reduce the EVA level by 2–5 wt% compared with 19 g/10 min EVA while maintaining the same Brookfield viscosity. Softening and blocking resistance should be confirmed by ring-and-ball softening point per ASTM E28 and blocking tests at 50°C under load. The resin should be added slowly to molten wax under nitrogen to prevent local overheating and acid generation.

When the converter selects a 0.7 g/10 min EVA over 8 or 19 g/10 min alternatives

The most consequential differences from adjacent ELVAX grades are molecular weight, melt flow rate and vinyl acetate content. ELVAX 3165Z has the same nominal 18 wt% VA as ELVAX 450 but a lower MFR, producing higher melt strength, higher viscosity, higher torque, and better retention of shape during foam expansion and profile calibration. Compared with ELVAX 260 at 28 wt% VA, the lower VA level of 3165Z gives a more polyethylene-like crystalline melting point, higher modulus, lower surface polarity and reduced adhesion to unprimed aluminium. Compared with ELVAX 350 at 25 wt% VA and 19 g/10 min, 3165Z is substantially more viscous and is preferred where melt strength, not wetting speed, governs the process.

In polyolefin modification, the resin is dry-blended with LDPE or LLDPE at addition levels from 5 wt% to 30 wt% and compounded on a twin-screw extruder to improve impact toughness, filler compatibility and adhesion to polar layers. The lower MFR of 3165Z preserves melt strength in blown film formulations where higher-MFR EVA would destabilize the bubble. Tensile and flexural properties of the modified polyolefin should be characterized per ASTM D638-14 and ASTM D790-17; impact performance should be measured by ASTM D256 Izod or ASTM D1822 tensile impact, depending on end-use thickness. The actual improvement in impact strength depends on dispersion quality and is not a fixed property of the resin; sieve analysis of the compounded pellets and microscopy of cryofractured specimens should accompany mechanical testing.

Compared with ethylene methyl acrylate and ethylene butyl acrylate copolymers, EVA has a stiffer backbone and a sharper melting transition but a lower continuous-use temperature ceiling because of deacetylation. Ethylene butyl acrylate is often selected when stability at processing temperatures above 230°C is required; propylene-based elastomers may be selected for better thermo-oxidative stability. ELVAX 3165Z is therefore specified where the 18 wt% VA balance among adhesion, modulus and melt strength aligns with a process that does not exceed 220°C. Published comparative data for this specific Z-stabilized formulation against alternate copolymers is limited; selection should be validated by processing trials and end-use thermal aging per ASTM D573 or ASTM D3045 as applicable.

For food-contact use, extraction limits under 21 CFR 177.1350 must be confirmed

The resin can be used in hot-melt adhesives, sealants, wax blends, polymer modification and extruded profiles. For food-contact applications, compliance must be verified under 21 CFR 177.1350 and, where applicable, 21 CFR 177.1520 against the specific end-use extraction conditions; the presence of the Z stabilization package requires supplier confirmation that all components meet the relevant positive lists. Under REACH and RoHS, the grade should be documented through supplier SDS and batch certificates; no intentional addition of lead, cadmium, mercury, hexavalent chromium, PBB or PBDE is typical, but batch-level verification is required. Because the resin contains 18 wt% vinyl acetate, prolonged contact with strong alkalis, strong acids, or metal ions that catalyze ester hydrolysis should be avoided. Exposure to UV without carbon black or hindered amine stabilizers leads to chain scission and surface chalking; outdoor service formulations require additional stabilization and weatherometer testing per ASTM G154. Processing scrap should be dried and re-extruded only after melt flow rate and color verification per ASTM D1238 and ASTM D6290, because repeated heat history can shift the stabilization package and reduce melt stability.