ELVAX 560 Copolímero de Etileno Vinil Acetato

ELVAX 560 is an ethylene vinyl acetate copolymer resin supplied as translucent pellets. The nominal vinyl acetate comonomer content is 15 wt%, and the melt mass-flow rate is 2.5 g/10 min when measured at 190 °C under a 2.16 kg load in accordance with ASTM D1238 or ISO 1133-1:2022. Solid-state density at 23 °C is typically 0.94 g/cm³ as determined by ISO 1183-1:2019. Differential scanning calorimetry under ASTM D3418 places the main melting endotherm near 93 °C, and the Vicat softening temperature is approximately 68 °C under 10 N load per ISO 306:2022. These specifications locate ELVAX 560 in the lower-polarity region of the EVA portfolio: the 15 wt% vinyl acetate content reduces crystallinity relative to low-density polyethylene, imparts low-temperature flexibility, and retains compatibility with nonpolar polyolefins, paraffin waxes, and hydrocarbon tackifiers. Because the molecular weight is higher than that of ELVAX 550 at the same vinyl acetate content, ELVAX 560 is specified where lower melt flow, higher melt strength, and reduced draw sag are required in cast film, extrusion coating, profile extrusion, and melt blending. Certificates of analysis for commercial lots typically report MFR within ±0.2 g/10 min of the nominal value and vinyl acetate content within ±1 wt%; these lot-to-lot control limits are sufficient for most compounding operations provided incoming resin is sampled and tested before silo transfer.

For specification purposes, mechanical testing on compression-molded or injection-molded plaques is conducted under ASTM D638 or ISO 527-2:2012. Published typical values for 15 wt% vinyl acetate EVA in this melt-flow range fall between 12 MPa and 20 MPa for tensile strength at break and between 650 % and 800 % for elongation at break, depending on specimen conditioning, draw ratio, and test speed. Flexural modulus measured by ISO 178:2019 is lower than that of 12 wt% vinyl acetate grades and higher than that of 18 wt% vinyl acetate grades. Hardness is typically in the range of 42 to 48 Shore D when measured by ISO 868:2003. The material exhibits a broad melting endotherm rather than a sharp crystalline peak, which is characteristic of random incorporation of vinyl acetate units that disrupt polyethylene crystallinity. The degree of crystallinity calculated from the DSC melt enthalpy is lower than that of LDPE and depends on the thermal history imposed during cooling. These mechanical and thermal characteristics are relevant where a balance of toughness, flexibility, and dimensional stability under ambient conditions is required. Because the product is a semicrystalline copolymer, post-processing shrinkage and warpage are influenced by cooling rate; controlled cooling to 20 °C at uniform air velocity is recommended for profile extrusion.

Melt Rheology and Processing Boundaries on Twin-Screw Extruders

Temperature control is a primary processing constraint because the vinyl acetate segment begins to undergo thermal deacetylation at sustained melt temperatures above 230 °C; the resulting acetic acid accelerates corrosion of nitrided barrel surfaces, degrades optical clarity, and generates bubble defects in extruded profiles. On a 45 mm co-rotating twin-screw extruder with L/D 36:1, a reverse temperature profile of 130 °C in barrel zone 1, 150 °C in zone 2, 170 °C in zone 3, 180 °C in zones 4 through 6, and 190 °C at the die limits viscous heating while maintaining plastication. Screw speeds are normally held below 250 min⁻¹ because higher speeds in fully filled zones can produce melt-temperature overshoot above 215 °C even when barrel setpoints remain unchanged. Melt pressure at the die is higher than for ELVAX 550 at the same output by roughly 20 % due to the molecular-weight difference. Pre-drying is not required for resin taken from factory-sealed bags with moisture levels below 0.1 wt%; if surface condensation occurs after storage in an unheated warehouse, drying at 50 °C for 4 h with desiccant air at a dew point below −20 °C prevents steam-induced gels. The usable melt-temperature window is narrow at high shear: when melt temperature exceeds 210 °C at screw speeds above 250 min⁻¹, film samples show surface pitting and acetic-acid odor. Direct metering of this pellet resin into a single-screw extruder with L/D 24:1 is possible at lower outputs; a mixing section is recommended when adding powdered tackifiers or fillers because the higher melt strength of ELVAX 560 reduces dispersive mixing relative to a lower-viscosity grade.

Thermal Degradation Kinetics Are Accelerated Above 230 °C

The principal degradation pathway is deacetylation of the vinyl acetate units, which proceeds by radical and ester-cleavage mechanisms with measurable acetic acid evolution above 230 °C under inert atmosphere. Thermogravimetric analysis shows that mass loss depends on both temperature and residence time; published data for this specific grade is limited, but EVA copolymers with similar vinyl acetate content exhibit onset of non-oxidative mass loss near 230 °C and rapid acetic acid release above 250 °C. In compounding trials, a melt-temperature overshoot to 240 °C for 10 min produced a measurable increase in MFR and gel count in blown film; the effect is attributed to main-chain scission and cross-linking reactions following deacetylation. This degradation behavior imposes two operational requirements: melt temperature must be monitored with an immersion probe, and acid-scavenging additives such as zinc stearate may be used in formulations containing moisture-sensitive substrates. The addition of acid scavengers should not exceed 0.1 wt% to 0.5 wt% unless the formulation is explicitly designed for high-acid conditions, because excess metallic stearate can plate out on die lips. Processors should also avoid using copper-based heating elements or bronze screens in contact with melt above 230 °C, because acetic acid accelerates corrosion of copper alloys.

What Distinguishes ELVAX 560 from ELVAX 550 and ELVAX 460?

In melt-flow terms, ELVAX 560 occupies the 2.5 g/10 min slot with 15 wt% vinyl acetate. ELVAX 550 has the same 15 wt% vinyl acetate content but an MFR of 8.0 g/10 min; ELVAX 460 has a higher vinyl acetate content of 18 wt% at the same 2.5 g/10 min MFR. The comparison is not limited to melt viscosity: vinyl acetate content controls polarity, crystallinity, moisture sensitivity, and thermal properties, while molecular weight controls melt strength, draw sag, and the shear-thinning response.

Relative to ELVAX 550, ELVAX 560 provides a higher melt viscosity at the same vinyl acetate content. This translates to greater melt strength and lower draw sag in cast-film and profile extrusion, but it also raises torque in high-speed compounding and can reduce line output by approximately 10 % to 20 % when equipment is torque-limited. Rheological characterization by small-amplitude oscillatory shear at 150 °C shows a higher storage modulus at low frequency for ELVAX 560 than for ELVAX 550, which corresponds to a longer relaxation time and greater melt elasticity. Relative to ELVAX 460, ELVAX 560 has 3 wt% lower vinyl acetate content. The lower vinyl acetate content reduces polarity and specific adhesion to polar substrates such as aluminum, polyester, and glass; it also raises the Vicat softening temperature and lowers equilibrium moisture uptake when measured by ASTM D570. Relative to ELVAX 660, ELVAX 560 contains 3 wt% more vinyl acetate, which improves low-temperature flexibility and tack in hot-melt formulations. Differences in adhesion are quantified by peel tests on polar films: ASTM D1876 T-peel and ASTM D903 peel or stripping tests are commonly used to compare formulated adhesives from these grades on the same substrate. Selection between ELVAX 560 and ELVAX 460 therefore depends on whether polarity and adhesion are more important than hydrocarbon compatibility and moisture resistance. Selection between ELVAX 560 and ELVAX 550 depends on whether the target line can tolerate the higher viscosity of the 2.5 g/10 min grade.

In hot-melt adhesive compounding, ELVAX 560 is commonly melt-blended with hydrocarbon resin tackifiers, microcrystalline waxes, and antioxidant packages at EVA loadings from 25 wt% to 40 wt%. The 2.5 g/10 min MFR of ELVAX 560 produces higher melt viscosity and longer relaxation time than ELVAX 550 at a given formulation; this can reduce penetration into porous board and increase the cohesive component of bond failure. Bond performance is characterized by ASTM D4498 shear strength, ASTM D1876 T-peel, and ASTM D6862 180-degree peel methods depending on the substrate. In case-sealing operations at 160 °C to 180 °C, adhesive stringing is controlled by adjusting application temperature: below 150 °C, the high melt strength of ELVAX 560 can delay clean adhesive break-off and increase stringing, while an application temperature of 170 °C typically reduces stringing without entering the deacetylation region. Open time is governed less by the base resin MFR alone than by the ratio of wax, tackifier, and branched polymer in the formulation; therefore open-time predictions should be based on formulated adhesive viscosity measured by ASTM D3236 at the application temperature. Published data for specific case-sealing line speeds with this exact resin is limited, so line trials are required to establish the upper speed limit for a given board stock and adhesive tank geometry. Batch-to-batch viscosity variation in hot-melt tanks is more sensitive to wax source than to the 0.2 g/10 min MFR tolerance of the resin; however, lot changes should be tracked by full melt-viscosity curves rather than single-point MFR because shear-thinning differences can occur from branching or molecular-weight distribution shifts.

In polyolefin modification, addition of 5 wt% to 15 wt% ELVAX 560 to low-density polyethylene-rich compounds improves environmental stress-crack resistance and impact toughness. The ESCR effect is measured by ASTM D1693 notched constant-strain immersion in 10 % Igepal CO-630 at 50 °C; the relative improvement depends on the base polyethylene density and comonomer type. Because the viscosity mismatch between ELVAX 560 and high-melt-index LDPE can produce phase domains rather than complete miscibility, mixing on a twin-screw extruder with effective shear is preferred over simple dry blending.

When Paraffin Wax Modification Requires a 15 wt% Vinyl Acetate Grade

Paraffin wax systems containing 5 wt% to 20 wt% ELVAX 560 display a monotonic increase in melt viscosity and a reduction in blocking tendency. In paperboard saturating lines, addition above 25 wt% can reduce wax penetration into the substrate because the melt viscosity at 120 °C approaches the upper operating limit of air-knife metering systems. The grade is selected over ELVAX 550 when a wax-modified coating must retain more melt strength during vertical draw or when lower creep at 40 °C is required. The effect on wax crystal size is evaluated by modulated differential scanning calorimetry or microscopy; published data for specific air-knife coaters is limited, so formulated viscosity should be measured by ASTM D3236 at the wet-bath temperature. In fully refined paraffin with melting point 60 °C, addition of 10 wt% ELVAX 560 typically elevates the ring-and-ball softening point of the blend by approximately 5 °C when measured by ASTM E28; with microcrystalline wax the shift is smaller because the base already contains branched-chain structure. Avoid melt blending with strong alkaline additives and certain amine-based stabilizers because these can catalyze ester cleavage; an evaluation of formulation pH after acetone dilution provides a simple screening method. In extrusion coating, ELVAX 560 can be processed at melt temperatures from 160 °C to 210 °C; adhesion to paper and board is typically measured by a tape peel method following conditioning at 23 °C and 50 % relative humidity for 24 h. When high-speed coating lines exceed 200 m/min, the higher melt viscosity of ELVAX 560 may cause draw resonance unless the air gap is shortened.

Under 21 CFR 177.1520, olefin polymers may be eligible for food-contact applications only when the finished article meets the specified extractables limits and end-use conditions; compliance is not an inherent property of the resin. Food-contact status for ELVAX 560 should be confirmed through a supplier declaration referencing EU 10/2011 or FDA 21 CFR 177.1520 as applicable to the target market. The product is not intended for medical implant applications. RoHS screening under Directive 2011/65/EU annex II restrictions for lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE is typically addressed by the supplier's material declaration; if the resin is colored or compounded, the assessment must include the additive package. Storage should avoid unheated warehouses where the pellet temperature falls below the dew point, because surface condensation can introduce moisture into hot-melt mixing vessels. Continuous outdoor exposure of unpigmented ELVAX 560 without UV stabilizers leads to chain scission, gloss loss, and reduction in elongation at break when specimens are tested under ISO 527-2:2012 after weathering. The material should not be processed above 230 °C for extended periods, and any acetic-acid odor during processing indicates that melt temperature reduction or a shorter residence time is required.