ExxonMobil EVA 45033. Resina de copolímero EH2 EVA

ExxonMobil EVA 45033.EH2 EVA Copolymer Resin is an ethylene-vinyl acetate copolymer supplied as pellets. The nominal vinyl acetate content is 33 wt%, determined by Fourier-transform infrared spectroscopy using ASTM D5594-18. The melt index is 0.45 g/10 min at 190°C and 2.16 kg load, measured in accordance with ASTM D1238-20. Density at 23°C is approximately 0.957 g/cm³, tested per ASTM D1505-18. The grade is positioned in the low-melt-index, high-polarity segment of the EVA copolymer range and is used in hot-melt adhesives, wax modification, mineral-filled compounds, polymer blending, crosslinked foam, and asphalt modification. The low melt index restricts use in thin-wall injection molding and thin-gauge extrusion unless the resin is blended with lower-viscosity polymers or waxes.

The following supplier-published typical values are used for incoming inspection and lot-to-lot comparison. They are not maximum or minimum specifications unless stated in a supply agreement. The values should not be used for specification release without verifying against the current certificate of analysis.

Published supplier data for tensile strength, Shore hardness, and flexural modulus of this specific grade configuration are limited. Mechanical properties should be measured on the finished compound under ASTM D638-14 for tensile behavior and ASTM D2240-15 for durometer hardness, because final values depend on filler loading, plasticizer content, and thermal history.

What distinguishes a 33 wt% vinyl acetate copolymer from lower-VA grades during compounding?

The 33 wt% vinyl acetate content reduces polyethylene crystallinity and shifts the resin toward elastomeric behavior. Compared with an 18 wt% VA ethylene-vinyl acetate copolymer, the 45033.EH2 grade exhibits lower melting point, lower tensile modulus, higher elongation at break, and higher surface polarity. In practice, the higher vinyl acetate concentration improves wetting of polar substrates such as aluminum, polyester film, and glass. In co-rotating twin-screw compounding with 40:1 L/D machines, the 33 wt% VA grade shows higher filler acceptance with calcium carbonate and talc at loadings of 20–50 wt%, but the low melt index requires barrel temperature settings of 140–190°C to prevent pressure spikes at the die. The melt temperature must be confirmed by an immersion probe at the die exit because frictional heating can exceed setpoint by 10–20°C at screw speeds of 300 rpm.

Vinyl acetate content is frequently measured by FTIR to ASTM D5594-18 or by NMR. The 33 wt% value corresponds to approximately 10.5 mol% vinyl acetate. Lower-VA grades have higher crystalline melting temperatures and greater stiffness; a 28 wt% VA grade with a higher melt index disperses more rapidly but may develop less green strength in hot-melt adhesive coatings. Selection of EVA 45033.EH2 is therefore appropriate when final peel strength and low-temperature flexibility are more critical than melt flow.

Hot-melt adhesive production on continuous twin-screw lines uses EVA 45033.EH2 as the polymer backbone. Formulation ranges of 30–40 parts EVA, 35–50 parts tackifying resin, and 10–25 parts paraffin or Fischer-Tropsch wax are typical. Resin, wax, and polymer are fed in the first barrel, but the polymer is often added downstream to avoid overheating in the melt-kneading zone. Screw speed is limited to 250–350 rpm on a 40:1 L/D co-rotating machine to limit torque. Adhesive viscosity is measured at 180°C by ASTM D3236-88 with a Brookfield Thermosel. Peel adhesion to aluminum and low-density polyethylene is evaluated by ASTM D1876-08 using a 180° peel test at 300 mm/min. Ring-and-ball softening point is determined by ASTM E28-18. The high VA content supports compatibility with rosin ester tackifiers; phase separation after 24 h at 120°C is reduced relative to lower-VA grades when formulated with rosin ester and microcrystalline wax.

In wax blending, addition of 5–30 wt% EVA 45033.EH2 to paraffin wax modifies crystallite structure. The blend is prepared in a jacketed vessel at 160–180°C with low-shear agitation. Congealing point is determined by ASTM D938-18, and drop melting point is determined by ASTM D127-19. The copolymer increases viscosity and reduces wax brittleness; adhesion to fiberboard is tested by peel or tensile adhesion after coating. Published data for this exact grade in wax systems is limited, so pilot-scale blending is required to determine wax compatibility limits.

Thermal degradation occurs through vinyl acetate cleavage above 220°C in high-shear melt processing

EVA 45033.EH2 is not thermally stable above 220°C. At extended melt residence exceeding 15 min at 230°C, the acetate side groups undergo elimination, releasing acetic acid. The acid can corrode downstream metal surfaces and produce odor and bubble formation in extrudate. For hot-melt and compounding operations, melt temperature should be controlled at 180–200°C. Vented twin-screw extruders should be used with vacuum ports to strip acetic acid and moisture. Pre-drying is recommended at 60°C for 2 h when pellets have been stored at relative humidity above 60% or in cold warehouses; although EVA does not hydrolyze readily, surface condensation causes splay in extrudate. The dryer must be a desiccant type with a dew point below -20°C. Avoid blending with amine-based stabilizers that can accelerate deacetylation; phenolic/phosphite stabilizer packages at 0.1–0.3 wt% addition are preferred.

Single-screw extruders with 24:1 L/D may be used for adhesive coating, but melt temperature should be measured at the adapter. Because the melt index is 0.45 g/10 min, screw back pressure can reach 150–250 bar in a 90 mm extruder at 80 rpm when processing unfilled resin. Screw designs with shallow compression sections and Maddock mixing elements improve melt homogeneity without excessive shear. At shutdown, the machine should be purged with a lower-VA or polyolefin purge compound until the melt temperature falls below 150°C.

For hot-melt adhesives used in packaging, the final formulation is characterized by Brookfield viscosity ASTM D3236-88 at 149°C and 177°C, ring-and-ball softening point ASTM E28-18, and low-temperature flexibility by bending at -20°C. The 33 wt% vinyl acetate content provides adhesion to clay-coated paperboard and corrugated board. Open time and set time depend on wax selection and application temperature. Typical application temperature is 160–180°C using slot-die or roll coaters. Equipment must have temperature controllers with ±2°C accuracy; higher temperatures accelerate deacetylation.

When halogen-free flame-retardant cable jackets require high filler dispersion

Compounding for halogen-free flame-retardant cable jackets uses 60–65 wt% mineral filler, typically aluminum trihydroxide or magnesium hydroxide, in EVA 45033.EH2. The high vinyl acetate content improves filler wetting, but the low melt index of the resin increases mixing torque. A co-rotating twin-screw extruder with 40:1 L/D and side-fed filler at barrel 6 of 12 is used to avoid feeding limitations in the main hopper. Barrel temperature profile is 120–170°C from feed to die, with screw speed 200–320 rpm. The compound melt temperature at the die is held below 200°C. Tensile properties are measured by ASTM D638-14, elongation at break after thermal aging by ASTM D638-14 and IEC 60811-501, and limiting oxygen index by ASTM D2863-19. The final compound typically contains 1–3 wt% processing aid and 0.5–2 wt% silicone masterbatch to lower extruder torque; without these additives, die pressure variation can exceed 5% on long runs.

Batch-to-batch variation in filler moisture content influences adhesion and surface finish. Magnesium hydroxide releases water above 300°C; predrying at 80°C for 4 h in a dehumidifying hopper is required. The EVA phase provides char formation and low acid gas emission; hydrogen chloride generation is not present because no chlorinated polymers are used in the formulation.

Pellet storage should be in sealed containers at 5–40°C. Cold pellet temperature below 15°C can cause condensation when introduced to warm plant air. If pellets are conveyed by vacuum systems, transport air should be dried to a dew point below -20°C to avoid surface moisture. Static accumulation on pellets can be managed by grounding all conveying lines; the resin has higher surface resistivity than carbon-black-filled conductive compounds. Incoming melt index should be verified by ASTM D1238-20, density by ASTM D1505-18, and vinyl acetate content by FTIR calibrated with known standards. Control limits for lot-to-lot melt index variation are typically ±0.05 g/10 min, but specific supply agreements govern.

Rheological comparison with higher-melt-index EVA copolymers in molding and extrusion

Compared with an EVA copolymer of similar vinyl acetate content but melt index of 25 g/10 min, EVA 45033.EH2 develops higher melt strength and higher extruder head pressure at equal throughput. In spiral-flow testing by ASTM D3123-09, the low-melt-index grade fills a shorter flow length at a given injection pressure and melt temperature. It is not suitable for thin-wall injection molding with wall thickness below 1.5 mm unless melt temperature is increased to 210°C and injection speed is raised; even then, shear heating may approach the degradation boundary. The resin is better matched to profile extrusion, calendering, and compression molding where lower flow is acceptable.

Compared with LDPE, EVA 45033.EH2 exhibits lower melting point, lower flexural modulus, and better adhesion to polar substrates. Tensile strength measured by ASTM D638-14 is lower than LDPE; therefore, load-bearing structural applications require blending with high-density polyethylene. Compared with lower-VA EVA grades, the 45033.EH2 shows lower Shore hardness and improved low-temperature impact resistance, but reduced flexural stiffness.

In blown film, EVA 45033.EH2 is usually blended with LDPE or LLDPE at 10–30% to improve impact and clarity. The melt index of 0.45 g/10 min contributes to high back pressure in a 45 mm single-screw extruder; die gaps of 1.5–2.5 mm are typical. The high VA content increases film surface energy, improving printability without corona treatment beyond 38 mN/m. Surface energy measurement is by ASTM D2578-17. Higher VA also reduces film modulus; tensile properties are determined by ASTM D882-18 for films.

For crosslinked foam production, formulation containing 100 phr EVA 45033.EH2, 0.5–1.5 phr dicumyl peroxide, 2–5 phr azodicarbonamide, and 1–3 phr zinc oxide is mixed on a two-roll mill at 100–120°C. The melt index of 0.45 g/10 min provides green strength in sheet form before crosslinking. Cure behavior is measured by moving-die rheometer per ASTM D5289-19; the rheometer curve is used to adjust peroxide level to match press cycle. The 33 wt% vinyl acetate content lowers Shore A hardness of the foam and increases resilience compared with 18 wt% VA EVA foam. Dimensional stability after demolding requires cooling under pressure to below 80°C. Published data for this specific foaming configuration is limited; pilot trials are required to set mixing and cure parameters.

Asphalt modification with EVA 45033.EH2 is carried out in high-shear rotor-stator mixers at 170–190°C for 2–4 h. Addition levels of 3–7 wt% are typical. The EVA phase increases softening point, penetration resistance, and elastic recovery. Softening point is measured by ASTM D36-14, penetration by ASTM D5-20, and elastic recovery by ASTM D6084-18. The 33 wt% vinyl acetate content improves low-temperature cracking resistance relative to lower-VA EVA modifiers, but high-temperature storage stability must be confirmed at 160°C for 48 h because phase separation may occur if the asphalt has high asphaltene content. Published data for this specific configuration is limited; tank blending trials are required to set optimum addition level and shear time.

Regulatory assessments are application-specific. EVA copolymers may be subject to EU 10/2011 when used in food-contact articles, but finished-article migration testing is required. The resin is not a medical-grade product. REACH registration obligations apply to imported monomer and polymer substances; current EU REACH, RoHS 2011/65/EU, and safety data sheet documentation should be consulted before use in regulated end markets. Deacetylation products arising during thermal processing may require local exhaust ventilation. Any food-contact compliance under 21 CFR 177.1350 is conditional on vinyl acetate content, extractives limits, and finished-article conditions of use; it should not be assumed without full compliance testing.