EVATHENE UE3302 Ethylene Vinyl Acetate Copolymer

EVATHENE UE3302 is a pelletised ethylene-vinyl acetate copolymer supplied by USI Corporation. The grade is specified with a nominal vinyl acetate comonomer content of 33 wt%, a melt index of 2.0 g/10 min measured at 190 °C under 2.16 kg load by ISO 1133-1:2022, and a density of approximately 0.95 g/cm³ by ISO 1183-1:2019. The material is used in hot melt adhesives, crosslinked and uncrosslinked foam, footwear compounding, and as a polar modifier in polyolefin and PVC systems. Relative to lower vinyl acetate EVA grades, the 33 wt% acetate content suppresses crystallinity, lowers the melting point, increases surface polarity, and shifts mechanical response from stiff thermoplastic to flexible elastomer.

What structural consequence follows from 33 wt% vinyl acetate?

Because the vinyl acetate side groups disrupt ethylene chain packing, semicrystalline order is reduced. Differential scanning calorimetry at 10 °C/min in accordance with ASTM D3418-21 places the main melting endotherm for this comonomer level between 60 °C and 75 °C, whereas an 18 wt% vinyl acetate grade typically melts between 85 °C and 90 °C. Hardness for the 33 wt% class commonly falls between 70 Shore A and 80 Shore A when measured by ASTM D2240-15, and tensile elongation at break exceeds 600% under ASTM D638-14 at 500 mm/min. The acetate side groups increase cohesive energy density and promote wetting of aluminium, polyester, and polyurethane surfaces, but they also make the chain more sensitive to thermal deacetylation. Above 230 °C, acetic acid elimination increases, producing gel specks, discoloration, and equipment corrosion in continuous extrusion.

In a 25:1 to 30:1 L/D single-screw extruder, UE3302 is processed with a temperature profile from 160 °C in the feed zone to 210 °C at the die. Melt temperature should remain below 230 °C; on high-shear twin-screw lines, kneading blocks can raise local melt temperature 20–40 °C above the barrel set point. This thermal excursion is a common cause of batch-to-batch viscosity drift because deacetylation generates free acetic acid that catalyses further degradation. Drying is not required for pellets stored in sealed packaging at 25 °C and 50% relative humidity, but exposure to ambient air above 60% relative humidity requires desiccant drying at 70–80 °C for 4–6 h. Moisture-induced splay in EVA is less severe than in polyamide or PET, but surface condensation can still produce bubbles and streaks in extruded sheet.

Rheological characterisation is typically performed by parallel-plate oscillation at 180 °C under 1% strain and 100 rad/s. EVA grades with melt index 2.0 g/10 min display shear-thinning behaviour, and the storage modulus at 1 rad/s is lower than that of an 18 wt% vinyl acetate grade at the same melt index, which increases melt relaxation and reduces die swell. For hot melt adhesive production, this translates into reduced stringing at high application speeds, although published UE3302-specific rheological curves are limited.

When UE3302 is screened against EVA grades with lower or higher vinyl acetate content

Product selection is based on the balance between adhesion, low-temperature flexibility, heat resistance, and melt handling. The following values are class-typical ranges derived from EVA copolymer literature and compounding trials; they are not a substitute for a UE3302 certificate of analysis or lot-specific test data.

Relative to an 18 wt% vinyl acetate grade of equivalent melt index, UE3302 shows lower flexural modulus measured by ISO 178:2019, higher probe tack, and stronger adhesion to aluminium and polyester in hot melt bonding. Peel strength measured by ASTM D1876-08 typically increases when the lower-VA grade is replaced by UE3302, but published UE3302-specific values are limited. Against a 40 wt% vinyl acetate grade, UE3302 retains greater cohesive strength and is less prone to pellet blocking during warehouse storage because the surface tack is lower. The thermal degradation tendency lies between the two reference points, making melt temperature control more critical than in low-VA EVA but less critical than in 40 wt% high-VA EVA.

Compared with ethylene-methyl acrylate or ethylene-ethyl acrylate copolymers of equivalent comonomer content, UE3302 provides higher surface polarity and better adhesion to aluminium and polyester, but lower continuous-use temperature. The vinyl acetate unit undergoes acetic acid elimination at 230 °C; acrylate copolymers do not release an equivalent acidic by-product, giving them better thermal stability but less efficient hot tack on polar surfaces. Against metallocene polyethylene plastomers with density below 0.900 g/cm³, UE3302 may offer easier bonding and lower modulus but exhibits lower tensile toughness measured by ASTM D638-14 and poorer UV stability.

In hot melt adhesive production, UE3302 is charged to a jacketed sigma-blade mixer at 160–180 °C with tackifier and wax. Viscosity is measured by ASTM D3236-15 using a Brookfield thermosel at 180 °C; a starting formulation containing 30–35 wt% UE3302, 40–45 wt% rosin ester tackifier, and 20–25 wt% Fischer-Tropsch wax typically falls between 800 mPa·s and 2000 mPa·s. The 33 wt% acetate content increases compatibility with rosin esters and improves adhesion to polar packaging films, but it narrows the compatibility window for paraffinic waxes. Paraffinic wax levels above 10 phr can exude and cause bond failure under cold flex; open time and set time are controlled primarily by wax carbon number distribution and tackifier softening point. Supplier-specific design-space data for UE3302 hot melt formulations are limited.

Evaluating peroxide cure and blowing agent decomposition during foam expansion

In crosslinked EVA foam, UE3302 is compounded on a two-roll mill at 90–100 °C to incorporate dicumyl peroxide, activated azodicarbonamide, and fillers without scorch. Dicumyl peroxide is added at 0.7–1.2 phr, while activated azodicarbonamide is used at 2–5 phr depending on density target. The blowing agent decomposition is adjusted with zinc oxide or zinc stearate into the 160–180 °C cure range, and compression press platens are held at 150–170 °C to synchronise crosslinking with gas evolution. If the melt viscosity rises too slowly, cell coalescence produces an irregular open-cell structure; if the viscosity rise is too rapid, the foam cannot expand to full thickness. A peroxide loading below 0.5 phr is associated with low crosslink density and cell collapse, while loadings above 1.5 phr increase gel content, surface embrittlement, and shrinkage after demoulding. The window is narrower than for low-VA EVA because the acetate groups already lower crystallinity and raise melt tack. On a production scale, the main failure mode is batch-to-batch variation in two-roll mill temperature, which causes uneven peroxide dispersion and hot spots that initiate premature crosslinking.

Injection moulding of UE3302 is run at melt temperatures between 170 °C and 200 °C, with mould temperatures between 20 °C and 40 °C. The material does not require the same clamping force as rigid polyolefins of equivalent melt index because the hydraulic pressure needed to fill the cavity is lower; however, gate freeze-off is slower than semicrystalline polyethylene, and hot-runner systems should avoid stagnant zones above 230 °C. Sprue and runner systems with sharp turns can generate local shear heating that produces acetic acid odour and brown specks. Production lines equipped with hydraulic injection units with clamp force below 100 tonnes can accommodate a wide range of UE3302 parts, but rapid ejection may cause surface defects if the part has deep undercuts.

Outdoor weathering is not a primary design space for UE3302 because neat EVA undergoes photolytic deacetylation and surface cracking. Where external applications require resistance, 0.2–0.5 wt% of a high-molecular-weight hindered phenolic antioxidant and 0.2–0.5 wt% of a hindered amine light stabiliser are standard. The stabiliser package should be added before the melt exceeds 180 °C to limit oxidative chain scission during compounding. Carbon black at 2–3 wt% provides UV shielding in foam and film, but it complicates colour matching and raises dielectric loss.

Limits on filler loading and paraffinic plasticiser compatibility

Filled compounds based on UE3302 can accept calcium carbonate and talc, but the higher vinyl acetate content increases surface polarity and can promote filler agglomeration. In a 40:1 L/D co-rotating twin-screw extruder with side feeding, total filler addition is typically held below 30 wt% to avoid a discontinuous melt phase and pressure oscillations exceeding 20% of the set point. At filler loadings above this value, the elongational viscosity drops and the melt may tear at the die lip during strand pelletising. Paraffinic or naphthenic plasticisers reduce hardness but migrate to the surface at levels above 10 phr; accelerated storage at 40 °C for 48 h can reveal surface haze and tack. Aromatic plasticisers are generally avoided because they can accelerate deacetylation and generate odour. UE3302 should not be dry-blended with amine-based additives that may initiate premature crosslinking through reaction with residual acetoxy species; such systems require the amine additive to be introduced after the EVA has been fully melted and sufficiently diluted.

Converters requiring food-contact or medical-grade status should obtain a grade-specific compliance letter from USI Corporation. EVA copolymers of this comonomer level are commonly assessed under FDA 21 CFR 177.1350 and EU Regulation (EU) No 10/2011, including the overall migration limit of 10 mg/dm²; final compliance depends on the complete formulation and converting conditions. REACH registration documentation and RoHS screening for heavy metals must also be verified at lot level. No grade-specific statement should be inferred from generic class data.