EVATHENE UE33002 EVA resina de copolímero, 33% VA, espuma e calçado grau

EVATHENE UE33002 is an ethylene-vinyl acetate copolymer resin with a nominal vinyl acetate content of 33% by weight, positioned as a foam and footwear grade for chemically blown, peroxide-cured midsole, sheet, and moulded sole compounds. The grade belongs to the high-VA segment of EVA copolymer resins, where vinyl acetate comonomer reduces polyethylene crystallinity and shifts the material from semi-rigid film and extrusion behaviour toward flexible, low-hardness elastomeric behaviour. The resin is supplied in pellet form and is intended for compounding with azodicarbonamide or endothermic blowing agents, dicumyl peroxide or other peroxides, fillers, and processing aids. The exact melt flow rate and additive package for UE33002 should be taken from the supplier certificate of analysis or product data sheet, because foam grades are frequently controlled within narrow lot-to-lot ranges to maintain uniform cell structure. The nominal 33% VA content itself distinguishes UE33002 from lower-VA EVA grades used in hot-melt adhesives, films, and extrusion coating, where vinyl acetate content is commonly 12% to 28%. Higher vinyl acetate content improves low-temperature flexibility and filler acceptance, but increases polarity, tack, and water absorption. These characteristics define the processing window and downstream formulation constraints.

Thermal and Rheological Characterization Through Differential Scanning Calorimetry and Melt Flow Testing

Thermal analysis under ASTM D3418 for 33% VA EVA resins typically shows a broad melting endotherm between 60 °C and 85 °C, with peak location dependent on cooling rate and thermal history. The crystalline melting enthalpy is lower than that of 18% VA grades; class-typical values reported for high-VA EVA are in the range of 20 J/g to 35 J/g, while 18% VA grades may exceed 60 J/g. Melt flow rate is usually tested under ISO 1133-1:2022 at 190 °C/2.16 kg, and the result must be selected for the intended foam expansion ratio. Density is determined by ASTM D792; commercial 33% VA EVA resins often fall between 0.945 g/cm³ and 0.965 g/cm³. These class-typical values should not replace the UE33002 product data sheet because small shifts in vinyl acetate content and molecular weight alter melt viscosity and foaming behaviour. The resin’s low crystallinity also reduces the onset temperature for deformation under load and lowers Shore hardness at equivalent foam density compared with high-density polyethylene or lower-VA EVA.

For compression moulding of EVA foam sheet, the compound is first mixed in an internal Banbury-type mixer or on a two-roll mill. Mixing temperature is normally held between 90 °C and 110 °C to disperse zinc oxide, stearic acid, blowing agent, and peroxide without decomposing the peroxide or blowing agent. The azodicarbonamide blowing agent used in many footwear compounds has a decomposition peak near 204–215 °C in air, but exothermic decomposition can begin earlier at hot spots above 130 °C. The mixed compound is calendered or extruded into preforms, then placed into multi-opening hydraulic presses. Press temperatures of 160 °C to 175 °C are common for cure and blowing. During the press cycle, dicumyl peroxide crosslinking and azodicarbonamide gas generation overlap; the crosslinking reaction raises melt strength while gas expands to form the closed-cell structure. If cure is too fast relative to gas generation, expanding gas is trapped in over-crosslinked cells and tear strength decreases. If cure is too slow, cell walls may rupture under internal gas pressure, producing connected cells and internal splits. Production-scale presses with 500–1 500 t clamp force and multi-zone oil heating are used; part thickness determines cure time, with typical midsoles requiring 10–15 min for 10–15 mm thick sections. Gel content after cure is commonly checked by ASTM D2765 to ensure crosslink density; footwear foam specifications often require gel fraction in the range of 65–80% depending on hardness and rebound targets. Cured EVA foam midsoles with density 0.15–0.25 g/cm³ commonly exhibit tensile strength 1.5–2.5 MPa and elongation 200–350% under ASTM D412 or ASTM D3574; rebound resilience measured by ASTM D2632 is often 40–60% for standard midsoles.

When 33% VA EVATHENE UE33002 Replaces 18% VA EVA in a Footwear Midsole Compound

When EVATHENE UE33002 is used as the base polymer in a footwear midsole compound, the 33% VA level lowers Shore A/D hardness and increases elongation relative to 18% VA or 28% VA EVA at equivalent foam density. The higher polarity of the acetate groups improves wetting of calcium carbonate, talc, and silica fillers, which can reduce cost and increase hardness; filler loadings above 20 phr in high-VA EVA may reduce tear strength and dynamic fatigue resistance. For athletic midsoles, Asker C hardness targets often fall between 45 and 60. A 33% VA grade reaches the same Asker C hardness at lower compound density or with less filler than a lower-VA grade, supporting lightweight designs. The trade-off is lower heat deflection and higher compression set if the peroxide cure is insufficient. Compared with 28% VA EVA, UE33002 shifts the continuous phase toward greater flexibility and lower melting point; compared with 18% VA EVA, it is softer and more tacky, which can increase sheet blocking after calendering if release agents are inadequate. Compared with olefin block copolymer or SEBS foam grades, EVATHENE UE33002 has higher filler acceptance and generally lower material cost, but higher compression set and lower elastic recovery. In running shoe midsoles requiring rebound above 60%, the compound may be blended with 10–30 phr polyolefin elastomer or EPDM to tune energy return.

Crosslinking Kinetics, Blowing Agent Decomposition, and Process Safety Envelope

The curing system must be matched to the thermal behaviour of the 33% VA resin. Dicumyl peroxide has a one-minute half-life temperature near 175 °C and a one-hour half-life temperature near 135 °C; this places the practical cure window for compression moulding between 160 °C and 175 °C. At mixing temperatures of 100–110 °C, peroxide decomposition rate is low enough for safe compounding, but local hot spots above 130 °C can initiate premature crosslinking. Azodicarbonamide decomposition generates approximately 220 mL/g of gas, mainly nitrogen, carbon monoxide, carbon dioxide, and ammonia; gas evolution rate depends on particle size, activator level, and the presence of zinc oxide or zinc stearate. In EVA foam formulations, zinc oxide at 1–3 phr and stearic acid at 0.5–1.0 phr are frequently used. Blowing agent dosage is typically 2.5–4.0 phr for sheet expansion ratios of 1.5–2.5 or higher. The 33% VA grade’s lower crystallinity improves gas solubility and cell expansion at lower melt temperatures, but higher VA polarity can increase moisture uptake during storage. If the resin is stored at relative humidity above 60%, pre-drying at 60–70 °C for 4–6 h is recommended before compounding to avoid surface defects and irregular cells caused by steam. Published data for this specific configuration is limited; these limits are derived from class-typical EVA foam processing practice and should be confirmed against the UE33002 supplier technical data sheet.

Injection moulding of footwear soles from EVATHENE UE33002 compounds is performed at barrel temperatures of 80 °C to 120 °C, with mould temperatures between 30 °C and 50 °C. The low melt temperature of 33% VA EVA reduces energy input relative to TPU or higher-density polyolefin elastomers, but the narrow thermal window between melt processing and peroxide or blowing-agent activation requires close control. Screw designs with L/D ratios of 24:1 to 32:1 are used for homogeneous melt distribution without excessive shear heating. If melt temperature exceeds 125 °C before the mould, azodicarbonamide decomposition may begin in the barrel, causing gas voids, screw slip, and part density variation. Back pressure and screw speed are set to keep melt temperature overshoot below 10 °C above setpoint. Production-scale twin-screw compounding of ADC-containing EVA has shown that batch-to-batch differences in melt flow rate of ±0.3 g/10 min can shift final foam density by 3–5% under otherwise fixed conditions, so incoming melt flow rate control is critical.

Which Test Methods Are Required for Quality Release of EVATHENE UE33002?

Quality release for the resin should include verification of nominal vinyl acetate content, melt flow rate, density, and moisture. The supplier certificate of analysis is the primary source for UE33002-specific values. Incoming inspection at the footwear manufacturer may add accelerated ageing, gel content after cure, and foam density checks. The table below lists common test methods used for EVA foam and footwear raw materials and cured compounds. Test method designations align with ASTM and ISO methods; local specifications may include additional customer-specific parameters. Published data for this specific configuration is limited; the receiving site should establish control limits from the certificate of analysis and incoming inspection rather than from generic tables.

Raw material declarations should include the supplier safety data sheet, REACH Annex XVII restricted substance status, and AFIRM RSL screening if the compound is destined for footwear. EVATHENE UE33002 should not be assumed to meet food-contact regulations; if a food-contact application is considered, the grade must be specifically confirmed under 21 CFR 177.1520 or equivalent. For footwear, the finished compound may be tested for specific aromatic amines from blowing agent residues or for formamide if blowing agent decomposition is incomplete. Ventilation and post-cure ageing are normally used to reduce residual gas; post-cure at 60–80 °C for 4–8 h is common for crosslinked EVA foam to stabilize dimensions and reduce odour. The grade is also not compatible with amine-based additives that may prematurely decompose peroxide or interfere with azodicarbonamide decomposition.